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Kuroda S, Lalonde RL, Mansour TA, Mosimann C, Nakamura T. Multiple embryonic sources converge to form the pectoral girdle skeleton in zebrafish. Nat Commun 2024; 15:6313. [PMID: 39060278 PMCID: PMC11282072 DOI: 10.1038/s41467-024-50734-x] [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: 07/27/2023] [Accepted: 07/19/2024] [Indexed: 07/28/2024] Open
Abstract
The morphological transformation of the pectoral/shoulder girdle is fundamental to the water-to-land transition in vertebrate evolution. Although previous studies have resolved the embryonic origins of tetrapod shoulder girdles, those of fish pectoral girdles remain uncharacterized, creating a gap in the understanding of girdle transformation mechanisms from fish to tetrapods. Here, we identify the embryonic origins of the zebrafish pectoral girdle, including the cleithrum as an ancestral girdle element lost in extant tetrapods. Our combinatorial approach of photoconversion and genetic lineage tracing demonstrates that cleithrum development combines four adjoining embryonic populations. A comparison of these pectoral girdle progenitors with extinct and extant vertebrates highlights that cleithrum loss, indispensable for neck evolution, is associated with the disappearance of its unique developmental environment at the head/trunk interface. Overall, our study establishes an embryological framework for pectoral/shoulder girdle formation and provides evolutionary trajectories from their origin in water to diversification on land.
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Affiliation(s)
- Shunya Kuroda
- Department of Genetics, Rutgers the State University of New Jersey, Piscataway, NJ, 08854, USA.
- Institute for Frontier Science Initiative, Kanazawa University, Kakuma-machi, Kanazawa, 920-1164, Japan.
| | - Robert L Lalonde
- Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, USA
| | - Thomas A Mansour
- Department of Genetics, Rutgers the State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Christian Mosimann
- Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, USA
| | - Tetsuya Nakamura
- Department of Genetics, Rutgers the State University of New Jersey, Piscataway, NJ, 08854, USA.
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2
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Figueroa RT, Weinschütz LC, Giles S, Friedman M. Soft-tissue fossilization illuminates the stepwise evolution of the ray-finned fish brain. Curr Biol 2024; 34:2831-2840.e2. [PMID: 38866006 DOI: 10.1016/j.cub.2024.05.027] [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: 02/06/2024] [Revised: 04/12/2024] [Accepted: 05/14/2024] [Indexed: 06/14/2024]
Abstract
A complex brain is central to the success of backboned animals. However, direct evidence bearing on vertebrate brain evolution comes almost exclusively from extant species, leaving substantial knowledge gaps. Although rare, soft-tissue preservation in fossils can yield unique insights on patterns of neuroanatomical evolution. Paleontological evidence from an exceptionally preserved Pennsylvanian (∼318 Ma) actinopterygian, Coccocephalus, calls into question prior interpretations of ancestral actinopterygian brain conditions. However, the ordering and timing of major evolutionary innovations, such as an everted telencephalon, modified meningeal tissues, and hypothalamic inferior lobes, remain unclear. Here, we report two distinct actinopterygian morphotypes from the latest Carboniferous-earliest Permian (∼299 Ma) of Brazil that show extensive soft-tissue preservation of brains, cranial nerves, eyes, and potential cardiovascular tissues. These fossils corroborate inferences drawn from ✝Coccocephalus, while adding new information about neuroanatomical evolution. Skeletal features indicate that one of these Brazilian morphotypes is more closely related to living actinopterygians than the other, which is also reflected in soft-tissue features. Significantly, the more crownward morphotype shows a key neuroanatomical feature of extant actinopterygians-an everted telencephalon-that is absent in the other morphotype and ✝Coccocephalus. All preserved Paleozoic actinopterygian brains show broad similarities, including an invaginated cerebellum, hypothalamus inferior lobes, and a small forebrain. In each case, preserved brains are substantially smaller than the enclosing cranial chamber. The neuroanatomical similarities shared by this grade of Permo-Carboniferous actinopterygians reflect probable primitive conditions for actinopterygians, providing a revised model for interpreting brain evolution in a major branch of the vertebrate tree of life.
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Affiliation(s)
- Rodrigo T Figueroa
- Department of Earth and Environmental Sciences, University of Michigan, North University Building, 1100 North University Avenue, Ann Arbor, MI 48109, USA; Museum of Paleontology, University of Michigan, Biological Sciences Building, 1105 North University Avenue, Ann Arbor, MI 48109, USA.
| | - Luiz Carlos Weinschütz
- Centro Paleontologico da Universidade do Contestado, CENPALEO, Av. Presidente Nereu Ramos 1071, Jardim Moinho, Mafra 89806-076, Santa Catarina, Brazil
| | - Sam Giles
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Matt Friedman
- Department of Earth and Environmental Sciences, University of Michigan, North University Building, 1100 North University Avenue, Ann Arbor, MI 48109, USA; Museum of Paleontology, University of Michigan, Biological Sciences Building, 1105 North University Avenue, Ann Arbor, MI 48109, USA
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3
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Cummins M, Watson C, Edwards RJ, Mattick JS. The Evolution of Ultraconserved Elements in Vertebrates. Mol Biol Evol 2024; 41:msae146. [PMID: 39058500 PMCID: PMC11276968 DOI: 10.1093/molbev/msae146] [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: 03/26/2024] [Revised: 06/29/2024] [Accepted: 07/08/2024] [Indexed: 07/18/2024] Open
Abstract
Ultraconserved elements were discovered two decades ago, arbitrarily defined as sequences that are identical over a length ≥ 200 bp in the human, mouse, and rat genomes. The definition was subsequently extended to sequences ≥ 100 bp identical in at least three of five mammalian genomes (including dog and cow), and shown to have undergone rapid expansion from ancestors in fish and strong negative selection in birds and mammals. Since then, many more genomes have become available, allowing better definition and more thorough examination of ultraconserved element distribution and evolutionary history. We developed a fast and flexible analytical pipeline for identifying ultraconserved elements in multiple genomes, dedUCE, which allows manipulation of minimum length, sequence identity, and number of species with a detectable ultraconserved element according to specified parameters. We suggest an updated definition of ultraconserved elements as sequences ≥ 100 bp and ≥97% sequence identity in ≥50% of placental mammal orders (12,813 ultraconserved elements). By mapping ultraconserved elements to ∼200 species, we find that placental ultraconserved elements appeared early in vertebrate evolution, well before land colonization, suggesting that the evolutionary pressures driving ultraconserved element selection were present in aquatic environments in the Cambrian-Devonian periods. Most (>90%) ultraconserved elements likely appeared after the divergence of gnathostomes from jawless predecessors, were largely established in sequence identity by early Sarcopterygii evolution-before the divergence of lobe-finned fishes from tetrapods-and became near fixed in the amniotes. Ultraconserved elements are mainly located in the introns of protein-coding and noncoding genes involved in neurological and skeletomuscular development, enriched in regulatory elements, and dynamically expressed throughout embryonic development.
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Affiliation(s)
- Mitchell Cummins
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Cadel Watson
- School of Engineering, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Richard J Edwards
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - John S Mattick
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
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4
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Werneburg I, Hoßfeld U, Levit GS. Darwin, Haeckel, and the "Mikluskan gas organ theory". Dev Dyn 2024; 253:370-389. [PMID: 37837337 DOI: 10.1002/dvdy.661] [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: 05/10/2023] [Revised: 09/20/2023] [Accepted: 09/20/2023] [Indexed: 10/16/2023] Open
Abstract
A previously unknown reference to the Russian ethnologist, biologist, and traveler Nikolai N. Miklucho-Maclay (1846-1888) was discovered in correspondence between Charles Darwin (1809-1882) and Ernst Haeckel (1834-1919). This reference has remained unknown to science, even to Miklucho-Maclay's biographers, probably because Darwin used the Russian nickname "Mikluska" when alluding to this young scientist. Here, we briefly outline the story behind the short discussion between Darwin and his German counterpart Haeckel, and highlight its importance for the history of science. Miklucho-Maclay's discovery of a putative swim bladder anlage in sharks, published in 1867, was discussed in four letters between the great biologists. Whereas, Haeckel showed enthusiasm for the finding because it supported (his view on) evolutionary theory, Darwin was less interested, which highlights the conceptual differences between the two authorities. We discuss the scientific treatment of Miklucho-Maclay's observation in the literature and discuss the homology, origin, and destiny of gas organs-swim bladders and lungs-in vertebrate evolution, from an ontogenetic point of view. We show that the conclusions reached by Miklucho-Maclay and Haeckel were rather exaggerated, although they gave rise to fundamental insights, and we illustrate how tree-thinking may lead to differences in the conceptualization of evolutionary change.
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Affiliation(s)
- Ingmar Werneburg
- Paläontologische Sammlung, Fachbereich Geowissenschaften der Universität Tübingen, Tübingen, Germany
- Senckenberg Center for Human Evolution and Palaeoenvironment an der Universität Tübingen, Tübingen, Germany
| | - Uwe Hoßfeld
- Arbeitsgruppe Biologiedidaktik, Institut für Zoologie und Evolutionsforschung, Fakultät für Biowissenschaften, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Georgy S Levit
- Arbeitsgruppe Biologiedidaktik, Institut für Zoologie und Evolutionsforschung, Fakultät für Biowissenschaften, Friedrich-Schiller-Universität Jena, Jena, Germany
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5
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Long JA, Trinajstic K. Placoderms. Curr Biol 2024; 34:R43-R47. [PMID: 38262353 DOI: 10.1016/j.cub.2023.11.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
For over 70 million years, during the Paleozoic, the placoderms (Greek for 'plated skin'), an extinct group of armoured fishes, were the most abundant and diverse vertebrates on our planet. Some of the first placoderm fossils discovered - such as Bothriolepis with its bone-covered pectoral fins - seemed so bizarre that they were thought to represent turtles or ancient beetles. All placoderms bear thick overlapping dermal plates around the head (called the 'head shield') and an area of the body covered in similar overlapping plates enveloping the pectoral to anal region (called the 'trunk-shield'). Placoderm fossils (Figure 1) are known from every continent on Earth ranging from the early Silurian (∼438 million years ago) to the end Devonian (∼359 million years ago) when they became extinct.
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Affiliation(s)
- John A Long
- School of Biological Sciences, Flinders University, Adelaide, SA 2100, Australia.
| | - Kate Trinajstic
- School of Molecular and Life Sciences, Curtin University, Bentley, WA 6076, Australia
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6
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Dhami NK, Greenwood PF, Poropat SF, Tripp M, Elson A, Vijay H, Brosnan L, Holman AI, Campbell M, Hopper P, Smith L, Jian A, Grice K. Microbially mediated fossil concretions and their characterization by the latest methodologies: a review. Front Microbiol 2023; 14:1225411. [PMID: 37840715 PMCID: PMC10576451 DOI: 10.3389/fmicb.2023.1225411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 08/14/2023] [Indexed: 10/17/2023] Open
Abstract
The study of well-preserved organic matter (OM) within mineral concretions has provided key insights into depositional and environmental conditions in deep time. Concretions of varied compositions, including carbonate, phosphate, and iron-based minerals, have been found to host exceptionally preserved fossils. Organic geochemical characterization of concretion-encapsulated OM promises valuable new information of fossil preservation, paleoenvironments, and even direct taxonomic information to further illuminate the evolutionary dynamics of our planet and its biota. Full exploitation of this largely untapped geochemical archive, however, requires a sophisticated understanding of the prevalence, formation controls and OM sequestration properties of mineral concretions. Past research has led to the proposal of different models of concretion formation and OM preservation. Nevertheless, the formation mechanisms and controls on OM preservation in concretions remain poorly understood. Here we provide a detailed review of the main types of concretions and formation pathways with a focus on the role of microbes and their metabolic activities. In addition, we provide a comprehensive account of organic geochemical, and complimentary inorganic geochemical, morphological, microbial and paleontological, analytical methods, including recent advancements, relevant to the characterization of concretions and sequestered OM. The application and outcome of several early organic geochemical studies of concretion-impregnated OM are included to demonstrate how this underexploited geo-biological record can provide new insights into the Earth's evolutionary record. This paper also attempts to shed light on the current status of this research and major challenges that lie ahead in the further application of geo-paleo-microbial and organic geochemical research of concretions and their host fossils. Recent efforts to bridge the knowledge and communication gaps in this multidisciplinary research area are also discussed, with particular emphasis on research with significance for interpreting the molecular record in extraordinarily preserved fossils.
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Affiliation(s)
- Navdeep K. Dhami
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Paul F. Greenwood
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Stephen F. Poropat
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Madison Tripp
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Amy Elson
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Hridya Vijay
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Luke Brosnan
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Alex I. Holman
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Matthew Campbell
- The Trace and Environmental DNA lab (trEND), School of Molecular and Life Sciences, Curtin University, Perth, WA, Australia
| | - Peter Hopper
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Lisa Smith
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Andrew Jian
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
| | - Kliti Grice
- Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA, Australia
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7
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Jensen B, Moorman AFM, Wang T, Møller PR, Icardo JM, Lauridsen H. Comment on "Exceptional preservation of organs in Devonian placoderms from the Gogo lagerstätte". Science 2023; 380:eadg2748. [PMID: 37167376 DOI: 10.1126/science.adg2748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Trinajstic et al., (Science, 16 September 2022, p. 1311-1314) describe exceptionally well-preserved organs in fossilized Devonian placoderms to infer the early evolution of the vertebrate heart. We argue that the report has numerous shortcomings and examples of mixed specimen codes. Further, we question whether there indeed is any evidence for a mineralized chambered heart in these placoderms.
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Affiliation(s)
- Bjarke Jensen
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centres, Amsterdam, The Netherlands
| | - Antoon Fransiscus Maria Moorman
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centres, Amsterdam, The Netherlands
| | - Tobias Wang
- Department of Biology, Zoophysiology, Aarhus University, Aarhus, Denmark
| | - Peter Rask Møller
- Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
- Norwegian College of Fishery Science, UiT - The Arctic University of Norway, Tromsø, Norway
| | - José Manuel Icardo
- Department of Anatomy and Cell Biology, University of Cantabria, Santander, Spain
| | - Henrik Lauridsen
- Department of Clinical Medicine, Aarhus University, Aarhus N, Denmark
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8
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Trinajstic K, Long J, Sanchez S, Boisvert CA, Snitting D, Tafforeau P, Dupret V, Clement AM, Currie PD, Roelofs B, Bevitt JJ, Lee MSY, Ahlberg PE. Response to comment on "Exceptional preservation of organs in Devonian placoderms from the Gogo largerstätte". Science 2023; 380:eadg3748. [PMID: 37167391 DOI: 10.1126/science.adg3748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Jensen et al. (1) question evidence presented of a chambered heart within placoderms, citing its small size and apparently ventral atrium. However, they fail to note the belly-up orientation of the placoderm within one nodule, and the variability of heart morphology within extant taxa. Thus, we remain confident in our interpretation of the mineralized organ as the heart.
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Affiliation(s)
- Kate Trinajstic
- School of Molecular and Life Sciences, Curtin University, Kent Street, Bentley, 6102, WA, Australia
- Western Australian Museum, 49 Kew Street, Welshpool, 6106, Western Australia, Australia
| | - John Long
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide 5001, South Australia, Australia
- Museum Victoria, PO Box 666, Melbourne, Victoria, Australia 3001
| | - Sophie Sanchez
- Department of Organismal Biology, Evolutionary Biology Center, Uppsala University, Norbyvägen 18A, 75236 Uppsala, Sweden
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Catherine A Boisvert
- School of Molecular and Life Sciences, Curtin University, Kent Street, Bentley, 6102, WA, Australia
| | - Daniel Snitting
- Department of Organismal Biology, Evolutionary Biology Center, Uppsala University, Norbyvägen 18A, 75236 Uppsala, Sweden
| | - Paul Tafforeau
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Vincent Dupret
- Department of Organismal Biology, Evolutionary Biology Center, Uppsala University, Norbyvägen 18A, 75236 Uppsala, Sweden
| | - Alice M Clement
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide 5001, South Australia, Australia
| | - Peter D Currie
- Australian Regenerative Medicine Institute and EMBL Australia Building, Monash University, Clayton, 3800, Victoria, Australia
| | - Brett Roelofs
- School of Molecular and Life Sciences, Curtin University, Kent Street, Bentley, 6102, WA, Australia
| | - Joseph J Bevitt
- Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, 2234, New South Wales, Australia
| | - Michael S Y Lee
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide 5001, South Australia, Australia
- Earth Sciences Section, South Australian Museum, Adelaide, 5000, South Australia
| | - Per E Ahlberg
- Department of Organismal Biology, Evolutionary Biology Center, Uppsala University, Norbyvägen 18A, 75236 Uppsala, Sweden
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9
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Dutel H, Fabbri M. Fish fossil unfolds clues to vertebrate brain evolution. Nature 2023; 614:422-423. [PMID: 36725939 DOI: 10.1038/d41586-023-00243-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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10
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Exceptional fossil preservation and evolution of the ray-finned fish brain. Nature 2023; 614:486-491. [PMID: 36725931 DOI: 10.1038/s41586-022-05666-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Accepted: 12/16/2022] [Indexed: 02/03/2023]
Abstract
Brain anatomy provides key evidence for the relationships between ray-finned fishes1, but two major limitations obscure our understanding of neuroanatomical evolution in this major vertebrate group. First, the deepest branching living lineages are separated from the group's common ancestor by hundreds of millions of years, with indications that aspects of their brain morphology-like other aspects of their anatomy2,3-are specialized relative to primitive conditions. Second, there are no direct constraints on brain morphology in the earliest ray-finned fishes beyond the coarse picture provided by cranial endocasts: natural or virtual infillings of void spaces within the skull4-8. Here we report brain and cranial nerve soft-tissue preservation in Coccocephalus wildi, an approximately 319-million-year-old ray-finned fish. This example of a well-preserved vertebrate brain provides a window into neural anatomy deep within ray-finned fish phylogeny. Coccocephalus indicates a more complicated pattern of brain evolution than suggested by living species alone, highlighting cladistian apomorphies1 and providing temporal constraints on the origin of traits uniting all extant ray-finned fishes1,9. Our findings, along with a growing set of studies in other animal groups10-12, point to the importance of ancient soft tissue preservation in understanding the deep evolutionary assembly of major anatomical systems outside of the narrow subset of skeletal tissues13-15.
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11
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Engelman R. Giant, swimming mouths: oral dimensions of extant sharks do not accurately predict body size in Dunkleosteus terrelli (Placodermi: Arthrodira). PeerJ 2023; 11:e15131. [PMID: 37065696 PMCID: PMC10100833 DOI: 10.7717/peerj.15131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 03/06/2023] [Indexed: 04/18/2023] Open
Abstract
Background The size of Dunkleosteus and other late Devonian arthrodire placoderms has been a persistent problem in paleontology. The bony head and thoracic armor of these animals are typically the only elements preserved in the fossil record, with the rest of the body being lost during fossilization. Accurate length estimates of arthrodires are critical for reconstructing the paleobiology of these taxa and Devonian paleoecology more generally. Lengths of 5.3-8.8 m were proposed for Dunkleosteus based on allometric relationships between upper jaw perimeter and total length in extant large-bodied sharks. However, these methods were not statistically evaluated to determine if allometric relationships between body size and mouth size in sharks reliably predicted size in arthrodires. Several smaller arthrodire taxa are known from relatively complete remains, and can be used as independent case studies to test the accuracy of these methods. Results Length estimates for Dunkleosteus are evaluated through an examination of mouth proportions in complete arthrodires and fishes more generally. Currently accepted lengths of 5.3-8.8 m for D. terrelli are mathematically and biologically unlikely for three major reasons: (1) Arthrodires have larger mouths than sharks at similar body sizes. (2) upper jaw perimeter and mouth width produce extreme overestimates of body size (at least twice the actual value) in arthrodires known from complete remains. (3) Reconstructing Dunkleosteus using lengths predicted by upper jaw perimeter results in highly unusual body proportions, including extremely small, shrunken heads and hyper-anguilliform body plans, not seen in complete arthrodires or fishes more generally. Conclusions Length estimates for arthrodires based on the mouth dimensions of extant sharks are not reliable. Arthrodires have proportionally larger mouths than sharks, more similar to catfishes (Siluriformes). The disproportionately large mouths of arthrodires suggest these animals may have consumed larger prey relative to their body size than extant macropredatory sharks, and thus the paleobiology and paleoecology of these two groups may not have been exactly analogous within their respective ecosystems.
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Affiliation(s)
- Russell Engelman
- Department of Biology, Case Western Reserve University, Cleveland, OH, United States of America
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12
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A New Large †Pachycormiform (Teleosteomorpha: †Pachycormiformes) from the Lower Jurassic of Germany, with Affinities to the Suspension-Feeding Clade, and Comments on the Gastrointestinal Anatomy of Pachycormid Fishes. DIVERSITY 2022. [DOI: 10.3390/d14121026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Pachycormiformes is a diverse clade of stem-teleost actinopterygian fishes with a stratigraphic range from the Lower Jurassic (Toarcian) to Upper Cretaceous (Maastrichtian). The Toarcian Posidonienschiefer Formation in SW Germany records the earliest occurrence of †Pachycormiformes in the fossil record, offering unique and crucial insight into the clade’s origins and early adaptive radiation in the Early Jurassic. However, Early Jurassic taxa remain poorly studied with the taxonomic diversity and stratigraphic/geographic distributions insufficiently defined, thus masking the early part of this evolutionary radiation. Here, we report a new genus and species of pachycormid fish from the Posidonienschiefer Formation identified by phylogenetic analysis as falling in an intermediate position between Saurostomus and Ohmdenia at the base of the suspension-feeding clade. The new taxon shows a unique suite of cranial and postcranial characters. Several synapomorphies of the suspension-feeding clade, notably, the morphology of the hyomandibula, elongation of the skull, and reduced squamation are shared with the new taxon. The intestinal tract is exceptionally preserved, providing one of the most complete examples of pachycormid gastric anatomy. A comparison of the gastrointestinal anatomy of the new genus with other pachycormiforms indicates extensive taxonomic variation within the clade, in the configuration of both the midgut and spiral valve, potentially related to trophic divergence. The results highlight an underestimated high diversity and the rapid acquisition of trophic specializations in Pachycormiformes much earlier in the clade’s evolution than previously considered.
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13
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Jobbins M, Rücklin M, Ferrón HG, Klug C. A new selenosteid placoderm from the Late Devonian of the eastern Anti-Atlas (Morocco) with preserved body outline and its ecomorphology. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.969158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Placoderms are an extinct group of early jawed vertebrates that play a key role in understanding the evolution of the gnathostome body plan, including the origin of novelties such as jaws, teeth, and pelvic fins. As placoderms have a poorly ossified axial skeleton, preservation of the mainly cartilaginous axial and fin elements is extremely rare, contrary to the heavily mineralized bones of the skull and thoracic armor. Therefore, the gross anatomy of the animals and body shape is only known from a few taxa, and reconstructions of the swimming function and ecology are speculative. Here, we describe articulated specimens preserving skull roofs, shoulder girdles, most fins, and body outlines of a newly derived arthrodire. Specimens of the selenosteid Amazichthys trinajsticae gen. et sp. nov. display a skull roof with reticular ornamentation and raised sensory lines like Driscollaspis, a median dorsal plate with a unique sharp posterior depression, the pelvic girdle, the proportions and shape of the pectoral, dorsal, and caudal fins as well as a laterally enlarged region resembling the lateral keel of a few modern sharks and bony fishes. Our new phylogenetic analyses support the monophyly of the selenosteid family and place the new genus in a clade with Melanosteus, Enseosteus, Walterosteus, and Draconichthys. The shape of its body and heterocercal caudal fin in combination with the pronounced “lateral keel” suggest Amazichthys trinajsticae was an active macropelagic swimmer capable of reaching high swimming speeds.
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