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Koyabu D. Evolution, conservatism and overlooked homologies of the mammalian skull. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220081. [PMID: 37183902 PMCID: PMC10184252 DOI: 10.1098/rstb.2022.0081] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 01/22/2023] [Indexed: 05/16/2023] Open
Abstract
In the last decade, studies integrating palaeontology, embryology and experimental developmental biology have markedly altered our homological understanding of the mammalian skull. Indeed, new evidence suggests that we should revisit and restructure the conventional anatomical terminology applied to the components of the mammalian skull. Notably, these are classical problems that have remained unresolved since the ninteenth century. In this review, I offer perspectives on the overlooked problems associated with the homology, development, and conservatism of the mammalian skull, aiming to encourage future studies in these areas. I emphasise that ossification patterns, bone fusion, cranial sutures and taxon-specific neomorphic bones in the skull are virtually unexplored, and further studies would improve our homological understanding of the mammalian skull. Lastly, I highlight that overlooked bones may exist in the skull that are not yet known to science and suggest that further search is needed. This article is part of the theme issue 'The mammalian skull: development, structure and function'.
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Affiliation(s)
- Daisuke Koyabu
- Research and Development Center for Precision Medicine, University of Tsukuba, Tsukuba, Japan
- Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Hong Kong, People's Republic of China
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Roston RA, Boessenecker RW, Geisler JH. Evolution and development of the cetacean skull roof: a case study in novelty and homology. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220086. [PMID: 37183892 PMCID: PMC10184229 DOI: 10.1098/rstb.2022.0086] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Accepted: 11/15/2022] [Indexed: 05/16/2023] Open
Abstract
Skulls of living whales and dolphins (cetaceans) are telescoped-bones of the skull roof are overlapped by expanded facial bones and/or anteriorly extended occipital bones. Evolution of the underlying skull roof (calvarium), which lies between the telescoped regions, is relatively unstudied. We explore the evolution and development of the calvarium of toothed whales (odontocetes) by integrating fetal data with Oligocene odontocete fossils from North America, including eight neonatal and juvenile skulls of Olympicetus†. We identified two potential synapomorphies of crown Cetacea: contact of interparietals with frontals, and a single anterior median interparietal (AMI) element. Within Odontoceti, loss of contact between the parietals diagnoses the clade including Delphinida, Ziphiidae and Platanistidae (=Synrhina). Delphinida is characterized by a greatly enlarged interparietal. New fetal series of delphinoids reveal a consistent developmental pattern with three elements: the AMI and bilateral posterior interparietals (PIs). The PIs most resemble the medial interparietal elements of terrestrial artiodactyls, suggesting that the AMI of cetaceans could be a unique ossification. More broadly, the paucity of conserved anatomical relationships of the interparietals, as well as the fact that the elements often do not coalesce into a single bone, demonstrates that assessing homology of the interparietals across mammals remains challenging. This article is part of the theme issue 'The mammalian skull: development, structure and function'.
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Affiliation(s)
- R. A. Roston
- Department of Oral Health Sciences, School of Dentistry, University of Washington, Seattle, WA 98195, USA
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - R. W. Boessenecker
- Department of Geology and Environmental Geosciences, College of Charleston, Charleston, SC 29424, USA
- University of California Museum of Paleontology, University of California, Berkeley, CA 94720, USA
| | - J. H. Geisler
- Department of Anatomy, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY 11568, USA
- Department of Paleobiology, National Museum of Natural History, Washington, DC 20560, USA
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Dudgeon TW, Maddin HC, Evans DC, Mallon JC. The internal cranial anatomy of Champsosaurus (Choristodera: Champsosauridae): Implications for neurosensory function. Sci Rep 2020; 10:7122. [PMID: 32346021 PMCID: PMC7188685 DOI: 10.1038/s41598-020-63956-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 04/06/2020] [Indexed: 11/09/2022] Open
Abstract
Although isolated Champsosaurus remains are common in Upper Cretaceous sediments of North America, the braincase of these animals is enigmatic due to the fragility of their skulls. Here, two well-preserved specimens of Champsosaurus (CMN 8920 and CMN 8919) are CT scanned to describe their neurosensory structures and infer sensory capability. The anterior portion of the braincase was poorly ossified and thus does not permit visualization of a complete endocast; however, impressions of the olfactory stalks indicate that they were elongate and likely facilitated good olfaction. The posterior portion of the braincase is ossified and morphologically similar to that of other extinct diapsids. The absence of an otic notch and an expansion of the pars inferior of the inner ear suggests Champsosaurus was limited to detecting low frequency sounds. Comparison of the shapes of semicircular canals with lepidosaurs and archosauromorphs demonstrates that the semicircular canals of Champsosaurus are most similar to those of aquatic reptiles, suggesting that Champsosaurus was well adapted for sensing movement in an aquatic environment. This analysis also demonstrates that birds, non-avian archosauromorphs, and lepidosaurs possess significantly different canal morphologies, and represents the first morphometric analysis of semicircular canals across Diapsida.
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Affiliation(s)
- Thomas W Dudgeon
- Department of Earth Sciences, Carleton University, Ottawa, Canada.
| | - Hillary C Maddin
- Department of Earth Sciences, Carleton University, Ottawa, Canada
| | - David C Evans
- Vertebrate Palaeontology, Royal Ontario Museum, Toronto, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Jordan C Mallon
- Department of Earth Sciences, Carleton University, Ottawa, Canada.,Beaty Centre for Species Discovery and Palaeobiology Section, Canadian Museum of Nature, Ottawa, Canada
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Wöss C, Unterberger SH, Degenhart G, Akolkar A, Traxl R, Kuhn V, Schirmer M, Pallua AK, Tappert R, Pallua JD. Comparison of structure and composition of a fossil Champsosaurus vertebra with modern Crocodylidae vertebrae: A multi-instrumental approach. J Mech Behav Biomed Mater 2020; 104:103668. [PMID: 32174426 DOI: 10.1016/j.jmbbm.2020.103668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 01/29/2020] [Accepted: 02/01/2020] [Indexed: 11/30/2022]
Abstract
Information on the adaptation of bone structures during evolution is rare since histological data are limited. Micro- and nano-computed tomography of a fossilized vertebra from Champsosaurus sp., which has an estimated age of 70-73 million years, revealed lower porosity and higher bone density compared to modern Crocodylidae vertebrae. Mid-infrared reflectance and energy dispersive X-ray mapping excluded a petrification process, and demonstrated a typical carbonate apatite distribution, confirming histology in light- and electron microscopy of the preserved vertebra. As a consequence of this evolutionary process, the two vertebrae of modern Crocodylidae show reduced overall stiffness in the finite element analysis simulation compared to the fossilized Champsosaurus sp. vertebra, with predominant stiffness along the longitudinal z-axes.
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Affiliation(s)
- C Wöss
- Institute of Legal Medicine, Medical University of Innsbruck, Müllerstraße 44, 6020, Innsbruck, Austria
| | - S H Unterberger
- Unit for Material Technology, University of Innsbruck, Technikerstraße 13, 6020, Innsbruck, Austria
| | - G Degenhart
- Department of Radiology, Medical University of Innsbruck, Anichstraße 35, 6020, Innsbruck, Austria
| | - A Akolkar
- Illwerke vkw Professorship for Energy Efficiency, Vorarlberg University of Applied Sciences, Hochschulstraße 1, 6850, Dornbirn, Austria; Josef Ressel Center for Applied Computational Science in Energy, Finance, and Logistics, Hochschulstraße 1, 6850, Dornbirn, Austria
| | - R Traxl
- Unit for Material Technology, University of Innsbruck, Technikerstraße 13, 6020, Innsbruck, Austria
| | - V Kuhn
- Department of Traumatology, Medical University of Innsbruck, Anichstraße 35, 6020, Innsbruck, Austria
| | - M Schirmer
- Department of Internal Medicine, Clinic II, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - A K Pallua
- Former Institute for Computed Tomography-Neuro CT, Medical University of Innsbruck, Anichstraße 35, 6020, Innsbruck, Austria
| | - R Tappert
- Hyperspectral Intelligence Inc., Box 851, Gibsons, British Columbia, V0N 1V0, Canada
| | - J D Pallua
- Institute of Legal Medicine, Medical University of Innsbruck, Müllerstraße 44, 6020, Innsbruck, Austria; Institute of Pathology, Neuropathology and Molecular Pathology, Medical University of Innsbruck, Müllerstraße 44, 6020, Innsbruck, Austria.
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