129-73 Digital Segmentation and Skeletal Reconstruction of the Basal Aetosaur Stenomyti Using synchrotron computed tomography data

Abstract:

Aetosaurs are a clade of heavily armored, medium- to large-sized omnivorous or herbivorous pseudosuchian archosaurs that occupied terrestrial ecosystems during the Late Triassic (~231– 201 Ma). Several aetosaur taxa have been described in rigorous detail, while the species Stenomyti huangae remains comparatively understudied. Stenomyti huangae is known from three partial skeletons, the holotype (DMNH 60708) and referred specimens (DMNH 61392 and DMNH 34565), containing cranial and postcranial elements from the ‘red siltstone member’ of the uppermost Late Triassic Chugwater Group in the Eagle Basin of Colorado, United States. Many aspects of its osteology are difficult to examine using traditional preparation techniques due to overlapping elements of the carapace and a dense rock matrix. This study utilizes high-resolution synchrotron computed tomography (CT) data of the holotype specimen DMNH 60708 to digitally segment and reconstruct the skeleton of Stenomyti. The CT datasets were imported into the software Dragonfly, where individual skeletal elements were segmented and isolated from both the rock matrix and adjacent bones. These segmented elements were then used to generate 3D models that allow detailed examination of anatomical features previously inaccessible on the exterior of DMNH 60708. The resulting reconstructions allow visualization and description of previously unknown elements (e.g., cervical vertebrae) along with additional anatomical details of previously described elements that were otherwise obscured by the matrix. The use of CT-based segmentation offers significant advantages over traditional preparation by preserving specimen integrity while allowing repeated, non-destructive examination of internal and external structures. These observations can provide valuable comparisons with aetosaurs and other pseudosuchians that may further clarify the relationships of the clade and their role in Late Triassic ecosystems.

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