Affiliation:
1. Programa de Pós‐Graduação em Geociências Instituto de Geociências, Universidade Federal do Rio Grande do Sul Porto Alegre Rio Grande do Sul Brazil
2. CONICET—División Paleontologia Vertebrados, Facultad de Ciencias Naturales y Museo Universidad Nacional de La Plata La Plata Buenos Aires Argentina
3. Instituto de Investigación en Paleobiologia y Geología (CONICET—Universidad Nacional de Río Negro) Cipolletti Río Negro Argentina
4. Museu de Ciências Naturais—Jardim Botânico, Secretaria do Meio Ambiente e Infraestrutura Porto Alegre Rio Grande do Sul Brazil
5. Departamento de Geologia e Paleontologia, Museu Nacional Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil
Abstract
AbstractDecuriasuchus quartacolonia is a middle‐sized basal “rauisuchian” (Pseudosuchia, Loricata) from the Triassic beds of Brazil, whose original description was based on 10 specimens of equivalent size found in aggregation. In this contribution, we explore the osteohistology of its appendicular bones and a rib, aiming to infer growth patterns and ontogeny. In all analyzed bones (except in the rib) from three individuals, we found fibrolamellar bone (FLB) throughout the cortices, a pattern shared with other histologically sampled basal loricatans. We found evidence that suggests an early ontogenetic stage for all studied specimens: absence of secondary osteons, lack of transition from an inner highly vascularized FLB matrix to a poor vascularized parallel‐fibred bone, one line of arrested growth, open vascular canals in the external surface of the cortex and absence of an external fundamental system. In addition, we observed that the neurocentral sutures in the caudal to cervical vertebrae of the holotype are unfused, strongly suggesting that these individuals were not skeletally mature, as had been previously assumed. In addition, our data support the prior hypothesis that Decuriasuchus is the oldest‐known archosaur to show evidence of gregarious behavior and adds a probable cause of this as a strategy to obtain food and avoid predation until becoming independent as adults. Furthermore, our results open the possibility that Decuriasuchus may represent an earlier growth stage of the larger Prestosuchus chiniquensis, with two specimens recovered from the same stratigraphic level and paleontological site. Since the adult form of Decuriasuchus remains unknown, a deeper anatomical study is needed to discuss the validity of the species. This study case exemplifies the importance of paleohistology as an essential complementary tool to describe a new morphospecies in vertebrate paleontology.
Funder
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
Agencia Nacional de Promoción Científica y Tecnológica
Subject
Ecology, Evolution, Behavior and Systematics,Histology,Biotechnology,Anatomy
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