Osteohistology and microanatomy of a new specimen of Cearachelys placidoi (Testudines: Pleurodira) a side‐necked turtle from the lower Cretaceous of Brazil

Abstract

Pelomedusoides had a recognised diverse Early Cretaceous fauna of turtles in Northeast Brazil. Within them, the bothremydid Cearachelys placidoi has a relatively abundant record. This diversity contrasts with the scarcity of osteohistological studies in this group. The relatively well-preserved 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 fiber 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.

An early bothremydid from the Arlington Archosaur Site of Texas

“…See "Supplementary Information" for full histological description. The results of our histological analysis are largely consistent with other known bothremydid taxa, which have a significantly thicker external than internal cortex 45,46 . The predominance of woven bone suggests fast skeletal growth, a derived characteristic www.nature.com/scientificreports/ seen in C. placidoi and the extant pleurodiran genus Phrynops 46,47 .…”

“…The predominance of woven bone suggests fast skeletal growth, a derived characteristic www.nature.com/scientificreports/ seen in C. placidoi and the extant pleurodiran genus Phrynops 46,47 . In contrast, extinct and extant cryptodires and the Cretaceous chelid Linderochelys rinconensis exhibit greater parallel-fibered bone, characteristic of a slower growth rate and a more conservative osteohistological pattern 46,[48][49][50][51][52][53] .…”

Osteohistological characterization of notosuchian osteoderms: Evidence for an overlying thick leathery layer of skin

“…The osteoderms of Uberabasuchus terrificus , Itasuchus jesuinoi , Armadillosuchus arrudai , Mariliasuchus amarali , and Baurusuchidae indet. (LPRP/USP 0642) have basal cortices similar to those of aetosaurs, other pseudosuchian, and turtle shell plates (Scheyer et al, 2007 ; Sena et al, 2020 ., 2021 ). They are composed of parallel‐fibered bone tissue poorly vascularized interrupted by growth marks.…”

“…indet. (LPRP/USP 0642) have basal cortices similar to those of aetosaurs, other pseudosuchian, and turtle shell plates Sena et al, 2020Sena et al, ., 2021. They are composed of parallelfibered bone tissue poorly vascularized interrupted by growth marks.…”

Overview of special issue on current advances in Brazilian biomedical and anatomical sciences

“…“Osteohistology and microanatomy of a new specimen of Cearachelys placidoi (Testudines: Pleurodira) a side‐necked turtle from the Lower Cretaceous of Brazil” (Sena et al, 2021) was developed in a collaboration among authors from institutions located in Brazilian states: Pernambuco (Federal University of Pernambuco, Department of Geological Sciences and Vitória de Santo Antão University Center); Ceará (Paleontology Lab—Regional University of Cariri); Rio de Janeiro Laboratory of Peleobiology and Paleography—National Museum of the Federal University of Rio de Janeiro). It explores the histological characteristics of the shell of the costal marine C. placidoi from the Aptian age of the Araripe Basin, in a comparative study with the fresh water turtles Phrynops sp.…”