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Mao F, Zhang C, Ren J, Wang T, Wang G, Zhang F, Rich T, Vickers-Rich P, Meng J. Fossils document evolutionary changes of jaw joint to mammalian middle ear. Nature 2024; 628:576-581. [PMID: 38570677 DOI: 10.1038/s41586-024-07235-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 02/26/2024] [Indexed: 04/05/2024]
Abstract
The dual jaw joint of Morganucodon1,2 consists of the dentary-squamosal joint laterally and the articular-quadrate one medially. The articular-quadrate joint and its associated post-dentary bones constitute the precursor of the mammalian middle ear. Fossils documenting the transition from such a precursor to the mammalian middle ear are poor, resulting in inconsistent interpretations of this hallmark apparatus in the earliest stage of mammaliaform evolution1-5. Here we report mandibular middle ears from two Jurassic mammaliaforms: a new morganucodontan-like species and a pseudotribosphenic shuotheriid species6. The morganucodontan-like species shows many previously unknown post-dentary bone morphologies1,2 and exhibits features that suggest a loss of load-bearing function in its articular-quadrate joint. The middle ear of the shuotheriid approaches the mammalian condition in that it has features that are suitable for an exclusively auditory function, although the post-dentary bones are still attached to the dentary. With size reduction of the jaw-joint bones, the quadrate shifts medially at different degrees in relation to the articular in the two mammaliaforms. These changes provide evidence of a gradual loss of load-bearing function in the articular-quadrate jaw joint-a prerequisite for the detachment of the post-dentary bones from the dentary7-12 and the eventual breakdown of the Meckel's cartilage13-15 during the evolution of mammaliaforms.
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Affiliation(s)
- Fangyuan Mao
- Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.
- Division of Paleontology, American Museum of Natural History, New York, NY, USA.
| | - Chi Zhang
- Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
| | - Jicheng Ren
- Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
| | - Tao Wang
- Bureau of Land and Resources of Lufeng County, Lufeng, China
| | - Guofu Wang
- Fossil Research Center of Chuxiong Prefecture, Chuxiong, China
| | - Fakui Zhang
- Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
| | - Thomas Rich
- Museums Victoria, Melbourne, Victoria, Australia
- School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia
| | - Patricia Vickers-Rich
- Museums Victoria, Melbourne, Victoria, Australia
- School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia
- School of Earth and Planetary Science, Curtin University, Perth, Western Australia, Australia
| | - Jin Meng
- Division of Paleontology, American Museum of Natural History, New York, NY, USA.
- Earth and Environmental Sciences, Graduate Center, City University of New York, New York, NY, USA.
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2
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Mao F, Li Z, Wang Z, Zhang C, Rich T, Vickers-Rich P, Meng J. Jurassic shuotheriids show earliest dental diversification of mammaliaforms. Nature 2024; 628:569-575. [PMID: 38570681 DOI: 10.1038/s41586-024-07258-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 02/29/2024] [Indexed: 04/05/2024]
Abstract
Shuotheriids are Jurassic mammaliaforms that possess pseudotribosphenic teeth in which a pseudotalonid is anterior to the trigonid in the lower molar, contrasting with the tribosphenic pattern of therian mammals (placentals, marsupials and kin) in which the talonid is posterior to the trigonid1-4. The origin of the pseudotribosphenic teeth remains unclear, obscuring our perception of shuotheriid affinities and the early evolution of mammaliaforms1,5-9. Here we report a new Jurassic shuotheriid represented by two skeletal specimens. Their complete pseudotribosphenic dentitions allow reidentification of dental structures using serial homology and the tooth occlusal relationship. Contrary to the conventional view1,2,6,10,11, our findings show that dental structures of shuotheriids can be homologized to those of docodontans and partly support homologous statements for some dental structures between docodontans and other mammaliaforms6,12. The phylogenetic analysis based on new evidence removes shuotheriids from the tribosphenic ausktribosphenids (including monotremes) and clusters them with docodontans to form a new clade, Docodontiformes, that is characterized by pseudotribosphenic features. In the phylogeny, docodontiforms and 'holotherians' (Kuehneotherium, monotremes and therians)13 evolve independently from a Morganucodon-like ancestor with triconodont molars by labio-lingual widening their posterior teeth for more efficient food processing. The pseudotribosphenic pattern passed a cusp semitriangulation stage9, whereas the tribosphenic pattern and its precursor went through a stage of cusp triangulation. The two different processes resulted in complex tooth structures and occlusal patterns that elucidate the earliest diversification of mammaliaforms.
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Affiliation(s)
- Fangyuan Mao
- Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.
- Division of Paleontology, American Museum of Natural History, New York, NY, USA.
| | - Zhiyu Li
- Inner Mongolia Museum of Natural History, Hohhot, China
| | - Zhili Wang
- Inner Mongolia Museum of Natural History, Hohhot, China
| | - Chi Zhang
- Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
| | - Thomas Rich
- Museums Victoria, Melbourne, Victoria, Australia
- School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia
| | - Patricia Vickers-Rich
- Museums Victoria, Melbourne, Victoria, Australia
- School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia
- School of Earth and Planetary Sciences, Curtin University, Perth, Western Australia, Australia
| | - Jin Meng
- Division of Paleontology, American Museum of Natural History, New York, NY, USA.
- Earth and Environmental Sciences, City University of New York, New York, NY, USA.
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3
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Brocklehurst N. The decline and fall of the mammalian stem. PeerJ 2024; 12:e17004. [PMID: 38436024 PMCID: PMC10906263 DOI: 10.7717/peerj.17004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 02/05/2024] [Indexed: 03/05/2024] Open
Abstract
The mammalian crown originated during the Mesozoic and subsequently radiated into the substantial array of forms now extant. However, for about 100 million years before the crown's origin, a diverse array of stem mammalian lineages dominated terrestrial ecosystems. Several of these stem lineages overlapped temporally and geographically with the crown mammals during the Mesozoic, but by the end of the Cretaceous crown mammals make up the overwhelming majority of the fossil record. The progress of this transition between ecosystems dominated by stem mammals and those dominated by crown mammals is not entirely clear, in part due to a distinct separation of analyses and datasets. Analyses of macroevolutionary patterns tend to focus on either the Mammaliaformes or the non-mammalian cynodonts, with little overlap in the datasets, preventing direct comparison of the diversification trends. Here I analyse species richness and biogeography of Synapsida as a whole during the Mesozoic, allowing comparison of the patterns in the mammalian crown and stem within a single framework. The analysis reveals the decline of the stem mammals occurred in two discrete phases. The first phase occurred between the Triassic and Middle Jurassic, during which the stem mammals were more restricted in their geographic range than the crown mammals, although within localities their species richness remained at levels seen previously. The second phase was a decline in species richness, which occurred during the Lower Cretaceous. The results show the decline of stem mammals, including tritylodontids and several mammaliaform groups, was not tied to a specific event, nor a gradual decline, but was instead a multiphase transition.
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Affiliation(s)
- Neil Brocklehurst
- Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom
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4
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Chimento NR, Agnolín FL, García-Marsà J, Manabe M, Tsuihiji T, Novas FE. A large therian mammal from the Late Cretaceous of South America. Sci Rep 2024; 14:2854. [PMID: 38310138 PMCID: PMC10838296 DOI: 10.1038/s41598-024-53156-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 01/29/2024] [Indexed: 02/05/2024] Open
Abstract
Theria represent an extant clade that comprises placental and marsupial mammals. Here we report on the discovery of a new Late Cretaceous mammal from southern Patagonia, Patagomaia chainko gen. et sp. nov., represented by hindlimb and pelvic elements with unambiguous therian features. We estimate Patagomaia chainko attained a body mass of 14 kg, which is considerably greater than the 5 kg maximum body mass of coeval Laurasian therians. This new discovery demonstrates that Gondwanan therian mammals acquired large body size by the Late Cretaceous, preceding their Laurasian relatives, which remained small-bodied until the beginning of the Cenozoic. Patagomaia supports the view that the Southern Hemisphere was a cradle for the evolution of modern mammalian clades, alongside non-therian extinct groups such as meridiolestidans, gondwanatherians and monotremes.
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Affiliation(s)
- Nicolás R Chimento
- Laboratorio de Anatomía Comparada y Evolución de los Vertebrados (LACEV), Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" (MACN-CONICET), Av. Ángel Gallardo 470, C1405DJR, Ciudad Autónoma de Buenos Aires, Argentina.
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
| | - Federico L Agnolín
- Laboratorio de Anatomía Comparada y Evolución de los Vertebrados (LACEV), Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" (MACN-CONICET), Av. Ángel Gallardo 470, C1405DJR, Ciudad Autónoma de Buenos Aires, Argentina
- Fundación de Historia Natural "Félix de Azara", Departamento de Ciencias Naturales y Antropología, CEBBAD - Universidad Maimónides, Hidalgo 767, C1405BDB, Buenos Aires, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Jordi García-Marsà
- Laboratorio de Anatomía Comparada y Evolución de los Vertebrados (LACEV), Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" (MACN-CONICET), Av. Ángel Gallardo 470, C1405DJR, Ciudad Autónoma de Buenos Aires, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Makoto Manabe
- National Museum of Nature and Science, 4‑1‑1 Amakubo, Tsukuba, 305‑0005, Japan
| | - Takanobu Tsuihiji
- Department of Earth and Planetary Science, The University of Tokyo, 7‑3‑1 Hongo, Bunkyo-ku, Tokyo, 305‑0005, Japan
| | - Fernando E Novas
- Laboratorio de Anatomía Comparada y Evolución de los Vertebrados (LACEV), Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" (MACN-CONICET), Av. Ángel Gallardo 470, C1405DJR, Ciudad Autónoma de Buenos Aires, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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5
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Formoso KK, Habib MB, Vélez-Juarbe J. The Role of Locomotory Ancestry on Secondarily Aquatic Transitions. Integr Comp Biol 2023; 63:1140-1153. [PMID: 37591628 DOI: 10.1093/icb/icad112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 07/11/2023] [Accepted: 07/12/2023] [Indexed: 08/19/2023] Open
Abstract
Land-to-sea evolutionary transitions are great transformations where terrestrial amniote clades returned to aquatic environments. These secondarily aquatic amniote clades include charismatic marine mammal and marine reptile groups, as well as countless semi-aquatic forms that modified their terrestrial locomotor anatomy to varying degrees to be suited for swimming via axial and/or appendicular propulsion. The terrestrial ancestors of secondarily aquatic groups would have started off swimming strikingly differently from one another given their evolutionary histories, as inferred by the way modern terrestrial amniotes swim. With such stark locomotor functional differences between reptiles and mammals, we ask if this impacted these transitions. Axial propulsion appears favored by aquatic descendants of terrestrially sprawling quadrupedal reptiles, with exceptions. Appendicular propulsion is more prevalent across the aquatic descendants of ancestrally parasagittal-postured mammals, particularly early transitioning forms. Ancestral terrestrial anatomical differences that precede secondarily aquatic invasions between mammals and reptiles, as well as the distribution of axial and appendicular swimming in secondarily aquatic clades, may indicate that ancestral terrestrial locomotor anatomy played a role, potentially in both constraint and facilitation, in certain aquatic locomotion styles. This perspective of the land-to-sea transition can lead to new avenues of functional, biomechanical, and developmental study of secondarily aquatic transitions.
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Affiliation(s)
- Kiersten K Formoso
- Department of Earth Sciences, University of Southern California, 3651 Trousedale Pkwy, Zumberge Hall, Los Angeles, CA 90089, USA
- Dinosaur Institute, Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, CA 90007-4057, USA
| | - Michael B Habib
- Dinosaur Institute, Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, CA 90007-4057, USA
- UCLA Cardiac Arrhythmia Center, Division of Cardiology, 100 Medical Plaza, Suite 660, Los Angeles, CA 90095, USA
| | - Jorge Vélez-Juarbe
- Department of Mammalogy, Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angelss, CA 90007-4057, USA
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6
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Norton LA, Abdala F, Benoit J. Craniodental anatomy in Permian-Jurassic Cynodontia and Mammaliaformes (Synapsida, Therapsida) as a gateway to defining mammalian soft tissue and behavioural traits. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220084. [PMID: 37183903 PMCID: PMC10184251 DOI: 10.1098/rstb.2022.0084] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023] Open
Abstract
Mammals are diagnosed by more than 30 osteological characters (e.g. squamosal-dentary jaw joint, three inner ear ossicles, etc.) that are readily preserved in the fossil record. However, it is the suite of physiological, soft tissue and behavioural characters (e.g. endothermy, hair, lactation, isocortex and parental care), the evolutionary origins of which have eluded scholars for decades, that most prominently distinguishes living mammals from other amniotes. Here, we review recent works that illustrate how evolutionary changes concentrated in the cranial and dental morphology of mammalian ancestors, the Permian-Jurassic Cynodontia and Mammaliaformes, can potentially be used to document the origin of some of the most crucial defining features of mammals. We discuss how these soft tissue and behavioural traits are highly integrated, and how their evolution is intermingled with that of craniodental traits, thus enabling the tracing of their previously out-of-reach phylogenetic history. Most of these osteological and dental proxies, such as the maxillary canal, bony labyrinth and dental replacement only recently became more easily accessible-thanks, in large part, to the widespread use of X-ray microtomography scanning in palaeontology-because they are linked to internal cranial characters. This article is part of the theme issue 'The mammalian skull: development, structure and function'.
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Affiliation(s)
- Luke A Norton
- Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
| | - Fernando Abdala
- Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
- Unidad Ejecutora Lillo, CONICET-Fundación Miguel Lillo, Miguel Lillo 251, Tucumán 4000, Argentina
| | - Julien Benoit
- Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
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7
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Dhouailly D. Evo Devo of the Vertebrates Integument. J Dev Biol 2023; 11:25. [PMID: 37367479 DOI: 10.3390/jdb11020025] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/19/2023] [Accepted: 05/21/2023] [Indexed: 06/28/2023] Open
Abstract
All living jawed vertebrates possess teeth or did so ancestrally. Integumental surface also includes the cornea. Conversely, no other anatomical feature differentiates the clades so readily as skin appendages do, multicellular glands in amphibians, hair follicle/gland complexes in mammals, feathers in birds, and the different types of scales. Tooth-like scales are characteristic of chondrichthyans, while mineralized dermal scales are characteristic of bony fishes. Corneous epidermal scales might have appeared twice, in squamates, and on feet in avian lineages, but posteriorly to feathers. In contrast to the other skin appendages, the origin of multicellular glands of amphibians has never been addressed. In the seventies, pioneering dermal-epidermal recombination between chick, mouse and lizard embryos showed that: (1) the clade type of the appendage is determined by the epidermis; (2) their morphogenesis requires two groups of dermal messages, first for primordia formation, second for appendage final architecture; (3) the early messages were conserved during amniotes evolution. Molecular biology studies that have identified the involved pathways, extending those data to teeth and dermal scales, suggest that the different vertebrate skin appendages evolved in parallel from a shared placode/dermal cells unit, present in a common toothed ancestor, c.a. 420 mya.
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Affiliation(s)
- Danielle Dhouailly
- Department of Biology and Chemistry, Institute for Advanced Biosciences, University Grenoble-Alpes, 38700 La Tronche, France
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8
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At the root of the mammalian mind: The sensory organs, brain and behavior of pre-mammalian synapsids. PROGRESS IN BRAIN RESEARCH 2023; 275:25-72. [PMID: 36841570 DOI: 10.1016/bs.pbr.2022.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
All modern mammals are descendants of the paraphyletic non-mammaliaform Synapsida, colloquially referred to as the "mammal-like reptiles." It has long been assumed that these mammalian ancestors were essentially reptile-like in their morphology, biology, and behavior, i.e., they had a small brain, displayed simple behavior, and their sensory organs were unrefined compared to those of modern mammals. Recent works have, however, revealed that neurological, sensory, and behavioral traits previously considered typically mammalian, such as whiskers, enhanced olfaction, nocturnality, parental care, and complex social interactions evolved before the origin of Mammaliaformes, among the early-diverging "mammal-like reptiles." In contrast, an enlarged brain did not evolve immediately after the origin of mammaliaforms. As such, in terms of paleoneurology, the last "mammal-like reptiles" were not significantly different from the earliest mammaliaforms. The abundant data and literature published in the last 10 years no longer supports the "three pulses" scenario of synapsid brain evolution proposed by Rowe and colleagues in 2011, but supports the new "outside-in" model of Rodrigues and colleagues proposed in 2018, instead. As Mesozoic reptiles were becoming the dominant taxa within terrestrial ecosystems, synapsids gradually adapted to smaller body sizes and nocturnality. This resulted in a sensory revolution in synapsids as olfaction, audition, and somatosensation compensated for the loss of visual cues. This altered sensory input is aligned with changes in the brain, the most significant of which was an increase in relative brain size.
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9
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A new Middle Jurassic cockroach (Blattaria: Blattulidae) from the Jiulongshan Formation of Daohugou in China. Biologia (Bratisl) 2023. [DOI: 10.1007/s11756-022-01300-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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10
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Calede JJM. The oldest semi-aquatic beaver in the world and a new hypothesis for the evolution of locomotion in Castoridae. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220926. [PMID: 36016911 DOI: 10.6084/m9.figshare.c.6154283] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 08/05/2022] [Indexed: 05/25/2023]
Abstract
The North American rodent fossil record includes hundreds of species representing both an incredible taxonomic diversity and great ecological disparity. Although it is during the Oligocene that taxonomic diversity first peaks, it is not until the Miocene, almost 10 Myr later, that many ecologies, particularly locomotory ecologies, are recorded. Here, I present a new Oligocene-aged species of beaver from Montana, Microtheriomys articulaquaticus sp. nov., which represents the oldest semi-aquatic rodent in North America and the oldest amphibious beaver in the world, pushing the advent of semi-aquatic ecology in beavers by 7 Myr. I also provide morphological data supporting a terrestrial ecology for the sister taxon to Castoridae. Together with existing data, these findings lead to a new hypothesis for the evolutionary ecology of castorids whereby swimming was exapted from burrowing during the Oligocene. This evolution of semi-aquatic locomotion may have taken place in North America instead of Eurasia. It started in small beavers with gigantism achieved only much later. Indeed, body size evolution in castoroids follows a directional drift. Beavers obey Cope's rule, a selection for larger size over time that appears associated with semi-aquatic ecology and may well explain their low modern diversity.
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Affiliation(s)
- Jonathan J M Calede
- Department of Evolution, Ecology, and Organismal Biology, The Ohio State University at Marion, 1459 Mount Vernon Avenue, Marion, OH 43302, USA
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11
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Calede JJM. The oldest semi-aquatic beaver in the world and a new hypothesis for the evolution of locomotion in Castoridae. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220926. [PMID: 36016911 PMCID: PMC9399697 DOI: 10.1098/rsos.220926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 08/05/2022] [Indexed: 05/10/2023]
Abstract
The North American rodent fossil record includes hundreds of species representing both an incredible taxonomic diversity and great ecological disparity. Although it is during the Oligocene that taxonomic diversity first peaks, it is not until the Miocene, almost 10 Myr later, that many ecologies, particularly locomotory ecologies, are recorded. Here, I present a new Oligocene-aged species of beaver from Montana, Microtheriomys articulaquaticus sp. nov., which represents the oldest semi-aquatic rodent in North America and the oldest amphibious beaver in the world, pushing the advent of semi-aquatic ecology in beavers by 7 Myr. I also provide morphological data supporting a terrestrial ecology for the sister taxon to Castoridae. Together with existing data, these findings lead to a new hypothesis for the evolutionary ecology of castorids whereby swimming was exapted from burrowing during the Oligocene. This evolution of semi-aquatic locomotion may have taken place in North America instead of Eurasia. It started in small beavers with gigantism achieved only much later. Indeed, body size evolution in castoroids follows a directional drift. Beavers obey Cope's rule, a selection for larger size over time that appears associated with semi-aquatic ecology and may well explain their low modern diversity.
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Affiliation(s)
- Jonathan J. M. Calede
- Department of Evolution, Ecology, and Organismal Biology, The Ohio State University at Marion, 1459 Mount Vernon Avenue, Marion, OH 43302, USA
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12
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Wright MA, Sears KE, Pierce SE. Comparison of Hindlimb Muscle Architecture Properties in Small-Bodied, Generalist Mammals Suggests Similarity in Soft Tissue Anatomy. J MAMM EVOL 2022. [DOI: 10.1007/s10914-022-09608-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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13
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Newham E, Gill PG, Corfe IJ. New tools suggest a middle Jurassic origin for mammalian endothermy: Advances in state-of-the-art techniques uncover new insights on the evolutionary patterns of mammalian endothermy through time: Advances in state-of-the-art techniques uncover new insights on the evolutionary patterns of mammalian endothermy through time. Bioessays 2022; 44:e2100060. [PMID: 35170781 DOI: 10.1002/bies.202100060] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 01/31/2022] [Accepted: 02/01/2022] [Indexed: 12/18/2022]
Abstract
We suggest that mammalian endothermy was established amongst Middle Jurassic crown mammals, through reviewing state-of-the-art fossil and living mammal studies. This is considerably later than the prevailing paradigm, and has important ramifications for the causes, pattern, and pace of physiological evolution amongst synapsids. Most hypotheses argue that selection for either enhanced aerobic activity, or thermoregulation was the primary driver for synapsid physiological evolution, based on a range of fossil characters that have been linked to endothermy. We argue that, rather than either alternative being the primary selective force for the entirety of endothermic evolution, these characters evolved quite independently through time, and across the mammal family tree, principally as a response to shifting environmental pressures and ecological opportunities. Our interpretations can be tested using closely linked proxies for both factors, derived from study of fossils of a range of Jurassic and Cretaceous mammaliaforms and early mammals.
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Affiliation(s)
- Elis Newham
- School of Engineering and Materials Science, Queen Mary University of London, London, UK.,Department of Palaeontology, Institute for Geosciences, University of Bonn, Bonn, Germany
| | - Pamela G Gill
- School of Earth Sciences, University of Bristol, Bristol, UK.,Earth Sciences Department, Natural History Museum, London, UK
| | - Ian J Corfe
- Jernvall Laboratory, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Geological Survey of Finland, Espoo, Finland
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14
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Kaas JH, Qi HX, Stepniewska I. Escaping the nocturnal bottleneck, and the evolution of the dorsal and ventral streams of visual processing in primates. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210293. [PMID: 34957843 PMCID: PMC8710890 DOI: 10.1098/rstb.2021.0293] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 09/21/2021] [Indexed: 12/12/2022] Open
Abstract
Early mammals were small and nocturnal. Their visual systems had regressed and they had poor vision. After the extinction of the dinosaurs 66 mya, some but not all escaped the 'nocturnal bottleneck' by recovering high-acuity vision. By contrast, early primates escaped the bottleneck within the age of dinosaurs by having large forward-facing eyes and acute vision while remaining nocturnal. We propose that these primates differed from other mammals by changing the balance between two sources of visual information to cortex. Thus, cortical processing became less dependent on a relay of information from the superior colliculus (SC) to temporal cortex and more dependent on information distributed from primary visual cortex (V1). In addition, the two major classes of visual information from the retina became highly segregated into magnocellular (M cell) projections from V1 to the primate-specific temporal visual area (MT), and parvocellular-dominated projections to the dorsolateral visual area (DL or V4). The greatly expanded P cell inputs from V1 informed the ventral stream of cortical processing involving temporal and frontal cortex. The M cell pathways from V1 and the SC informed the dorsal stream of cortical processing involving MT, surrounding temporal cortex, and parietal-frontal sensorimotor domains. This article is part of the theme issue 'Systems neuroscience through the lens of evolutionary theory'.
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Affiliation(s)
- Jon H. Kaas
- Department of Pshycology, Vanderbilt University, 301 Wilson Hall, 111 21st Ave. S., Nashville, TN 37240, USA
| | - Hui-Xin Qi
- Department of Pshycology, Vanderbilt University, 301 Wilson Hall, 111 21st Ave. S., Nashville, TN 37240, USA
| | - Iwona Stepniewska
- Department of Pshycology, Vanderbilt University, 301 Wilson Hall, 111 21st Ave. S., Nashville, TN 37240, USA
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15
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Brocklehurst RJ, Fahn-Lai P, Regnault S, Pierce SE. Musculoskeletal modeling of sprawling and parasagittal forelimbs provides insight into synapsid postural transition. iScience 2022; 25:103578. [PMID: 37609446 PMCID: PMC10441569 DOI: 10.1016/j.isci.2021.103578] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 10/14/2021] [Accepted: 12/03/2021] [Indexed: 11/30/2022] Open
Abstract
The sprawling-parasagittal postural shift was a major transition during synapsid evolution, underpinned by reorganization of the forelimb, and considered key to mammalian ecological diversity. Determining when and how this transition occurred in the fossil record is challenging owing to limited comparative data on extant species. Here, we built forelimb musculoskeletal models of three extant taxa that bracket sprawling-parasagittal postures-tegu lizard, echidna, and opossum-and tested the relationship between three-dimensional joint mobility, muscle action, and posture. Results demonstrate clear functional variation between postural grades, with the parasagittal opossum occupying a distinct region of pose space characterized by a highly retracted and depressed shoulder joint that emphasizes versatility and humeral elevation. Applying our data to the fossil record support trends of an increasingly retracted humerus and greater elevation muscle moment arms indicative of more parasagittal postures throughout synapsid evolution.
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Affiliation(s)
- Robert J. Brocklehurst
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 01239, USA
| | - Philip Fahn-Lai
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 01239, USA
- Concord Field Station and Department of Organismic and Evolutionary Biology, Harvard University, Bedford, MA01730, USA
| | - Sophie Regnault
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 01239, USA
- Institute of Biological, Environment & Rural Sciences, Aberystwyth University, Aberystwyth, CeredigionSY23 3DA, UK
| | - Stephanie E. Pierce
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 01239, USA
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16
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Knaus PL, van Heteren AH, Lungmus JK, Sander PM. High Blood Flow Into the Femur Indicates Elevated Aerobic Capacity in Synapsids Since the Synapsida-Sauropsida Split. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.751238] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Varanids are the only non-avian sauropsids that are known to approach the warm-blooded mammals in stamina. Furthermore, a much higher maximum metabolic rate (MMR) gives endotherms (including birds) higher stamina than crocodiles, turtles, and non-varanid lepidosaurs. This has led researchers to hypothesize that mammalian endothermy evolved as a second step after the acquisition of elevated MMR in non-mammalian therapsids from a plesiomorphic state of low metabolic rates. In recent amniotes, MMR correlates with the index of blood flow into the femur (Qi), which is calculated from femoral length and the cross-sectional area of the nutrient foramen. Thus, Qi may serve as an indicator of MMR range in extinct animals. Using the Qi proxy and phylogenetic eigenvector maps, here we show that elevated MMRs evolved near the base of Synapsida. Non-mammalian synapsids, including caseids, edaphosaurids, sphenacodontids, dicynodonts, gorgonopsids, and non-mammalian cynodonts, show Qi values in the range of recent endotherms and varanids, suggesting that raised MMRs either evolved in synapsids shortly after the Synapsida-Sauropsida split in the Mississippian or that the low MMR of lepidosaurs and turtles is apomorphic, as has been postulated for crocodiles.
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17
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Lungmus JK, Angielczyk KD. Phylogeny, function and ecology in the deep evolutionary history of the mammalian forelimb. Proc Biol Sci 2021; 288:20210494. [PMID: 33878918 PMCID: PMC8059613 DOI: 10.1098/rspb.2021.0494] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 03/29/2021] [Indexed: 11/12/2022] Open
Abstract
Mammals are the only living members of the larger clade Synapsida, which has a fossil record spanning 320 Ma. Despite the fact that much of the ecological diversity of mammals has been considered in the light of limb morphology, the ecological comparability of mammals to their fossil forerunners has not been critically assessed. Because of the wide use of limb morphology in testing ecomorphological hypothesis about extinct tetrapods, we sought: (i) to estimate when in synapsid history, modern mammals become analogues for predicting fossil ecologies; (ii) to document examples of ecomorphological convergence; and (iii) to compare the functional solutions of distinct synapsid radiations. We quantitatively compared the forelimb shapes of the multiple fossil synapsid radiations to a broad sample of extant Mammalia representing a variety of divergent locomotor ecologies. Our results indicate that each synapsid radiation explored different areas of morphospace and arrived at functional solutions that reflected their distinctive ancestral morphologies. This work counters the narrative of non-mammalian synapsid forelimb evolution as a linear progression towards more mammalian morphologies. Instead, a disparate array of early-evolving shapes subsequently contracted towards more mammal-like forms.
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Affiliation(s)
- Jacqueline K. Lungmus
- Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA
- Negaunee Integrative Research Center, Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, IL 60605-2496, USA
| | - Kenneth D. Angielczyk
- Negaunee Integrative Research Center, Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, IL 60605-2496, USA
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18
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Fish FE, Rybczynski N, Lauder GV, Duff CM. The Role of the Tail or Lack Thereof in the Evolution of Tetrapod Aquatic Propulsion. Integr Comp Biol 2021; 61:398-413. [PMID: 33881525 DOI: 10.1093/icb/icab021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Synopsis Secondary aquatic vertebrates exhibit a diversity of swimming modes that use paired limbs and/or the tail. Various secondarily aquatic tetrapod clades, including amphibians, reptiles, and mammals employ transverse undulations or oscillations of the tail for swimming. These movements have often been classified according to a kinematic gradient that was established for fishes, but may not be appropriate to describe the swimming motions of tetrapods. To understand the evolution of movements and design of the tail in aquatic tetrapods, we categorize the types of tails used for swimming and examine swimming kinematics and hydrodynamics. From a foundation of a narrow, elongate ancestral tail, the tails used for swimming by aquatic tetrapods are classified as tapered, keeled, paddle, and lunate. Tail undulations are associated with tapered, keeled, and paddle tails for a diversity of taxa. Propulsive undulatory waves move down the tail with increasing amplitude toward the tail tip, while moving posteriorly at a velocity faster than the anterior motion of the body indicating that the tail is used for thrust generation. Aquatic propulsion is associated with the transfer of momentum to the water from the swimming movements of the tail, particularly at the trailing edge. The addition of transverse extensions and flattening of the tail increases the mass of water accelerated posteriorly and affects vorticity shed into the wake for more aquatically adapted animals. DPIV (Digital Particle Image Velocimetry) reveals differences were exhibited in the vortex wake between the morphological and kinematic extremes of the alligator with a tapering undulating tail and the dolphin with oscillating wing-like flukes that generate thrust. In addition to exploring the relationship between shape of undulating tails and swimming performance across aquatic tetrapods, the role of tail reduction or loss of a tail in aquatic-tetrapod swimming was also explored. For aquatic tetrapods, reduction would have been due to factors including locomotor and defensive specializations and phylogenetic and physiological constraints. Possession of a thrust-generating tail for swimming, or lack thereof, guided various lineages of secondarily aquatic vertebrates into different evolutionary trajectories for effective aquatic propulsion (i.e., speed, efficiency, acceleration).
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Affiliation(s)
- Frank E Fish
- Department of Biology, West Chester University, West Chester, Pennsylvania 19383, USA
| | - Natalia Rybczynski
- Department of Palaeobiology, Canadian Museum of Nature, Ottawa, K1P 6P4, Ontario, Canada
| | - George V Lauder
- Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA
| | - Christina M Duff
- Department of Biology, West Chester University, West Chester, Pennsylvania 19383, USA
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19
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Jaw shape and mechanical advantage are indicative of diet in Mesozoic mammals. Commun Biol 2021; 4:242. [PMID: 33623117 PMCID: PMC7902851 DOI: 10.1038/s42003-021-01757-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 01/14/2021] [Indexed: 01/31/2023] Open
Abstract
Jaw morphology is closely linked to both diet and biomechanical performance, and jaws are one of the most common Mesozoic mammal fossil elements. Knowledge of the dietary and functional diversity of early mammals informs on the ecological structure of palaeocommunities throughout the longest era of mammalian evolution: the Mesozoic. Here, we analyse how jaw shape and mechanical advantage of the masseter (MAM) and temporalis (MAT) muscles relate to diet in 70 extant and 45 extinct mammals spanning the Late Triassic-Late Cretaceous. In extant mammals, jaw shape discriminates well between dietary groups: insectivores have long jaws, carnivores intermediate to short jaws, and herbivores have short jaws. Insectivores have low MAM and MAT, carnivores have low MAM and high MAT, and herbivores have high MAM and MAT. These traits are also informative of diet among Mesozoic mammals (based on previous independent determinations of diet) and set the basis for future ecomorphological studies.
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20
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Franchini LF. Genetic Mechanisms Underlying Cortical Evolution in Mammals. Front Cell Dev Biol 2021; 9:591017. [PMID: 33659245 PMCID: PMC7917222 DOI: 10.3389/fcell.2021.591017] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 01/08/2021] [Indexed: 12/13/2022] Open
Abstract
The remarkable sensory, motor, and cognitive abilities of mammals mainly depend on the neocortex. Thus, the emergence of the six-layered neocortex in reptilian ancestors of mammals constitutes a fundamental evolutionary landmark. The mammalian cortex is a columnar epithelium of densely packed cells organized in layers where neurons are generated mainly in the subventricular zone in successive waves throughout development. Newborn cells move away from their site of neurogenesis through radial or tangential migration to reach their specific destination closer to the pial surface of the same or different cortical area. Interestingly, the genetic programs underlying neocortical development diversified in different mammalian lineages. In this work, I will review several recent studies that characterized how distinct transcriptional programs relate to the development and functional organization of the neocortex across diverse mammalian lineages. In some primates such as the anthropoids, the neocortex became extremely large, especially in humans where it comprises around 80% of the brain. It has been hypothesized that the massive expansion of the cortical surface and elaboration of its connections in the human lineage, has enabled our unique cognitive capacities including abstract thinking, long-term planning, verbal language and elaborated tool making capabilities. I will also analyze the lineage-specific genetic changes that could have led to the modification of key neurodevelopmental events, including regulation of cell number, neuronal migration, and differentiation into specific phenotypes, in order to shed light on the evolutionary mechanisms underlying the diversity of mammalian brains including the human brain.
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Affiliation(s)
- Lucía Florencia Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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21
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Panciroli E, Benson RBJ, Fernandez V, Butler RJ, Fraser NC, Luo ZX, Walsh S. New species of mammaliaform and the cranium of Borealestes (Mammaliformes: Docodonta) from the Middle Jurassic of the British Isles. Zool J Linn Soc 2021. [DOI: 10.1093/zoolinnean/zlaa144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Abstract
Docodonta are one of the earliest diverging groups of mammaliaforms, and their morphology provides key information on the transition between non-mammalian cynodonts and Mammalia. We describe the partial skulls of two docodontans Borealestes serendipitus and Borealestes cuillinensis sp. nov. from the Kilmaluag Formation (Middle Jurassic: Bathonian), Isle of Skye, Scotland. We visualize their cranial anatomy using laboratory and synchrotron X-ray micro-CT. The skulls belong to two partial skeletons, currently comprising the most complete Mesozoic mammal fossils reported from the British Isles. The associated upper and lower dentitions show that the lower dentition of Borealestes is not diagnostic to species level. We establish, B. cuillinensis, based on upper molar characters, and re-identify upper molars previously assigned to ‘Borealestes’ mussettae as belonging to B. cuillinensis. ‘Borealestes’ mussettae, based on distinctive lower molars, is found to be morphologically and phylogenetically distinct from Borealestes, necessitating assignment to a new genus, Dobunnodon gen. nov. The skulls of Borealestes retain many plesiomorphic features seen in Morganucodon but absent in more crownward mammaliaforms. Our study highlights that generic and species taxonomy of docodontans are more reliable when based on both upper and lower teeth, while lower molar morphology may underrepresent the true diversity of Mesozoic mammaliaforms.
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Affiliation(s)
- Elsa Panciroli
- Natural Science Department, National Museums Scotland, Edinburgh, Scotland, UK
- School of Geosciences, Grant Institute, University of Edinburgh, Scotland, UK
- Department of Earth Sciences, University of Oxford, Oxford, England, UK
| | - Roger B J Benson
- Department of Earth Sciences, University of Oxford, Oxford, England, UK
| | - Vincent Fernandez
- European Synchrotron Radiation Facility (ESRF), Beamline, Grenoble, France
- Natural History Museum, London, UK
| | - Richard J Butler
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - Nicholas C Fraser
- Natural Science Department, National Museums Scotland, Edinburgh, Scotland, UK
- School of Geosciences, Grant Institute, University of Edinburgh, Scotland, UK
| | - Zhe-Xi Luo
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, Illinois, USA
| | - Stig Walsh
- Natural Science Department, National Museums Scotland, Edinburgh, Scotland, UK
- School of Geosciences, Grant Institute, University of Edinburgh, Scotland, UK
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22
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Kilbourne BM. Differing limb functions and their potential influence upon the diversification of the mustelid hindlimb skeleton. Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blaa207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Though form-function relationships of the mammalian locomotor system have been investigated for over a century, recent models of trait evolution have hitherto been seldom used to identify likely evolutionary processes underlying the locomotor system’s morphological diversity. Using mustelids, an ecologically diverse carnivoran lineage, I investigated whether variation in hindlimb skeletal morphology functionally coincides with climbing, digging, swimming and generalized locomotor habits by using 15 linear traits of the femur, tibia, fibula, calcaneum and metatarsal III across 44 species in a principal component analysis. I subsequently fit different models of Brownian motion and adaptive trait diversification individually to each trait. Climbing, digging and swimming mustelids occupy distinct regions of phenotypic space characterized by differences in bone robustness. Models of adaptive and neutral evolution are, respectively, the best fits for long bone lengths and muscle in-levers, suggesting that different kinds of traits may be associated with different evolutionary processes. However, simulations based upon models of best fit reveal low statistical power to rank the models. Though differences in mustelid hindlimb skeletal morphology appear to coincide with locomotor habits, further study, with sampling expanded beyond the Mustelidae, is necessary to better understand to what degree adaptive evolution shapes morphological diversity of the locomotor system.
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Affiliation(s)
- Brandon M Kilbourne
- Museum für Naturkunde Berlin, Leibniz Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany
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23
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Álvarez-Parra S, Delclòs X, Solórzano-Kraemer MM, Alcalá L, Peñalver E. Cretaceous amniote integuments recorded through a taphonomic process unique to resins. Sci Rep 2020; 10:19840. [PMID: 33199731 PMCID: PMC7669849 DOI: 10.1038/s41598-020-76830-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 11/03/2020] [Indexed: 11/10/2022] Open
Abstract
Fossil records of vertebrate integuments are relatively common in both rocks, as compressions, and amber, as inclusions. The integument remains, mainly the Mesozoic ones, are of great interest due to the panoply of palaeobiological information they can provide. We describe two Spanish Cretaceous amber pieces that are of taphonomic importance, one bearing avian dinosaur feather remains and the other, mammalian hair. The preserved feather remains originated from an avian dinosaur resting in contact with a stalactite-shaped resin emission for the time it took for the fresh resin to harden. The second piece shows three hair strands recorded on a surface of desiccation, with the characteristic scale pattern exceptionally well preserved and the strands aligned together, which can be considered the record of a tuft. These assemblages were recorded through a rare biostratinomic process we call "pull off vestiture" that is different from the typical resin entrapment and embedding of organisms and biological remains, and unique to resins. The peculiarity of this process is supported by actualistic observations using sticky traps in Madagascar. Lastly, we reinterpret some exceptional records from the literature in the light of that process, thus bringing new insight to the taphonomic and palaeoecological understanding of the circumstances of their origins.
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Affiliation(s)
- Sergio Álvarez-Parra
- Departament de Dinàmica de la Terra i de l'Oceà and Institut de Recerca de la Biodiversitat (IRBio), Facultat de Ciències de la Terra, Universitat de Barcelona, c/ Martí i Franquès S/N, 08028, Barcelona, Spain.
| | - Xavier Delclòs
- Departament de Dinàmica de la Terra i de l'Oceà and Institut de Recerca de la Biodiversitat (IRBio), Facultat de Ciències de la Terra, Universitat de Barcelona, c/ Martí i Franquès S/N, 08028, Barcelona, Spain
| | - Mónica M Solórzano-Kraemer
- Paläontologie und Historische Geologie, Senckenberg Forschungsinstitut und Naturmuseum, Senckenberganlage 25, 60325, Frankfurt am Main, Germany
| | - Luis Alcalá
- Fundación Conjunto Paleontológico de Teruel-Dinópolis/Museo Aragonés de Paleontología, Av. Sagunto s/n, 44002, Teruel, Spain
| | - Enrique Peñalver
- Instituto Geológico y Minero de España (Museo Geominero), c/ Cirilo Amorós 42, 46004, Valencia, Spain
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24
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Newham E, Gill PG, Brewer P, Benton MJ, Fernandez V, Gostling NJ, Haberthür D, Jernvall J, Kankaanpää T, Kallonen A, Navarro C, Pacureanu A, Richards K, Brown KR, Schneider P, Suhonen H, Tafforeau P, Williams KA, Zeller-Plumhoff B, Corfe IJ. Reptile-like physiology in Early Jurassic stem-mammals. Nat Commun 2020; 11:5121. [PMID: 33046697 PMCID: PMC7550344 DOI: 10.1038/s41467-020-18898-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 09/11/2020] [Indexed: 12/12/2022] Open
Abstract
Despite considerable advances in knowledge of the anatomy, ecology and evolution of early mammals, far less is known about their physiology. Evidence is contradictory concerning the timing and fossil groups in which mammalian endothermy arose. To determine the state of metabolic evolution in two of the earliest stem-mammals, the Early Jurassic Morganucodon and Kuehneotherium, we use separate proxies for basal and maximum metabolic rate. Here we report, using synchrotron X-ray tomographic imaging of incremental tooth cementum, that they had maximum lifespans considerably longer than comparably sized living mammals, but similar to those of reptiles, and so they likely had reptilian-level basal metabolic rates. Measurements of femoral nutrient foramina show Morganucodon had blood flow rates intermediate between living mammals and reptiles, suggesting maximum metabolic rates increased evolutionarily before basal metabolic rates. Stem mammals lacked the elevated endothermic metabolism of living mammals, highlighting the mosaic nature of mammalian physiological evolution.
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Affiliation(s)
- Elis Newham
- School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, UK. .,Bioengineering Science Research Group, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK.
| | - Pamela G Gill
- School of Earth Sciences, University of Bristol, Bristol, UK. .,Earth Sciences Department, The Natural History Museum, London, UK.
| | - Philippa Brewer
- Earth Sciences Department, The Natural History Museum, London, UK
| | | | - Vincent Fernandez
- Core Research Laboratories, The Natural History Museum, London, UK.,ESRF, The European Synchrotron, Grenoble, France
| | - Neil J Gostling
- School of Biological Sciences, University of Southampton, Southampton, UK
| | - David Haberthür
- Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.,Institute of Anatomy, University of Bern, Bern, Switzerland
| | - Jukka Jernvall
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Tuomas Kankaanpää
- Department of Agricultural Sciences, University of Helsinki, Helsinki, Finland
| | - Aki Kallonen
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - Charles Navarro
- School of Earth Sciences, University of Bristol, Bristol, UK
| | | | | | - Kate Robson Brown
- Department of Anthropology and Archaeology, University of Bristol, Bristol, UK
| | - Philipp Schneider
- Bioengineering Science Research Group, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
| | - Heikki Suhonen
- Department of Physics, University of Helsinki, Helsinki, Finland
| | | | - Katherine A Williams
- Bioengineering Science Research Group, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
| | - Berit Zeller-Plumhoff
- Institute for Materials Research, Division of Metallic Biomaterials, Helmholtz Zentrum Geesthacht, Geesthacht, Germany
| | - Ian J Corfe
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland. .,Geomaterials and Applied Mineralogy group, Geological Survey of Finland, Espoo, Finland.
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25
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Erwin DH. A conceptual framework of evolutionary novelty and innovation. Biol Rev Camb Philos Soc 2020; 96:1-15. [PMID: 32869437 DOI: 10.1111/brv.12643] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 07/31/2020] [Accepted: 08/12/2020] [Indexed: 12/20/2022]
Abstract
Since 1990 the recognition of deep homologies among metazoan developmental processes and the spread of more mechanistic approaches to developmental biology have led to a resurgence of interest in evolutionary novelty and innovation. Other evolutionary biologists have proposed central roles for behaviour and phenotypic plasticity in generating the conditions for the construction of novel morphologies, or invoked the accessibility of new regions of vast sequence spaces. These approaches contrast with more traditional emphasis on the exploitation of ecological opportunities as the primary source of novelty. This definitional cornucopia reflects differing stress placed on three attributes of novelties: their radical nature, the generation of new taxa, and ecological and evolutionary impact. Such different emphasis has led to conflating four distinct issues: the origin of novel attributes (genes, developmental processes, phenotypic characters), new functions, higher clades and the ecological impact of new structures and functions. Here I distinguish novelty (the origin of new characters, deep character transformations, or new combinations) from innovation, the ecological and evolutionary success of clades. Evidence from the fossil record of macroevolutionary lags between the origin of a novelty and its ecological success demonstrates that novelty may be decoupled from innovation, and only definitions of novelty based on radicality (rather than generativity or consequentiality) can be assessed without reference to the subsequent history of the clade to which a novelty belongs. These considerations suggest a conceptual framework for novelty and innovation, involving: (i) generation of the potential for novelty; (ii) the formation of novel attributes; (iii) refinement of novelties through adaptation; (iv) exploitation of novelties by a clade, which may coincide with a new round of ecological or environmental potentiation; followed by (v) the establishment of innovations through ecological processes. This framework recognizes that there is little empirical support for either the dominance of ecological opportunity, nor abrupt discontinuities (often caricatured as 'hopeful monsters'). This general framework may be extended to aspects of cultural and social innovation.
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Affiliation(s)
- Douglas H Erwin
- Department of Paleobiology, MRC-121 National Museum of Natural History, PO Box 37012, Washington, DC, 20013-7012, U.S.A.,Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM, 87501, U.S.A
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26
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Siomava N, Fuentes JSM, Diogo R. Deconstructing the long‐standing a priori assumption that serial homology generally involves ancestral similarity followed by anatomical divergence. J Morphol 2020; 281:1110-1132. [DOI: 10.1002/jmor.21236] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 06/18/2020] [Accepted: 07/07/2020] [Indexed: 12/26/2022]
Affiliation(s)
- Natalia Siomava
- Department of Anatomy Howard University College of Medicine Washington District of Columbia USA
| | | | - Rui Diogo
- Department of Anatomy Howard University College of Medicine Washington District of Columbia USA
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27
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Celik MA, Phillips MJ. Conflict Resolution for Mesozoic Mammals: Reconciling Phylogenetic Incongruence Among Anatomical Regions. Front Genet 2020; 11:0651. [PMID: 32774343 PMCID: PMC7381353 DOI: 10.3389/fgene.2020.00651] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Accepted: 05/28/2020] [Indexed: 11/13/2022] Open
Abstract
The evolutionary history of Mesozoic mammaliaformes is well studied. Although the backbone of their phylogeny is well resolved, the placement of ecologically specialized groups has remained uncertain. Functional and developmental covariation has long been identified as an important source of phylogenetic error, yet combining incongruent morphological characters altogether is currently a common practice when reconstructing phylogenetic relationships. Ignoring incongruence may inflate the confidence in reconstructing relationships, particularly for the placement of highly derived and ecologically specialized taxa, such as among australosphenidans (particularly, crown monotremes), haramiyidans, and multituberculates. The alternative placement of these highly derived clades can alter the taxonomic constituency and temporal origin of the mammalian crown group. Based on prior hypotheses and correlated homoplasy analyses, we identified cheek teeth and shoulder girdle character complexes as having a high potential to introduce phylogenetic error. We showed that incongruence among mandibulodental, cranial, and postcranial anatomical partitions for the placement of the australosphenidans, haramiyids, and multituberculates could largely be explained by apparently non-phylogenetic covariance from cheek teeth and shoulder girdle characters. Excluding these character complexes brought agreement between anatomical regions and improved the confidence in tree topology. These results emphasize the importance of considering and ameliorating major sources of bias in morphological data, and we anticipate that these will be valuable for confidently integrating morphological and molecular data in phylogenetic and dating analyses.
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Affiliation(s)
- Mélina A Celik
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, QLD, Australia
| | - Matthew J Phillips
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, QLD, Australia
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28
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Benevento GL, Benson RBJ, Friedman M. Patterns of mammalian jaw ecomorphological disparity during the Mesozoic/Cenozoic transition. Proc Biol Sci 2020; 286:20190347. [PMID: 31039714 PMCID: PMC6532522 DOI: 10.1098/rspb.2019.0347] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The radiation of mammals after the Cretaceous/Palaeogene (K/Pg) boundary was a major event in the evolution of terrestrial ecosystems. Multiple studies point to increases in maximum body size and body size disparity, but patterns of disparity for other traits are less clear owing to a focus on different indices and subclades. We conducted an inclusive comparison of jaw functional disparity from the Early Jurassic-latest Eocene, using six mechanically relevant mandibular ratios for 256 species representing all major groups. Jaw functional disparity across all mammals was low throughout much of the Mesozoic and remained low across the K/Pg boundary. Nevertheless, the K/Pg boundary was characterized by a pronounced pattern of turnover and replacement, entailing a substantial reduction of non-therian and stem-therian disparity, alongside a marked increase in that of therians. Total mammal disparity exceeded its Mesozoic maximum for the first time during the Eocene, when therian mammals began exploring previously unoccupied regions of function space. This delay in the rise of jaw functional disparity until the Eocene probably reflects the duration of evolutionary recovery after the K/Pg mass extinction event. This contrasts with the more rapid expansion of maximum body size, which occurred in the Palaeocene.
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Affiliation(s)
- Gemma Louise Benevento
- 1 Department of Earth Sciences, University of Oxford , Oxford OX1 3AN , UK.,2 School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston , Birmingham B15 2TT , UK
| | - Roger B J Benson
- 1 Department of Earth Sciences, University of Oxford , Oxford OX1 3AN , UK
| | - Matt Friedman
- 1 Department of Earth Sciences, University of Oxford , Oxford OX1 3AN , UK.,3 Museum of Paleontology and Department of Earth and Environmental Sciences, University of Michigan , 1105 N University Avenue, Ann Arbor, MI 48109 , USA
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Faure-Brac MG, Cubo J. Were the synapsids primitively endotherms? A palaeohistological approach using phylogenetic eigenvector maps. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190138. [PMID: 31928185 DOI: 10.1098/rstb.2019.0138] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The acquisition of mammalian endothermy is poorly constrained both phylogenetically and temporally. Here, we inferred the resting metabolic rates (RMRs) and the thermometabolic regimes (endothermy or ectothermy) of a sample of eight extinct synapsids using palaeohistology, phylogenetic eigenvector maps (PEMs), and a sample of 17 extant tetrapods of known RMR (quantified using respirometry). We inferred high RMR values and an endothermic metabolism for the anomodonts (Lystrosaurus sp., Oudenodon bainii) and low RMR values and an ectothermic metabolism for Clepsydrops collettii, Dimetrodon sp., Edaphosaurus boanerges, Mycterosaurus sp., Ophiacodon uniformis and Sphenacodon sp. A maximum-likelihood ancestral states reconstruction of RMRs performed using the values inferred for extinct synapsids, and the values measured using respirometry in extant tetrapods, shows that the nodes Anomodontia and Mammalia were primitively endotherms. Finally, we performed a parsimony optimization of the presence of endothermy using the results obtained in the present study and those obtained in previous studies that used PEMs. For this, we assigned to each extinct taxon a thermometabolic regime (ectothermy or endothermy) depending on whether the inferred values were significantly higher, lower or not significantly different from the RMR value separating ectotherms from endotherms (1.5 ml O2 h-1 g-0.67). According to this optimization, endothermy arose independently in Archosauromorpha, Sauropterygia and Therapsida. This article is part of the theme issue 'Vertebrate palaeophysiology'.
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Affiliation(s)
- Mathieu G Faure-Brac
- Sorbonne Université, Muséum national d'Histoire naturelle, CNRS, Centre de Recherche en Paléontologie-Paris (CR2P, UMR 7207), 4 place Jussieu, 75005 Paris, France
| | - Jorge Cubo
- Sorbonne Université, Muséum national d'Histoire naturelle, CNRS, Centre de Recherche en Paléontologie-Paris (CR2P, UMR 7207), 4 place Jussieu, 75005 Paris, France
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Lovegrove BG. Obligatory Nocturnalism in Triassic Archaic Mammals: Preservation of Sperm Quality? Physiol Biochem Zool 2019; 92:544-553. [DOI: 10.1086/705440] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Amson E, Kilbourne BM. Trabecular bone architecture in the stylopod epiphyses of mustelids (Mammalia, Carnivora). ROYAL SOCIETY OPEN SCIENCE 2019; 6:190938. [PMID: 31824706 PMCID: PMC6837213 DOI: 10.1098/rsos.190938] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 09/20/2019] [Indexed: 05/04/2023]
Abstract
Mustelidae, a carnivoran clade that includes for instance weasels, badgers, otters and martens, has undergone several evolutionary transitions of lifestyle, resulting in specializations for fossorial, natatorial and scansorial locomotion, in addition to more generalized species. The family is therefore regarded as offering an adequate framework for morpho-functional analyses. However, the architecture of the epiphyseal trabecular bone, which is argued to be particularly responsive to the biomechanical environment, has never been studied. Here, we quantify trabecular bone parameters of the proximal and distal epiphyses of the humerus and femur in 29 species of mustelids and assess the differences of these parameters among groups defined a priori based on the aforementioned locomotor types. The parameters are assessed in a phylogenetic framework, taking into account the potential effect on an individual's body mass. The range of variation described by the acquired parameters is relatively restricted when compared to that of other clades. Generalists, however, are featuring a wider range of variation than the other types. While clear discrimination of locomotor types is difficult, some differences were highlighted by our analysis, such as a greater bone fraction associated with the natatorial taxa, which we discuss in a functional context.
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Affiliation(s)
- E. Amson
- Author for correspondence: E. Amson e-mail:
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Wallace RVS, Martínez R, Rowe T. First record of a basal mammaliamorph from the early Late Triassic Ischigualasto Formation of Argentina. PLoS One 2019; 14:e0218791. [PMID: 31390368 PMCID: PMC6685608 DOI: 10.1371/journal.pone.0218791] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 06/06/2019] [Indexed: 12/03/2022] Open
Abstract
We describe a new probainognathian cynodont, Pseudotherium argentinus, from the early Late Triassic Ischigualasto Formation of Argentina. Pseudotherium adds to a growing assemblage of small Triassic cynodonts that offers new insight into events leading up to the origin of crown Mammalia and the successively more inclusive Mammaliaformes and Mammaliamorpha. Using high-resolution X-ray computed tomography, we illustrate and describe the holotype and only known specimen, which consists of a well-preserved isolated skull. It preserves apomorphic features of the orbit and braincase. Prefrontal and vestigial postorbital bones are present, despite the absence of an ossified postorbital bar. As in Brasilitherium riograndensis, thin turbinal-like bones are present in the nasopharyngeal passage, and we discuss impediments to establishing their identity and function. Compared to more basal cynodonts, the cochlea is elongated but uncoiled and in this and other features it resembles basal mammaliamorphs. Our analysis found weak support for Pseudotherium as the sister taxon of Tritylodontidae. However, a broader assessment of its relationships in light of additional character data from the literature and unpublished computed tomography data suggest that it may be more realistic to view the relationships of Pseudotherium as an unresolved polytomy with tritylodontids, and the taxa referred to as tritheledontids and brasilodontids (groups of variable membership and questionable monophyly). Thus, Pseudotherium may lie just inside or just outside of Mammaliamorpha, and there is also weak character support for its sister taxon relationship with Brasilitherium. Our results amplify previous conclusions that phylogenetic relationships in this adaptive radiation of small cynodonts will remain somewhat uncertain until more complete specimens are recovered, and until high-resolution CT scans of existing specimens become available to the larger community. Toward that goal, we make the CT dataset for the holotype of Pseudotherium argentinus publically available under a Creative Commons license at www.DigiMorph.org.
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Affiliation(s)
- Rachel V. S. Wallace
- Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, United States of America
| | - Ricardo Martínez
- División Paleontologia de Vertebrados, Instituto y Museo de Ciencias Naturales, Universidad Nacional de San Juan, San Juan, Argentina
| | - Timothy Rowe
- Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, United States of America
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Zhou CF, Bhullar BAS, Neander AI, Martin T, Luo ZX. New Jurassic mammaliaform sheds light on early evolution of mammal-like hyoid bones. Science 2019; 365:276-279. [DOI: 10.1126/science.aau9345] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 06/12/2019] [Indexed: 12/15/2022]
Affiliation(s)
- Chang-Fu Zhou
- Paleontological Museum of Liaoning, Shenyang Normal University, Shenyang Liaoning 110034, China
- College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
| | - Bhart-Anjan S. Bhullar
- Department of Geology and Geophysics and Peabody Museum of Natural History, Yale University, New Haven, CT 06511, USA
| | - April I. Neander
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, IL 60637, USA
| | - Thomas Martin
- Section Paleontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Zhe-Xi Luo
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, IL 60637, USA
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Grossnickle DM, Smith SM, Wilson GP. Untangling the Multiple Ecological Radiations of Early Mammals. Trends Ecol Evol 2019; 34:936-949. [PMID: 31229335 DOI: 10.1016/j.tree.2019.05.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/14/2019] [Accepted: 05/21/2019] [Indexed: 11/16/2022]
Abstract
The ecological diversification of early mammals is one of the most globally transformative events in Earth's history and the Cretaceous Terrestrial Revolution (KTR) and end-Cretaceous mass extinction are commonly hailed as catalysts. However, a confounding issue when examining this diversification is that it comprised nested radiations of mammalian subclades within the broader scope of mammalian evolution. In the past 200 million years, various independent groups experienced large-scale radiations, each involving ecological diversification from ancestral lineages of small insectivores; examples include Jurassic mammaliaforms, Late Cretaceous metatherians, and Cenozoic placentals. Here, we review these ecological radiations, highlighting the nuanced complexity of early mammal evolution, the value of ecomorphological fossil data, and the importance of phylogenetic context in macroevolutionary studies.
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Affiliation(s)
| | - Stephanie M Smith
- Integrative Research Center, Field Museum of Natural History, Chicago, IL, USA
| | - Gregory P Wilson
- Department of Biology, University of Washington, Seattle, WA, USA
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Lyons SK, Smith FA, Ernest SKM. Macroecological patterns of mammals across taxonomic, spatial, and temporal scales. J Mammal 2019. [DOI: 10.1093/jmammal/gyy171] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Affiliation(s)
- S Kathleen Lyons
- University of Nebraska–Lincoln, School of Biological Sciences, St. Lincoln, NE
| | - Felisa A Smith
- University of New Mexico, Department of Biology, Albuquerque, NM
| | - S K Morgan Ernest
- University of Florida, Department of Wildlife Ecology and Conservation, Gainesville, FL
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Chen M, Strömberg CAE, Wilson GP. Assembly of modern mammal community structure driven by Late Cretaceous dental evolution, rise of flowering plants, and dinosaur demise. Proc Natl Acad Sci U S A 2019; 116:9931-9940. [PMID: 31036651 PMCID: PMC6525522 DOI: 10.1073/pnas.1820863116] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The long-standing view that Mesozoic mammaliaforms living in dinosaur-dominated ecosystems were ecologically constrained to small size and insectivory has been challenged by astonishing fossil discoveries over the last three decades. By studying these well-preserved early mammaliaform specimens, paleontologists now agree that mammaliaforms underwent ecomorphological diversification during the Mesozoic Era. This implies that Mesozoic mammaliaform communities had ecological structure and breadth that were comparable to today's small-bodied mammalian communities. However, this hypothesis remains untested in part because the primary focus of most studies is on individual taxa. Here, we present a study quantifying the ecological structure of Mesozoic mammaliaform communities with the aim of identifying evolutionary and ecological drivers that influenced the deep-time assembly of small-bodied mammaliaform communities. We used body size, dietary preference, and locomotor mode to establish the ecospace occupation of 98 extant, small-bodied mammalian communities from diverse biomes around the world. We calculated ecological disparity and ecological richness to measure the magnitude of ecological differences among species in a community and the number of different eco-cells occupied by species of a community, respectively. This modern dataset served as a reference for analyzing five exceptionally preserved, extinct mammaliaform communities (two Jurassic, two Cretaceous, one Eocene) from Konservat-Lagerstätten. Our results indicate that the interplay of at least three factors, namely the evolution of the tribosphenic molar, the ecological rise of angiosperms, and potential competition with other vertebrates, may have been critical in shaping the ecological structure of small-bodied mammaliaform communities through time.
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Affiliation(s)
- Meng Chen
- School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (CAS), Nanjing 210008, China
| | - Caroline A E Strömberg
- Department of Biology, University of Washington, Seattle, WA 98195-1800
- Burke Museum of Natural History and Culture, University of Washington, Seattle, WA 98195-3010
| | - Gregory P Wilson
- Department of Biology, University of Washington, Seattle, WA 98195-1800;
- Burke Museum of Natural History and Culture, University of Washington, Seattle, WA 98195-3010
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Guignard ML, Martinelli AG, Soares MB. The postcranial anatomy of Brasilodon quadrangularis and the acquisition of mammaliaform traits among non-mammaliaform cynodonts. PLoS One 2019; 14:e0216672. [PMID: 31075140 PMCID: PMC6510408 DOI: 10.1371/journal.pone.0216672] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 04/25/2019] [Indexed: 11/20/2022] Open
Abstract
Brasilodon quadrangularis (Cynodontia, Probainognathia) is an iconic non-mammaliaform cynodont from the Late Triassic of Brazil (Riograndia Assemblage Zone, Candelária Sequence), being considered as the sister taxon of Mammaliaformes. Although its phylogenetic position is very important, several aspects of its postcranial anatomy remain unclear or unstudied. Here, we present a detailed description of the postcranial elements referred to Brasilodon, including previously mentioned specimens and new ones, which add relevant information about its postcranial morphology and provide a new insight into the anatomical transition between advanced non-mammaliaform cynodonts and early mammaliaforms. Functional and ecological implications are also investigated, based on the postcranial morphology and muscular reconstructions. The postcranium of Brasilodon differs from most non-mammaliaform cynodonts and presents similarities with tritylodontids, early mammaliaforms and extant therians, such as a ventrally oriented scapular glenoid facet, a distinct and ossified greater humeral tubercle, lack of ectepicondylar foramen, olecranon process, hemispherical humeral and femoral heads and a prominent intertrochanteric crest. The humeral torsion, the length of the deltopectoral crest, the large bicipital groove and the well-developed lesser tubercle, indicate that the forelimb of Brasilodon was hold in a semi-sprawling position, with well-developed adductor muscles to maintain the body off the ground. The short femoral neck and the strong medial projection of the femoral head indicate the femur was held in a more erect posture than in basal non-mammaliaform cynodonts. The anterodorsally projected iliac blade with reduced postacetabular process, reduction of the anterior part of the pubis, medially located lesser trochanter indicate a basically mammalian pattern of pelvic musculature, able to swing the femur in a nearly parasagittal plane.
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Affiliation(s)
- Morgan L. Guignard
- Programa de Pós-Graduação em Geociências, Universidade Federal do Rio Grande do Sul, Agronomia, Porto Alegre, Rio Grande do Sul, Brazil
- * E-mail:
| | - Agustin G. Martinelli
- CONICET-Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales ’Bernardino Rivadavia', Buenos Aires, Argentina
- Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Agronomia, Porto Alegre, Rio Grande do Sul, Brazil
| | - Marina B. Soares
- Programa de Pós-Graduação em Geociências, Universidade Federal do Rio Grande do Sul, Agronomia, Porto Alegre, Rio Grande do Sul, Brazil
- CONICET-Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales ’Bernardino Rivadavia', Buenos Aires, Argentina
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Jäger KRK, Luo ZX, Martin T. Postcranial Skeleton of Henkelotherium guimarotae (Cladotheria, Mammalia) and Locomotor Adaptation. J MAMM EVOL 2019. [DOI: 10.1007/s10914-018-09457-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Lambert O, Bianucci G, Salas-Gismondi R, Di Celma C, Steurbaut E, Urbina M, de Muizon C. An Amphibious Whale from the Middle Eocene of Peru Reveals Early South Pacific Dispersal of Quadrupedal Cetaceans. Curr Biol 2019; 29:1352-1359.e3. [PMID: 30955933 DOI: 10.1016/j.cub.2019.02.050] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/20/2019] [Accepted: 02/21/2019] [Indexed: 11/29/2022]
Abstract
Cetaceans originated in south Asia more than 50 million years ago (mya), from a small quadrupedal artiodactyl ancestor [1-3]. Amphibious whales gradually dispersed westward along North Africa and arrived in North America before 41.2 mya [4]. However, fossil evidence on when, through which pathway, and under which locomotion abilities these early whales reached the New World is fragmentary and contentious [5-7]. Peregocetus pacificus gen. et sp. nov. is a new protocetid cetacean discovered in middle Eocene (42.6 mya) marine deposits of coastal Peru, which constitutes the first indisputable quadrupedal whale record from the Pacific Ocean and the Southern Hemisphere. Preserving the mandibles and most of the postcranial skeleton, this unique four-limbed whale bore caudal vertebrae with bifurcated and anteroposteriorly expanded transverse processes, like those of beavers and otters, suggesting a significant contribution of the tail during swimming. The fore- and hind-limb proportions roughly similar to geologically older quadrupedal whales from India and Pakistan, the pelvis being firmly attached to the sacrum, an insertion fossa for the round ligament on the femur, and the retention of small hooves with a flat anteroventral tip at fingers and toes indicate that Peregocetus was still capable of standing and even walking on land. This new record from the southeastern Pacific demonstrates that early quadrupedal whales crossed the South Atlantic and nearly attained a circum-equatorial distribution with a combination of terrestrial and aquatic locomotion abilities less than 10 million years after their origin and probably before a northward dispersal toward higher North American latitudes. VIDEO ABSTRACT.
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Affiliation(s)
- Olivier Lambert
- D.O. Terre et Histoire de la Vie, Institut royal des Sciences naturelles de Belgique, Rue Vautier 29, 1000 Brussels, Belgium.
| | - Giovanni Bianucci
- Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa, Italy
| | - Rodolfo Salas-Gismondi
- BioGeoCiencias Lab, Facultad de Ciencias y Filosofía/CIDIS, Universidad Peruana Cayetano Heredia, Lima, Peru; Departamento de Paleontología de Vertebrados, Museo de Historia Natural-UNMSM, Avenida Arenales 1256, 14 Lima, Peru
| | - Claudio Di Celma
- Scuola di Scienze e Tecnologie, Università di Camerino, Via Gentile III da Varano 1, 62032 Camerino, Italy
| | - Etienne Steurbaut
- D.O. Terre et Histoire de la Vie, Institut royal des Sciences naturelles de Belgique, Rue Vautier 29, 1000 Brussels, Belgium; Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, 3001 Leuven, Belgium
| | - Mario Urbina
- Departamento de Paleontología de Vertebrados, Museo de Historia Natural-UNMSM, Avenida Arenales 1256, 14 Lima, Peru
| | - Christian de Muizon
- Centre de Recherche en Paléontologie-Paris, CR2P (CNRS, MNHN, Sorbonne-Université), Département Origines et Évolution, Muséum national d'Histoire naturelle, 8, Rue Buffon 75005 Paris, France
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Antiquity of forelimb ecomorphological diversity in the mammalian stem lineage (Synapsida). Proc Natl Acad Sci U S A 2019; 116:6903-6907. [PMID: 30886085 PMCID: PMC6452662 DOI: 10.1073/pnas.1802543116] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mammals and their closest fossil relatives use their shoulders and forelimbs for many functions, which is reflected by the great range of mammalian forelimb shapes. We found that forelimb shape diversity in the early mammalian lineage (Synapsida) began to increase about 270 million years ago, with the emergence of a group called Therapsida, and is accompanied by new forelimb functions. The functional diversification of therapsid forelimbs was curtailed by the Permo-Triassic mass extinction, but eventually continued as more mammal-like therapsids evolved new ecologies. Our analyses characterize the deep time origin of a quintessential part of the mammalian body plan: evolutionarily labile forelimbs that can be deployed in a wide range of functional and ecological roles. Mammals and their closest fossil relatives are unique among tetrapods in expressing a high degree of pectoral girdle and forelimb functional diversity associated with fully pelagic, cursorial, subterranean, volant, and other lifestyles. However, the earliest members of the mammalian stem lineage, the “pelycosaur”-grade synapsids, present a far more limited range of morphologies and inferred functions. The more crownward nonmammaliaform therapsids display novel forelimb morphologies that have been linked to expanded functional diversity, suggesting that the roots of this quintessentially mammalian phenotype can be traced to the pelycosaur–therapsid transition in the Permian period. We quantified morphological disparity of the humerus in pelycosaur-grade synapsids and therapsids using geometric morphometrics. We found that disparity begins to increase concurrently with the emergence of Therapsida, and that it continues to rise until the Permo-Triassic mass extinction. Further, therapsid exploration of new regions of morphospace is correlated with the evolution of novel ecomorphologies, some of which are characterized by changes to overall limb morphology. This evolutionary pattern confirms that nonmammaliaform therapsid forelimbs underwent ecomorphological diversification throughout the Permian, with functional elaboration initially being more strongly expressed in the proximal end of the humerus than the distal end. The role of the forelimbs in the functional diversification of therapsids foreshadows the deployment of forelimb morphofunctional diversity in the evolutionary radiation of mammals.
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Bertolesi GE, Zhang JZ, McFarlane S. Plasticity for colour adaptation in vertebrates explained by the evolution of the genes pomc, pmch and pmchl. Pigment Cell Melanoma Res 2019; 32:510-527. [PMID: 30791235 PMCID: PMC7167667 DOI: 10.1111/pcmr.12776] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 01/27/2019] [Accepted: 02/16/2019] [Indexed: 02/06/2023]
Abstract
Different camouflages work best with some background matching colour. Our understanding of the evolution of skin colour is based mainly on the genetics of pigmentation ("background matching"), with little known about the evolution of the neuroendocrine systems that facilitate "background adaptation" through colour phenotypic plasticity. To address the latter, we studied the evolution in vertebrates of three genes, pomc, pmch and pmchl, that code for α-MSH and two melanin-concentrating hormones (MCH and MCHL). These hormones induce either dispersion/aggregation or the synthesis of pigments. We find that α-MSH is highly conserved during evolution, as is its role in dispersing/synthesizing pigments. Also conserved is the three-exon pmch gene that encodes MCH, which participates in feeding behaviours. In contrast, pmchl (known previously as pmch), is a teleost-specific intron-less gene. Our data indicate that in zebrafish, pmchl-expressing neurons extend axons to the pituitary, supportive of an MCHL hormonal role, whereas zebrafish and Xenopus pmch+ neurons send axons dorsally in the brain. The evolution of these genes and acquisition of hormonal status for MCHL explain different mechanisms used by vertebrates to background-adapt.
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Affiliation(s)
- Gabriel E Bertolesi
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - John Zhijia Zhang
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Sarah McFarlane
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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Kilbourne BM, Hutchinson JR. Morphological diversification of biomechanical traits: mustelid locomotor specializations and the macroevolution of long bone cross-sectional morphology. BMC Evol Biol 2019; 19:37. [PMID: 30700269 PMCID: PMC6354431 DOI: 10.1186/s12862-019-1349-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 01/02/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Morphological diversity of limb bone lengths, diameters, and proportions in mammals is known to vary strongly with locomotor habit. It remains less well known how different locomotor habits are correlated with cross-sectional traits of the limb skeleton, such as cross-sectional area (CSA), second moments of area (SMA), and section modulus (MOD) and whether these traits have evolved adaptively. CSA and SMA represent the bone's resistance to axial compression and bending, respectively, whereas MOD represents bone structural strength related to shape. Sampling 28 species of mustelids, a carnivoran lineage with diverse locomotor habits, we tested for differences in humeral, radial, and ulnar cross-sectional traits among specialists for climbing, digging, and swimming, in addition to generalists. Given that the limbs of digging specialists function in the dense substance of soil, and that swimming specialists need to counteract buoyancy, we predicted that these mustelids with these specializations should have the greatest values of cross-sectional traits. RESULTS We analyzed cross-sectional traits (calculated via μCT scanning and rendered dimensionless) in 5% increments along a bone's length and found significant differences among locomotor habits, though differences in ulnar cross-sectional traits were fewer than those for the humerus and radius. Swimming specialists had the greatest values of cross-sectional traits, followed by digging specialists. Climbing specialists had the lowest values of cross-sectional traits. However, phylogenetic affinity underlies these results. Fitting models of trait evolution to CSA and SMA revealed that a multi-rate Brownian motion model and a multi-optima Ornstein-Uhlenbeck model are the best-fitting models of evolution for these traits. However, inspection of α-values uncovered that many of the OU models did not differ from a Brownian motion model. CONCLUSIONS Within Mustelidae, differences in limb function and locomotor habit influence cross-sectional traits in ways that produce patterns that may diverge from adaptive patterns exhibited by external traits (e.g., bone lengths) of the mammalian limb skeleton. These results suggest that not all the traits of a single organ evolve under a single evolutionary process and that models of trait evolution should be fit to a range of traits for a better understanding of the evolution of the mammalian locomotor system.
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Affiliation(s)
- Brandon M Kilbourne
- Museum für Naturkunde Berlin, Leibniz Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115, Berlin, Germany.
| | - John R Hutchinson
- Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Hatfield, AL9 7TA, UK
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Mao FY, Meng J. A new haramiyidan mammal from the Jurassic Yanliao Biota and comparisons with other haramiyidans. Zool J Linn Soc 2019. [DOI: 10.1093/zoolinnean/zly088] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Fang-Yuan Mao
- Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
- CAS Center for Excellence in Life and Paleoenvironment, Beijing, China
| | - Jin Meng
- Division of Paleontology, American Museum of Natural History, New York, New York, USA
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Erwin DH. The topology of evolutionary novelty and innovation in macroevolution. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0422. [PMID: 29061895 PMCID: PMC5665810 DOI: 10.1098/rstb.2016.0422] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/16/2017] [Indexed: 12/30/2022] Open
Abstract
Sewall Wright's fitness landscape introduced the concept of evolutionary spaces in 1932. George Gaylord Simpson modified this to an adaptive, phenotypic landscape in 1944 and since then evolutionary spaces have played an important role in evolutionary theory through fitness and adaptive landscapes, phenotypic and functional trait spaces, morphospaces and related concepts. Although the topology of such spaces is highly variable, from locally Euclidean to pre-topological, evolutionary change has often been interpreted as a search through a pre-existing space of possibilities, with novelty arising by accessing previously inaccessible or difficult to reach regions of a space. Here I discuss the nature of evolutionary novelty and innovation within the context of evolutionary spaces, and argue that the primacy of search as a conceptual metaphor ignores the generation of new spaces as well as other changes that have played important evolutionary roles.This article is part of the themed issue 'Process and pattern in innovations from cells to societies'.
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Affiliation(s)
- Douglas H Erwin
- Department of Paleobiology MRC-121, National Museum of Natural History, Smithsonian Institution, PO Box 37012, DC 20013-7012, USA .,Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA
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Pritchard AC, Gauthier JA, Hanson M, Bever GS, Bhullar BAS. A tiny Triassic saurian from Connecticut and the early evolution of the diapsid feeding apparatus. Nat Commun 2018; 9:1213. [PMID: 29572441 PMCID: PMC5865133 DOI: 10.1038/s41467-018-03508-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 02/20/2018] [Indexed: 11/25/2022] Open
Abstract
Following the Permo–Triassic Extinction, large-bodied diapsid reptiles—with a body length >1 m—rapidly expanded their ecological roles. This diversification is reflected in enormous disparity in the development of the rostrum and adductor chamber. However, it is unclear how marked the diversity of the feeding apparatus was in contemporary small-bodied diapsids. Here we describe the remarkably small skull (2.5 cm long) of a saurian reptile, Colobops noviportensis, gen. et sp. nov., from the Triassic New Haven Arkose of Connecticut, USA. The taxon possesses an exceptionally reinforced snout and strikingly expanded supratemporal fossae for adductor musculature relative to any known Mesozoic or Recent diapsid of similar size. Our phylogenetic analyses support C. noviportensis as an early diverging pan-archosaur. Colobops noviportensis reveals extraordinary disparity of the feeding apparatus in small-bodied early Mesozoic diapsids, and a suite of morphologies, functionally related to a powerful bite, unknown in any small-bodied diapsid. The Triassic fossil record is biased towards large species, obscuring the anatomical diversity of small species. Here, the authors describe a new species, Colobops noviportensis, based on a 2.5 cm-long skull with proportionally large attachments for jaw muscles, expanding the known diversity of early diapsids.
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Affiliation(s)
- Adam C Pritchard
- Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT, 06511, USA.
| | - Jacques A Gauthier
- Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT, 06511, USA.,Yale Peabody Museum of Natural History, Yale University, 170 Whitney Avenue, New Haven, CT, 06511, USA
| | - Michael Hanson
- Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT, 06511, USA
| | - Gabriel S Bever
- Center for Functional Anatomy and Evolution, School of Medicine, Johns Hopkins University, 1830 E. Monument Street, Baltimore, MD, 21205, USA
| | - Bhart-Anjan S Bhullar
- Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT, 06511, USA. .,Yale Peabody Museum of Natural History, Yale University, 170 Whitney Avenue, New Haven, CT, 06511, USA.
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Lai PH, Biewener AA, Pierce SE. Three-dimensional mobility and muscle attachments in the pectoral limb of the Triassic cynodont Massetognathus pascuali (Romer, 1967). J Anat 2018; 232:383-406. [PMID: 29392730 PMCID: PMC5807948 DOI: 10.1111/joa.12766] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2017] [Indexed: 01/21/2023] Open
Abstract
The musculoskeletal configuration of the mammalian pectoral limb has been heralded as a key anatomical feature leading to the adaptive radiation of mammals, but limb function in the non-mammaliaform cynodont outgroup remains unresolved. Conflicting reconstructions of abducted and adducted posture are based on mutually incompatible interpretations of ambiguous osteology. We reconstruct the pectoral limb of the Triassic non-mammaliaform cynodont Massetognathus pascuali in three dimensions, by combining skeletal morphology from micro-computed tomography with muscle anatomy from an extended extant phylogenetic bracket. Conservative tests of maximum range of motion suggest a degree of girdle mobility, as well as substantial freedom at the shoulder and the elbow joints. The glenoid fossa supports a neutral pose in which the distal end of the humerus points 45° posterolaterally from the body wall, intermediate between classically 'sprawling' and 'parasagittal' limb postures. Massetognathus pascuali is reconstructed as having a near-mammalian complement of shoulder muscles, including an incipient rotator cuff (m. subscapularis, m. infraspinatus, m. supraspinatus, and m. teres minor). Based on close inspection of the morphology of the glenoid fossa, we hypothesize a posture-driven scenario for the evolution of the therian ball-and-socket shoulder joint. The musculoskeletal reconstruction presented here provides the anatomical scaffolding for more detailed examination of locomotor evolution in the precursors to mammals.
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Affiliation(s)
- Phil H. Lai
- Museum of Comparative Zoology and Department of Organismic and Evolutionary BiologyHarvard UniversityCambridgeMAUSA
- Concord Field Station and Department of Organismic and Evolutionary BiologyHarvard UniversityBedfordMAUSA
| | - Andrew A. Biewener
- Concord Field Station and Department of Organismic and Evolutionary BiologyHarvard UniversityBedfordMAUSA
| | - Stephanie E. Pierce
- Museum of Comparative Zoology and Department of Organismic and Evolutionary BiologyHarvard UniversityCambridgeMAUSA
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Re-examination of the Jurassic Mammaliaform Docodon victor by Computed Tomography and Occlusal Functional Analysis. J MAMM EVOL 2017. [DOI: 10.1007/s10914-017-9418-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Ferner K, Schultz JA, Zeller U. Comparative anatomy of neonates of the three major mammalian groups (monotremes, marsupials, placentals) and implications for the ancestral mammalian neonate morphotype. J Anat 2017; 231:798-822. [PMID: 28960296 PMCID: PMC5696127 DOI: 10.1111/joa.12689] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/08/2017] [Indexed: 12/16/2022] Open
Abstract
The existing different modes of reproduction in monotremes, marsupials and placentals are the main source for our current understanding of the origin and evolution of the mammalian reproduction. The reproductive strategies and, in particular, the maturity states of the neonates differ remarkably between the three groups. Monotremes, for example, are the only extant mammals that lay eggs and incubate them for the last third of their embryonic development. In contrast, marsupials and placentals are viviparous and rely on intra-uterine development of the neonates via choriovitelline (mainly marsupials) and chorioallantoic (mainly placentals) placentae. The maturity of a newborn is closely linked to the parental care strategy once the neonate is born. The varying developmental degrees of neonates are the main focus of this study. Monotremes and marsupials produce highly altricial and nearly embryonic offspring. Placental mammals always give birth to more developed newborns with the widest range from altricial to precocial. The ability of a newborn to survive and grow in the environment it was born in depends highly on the degree of maturation of vital organs at the time of birth. Here, the anatomy of four neonates of the three major extant mammalian groups is compared. The basis for this study is histological and ultrastructural serial sections of a hatchling of Ornithorhynchus anatinus (Monotremata), and neonates of Monodelphis domestica (Marsupialia), Mesocricetus auratus (altricial Placentalia) and Macroscelides proboscideus (precocial Placentalia). Special attention was given to the developmental stages of the organs skin, lung, liver and kidney, which are considered crucial for the maintenance of vital functions. The state of the organs of newborn monotremes and marsupials are found to be able to support a minimum of vital functions outside the uterus. They are sufficient to survive, but without capacities for additional energetic challenges. The organs of the altricial placental neonate are further developed, able to support the maintenance of vital functions and short-term metabolic increase. The precocial placental newborn shows the most advanced state of organ development, to allow the maintenance of vital functions, stable thermoregulation and high energetic performance. The ancestral condition of a mammalian neonate is interpreted to be similar to the state of organ development found in the newborns of marsupials and monotremes. In comparison, the newborns of altricial and precocial placentals are derived from the ancestral state to a more mature developmental degree associated with advanced organ systems.
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Affiliation(s)
- Kirsten Ferner
- Leibniz‐Institut für Evolutions‐ und BiodiversitätsforschungMuseum für NaturkundeBerlinGermany
| | - Julia A. Schultz
- Department of Organismal Biology and AnatomyUniversity of ChicagoChicagoILUSA
| | - Ulrich Zeller
- Lebenswissenschaftliche FakultätFG Spezielle ZoologieAlbrecht Daniel Thaer‐Institut für Agrar‐ und GartenbauwissenschaftenHumboldt‐Universität zu BerlinBerlinGermany
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