Terrific Tetanurae #10 The Wealden Tetanuran

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 thinking with Dr. Witton’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.

Like the Cretaceous fauna of the east coast, which is one of my primary research subjects, much of what we know about the fauna of the Wealden Supergroup is based on highly fragmentary remains. Sure, occasional gems like the mostly complete skeletons of Neovenator, Baryonyx, Eotyrannus, and Iguanodon 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 deal.

The tetanuran I will discuss today was described by Benson et. al. (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 the tyrannosauroid Eotyrannus (Hutt et. al., 2001). You would probably think this animal an allosauroid 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 information on the differences between this theropod and Neovenator), supporting the animal’s status as a basal tetanuran outside of Allosauroidea. The presence of this animal in a terrestrial ecosystem from the Early Cretaceous is unusual, as during this time allosauroids like Acrocanthosaurus were the most common large predators on land.

The presence of this theropod in the Wessex Formation shows that the environment it represents could support multiple medium-sized and large predators (Benson et. al, 2009, Hutt et. al., 1996).

Overall, this indeterminate 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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