Data from: A new hybodont shark (Chondrichthyes, Elasmobranchii) from the Upper Triassic Tiki Formation of India with remarks on its dental histology and biostratigraphy

A new lonchidiid genus, Pristrisodus, from the Upper Triassic Tiki Formation of India is described based on multiple, well-preserved, isolated teeth. Comparative analysis resulted in synonymizing Parvodus tikiensis and Lissodus duffini, which are known from the same horizon and resulted in a new taxon, Pristrisodus tikiensis n. comb. These teeth are elongated with mesiodistal length greater than or equal to twice the labiolingual width and have a high principal cusp, lateral cusplets, a distinct ridge near the crown-root junction labially and higher up on the crown lingually, weak ornamentation, and linear depression along the crown-root junction. Five morphotypes based on overall shape, robustness and crown height are determined. The teeth show a gradual monognathic heterodonty. The anterolateral teeth (morphotypes I−II) have high, pyramidal principal cusp with two or three small but pointed cusplets, and triangular labial and lingual protuberance. The posterolateral teeth (morphotypes III−IV) have four incipient cusplets, relatively low principal cusp, bilobed/rounded, hanging labial and incipient lingual protuberances. Morphotype V comprises anterior teeth that are broad, triangular and robust, and have rounded/blunt principal cusp, one cusplet, and low, hanging labial peg. Multivariate analyses corroborate the qualitative assessment of the Indian hybodonts. Dental histology of Pristrisodus n. gen., shows that it is distinctly different from other lonchidiid genera. The assemblage of freshwater sharks, along with other vertebrate microfossils of the Tiki Formation, shows similarity with that of the lower Tecovas Formation of the Chinle Group, USA. The euryhaline nature resulted in the adaptation of the hybodonts to freshwater systems in India during the Carnian.

基于多枚保存完好的孤立牙齿，本文记述了产自印度上三叠统提基组（Tiki Formation）的一新钝齿鲨科（Lonchidiidae）属：Pristrisodus。通过比较分析，我们将同层位发现的Parvodus tikiensis与Lissodus duffini归为同物异名，并建立新组合Pristrisodus tikiensis n. comb.。该类群牙齿呈延长形，近中远中轴长度（mesiodistal length）不小于唇舌宽度（labiolingual width）的两倍，主齿尖高耸，具侧生小齿尖；唇面冠根交界处及舌面牙冠中上部具明显脊状结构，纹饰较弱，冠根交界处带有线状凹陷。根据整体形态、粗壮度及牙冠高度，可将其牙齿划分为5种形态型（morphotypes）。该类群牙齿呈现渐进的单颌齿型异齿现象：前侧位牙齿（形态型I−II）主齿尖高耸呈锥形，具2至3枚细小尖锐的小齿尖，唇面与舌面均具三角形突起；后外侧位牙齿（形态型III−IV）具4枚初现的小齿尖，主齿尖相对低矮，唇面突起呈双叶/圆形下垂状，舌面突起初现。形态型V为前部牙齿，整体宽扁呈三角形且较为粗壮，主齿尖圆润/钝圆，具1枚小齿尖，唇面带有低矮下垂的柱状突起。多元统计分析证实了针对印度弓鲛类（hybodonts）的定性评估结果。Pristrisodus新属的牙齿组织学特征明显区别于其他钝齿鲨科属类。该淡水鲨类组合与提基组的其他脊椎动物微化石一道，与美国钦尔群（Chinle Group）下特科瓦组（lower Tecovas Formation）的化石组合具有相似性。在卡尼期（Carnian），这类广盐性（euryhaline）生物使得弓鲛类得以适应印度的淡水生态系统。