Morphology, development and ecological implications of the dentition of Bajadasaurus pronuspinax

Abstract

The associated preservation between dentitions and dentigerous elements is crucial for understanding diverse biological features. Notwithstanding, their fossil record in Sauropoda is relatively seldom, compared to other skeletal elements. Here, the first partially complete dentition including upper and lower teeth in Dicraeosauridae is described, based on Bajadasaurus pronuspinax. This dentition lacks only one upper and two lower functional teeth. The dentigerous elements preserved replacement teeth, which reduce in length and number caudally. Tooth formation times and rates vary within the different elements, with a total mean replacement time of 40.7 days. The functional dentition shows three caudally directed patterns: reduction in size, reduction in curvature, and reduction in the occurrence of wear facets. The functional teeth number mirrors in the occlusal and sagittal planes. The replacement teeth count in Bajadasaurus is lower than the same for other diplodocoids. In this taxon, the tooth-replacement process fits the Zahnreihen with a Z-space-of-two model on the lower dentition, but this model results in a chaotic arrangement of the developmental pattern dorsally, probably due to a replacement mechanism of the whole upper dentition similar to Dicraeosaurus and Apatosaurus. Overall, the dental traits of Bajadasaurus suggest a plausible low-level specialist-feeding ecological niche for this taxon.