Relatively low tooth replacement rate in a sauropod dinosaur from the Early Cretaceous Ruyang Basin of central China

The dentition of the Late Jurassic dwarf sauropod Europasaurus holgeri from northern Germany: ontogeny, function, and implications for a rhamphotheca-like structure in Sauropoda

The basal macronarian sauropod Europasaurus holgeri is known only from the Late Jurassic of the Langenberg Quarry near Goslar, Lower Saxony, Germany. Europasaurus has been identified as an insular dwarf and shows a clear resemblance to Camarasaurus and Giraffatitan. This study provides a detailed description of the dentition of Europasaurus based on an array of fossils outstanding in their abundance, variety of preservation, and ontogenetic range. Dental morphology for the replacement and functional dentitions, the tooth replacement pattern, and implications for food intake are described for the Europasaurus dentition, which is characterized by broad-crowned teeth. Characteristic features for Europasaurus are the presence of denticles on replacement teeth, the wrinkled enamel, and large wear facets both on the apex and on the carinae of the tooth crowns. The partially articulated skull SNHM-2207-R and isolated tooth rows DfmMh/FV 580.1 and DfmMh/FV 896.7 suggest the presence of strong connective tissue partially covering the teeth. This connective tissue would have provided stability and protection for the teeth. Evidence for this connective tissue include exposed tooth necks, in-situ teeth with strongly resorbed roots which no longer would have been connected to the jaw bone, and wrinkled enamel and its surface pattern. The same features can be observed in other sauropod taxa as well. We therefore suggest that eusauropods in general possessed this connective tissue structure, which may be an autapomorphy of the group. Possibly, this hypothetical structure is homologous to the rhamphotheca in birds and some non-avian theropods, which, however rarely, show such a close integration of keratinous tissue and teeth that we hypothesize here.

Sauropod dinosaur teeth from the lower Upper Cretaceous Winton Formation of Queensland, Australia and the global record of early titanosauriforms

The Upper Cretaceous Winton Formation of Queensland, Australia, has produced several partial sauropod skeletons, but cranial remains-including teeth-remain rare. Herein, we present the first description of sauropod teeth from this formation, based on specimens from three separate sites. An isolated tooth and a dentary fragment from the Diamantinasaurus matildae type locality are considered to be referable to that titanosaurian taxon. A single tooth from the D. matildae referred specimen site is similarly regarded as being part of that individual. Seventeen teeth from a new site that are morphologically uniform, and similar to the teeth from the two Diamantinasaurus sites, are assigned to Diamantinasauria. All sauropod teeth recovered from the Winton Formation to date are compressed-cone-chisel-shaped, have low slenderness index values (2.00-2.88), are lingually curved at their apices, mesiodistally convex on their lingual surfaces, and lack prominent carinae and denticles. They are markedly different from the chisel-like teeth of derived titanosaurs, more closely resembling the teeth of early branching members of the titanosauriform radiation. This provides further support for a 'basal' titanosaurian position for Diamantinasauria. Scanning electron microscope microwear analysis of the wear facets of several teeth reveals more scratches than pits, implying that diamantinasaurians were mid-height (1-10 m) feeders. With a view to assessing the spatio-temporal distribution of sauropod tooth morphotypes before and after deposition of the Winton Formation, we provide a comprehensive continent-by-continent review of the early titanosauriform global record (Early to early Late Cretaceous). This indicates that throughout the Early-early Late Cretaceous, sauropod faunas transitioned from being quite diverse at higher phylogenetic levels and encompassing a range of tooth morphologies at the start of the Berriasian, to faunas comprising solely titanosaurs with limited dental variability by the end-Turonian. Furthermore, this review highlights the different ways in which this transition unfolded on each continent, including the earliest records of titanosaurs with narrow-crowned teeth on each continent.