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Argochampsa krebsi is a gavialoid crocodylian from the early Paleogene of North Africa. Based on its recovered phylogenetic relationship with South American species, it has been inferred to have been capable of transoceanic dispersal, but potential anatomical correlates for a marine lifestyle have yet to be identified. Based on CT scans of a mostly complete and well-preserved skull, we reconstruct the endocranial anatomy of Argochampsa and compare it to that of other gavialoids. We demonstrate that Argochampsa possesses concave depressions on the internal surface of the prefrontals and lacrimals, which have been inferred to represent osteological correlates for salt glands in unequivocally marine metriorhynchoid thalattosuchian crocodyliforms. The presence of these salt glands suggests that Argochampsa likely frequented pelagic environments and provides additional support for the capability of transoceanic dispersal within Gavialoidea. We also newly interpret osteological correlates for salt glands in the Miocene north African gavialoid Sutekhsuchus dowsoni, providing further support that saltwater tolerance was widespread and possibly ancestral in Gavialoidea, given that they have been previously reported in the Late Cretaceous-early Paleogene species Eosuchus lerichei and Portugalosuchus azenhae. In addition to these gavialoids, as well as metriorhynchids, we also identify these osteological salt gland correlates in the Paleocene northwest African dyrosaurid Rhabdognathus aslerensis, which represents another crocodyliform lineage thought to be capable of transoceanic dispersal. Given that dyrosaurids, gavialoids, and metriorhynchoids are distantly related lineages, the evolution of salt glands is likely a convergent ecological adaptation to the occupation of pelagic environments. Nevertheless, we demonstrate limited evaluation of the presence of these osteological correlates across Crocodyliformes, including within most extant species, such that it remains possible that they are much more widespread., (© 2024 The Author(s). Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

The interrelationships of the extant crocodylians Gavialis gangeticus and Tomistoma schlegelii have been historically disputed. Whereas molecular analyses indicate a sister taxon relationship between these two gavialoid species, morphological datasets typically place Gavialis as the outgroup to all other extant crocodylians. Recent morphological-based phylogenetic analyses have begun to resolve this discrepancy, recovering Gavialis as the closest living relative of Tomistoma; however, several stratigraphically early fossil taxa are recovered as closer to Gavialis than Tomistoma, resulting in anomalously early divergence timings. As such, additional morphological data might be required to resolve these remaining discrepancies. 'Tomistoma' dowsoni is an extinct species of gavialoid from the Miocene of North Africa. Utilising CT scans of a near-complete, referred skull, we reconstruct the neuroanatomy and neurosensory apparatus of 'Tomistoma' dowsoni. Based on qualitative and quantitative morphometric comparisons with other crocodyliforms, the neuroanatomy of 'Tomistoma' dowsoni is characterised by an intermediate morphology between the two extant gavialoids, more closely resembling Gavialis. This mirrors the results of recent studies based on the external anatomy of these three species and other fossil gavialoids. Several neuroanatomical features of these species appear to reflect ecological and/or phylogenetic signals. For example, the 'simple' morphology of their neurosensory apparatus is broadly similar to that of other long and narrow-snouted (longirostrine), aquatic crocodyliforms. A dorsoventrally short, anteroposteriorly long endosseous labyrinth is also associated with longirostry. These features indicate that snout and skull morphology, which are themselves partly constrained by ecology, exert an influence on neuroanatomical morphology, as has also been recognised in birds and turtles. Conversely, the presence of a pterygoid bulla in Gavialis and several extinct gavialoids, and its absence in Tomistoma schlegelii, could be interpreted as a phylogenetic signal of crocodylians more closely related to Gavialis than to Tomistoma. Evaluation of additional fossil gavialoids will be needed to further test whether these and other neuroanatomical features primarily reflect a phylogenetic or ecological signal. By incorporating such previously inaccessible information of extinct and extant gavialoids into phylogenetic and macroecological studies, we can potentially further constrain the clade's interrelationships, as well as evaluate the timing and ecological association of the evolution of these neuroanatomical features. Finally, our study supports recent phylogenetic analyses that place 'Tomistoma' dowsoni as being phylogenetically closer to Gavialis gangeticus than to Tomistoma schlegelii, indicating the necessity of a taxonomic revision of this fossil species., (© 2023 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)