Internal structure of ichthyosaur rostrum from the Upper Jurassic of Poland with comments on ecomorphological adaptations of ophthalmosaurid skull

Abstract

ABSTRACT This study presents a detailed analysis of a semi-articulated finding of an ichthyosaur Ophthalmosauridae indet. rostrum fragment from the Upper Jurassic (Oxfordian) in the Morawica quarry in the Holy Cross Mountains (Southeastern Poland). The specimens are preserved as transverse cross-sections of the large rostrum on the surface of two limestone slabs. 3D virtual reconstructions of these fossils widen knowledge on the internal morphology of the ophthalmosaurid ichthyosaurs cranial region and the functional adaptations and palaeoecology of these marine reptiles. New information about the rostral cavity is provided from three-dimensional models of preserved structures. This Ophthalmosauridae indet. Specimen has a relatively large and wide nasal cavity. We proposed a new model of saturation-inhalation of the ophthalmosaurid ichthyosaurs skull, which is an open system connecting external and internal nares of the animal. This ecomorphological adaptations of ophthalmosaurid skull were useful during the feeding near the water surface in the two-dimensional habitats of shallow sea and sky and also in the deeper three-dimensional marine environment. The function described here is parsimonious with the Late Jurassic shallow marine environment of the Holy Cross Mountains.