Schachner Emma R, Diaz Raul E, Coke Rob, Echols Scott, Osborn Michelle L, Hedrick Brandon P
Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA.
Department of Biological Sciences, California State University Los Angeles, Los Angeles, California, USA.
Anat Rec (Hoboken). 2022 Oct;305(10):3037-3054. doi: 10.1002/ar.24919. Epub 2022 Apr 4.
We imaged the lungs of five Cuvier's dwarf caiman (Paleosuchus palpebrosus) via computed tomography (CT) and micro-computed tomography (μCT) and compared these data to the lungs of the American alligator (Alligator mississippiensis). These data demonstrate anatomical commonalities between the lungs of P. palpebrosus and A. mississippiensis, and a few notable differences. The structural similarities are (a) a proximally narrow, distally widened, hook-shaped primary bronchus; (b) a cervical ventral bronchus that branches of the primary bronchus and immediately makes a hairpin turn toward the apex of the lung; (c) a sequential series of dorsobronchi arising from the primary bronchus caudal to the cervical ventral bronchus; (d) intraspecifically highly variable medial sequence of secondary airways; (e) sac-like laterobronchi; and (f) grossly dead-ended caudal group bronchi in the caudal and ventral aspects of the lung. The primary differences between the two taxa are in the overall number of large bronchi (fewer in P. palpebrosus), and the number of branches that contribute to the cardiac regions. Imaging data of both a live and deceased specimen under varying states (postprandial, fasting, total lung capacity, open to atmosphere) indicate that the caudal margin and position of the lungs shift craniocaudally relative to the vertebral column. These imaging data suggest that the smooth thoracic ceiling may be correlated to visceral movement during ventilation, but this hypothesis warrants validation. These results provide the scaffolding for future comparisons between crocodilians, for generating preliminary reconstructions of the ancestral crocodilian bronchial tree, and establishing new hypotheses of bronchial homology across Archosauria.
我们通过计算机断层扫描（CT）和显微计算机断层扫描（μCT）对五只居维叶侏儒凯门鳄（Paleosuchus palpebrosus）的肺部进行了成像，并将这些数据与美国短吻鳄（Alligator mississippiensis）的肺部数据进行了比较。这些数据显示了居维叶侏儒凯门鳄和美国短吻鳄肺部在解剖结构上的共性以及一些显著差异。结构上的相似之处包括：（a）近端狭窄、远端变宽的钩状主支气管；（b）从主支气管分出并立即向肺尖呈发夹状转弯的颈腹支气管；（c）从颈腹支气管后方的主支气管发出一系列连续的背支气管；（d）种内二级气道的内侧序列高度可变；（e）囊状侧支气管；（f）肺尾侧和腹侧的粗大盲端尾组支气管。这两个分类群之间的主要差异在于大支气管的总数（居维叶侏儒凯门鳄较少）以及对心脏区域有贡献的分支数量。对一只活体和一只死亡标本在不同状态（餐后、禁食、肺总量、向大气开放）下的成像数据表明，肺的尾缘和位置相对于脊柱发生头尾方向的移动。这些成像数据表明，光滑的胸廓顶部可能与通气过程中的内脏运动相关，但这一假设有待验证。这些结果为未来鳄类之间的比较、构建原始鳄类支气管树的初步重建以及建立整个主龙类支气管同源性的新假设提供了框架。
