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

Abstract

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.

A nearly complete skull of the sauropod dinosaurDiamantinasaurus matildaefrom the Upper Cretaceous Winton Formation of Australia and implications for the early evolution of titanosaurs

“…[ 40 ]. An early-branching position for Diamantinasauria within Titanosauria has received additional support in several recent studies [ 34 , 40 , 41 , 43 ]. Nevertheless, it is plausible that the presence of several seemingly plesiomorphic titanosaurian characters [ 40 , 41 ] simply indicates that Diamantinasauria occupies a position outside Titanosauria, rather than an early-branching position within, as recovered in our analyses applying extended implied weighting.…”

“…The teeth within the premaxilla of AODF 0906 are almost identical to those from the Diamantinasaurus matildae type (AODL 0085) and referred specimen (AODL 0127) sites, and those from the ‘Mitchell' site (AODL 0270; [ 43 ]). They also show some similarity to some of the sauropod teeth described from Lightning Ridge [ 33 , 35 ].…”

“…in Adobe Illustrator CC 2022 (modified from Poropat et al . [ 43 ], incorporating geological information from Vine [ 46 ] and Vine and Casey [ 47 ] (© Commonwealth of Australia (Geoscience Australia) 2022. This product is released under the Creative Commons Attribution 4.0 International Licence.…”

“…The apicobasal heights of the preserved tooth crowns range from 25.40 to 28.07 mm ( table 2 ). Thus, they are larger than all of the sauropod teeth described from the Griman Creek Formation [ 35 ], similar in size to the sauropod teeth from the sites that produced the Diamantinasaurus matildae holotype (AODL 0085) and referred (AODL 0127) specimens in the Winton Formation, and smaller than the sauropod teeth from AODL 0270, also in the Winton Formation [ 43 ]. The slenderness indices (SI = apicobasal length: mesiodistal width of crown ratio) of the premaxillary replacement teeth range from 2.33 to 2.74 ( table 2 ).…”

“…The AODF 0906 teeth are generally more slender than those from the Griman Creek Formation: the SI indices of these range from 1.36 to 3.10 (mean SI = 2.09), although only four of the 26 teeth sampled have SI indices greater than 2.40 [ 35 ]. The AODF 0906 teeth are also generally slenderer than those from AODL 0270, the SI indices of which range from 2.00 to 2.88 (with six of the 10 below 2.10) [ 43 ].…”