Craniomandibular osteology of <i>Macrocollum itaquii</i> (Dinosauria: Sauropodomorpha) from the Late Triassic of southern Brazil

Several new sauropodomorphs have been described in recent years, including the unaysaurid sauropodomorph <i>Macrocollum itaquii</i> (Late Triassic, Brazil). This study presents a detailed description of the craniomandibular anatomy of <i>M. itaquii</i> based on the holotype, a paratype and a newly referred specimen. A phylogenetic analysis using an updated dataset is performed to test a previous hypothesis regarding the affinities of this taxon and its potential influence in the phylogeny of Triassic and Early Jurassic sauropodomorphs. The taxon is supported as a member of Unaysauridae. This clade is recovered as the basal-most group within Massopoda rather than the sister group to Plateosauria. However, the position of <i>M. itaquii</i> (and unaysaurids) is likely to be highly labile due to specific, transitional aspects of its anatomy. The most recently discovered <i>M. itaquii</i> specimen, in conjunction with other newly discovered specimens, serve to elucidate the transition from slender basal sauropodomorphs to more robust derived members within this group.近年来已有多种新的蜥脚形亚目（Sauropodomorpha）恐龙被记述，其中包括乌奈龙科（Unaysauridae）的伊塔基巨颈龙（Macrocollum itaquii，发现于巴西三叠纪晚期地层）。本研究基于正模标本、副模标本以及一件新归入标本，对伊塔基巨颈龙（Macrocollum itaquii）的颅颌解剖结构进行了详细记述。本研究采用更新后的数据集开展系统发育分析（phylogenetic analysis），以验证此前针对该分类单元（taxon）亲缘关系的假说，以及该类群对三叠纪至早侏罗世蜥脚形亚目系统发育演化的潜在影响。该分类单元被支持为乌奈龙科（Unaysauridae）的成员，该演化支被恢复为大脚类（Massopoda）中最基干的类群，而非板龙类（Plateosauria）的姊妹群。然而，由于其解剖结构存在特定的过渡性特征，伊塔基巨颈龙（及乌奈龙科类群）的系统发育位置极有可能存在较高的不稳定性。最新发现的伊塔基巨颈龙标本与其他新发现标本相结合，有助于阐明该类群中从纤细的基干蜥脚形亚目类群到更为粗壮的衍化类群的演化过渡过程。

搜集汇总

背景与挑战

背景概述

该数据集提供了巴西晚三叠世蜥脚类亚目恐龙Macrocollum itaquii的头骨和下颌骨骨学研究的原始数据，包括系统发育分析文件（NEX、TNT格式）和描述文档。数据集支持对该物种解剖学特征的详细分析，并探讨了其在蜥脚类亚目早期演化中的过渡作用，有助于理解从细长基部成员到粗壮衍生成员的形态转变。