1
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Bronzati M, Langer MC, Ezcurra MD, Stocker MR, Nesbitt SJ. Braincase and neuroanatomy of the lagerpetid Dromomeron gregorii (Archosauria, Pterosauromorpha) with comments on the early evolution of the braincase and associated soft tissues in Avemetatarsalia. Anat Rec (Hoboken) 2024; 307:1147-1174. [PMID: 37794742 DOI: 10.1002/ar.25334] [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: 07/06/2023] [Revised: 09/06/2023] [Accepted: 09/18/2023] [Indexed: 10/06/2023]
Abstract
The anatomy of the braincase and associated soft tissues of the lagerpetid Dromomeron gregorii (Archosauria: Avemetatarsalia) from the Late Triassic of the United States is here described. This corresponds to the first detailed description of cranial materials of Lagerpetidae, an enigmatic group of Late Triassic (c. 236-200 Million years ago) animals that are the closest known relatives of pterosaurs, the flying reptiles. The braincase of D. gregorii is characterized by the presence of an anteriorly elongated laterosphenoid and a postparietal, features observed in stem-archosaurs but that were still unknown in early members of the avian lineage of archosaurs. Using micro-computed tomography (CT-scan data), we present digital reconstructions of the brain and endosseous labyrinth of D. gregorii. The brain of D. gregorii exhibits a floccular lobe of the cerebellum that projects within the space of the semicircular canals. The semicircular canals are relatively large when compared to other archosauromorphs, with the anterior canal exhibiting a circular shape. These features of the sensory structures of D. gregorii are more similar to those of pterosaurs than to those of other early avemetatarsalians. In sum, the braincase anatomy of D. gregorii shows a combination of plesiomorphic and apomorphic features in the phylogenetic context of Archosauria and suggests that the still poorly understood early evolution of the braincase in avemetatarsalians is complex, with a scenario of independent acquisitions and losses of character states.
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Affiliation(s)
- Mario Bronzati
- Fachbereich Geowissenschaften der Eberhard Karls University Tübingen, Tübingen, Germany
| | - Max C Langer
- Departamento de Biologia, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Martín D Ezcurra
- Sección Paleontología de Vertebrados, CONICET-Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Buenos Aires, Argentina
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
| | - Michelle R Stocker
- Department of Geosciences, Virginia Tech, Blacksburg, Virginia, USA
- Vertebrate Paleontology Collection, The University of Texas at Austin, Austin, Texas, USA
| | - Sterling J Nesbitt
- Department of Geosciences, Virginia Tech, Blacksburg, Virginia, USA
- Vertebrate Paleontology Collection, The University of Texas at Austin, Austin, Texas, USA
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2
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Ballell A, Benton MJ, Rayfield EJ. Dental form and function in the early feeding diversification of dinosaurs. SCIENCE ADVANCES 2022; 8:eabq5201. [PMID: 36525501 PMCID: PMC9757754 DOI: 10.1126/sciadv.abq5201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 07/05/2022] [Accepted: 11/16/2022] [Indexed: 06/17/2023]
Abstract
Dinosaurs evolved a remarkable diversity of dietary adaptations throughout the Mesozoic, but the origins of different feeding modes are uncertain, especially the multiple origins of herbivory. Feeding habits of early dinosaurs have mostly been inferred from qualitative comparisons of dental morphology with extant analogs. Here, we use biomechanical and morphometric methods to investigate the dental morphofunctional diversity of early dinosaurs in comparison with extant squamates and crocodylians and predict their diets using machine learning classification models. Early saurischians/theropods are consistently classified as carnivores. Sauropodomorphs underwent a dietary shift from faunivory to herbivory, experimenting with diverse diets during the Triassic and Early Jurassic, and early ornithischians were likely omnivores. Obligate herbivory was a late evolutionary innovation in both clades. Carnivory is the most plausible ancestral diet of dinosaurs, but omnivory is equally likely under certain phylogenetic scenarios. This early dietary diversity was fundamental in the rise of dinosaurs to ecological dominance.
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3
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Chapelle KEJ, Barrett PM, Choiniere JN, Botha J. Interelemental osteohistological variation in Massospondylus carinatus and its implications for locomotion. PeerJ 2022; 10:e13918. [PMID: 36172498 PMCID: PMC9512004 DOI: 10.7717/peerj.13918] [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: 05/02/2022] [Accepted: 07/28/2022] [Indexed: 01/19/2023] Open
Abstract
Massospondylus carinatus Owen, 1854 is an iconic basal sauropodomorph dinosaur from the Early Jurassic of southern Africa. Over 200 specimens have been referred to this taxon, spanning the entire ontogenetic series from embryo to adult. Consequently, it provides an ideal sample for investigating dinosaur developmental biology, including growth patterns and growth rates, through osteohistological analysis. Massospondylus carinatus was the first early-branching sauropodomorph dinosaur for which a femoral growth series was sampled. Since then, growth series of other non-avian dinosaur taxa have shown that growth plasticity, interelemental variation, and ontogenetic locomotory shifts can complicate our understanding of growth curves and patterns. To investigate these questions further, it is necessary to sample multiple skeletal elements from multiple individuals across a large range of sizes, something that is often hindered by the incompleteness of the fossil record. Here, we conducted a broad, multielement osteohistological study of long bones (excluding metapodials) from 27 specimens of Massospondylus carinatus that span its ontogenetic series. Our study reveals substantial variations in growth history. A cyclical woven-parallel complex is the predominant bone tissue pattern during early and mid-ontogeny, which transitions to slower forming parallel-fibred bone during very late ontogeny. The bone tissue is interrupted by irregularly spaced cyclical growth marks (CGMs) including lines of arrested growth indicating temporary cessations in growth. These CGMs show that the previously recorded femoral growth plasticity is also visible in other long bones, with a poor correlation between body size (measured by midshaft circumference) and CGM numbers. Furthermore, we found that the growth trajectory for an individual can vary depending on which limb element is studied. This makes the establishment of an accurate growth curve and determination of the onset of reproductive maturity difficult for this taxon. Finally, we found no evidence of differential growth rates in forelimb vs hindlimb samples from the same individual, providing further evidence falsifying hypothesised ontogenetic postural shifts in Massospondylus carinatus.
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Affiliation(s)
- Kimberley EJ Chapelle
- Division of Paleontology, American Museum of Natural History, New York City, New York, United States of America,Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
| | - Paul M. Barrett
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, Gauteng, South Africa,Science Group, Natural History Museum, London, United Kingdom
| | - Jonah N. Choiniere
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
| | - Jennifer Botha
- Department of Zoology and Entomology, University of the Free State, Bloemfontein, Free State, South Africa,Karoo Palaeontology Department, National Museum, Bloemfontein, Free State, South Africa
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4
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Das S, Brecko J, Pauwels OSG, Merilä J. Cranial osteology of
Hypoptophis
(Aparallactinae: Atractaspididae: Caenophidia), with a discussion on the evolution of its fossorial adaptations. J Morphol 2022; 283:510-538. [PMID: 35094424 PMCID: PMC9305546 DOI: 10.1002/jmor.21457] [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: 04/17/2021] [Revised: 01/10/2022] [Accepted: 01/27/2022] [Indexed: 11/08/2022]
Affiliation(s)
- Sunandan Das
- Ecological Genetics Research Unit, Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, FI‐00014 University of Helsinki Finland
| | - Jonathan Brecko
- Department of Recent Vertebrates Royal Belgian Institute of Natural Sciences (RBINS), Rue Vautier 29, B‐1000 Brussels Belgium
- Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren Belgium
| | - Olivier S. G. Pauwels
- Department of Recent Vertebrates Royal Belgian Institute of Natural Sciences (RBINS), Rue Vautier 29, B‐1000 Brussels Belgium
| | - Juha Merilä
- Ecological Genetics Research Unit, Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, FI‐00014 University of Helsinki Finland
- Division of Ecology and Biodiversity, Faculty of Science The University of Hong Kong, KBSB 3N19 Hong Kong SAR
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5
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Schade M, Knötschke N, Hörnig MK, Paetzel C, Stumpf S. Neurovascular anatomy of dwarf dinosaur implies precociality in sauropods. eLife 2022; 11:82190. [PMID: 36537069 PMCID: PMC9767461 DOI: 10.7554/elife.82190] [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: 07/26/2022] [Accepted: 11/11/2022] [Indexed: 12/24/2022] Open
Abstract
Macronaria, a group of mostly colossal sauropod dinosaurs, comprised the largest terrestrial vertebrates of Earth's history. However, some of the smallest sauropods belong to this group as well. The Late Jurassic macronarian island dwarf Europasaurus holgeri is one of the most peculiar and best-studied sauropods worldwide. So far, the braincase material of this taxon from Germany pended greater attention. With the aid of micro-computed tomography (microCT), we report on the neuroanatomy of the nearly complete braincase of an adult individual, as well as the inner ears (endosseous labyrinths) of one other adult and several juveniles (the latter also containing novel vascular cavities). The presence of large and morphologically adult inner ears in juvenile material suggests precociality. Our findings add to the diversity of neurovascular anatomy in sauropod braincases and buttress the perception of sauropods as fast-growing and autonomous giants with manifold facets of reproductive and social behaviour. This suggests that - apart from sheer size - little separated Europasaurus from its large-bodied relatives.
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Affiliation(s)
- Marco Schade
- University of Greifswald, Institute of Geography and Geology, Palaeontology and HistoricalGreifswaldGermany,University of Greifswald, Zoological Institute and Museum, Cytology and Evolutionary BiologyGreifswaldGermany
| | | | - Marie K Hörnig
- University of Greifswald, Zoological Institute and Museum, Cytology and Evolutionary BiologyGreifswaldGermany
| | - Carina Paetzel
- University of Greifswald, Zoological Institute and Museum, Cytology and Evolutionary BiologyGreifswaldGermany
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6
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Fabbri M, Navalón G, Mongiardino Koch N, Hanson M, Petermann H, Bhullar BA. A shift in ontogenetic timing produced the unique sauropod skull. Evolution 2021; 75:819-831. [PMID: 33578446 DOI: 10.1111/evo.14190] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 01/30/2021] [Indexed: 11/29/2022]
Abstract
Sauropod dinosaurs include the largest terrestrial vertebrates that have ever lived. Virtually every part of the sauropod body is heavily modified in association with gigantic size and associated physiological alterations. Sauropod skulls are no exception: they feature elongated, telescoped facial regions connected to tilted neurocrania and reoriented jaw adductor muscles. Several of these cranial features have been suggested to be adaptations for feeding on the one hand and the result of paedomorphic transformation near the base of Sauropoda on the other. However, the scarcity of sauropodomorph ontogenetic series has impeded further investigation of these hypotheses. We re-evaluated the cranial material attributed to the early sauropodomorph Anchisaurus, which our phylogenetic analyses confirm to be closely related to sauropods. Digital assembly of μCT-scanned skulls of the two known specimens, a juvenile and an adult, permitted us to examine the detailed ontogeny of cranial elements. The skull anatomy of Anchisaurus is distinguished by a mosaic of ancestral saurischian and sauropod-like characters. Sauropod-like characters of the braincase and adductor chamber appear late in ontogeny, suggesting that these features first evolved by the developmental mechanism of terminal addition. Shape analyses and investigation of allometric evolution demonstrate that cranial characters that appear late in the ontogeny of sauropodomorphs closely related to sauropods are already present in the embryos and juveniles of sauropods, suggesting a predisplacement-type shift in developmental timing from the ancestral anchisaurian condition. We propose that this developmental shift relaxed prior constraints on skull morphology, allowing sauropods to explore a novel range of phenotypes and enabling specializations of the feeding apparatus. The shift in timing occurred in concert with the evolution of gigantism and physiological and locomotory innovations.
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Affiliation(s)
- Matteo Fabbri
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut, 06511.,Peabody Museum of Natural History, Yale University, New Haven, Connecticut, 06511
| | - Guillermo Navalón
- Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, United Kingdom.,Unidad de Paleontología, Departamento de Biología, Universidad Autónoma de Madrid, Madrid, 28049, Spain
| | - Nicolás Mongiardino Koch
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut, 06511.,Peabody Museum of Natural History, Yale University, New Haven, Connecticut, 06511
| | - Michael Hanson
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut, 06511.,Peabody Museum of Natural History, Yale University, New Haven, Connecticut, 06511
| | - Holger Petermann
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut, 06511.,Peabody Museum of Natural History, Yale University, New Haven, Connecticut, 06511.,Denver Museum of Nature and Science, Denver, Colorado, 80205
| | - Bhart-Anjan Bhullar
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut, 06511.,Peabody Museum of Natural History, Yale University, New Haven, Connecticut, 06511
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7
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Ballell A, King JL, Neenan JM, Rayfield EJ, Benton MJ. The braincase, brain and palaeobiology of the basal sauropodomorph dinosaur Thecodontosaurus antiquus. Zool J Linn Soc 2020. [DOI: 10.1093/zoolinnean/zlaa157] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Sauropodomorph dinosaurs underwent drastic changes in their anatomy and ecology throughout their evolution. The Late Triassic Thecodontosaurus antiquus occupies a basal position within Sauropodomorpha, being a key taxon for documenting how those morphofunctional transitions occurred. Here, we redescribe the braincase osteology and reconstruct the neuroanatomy of Thecodontosaurus, based on computed tomography data. The braincase of Thecodontosaurus shares the presence of medial basioccipital components of the basal tubera and a U-shaped basioccipital–parabasisphenoid suture with other basal sauropodomorphs and shows a distinct combination of characters: a straight outline of the braincase floor, an undivided metotic foramen, an unossified gap, large floccular fossae, basipterygoid processes perpendicular to the cultriform process in lateral view and a rhomboid foramen magnum. We reinterpret these braincase features in the light of new discoveries in dinosaur anatomy. Our endocranial reconstruction reveals important aspects of the palaeobiology of Thecodontosaurus, supporting a bipedal stance and cursorial habits, with adaptations to retain a steady head and gaze while moving. We also estimate its hearing frequency and range based on endosseous labyrinth morphology. Our study provides new information on the pattern of braincase and endocranial evolution in Sauropodomorpha.
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Affiliation(s)
- Antonio Ballell
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - J Logan King
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - James M Neenan
- Oxford University Museum of Natural History, Parks Road, Oxford, UK
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8
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Müller RT, Ferreira JD, Pretto FA, Bronzati M, Kerber L. The endocranial anatomy of Buriolestes schultzi (Dinosauria: Saurischia) and the early evolution of brain tissues in sauropodomorph dinosaurs. J Anat 2020; 238:809-827. [PMID: 33137855 DOI: 10.1111/joa.13350] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 10/05/2020] [Accepted: 10/09/2020] [Indexed: 12/26/2022] Open
Abstract
Our knowledge on the anatomy of the first dinosaurs (Late Triassic, 235-205 Ma) has drastically increased in the last years, mainly due to several new findings of exceptionally well-preserved specimens. Nevertheless, some structures such as the neurocranium and its associated structures (brain, labyrinth, cranial nerves, and vasculature) remain poorly known, especially due to the lack of specimens preserving a complete and articulated neurocranium. This study helps to fill this gap by investigating the endocranial cavity of one of the earliest sauropodomorphs, Buriolestes schultzi, from the Upper Triassic (Carnian-c. 233 Ma) of Brazil. The endocranial anatomy of this animal sheds light on the ancestral condition of the brain of sauropodomorphs, revealing an elongated olfactory tract combined to a relatively small pituitary gland and well-developed flocculus of the cerebellum. These traits change drastically across the evolutionary history of sauropodomorphs, reaching the opposite morphology in Jurassic times. Furthermore, we present here the first calculations of the Reptile Encephalization Quotient (REQ) for a Triassic dinosaur. The REQ of B. schultzi is lower than that of Jurassic theropods, but higher than that of later sauropodomorphs. The combination of cerebral, dental, and postcranial data suggest that B. schultzi was an active small predator, able to track moving prey.
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Affiliation(s)
- Rodrigo T Müller
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria, São João do Polêsine, Brazil
| | - José D Ferreira
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, Brazil
| | - Flávio A Pretto
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria, São João do Polêsine, Brazil.,Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, Brazil
| | - Mario Bronzati
- Laboratório de Evolução e Biologia Integrativa, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - Leonardo Kerber
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria, São João do Polêsine, Brazil.,Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Museu Paraense Emílio Goeldi, Coordenação de Ciências da Terra e Ecologia, Belém, Brazil
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9
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Button DJ, Zanno LE. Repeated Evolution of Divergent Modes of Herbivory in Non-avian Dinosaurs. Curr Biol 2020; 30:158-168.e4. [DOI: 10.1016/j.cub.2019.10.050] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 09/08/2019] [Accepted: 10/25/2019] [Indexed: 01/13/2023]
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10
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Wang Y, Wang T, Yang Z, You H. Cranium and Vertebral Column of
Xingxiulong chengi
(Dinosauria: Sauropodomorpha) from the Early Jurassic of China. Anat Rec (Hoboken) 2019; 303:772-789. [DOI: 10.1002/ar.24305] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 09/05/2019] [Accepted: 09/13/2019] [Indexed: 11/10/2022]
Affiliation(s)
| | - Tao Wang
- Bureau of Land and Resources of Lufeng County Lufeng Yunnan China
| | - Zhi‐Wen Yang
- Bureau of Land and Resources of Lufeng County Lufeng Yunnan China
| | - Hai‐Lu You
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences Beijing China
- CAS Center for Excellence in Life and Paleoenvironment Beijing China
- College of Earth and Planetary Sciences, University of Chinese Academy of Sciences Beijing China
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11
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Bronzati M, Müller RT, Langer MC. Skull remains of the dinosaur Saturnalia tupiniquim (Late Triassic, Brazil): With comments on the early evolution of sauropodomorph feeding behaviour. PLoS One 2019; 14:e0221387. [PMID: 31490962 PMCID: PMC6730896 DOI: 10.1371/journal.pone.0221387] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 08/07/2019] [Indexed: 11/28/2022] Open
Abstract
Saturnalia tupiniquim is a sauropodomorph dinosaur from the Late Triassic (Carnian–c. 233 Ma) Santa Maria Formation of Brazil. Due to its phylogenetic position and age, it is important for studies focusing on the early evolution of both dinosaurs and sauropodomorphs. The osteology of Saturnalia has been described in a series of papers, but its cranial anatomy remains mostly unknown. Here, we describe the skull bones of one of its paratypes (only in the type-series to possess such remains) based on CT Scan data. The newly described elements allowed estimating the cranial length of Saturnalia and provide additional support for the presence of a reduced skull (i.e. two thirds of the femoral length) in this taxon, as typical of later sauropodomorphs. Skull reduction in Saturnalia could be related to an increased efficiency for predatory feeding behaviour, allowing fast movements of the head in order to secure small and elusive prey, a hypothesis also supported by data from its tooth and brain morphology. A principal co-ordinates analysis of the sauropodomorph jaw feeding apparatus shows marked shifts in morphospace occupation in different stages of the first 30 million years of their evolutionary history. One of these shifts is observed between non-plateosaurian and plateosaurian sauropodomorphs, suggesting that, despite also having an omnivorous diet, the feeding behaviour of some early Carnian sauropodomorphs, such as Saturnalia, was markedly different from that of later Triassic taxa. A second shift, between Late Triassic and Early Jurassic taxa, is congruent with a floral turnover hypothesis across the Triassic-Jurassic boundary.
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Affiliation(s)
- Mario Bronzati
- Laboratório de Paleontologia, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
- * E-mail: (MB); (MCL)
| | - Rodrigo T. Müller
- Centro de Apoio à Pesquisa Paleontológica, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brazil
| | - Max C. Langer
- Laboratório de Paleontologia, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
- * E-mail: (MB); (MCL)
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12
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Bullar CM, Zhao Q, Benton MJ, Ryan MJ. Ontogenetic braincase development in Psittacosaurus lujiatunensis (Dinosauria: Ceratopsia) using micro-computed tomography. PeerJ 2019; 7:e7217. [PMID: 31428535 PMCID: PMC6698140 DOI: 10.7717/peerj.7217] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 05/31/2019] [Indexed: 11/20/2022] Open
Abstract
Ontogenetic sequences are relatively rare among dinosaurs, with Ceratopsia being one of the better represented clades, and especially among geologically earlier forms, such as Psittacosaurus. Psittacosaurus is a small, bipedal basal ceratopsian abundant in the Lower Cretaceous deposits of Asia, whose cranial and endocranial morphology has been well studied, but only cursory details have been published on the bones surrounding the brain. Using reconstructions created from micro-computed tomography scans of well-preserved skulls from the Barremian–Aptian Yixian Formation, China, we document morphological changes in the braincase of Psittacosaurus lujiatunensis through three growth stages, hatchling, juvenile, and adult, thus providing the first detailed study of ceratopsian braincase morphology through ontogeny. Notable ontogenetic changes in the braincase of P. lujiatunensis include a dramatic relative reduction in size of the supraoccipital, an increase in the lateral expansion of the paroccipital processes and a decrease in the angle between the lateral semicircular canal and the palatal plane. These ontogenetic morphological changes in the braincase relate to expansion of the cranium and brain through growth, as well as reflecting the switch from quadrupedal juveniles to bipedal adults as documented in the changing orientation of the horizontal semicircular canal through ontogeny. Recognition of these patterns in a basal ceratopsian has implications for understanding key events in later ceratopsian evolution, such as the development of the parieto-squamosal frill in derived neoceratopsians.
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Affiliation(s)
- Claire M Bullar
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - Qi Zhao
- School of Earth Sciences, University of Bristol, Bristol, UK.,Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
| | | | - Michael J Ryan
- Department of Earth Sciences, Carleton University, Ottawa, ON, Canada
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13
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Chapelle KE, Barrett PM, Botha J, Choiniere JN. Ngwevu intloko: a new early sauropodomorph dinosaur from the Lower Jurassic Elliot Formation of South Africa and comments on cranial ontogeny in Massospondylus carinatus. PeerJ 2019; 7:e7240. [PMID: 31403001 PMCID: PMC6687053 DOI: 10.7717/peerj.7240] [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: 03/25/2019] [Accepted: 06/03/2019] [Indexed: 11/24/2022] Open
Abstract
Our knowledge of Early Jurassic palaeobiodiversity in the upper Elliot Formation of South Africa has increased markedly in recent years with the discovery of new fossils, re-assessments of previously collected material and a better understanding of Stormberg Group stratigraphy. Here, Ngwevu intloko, a new genus of upper Elliot basal sauropodomorph is named on the basis of a complete skull and partial skeleton (BP/1/4779) previously assigned to Massospondylus carinatus. It can be distinguished from all other basal sauropodomorphs by a combination of 16 cranial and six postcranial characters. The new species is compared to a small ontogenetic series of M. carinatus as well as to a range of closely related taxa. Taphonomic deformation, sexual dimorphism and ontogeny are rejected as possible explanations for the morphological differences present between BP/1/4779 and other taxa. Osteohistological examination reveals that BP/1/4779 had nearly reached adult size at the time of its death at a minimum age of 10 years.
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Affiliation(s)
- Kimberley E.J. Chapelle
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
- School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Paul M. Barrett
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
- Department of Earth Sciences, Natural History Museum, London, United Kingdom
| | - Jennifer Botha
- Department of Karoo Palaeontology, National Museum, Bloemfontein, South Africa
- Department of Zoology and Entomology, University of the Free State, Bloemfontein, South Africa
| | - Jonah N. Choiniere
- Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa
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14
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Zhang Q, Wang T, Yang Z, You H. Redescription of the Cranium of
Jingshanosaurus xinwaensis
(Dinosauria: Sauropodomorpha) from the Lower Jurassic Lufeng Formation of Yunnan Province, China. Anat Rec (Hoboken) 2019; 303:759-771. [DOI: 10.1002/ar.24113] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 12/02/2018] [Accepted: 12/25/2018] [Indexed: 11/09/2022]
Affiliation(s)
- Qian‐Nan Zhang
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of Sciences 142 Xizhimenwai Street Beijing 100044 China
- CAS Center for Excellence in Life and Paleoenvironment 142 Xizhimenwai Street Beijing 100044 China
- College of Earth and Planetary SciencesUniversity of Chinese Academy of Sciences 19A Yüquan Road Beijing 100049 China
| | - Tao Wang
- Bureau of Land and Resources of Lufeng County Yunnan Province 651299 China
| | - Zhi‐Wen Yang
- Bureau of Land and Resources of Lufeng County Yunnan Province 651299 China
| | - Hai‐Lu You
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of Sciences 142 Xizhimenwai Street Beijing 100044 China
- CAS Center for Excellence in Life and Paleoenvironment 142 Xizhimenwai Street Beijing 100044 China
- College of Earth and Planetary SciencesUniversity of Chinese Academy of Sciences 19A Yüquan Road Beijing 100049 China
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15
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Langer MC, McPhee BW, Marsola JCDA, Roberto-da-Silva L, Cabreira SF. Anatomy of the dinosaur Pampadromaeus barberenai (Saurischia-Sauropodomorpha) from the Late Triassic Santa Maria Formation of southern Brazil. PLoS One 2019; 14:e0212543. [PMID: 30785940 PMCID: PMC6382151 DOI: 10.1371/journal.pone.0212543] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 02/05/2019] [Indexed: 11/19/2022] Open
Abstract
Sauropodomorphs are the most abundant and diverse clade of Triassic dinosaurs, but the taxonomy of their earliest (Carnian) representatives is still poorly understood. One such taxon is Pampadromaeus barberenai, represented by a nearly complete disarticulated skeleton recovered from the upper part of the Santa Maria Formation of Rio Grande do Sul, Brazil. Here, the osteology of Pam. barberenai is fully described for the first time. Detailed comparisons with other Carnian sauropodomorphs reveal a unique anatomy, corroborating its status as a valid species. Potential autapomorphies of Pam. barberenai can be seen in the articulation of the sacral zygapophyses, the length of the pectoral epipodium, the shape of the distal articulation of the femur and the proximal articulation of metatarsal 1. A novel phylogenetic study shows that relationships among the Carnian sauropodomorphs are poorly constrained, possibly because they belong to a "zone of variability", where homoplasy abounds. Yet, there is some evidence that Pam. barberenai may nest within Saturnaliidae, along with Saturnalia tupiniquim and Chromogisaurus novasi, which represents the sister group to the larger sauropodomorphs, i.e. Bagualosauria.
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Affiliation(s)
- Max Cardoso Langer
- Laboratório de Paleontologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto-SP, Brazil
| | - Blair Wayne McPhee
- Laboratório de Paleontologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto-SP, Brazil
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16
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Marsh AD, Rowe TB. Anatomy and systematics of the sauropodomorph Sarahsaurus aurifontanalis from the Early Jurassic Kayenta Formation. PLoS One 2018; 13:e0204007. [PMID: 30304035 PMCID: PMC6179219 DOI: 10.1371/journal.pone.0204007] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 09/01/2018] [Indexed: 12/13/2022] Open
Abstract
Sarahsaurus aurifontanalis, from the Kayenta Formation of Arizona, is one of only three sauropodomorph dinosaurs known from the Early Jurassic of North America. It joins Anchisaurus polyzelus, from the older Portland Formation of the Hartford Basin, and Seitaad reussi, from the younger Navajo Sandstone of Utah, in representing the oldest North American sauropodomorphs. If it is true that sauropodomorphs were absent from North America during the Late Triassic, the relationship among these three dinosaurs offers a test of the mechanisms that drove recovery in North American biodiversity following the end-Triassic extinction event. Here we provide the first thorough description of Sarahsaurus aurifontanalis based on completed preparation and computed tomographic imaging of the holotype and referred specimens. With new anatomical data, our phylogenetic analysis supports the conclusion that Sarahsaurus aurifontanalis is nested within the primarily Gondwanan clade Massospondylidae, while agreeing with previous analyses that the three North American sauropodomorphs do not themselves form an exclusive clade. A revised diagnosis and more thorough understanding of the anatomy of Sarahsaurus aurifontanalis support the view that independent dispersal events were at least partly responsible for the recovery in North American vertebrate diversity following a major extinction event.
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Affiliation(s)
- Adam D. Marsh
- The Jackson School of Geosciences, University of Texas at Austin, Austin, Texas, United States of America
- Division of Science and Resource Management, Petrified Forest National Park, Arizona, United States of America
| | - Timothy B. Rowe
- The Jackson School of Geosciences, University of Texas at Austin, Austin, Texas, United States of America
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17
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Yin YL, Pei R, Zhou CF. Cranial morphology of Sinovenator changii (Theropoda: Troodontidae) on the new material from the Yixian Formation of western Liaoning, China. PeerJ 2018; 6:e4977. [PMID: 29942679 PMCID: PMC6015489 DOI: 10.7717/peerj.4977] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 05/24/2018] [Indexed: 11/20/2022] Open
Abstract
A new three-dimensionally preserved troodontid specimen consisting of most of the skull, partial mandibles and six articulated cervical vertebrae (PMOL-AD00102) from the Early Cretaceous Yixian Formation of Beipiao, western Liaoning, China is identified as Sinovenator changii on the basis of a surangular with a “T”-shaped cross-section. High-resolution computed tomographic data for the skull of this new specimen facilitated a detailed description of the cranial anatomy of S. changii. New diagnostic features of S. changii include a well-developed medial shelf on the jugal, a slender bar in the parasphenoid recess, a lateral groove on the pterygoid flange of the ectopterygoid, and the lateral surface of the anterior cervical vertebrae bearing two pneumatic foramina. Our new observation confirms that the braincase of Sinovenator is not as primitive as previously suggested, although it still shows an intermediate state between derived troodontids and non-troodontid paravians in having an initial stage of the subotic recess and the otosphenoidal crest. Additionally, this new specimen reveals some novel and valuable anatomical information of troodontids regarding the quadrate-quadratojugal articulation, the stapes, the epipterygoid and the atlantal ribs.
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Affiliation(s)
- Ya-Lei Yin
- Paleontological Institute, Shenyang Normal University, Shenyang, Liaoning, China
| | - Rui Pei
- Department of Earth Sciences, the University of Hong Kong, Hong Kong, China
| | - Chang-Fu Zhou
- College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, Shandong, China
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18
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Moore AJ, Mo J, Clark JM, Xu X. Cranial anatomy of Bellusaurus sui (Dinosauria: Eusauropoda) from the Middle-Late Jurassic Shishugou Formation of northwest China and a review of sauropod cranial ontogeny. PeerJ 2018; 6:e4881. [PMID: 29868283 PMCID: PMC5985764 DOI: 10.7717/peerj.4881] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 05/10/2018] [Indexed: 11/20/2022] Open
Abstract
Bellusaurus sui is an enigmatic sauropod dinosaur from the Middle-Late Jurassic Shishugou Formation of northwest China. Bellusaurus is known from a monospecific bonebed preserving elements from more than a dozen juvenile individuals, including numerous bones of the skull, providing rare insight into the cranial anatomy of juvenile sauropods. Here, we present a comprehensive description of the cranial anatomy of Bellusaurus, supplementing the holotypic cranial material with additional elements recovered from recent joint Sino-American field expeditions. Bellusaurus is diagnosed by several unique autapomorphies, including a neurovascular foramen piercing the ascending process of the maxilla at midheight, the frontal process of the nasal extending farther posteriorly onto the frontal than the prefrontal, and U-shaped medial and lateral notches in the posterior margin of the ventral process of the squamosal. Several features identified here, including a preantorbital opening in the maxilla, a stepped dorsal margin of the vomerine process of the pterygoid, and the partitioning of the dorsal midline endocranial fossae associated with the dural venous sinuses into anterior and posterior components by a transverse ridge of the parietal, are consistent with recent phylogenetic hypotheses that recover Bellusaurus as a basal macronarian or close relative of Neosauropoda. We review the current state of knowledge of sauropod cranial ontogeny, placing several aspects of the cranial anatomy of Bellusaurus in an ontogenetic context and providing explicit hypotheses of ontogenetic transformations that can be tested by future discoveries of ontogenetic variants of sauropod skulls. While scoring ontogenetically variable characters as unknown may help to alleviate the biasing effects of ontogeny on the phylogenetic position of juvenile specimens, we caution that this approach may remove phylogenetically informative character information, and argue that inference methods that are known to be less sensitive to homoplasy than equal weights parsimony (i.e., implied weights parsimony; Bayesian approaches) should also be employed.
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Affiliation(s)
- Andrew J Moore
- Department of Biological Sciences, George Washington University, Washington, DC, USA
| | - Jinyou Mo
- Natural History Museum of Guangxi Zhuang Autonomous Region, Nanning, China
| | - James M Clark
- Department of Biological Sciences, George Washington University, Washington, DC, USA
| | - Xing Xu
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
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