Sailing to Gondwana: multiple waves of spinosaurid dispersal to the southern continents

Spinosaurid theropods exhibited a relatively widespread distribution during the Cretaceous Period; however, biogeographical analyses have been limited, largely owing to their fragmentary nature and uncertainties in spinosaurid phylogeny. We conducted a biogeographical analysis of Megalosauroidea, with a focus on Spinosauridae, using the R package 'BioGeoBEARS' on multiple phylogenetic trees to test their probable dispersal patterns. The best-fit models suggest that spinosaurid evolutionary history was influenced by geodispersal followed by narrow and widespread vicariance, as well as regional sympatry between co-occurring taxa. Within Spinosauridae, we find at least two distinct dispersals from Europe into Africa and South America, as well as at least one dispersal from Europe into Asia. Based on existing climate model data, spinosaurids generally appear to occur in high mean annual temperature semi-aquatic environments (approx. 26.1-33.1°C) with relatively minimal seasonal variation (approx. ±8.46°C), which may have influenced their dispersal capability, as these preferences appearmore constrained compared with those of other medium-to-large theropods. These results imply a more limited biogeographical distribution for Spinosauridae compared with other clades, which may be owing to climatic dispersal barriers and environmental factors.