Re: [dinosaur] Muiscasaurus an ophthalmosaurine + Cearachelys (Pleurodira) osteohistology

Oops...

I just noticed that there was a problem (copy-paste or something else) and the turtle ref did not show up.

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Mariana ValÃria de AraÃjo Sena, Renan Alfredo Machado Bantim, AntÃnio Ãlamo Feitosa Saraiva, Juliana Manso SayÃo Â& Gustavo Ribeiro Oliveira (2020)
Osteohistology and microanatomy of a new specimen of Cearachelys placidoi (Testudines: Pleurodira) a sideânecked turtle from the Lower Cretaceous of Brazil.
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.24556
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.24556

Pelomedusoides had a recognised diverse Early Cretaceous fauna of turtles in Northeast Brazil. Within them, the bothremydids Cearachelys placidoi has a relatively abundant record. This diversity contrasts with the scarcity of osteohistological studies in this group. The relatively wellâpreserved shell of C. placidoi (UFRPE 5600), from the Aptian age of Araripe Basin, is studied here for the purpose of filling this gap. We performed the osteohistological description of the plastron of a new specimen of C. placidoi. Also, to conduct a comparative study, we carried out histological sections in bones of the recent chelid Phrynops sp. Our histological findings indicate similarities between the histological pattern of freshwater turtles and the coastal marine C. placidoi. Moreover, osteohistological features imply metaplastic incorporation of dermal interwoven structural fibre bundles. Lastly, the xiphiplastron of C. placidoi shows an increase of bone compactness over its craniocaudal axis. This microanatomical feature is exclusive to Cearachelys so far.

On Mon, Oct 26, 2020 at 8:32 PM Ben Creisler <bcreisler@gmail.com> wrote:

Ben Creisler
bcreisler@gmail.com

New papers:

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MarÃa EurÃdice PÃramo-Fonseca, Javier GarcÃa Guerrero, Cristian David Benavides-Cabra, Santiago Padilla Bernal & Antonio JosÃ CastaÃeda-GÃmez (2020)
A benchmark specimen of Muiscasaurus catheti from the Upper Aptian of Villa De Leiva, Colombia: new anatomical features and phylogenetic implications.
Cretaceous Research 104685 (advance online publication)
doi: https://doi.org/10.1016/j.cretres.2020.104685
https://www.sciencedirect.com/science/article/abs/pii/S0195667120303724

Highlights

A benchmark specimen for the species Muiscasaurus catheti is described.
Two new autapomorphies of the M. catheti are identified.
New morphological features of M. catheti are revealed.
M. catheti is recovered within Ophthalmosaurinae.
M. catheti is not a Platypterygiinae as was suggested in previous works.
The Ophthalmosaurines are now recorded up to the Aptian in South America.

Abstract

A new specimen of Muiscasaurus catheti Maxwell et al., 2016 from upper Aptian of the Paja Formation found in Villa de Leiva (BoyacÃ, Colombia) is described herein. It consists of a well preserved skull and a nearly complete axial skeleton of a sub-adult individual and provides valuable new morphological information on the species, including two autapomorphies: the presence of a quadratojugal with extremely reduced external exposure, and basioccipital floor of the foramen magnum with a medially furrowed anterior ridge. A detailed comparison between the new specimen (FCG-CBP-16) and the holotype (CIP-FCG-CBP-74) allows us to identify misinterpretations in the original description of M. catheti that were probably due to the highly deformed and partially unprepared state of the holotype. Consequently, we propose the new specimen (FCG-CBP-16) to be a benchmark specimen for the species. Morphological comparisons with other Ophthalmosauridae highlight the affinities between M. catheti and the species of the Upper Jurassic genus Ophthalmosaurus. A phylogenetic analysis recovers M. catheti in a 'basal' position within Ophthalmosaurinae, supporting its proximity to Ophthalmosaurus and contrasting with previous topologies where M. catheti was recovered as a basal Platypterygiinae. This implies a temporal extension of the Ophthalmosaurinae up to the Aptian in South America.

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