The first record of a shortnose chimaera-like egg capsule from the Mesozoic (Late Jurassic, Switzerland).

Chondrichthyan egg capsules, fossil and recent, have a taxonomical significance that can provide important insights into the occurrence and reproductive strategy of their producers. However, the rare occurrence of fossil capsules and their sometimes difficult identification hinder our understanding of their systematics and significance. Laffonia from the Late Jurassic of Switzerland and its probable junior synonym, Pseudocaudina, from the Late Jurassic lithographic limestones of southern Germany, have been interpreted in a variety of ways including as a fructification of a plant, a possible egg capsule of a shark or ray, a presumed holothurian, a possible actinarian, or even a ctenophore. Here, we redescribe the holotype of Laffonia, which has a fusiform body that is ornamented with over seven longitudinal ribs and two narrow striated flanges at its lateral edges. These morphological features are incompatible with a diploblast or echinoderm affinity, but highly resemble the characteristics of certain holocephalan egg capsules in several respects. Our phylogenetic analysis places Laffonia within a group containing the Carboniferous fossil capsules Crookallia and Vetacapsula, as well as recent chimaerid capsules. Thus, we suggest that the Mesozoic Laffonia represents an intermediate morphotype between the Carboniferous species and extant chimaerid capsules. Laffonia is the only known fossil chimaerid-like capsule from the Mesozoic so far, which offers novel insights into the morphology and evolution of holocephalan egg capsules.

Supplementary information: The online version contains supplementary material available at 10.1186/s13358-025-00352-x.