Ancient Shed Teeth Show More Diverse Predators in Dinosaur Era

Jenn Hoskins
11th May, 2024

Ancient Shed Teeth Show More Diverse Predators in Dinosaur Era

The analysis of these thirty-two shed crowns identifies six distinct dental morphotypes attributed to Megaraptoridae (Figs. 2, 3), Alvarezsauridae (Fig. 5), and Abelisauridae plus a basal Abelisauroidea (Figs. 4, 6, 7), revealing a significantly higher diversity of theropod predators in the Turonian-Coniacian Portezuelo Formation than previously recognized.

Image adapted from: Meso et al. / CC BY (Source)

Key Findings

  • In Argentina's Portezuelo Formation, researchers identified six distinct types of theropod dinosaur teeth
  • Two tooth types suggest the presence of new species of megaraptorid and alvarezsaurid dinosaurs
  • Another tooth type may indicate a medium-sized abelisauroid living alongside larger abelisaurids
In the realm of paleontology, the discovery and identification of dinosaur species have long been guided by the examination of fossilized bones. However, teeth, often more abundant in the fossil record, can also provide significant insights into the diversity and relationships of these ancient creatures. A recent study by researchers at CONICET has shed new light on the theropod dinosaurs that once roamed the area of what is now the Portezuelo Formation in Argentina during the middle Turonian to the late Coniacian period[1]. Theropods are a diverse group of bipedal, carnivorous dinosaurs, some of which are the ancestors of modern birds. The study focused on thirty-two shed crowns—essentially the visible part of the teeth above the gumline—and utilized a combination of analytical techniques to categorize them into six distinct morphotypes, each representing different species or families of theropods. The significance of this study lies in its contribution to our understanding of the diversity of theropod dinosaurs in the Southern Hemisphere. Previous research has highlighted the presence of deinonychosaurs like Neuquenraptor argentinus in Gondwana, suggesting a wider distribution of these creatures than previously thought[2]. The current study expands on this by identifying two morphotypes that belong to the Megaraptoridae family, known for their gigantic claws. The researchers also identified three morphotypes that were ascribed to the Abelisauridae family, a group of predators characterized by their short snouts and horn-like structures above the eyes. This finding is intriguing as it aligns with earlier discoveries of abelisaurid teeth in the Jurassic deposits of Portugal, indicating that this family had a much earlier origin and a wider distribution than previously recognized[3]. Moreover, the study sheds light on the dental characteristics of megaraptorids, which have been elusive due to the scarcity of their in situ dentition in fossil records. The new findings from the Portezuelo Formation allow for a clearer depiction of megaraptorid teeth, which exhibit modest pseudoheterodonty—a variation in tooth shape—and a unique figure-of-eight basal cross-section[4]. This contributes to the understanding of their feeding habits and ecological roles. Interestingly, one of the morphotypes was identified as belonging to the Alvarezsauridae family, a group of small, feathered dinosaurs that were previously thought to be less diverse in the region. This discovery suggests that there was a second, previously undocumented alvarezsaurid species in the same ecosystem. The existence of a morphotype that combines features of both megaraptorids and abelisaurids indicates a potential for convergent evolution or even an undiscovered relationship between these two families. Such findings echo patterns of homoplasy—similar traits evolving independently—in other theropod groups, underscoring the complex evolutionary history of these dinosaurs[3]. Additionally, the study hints at the coexistence of medium-sized abelisauroids with larger abelisaurids, which could suggest a more intricate predator-prey dynamic and niche partitioning within the ecosystem. This is reminiscent of the diversity seen in noasaurines, another group of predatory theropods from Gondwana, which displayed a range of sizes and adaptations[5]. The results of the study emphasize the need for further exploration and excavation at the Sierra del Portezuelo locality. With each new discovery, our understanding of the theropod lineage and their global distribution continues to evolve. The findings from the Portezuelo Formation not only add to the diversity of known theropods but also challenge assumptions about the geographical and ecological boundaries of these prehistoric predators. As paleontologists continue to unearth the secrets of the past, the story of these fascinating creatures becomes ever more detailed and complex.

Animal ScienceEvolution

References

Main Study

1) Shed teeth from Portezuelo formation at Sierra del Portezuelo reveal a higher diversity of predator theropods during Turonian-Coniacian times in northern Patagonia

Published 10th May, 2024

https://doi.org/10.1186/s12862-024-02249-8

Related Studies

2) New evidence on deinonychosaurian dinosaurs from the Late Cretaceous of Patagonia.

Journal: Nature, Issue: Vol 433, Issue 7028, Feb 2005

3) Abelisauridae (Dinosauria: Theropoda) from the Late Jurassic of Portugal and dentition-based phylogeny as a contribution for the identification of isolated theropod teeth.

https://doi.org/10.11646/zootaxa.3759.1.1

4) The dentary of Australovenator wintonensis (Theropoda, Megaraptoridae); implications for megaraptorid dentition.

https://doi.org/10.7717/peerj.1512

5) A new desert-dwelling dinosaur (Theropoda, Noasaurinae) from the Cretaceous of south Brazil.

https://doi.org/10.1038/s41598-019-45306-9


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