The oldest turritelline gastropods: from the Oxfordian (Upper Jurassic) of Kutch, India

Turritellid gastropods are important components of many Cretaceous-Recent fossil marine faunas worldwide. Their shell is morphologically simple, making homoplasy widespread and phylogenetic analysis difficult, but fossil and living species can be recognized based on shell characters. For many decades, it has been the consensus that the oldest definite representatives of Turritellidae are from the lower Cretaceous, and that pre-Cretaceous forms are homeomorphs. Some morphological characters of the present turritelline species resemble those of mathildoids, but many diagnostic characters clearly separate these two groups. We here describe and/or redescribe – based on examination of more than 1800 near complete specimens -- four species from the Upper Jurassic Dhosa Oolite Member of the Chari Formation in Kutch, western India, and demonstrate that they are members of Turritellidae, subfamily Turritellinae, on the basis of diagnostic characters including apical sculptural ontogeny (obtained...锥螺科（Turritellidae）腹足类是全球范围内诸多白垩纪至现代海洋化石动物群的重要组成类群。其壳体形态结构简单，导致趋同演化（homoplasy）现象广泛分布，系统发育分析难度较高，但仍可通过壳体特征对化石物种与现生物种进行识别。数十年来，学界普遍认为锥螺科确定的最古老类群成员来自下白垩统，而白垩纪前的类群均为趋同同型类（homeomorphs）。现生锥螺亚科物种的部分形态特征与帽螺超科（Mathiloidea）类群相似，但诸多鉴别特征可清晰区分这两个类群。本文基于对印度西部库奇地区查里组上侏罗统多萨鲕状灰岩段1800余件近完整标本的检视，描述并/或重新记述了4个物种，并通过包括壳顶雕刻个体发育序列（apical sculptural ontogeny (obtained...）在内的鉴别特征，证明它们隶属于锥螺科锥螺亚科（Turritellinae）。