Eosuchus lerichei is a gavialoid crocodylian from late Paleocene marine deposits of northwestern Europe, known from a skull and lower jaws, as well as postcrania. Its sister taxon relationship with the approximately contemporaneous species Eosuchus minor from the east coast of the USA has been explained through transoceanic dispersal, indicating a capability for salt excretion that is absent in extant gavialoids. However, there is currently no anatomical evidence to support marine adaptation in extinct gavialoids. Furthermore, the placement of Eosuchus within Gavialoidea is labile, with some analyses supporting affinities with the Late Cretaceous to early Paleogene “thoracosaurs.” Here we present novel data on the internal and external anatomy of the skull of E. lerichei that enables a revised diagnosis, with 6 autapormorphies identified for the genus and 10 features that enable differentiation of the species from Eosuchus minor. Our phylogenetic analyses recover Eosuchus as an early diverging gavialid gavialoid that is not part of the “thoracosaur” group. In addition to thickened semi-circular canal walls of the endosseous labyrinth and paratympanic sinus reduction, we identify potential osteological correlates for salt glands in the internal surface of the prefrontal and lacrimal bones of E. lerichei. These salt glands potentially provide anatomical evidence for the capability of transoceanic dispersal within Eosuchus, and we also identify them in the Late Cretaceous “thoracosaur” Portugalosuchus. Given that the earliest diverging and stratigraphically oldest gavialoids either have evidence for a nasal salt gland and/or have been recovered from marine deposits, this suggests the capacity for salt excretion might be ancestral for Gavialoidea. Mapping osteological and geological evidence for marine adaptation onto a phylogeny indicates that there was probably more than one independent loss/reduction in the capacity for salt excretion in gavialoids.
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Raoellid mammals are small artiodactyls from the Eocene of Asia, hypothesized to be closely related to stem Cetacea. Knowledge of the cranial and dental morphology of Raoellidae comes mostly from one species, Indohyus indirae. Here we describe new material of another raoellid genus, Khirtharia, based on material retrieved from the Kalakot area, Jammu and Kashmir. This new material, comprising an almost complete, lightly deformed cranium and a partial snout with associated partial mandible, greatly adds to our knowledge of raoellid morphology. It highlights the similarity of cranial characters with Indohyus, such as a long snout with raptorial incisors, a thick and narrow supraorbital region, a strong postorbital constriction, a triangular shaped braincase, and a thickened medial wall to the auditory bulla (involucrum). The new specimen is similar to Indohyus cranially but differs dentally in being more bunodont. The presence of these traits in two different raoellid genera suggests they may be present more broadly across Raoellidae. These characters are also observed in early cetaceans, highlighting the need to investigate their phylogenetic impact. Some cranial features support aquatic habits of members of this family.
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