Paläontologisches Institut und Museum der Universität Zürich, Karl Schmid-Strasse 4, CH-8006 Zürich, Switzerland.
Anat Rec (Hoboken). 2014 Feb;297(2):240-60. doi: 10.1002/ar.22849. Epub 2013 Dec 24.
As in other archosauriforms, phytosaurs and aetosaurs are characterized by the presence of well-developed osteoderms. Here we provide a comparative study on the microstructure of phytosaur (five taxa) and aetosaur (thirteen taxa) osteoderms. For outgroup comparison, we sampled osteoderms of the sister taxon to Aetosauria, Revueltosaurus callenderi, and the doswelliid Jaxtasuchus salomoni. Phytosaur, aetosaur, and Jaxtasuchus osteoderms are composed of a diploe structure, whereas the Revueltosaurus osteoderm microanatomy is more compact. The external cortex of phytosaurs, Revueltosaurus and Jaxtasuchus osteoderms is mainly composed of parallel-fibered bone. In aetosaurs, the external cortex mainly consists of lamellar bone, with lines of resorption within the primary bone indicating successive cycles of bone erosion and deposition. The basal cortex in all the specimens is composed of parallel-fibered bone, with the cancellous internal core being more strongly developed in aetosaurs than in phytosaurs. Woven or fibro-lamellar bone was recorded in both phytosaurian and aetosaurian taxa, as well as in Jaxtasuchus. Structural fibers, which at least partly suggest metaplastic origin, were only recorded in the internal core of two phytosaurs and in the basal cortex of one aetosaur. Osteoderm thickness and cancellous to compact bone ratios appear to be subject to ontogenetic change. Minimum growth mark counts in osteoderms sampled indicate that some aetosaurs and phytosaurs lived for at least two decades. Bone microstructures are more uniform in phytosaur osteoderms and show a higher level of disparity among aetosaur osteoderms, and at least in the latter, histological features are potentially apomorphic for species/genus level.
与其他槽齿龙类一样，植龙类和鳄龙类的特征是具有发育良好的骨板。在这里，我们对植龙类（五个分类单元）和鳄龙类（十三个分类单元）的骨板微观结构进行了比较研究。为了进行外群比较，我们采样了鳄龙类的姐妹分类单元雷夫洛龙和多齿龙的骨板，以及 Doswellia 的 Jaxtasuchus。植龙类、鳄龙类和 Jaxtasuchus 的骨板由板层结构组成，而雷夫洛龙的骨板微观解剖结构更为紧凑。植龙类、雷夫洛龙和 Jaxtasuchus 骨板的外部皮质主要由平行纤维骨组成。在鳄龙类中，外部皮质主要由板层骨组成，初级骨内的吸收线表明骨侵蚀和沉积的连续循环。所有标本的基底层皮质均由平行纤维骨组成，其中松质内部核心在鳄龙类中比在植龙类中更为发达。编织骨或纤维-板层骨在植龙类和鳄龙类以及 Jaxtasuchus 中均有记录。结构纤维，至少部分表明其具有转化起源，仅在两个植龙类的内部核心和一个鳄龙类的基底层皮质中被记录。骨板厚度和松质骨与致密骨的比例似乎受到个体发育变化的影响。在采样的骨板中，最少的生长标记计数表明，一些鳄龙类和植龙类至少活了二十年。植龙类骨板的微观结构更为均匀，而鳄龙类骨板的差异程度更高，至少在后者中，组织学特征可能是物种/属水平的特化特征。
