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. 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, 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 2-3 small but pointed cusplets, and triangular labial and lingual protuberance, and 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 as these 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 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 has 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）的长鳍鲛科（Lonchidiidae）新属Pristrisodus。通过比较分析，将发现于同一层位的Parvodus tikiensis与Lissodus duffini归为同物异名，并建立新分类单元Pristrisodus tikiensis。该类牙齿呈长条形，近中远中长度不小于唇舌向宽度的两倍，具备高耸的主齿尖与侧齿尖；唇侧冠根交界附近以及舌侧齿冠上部具明显棱脊，纹饰较弱，冠根交界处带有线性凹陷。研究根据整体形态、粗壮程度以及齿冠高度划分出5种形态型。该类牙齿呈现出渐进式的单颌异齿型特征：前侧齿（形态型I~II）的主齿尖高耸呈锥形，带有2~3枚小巧尖锐的侧齿尖，唇侧与舌侧均具三角形突起；而后侧齿（形态型III~IV）则具4枚初生齿尖，主齿尖相对低矮，唇侧突起呈悬垂双叶/圆形，舌侧突起为初生状态。形态型V包含前齿，这类牙齿宽扁呈三角形且粗壮，主齿尖圆钝，仅具1枚侧齿尖，唇侧齿突低矮且呈悬垂状。多变量分析佐证了针对印度弓鲛类（Hybodontiformes）的定性评估结果。Pristrisodus的牙齿组织学特征明显区别于其他长鳍鲛科属类。提基组中淡水鲨类与其他脊椎动物微化石组合，与美国钦勒群（Chinle Group）下特科瓦斯组（Lower Tecovas Formation）的对应组合具有相似性。在三叠纪卡尼期（Carnian），广盐性特征使得弓鲛类得以适应印度的淡水生境。