Abstract
A braincase of the Cretaceous titanosaurian sauropod Malawisaurus dixeyi, complete except for the olfactory region, was CT scanned and a 3D rendering of the endocast and inner ear was generated. Cranial nerves appear in the same configuration as in other sauropods, including derived features that appear to characterize titanosaurians, specifically, an abducens nerve canal that passes lateral to the pituitary fossa rather than entering it. Furthermore, the hypoglossal nerve exits the skull via a single foramen, consistent with most titanosaurians, while other saurischians, including the basal titanosauriform, Giraffatitan, contain multiple rootlets. The size of the vestibular labyrinth is smaller than in Giraffatitan, but larger than in most derived titanosaurians. Similar to the condition found in Giraffatitan, the anterior semicircular canal is larger than the posterior semicircular canal. This contrasts with more derived titanosaurians that contain similarly sized anterior and posterior semicircular canals, congruent with the interpretation of Malawisaurus as a basal titanosaurian. Measurements of the humerus of Malawisaurus provide a body mass estimate of 4.7 metric tons. Comparison of body mass to radius of the semicircular canals of the vestibular labyrinth reveals that Malawisaurus fits the allometric relationship found in previous studies of extant mammals and Giraffatitan brancai. As in Giraffatitan, the anterior semicircular canal is significantly larger than is predicted by the allometric relationship suggesting greater sensitivity and slower movement of the head in the sagittal plane.
Highlights
Cretaceous titanosaurid material recovered from Malawi, Africa, was first described by Haughton (1928) and named Gigantosaurus dixeyi based on presumed similarity to specimens collected in Tanzania that were referred to as Gigantosaurus [1, 2]
The caudal semicircular canal falls within the 95% confidence interval of predicted size, but the lateral semicircular canal is smaller than the predicted size
CT scans of the braincase of Malawisaurus dixeyi recovered from the Dinosaur Beds of Malawi reveal insights into the paleoneuroanatomy and physiology of a basal titanosaur
Summary
Cretaceous titanosaurid material recovered from Malawi, Africa, was first described by Haughton (1928) and named Gigantosaurus dixeyi based on presumed similarity to specimens collected in Tanzania that were referred to as Gigantosaurus [1, 2]. The braincase of Malawisaurus dixeyi (Sauropoda: Titanosauria) funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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