Paleohistology and Lifestyle Inferences of a Dyrosaurid (Archosauria: Crocodylomorpha) from Paraíba Basin (Northeastern Brazil)

Abstract

Among the few vertebrates that survived the mass extinction event documented at the Cretaceous–Paleocene boundary are dyrosaurid crocodylomorphs. Surprisingly, there is little information regarding the bone histology of dyrosaurids, despite their relatively common occurrence in the fossil record, and the potential to gain insight about their biology and lifestyle. We provide the first description of the long bone histology of the dyrosaurids. Specimens were collected from the Maria Farinha Formation, in the Paraíba Basin of northeast Brazil. Thin sections of a right femur and left tibia were made. In the left tibia, the cortex consists of lamellar-zonal bone with five lines of arrested growth (LAGs), spaced ∼300 µm apart. The tibia contains a small to medium-sized organized vascular network of both simple vascular canals and primary osteons that decrease in density periostially. The femur exhibits a similar histological pattern overall but has double-LAGs, and an EFS layer (the latter is rare in living crocodylians). Secondary osteons occur in the deep cortex near and inside the spongiosa as a result of remodeling in both bones. This tissue pattern is fairly common among slow-growing animals. These specimens were a sub-adult and a senescent. Patterns in the distribution of bone consistent with osteosclerosis suggest that these animals probably hada fast-swimming ecology. Although these results are consistent with the histology in anatomically convergent taxa, it will be necessary to make additional sections from the mid-diaphysis in order to assign their ecology.

New dyrosaurid remains (Crocodyliformes, Mesoeucrocodylia) from the Paleocene of the Paraíba Basin, NE Brazil

“…This is likely due to adaptations of G. munizi and similar dyrosaurids to a semi-aquatic life and fast swimming (Andrade & Sayão, 2014), and the development of the specialized feeding apparatus of longirostrine dyrosaurids. The tubular rostrum would have created less resistance in water when catching prey.…”

Biomechanical and physiological influences on the osteohistological deposition of Anhangueria (Pterosauria, Pterodactyloidea)

“…A considerable number of previous studies with many types of vertebrate fossils noted that the microstructure of bone throughout the skeleton varies according to the bone and its location in the skeleton (Enlow, 1969;Sayão, 2003;Chinsamy et al, 2009;Werning, 2012;Andrade & Sayão, 2014). Furthermore, the general morphology and biomechanical function of a particular bone element affect the type of bone that will be present (Francillon-Vieillot et al, 1990;Chinsamy-Turan, 2005;Werning, 2012).…”

“…To understand this mechanism and other related paleobiological features of extinct organisms, paleohistology is used (e.g. Sander, 2000;Steel, 2008;Andrade & Sayão, 2014).…”

“…The study of bone microstructure preserved in fossil organisms reveals substantial information about the physiology, gradients and growth strategies, indicating its ontogenetic stage and allowing some ecological considerations to be made (Bennett, 1993a;Chinsamy & Dodson, 1995;Horner et al, 2000;Kellner et al, 2013;Andrade & Sayão, 2014). The number of vascular canals, LAGs and tissue patterns are some of the features analyzed by paleohistology to reconstruct the past life story of extinct animals (Chinsamy et al, 2009).…”

A paleontologia no século XXI: novas técnicas e interpretações

“…Um dos destaques atuais foi a observação da microestrutura dos ossos do crocodilo marinho Guarinisuchusmunizi, encontrado nas rochas localizadas no litoral do estado de Pernambuco. Nessa pesquisa verificou-se, a partir da análise da tíbia e do fêmur, que essa espécie de crocodilo possuía ossos bastante leves e vascularizados, o que poderia conferir a esse animal a capacidade de ser um exímio nadador (8). A partir dessa e de outras características observadas na composição do osso, os autores propuseram que o dos os equipamentos necessários para estudos de cunho paleobiológico em nosso país.…”