Alcober Oscar A, Martinez Ricardo N
Museo de Ciencias Naturales, San Juan 5400, Argentina.
Zookeys. 2010 Oct 19(63):55-81. doi: 10.3897/zookeys.63.550.
Herrerasauridae comprises a basal clade of dinosaurs best known from the Upper Triassic of Argentina and Brazil, which have yielded remains of Herrerasaurus ischigualastensis and Staurikosaurus pricei, respectively. Systematic opinion regarding the position of Herrerasauridae at the base of Dinosauria has varied. Here we describe a new herrerasaurid, Sanjuansaurus gordilloi gen. n., sp. n., based on a partial skeleton from Carnian-age strata of the the Upper Triassic Ischigualasto Formation of northwestern Argentina. The new taxon is diagnosed by numerous features, including long, band-shaped and posterolaterally oriented transverse process on the posterior cervical vertebrae; neural spines of the sixth to eighth dorsal vertebrae, at least, bearing acute anterior and posterior processes; scapula and coracoid with everted lateral margins of the glenoid; and short pubis (63% of the femoral length). Phylogenetic analysis placed Sanjuansaurus within a monophyletic Herrerasauridae, at the base of Theropoda and including Herrerasaurus and Staurikosaurus. The presence of Sanjuansaurus at the base of the Ischigualasto Formation, along with other dinosaurs such as Herrerasaurus, Eoraptor, Panphagia, and Chromogisaurus suggests that saurischian dinosaurs in southwestern Pangea were already widely diversified by the late Carnian rather than increasing in diversity across the Carnian-Norian boundary.
黑瑞龙科是恐龙的一个基干类群，以阿根廷和巴西上三叠统最为著名，分别发现了伊斯基瓜拉斯托黑瑞龙（Herrerasaurus ischigualastensis）和普氏始盗龙（Staurikosaurus pricei）的化石。关于黑瑞龙科在恐龙总目基部的系统发育位置，学界观点不一。在此，我们基于阿根廷西北部上三叠统伊斯基瓜拉斯托组卡尼阶地层的一具部分骨骼化石，描述了一种新的黑瑞龙科恐龙——戈尔迪约桑胡安龙（Sanjuansaurus gordilloi），属名及种名均为新拟。该新分类单元具有众多鉴别特征，包括颈椎后部有长的、带状且向后外侧延伸的横突；至少第六至八节背椎的神经棘有尖锐的前后突起；肩胛骨和乌喙骨的肩胛骨关节窝外侧边缘外翻；耻骨短（为股骨长度的63%）。系统发育分析将桑胡安龙置于单系的黑瑞龙科内，位于兽脚亚目基部，包括黑瑞龙和始盗龙。桑胡安龙出现在伊斯基瓜拉斯托组基部，与其他恐龙如黑瑞龙、始盗龙、泛食龙和色吉龙一同表明，泛大陆西南部的蜥脚类恐龙在卡尼晚期就已广泛分化，而非在卡尼阶 - 诺利阶边界期间多样性增加。
