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Motani R, Pyenson ND. Downsizing a heavyweight: factors and methods that revise weight estimates of the giant fossil whale Perucetus colossus. PeerJ 2024; 12:e16978. [PMID: 38436015 PMCID: PMC10909350 DOI: 10.7717/peerj.16978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 01/29/2024] [Indexed: 03/05/2024] Open
Abstract
Extremes in organismal size have broad interest in ecology and evolution because organismal size dictates many traits of an organism's biology. There is particular fascination with identifying upper size extremes in the largest vertebrates, given the challenges and difficulties of measuring extant and extinct candidates for the largest animal of all time, such as whales, terrestrial non-avian dinosaurs, and extinct marine reptiles. The discovery of Perucetus colossus, a giant basilosaurid whale from the Eocene of Peru, challenged many assumptions about organismal extremes based on reconstructions of its body weight that exceeded reported values for blue whales (Balaenoptera musculus). Here we present an examination of a series of factors and methodological approaches to assess reconstructing body weight in Perucetus, including: data sources from large extant cetaceans; fitting published body mass estimates to body outlines; testing the assumption of isometry between skeletal and body masses, even with extrapolation; examining the role of pachyostosis in body mass reconstructions; addressing method-dependent error rates; and comparing Perucetus with known physiological and ecological limits for living whales, and Eocene oceanic productivity. We conclude that Perucetus did not exceed the body mass of today's blue whales. Depending on assumptions and methods, we estimate that Perucetus weighed 60-70 tons assuming a length 17 m. We calculated larger estimates potentially as much as 98-114 tons at 20 m in length, which is far less than the direct records of blue whale weights, or the 270 ton estimates that we calculated for body weights of the largest blue whales measured by length.
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Affiliation(s)
- Ryosuke Motani
- Department of Earth and Planetary Sciences, University of California, Davis, Davis, California, United States
| | - Nicholas D. Pyenson
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, District of Columbia, United States
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2
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Bennion RF, Maxwell EE, Lambert O, Fischer V. Craniodental ecomorphology of the large Jurassic ichthyosaurian Temnodontosaurus. J Anat 2024; 244:22-41. [PMID: 37591692 PMCID: PMC10734653 DOI: 10.1111/joa.13939] [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: 04/02/2023] [Revised: 07/12/2023] [Accepted: 07/18/2023] [Indexed: 08/19/2023] Open
Abstract
Marine amniotes have played many crucial roles in ocean ecosystems since the Triassic, including predation at the highest trophic levels. One genus often placed into this guild is the large Early Jurassic neoichthyosaurian Temnodontosaurus, the only post-Triassic ichthyosaurian known with teeth which bear a distinct cutting edge or carina. This taxonomically problematic genus is currently composed of seven species which show a wide variety of skull and tooth morphologies. Here we assess the craniodental disparity in Temnodontosaurus using a series of functionally informative traits. We describe the range of tooth morphologies in the genus in detail, including the first examples of serrated carinae in ichthyosaurians. These consist of false denticles created by the interaction of enamel ridgelets with the carinal keel, as well as possible cryptic true denticles only visible using scanning electron microscopy. We also find evidence for heterodonty in the species T. platyodon, with unicarinate mesial teeth likely playing a role in prey capture and labiolingually compressed, bicarinate distal teeth likely involved in prey processing. This type of heterodonty appears to be convergent with a series of other marine amniotes including early cetaceans. Overall, the species currently referred to as the genus Temnodontosaurus show a range of craniodental configurations allowing prey to be captured and processed in different ways - for example, T. eurycephalus has a deep snout and relatively small bicarinate teeth likely specialised for increased wound infliction and grip-and-tear feeding, whereas T. platyodon has a more elongate yet robust snout and larger teeth and may be more adapted for grip-and-shear feeding. These results suggest the existence of niche partitioning at higher trophic levels in Early Jurassic ichthyosaurians and have implications for future work on the taxonomy of this wastebasket genus, as well as for research into the ecology of other extinct megapredatory marine tetrapods.
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Affiliation(s)
- R F Bennion
- Evolution & Diversity Dynamics Lab, Université de Liège, Liège, Belgium
- OD Earth and History of Life, Royal Belgian Institute of Natural Sciences, Brussels, Belgium
| | - E E Maxwell
- Staatliches Museum für Naturkunde Stuttgart, Stuttgart, Germany
| | - O Lambert
- OD Earth and History of Life, Royal Belgian Institute of Natural Sciences, Brussels, Belgium
| | - V Fischer
- Evolution & Diversity Dynamics Lab, Université de Liège, Liège, Belgium
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3
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Bianucci G, Lambert O, Urbina M, Merella M, Collareta A, Bennion R, Salas-Gismondi R, Benites-Palomino A, Post K, de Muizon C, Bosio G, Di Celma C, Malinverno E, Pierantoni PP, Villa IM, Amson E. A heavyweight early whale pushes the boundaries of vertebrate morphology. Nature 2023; 620:824-829. [PMID: 37532931 DOI: 10.1038/s41586-023-06381-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 06/28/2023] [Indexed: 08/04/2023]
Abstract
The fossil record of cetaceans documents how terrestrial animals acquired extreme adaptations and transitioned to a fully aquatic lifestyle1,2. In whales, this is associated with a substantial increase in maximum body size. Although an elongate body was acquired early in cetacean evolution3, the maximum body mass of baleen whales reflects a recent diversification that culminated in the blue whale4. More generally, hitherto known gigantism among aquatic tetrapods evolved within pelagic, active swimmers. Here we describe Perucetus colossus-a basilosaurid whale from the middle Eocene epoch of Peru. It displays, to our knowledge, the highest degree of bone mass increase known to date, an adaptation associated with shallow diving5. The estimated skeletal mass of P. colossus exceeds that of any known mammal or aquatic vertebrate. We show that the bone structure specializations of aquatic mammals are reflected in the scaling of skeletal fraction (skeletal mass versus whole-body mass) across the entire disparity of amniotes. We use the skeletal fraction to estimate the body mass of P. colossus, which proves to be a contender for the title of heaviest animal on record. Cetacean peak body mass had already been reached around 30 million years before previously assumed, in a coastal context in which primary productivity was particularly high.
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Affiliation(s)
- Giovanni Bianucci
- Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
| | - Olivier Lambert
- D.O. Terre et Histoire de la Vie, Institut Royal des Sciences Naturelles de Belgique, Brussels, Belgium
| | - Mario Urbina
- Departamento de Paleontología de Vertebrados, Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, Lima, Perú
| | - Marco Merella
- Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
| | - Alberto Collareta
- Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
| | - Rebecca Bennion
- D.O. Terre et Histoire de la Vie, Institut Royal des Sciences Naturelles de Belgique, Brussels, Belgium
- Evolution & Diversity Dynamics Lab, UR Geology, Université de Liège, Liège, Belgium
| | - Rodolfo Salas-Gismondi
- Departamento de Paleontología de Vertebrados, Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, Lima, Perú
- Facultad de Ciencias y Filosofía/Centro de Investigación para el Desarrollo Integral y Sostenible, Laboratorios de Investigación y Desarrollo, Universitad Peruana Cayetano Heredia Lima, Lima, Perú
| | - Aldo Benites-Palomino
- Departamento de Paleontología de Vertebrados, Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, Lima, Perú
- Department of Paleontology, University of Zurich, Zurich, Switzerland
| | - Klaas Post
- Natuurhistorisch Museum Rotterdam, Rotterdam, The Netherlands
| | - Christian de Muizon
- Département Origines et Évolution, CR2P (CNRS, MNHN, Sorbonne Université), Muséum National d'Histoire Naturelle, Paris, France
| | - Giulia Bosio
- Dipartimento di Scienze dell'Ambiente e della Terra, Università degli Studi di Milano-Bicocca, Milano, Italy
| | - Claudio Di Celma
- School of Science and Technology, University of Camerino, Camerino, Italy
| | - Elisa Malinverno
- Dipartimento di Scienze dell'Ambiente e della Terra, Università degli Studi di Milano-Bicocca, Milano, Italy
| | | | | | - Eli Amson
- Staatliches Museum für Naturkunde Stuttgart, Stuttgart, Germany.
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4
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Kast ER, Griffiths ML, Kim SL, Rao ZC, Shimada K, Becker MA, Maisch HM, Eagle RA, Clarke CA, Neumann AN, Karnes ME, Lüdecke T, Leichliter JN, Martínez-García A, Akhtar AA, Wang XT, Haug GH, Sigman DM. Cenozoic megatooth sharks occupied extremely high trophic positions. SCIENCE ADVANCES 2022; 8:eabl6529. [PMID: 35731884 PMCID: PMC9217088 DOI: 10.1126/sciadv.abl6529] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 05/05/2022] [Indexed: 06/15/2023]
Abstract
Trophic position is a fundamental characteristic of animals, yet it is unknown in many extinct species. In this study, we ground-truth the 15N/14N ratio of enameloid-bound organic matter (δ15NEB) as a trophic level proxy by comparison to dentin collagen δ15N and apply this method to the fossil record to reconstruct the trophic level of the megatooth sharks (genus Otodus). These sharks evolved in the Cenozoic, culminating in Otodus megalodon, a shark with a maximum body size of more than 15 m, which went extinct 3.5 million years ago. Very high δ15NEB values (22.9 ± 4.4‰) of O. megalodon from the Miocene and Pliocene show that it occupied a higher trophic level than is known for any marine species, extinct or extant. δ15NEB also indicates a dietary shift in sharks of the megatooth lineage as they evolved toward the gigantic O. megalodon, with the highest trophic level apparently reached earlier than peak size.
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Affiliation(s)
- Emma R. Kast
- Department of Geosciences, Princeton University, Princeton, NJ 08544, USA
- Department of Earth Sciences, University of Cambridge, Cambridge, CB23EQ, UK
| | - Michael L. Griffiths
- Department of Environmental Science, William Paterson University of New Jersey, Wayne, NJ 07470, USA
| | - Sora L. Kim
- Department of Life and Environmental Sciences, University of California Merced, Merced, CA 95343, USA
| | - Zixuan C. Rao
- Department of Geosciences, Princeton University, Princeton, NJ 08544, USA
| | - Kenshu Shimada
- Department of Environmental Science and Studies, DePaul University, Chicago, IL 60614, USA
- Department of Biological Sciences, DePaul University, Chicago, IL 60614, USA
- Sternberg Museum of Natural History, Fort Hays State University, Hays, KS 67601, USA
| | - Martin A. Becker
- Department of Environmental Science, William Paterson University of New Jersey, Wayne, NJ 07470, USA
| | - Harry M. Maisch
- Department of Marine and Earth Sciences, Florida Gulf Coast University, Fort Myers, FL 33965, USA
| | - Robert A. Eagle
- Department of Atmospheric and Oceanic Sciences. Institute of the Environment and Sustainability, University of California, Los Angeles, CA 90095, USA
| | - Chelesia A. Clarke
- Department of Environmental Science, William Paterson University of New Jersey, Wayne, NJ 07470, USA
| | - Allison N. Neumann
- Department of Environmental Science, William Paterson University of New Jersey, Wayne, NJ 07470, USA
| | - Molly E. Karnes
- Department of Life and Environmental Sciences, University of California Merced, Merced, CA 95343, USA
| | - Tina Lüdecke
- Emmy Noether Group for Hominin Meat Consumption, Max Planck Institute for Chemistry, 55128 Mainz, Germany
- Senckenberg Biodiversity and Climate Research Centre, 60325 Frankfurt, Germany
| | - Jennifer N. Leichliter
- Emmy Noether Group for Hominin Meat Consumption, Max Planck Institute for Chemistry, 55128 Mainz, Germany
- Johannes Gutenberg University, Institute of Geosciences, 55128 Mainz, Germany
| | - Alfredo Martínez-García
- Department of Climate Geochemistry, Max Planck Institute for Chemistry, 55128 Mainz, Germany
| | - Alliya A. Akhtar
- Department of Geosciences, Princeton University, Princeton, NJ 08544, USA
| | - Xingchen T. Wang
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467, USA
| | - Gerald H. Haug
- Department of Climate Geochemistry, Max Planck Institute for Chemistry, 55128 Mainz, Germany
- Department of Earth Sciences, ETH Zürich, CH-8092 Zürich, Switzerland
| | - Daniel M. Sigman
- Department of Geosciences, Princeton University, Princeton, NJ 08544, USA
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5
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OUP accepted manuscript. Zool J Linn Soc 2022. [DOI: 10.1093/zoolinnean/zlac019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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6
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Gohar AS, Antar MS, Boessenecker RW, Sabry DA, El-Sayed S, Seiffert ER, Zalmout IS, Sallam HM. A new protocetid whale offers clues to biogeography and feeding ecology in early cetacean evolution. Proc Biol Sci 2021; 288:20211368. [PMID: 34428967 PMCID: PMC8385364 DOI: 10.1098/rspb.2021.1368] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 07/30/2021] [Indexed: 11/12/2022] Open
Abstract
Over about 10 million years, the ancestors of whales transformed from herbivorous, deer-like, terrestrial mammals into carnivorous and fully aquatic cetaceans. Protocetids are Eocene whales that represent a unique semiaquatic stage in that dramatic evolutionary transformation. Here, we report on a new medium-sized protocetid, Phiomicetus anubis gen. et sp. nov., consisting of a partial skeleton from the middle Eocene (Lutetian) of the Fayum Depression in Egypt. The new species differs from other protocetids in having large, elongated temporal fossae, anteriorly placed pterygoids, elongated parietals, an unfused mandibular symphysis that terminates at the level of P3, and a relatively enlarged I3. Unique features of the skull and mandible suggest a capacity for more efficient oral mechanical processing than the typical protocetid condition, thereby allowing for a strong raptorial feeding style. Phylogenetic analysis nests Phiomicetus within the paraphyletic Protocetidae, as the most basal protocetid known from Africa. Recovery of Phiomicetus from the same bed that yielded the remingtonocetid Rayanistes afer provides the first clear evidence for the co-occurrence of the basal cetacean families Remingtonocetidae and Protocetidae in Africa. The discovery of Phiomicetus further augments our understanding of the biogeography and feeding ecology of early whales.
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Affiliation(s)
- Abdullah S. Gohar
- Mansoura University Vertebrate Paleontology Center, Department of Geology, Faculty of Science, Egyptian Environmental Affairs Agency, Cairo 11728, Egypt
| | - Mohammed S. Antar
- Mansoura University Vertebrate Paleontology Center, Department of Geology, Faculty of Science, Egyptian Environmental Affairs Agency, Cairo 11728, Egypt
- Department of Geology and Paleontology, Nature Conservation Sector, Egyptian Environmental Affairs Agency, Cairo 11728, Egypt
| | - Robert W. Boessenecker
- Department of Geology and Environmental Geosciences, College of Charleston, Charleston, SC 29424, USA
| | - Dalia A. Sabry
- Department of Zoology, Faculty of Science, Mansoura University, Mansoura 35516, Egypt
| | - Sanaa El-Sayed
- Mansoura University Vertebrate Paleontology Center, Department of Geology, Faculty of Science, Egyptian Environmental Affairs Agency, Cairo 11728, Egypt
| | - Erik R. Seiffert
- Department of Integrative Anatomical Sciences, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA 90033, USA
| | - Iyad S. Zalmout
- Department of Paleontology, Saudi Geological Survey, Jeddah 21514, Saudi Arabia
| | - Hesham M. Sallam
- Mansoura University Vertebrate Paleontology Center, Department of Geology, Faculty of Science, Egyptian Environmental Affairs Agency, Cairo 11728, Egypt
- Institute of Global Health and Human Ecology, School of Science and Engineering, American University in Cairo, New Cairo 11835, Egypt
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7
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Bosio G, Collareta A, Di Celma C, Lambert O, Marx FG, de Muizon C, Gioncada A, Gariboldi K, Malinverno E, Malca RV, Urbina M, Bianucci G. Taphonomy of marine vertebrates of the Pisco Formation (Miocene, Peru): Insights into the origin of an outstanding Fossil-Lagerstätte. PLoS One 2021; 16:e0254395. [PMID: 34264979 PMCID: PMC8282071 DOI: 10.1371/journal.pone.0254395] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 06/28/2021] [Indexed: 11/23/2022] Open
Abstract
The Miocene Pisco Formation, broadly exposed in the Ica Desert of southern Peru, is among the most outstanding Cenozoic marine Fossil-Lagerstätten worldwide. It is renowned for its exceptional preservation and abundance of vertebrate fossils, including a rich assemblage of whales and dolphins (Cetacea). Here, we integrate taphonomic data on 890 marine vertebrate fossils, gathered through 16 different localities. Our observations range from the taxonomic distribution, articulation, completeness, disposition and orientation of skeletons, to the presence of bite marks, associations with shark teeth and macro-invertebrates, bone and soft tissue preservation, and the formation of attendant carbonate concretions and sedimentary structures. We propose that the exceptional preservation characterising many Pisco vertebrates, as well as their exceptionally high abundance, cannot be ascribed to a single cause like high sedimentation rates (as proposed in the past), but rather to the interplay of several favourable factors including: (i) low levels of dissolved oxygen at the seafloor (with the intervention of seasonal anoxic events); (ii) the early onset of mineralisation processes like apatite dissolution/recrystallisation and carbonate mineral precipitation; (iii) rapid burial of carcasses in a soupy substrate and/or a novel mechanism involving scour-induced self-burial; and (iv) original biological richness. Collectively, our observations provide a comprehensive overview of the taphonomic processes that shaped one of South America's most important fossil deposits, and suggest a model for the formation of other marine vertebrate Fossil-Lagerstätten.
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Affiliation(s)
- Giulia Bosio
- Dipartimento di Scienze dell’Ambiente e della Terra, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Alberto Collareta
- Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
| | - Claudio Di Celma
- Scuola di Scienze e Tecnologie, Università di Camerino, Camerino, Italy
| | - Olivier Lambert
- D.O. Terre et Histoire de la Vie, Institut Royal des Sciences Naturelles de Belgique, Bruxelles, Belgium
| | - Felix G. Marx
- Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand
- Department of Geology, University of Otago, Dunedin, New Zealand
| | - Christian de Muizon
- Département Origines et Evolution, CR2P UMR 7207, (MNHN, CNRS, UPMC, Sorbonne-Université), Muséum national d’Histoire naturelle, Paris, France
| | - Anna Gioncada
- Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
| | - Karen Gariboldi
- Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
| | - Elisa Malinverno
- Dipartimento di Scienze dell’Ambiente e della Terra, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Rafael Varas Malca
- Departamento de Paleontologia de Vertebrados, Museo de Historia Natural-UNMSM, Lima, Peru
| | - Mario Urbina
- Departamento de Paleontologia de Vertebrados, Museo de Historia Natural-UNMSM, Lima, Peru
| | - Giovanni Bianucci
- Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
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Cawley JJ, Marramà G, Carnevale G, Villafaña JA, López-Romero FA, Kriwet J. Rise and fall of †Pycnodontiformes: Diversity, competition and extinction of a successful fish clade. Ecol Evol 2021; 11:1769-1796. [PMID: 33614003 PMCID: PMC7882952 DOI: 10.1002/ece3.7168] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 12/04/2020] [Accepted: 12/11/2020] [Indexed: 12/25/2022] Open
Abstract
†Pycnodontiformes was a successful lineage of primarily marine fishes that broadly diversified during the Mesozoic. They possessed a wide variety of body shapes and were adapted to a broad range of food sources. Two other neopterygian clades possessing similar ecological adaptations in both body morphology (†Dapediiformes) and dentition (Ginglymodi) also occurred in Mesozoic seas. Although these groups occupied the same marine ecosystems, the role that competitive exclusion and niche partitioning played in their ability to survive alongside each other remains unknown. Using geometric morphometrics on both the lower jaw (as constraint for feeding adaptation) and body shape (as constraint for habitat adaptation), we show that while dapediiforms and ginglymodians occupy similar lower jaw morphospace, pycnodontiforms are completely separate. Separation also occurs between the clades in body shape so that competition reduction between pycnodontiforms and the other two clades would have resulted in niche partitioning. Competition within pycnodontiforms seemingly was reduced further by evolving different feeding strategies as shown by disparate jaw shapes that also indicate high levels of plasticity. Acanthomorpha was a teleostean clade that evolved later in the Mesozoic and which has been regarded as implicated in driving the pycnodontiforms to extinction. Although they share similar body shapes, no coeval acanthomorphs had similar jaw shapes or dentitions for dealing with hard prey like pycnodontiforms do and so their success being a factor in pycnodontiform extinction is unlikely. Sea surface temperature and eustatic variations also had no impact on pycnodontiform diversity patterns according to our results. Conversely, the occurrence and number of available reefs and hardgrounds as habitats through time seems to be the main factor in pycnodontiform success. Decline in such habitats during the Late Cretaceous and Palaeogene might have had deleterious consequences for pycnodontiform diversity. Acanthomorphs occupied the niches of pycnodontiforms during the terminal phase of their existence.
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Affiliation(s)
- John J Cawley
- Faculty of Earth Science, Geography and Astronomy Department of Palaeontology University of Vienna Geozentrum Vienna Austria
| | - Giuseppe Marramà
- Dipartimento di Scienze della Terra Università degli Studi di Torino Torino Italy
| | - Giorgio Carnevale
- Dipartimento di Scienze della Terra Università degli Studi di Torino Torino Italy
| | - Jaime A Villafaña
- Faculty of Earth Science, Geography and Astronomy Department of Palaeontology University of Vienna Geozentrum Vienna Austria.,Centro de Investigación en Recursos Naturales y Sustentabilidad Universidad Bernardo O'Higgins Santiago Chile.,Paleontological Institute and Museum University of Zurich Zurich Switzerland
| | - Faviel A López-Romero
- Faculty of Earth Science, Geography and Astronomy Department of Palaeontology University of Vienna Geozentrum Vienna Austria
| | - Jürgen Kriwet
- Faculty of Earth Science, Geography and Astronomy Department of Palaeontology University of Vienna Geozentrum Vienna Austria
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9
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Gingerich PD, Antar MSM, Zalmout IS. Aegicetus gehennae, a new late Eocene protocetid (Cetacea, Archaeoceti) from Wadi Al Hitan, Egypt, and the transition to tail-powered swimming in whales. PLoS One 2019; 14:e0225391. [PMID: 31825956 PMCID: PMC6905522 DOI: 10.1371/journal.pone.0225391] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 10/30/2019] [Indexed: 11/19/2022] Open
Abstract
Aegicetus gehennae is a new African protocetid whale based on a partial skull with much of an associated postcranial skeleton. The type specimen, Egyptian Geological Museum, Cairo [CGM] 60584, was found near the base of the early-Priabonian-age (earliest late Eocene) Gehannam Formation of the Wadi Al Hitan World Heritage Site in Egypt. The cranium is distinctive in having ventrally-deflected exoccipitals. The vertebral column is complete from cervical C1 through caudal Ca9, with a vertebral formula of 7:15:4:4:9+, representing, respectively, the number of cervical, thoracic, lumbar, sacral, and caudal vertebrae. CGM 60584 has two more rib-bearing thoracic vertebrae than other known protocetids, and two fewer lumbars. Sacral centra are unfused, and there is no defined auricular surface on the ilium. Thus there was no weight-bearing sacroiliac joint. The sternum is distinctive in being exceptionally broad and flat. The body weight of CGM 60584, a putative male, is estimated to have been about 890 kg in life. Long bones of the fore and hind limbs are shorter than expected for a protocetid of this size. Bones of the manus are similar in length and more robust compared to those of the pes. A log vertebral length profile for CGM 60584 parallels that of middle Eocene Maiacetus inuus through the anterior and middle thorax, but more posterior vertebrae are proportionally longer. Vertebral elongation, loss of a sacroiliac articulation, and hind limb reduction indicate that Aegicetus gehennae was more fully aquatic and less specialized as a foot-powered swimmer than earlier protocetids. It is doubtful that A. gehennae had a tail fluke, and the caudal flattening known for basilosaurids is shorter relative to vertebral column length than flattening associated with a fluke in any modern whale. Late protocetids and basilosaurids had relatively long skeletons, longer than those known earlier and later, and the middle-to-late Eocene transition from foot-powered to tail-powered swimming seemingly involved some form of mid-body-and-tail undulation.
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Affiliation(s)
- Philip D. Gingerich
- Museum of Paleontology, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
| | - Mohammed Sameh M. Antar
- Department of Geology and Paleontology, Nature Conservation Sector, Egyptian Environmental Affairs Agency, Cairo, Egypt
| | - Iyad S. Zalmout
- Museum of Paleontology, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Paleontology, Saudi Geological Survey, Jeddah, Saudi Arabia
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