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.本研究基于多枚保存完好的孤立牙齿，描述了产自印度上三叠统提基组的隆齿鲛科（Lonchidiidae）新属Pristrisodus。通过比较解剖学分析，我们将产自同一层位的副尖齿鲨属提基种（Parvodus tikiensis）与滑齿鲨属达芬种（Lissodus duffini）归为同物异名，并建立新分类单元Pristrisodus tikiensis新组合（n. comb.）。该属牙齿呈延长状，近中远中长度不小于唇舌径宽度的两倍，具备高耸的主齿尖、侧生小齿尖；唇侧冠根交界处附近以及舌侧牙冠上部可见明显的棱脊，纹饰较弱，且冠根交界处带有线形凹陷。研究人员根据整体形态、粗壮程度以及牙冠高度，将该属牙齿划分为5种形态型。该类牙齿呈现出渐进式单颌异型齿特征：前侧位牙齿（I-II型形态型）具备高耸的锥形主齿尖，带有2~3枚细小而尖锐的侧小齿尖，且唇侧与舌侧均带有三角形突起；后侧位牙齿（III-IV型形态型）带有4枚雏形小齿尖，主齿尖相对低矮，唇侧突起呈悬垂状的两叶/圆形，舌侧突起为雏形；V型形态型则包含宽扁、呈三角形且粗壮的前位牙齿，其主齿尖圆钝，带有1枚小齿尖，且唇侧带有低矮悬垂的小突。多变量分析结果佐证了对印度弓鲛类（Hybodontiformes）的定性评估结论。Pristrisodus新属的牙齿组织学特征显示，其与其他隆齿鲛科属种存在显著差异。提基组产出的淡水鲨类组合与其他脊椎动物微化石组合，与美国钦利群下特科瓦组的对应组合具有相似性。卡尼期（Carnian）时，弓鲛类凭借其广盐性特性，成功适应了印度的淡水水域环境。