Abstract
The early Middle Jurassic is regarded as the period when sauropods diversified and became major components of the terrestrial ecosystems. Not many sites yield sauropod material of this time; however, both cranial and postcranial material of eusauropods have been found in the Cañadón Asfalto Formation (latest Early Jurassic–early Middle Jurassic) in Central Patagonia (Argentina), which may help to shed light on the early evolution of eusauropods. These eusauropod remains include teeth associated with cranial and mandibular material as well as isolated teeth found at different localities. In this study, an assemblage of sauropod teeth from the Cañadón Asfalto Formation found in four different localities in the area of Cerro Condor (Chubut, Argentina) is used as a mean of assessing sauropod species diversity at these sites. By using dental enamel wrinkling, primarily based on the shape and orientation of grooves and crests of this wrinkling, we define and describe three different morphotypes. With the exception of one taxon, for which no cranial material is currently known, these morphotypes match the local eusauropod diversity as assessed based on postcranial material. Morphotype I is tentatively assigned to Patagosaurus, whereas morphotypes II and III correspond to new taxa, which are also distinguished by associated postcranial material. This study thus shows that enamel wrinkling can be used as a tool in assessing sauropod diversity.
Highlights
Sauropods are one of the most successful groups of dinosaurs; their presence in the fossil record stretches from the Late Triassic to the Late Cretaceous (e.g. [1,2,3,4])
The aim of this study is to present a morphological analysis of eusauropod teeth from localities within the Cañadón Asfalto Formation, in order to estimate eusauropod species diversity at these localities
Based on observations of the eusauropod toothrows and isolated teeth from the Cañadón Asfalto Formation (MPEF-PV 3341, MACN-CH 933, MPEF-PV 1670, MACN-CH 934), as well as from other taxa (e.g., Camarasaurus, diplodocids, Giraffatitan), it seems that enamel wrinkling pattern is conservative along the toothrow in sauropods, so that there is minimal intraspecific variation, but considerable interspecific variation
Summary
Sauropods are one of the most successful groups of dinosaurs; their presence in the fossil record stretches from the Late Triassic to the Late Cretaceous (e.g. [1,2,3,4]). Sauropods are one of the most successful groups of dinosaurs; their presence in the fossil record stretches from the Late Triassic to the Late Cretaceous The eusauropods diversified and became abundant in terrestrial ecosystems during the Jurassic. Using Dental Enamel Wrinkling to Define Sauropod Tooth Morphotypes period, and representatives of most important lineages of this clade gained a global distribution. Phylogenetic studies indicate that especially the Middle Jurassic was an important time in eusauropod evolution, with a proliferation of basal forms and the first appearance of neosauropods, including many of the lineages that radiated in the Late Jurassic and Cretaceous [5,6]. Middle Jurassic dinosaur localities are relatively rare [7], with most material coming from China e.g. Apart from the Chinese record, a few taxa are known from northern Africa [13,14,15,16], Madagascar [17,18] and Argentina [19,20,21,22,23,24,25,26]
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