Cranial anatomy and phylogenetic position of the titanosaurian sauropod Bonitasaura salgadoi

Knowledge of titanosaurian cranial anatomy has improved substantially in the last decade because several skulls have come to light or were restudied. The discovery of Bonitasaura salgadoi, a partial titanosaurian skeleton including cranial bones, permitted the definitive recognition of square jaws in a titanosaurian sauropod as well as a peculiar skull morphology that increases the morphological diversity of the group. Here we present a full description and illustration of the skull material of B. salgadoi. Among cranial bones, the lacrimal, quadrate, and dentary exhibit apomorphic differences from those of other titanosaurians. Conversely, the frontal and parietal are more conservative. A phylogenetic analysis recovers B. salgadoi as a member of the Titanosauria, related to mid−sized to large titanosauroids from the Turonian–Campanian of South America, in contrast to a previous hypothesis that suggested a nemegtosaurid affinity. The skull reconstruction presented here shows that the skull of B. salgadoi is anteroposteriorly short and dorsoventrally high, contrasting with the elongate skull of Rapetosaurus krausei.