Romo de Vivar Martínez Paula Rosario, Soares Marina Bento
Laboratório de Paleontologia de Vertebrados, Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
PLoS One. 2015 Mar 20;10(3):e0119307. doi: 10.1371/journal.pone.0119307. eCollection 2015.
Clevosaurus was a cosmopolitan rhynchocephalian genus, known from the Late Triassic to the Early Jurassic. In South America this genus is represented by C. brasiliensis, an important component of the Linha São Luiz taphocoenosis, on the top of the Norian Santa Maria 2 Sequence of Southern Brazil. The best preserved and most abundant bone elements of C. brasiliensis are dentaries, in which variations of shape and size are observed. The aim of this study is to describe and evaluate the variation, using geometric morphometrics methods. Geometric morphometric analysis of 10 specimens highlights variations in relative size of the dentary. Most of the variation observed for PC1 (83.3%) is likely related to ontogeny, and PC2 (10.0%) is likely related to taphonomic signatures. The development patterns observed, such as the growth of the dentary, consists of differential growth in length between the posterior portion of the dentary, that grows at a higher rate, regarding the anterior portion of the element. This allometric growth is similar to what is observed in other rhynchocephalians and is accompanied by the allometric skull growth, similar to the trend exhibited by clevosaurs. The taphocoenosis is bimodal (juveniles and adults) with a bias towards adult preservation. Some diagenetic influence is reflected in deformed skulls and this is observed in the tangent-plot. Finally, a strong correlation was detected between the taphonomic signatures and the PC2, regarding specially disarticulation and degree of fragmentation.
鳄龙是一种分布广泛的喙头目属，生存于晚三叠世至早侏罗世。在南美洲，该属以巴西鳄龙为代表，它是巴西南部诺利阶圣玛丽亚2层序顶部的圣路易斯组埋藏群落的重要组成部分。巴西鳄龙保存最完好、数量最多的骨骼元素是齿骨，在齿骨中观察到了形状和大小的变化。本研究的目的是使用几何形态计量学方法描述和评估这些变化。对10个标本的几何形态计量分析突出了齿骨相对大小的变化。观察到的主成分1（PC1）的大部分变化（83.3%）可能与个体发育有关，主成分2（PC2）的变化（10.0%）可能与埋藏特征有关。观察到的发育模式，如齿骨的生长，包括齿骨后部的长度增长差异，后部的生长速度高于齿骨前部。这种异速生长与在其他喙头目动物中观察到的情况相似，并且伴随着头骨的异速生长，类似于鳄龙类所表现出的趋势。埋藏群落是双峰的（幼年和成年个体），且偏向于成年个体的保存。一些成岩作用的影响反映在变形的头骨上，这在切线图中可以观察到。最后，在埋藏特征与PC2之间检测到了很强的相关性，特别是在关节分离和破碎程度方面。
