Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny

Background. Macelognathus vagans Marsh, 1884 from the Late Jurassic Morrison Fm. of Wyoming was originally described as a dinosaur by Marsh and in 1971 Ostrom suggested crocodilian affinities. In 2005, Göhlich and collaborators identified new material of this species from Colorado as a basal crocody...

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Autores principales: Leardi, J.M., Pol, D., Clark, J.M.
Formato: JOUR
Materias:
Braincase
Crocodylomorpha
Late jurassic
Micro CT
Phylogeny
anatomy
archosaur
Argentina
bear
cladistics
dorsal region
human
human tissue
mandible
marsh
micro-computed tomography
nonhuman
parietal bone
relative
sampling
sister group
Upper Jurassic
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_21678359_v2017_n1_p_Leardi
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_21678359_v2017_n1_p_Leardi2023-10-03T16:39:39Z Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny Leardi, J.M. Pol, D. Clark, J.M. Braincase Crocodylomorpha Late jurassic Micro CT Phylogeny anatomy archosaur Argentina bear cladistics dorsal region human human tissue mandible marsh micro-computed tomography nonhuman parietal bone relative sampling sister group Upper Jurassic Background. Macelognathus vagans Marsh, 1884 from the Late Jurassic Morrison Fm. of Wyoming was originally described as a dinosaur by Marsh and in 1971 Ostrom suggested crocodilian affinities. In 2005, Göhlich and collaborators identified new material of this species from Colorado as a basal crocodylomorph. However, a partial skull found in association with mandibular and postcranial remains was not described. Methods. Due to the small size and delicate structures within the braincase, micro CT studies were performed on this specimen. The new anatomical information was incorporated in a phylogenetic dataset, expanding both character and taxon sampling. Results. This new material reinforces the non-crocodyliform crocodylomorph affinities of Macelognathus as it bears a large otic aperture, unfused frontals and lacks ornamentation on the dorsal cranial bones. The internal structures also support these affinities as this specimen bears traits (i.e., heavily pneumatized and expanded basisphenoid; the presence of additional pneumatic features on the braincase; and the otoccipitalquadrate contact) not present in most basal crocodylomorphs. Furthermore, the presence of a wide supraoccipital and a cranioquadrate passage are traits shared with Almadasuchus from the early Late Jurassic of Argentina. Macelognathus was recovered as one of the closest relatives of crocodyliforms, forming a clade (Hallopodidae) with two other Late Jurassic taxa (Almadasuchus and Hallopus). Discussion. The clade formed by Almadasuchus C Hallopus C Macelognathus, the Hallopodidae, is characterized by a higher degree of suturing of the braincase, posteriorly closed otic aperture (paralleled in mesoeucrocodylians) and cursorial adaptations. Also, the phylogenetic position of this lineage of derived crocodylomorphs as the sister group of Crocodyliformes implies a large amount of unsampled record (ghost lineage), at least 50 million years. © 2017 Leardi et al. Fil:Leardi, J.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Pol, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_21678359_v2017_n1_p_Leardi
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Braincase
Crocodylomorpha
Late jurassic
Micro CT
Phylogeny
anatomy
archosaur
Argentina
bear
cladistics
dorsal region
human
human tissue
mandible
marsh
micro-computed tomography
nonhuman
parietal bone
relative
sampling
sister group
Upper Jurassic
spellingShingle Braincase
Crocodylomorpha
Late jurassic
Micro CT
Phylogeny
anatomy
archosaur
Argentina
bear
cladistics
dorsal region
human
human tissue
mandible
marsh
micro-computed tomography
nonhuman
parietal bone
relative
sampling
sister group
Upper Jurassic
Leardi, J.M.
Pol, D.
Clark, J.M.
Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny
topic_facet Braincase
Crocodylomorpha
Late jurassic
Micro CT
Phylogeny
anatomy
archosaur
Argentina
bear
cladistics
dorsal region
human
human tissue
mandible
marsh
micro-computed tomography
nonhuman
parietal bone
relative
sampling
sister group
Upper Jurassic
description Background. Macelognathus vagans Marsh, 1884 from the Late Jurassic Morrison Fm. of Wyoming was originally described as a dinosaur by Marsh and in 1971 Ostrom suggested crocodilian affinities. In 2005, Göhlich and collaborators identified new material of this species from Colorado as a basal crocodylomorph. However, a partial skull found in association with mandibular and postcranial remains was not described. Methods. Due to the small size and delicate structures within the braincase, micro CT studies were performed on this specimen. The new anatomical information was incorporated in a phylogenetic dataset, expanding both character and taxon sampling. Results. This new material reinforces the non-crocodyliform crocodylomorph affinities of Macelognathus as it bears a large otic aperture, unfused frontals and lacks ornamentation on the dorsal cranial bones. The internal structures also support these affinities as this specimen bears traits (i.e., heavily pneumatized and expanded basisphenoid; the presence of additional pneumatic features on the braincase; and the otoccipitalquadrate contact) not present in most basal crocodylomorphs. Furthermore, the presence of a wide supraoccipital and a cranioquadrate passage are traits shared with Almadasuchus from the early Late Jurassic of Argentina. Macelognathus was recovered as one of the closest relatives of crocodyliforms, forming a clade (Hallopodidae) with two other Late Jurassic taxa (Almadasuchus and Hallopus). Discussion. The clade formed by Almadasuchus C Hallopus C Macelognathus, the Hallopodidae, is characterized by a higher degree of suturing of the braincase, posteriorly closed otic aperture (paralleled in mesoeucrocodylians) and cursorial adaptations. Also, the phylogenetic position of this lineage of derived crocodylomorphs as the sister group of Crocodyliformes implies a large amount of unsampled record (ghost lineage), at least 50 million years. © 2017 Leardi et al.
format JOUR
author Leardi, J.M.
Pol, D.
Clark, J.M.
author_facet Leardi, J.M.
Pol, D.
Clark, J.M.
author_sort Leardi, J.M.
title Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny
title_short Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny
title_full Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny
title_fullStr Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny
title_full_unstemmed Detailed anatomy of the braincase of Macelognathus vagans Marsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny
title_sort detailed anatomy of the braincase of macelognathus vagans marsh, 1884 (archosauria, crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny
url http://hdl.handle.net/20.500.12110/paper_21678359_v2017_n1_p_Leardi
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AT pold detailedanatomyofthebraincaseofmacelognathusvagansmarsh1884archosauriacrocodylomorphausinghighresolutiontomographyandnewinsightsonbasalcrocodylomorphphylogeny
AT clarkjm detailedanatomyofthebraincaseofmacelognathusvagansmarsh1884archosauriacrocodylomorphausinghighresolutiontomographyandnewinsightsonbasalcrocodylomorphphylogeny
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