Compared with crocodylomorph body fossils, the record of fossil crocodiloid eggs is scarce and poorly understood, a gap partially attributed to their typically thin eggshell, which is not conducive to preservation. A remarkable new association of well-preserved eggs and eggshells from the Adamantina Formation (Bauru Group, Upper Cretaceous) is described and compared to other known materials, while the significance of their unique oological features is discussed. These eggs constitute a new ootaxon, Bauruoolithus fragilis oogen. et oosp. nov., diagnosed by the following characteristics: elongate and elliptical egg with blunt ends; length-to-diameter ratio of 1:0.55; outer surface slightly undulating; shell thickness ranging from 0.15 to 0.25 mm; pore openings elliptical or teardrop-shaped, ranging from 30 to 80 lm in diameter; and shell units wider than higher, with the interstices forming an obtuse triangle. Specimens of Bauruoolithus also show only slight signs of extrinsic degradation that, coupled with the evidence that some of them constitute hatched eggs, suggests that the egg-laying taxon had a different pattern of egg incubation, in which the hatchling could break through the rather thin eggshell relatively easily and that the extrinsic degradation of the eggshell was not necessary. This contrasts with the pattern of incubation for all other known crocodylomorphs and crocodiloid eggs, where extrinsic degradation is a key component of the hatching process.
Knowledge on crocodyliform paleoneurology has significantly improved with development of computed tomography. However, studies so far have been able to reconstruct brain endocasts based only on single specimens for each taxon. Here for the first time, we reconstructed brain endocasts for multiple fossil specimens of the same crocodyliform taxon (Baurusuchus), consisting of complete skulls of two medium sized specimens, one large adult, and a late juvenile. In addition, we were able to reconstruct the inner ear anatomy of a fragmentary skull using microtomography. We present estimates of brain size using simple models, based on modern Crocodylia, able to adapt brain to endocranial cavity ratios to expected ontogenetic variation instead of using fixed ratios. We also analyzed relative brain sizes, olfactory ratios, facial sensation, alert head posture, best hearing frequencies, and hearing range. The calculated endocranial volumes showed that they can be greatly altered by taphonomic processes, altering both total and partial endocranial volumes. Reconstructed endocasts are compatible with different degrees of occupation along the endocranial cavity and some of their characteristics might be useful as phylogenetic characters. The relative brain size of Baurusuchus seems to be small in comparison to modern crocodilians. Sensorial abilities were somewhat similar to modern crocodilians and hearing ranges and best mean frequencies remarkably similar to modern taxa, whereas olfactory ratio values are a little higher. Differing from its modern relatives, Baurusuchus hypothesized alert head posture is compatible with a terrestrial habit.
The Upper Cretaceous Bauru Group deposits furnished several species of Crocodylomorpha, especially notosuchians. However, little is known about the feeding habits of this diverse group of crocodylomorphs. The dental histology is a destructive approach that can provide important information on tooth growth and feeding habits of fossil vertebrates. So far, few studies dealt with crocodylomorph dental histology and the ones available mainly focused on fossil and living neosuchians. In this work, we analyse the dental histology of three notosuchians commonly found in the Upper Cretaceous rocks of the Bauru Group: juvenile and adult Baurusuchidae, a large Sphagesauridae, and Mariliasuchus amarali. Our analyses indicate that tooth formation varied in these three taxa. In Mariliasuchus, a tooth took less than 2 months to be completely grown. On the other hand, in Sphagesauridae and Baurusuchidae, the tooth formation could take about 6 months to be completed. Mariliasuchus and Sphagesauridae have proportionally thicker enamel in comparison to Baurusuchidae. Additionally, the enamel thickness and its substantial development in the chewing area in Sphagesauridae indicate that apical advanced notosuchians are more adapted to process food items than more basal forms like Mariliasuchus.
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