Terrific Tetanurae #10 The Wealden Tetanuran

Yay! We have reached the tenth addition of Terrific Tetanurae! 300 views in May and now this! That’s awesome! Thanks everyone for your continuous support, and enjoy the article! 

Remember the post on Mark Witton’s blog I linked to in the last addition of PaleoNews? Well, the second addition of that art showcase has since come out and got me wondering with Mark’s mention of the presence of basal tetanurans in the supergroup. I’ve done some snooping, and it turns out the subject of basal tetanurans in the Wealden Supergroup is quite interesting, and deserves to be discussed on this blog.

Now I am no expert on Wealden fauna, but the supergroup holds a special place in my heart for a reason. Like the Cretaceous fauna of the East Coast, which, as I’ve mentioned, is one of my primary research areas (that and the paleobiology of carcharodontosaurid dinosaurs), much of what we know about the fauna of the Wealden Supergroup is based on highly fragmentary remains. Sure, the occasional gems like the partial and mostly complete specimens of animals like Neovenator, Baryonyx, Eotyrannus, Iguanodon, and various iguanodonts are incredibly important to our understanding of the paleoecology of the environment the supergroup represents, but more fragmentary specimens like that of the “Ashdown Maniraptoran” also tell us a good amount about the Wealden ecosystem.

Today, the tetanuran we will be talking about was described by Benson et. al. in 2009, and from what we can tell, it was pretty big. This animal hails from the Wessex Formation (Benson et. al., 2009) where it coexisted with such theropods as the tyrannosauroid Eotyrannus (Hutt et. al., 2001). This theropod is classified as a basal tetanuran (Benson et. al., 2009), but you would probably hypothesize this animal an allosaurid if you only heard “Large Basal Tetanuran from Wessex Formation”. Yet, the specimen differs a good amount even from Neovenator (see this post by Darren Naish for more not-contained-within-a-scientific-paper information on the differences between this theropod and Neovenator),supporting the animals status as a basal tetanuran outside of allosauroidea. The presence of this animal is quite unique among the terrestrial ecosystems of the Early Cretaceous, as, during this time, allosaurids, such as Acrocanthosaurus, were the most common large predators on land.

Allosaurids, like the carcharodontosaurid Mapusaurus, were the more common large predators of the Early and mid-Cretaceous. Artwork by the author, 2015.

Allosaurids, like the carcharodontosaurid Mapusaurus, were the more common large predators of the Early and mid-Cretaceous. Artwork by the author, 2015.

The presence of this theropod in the Wessex Formation shows that that environment could support multiple medium-sized and large predators, as Eotyrannus  and Neovenator are also present in the Wessex Formation (Benson et. al, 2009, Hutt et. al., 1996). This has implications for understanding the biomass of prey fauna in the Wessex Formation, but also might have something to do with niche partitioning.

The Wealden Tetanuran by the author. Colored pencils on paper, 2015.

The Wessex Formation Basal Tetanuran by the author. Colored pencils on paper, 2015.

Overall, this tetanuran shows how much we can learn about the paleoecology of a formation from fragmentary specimens. This theropod, at its heyday, would have taken up a predatory niche, hunting the various ornithopods and sauropods of the formation. The Early Cretaceous, however, would be the only time this animal would thrive. Along with the giant allosaurids of the Early and mid-Cretaceous (~145-90 MYA), this tetanuran would be replaced by the larger abelisaurids and tyrannosauroids of the Late Cretaceous, such as Carnotaurus sastrei and Tyrannosaurus rex. 

Large tyrannosauroids, like T. rex, replaced the large basal tetanurans and allosaurids of the Early and mid-Cretaceous as top predators during the Late Cretaceous. Photo by the author, 2015.

Large tyrannosauroids, like T. rex, replaced the large basal tetanurans and allosaurids of the Early and mid-Cretaceous as top predators during the Late Cretaceous. Photo by the author, 2015.

References 

1. Benson, R. B. J.; Brusatte, S. L.; Hutt, S.; Naish, D. 2009. “A new large basal tetanuran (Dinosauria: Theropoda) from the Wessex Formation (Barremian) of the Isle of Wight, England.” Journal of Vertebrate Paleontology 29: 612-615.

2. Hutt, S.; Naish, D.; Martill, D.M.; Barker, M.J.; Newbery, P. .2001. “A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Cretaceous) of southern England.” Cretaceous Research 22: 227–242.

3. S. Hutt; D. M. Martill; M. J. Barker. 1996. “The first European allosauroid dinosaur (Lower Cretaceous, Wealden Group, England).” Neues Jahrbuch für Geologie und Paläontologie Monatshefte 1996(10):635-644.

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