Data from: Early Jurassic Trochotomidae (Vetigastropoda, Pleurotomariodea) from the Neuquén Basin, Argentina

Trochotomidae is a small but distinctive extinct family of pleurotomarioidean gastropods characterized by trochiform shells with an elliptical trema. Two new species of trochotomids are described from Pliensbachian deposits in the Neuquén Basin, Argentina. The new genus-group name Placotoma is proposed to replace the pre-occupied name Discotoma Haber non Mulsant. The record of Trochotoma (Trochotoma) protonotialis new species and Trochotoma (Placotoma) neuquensis new species in the early Jurassic of Argentina extends the paleobiogeographical distribution of the genus (and the family) to the Southern Hemisphere. The new taxa reported here represent a component of the pleurotomarioidean adaptive radiation that took place in the Tethyan region during the earliest Jurassic. They are related to local patch coral reefs of shallow, open-marine paleoenvironments, agreeing with the known habitat of most species of this family. The group was well represented in the Tethyan region during the Mesozoic, especially during the Jurassic, and the new species represent its southernmost occurrence.

旋螺科（Trochotomidae）是一类体型小巧但特征鲜明的已灭绝腹足类类群，隶属于翁戎螺超科（Pleurotomarioidea），以具椭圆形壳孔（trema）的陀螺形壳体为主要鉴别特征。本研究描述了产自阿根廷内乌肯盆地（Neuquén Basin）普林斯巴阶（Pliensbachian）地层的2个旋螺科新物种。为替换被优先占有的学名Discotoma Haber（非Mulsant），本文提出新的属级名称Placotoma。产自阿根廷早侏罗世地层的Trochotoma (Trochotoma) protonotialis新种与Trochotoma (Placotoma) neuquensis新种的化石记录，将旋螺属（Trochotoma）（及旋螺科）的古生物地理分布范围拓展至南半球。本次报道的新分类群，属于早侏罗世特提斯（Tethyan）区域内翁戎螺超科适应性辐射演化的组成部分。其栖息环境为浅海开阔海域的局部斑礁古环境，与该科多数物种的已知栖息环境相符。该类群在中生代（Mesozoic），尤其是侏罗纪（Jurassic）时期的特提斯区域曾有大量化石记录，本次发现的新物种是该类群已知分布最南端的记录。