Many of the egg cases of oviparous chondrichthyans remain unknown and undescribed in the literature. Egg cases can be a useful taxonomic character for species distinction and can be a valuable indicator of a species distribution in the field. In this study, the egg cases for 9 of the 10 nominal species of Heterodontus are described and compared, and the terminology and methodology for studying them are standardized. Heterodontus egg cases are distinct and easily identifiable from other oviparous egg cases by having a unique corkscrew shape formed by a pair of lateral keels spiraling along its length. Heterodontus egg cases range between 7.5 and 14.5 cm in egg case length, 3.7 and 5.8 cm in egg case width at midportion, and have 0.75-4 complete rotations. Morphometric measurements of egg cases from the nine species were subjected to multivariate analysis, with unique characters enabling distinction between them. Egg cases can be separated into three morphotypes: the "wide keels lacking tendrils" group, the "narrow keels with tendrils" group, and the "wide keels with tendrils" group. The egg case of Heterodontus ramalheira remains unknown.
Keywords: Heterodontus; comparative morphology; egg cases; hornshark; oviparous; taxonomy.
© 2024 The Author(s). Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.