Dakotaraptor steini: Ghost of the Floodplain Forest

Dakotaraptor-preview1.jpg

"DAKOTARAPTOR! DAKOTARAPTOR! DAKOTARAPTOR! DAKOOOOOOTARAPTOR!" - Henry Meyers, October 29th, 2015 It's understandable if you're not quite as excited as Henry was when he found out about Dakotaraptor, but there is a lot to be excited about. For those of you who aren't aware, Dakotaraptor steini is Hell Creek's newly described, large-bodied dromaeosaur, representing a major new addition to an already famous menagerie and paints a much more nuanced picture of Hell Creek's ecosystem. Dakotaraptor is described based on an associated partial skeleton (PBMNH.P.10.113.T) of an individual that, in life, would have approached 5m in length and may have massed out at more than 200kg (around 440lbs).

Dakotaraptor steini concept art by RJ Palmer. Our team is super excited to implement this amazing discovery into Saurian. Size and proportions based on an earlier revision of the publication and may be subject to change.

[one_third]

Dakotaraptor wing reconstruction. Photo by Robert DePalma, used with permission.

[/one_third]

In addition to being roughly the size of the iconic "Raptors" from Jurassic Park, there are two very exciting skeletal features preserved in Dakotaraptor. The paper describes a massive dromaeosaur sickle claw on the middle toe. It measures 16 cm from top to bottom and 24 cm along the outer curve. This was an impressively large raptorial claw, even for an animal this size. The ulna, a bone in the forearm, bares 15 large and distinct quill knobs, or ulnar papillae, which are reinforced attachment points on the wings of birds and other dinosaurs where the large, pennaceous feathers attach. This makes Dakotaraptor the largest known dinosaur with confirmed wings.

Dakotaraptor was discovered in South Dakota at a fine grain sandstone (Konzentrat-Lagerstätte) site that offers the potential for exceptional fossil preservation, known as Bone Butte. It is most likely located within the upper 20m of the Hell Creek Formation (DePalma, 2010).

One of the most exciting implications of Dakotaraptor is how it fits into what we know of the Hell Creek ecosystem. Prior to this discovery, it was believed that different growth stages of tyrannosaur were the primary occupant of every major medium and large carnivore niche, and there was even some suggestion that tyrannosaurs suppressed or out competed any other potential ecological rivals. Dakotaraptor soundly turns this notion on its head, but it does so by illustrating a major difference in ecology. Subadult and juvenile tyrannosaurs are long legged pursuit predators, while Dakotaraptor, like most dromaeosaurs, appears built for ambush and grappling with prey. By exploiting different life strategies, Dakotaraptor was able to survive alongside tyrannosaurs while potentially utilizing the same prey resources. Despite this partitioning, Dakotaraptor appears to have been 'Ghost of the Forest', a rare component of the Hell Creek Fauna. In over 100 years of intensive sampling, this is the first time we've found enough of Dakotaraptor to recognize its existence, while we have dozens of specimens of Tyrannosaurus rex.

Dakotaraptor concept art compared to Acheroraptor and a young Tyrannosaurus.

So the question you've all probably been asking since the beginning of the post, how does Dakotaraptor influence Saurian? As the 'missing competitor' to subadult Tyrannosaurus, Dakotaraptor adds a much needed layer of competition to this portion of the ecosystem. In modern ecosystems, organisms who are drawing upon the same pool of prey resources have a vested interest in both avoiding injury while also eliminating potential competition for said resources. Predators often resolve this dilemma by purposefully targeting the young of their competitors. In sub-Saharan Africa for example, lions and hyenas will kill each others young with no intent to consume them as a way to eliminate potential future competition (Schaller, 1976). This tendency to purposefully eliminate potential competitors can even extend down the food chain. In Yellowstone, wolves will kill coyotes, foxes and bobcats as a means to increase the potential prey base available to them. (LiveScience 2007) This behavior is known as Intraguild Predation, and we think it will add significantly to Saurian's gameplay.

As a side note, Dakotaraptor is something of a vindication for those of us who have been working on on Saurian since the the beginning. Early on, when we were first researching Hell Creek, we encountered numerous references to a 'saurornitholestine' and the occasional mention of a phantom 'large dromaeosaurine' or images of large dromaeosaur teeth would crop up in google searches, usually on the pages of commercial fossil dealers. As mentioned in the paper, it is probable that all of these do in fact belong to Dakotaraptor, but at the time there was no hard evidence to support this animal's existence. The publishing of Acheroraptor in 2013 appeared to resolve this controversy for us; the saurornitholestine and the 'dromaeosaur' appeared to be the same animal. Now with the publication of Dakotaraptor, we've come full circle, and both animals that were basically known only from teeth are now named and far better understood than when we started.

References * DePalma et al. 2015, The first giant raptor (theropoda: dromaeosauridae) from the latest Cretaceous (Hell Creek Formation, South Dakota), Paleontological Contributions vol. 15. * DePalma, 2010, Geology, taphonomy, and paleoecology of a unique upper Cretaceous bonebed near the Cretaceous-Tertiary boundary in South Dakota, Florida Atlantic University 2007. * LiveScience Staff, 2007, Coyotes cower in wolf territory, LiveScience, [http://www.livescience.com/1865-coyotes-cower-wolf-territory.html] * Schaller 1976, Serengeti Lion: A Study in Predator-Prey Relationships, University of Chicago Press, pp. 337