1
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Arnold P, Janiszewska K, Li Q, O'Connor JK, Fostowicz-Frelik Ł. The Late Cretaceous eutherian Zalambdalestes reveals unique axis and complex evolution of the mammalian neck. Sci Bull (Beijing) 2024; 69:1767-1775. [PMID: 38702276 DOI: 10.1016/j.scib.2024.04.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 03/24/2024] [Accepted: 03/26/2024] [Indexed: 05/06/2024]
Abstract
The typical mammalian neck consisting of seven cervical vertebrae (C1-C7) was established by the Late Permian in the cynodont forerunners of modern mammals. This structure is precisely adapted to facilitate movements of the head during feeding, locomotion, predator evasion, and social interactions. Eutheria, the clade including crown placentals, has a fossil record extending back more than 125 million years revealing significant morphological diversification in the Mesozoic. Yet very little is known concerning the early evolution of eutherian cervical morphology and its functional adaptations. A specimen of Zalambdalestes lechei from the Late Cretaceous of Mongolia boasts exceptional preservation of an almost complete series of cervical vertebrae (C2-C7) revealing a highly modified axis (C2). The significance of this cervical morphology is explored utilizing an integrated approach combining comparative anatomical examination across mammals, muscle reconstruction, geometric morphometrics and virtual range of motion analysis. We compared the shape of the axis in Zalambdalestes to a dataset of 88 mammalian species (monotremes, marsupials, and placentals) using three-dimensional landmark analysis. The results indicate that the unique axis morphology of Zalambdalestes has no close analog among living mammals. Virtual range of motion analysis of the neck strongly implies Zalambdalestes was capable of exerting very forceful head movements and had a high degree of ventral flexion for an animal its size. These findings reveal unexpected complexity in the early evolution of the eutherian cervical morphology and suggest a feeding behavior similar to insectivores specialized in vermivory and defensive behaviors in Zalambdalestes akin to modern spiniferous mammals.
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Affiliation(s)
- Patrick Arnold
- Institute of Biochemistry and Biology, University of Potsdam, Potsdam D-14476, Germany
| | - Katarzyna Janiszewska
- Environmental Paleobiology Department, Institute of Paleobiology, Polish Academy of Sciences, Warsaw 00-818, Poland
| | - Qian Li
- Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | | | - Łucja Fostowicz-Frelik
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago IL 60637, USA; Evolutionary Paleobiology Department, Institute of Paleobiology, Polish Academy of Sciences, Warsaw 00-818, Poland.
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2
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Villamil CI, Middleton ER. Conserved patterns and locomotor-related evolutionary constraints in the hominoid vertebral column. J Hum Evol 2024; 190:103528. [PMID: 38579429 DOI: 10.1016/j.jhevol.2024.103528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 03/13/2024] [Accepted: 03/14/2024] [Indexed: 04/07/2024]
Abstract
The evolution of the hominoid lineage is characterized by pervasive homoplasy, notably in regions such as the vertebral column, which plays a central role in body support and locomotion. Few isolated and fewer associated vertebrae are known for most fossil hominoid taxa, but identified specimens indicate potentially high levels of convergence in terms of both form and number. Homoplasy thus complicates attempts to identify the anatomy of the last common ancestor of hominins and other taxa and stymies reconstructions of evolutionary scenarios. One way to clarify the role of homoplasy is by investigating constraints via phenotypic integration, which assesses covariation among traits, shapes evolutionary pathways, and itself evolves in response to selection. We assessed phenotypic integration and evolvability across the subaxial (cervical, thoracic, lumbar, sacral) vertebral column of macaques (n = 96), gibbons (n = 77), chimpanzees (n = 92), and modern humans (n = 151). We found a mid-cervical cluster that may have shifted cranially in hominoids, a persistent thoracic cluster that is most marked in chimpanzees, and an expanded lumbosacral cluster in hominoids that is most expanded in gibbons. Our results highlight the highly conserved nature of the vertebral column. Taxa appear to exploit existing patterns of integration and ontogenetic processes to shift, expand, or reduce cluster boundaries. Gibbons appear to be the most highly derived taxon in our sample, possibly in response to their highly specialized locomotion.
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Affiliation(s)
- Catalina I Villamil
- School of Chiropractic, Universidad Central del Caribe, Puerto Rico, PO Box 60327, Bayamón, USA.
| | - Emily R Middleton
- Department of Anthropology, University of Wisconsin-Milwaukee, 3413 N. Downer Ave., Sabin Hall 390, Milwaukee, WI, USA
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3
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Anderson RS, Chu AK, Rylander H, Binversie EE, Duncan ID, Baker L, Salamat S, Patterson MM, Gruel J, Kohler NL, Kearney HK, Ale SM, Momen MM, Muir P, Svaren JP, Johnson R, Sample SJ. Pathologic classification of a late-onset peripheral neuropathy in a spontaneous Labrador retriever dog model. J Comp Neurol 2024; 532:e25596. [PMID: 38439568 PMCID: PMC10914337 DOI: 10.1002/cne.25596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 12/21/2023] [Accepted: 02/09/2024] [Indexed: 03/06/2024]
Abstract
Late-onset peripheral neuropathy (LPN) is a heritable canine neuropathy commonly found in Labrador retrievers and is characterized by laryngeal paralysis and pelvic limb paresis. Our objective was to establish canine LPN as a model for human hereditary peripheral neuropathy by classifying it as either an axonopathy or myelinopathy and evaluating length-dependent degeneration. We conducted a motor nerve conduction study of the sciatic and ulnar nerves, electromyography (EMG) of appendicular and epaxial musculature, and histologic analysis of sciatic and recurrent laryngeal nerves in LPN-affected and control dogs. LPN-affected dogs exhibited significant decreases in compound muscle action potential (CMAP) amplitude, CMAP area, and pelvic limb latencies. However, no differences were found in motor nerve conduction velocity, residual latencies, or CMAP duration. Distal limb musculature showed greater EMG changes in LPN-affected dogs. Histologically, LPN-affected dogs exhibited a reduction in the number of large-diameter axons, especially in distal nerve regions. In conclusion, LPN in Labrador retrievers is a common, spontaneous, length-dependent peripheral axonopathy that is a novel animal model of age-related peripheral neuropathy that could be used for fundamental research and clinical trials.
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Affiliation(s)
- Ryan S. Anderson
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Alexander K. Chu
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Helena Rylander
- Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Emily E. Binversie
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Ian D. Duncan
- Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Lauren Baker
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Shahriar Salamat
- Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, 750 Highland Ave, Madison, WI 53726
| | - Margaret M. Patterson
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Jordan Gruel
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Nyah L. Kohler
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Hannah K Kearney
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Shelby M. Ale
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Mehdi M. Momen
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Peter Muir
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - John P. Svaren
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Rebecca Johnson
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
| | - Susannah J Sample
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Dr, Madison, WI 53706:
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4
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May-Davis S, Dzingle D, Saber E, Blades Eckelbarger P. Characterization of the Caudal Ventral Tubercle in the Sixth Cervical Vertebra in Modern Equus ferus caballus. Animals (Basel) 2023; 13:2384. [PMID: 37508161 PMCID: PMC10376820 DOI: 10.3390/ani13142384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 07/10/2023] [Accepted: 07/20/2023] [Indexed: 07/30/2023] Open
Abstract
This study examined the anomalous variations of the ventral process of C6 in modern E. ferus caballus. The aim was to provide an incremental grading protocol measuring the absence of the caudal ventral tubercle (CVT) in this ventral process. The findings revealed the most prevalent absent CVT (aCVT) was left unilateral (n = 35), with bilateral (n = 29) and right unilateral (n = 12). Grading was determined in equal increments of absence 1/4, 2/4, 3/4, with 4/4 representing a complete aCVT in 56/76, with a significance of p = 0.0013. This also applied to bilateral specimens. In those C6 osseous specimens displaying a 4/4 grade aCVT, 41/56 had a partial absence of the caudal aspect of the cranial ventral tubercle (CrVT). Here, grading absent CrVTs (aCrVT) followed similarly to aCVTs, though 4/4 was not observed. The significance between 4/4 grade aCVTs and the presentation of an aCrVT was left p = 0.00001 and right p = 0.00018. In bilateral specimens, C6 morphologically resembled C5, implying a homeotic transformation that limited the attachment sites for the cranial and thoracal longus colli muscle. This potentially diminishes function and caudal cervical stability. Therefore, it is recommended that further studies examine the morphological extent of this equine complex vertebral malformation (ECVM) as well as its interrelationships and genetic code/blueprint.
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Affiliation(s)
- Sharon May-Davis
- Canine and Equine Research Group, University of New England, Armidale, NSW 2351, Australia
| | - Diane Dzingle
- Equus Soma-Equine Osteology and Anatomy Learning Center, Aiken, SC 29805, USA
| | - Elle Saber
- Biological Data Science Institute, Australian National University, Canberra, ACT 2601, Australia
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5
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May-Davis S, Hunter R, White R. Morphology of the Ventral Process of the Sixth Cervical Vertebra in Extinct and Extant Equus: Functional Implications. Animals (Basel) 2023; 13:ani13101672. [PMID: 37238101 DOI: 10.3390/ani13101672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 05/07/2023] [Accepted: 05/15/2023] [Indexed: 05/28/2023] Open
Abstract
In this study, we examined the ventral process of C6 in extinct and extant Equus (sister taxa to Equus ferus caballus only) with the purpose of describing normal morphology and identifying anomalous variations relevant to recent studies describing a congenital malformation in E. ferus caballus. Overall, 83 specimens from 9 museums and 3 research/educational facilities were examined, totalling 71 extinct specimens from 12 species and 12 extant specimens from 5 species. The lateral view revealed that a large convexity exists in the ventral process between the cranial ventral tubercle (CrVT) and the caudal ventral tubercle (CVT) in the earliest ancestor, Hyracotherium grangeri, from 55 mya, which receded throughout the millennia to become a smaller convexity in E. ferus caballus and the sister taxa. The CrVT is visibly shorter and narrower than the CVT, with a constricted section directly ventral to the transverse process, essentially demarcating the CrVT and CVT. No congenital malformations were evident. As the ventral process of C6 is an integral component for muscle attachment in supporting the head/neck during posture and locomotion, this would indicate that the caudal module in the cervical column might be compromised when a partial or complete absence of the CVT is detected via radiographs in modern E. ferus caballus.
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Affiliation(s)
- Sharon May-Davis
- Canine and Equine Research Group, University of New England, Armidale, NSW 2351, Australia
| | - Robert Hunter
- Canine and Equine Research Group, University of New England, Armidale, NSW 2351, Australia
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6
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Linden TJ, Burtner AE, Rickman J, McFeely A, Santana SE, Law CJ. Scaling patterns of body plans differ among squirrel ecotypes. PeerJ 2023; 11:e14800. [PMID: 36718452 PMCID: PMC9884040 DOI: 10.7717/peerj.14800] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 01/04/2023] [Indexed: 01/26/2023] Open
Abstract
Body size is often hypothesized to facilitate or constrain morphological diversity in the cranial, appendicular, and axial skeletons. However, how overall body shape scales with body size (i.e., body shape allometry) and whether these scaling patterns differ between ecological groups remains poorly investigated. Here, we test whether and how the relationships between body shape, body size, and limb lengths differ among species with different locomotor specializations, and describe the underlying morphological components that contribute to body shape evolution among squirrel (Sciuridae) ecotypes. We quantified the body size and shape of 87 squirrel species from osteological specimens held at museum collections. Using phylogenetic comparative methods, we first found that body shape and its underlying morphological components scale allometrically with body size, but these allometric patterns differ among squirrel ecotypes: chipmunks and gliding squirrels exhibited more elongate bodies with increasing body sizes whereas ground squirrels exhibited more robust bodies with increasing body size. Second, we found that only ground squirrels exhibit a relationship between forelimb length and body shape, where more elongate species exhibit relatively shorter forelimbs. Third, we found that the relative length of the ribs and elongation or shortening of the thoracic region contributes the most to body shape evolution across squirrels. Overall, our work contributes to the growing understanding of mammalian body shape evolution and how it is influenced by body size and locomotor ecology, in this case from robust subterranean to gracile gliding squirrels.
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Affiliation(s)
- Tate J. Linden
- University of Washington, Seattle, WA, United States of America
| | | | | | - Annika McFeely
- University of Washington, Seattle, WA, United States of America
| | | | - Chris J. Law
- University of Washington, Seattle, WA, United States of America,University of Texas at Austin, Austin, TX, United States of America,American Museum of Natural History, New York, NY, United States of America
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7
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Grider‐Potter N, Rummel A. Dietary influences on head and neck ranges of motion in neotropical bats. J Zool (1987) 2022. [DOI: 10.1111/jzo.13011] [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]
Affiliation(s)
- N. Grider‐Potter
- Cell Systems and Anatomy University of Texas Health San Antonio San Antonio TX USA
- Southwest National Primate Research Center Texas Biomedical Research Institute San Antonio TX USA
| | - A. Rummel
- Department of Ecology and Evolutionary Biology Princeton University Princeton NJ USA
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8
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Brocklehurst N, Ford DP, Benson RBJ. Early origins of divergent patterns of morphological evolution on the mammal and reptile stem-lineages. Syst Biol 2022; 71:1195-1209. [PMID: 35274702 PMCID: PMC9366456 DOI: 10.1093/sysbio/syac020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 02/09/2022] [Accepted: 03/05/2022] [Indexed: 11/28/2022] Open
Abstract
The origin of amniotes 320 million years ago signaled independence from water in vertebrates and was closely followed by divergences within the mammal and reptile stem lineages (Synapsida and Reptilia). Early members of both groups had highly similar morphologies, being superficially “lizard-like” forms with many plesiomorphies. However, the extent to which they might have exhibited divergent patterns of evolutionary change, with the potential to explain the large biological differences between their living members, is unresolved. We use a new, comprehensive phylogenetic dataset to quantify variation in rates and constraints of morphological evolution among Carboniferous–early Permian amniotes. We find evidence for an early burst of evolutionary rates, resulting in the early origins of morphologically distinctive subgroups that mostly persisted through the Cisuralian. Rates declined substantially through time, especially in reptiles. Early reptile evolution was also more constrained compared with early synapsids, exploring a more limited character state space. Postcranial innovation in particular was important in early synapsids, potentially related to their early origins of large body size. In contrast, early reptiles predominantly varied the temporal region, suggesting disparity in skull and jaw kinematics, and foreshadowing the variability of cranial biomechanics seen in reptiles today. Our results demonstrate that synapsids and reptiles underwent an early divergence of macroevolutionary patterns. This laid the foundation for subsequent evolutionary events and may be critical in understanding the substantial differences between mammals and reptiles today. Potential explanations include an early divergence of developmental processes or of ecological factors, warranting cross-disciplinary investigation. [Amniote; body size; constraint; phylogeny; rate.]
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Affiliation(s)
- Neil Brocklehurst
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, UK
| | - David P Ford
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, UK
| | - Roger B J Benson
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, UK
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9
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Arlegi M, Pantoja-Pérez A, Veschambre-Couture C, Gómez-Olivencia A. Covariation between the cranium and the cervical vertebrae in hominids. J Hum Evol 2021; 162:103112. [PMID: 34894608 DOI: 10.1016/j.jhevol.2021.103112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/26/2021] [Accepted: 10/26/2021] [Indexed: 11/16/2022]
Abstract
The analysis of patterns of integration is crucial for the reconstruction and understanding of how morphological changes occur in a taxonomic group throughout evolution. These patterns are relatively constant; however, both patterns and the magnitudes of integration may vary across species. These differences may indicate morphological diversification, in some cases related to functional adaptations to the biomechanics of organisms. In this study, we analyze patterns of integration between two functional and developmental structures, the cranium and the cervical spine in hominids, and we quantify the amount of divergence of each anatomical element through phylogeny. We applied these methods to three-dimensional data from 168 adult hominid individuals, summing a total of more than 1000 cervical vertebrae. We found the atlas (C1) and axis (C2) display the lowest covariation with the cranium in hominids (Homo sapiens, Pan troglodytes, Pan paniscus, Gorilla gorilla, Gorilla beringei, Pongo pygmaeus). H. sapiens show a relatively different pattern of craniocervical correlation compared with chimpanzees and gorillas, especially in variables implicated in maintaining the balance of the head. Finally, the atlas and axis show lower magnitude of shape change during evolution than the rest of the cervical vertebrae, especially those located in the middle of the subaxial cervical spine. Overall, results suggest that differences in the pattern of craniocervical correlation between humans and gorillas and chimpanzees could reflect the postural differences between these groups. Also, the stronger craniocervical integration and larger magnitude of shape change during evolution shown by the middle cervical vertebrae suggests that they have been selected to play an active role in maintaining head balance.
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Affiliation(s)
- Mikel Arlegi
- Institut Català de Paleoecologia Humana i Evolució Social (IPHES-CERCA), Zona Educacional 4, Campus Sescelades URV (Edifici W3), 43007 Tarragona, Spain; Universitat Rovira i Virgili, Department d'Història i Història de l'Art, Avinguda de Catalunya 35, 43002 Tarragona, Spain.
| | - Ana Pantoja-Pérez
- Centro UCM-ISCIII de Investigación sobre Evolución y Comportamiento Humanos, Avda. Monforte de Lemos 5 (Pabellón 14), 28029 Madrid, Spain
| | - Christine Veschambre-Couture
- UMR 5199 PACEA, Université de Bordeaux, Allée Geoffroy Saint Hilaire, Bâtiment B8, CS 50023, 33615, Pessac Cedex, France
| | - Asier Gómez-Olivencia
- Departamento de Geología, Facultad de Ciencia y Tecnología, Universidad del País Vasco-Euskal Herriko Unibertsitatea (UPV/EHU), Barrio Sarriena S/n, 48940 Leioa, Spain; Sociedad de Ciencias Aranzadi, Zorroagagaina 11, 20014 Donostia-San Sebastián, Spain; Centro UCM-ISCIII de Investigación sobre Evolución y Comportamiento Humanos, Avda. Monforte de Lemos 5 (Pabellón 14), 28029 Madrid, Spain
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10
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Hofmann R, Lehmann T, Warren DL, Ruf I. The squirrel is in the detail: Anatomy and morphometry of the tail in Sciuromorpha (Rodentia, Mammalia). J Morphol 2021; 282:1659-1682. [PMID: 34549832 DOI: 10.1002/jmor.21412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Revised: 09/09/2021] [Accepted: 09/15/2021] [Indexed: 11/07/2022]
Abstract
In mammals, the caudal vertebrae are certainly among the least studied elements of their skeleton. However, the tail plays an important role in locomotion (e.g., balance, prehensility) and behavior (e.g., signaling). Previous studies largely focused on prehensile tails in Primates and Carnivora, in which certain osteological features were selected and used to define tail regions (proximal, transitional, distal). Interestingly, the distribution pattern of these anatomical characters and the relative proportions of the tail regions were similar in both orders. In order to test if such tail regionalization can be applied to Rodentia, we investigated the caudal vertebrae of 20 Sciuridae and six Gliridae species. Furthermore, we examined relationships between tail anatomy/morphometry and locomotion. The position of selected characters along the tail was recorded and their distribution was compared statistically using Spearman rank correlation. Vertebral body length (VBL) was measured to calculate the proportions of each tail region and to perform procrustes analysis on the shape of relative vertebral body length (rVBL) progressions. Our results show that tail regionalization, as defined for Primates and Carnivora, can be applied to almost all investigated squirrels, regardless of their locomotor category. Moreover, major locomotor categories can be distinguished by rVBL progression and tail region proportions. In particular, the small flying squirrels Glaucomys volans and Hylopetes sagitta show an extremely short transitional region. Likewise, several semifossorial taxa can be distinguished by their short distal region. Moreover, among flying squirrels, Petaurista petaurista shows differences with the small flying squirrels, mirroring previous observations on locomotory adaptations based on their inner ear morphometry. Our results show furthermore that the tail region proportions of P. petaurista, phylogenetically more basal than the small flying squirrels, are similar to those of bauplan-conservative arboreal squirrels.
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Affiliation(s)
- Rebecca Hofmann
- Abteilung Messelforschung und Mammalogie, Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, Frankfurt am Main, Germany.,Institut für Geowissenschaften, Goethe-Universität, Frankfurt am Main, Germany
| | - Thomas Lehmann
- Abteilung Messelforschung und Mammalogie, Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, Frankfurt am Main, Germany
| | - Dan L Warren
- Senckenberg Biodiversität und Klima Forschungszentrum, Frankfurt am Main, Germany.,Biodiversity and Biocomplexity Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Irina Ruf
- Abteilung Messelforschung und Mammalogie, Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, Frankfurt am Main, Germany.,Institut für Geowissenschaften, Goethe-Universität, Frankfurt am Main, Germany
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11
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Boonsri B, Nganvongpanit K, Buddhachat K, Punyapornwithaya V, Kongtueng P, Kaewmong P, Kittiwattanawong K. Morphometric analysis of cervical vertebrae in some marine and land mammals. Anat Histol Embryol 2021; 50:812-825. [PMID: 34272750 DOI: 10.1111/ahe.12725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 07/02/2021] [Accepted: 07/05/2021] [Indexed: 11/28/2022]
Abstract
Bones or skeletal remains can be used to answer a number of questions related to species, sex, age or cause of death. However, studies involving vertebrae have been limited as most were performed on skulls or long bones. Here, we have stated the hypothesis that the morphometry of cervical vertebrae can be used for species identification and body size estimation among marine and land mammals. The cervical vertebrae from eight and 14 species of marine and land mammals were used to collect morphometric data. Cluster dendrogram, principal component analysis, discriminant analysis and linear regression were used to analyse the data. The results indicate that, based on an index of C4 to C7, there were 13 out of 22 species for which identity could be correctly predicted in 100% of the cases. The correlations between cervical vertebrae parameters (height, width and length of centrum) in marine (average R2 = 0.87, p < .01) and land (average R2 = 0.51, p < .01) mammals were observed. These results indicate that vertebral morphometrics could be used for species prediction and verification of body weight in both marine and land mammals.
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Affiliation(s)
- Burin Boonsri
- Department of Companion Animals and Wildlife Clinics, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Korakot Nganvongpanit
- Department of Veterinary Biosciences and Public Health, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai, Thailand.,Excellence Center in Veterinary Bioscience, Chiang Mai University, Chiang Mai, Thailand
| | - Kittisak Buddhachat
- Excellence Center in Veterinary Bioscience, Chiang Mai University, Chiang Mai, Thailand.,Department of Biology, Faculty of Science, Naresuan University, Phitsanulok, Thailand
| | - Veerasak Punyapornwithaya
- Department of Food Animal Clinic, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Piyamat Kongtueng
- Central Laboratory, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai, Thailand
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12
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Abstract
The axial skeleton of all vertebrates is composed of individual units known as vertebrae. Each vertebra has individual anatomical attributes, yet they can be classified in five different groups, namely cervical, thoracic, lumbar, sacral and caudal, according to shared characteristics and their association with specific body areas. Variations in vertebral number, size, morphological features and their distribution amongst the different regions of the vertebral column are a major source of the anatomical diversity observed among vertebrates. In this review I will discuss the impact of those variations on the anatomy of different vertebrate species and provide insights into the genetic origin of some remarkable morphological traits that often serve to classify phylogenetic branches or individual species, like the long trunks of snakes or the long necks of giraffes.
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13
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Marek RD, Falkingham PL, Benson RBJ, Gardiner JD, Maddox TW, Bates KT. Evolutionary versatility of the avian neck. Proc Biol Sci 2021; 288:20203150. [PMID: 33653136 PMCID: PMC7934994 DOI: 10.1098/rspb.2020.3150] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Bird necks display unparalleled levels of morphological diversity compared to other vertebrates, yet it is unclear what factors have structured this variation. Using three-dimensional geometric morphometrics and multivariate statistics, we show that the avian cervical column is a hierarchical morpho-functional appendage, with varying magnitudes of ecologically driven osteological variation at different scales of organization. Contrary to expectations given the widely varying ecological functions of necks in different species, we find that regional modularity of the avian neck is highly conserved, with an overall structural blueprint that is significantly altered only by the most mechanically demanding ecological functions. Nevertheless, the morphologies of vertebrae within subregions of the neck show more prominent signals of adaptation to ecological pressures. We also find that both neck length allometry and the nature of neck elongation in birds are different from other vertebrates. In contrast with mammals, neck length scales isometrically with head mass and, contrary to previous work, we show that neck elongation in birds is achieved predominantly by increasing vertebral lengths rather than counts. Birds therefore possess a cervical spine that may be unique in its versatility among extant vertebrates, one that, since the origin of flight, has adapted to function as a surrogate forelimb in varied ecological niches.
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Affiliation(s)
- Ryan D Marek
- Department of Musculoskeletal & Ageing Science, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Peter L Falkingham
- Biological and Environmental Sciences, James Parsons Building, Byrom Street, Liverpool L3 3AF, UK
| | - Roger B J Benson
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - James D Gardiner
- Department of Musculoskeletal & Ageing Science, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Thomas W Maddox
- Department of Musculoskeletal & Ageing Science, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Karl T Bates
- Department of Musculoskeletal & Ageing Science, University of Liverpool, William Henry Duncan Building, 6 West Derby Street, Liverpool, L7 8TX, UK
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14
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Bjarnason A, Benson R. A 3D geometric morphometric dataset quantifying skeletal variation in birds. ACTA ACUST UNITED AC 2021. [DOI: 10.18563/journal.m3.125] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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15
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Müller MA, Merten LJF, Böhmer C, Nyakatura JA. Pushing the boundary? Testing the "functional elongation hypothesis" of the giraffe's neck. Evolution 2021; 75:641-655. [PMID: 33443310 DOI: 10.1111/evo.14171] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 01/07/2021] [Accepted: 01/08/2021] [Indexed: 11/28/2022]
Abstract
Although giraffes maintain the usual mammalian cervical number of seven vertebrae, their first thoracic vertebra (T1) exhibits aberrant anatomy and has been hypothesized to functionally elongate the neck. We test this "functional elongation hypothesis" by combining phylogenetically informed analyses of neck length, three-dimensional (3D) vertebral shape, and of the functional significance of shape differences across a broad sample of ruminants and camelids. Digital bone models of the cervicothoracic transition were subjected to 3D geometric morphometric analysis revealing how the shape of the seventh cervical (C7) has converged in several long-necked species. However, we find a unique "cervicalization" of the giraffe's T1. In contrast, we demonstrate a "thoracalization" of C7 for the European bison. Other giraffids (okapi and extinct Sivatherium) did not exhibit "cervicalized" T1 morphology. Quantitative range of motion (ROM) analysis at the cervicothoracic transition in ruminants and camelids confirms the "functional elongation hypothesis" for the giraffe in terms of increased mobility, especially with regard to dorsoventral flexion/extension. Additionally, other factors related to the unique morphology of the giraffe's cervicothoracic transition such as neck posture and intervertebral stability are discussed and should be considered in future studies of giraffe neck evolution.
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Affiliation(s)
- Marilena A Müller
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, 10115, Germany
| | - Luisa J F Merten
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, 10115, Germany
| | - Christine Böhmer
- UMR 7179 CNRS/MNHN, Département Adaptations du Vivant, Muséum National d'Histoire Naturelle, Paris, 75005, France.,Department für Geo- und Umweltwissenschaften und GeoBio-Center, Ludwig-Maximilians-Universität München, München, 80333, Germany
| | - John A Nyakatura
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, 10115, Germany
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16
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Evolution of the Mammalian Neck from Developmental, Morpho-Functional, and Paleontological Perspectives. J MAMM EVOL 2020. [DOI: 10.1007/s10914-020-09506-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
AbstractThe mammalian neck adopts a variety of postures during daily life and generates numerous head trajectories. Despite its functional diversity, the neck is constrained to seven cervical vertebrae in (almost) all mammals. Given this low number, an unexpectedly high degree of modularity of the mammalian neck has more recently been uncovered. This work aims to review neck modularity in mammals from a developmental, morpho-functional, and paleontological perspective and how high functional diversity evolved in the mammalian neck after the occurrence of meristic limitations. The fixed number of cervical vertebrae and the developmental modularity of the mammalian neck are closely linked to anterior Hox genes expression and strong developmental integration between the neck and other body regions. In addition, basic neck biomechanics promote morpho-functional modularity due to preferred motion axes in the cranio-cervical and cervico-thoracic junction. These developmental and biomechanical determinants result in the characteristic and highly conserved shape variation among the vertebrae that delimits morphological modules. The step-wise acquisition of these unique cervical traits can be traced in the fossil record. The increasing functional specialization of neck modules, however, did not evolve all at once but started much earlier in the upper than in the lower neck. Overall, the strongly conserved modularity in the mammalian neck represents an evolutionary trade-off between the meristic constraints and functional diversity. Although a morpho-functional partition of the neck is common among amniotes, the degree of modularity and the way neck disparity is realized is unique in mammals.
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17
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Mozaffari M, Jiang D, Tucker AS. Developmental aspects of the tympanic membrane: Shedding light on function and disease. Genesis 2019; 58:e23348. [PMID: 31763764 PMCID: PMC7154630 DOI: 10.1002/dvg.23348] [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] [Received: 10/23/2019] [Revised: 11/13/2019] [Accepted: 11/14/2019] [Indexed: 12/19/2022]
Abstract
The ear drum, or tympanic membrane (TM), is a key component in the intricate relay that transmits air-borne sound to our fluid-filled inner ear. Despite early belief that the mammalian ear drum evolved as a transformation of a reptilian drum, newer fossil data suggests a parallel and independent evolution of this structure in mammals. The term "drum" belies what is in fact a complex three-dimensional structure formed from multiple embryonic cell lineages. Intriguingly, disease affects the ear drum differently in its different parts, with the superior and posterior parts being much more frequently affected. This suggests a key role for the developmental details of TM formation in its final form and function, both in homeostasis and regeneration. Here we review recent studies in rodent models and humans that are beginning to address large knowledge gaps in TM cell dynamics from a developmental biologist's point of view. We outline the biological and clinical uncertainties that remain, with a view to guiding the indispensable contribution that developmental biology will be able to make to better understanding the TM.
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Affiliation(s)
- Mona Mozaffari
- Centre for Craniofacial and Regenerative Biology, King's College London, Guy's Hospital, London, UK
| | - Dan Jiang
- Centre for Craniofacial and Regenerative Biology, King's College London, Guy's Hospital, London, UK.,ENT Department, Guy's Hospital, London, UK
| | - Abigail S Tucker
- Centre for Craniofacial and Regenerative Biology, King's College London, Guy's Hospital, London, UK
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18
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Vander Linden A, Dumont ER. Intraspecific male combat behaviour predicts morphology of cervical vertebrae in ruminant mammals. Proc Biol Sci 2019; 286:20192199. [PMID: 31718495 DOI: 10.1098/rspb.2019.2199] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Cranial weapons of all shapes and sizes are common throughout the animal kingdom and are frequently accompanied by the evolution of additional traits that enhance the use of those weapons. Bovids (cattle, sheep, goats, antelope) and cervids (deer) within the mammal clade Ruminantia are particularly well known for their distinct and varied cranial appendages in the form of horns and antlers, which are used as weapons in intraspecific combat between males for access to mates. Combat in these species takes many forms, including head-on collisions (ramming); stabbing an opponent's head or body with horn tips (stabbing); rearing and clashing downwards with horns (fencing); or interlocking antlers or horns while vigorously pushing and twisting (wrestling). Some aspects of weapon and skull morphology have been linked to combat behaviours in bovid and cervid species, but the contribution of postcranial structures that support these weapons, such as the neck, has not been explored. To investigate the role of the neck in intraspecific combat, we quantified biomechanically relevant linear variables of the cervical vertebrae (C1-C7) from males and females of 55 ruminant species. We then used phylogenetic generalized least-squares regression to assess differences among species that display primarily ramming, stabbing, fencing and wrestling combat styles. In males, we found that wrestlers have longer vertebral centra and longer neural spines than rammers, stabbers or fencers, while rammers have shorter and wider centra and taller neural spine lever arms. These results suggest a supportive role for the cervical vertebrae in resisting forces generated by male-male combat in ruminant mammals and indicate that evolutionary forces influencing cranial weapons also play a role in shaping the supporting anatomical structures.
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Affiliation(s)
- Abby Vander Linden
- Organismic and Evolutionary Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Elizabeth R Dumont
- School of Natural Sciences, University of California Merced, Merced, CA, USA
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19
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Vander Linden A, Campbell KM, Bryar EK, Santana SE. Head‐turning morphologies: Evolution of shape diversity in the mammalian atlas–axis complex. Evolution 2019; 73:2060-2071. [DOI: 10.1111/evo.13815] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 07/01/2019] [Indexed: 01/24/2023]
Affiliation(s)
- Abby Vander Linden
- Graduate Program in Organismic and Evolutionary Biology University of Massachusetts Amherst Amherst Massachusetts
| | | | - Erin K. Bryar
- Department of Biology University of Washington Seattle Washington
| | - Sharlene E. Santana
- Department of Biology University of Washington Seattle Washington
- Burke Museum of Natural History and Culture Seattle Washington
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20
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Böhmer C, Plateau O, Cornette R, Abourachid A. Correlated evolution of neck length and leg length in birds. ROYAL SOCIETY OPEN SCIENCE 2019; 6:181588. [PMID: 31218020 PMCID: PMC6549945 DOI: 10.1098/rsos.181588] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 04/08/2019] [Indexed: 06/09/2023]
Abstract
Despite a diversity of about 10 000 extant species, the sophisticated avian 'body plan' has not much changed once it was achieved around 160 Ma after the origin of powered flight. All birds are bipedal having wings, a rigid trunk, a short and ossified tail, a three-segmented leg and digitigrade feet. The avian neck, however, has always been regarded as a classic example of high variability ranging from short necks in songbirds to extremely long, serpentine necks in herons. Yet, the wide array of small to very large species makes it difficult to evaluate the actual neck length. Here, we investigate the evolution of the vertebral formulae in the neck of birds and the scaling relationships between skeletal dimensions and body size. Cervical count in birds is strongly related to phylogeny, with only some specialists having an exceptional number of vertebrae in the neck. In contrast with mammals, the length of the cervical vertebral column increases as body size increases and, thus, body size does not constrain neck length in birds. Indeed, neck length scales isometrically with total leg length suggesting a correlated evolution between both modules. The strong integration between the cervical and pelvic module in birds is in contrast with the decoupling of the fore- and hindlimb module and may be the result of the loss of a functionally versatile forelimb due to the evolution of powered flight.
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Affiliation(s)
- Christine Böhmer
- UMR 7179 CNRS/MNHN, Département Adaptations du Vivant, Muséum National d'Histoire Naturelle, 55 rue Buffon, 75005 Paris, France
| | - Olivia Plateau
- UMR 7179 CNRS/MNHN, Département Adaptations du Vivant, Muséum National d'Histoire Naturelle, 55 rue Buffon, 75005 Paris, France
| | - Raphäel Cornette
- UMR 7205 Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d'Histoire Naturelle, CNRS, Sorbonne Université, EPHE, CP 50, 57 rue Cuvier, 75005 Paris, France
| | - Anick Abourachid
- UMR 7179 CNRS/MNHN, Département Adaptations du Vivant, Muséum National d'Histoire Naturelle, 55 rue Buffon, 75005 Paris, France
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21
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Sherratt E, Coutts FJ, Rasmussen AR, Sanders KL. Vertebral evolution and ontogenetic allometry: The developmental basis of extreme body shape divergence in microcephalic sea snakes. Evol Dev 2019; 21:135-144. [DOI: 10.1111/ede.12284] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 02/04/2019] [Accepted: 02/05/2019] [Indexed: 12/25/2022]
Affiliation(s)
- Emma Sherratt
- Department of Ecology and Evolutionary Biology School of Biological Sciences, The University of Adelaide Adelaide South Australia Australia
| | - Felicity J. Coutts
- Department of Ecology and Evolutionary Biology School of Biological Sciences, The University of Adelaide Adelaide South Australia Australia
- Earth Sciences Section, South Australian Museum Adelaide South Australia Australia
| | - Arne R. Rasmussen
- The Royal Danish Academy of Fine Arts, Schools of Architecture, Design and Conservation Copenhagen Denmark
| | - Kate L. Sanders
- Department of Ecology and Evolutionary Biology School of Biological Sciences, The University of Adelaide Adelaide South Australia Australia
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22
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Bergmann PJ, Morinaga G. The convergent evolution of snake‐like forms by divergent evolutionary pathways in squamate reptiles*. Evolution 2018; 73:481-496. [DOI: 10.1111/evo.13651] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 11/08/2018] [Indexed: 12/15/2022]
Affiliation(s)
- Philip J. Bergmann
- Department of Biology Clark University 950 Main Street Worcester Massachusetts 01610
| | - Gen Morinaga
- Department of Biology Clark University 950 Main Street Worcester Massachusetts 01610
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23
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Montañez‐Rivera I, Nyakatura JA, Amson E. Bone cortical compactness in 'tree sloths' reflects convergent evolution. J Anat 2018; 233:580-591. [PMID: 30117161 PMCID: PMC6183012 DOI: 10.1111/joa.12873] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2018] [Indexed: 01/15/2023] Open
Abstract
Bone remodeling, one of the main processes that regulate bone microstructure, consists of bone resorption followed by the deposition of secondary bone at the same location. Remodeling intensity varies among taxa, but a characteristically compact cortex is ubiquitous in the long bones of mature terrestrial mammals. A previous analysis found that cortical bone in a few 'tree sloth' (Bradypus and Choloepus) specimens is heavily remodeled and characterized by numerous immature secondary osteons, suggesting that these animals were remodeling their bones at high rate until late in their ontogeny. This study aims at testing if this remodeling is generally present in 'tree sloths', using a quantitative analysis of the humeral cortical compactness (CC) among xenarthrans. The results of the investigation of humeral diaphyseal cross-sections of 26 specimens belonging to 10 xenarthran species including specimens from both extinct and extant species indicate that in 'tree sloths' the CC is significantly lower than in the other sampled xenarthrans. No significant difference was found between the CC of the two genera of 'tree sloths'. Our results are consistent with the hypothesis that the cortical bone of 'tree sloths' in general undergoes intense and balanced remodeling that is maintained until late (possibly throughout) in their ontogeny. In the light of xenarthran phylogeny, low CC represents another convergence between the long-separated 'tree sloth' lineages. Although the exact structural and/or functional demands that are associated with this trait are hitherto unknown, several hypotheses are suggested here, including a relationship to their relatively low metabolism and to the mechanical demands imposed upon the bones by the suspensory posture and locomotion, which was independently acquired by the two genera of 'tree sloths'.
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Affiliation(s)
- Irene Montañez‐Rivera
- AG Morphologie und FormengeschichteInstitut für BiologieHumboldt UniversitätBerlinGermany
| | - John A. Nyakatura
- AG Morphologie und FormengeschichteInstitut für BiologieHumboldt UniversitätBerlinGermany
- Bild Wissen Gestaltung. Ein interdisziplinäres LaborHumboldt UniversitätBerlinGermany
| | - Eli Amson
- AG Morphologie und FormengeschichteInstitut für BiologieHumboldt UniversitätBerlinGermany
- Bild Wissen Gestaltung. Ein interdisziplinäres LaborHumboldt UniversitätBerlinGermany
- Museum für NaturkundeLeibniz‐Institut für Evolutions‐ und BiodiversitätsforschungBerlinGermany
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24
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Böhmer C, Amson E, Arnold P, van Heteren AH, Nyakatura JA. Homeotic transformations reflect departure from the mammalian 'rule of seven' cervical vertebrae in sloths: inferences on the Hox code and morphological modularity of the mammalian neck. BMC Evol Biol 2018; 18:84. [PMID: 29879896 PMCID: PMC5992679 DOI: 10.1186/s12862-018-1202-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 05/23/2018] [Indexed: 11/10/2022] Open
Abstract
Background Sloths are one of only two exceptions to the mammalian ‘rule of seven’ vertebrae in the neck. As a striking case of breaking the evolutionary constraint, the explanation for the exceptional number of cervical vertebrae in sloths is still under debate. Two diverging hypotheses, both ultimately linked to the low metabolic rate of sloths, have been proposed: hypothesis 1 involves morphological transformation of vertebrae due to changes in the Hox gene expression pattern and hypothesis 2 assumes that the Hox gene expression pattern is not altered and the identity of the vertebrae is not changed. Direct evidence supporting either hypothesis would involve knowledge of the vertebral Hox code in sloths, but the realization of such studies is extremely limited. Here, on the basis of the previously established correlation between anterior Hox gene expression and the quantifiable vertebral shape, we present the morphological regionalization of the neck in three different species of sloths with aberrant cervical count providing indirect insight into the vertebral Hox code. Results Shape differences within the cervical vertebral column suggest a mouse-like Hox code in the neck of sloths. We infer an anterior shift of HoxC-6 expression in association with the first thoracic vertebra in short-necked sloths with decreased cervical count, and a posterior shift of HoxC-5 and HoxC-6 expression in long-necked sloths with increased cervical count. Conclusion Although only future developmental analyses in non-model organisms, such as sloths, will yield direct evidence for the evolutionary mechanism responsible for the aberrant number of cervical vertebrae, our observations lend support to hypothesis 1 indicating that the number of modules is retained but their boundaries are displaced. Our approach based on quantified morphological differences also provides a reliable basis for further research including fossil taxa such as extinct ‘ground sloths’ in order to trace the pattern and the underlying genetic mechanisms in the evolution of the vertebral column in mammals. Electronic supplementary material The online version of this article (10.1186/s12862-018-1202-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Christine Böhmer
- UMR 7179 CNRS/MNHN, Muséum National d'Histoire Naturelle, 57 rue Cuvier, CP-55, Paris, France.
| | - Eli Amson
- AG Morphologie und Formengeschichte, Institut für Biologie, Humboldt Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany.,Image Knowledge Gestaltung: An Interdisciplinary Laboratory, Humboldt University, Philippstraße 13, 10115, Berlin, Germany.,Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115, Berlin, Germany
| | - Patrick Arnold
- Institut für Zoologie und Evolutionsforschung mit Phyletischem Museum, Ernst-Haeckel-Haus und Biologiedidaktik, Friedrich-Schiller-Universität Jena, Erbertstraße 1, 07743, Jena, Germany.,Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103, Leipzig, Germany
| | - Anneke H van Heteren
- Sektion Mammalogie, SNSB - Zoologische Staatssammlung, Münchhausenstraße 21, 81247, München, Germany.,GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Straße 10, 80333, Munich, Germany.,Department Biologie II, Ludwig-Maximilians-Universität München, Großhaderner Straße 2, 82152, Planegg-Martinsried, Germany
| | - John A Nyakatura
- AG Morphologie und Formengeschichte, Institut für Biologie, Humboldt Universität zu Berlin, Philippstraße 13, 10115, Berlin, Germany.,Image Knowledge Gestaltung: An Interdisciplinary Laboratory, Humboldt University, Philippstraße 13, 10115, Berlin, Germany
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25
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Powell GL, Russell AP, Sutey J. Patterns of growth in the presacral vertebral column of the leopard gecko (Eublepharis macularius). J Morphol 2018; 279:1088-1103. [PMID: 29732599 DOI: 10.1002/jmor.20833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 03/06/2018] [Accepted: 04/08/2018] [Indexed: 11/10/2022]
Abstract
Postnatal growth patterns within the vertebral column may be informative about body proportions and regionalization. We measured femur length, lengths of all pre-sacral vertebrae, and lengths of intervertebral spaces, from radiographs of a series of 21 Eublepharis macularius, raised under standard conditions and covering most of the ontogenetic body size range. Vertebrae were grouped into cervical, sternal, and dorsal compartments, and lengths of adjacent pairs of vertebrae were summed before analysis. Femur length was included as an index of body size. Principal component analysis of the variance-covariance matrix of these data was used to investigate scaling among them. PC1 explained 94.19% of total variance, interpreted as the variance due to body size. PC1 differed significantly from the hypothetical isometric vector, indicating overall allometry. The atlas and axis vertebrae displayed strong negative allometry; the remainder of the vertebral pairs exhibited weak negative allometry, isometry or positive allometry. PC1 explained a markedly smaller amount of variance for the vertebral pairs of the cervical compartment than for the remainder of the vertebral pairs, with the exception of the final pair. The relative standard deviations of the eigenvalues from the PCAs of the three vertebral compartments indicated that the vertebrae of the cervical compartment were less strongly integrated by scaling than were the sternal or dorsal vertebrae, which did not differ greatly between themselves in their strong integration, suggesting that the growth of the cervical vertebrae is constrained by the mechanical requirements of the head. Regionalization of the remainder of the vertebral column is less clearly defined but may be associated with wave form propagation incident upon locomotion, and by locomotory changes occasioned by tail autotomy and regeneration. Femur length exhibits negative allometry relative to individual vertebral pairs and to vertebral column length, suggesting a change in locomotor requirements over the ontogenetic size range.
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Affiliation(s)
| | - Anthony P Russell
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Jennifer Sutey
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
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26
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Villamil CI. Phenotypic integration of the cervical vertebrae in the Hominoidea (Primates). Evolution 2018; 72:490-517. [DOI: 10.1111/evo.13433] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 01/11/2018] [Accepted: 01/12/2018] [Indexed: 12/30/2022]
Affiliation(s)
- Catalina I. Villamil
- Department of Anthropology; Dickinson College; P.O. Box 1773 Carlisle Pennsylvania 17013
- Center for the Study of Human Origins, Department of Anthropology; New York University; 25 Waverly Place New York New York 10003
- New York Consortium in Evolutionary Primatology; New York New York 10024
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27
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Arnold P, Esteve-Altava B, Fischer MS. Musculoskeletal networks reveal topological disparity in mammalian neck evolution. BMC Evol Biol 2017; 17:251. [PMID: 29237396 PMCID: PMC5729486 DOI: 10.1186/s12862-017-1101-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 11/30/2017] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The increase in locomotor and metabolic performance during mammalian evolution was accompanied by the limitation of the number of cervical vertebrae to only seven. In turn, nuchal muscles underwent a reorganization while forelimb muscles expanded into the neck region. As variation in the cervical spine is low, the variation in the arrangement of the neck muscles and their attachment sites (i.e., the variability of the neck's musculoskeletal organization) is thus proposed to be an important source of neck disparity across mammals. Anatomical network analysis provides a novel framework to study the organization of the anatomical arrangement, or connectivity pattern, of the bones and muscles that constitute the mammalian neck in an evolutionary context. RESULTS Neck organization in mammals is characterized by a combination of conserved and highly variable network properties. We uncovered a conserved regionalization of the musculoskeletal organization of the neck into upper, mid and lower cervical modules. In contrast, there is a varying degree of complexity or specialization and of the integration of the pectoral elements. The musculoskeletal organization of the monotreme neck is distinctively different from that of therian mammals. CONCLUSIONS Our findings reveal that the limited number of vertebrae in the mammalian neck does not result in a low musculoskeletal disparity when examined in an evolutionary context. However, this disparity evolved late in mammalian history in parallel with the radiation of certain lineages (e.g., cetartiodactyls, xenarthrans). Disparity is further facilitated by the enhanced incorporation of forelimb muscles into the neck and their variability in attachment sites.
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Affiliation(s)
- Patrick Arnold
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Borja Esteve-Altava
- Structure & Motion Lab, Department of Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK
| | - Martin S. Fischer
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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