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Foffa D, Nesbitt SJ, Butler RJ, Brusatte SL, Walsh S, Fraser NC, Barrett PM. The osteology of the Late Triassic reptile Scleromochlus taylori from μCT data. Anat Rec (Hoboken) 2024; 307:1113-1146. [PMID: 37846180 DOI: 10.1002/ar.25335] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 09/10/2023] [Accepted: 09/18/2023] [Indexed: 10/18/2023]
Abstract
Scleromochlus taylori is one of the most enigmatic members of the herpetofauna from the Lossiemouth Sandstone Formation (Upper Triassic) of Elgin (Moray, Scotland). For many years it was thought to be closely related to pterosaurs and dinosaurs, but the anatomy of this animal is difficult to interpret because of the notoriously poor preservation of the six available specimens, which comprise void space in the sandstone after the bones were destroyed by diagenesis. Historically, these fossils have been studied using physical molds, which provide only incomplete, and potentially distorted, information. Due to these uncertainties, interpretations of the anatomy, phylogenetic relationships, and paleobiology of Scleromochlus taylori have remained contentious. Here, we use microcomputed tomographic (μCT) techniques to redescribe and illustrate the osteology of Scleromochlus in detail, building upon a short redescription of keystone features of the anatomy that we recently published. We digitally visualize, describe, and figure previously inaccessible-and thus unaltered-portions of its skeleton, as well as providing new observations on the exposed parts of each specimen. This work reveals many novel features of the skull, mandible, trunk, tail, girdles, forelimb, and hindlimb (particularly of the manus, femur, and pes), demonstrating that historic molding techniques failed, in some cases, to accurately capture the anatomy of Scleromochlus. Our review sheds light on some of the most controversial aspects of Scleromochlus morphology showing that this taxon retains plesiomorphic features of Avemetatarsalia in the postcranial skeleton, alongside a suite of synapomorphies diagnostic of pterosauromorphs (the broad clade of pterosaurs and taxa more closely related to them than dinosaurs), particularly one subgroup, the lagerpetids. Consistent with recent work, our updated phylogenetic analyses (Maximum Parsimony and Bayesian Inference) demonstrate that Scleromochlus taylori is an avemetatarsalian archosaur that is recovered firmly in an early diverging position within Pterosauromorpha, as a member of Lagerpetidae, thus shedding important information on the origin of pterosaurs, the first group of vertebrates to evolve powered flight.
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Affiliation(s)
- Davide Foffa
- Department of Natural Sciences, National Museums Scotland, Edinburgh, UK
- Department of Geosciences, Virginia Tech, Blacksburg, Virginia, USA
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
| | | | - Richard J Butler
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
| | - Stephen L Brusatte
- Department of Natural Sciences, National Museums Scotland, Edinburgh, UK
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, UK
| | - Stig Walsh
- Department of Natural Sciences, National Museums Scotland, Edinburgh, UK
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, UK
| | - Nicholas C Fraser
- Department of Natural Sciences, National Museums Scotland, Edinburgh, UK
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, UK
| | - Paul M Barrett
- Fossil Reptiles, Amphibians and Birds Section, Natural History Museum, London, UK
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Garcia MS, Cabreira SF, da Silva LR, Pretto FA, Müller RT. A saurischian (Archosauria, Dinosauria) ilium from the Upper Triassic of southern Brazil and the rise of Herrerasauria. Anat Rec (Hoboken) 2024; 307:1011-1024. [PMID: 37971103 DOI: 10.1002/ar.25342] [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: 08/01/2023] [Revised: 09/21/2023] [Accepted: 10/03/2023] [Indexed: 11/19/2023]
Abstract
The Carnian (Upper Triassic) rocks of the Candelária Sequence present a rich record of dinosaurs, including some of the oldest known dinosaurs worldwide. In this contribution we describe the first unequivocal dinosaur from the Pivetta site, located in the Restinga Sêca municipality, Southern Brazil. The specimen CAPPA/UFSM 0373 is an isolated but well-preserved left ilium. A thorough examination of the specimen's anatomy and a phylogenetic analysis provides evidence that CAPPA/UFSM 0373 belongs to the Herrerasauria. We were able to identify several similarities with potential non-herrerasaurid herrerasaurians (e.g., Tawa hallae, "Caseosaurus crosbyensis"), which were previously only known from North American deposits. In contrast, herrerasaurids (e.g., Herrerasaurus ischigualastensis) are almost exclusively known from South America. Our results support the nesting of CAPPA/UFSM 0373 as an early-diverging herrerasaurian. Furthermore, this is potentially the first record of a non-herrerasaurid herrerasaurian in unambiguous Carnian beds, suggesting a hidden diversity of dinosaurs in the Carnian rocks of the Candelária Sequence, which can be revealed even by fragmentary specimens.
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Affiliation(s)
- Mauricio Silva Garcia
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brazil
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria, São João do Polêsine, Rio Grande do Sul, Brazil
| | | | | | - Flávio Augusto Pretto
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brazil
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria, São João do Polêsine, Rio Grande do Sul, Brazil
| | - Rodrigo Temp Müller
- Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brazil
- Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria, São João do Polêsine, Rio Grande do Sul, Brazil
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Griffin CT, Stocker MR, Colleary C, Stefanic CM, Lessner EJ, Riegler M, Formoso K, Koeller K, Nesbitt SJ. Assessing ontogenetic maturity in extinct saurian reptiles. Biol Rev Camb Philos Soc 2020; 96:470-525. [PMID: 33289322 DOI: 10.1111/brv.12666] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 10/09/2020] [Accepted: 10/28/2020] [Indexed: 01/06/2023]
Abstract
Morphology forms the most fundamental level of data in vertebrate palaeontology because it is through interpretations of morphology that taxa are identified, creating the basis for broad evolutionary and palaeobiological hypotheses. Assessing maturity is one of the most basic aspects of morphological interpretation and provides the means to study the evolution of ontogenetic changes, population structure and palaeoecology, life-history strategies, and heterochrony along evolutionary lineages that would otherwise be lost to time. Saurian reptiles (the least-inclusive clade containing Lepidosauria and Archosauria) have remained an incredibly diverse, numerous, and disparate clade through their ~260-million-year history. Because of the great disparity in this group, assessing maturity of saurian reptiles is difficult, fraught with methodological and terminological ambiguity. We compiled a novel database of literature, assembling >900 individual instances of saurian maturity assessment, to examine critically how saurian maturity has been diagnosed. We review the often inexact and inconsistent terminology used in saurian maturity assessment (e.g. 'juvenile', 'mature') and provide routes for better clarity and cross-study coherence. We describe the various methods that have been used to assess maturity in every major saurian group, integrating data from both extant and extinct taxa to give a full account of the current state of the field and providing method-specific pitfalls, best practices, and fruitful directions for future research. We recommend that a new standard subsection, 'Ontogenetic Assessment', be added to the Systematic Palaeontology portions of descriptive studies to provide explicit ontogenetic diagnoses with clear criteria. Because the utility of different ontogenetic criteria is highly subclade dependent among saurians, even for widely used methods (e.g. neurocentral suture fusion), we recommend that phylogenetic context, preferably in the form of a phylogenetic bracket, be used to justify the use of a maturity assessment method. Different methods should be used in conjunction as independent lines of evidence when assessing maturity, instead of an ontogenetic diagnosis resting entirely on a single criterion, which is common in the literature. Critically, there is a need for data from extant taxa with well-represented growth series to be integrated with the fossil record to ground maturity assessments of extinct taxa in well-constrained, empirically tested methods.
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Affiliation(s)
- Christopher T Griffin
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
| | - Michelle R Stocker
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
| | - Caitlin Colleary
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Vertebrate Paleontology, Cleveland Museum of Natural History, 1 Wade Oval Drive, Cleveland, OH, 44106, U.S.A
| | - Candice M Stefanic
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Anatomical Sciences, Stony Brook University, 100 Nicolls Road, Stony Brook, NY, 11794, U.S.A
| | - Emily J Lessner
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Pathology and Anatomical Sciences, University of Missouri, 1 Hospital Drive, Columbia, MO, 65212, U.S.A
| | - Mitchell Riegler
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL, 32611, U.S.A
| | - Kiersten Formoso
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Earth Sciences, University of Southern California, 3651 Trousdale Pkwy, Los Angeles, CA, 90089, U.S.A
- Dinosaur Institute, Natural History Museum of Los Angeles County, 900 W Exposition Boulevard, Los Angeles, CA, 90007, U.S.A
| | - Krista Koeller
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Biology, University of Florida, 220 Bartram Hall, Gainesville, FL, 32611, U.S.A
| | - Sterling J Nesbitt
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
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