A new miniature horned crocodile from the Quaternary of Aldabra Atoll, western Indian Ocean

摘要

A new crocodylid is described on the basis of fragmentary, but diagnostic, material from the Quaternary of Aldabra Atoll. It differs from all other known crocodylians, living or extinct, in having a prominent semicircular crest, or "horn," on the dorsolateral margin of the squamosal. Unlike the horns seen in some living Crocodylus, the apex of each horn was at its midpoint anterior to the external otic aperture and not near its posterior end. It also has a highly vaulted premaxillary palate and an anterodorsally-oriented external naris, and dorsal exposure of the supraoccipital on the skull table was extensive. Phylogenetic relationships of the new form are unclear, making its biogeographic origins difficult to trace, but it was very likely an immigrant from elsewhere and not endemic to Aldabra Atoll, as it occurs in deposits formed shortly after a period of submergence ended 120,000 years ago.