巴西研究人员发现了一具距今约2.4亿年前的爬行动物化石，属于恐龙和鳄鱼的远古祖先群体[1]。这一新物种被命名为Silescelida acristata，化石出土于巴西Rio Grande do Sul州内陆的Dona Francisca地区，该地隶属联合国教科文组织Quarta Colônia地质公园[1]。
该化石的关键特征在于其独特的腿部结构——股骨位置呈半直立状态，不具有粗隆（trochanter），表明这类爬行动物拥有比早期物种更高效的运动方式[1]。物种名称反映了发现过程的曲折：Silescelida取自"沉寂"一词，因为化石在遗失20多年后才于2022年被重新发现；acristata则指其主要保存的肢骨特征[1]。这项研究由圣玛丽亚联邦大学古生物研究中心、南里奥格兰德联邦大学及南里奥格兰德教宗天主教大学合作完成，成果发表在《Scientific Reports》期刊上[1]。
根据系统分类分析，Silescelida acristata可能与Euparkeriidae族群相关，此前该族群的已知分布仅限于非洲、亚洲和欧洲[1]。这一发现表明，在三叠纪时期，这类爬行动物的地理分布范围比科学家此前认为的更为广泛[1]。
Paleontologists in Brazil have identified a new reptile species from approximately 240 million years ago that sheds light on the evolutionary history preceding both dinosaurs and crocodiles.[1] The fossilized remains, designated Silescelida acristata, belong to an ancient lineage that served as a distant ancestor to these major reptilian groups.[1]
The specimen was discovered in Dona Francisca, located in Rio Grande do Sul state within Brazil's UNESCO Quarta Colônia geological park.[1] The fossil, which had been lost for over two decades, was partially rediscovered in 2022.[1] The species name reflects this unusual history—"Silescelida" derives from the Latin word for silence, referencing the fossil's long absence from scientific study, while "acristata" refers to the legs, the specimen's most well-preserved anatomical feature.[1]
A defining characteristic of Silescelida acristata is the semi-erect positioning of its femur, which lacks a trochanter structure.[1] This anatomical configuration suggests the creature possessed a more efficient locomotion method compared to earlier reptiles of its time.[1] The discovery indicates that the broader reptilian group possibly related to the Euparkeriidae family, previously known only from Africa, Asia, and Europe, had a wider geographic distribution during the Middle Triassic period than scientists had previously recognized.[1] The research, conducted collaboratively by paleontologists at the Federal University of Santa Maria, Federal University of Rio Grande do Sul, and the Pontifical Catholic University of Rio Grande do Sul, was published in Scientific Reports.[1]