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Sues HD, Schoch RR. A new Middle Triassic (Ladinian) trilophosaurid stem-archosaur from Germany increases diversity and temporal range of this clade. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230083. [PMID: 36968237 PMCID: PMC10031418 DOI: 10.1098/rsos.230083] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 02/28/2023] [Indexed: 06/18/2023]
Abstract
We report the first trilophosaurid stem-archosaur from Central Europe, Rutiotomodon tytthos gen. et sp. nov., from the Middle Triassic (Ladinian) Erfurt Formation of Baden-Württemberg (Germany). It is currently known from two jaw fragments with distinctive teeth. The labiolingually wide but mesiodistally narrow maxillary and dentary teeth each have a large labial cusp from which an occlusal ridge extends lingually to a small lingual cusp. A mesial and a distal cingulum extend between the labial and lingual cusps. The mesial and distal faces of the labial cusp each bear three prominent, lingually curved apicobasal ridges (arrises). A referred partial dentary has an edentulous, expanded symphysis similar to the mandibular 'beak' in Trilophosaurus buettneri. A review of Coelodontognathus ricovi, from the Lower Triassic (Olenekian) of southwestern Russia, supports its referral to Trilophosauridae rather than Procolophonidae. Based on this reassessment and the new material from the Middle Triassic, the temporal range of trilophosaurids now spans nearly the entire Triassic Period, from the Olenekian to the Rhaetian. Trilophosaurids present craniodental features that indicate omnivory or herbivory with limited oral food processing. They were more diverse in terms of dental structure (and presumably diet) than previously assumed.
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Affiliation(s)
- Hans-Dieter Sues
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - Rainer R. Schoch
- Staatliches Museum für Naturkunde Stuttgart, Stuttgart, Germany
- Institut für Biologie, Universität Hohenheim, Stuttgart, Germany
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Meng J, Mao F. Monotreme middle ear is not primitive for Mammalia. Natl Sci Rev 2021; 8:nwab131. [PMID: 34858616 PMCID: PMC8566185 DOI: 10.1093/nsr/nwab131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 07/08/2021] [Accepted: 07/20/2021] [Indexed: 11/28/2022] Open
Affiliation(s)
- Jin Meng
- Division of Paleontology, American Museum of Natural History, USA
- Earth and Environmental Sciences, Graduate Center, City University of New York, USA
| | - Fangyuan Mao
- Division of Paleontology, American Museum of Natural History, USA
- Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, China
- CASCenter for Excellence in Life and Paleoenvironment, China
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Grossnickle DM, Weaver LN, Jäger KRK, Schultz JA. The evolution of anteriorly directed molar occlusion in mammals. Zool J Linn Soc 2021. [DOI: 10.1093/zoolinnean/zlab039] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Abstract
In non-mammalian synapsids and early mammals, evolutionary transformations in the feeding and hearing apparatuses are posited to have been prerequisites for the radiation of extant mammals. Unlike most vertebrates, including many early synapsids, mammals have precise dental occlusion, a lower jaw composed of one bone, and middle ear ossicles derived from ancestral jaw bones. We illuminate a related functional transition: therian mammals (eutherians and metatherians) evolved anteriorly directed chewing strokes, which are absent in other synapsid lineages. Anteriorly directed jaw movement during occlusion necessitates anteriorly directed muscle force vectors, and we posit that a shift in muscle orientation is reflected in the fossil record by the evolutionary appearance of a posteriorly positioned angular process in cladotherians (therians and their close kin). Anteriorly directed occlusion might have been absent in earlier synapsids because of the presence of attached middle ear elements in the posterior region of the jaw that prohibited the posterior insertion of jaw musculature. These changes to the masticatory apparatus in cladotherians are likely to have permitted the evolution of novel masticatory movements, including grinding in both the anterior and medial directions (e.g. rodents and ungulates, respectively). Thus, this evolutionary transition might have been a crucial prerequisite for the dietary diversification of therians.
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Affiliation(s)
- David M Grossnickle
- Department of Biology, Life Sciences Building, University of Washington, Seattle, WA, USA
| | - Lucas N Weaver
- Department of Biology, Life Sciences Building, University of Washington, Seattle, WA, USA
| | - Kai R K Jäger
- Section Palaeontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 8, Bonn, Germany
| | - Julia A Schultz
- Section Palaeontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 8, Bonn, Germany
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Wang J, Wible JR, Guo B, Shelley SL, Hu H, Bi S. A monotreme-like auditory apparatus in a Middle Jurassic haramiyidan. Nature 2021; 590:279-283. [PMID: 33505017 DOI: 10.1038/s41586-020-03137-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 12/10/2020] [Indexed: 01/30/2023]
Abstract
Among extant vertebrates, mammals are distinguished by having a chain of three auditory ossicles (the malleus, incus and stapes) that transduce sound waves and promote an increased range of audible-especially high-frequencies1. By contrast, the homologous bones in early fossil mammals and relatives also functioned in chewing through their bony attachments to the lower jaw2. Recent discoveries of well-preserved Mesozoic mammals have provided glimpses into the transition from the dual (masticatory and auditory) to the single auditory function for the ossicles, which is now widely accepted to have occurred at least three times in mammal evolution3-6. Here we report a skull and postcranium that we refer to the haramiyidan Vilevolodon diplomylos (dating to the Middle Jurassic epoch (160 million years ago)) and that shows excellent preservation of the malleus, incus and ectotympanic (which supports the tympanic membrane). After comparing this fossil with other Mesozoic and extant mammals, we propose that the overlapping incudomallear articulation found in this and other Mesozoic fossils, in extant monotremes and in early ontogeny in extant marsupials and placentals is a morphology that evolved in several groups of mammals in the transition from the dual to the single function for the ossicles.
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Affiliation(s)
- Junyou Wang
- Centre for Vertebrate Evolutionary Biology, Institute of Palaeontology, Yunnan University, Kunming, China.,Inner Mongolia Museum of Natural History, Hohhot, China
| | - John R Wible
- Centre for Vertebrate Evolutionary Biology, Institute of Palaeontology, Yunnan University, Kunming, China. .,Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA.
| | - Bin Guo
- Inner Mongolia Museum of Natural History, Hohhot, China
| | - Sarah L Shelley
- Section of Mammals, Carnegie Museum of Natural History, Pittsburgh, PA, USA.,School of Geosciences, University of Edinburgh, Edinburgh, UK
| | - Han Hu
- Zoology Division, School of Environmental and Rural Sciences, University of New England, Armidale, New South Wales, Australia
| | - Shundong Bi
- Centre for Vertebrate Evolutionary Biology, Institute of Palaeontology, Yunnan University, Kunming, China. .,Department of Biology, Indiana University of Pennsylvania, Indiana, PA, USA.
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Skeleton of a Cretaceous mammal from Madagascar reflects long-term insularity. Nature 2020; 581:421-427. [DOI: 10.1038/s41586-020-2234-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 02/26/2020] [Indexed: 11/09/2022]
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Meng J, Mao F, Han G, Zheng X, Wang X, Wang Y. A comparative study on auditory and hyoid bones of Jurassic euharamiyidans and contrasting evidence for mammalian middle ear evolution. J Anat 2020; 236:50-71. [PMID: 31498899 PMCID: PMC6904648 DOI: 10.1111/joa.13083] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/06/2019] [Indexed: 12/31/2022] Open
Abstract
The holotypes of euharamiyidan Arboroharamiya allinhopsoni and Arboroharamiya jenkinsi preserve the auditory and hyoid bones, respectively. With additional structures revealed by micro-computerized tomography (CT) and X-ray micro-computed laminography (CL), we provide a detailed description of these minuscule bones. The stapes in the two species of Arboroharamiya are similar in having a strong process for insertion of the stapedius muscle. The incus is similar in having an almond-shaped body and a slim short process, in addition to a robust stapedial process with a short lenticular process preserved in A. allinhopsoni. The plate-like ectotympanic in the two species of Arboroharamiya is similar and comparable to that of Qishou jizantang. The surangular in the two species has a fan-shaped body and a needle-shaped anterior process. The malleus, ectotympanic, and surangular are fully detached from the dentary and should have functioned exclusively for hearing. All the auditory bones of Arboroharamiya display unique features unknown in other mammaliaforms. Moreover, hyoid elements are found in the two species of Arboroharamiya and co-exist with the five auditory bones in the holotype of A. allinhopsoni. The element interpreted as the stylohyal is similar to the bone identified as the ectotympanic in Vilevolodon. We reconstruct the auditory apparatus of Arboroharamiya and compare it with that of Vilevolodon as well as those in extant mammals and basal mammaliaforms. The comparison shows diverse morphological patterns of the auditory region in mammaliaforms. In particular, those of Vilevolodon and Arboroharamiya differ significantly: the former has a mandibular middle ear, whereas the latter possesses a definitive mammalian middle ear. It is puzzling that the two sympatric and dentally similar taxa have such different auditory apparatuses. In light of the available evidence, we argue that the mandibular middle ear reconstructed in Vilevolodon encounters many problems, and the so-called ectotympanic in Vilevolodon may be interpreted as a stylohyal; thus, the dilemma can be resolved.
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Affiliation(s)
- Jin Meng
- Division of PaleontologyAmerican Museum of Natural HistoryNew YorkNYUSA
- Earth and Environmental SciencesGraduate CenterCity University of New YorkNew YorkNYUSA
| | - Fangyuan Mao
- Division of PaleontologyAmerican Museum of Natural HistoryNew YorkNYUSA
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of SciencesInstitute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of SciencesBeijingChina
- CAS Center for Excellence in Life and PaleoenvironmentBeijingChina
| | - Gang Han
- Paleontology CenterBohai UniversityJinzhouChina
- Hainan Tropical Ocean UniversitySanyaChina
| | - Xiao‐Ting Zheng
- Institute of Geology and PaleontologyLinyi UniversityLinyiChina
- Shandong Tianyu Museum of NaturePingyiChina
| | - Xiao‐Li Wang
- Institute of Geology and PaleontologyLinyi UniversityLinyiChina
- Shandong Tianyu Museum of NaturePingyiChina
| | - Yuanqing Wang
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of SciencesInstitute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of SciencesBeijingChina
- CAS Center for Excellence in Life and PaleoenvironmentBeijingChina
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