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Osteohistology and paleobiological inferences of proterochampsids (Eucrocopoda: Proterochampsia) from the Chañares Formation (late Ladinian–early Carnian), La Rioja, Argentina
Journal of Vertebrate Paleontology ( IF 1.4 ) Pub Date : 2021-07-09 , DOI: 10.1080/02724634.2021.1926273
Denis A. Ponce 1 , M. Jimena Trotteyn 2 , Ignacio A. Cerda 1 , Lucas E. Fiorelli 3 , Julia B. Desojo 4
Affiliation  

ABSTRACT

Proterochampsids were a group of stem archosaurs from the Middle–Late Triassic of South America. Using for the first time in proterochampsids quantitative microanatomical and morphological data and an inference model, we analyze the microstructure of postcranial bones of proterochampsids to infer life-history traits dealing with growth dynamics, ontogenetic changes, dermal armor histogenesis and lifestyle. We studied proterochampsid individuals from the Middle–Late Triassic Chañares Formation: three specimens of Chanaresuchus bonapartei: PVL 4575 (osteoderms and femur), CRILAR-Pv 80 (osteoderm) and CRILAR-Pv 81 (humerus), and a femur of a non-identified Rhadinosuchinae specimen (CRILAR-Pv 488). The osteoderms show a compact-uniform composition of parallel-fibered bone and lines of arrested growth (LAGs). The long bones are composed mainly of highly vascularized, parallel-fibered bone and isolated areas of woven-fibered bone in the innermost portion of cortex (only in C. bonapartei PVL 4575). The absence of an external fundamental system (EFS) indicates that all of the sampled individuals were somatically immature at time of death. The absence of mineralized bundles of collagenous fibers supports intramembranous ossification as the developmental origin for the osteoderms. With an inference model used for the first time in proterochampsids, the lifestyle inferred for C. bonapartei is terrestrial. Histological evidence indicates that sexual maturity is reached before both somatic and skeletal maturity. The growth patterns among proterochampsids exhibit some degree of variation even within a single species. Such variation can be due to different causes, including possibly phenotypic plasticity.



中文翻译:

来自阿根廷拉里奥哈的 Chañares 组(拉丁期晚期 - 卡尼阶早期)的原龙目(真足纲:Proterochampsia)的骨组织学和古生物学推断

摘要

Proterochampsids 是一组来自南美洲中-晚三叠世的干祖龙。我们第一次使用 proterochampsids 的定量显微解剖学和形态学数据以及推理模型,分析了 proterochampsids 颅后骨骼的微观结构,以推断处理生长动态、个体发育变化、真皮盔甲组织发生和生活方式的生活史特征。我们研究了来自中-晚三叠世 Chañares 组的 proterochampsid 个体:Chanaresuchus Bonapartei 的三个标本:PVL 4575(骨皮和股骨)、CRILAR-Pv 80(骨皮)和 CRILAR-Pv 81(肱骨),以及未鉴定的棘头鳄亚科标本(CRILAR-Pv 488)的股骨。骨皮层显示出由平行纤维骨和生长停滞线 (LAG) 组成的紧凑均匀的组成。长骨主要由高度血管化的平行纤维骨和皮质最内侧的编织纤维骨的孤立区域组成(仅在C. bonaparteiPVL 4575)。外部基本系统 (EFS) 的缺失表明所有采样的个体在死亡时都未成熟。胶原纤维矿化束的缺乏支持膜内骨化作为骨皮层的发育起源。通过首次在 proterochampsids 中使用的推理模型,为C. Bonapartei 推断的生活方式是陆生的。组织学证据表明,性成熟是在躯体和骨骼成熟之前达到的。proterochampsids 之间的生长模式即使在单个物种内也表现出一定程度的变化。这种变化可能是由于不同的原因造成的,包括可能的表型可塑性。

更新日期:2021-09-15
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