Ontogeny of the middle-ear air-sinus system in Alligator mississippiensis (Archosauria: Crocodylia)

Modern crocodylians, including Alligator mississippiensis, have a greatly elaborated system of pneumatic sinuses invading the cranium. These sinuses invade nearly all the bones of the chondrocranium and several bony elements of the splanchnocranium, but patterns of postnatal paratympanic sinus development are poorly understood and documented. Much of crocodylomorph—indeed archosaurian—evolution is characterized by the evolution of various paratympanic air sinuses, the homologies of which are poorly understood due in large part to the fact that individual sinuses tend to become confluent in adults, obscuring underlying patterns. This study seeks to explore the ontogeny of these sinuses primarily to clarify the anatomical relations of the individual sinuses before they become confluent and thus to provide the foundation for later studies testing hypotheses of homology across extant and extinct Archosauria. Ontogeny was assessed using computed tomography in a sample of 13 specimens coverin...

现代鳄目动物，包括密西西比短吻鳄（Alligator mississippiensis），拥有一套高度发达的侵入颅骨的气囊窦（pneumatic sinuses）系统。该类窦腔几乎遍及软骨颅（chondrocranium）的全部骨骼以及脏颅（splanchnocranium）的多个骨组分，但学界对产后鼓室旁窦（paratympanic sinus）的发育模式仍缺乏充分了解与相关记载。鳄形类（crocodylomorph）——乃至主龙类（Archosauria）——的演化历程，在很大程度上以各类鼓室旁气窦的演化为标志性特征；由于成体个体内的单个气窦常会相互融合，掩盖了其原始发育模式，这类气窦的同源性问题长期以来难以得到清晰阐释。本研究旨在探究这些气窦的个体发育（ontogeny）过程，核心目标是厘清气窦相互融合前各单个气窦的解剖学关联，进而为后续开展现存与灭绝主龙类的同源性假说验证研究奠定理论基础。本研究采用计算机断层扫描（computed tomography）技术，对涵盖……的13份标本样本开展个体发育评估。