Redescription of the cranial morphology of Amphisbaena braestrupi and Amphisbaena laurenti (Squamata: Amphisbaenidae) from the Pleistocene of Brazil using x-ray computed tomography.

Amphisbaenians (Squamata: Amphisbaenidae) are fossorial reptiles with highly specialized cranial morphology, yet their fossil record is frequently limited by fragmentary preservation. This study provides a detailed osteological redescription of the skulls of Amphisbaena braestrupi and Amphisbaena laurenti from the Pleistocene of Lagoa Santa (Brazil) using high-resolution x-ray computed tomography. Beyond surface morphology, 3D reconstructions allowed the first detailed visualization of previously inaccessible internal anatomical features, such as the complex architecture of the braincase and the parabasal and optic canals. The analysis revealed hourglass-shaped skulls with pronounced sagittal crests and an advanced degree of coossification in the occipital complex. Digital dissection enabled the description of the pyramidal morphology of the otic capsules and the arrangement of the semicircular canals, alongside a more comprehensive redescription of the fossil material. Comparisons with the extant species Amphisbaena alba show that the fossils reach the upper limit of cranial size variation and exhibit greater occipital robustness. These findings fill critical anatomical gaps, providing new internal characters for taxonomic, phylogenetic, and evolutionary studies of South American amphisbaenians.