The first braincase of the basal aetosaur <i>Aetosauroides scagliai</i> (Archosauria: Pseudosuchia) from the Upper Triassic of Brazil

The phylogenetic relationships of Pseudosuchia, the crocodile-line of Archosauria, are still poorly resolved, in part, due to the lack of crucial braincase information for several key taxa. Recently, erpetosuchids and ornithosuchids have been recovered as close relatives to Aetosauria, sharing several braincase features. Here we provide the description of the first braincase of the basal aetosaur <i>Aetosauroides</i> based on specimens from the Upper Triassic Candelária Sequence of Brazil. Our study revealed the presence of an exoccipital lateral ridge and a medial ridge on the supraoccipital (both shared with all aetosaurs and erpetosuchids, but absent in ornithosuchids) and an anterolateral exit for the internal carotids (shared with all aetosaurs and ornithosuchids, but not with erpetosuchids). <i>Aetosauroides</i> lacks a medial contact between the exoccipitals (shared with the aetosaurs <i>Desmatosuchus smalli</i> and <i>Tecovasuchus</i>) and possesses a single hypoglossal foramen (contrasting with <i>Stagonolepis robertsoni</i> and <i>Desmatosuchus spurensis</i>). It also differs from the putative Argentinian <i>Aetosauroides</i> (PVSJ 326) by the presence of a ridge connecting the basal tubera medially (contrasting also with all stagonolepidoideans) and by a bulbous and ventrolaterally recurved basipterygoid process (contrasting with <i>Paratypothorax</i>). These features show that the braincase of aetosaurs is suitable for providing further phylogenetic information and may contribute to resolving controversies within Pseudosuchia relationships.主龙类（Archosauria）的鳄形支系——伪鳄类（Pseudosuchia）的系统发育关系至今仍未得到清晰解析，部分原因在于多个关键分类单元的脑颅（braincase）信息缺失。近年来，蛇鳄科（Erpetosuchidae）类群与鸟鳄科（Ornithosuchidae）类群被复原为坚蜥目（Aetosauria）的近缘类群，二者与坚蜥目共享多项脑颅特征。本文基于产自巴西上三叠统坎德拉里亚序列（Candelária Sequence）的标本，对基干坚蜥目类群<em>Aetosauroides</em>的首例脑颅进行描述。本研究揭示，该脑颅具有枕外骨（exoccipital）侧脊以及上枕骨（supraoccipital）内侧脊（该特征为所有坚蜥目类群与蛇鳄科所共有，但鸟鳄科不具备），以及颈内动脉（internal carotids）的前外侧出口（该特征为所有坚蜥目类群与鸟鳄科所共有，而蛇鳄科不具备）。<em>Aetosauroides</em>的枕外骨之间不存在内侧接触（该特征与坚蜥类的<em>Desmatosuchus smalli</em>和<em>Tecovasuchus</em>一致），且仅具单个舌下神经管（hypoglossal foramen）（这一点与<em>Stagonolepis robertsoni</em>和<em>Desmatosuchus spurensis</em>形成鲜明对比）。此外，它与被认为属于阿根廷的<em>Aetosauroides</em>标本（PVSJ 326）也存在差异：前者具有连接基底结节（basal tubera）的内侧脊（该特征也与所有斯通诺莱皮德类（Stagonolepidoideans）不同），且具球状且向腹外侧弯曲的基翼突（basipterygoid process）（这一点与<em>Paratypothorax</em>不同）。上述特征表明，坚蜥目的脑颅可提供进一步的系统发育信息，或有助于解决伪鳄类系统发育关系中存在的争议。

搜集汇总

背景与挑战

背景概述

该数据集是关于巴西上三叠统的基底鳄类Aetosauroides scagliai的首个脑颅骨研究，发布于2021年，旨在填补伪鳄类系统发育关系中的关键信息缺口。研究详细描述了脑颅骨特征（如外枕骨侧脊和上枕骨内侧脊），并与其他鳄类进行比较，为古生物学和系统发育学提供新的数据支持。