Battista Francesco, Martinelli Agustín G, Ribeiro Ana Maria, de Andrade Marco Brandalise, Schultz Cesar L
Laboratório de Paleontologia de Vertebrados, Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", CONICET, Buenos Aires, Argentina.
Anat Rec (Hoboken). 2024 Oct 11. doi: 10.1002/ar.25589.
Rhynchosauria is a group of extinct, exclusively Triassic, terrestrial, and herbivorous archosauromorphs, characterized by a peculiar maxillary-mandibular apparatus. They reached global distribution during the Carnian, with the Hyperodapedontinae clade. The rhynchosaurian record from South America is included in the Ladinian-?earliest Carnian Dinodontosaurus Assemblage Zone (Pinheiros-Chiniquá Sequence, Brazil) and Tarjadia Assemblage Zone (Chañares Formation, Argentina), and for strictly Carnian Hyperodapedon Assemblage Zone (Lower Candelária Sequence, Brazil) and Ischigualasto Formation (Argentina). Here, we present the first record of Hyperodapedontinae from the Brazilian Early Carnian Santacruzodon Assemblage Zone (Santa Cruz Sequence). The most diagnostic elements belong to a nearly complete left pes, which presents a combination of hyperodapedontine traits. The presence of a second individual of cf. Hyperodapedontinae is based on a fragmentary, isolated left metatarsal IV. An isolated fragment of premaxilla could belong to the second specimen (based on preservation mode) or to a third individual. This new report fills a gap within the South American rhynchosaurian distribution, strengthening biostratigraphic correlation with other regions from Gondwana (i.e., Madagascar), where similar and coeval faunas are known. The inclusion of these specimens in a phylogenetic dataset resulted in low resolution results, due to missing data because postcranial characters for rhynchosaurs are still poorly explored.
喙头龙类是一类已灭绝的、仅生存于三叠纪的、陆生的草食性主龙形类，其特征是具有独特的上颌-下颌结构。在卡尼期，它们与高齿龙亚科一起分布于全球。南美洲的喙头龙类化石记录包括拉丁期-？最早卡尼期的迪诺齿龙组合带（巴西的皮涅罗斯-奇尼基瓦层序）和塔尔贾迪亚组合带（阿根廷的查纳雷斯组），以及严格意义上的卡尼期高齿龙组合带（巴西的下坎德拉里亚层序）和伊斯基瓜拉斯托组（阿根廷）。在此，我们展示了来自巴西早卡尼期圣克鲁佐顿组合带（圣克鲁斯层序）的高齿龙亚科的首个记录。最具诊断性的化石属于一个近乎完整的左足，它呈现出高齿龙亚科的特征组合。另一个疑似高齿龙亚科个体的存在基于一块破碎、孤立的左第四跖骨。一块孤立的前上颌骨碎片可能属于第二个标本（基于保存方式）或第三个个体。这一新报告填补了南美洲喙头龙类分布的空白，加强了与冈瓦纳其他地区（如马达加斯加）的生物地层对比，在这些地区已知有相似且同期的动物群。由于喙头龙类的颅后特征仍未得到充分研究，数据缺失，将这些标本纳入系统发育数据集得到的结果分辨率较低。
