New material of Dolichochampsa minima (Archosauria: Crocodylia) from the Cretaceous–Palaeogene El Molino Formation of Bolivia sheds light on the early evolution of Gavialinae

Four Late Cretaceous taxa have been suggested to be amongst the oldest gavialoids: ‘thoracosaurs’ from North America; Ocepesuchus eoafricanus from Africa; Portugalosuchus azenhae from Portugal; and Dolichochampsa minima from South America. The evolutionary relationships of these taxa to definitive gavialoids remain contentious. Resolving the evolutionary relationships of early gavialoids is important for understanding the timing of the origin of the clade and its potential distribution across landmasses. Here, we report new material of Dolichochampsa minima from the Late Cretaceous–early Paleocene (73–64 Ma) El Molino Formation of Bolivia that provides key anatomical information elucidating the evolutionary relationships of early gavialines. A phylogenetic analysis based on a revised and expanded morphological character data set recovers D. minima nested within Gavialinae. The other putative gavialoids, however, were resolved outside of Gavialoidea: Ocepesuchus was recovered within alligatorids; ‘thoracosaurs’ were recovered outside crown-group Crocodylia; and Portugalosuchus was recovered within ‘thoracosaurs’. This phylogenetic hypothesis implies that several characters associated with longirostry evolved independently in gavialines and ‘thoracosaurs’. The phylogenetic relationships and geographical distribution of early gavialines suggest a plausible centre of origination in Gondwana for the group, followed by multiple trans-oceanic dispersals during the Late Cretaceous to other landmasses and possible dispersals to South America from the peri-Tethys during the late Palaeogene.