A survey of osteoderm histology and ornamentation among Crocodylomorpha: A new proxy to infer lifestyle?

Osteoderms of eight extant and extinct species of crocodylomorphs are studied histologically and morphologically. Most osteoderms display the typical crocodilian structure with a woven-fibered matrix surrounded by an upper and a lower parallel fibered matrix. The dorsal ornamentation of those specimens consists of a pit-and-ridge structure, with corresponding remodeling mechanisms. However, an osteoderm of Iberosuchus, studied here for the first time, differs in being nearly devoid of ornamentation; moreover, it shows strong bundles of straight Sharpey's fibers perpendicular to the surface in its lateral and dorsal walls, along with a rough plywood-like structure in its basal plate. This suggests that this osteoderm was more deeply anchored within the dermis than the other osteoderms studied hitherto. This peculiar structure might have been linked to a terrestrial ecology and a specific thermoregulation strategy. Some other notosuchians in our sample do not exhibit ornamentation on their osteoderms, as opposed to neosuchians. Considering current interpretations of osteoderm function(s) in crocodilians, our observations are discussed in reference to possible ecophysiological peculiarities of Notosuchia in general, and Iberosuchus in particular.

Automated summary

Histological and morphological studies were conducted on osteoderms from eight extant and extinct species of crocodylomorphs. Most osteoderms exhibited a typical crocodilian structure, while an osteoderm of Iberosuchus was found to be nearly devoid of ornamentation and had a unique structure. This suggests a possible link to terrestrial ecology and specific thermoregulation strategies. The findings were discussed in light of current interpretations of osteoderm function(s) in crocodilians and the ecophysiological peculiarities of Notosuchia, particularly Iberosuchus.