Filling a key gap in growth patterns of Pseudosuchia through the osteohistology of <em>Dynamosuchus collisensis</em> (Ornithosuchidae: Archosauria)

Ornithosuchidae are among the least studied pseudosuchians from a histological perspective, and their life history remains poorly constrained. Here we present the first long-bone osteohistological data for the Brazilian ornithosuchid Dynamosuchus collisensis, based on mid-diaphyseal thin sections of the humerus and femur, supplemented by a rib. The long bones show cortices dominated by highly vascularised woven-parallel complex and parallel-fibred bone, with three well-defined annuli and a fourth incipient one near the periosteal margin. Medullary expansion occurs through endosteal resorption, and secondary osteons are absent. The rib displays lower vascularisation, consistent with reduced growth rates in axial elements. Open neurocentral sutures, the absence of an EFS, and the lack of peripheral slowdown in cortical deposition indicate that the holotype was skeletally and likely sexually immature. These features support sustained rapid growth, contrasting with the predominantly slow gr..., Histological samples were prepared following standard paleohistological protocols for fossil bone. Elements were embedded in resin, sectioned using a precision diamond saw, and mounted on glass slides before being ground to optical translucency. Imaging was performed on polished thin sections under polarizing light microscopy, using high-resolution tiled captures subsequently stitched into panoramas for microstructure interpretation. Data include high-resolution thin-section raw panorama images necessary to reproduce the qualitative interpretations presented in the accompanying manuscript. For the femur, the raw images are provided under normal transmitted light; polarised images shown in the manuscript were produced from the same thin-section locally and do not constitute additional raw data. , # Data from: Filling a key gap in growth patterns of Pseudosuchia through the osteohistology of *Dynamosuchus collisensis* (Ornithosuchidae: Archosauria) Dataset DOI: [10.5061/dryad.h70rxwdz1](https://doi.org/10.5061/dryad.h70rxwdz1) ## Description of the data and file structure This dataset contains raw panoramic osteohistological images of a humerus, a femur, an indeterminate long bone and a rib belonging to CAPPA/UFSM 0248 (*Dynamosuchus collisensis*). The panoramas were automatically generated by *Affinity Photo 2* (macOS) ### Files and variables #### File: RSOS-252042_humerus_polarised.jpg **Description:** high-resolution polarised panoramic thin-section of the humerus. #### File: RSOS-252042_femur.jpg **Description:** high-resolution panoramic thin-section of the femur. #### File: RSOS-252042_femur_polarized.jpg **Description:** high-resolution polarised magnified view of thin-section of the femur. #### File: RSOS-252042_indeterminate_long_bone_polarised.jpg **Descript...,