Dakotaraptor steini model, WIP.
Dakotaraptor steini was a truly gigantic dromaeosaur, only exceeded by Utahraptor ostrommaysorum in size. However, Dakotaraptor does not share the proportions or adaptations found in Utahraptor - its proportions more closely resemble those of smaller dromaeosaurids such as Deinonychus (DePalma et al., 2015). The total estimated length of Dakotaraptor is approximately 5.5 meters.
The remains of Dakotaraptor were found in Harding County, South Dakota by Robert DePalma in 2005, and the species description was published 5 years later. The holotype (PBMNH.P.10.113.T), consists of a partial skeleton (lacking the skull) of an adult animal, consisting mainly of forelimb and hindlimb elements, though a single fragmentary dorsal centrum, furcula, and 20 caudal vertebrae were also preserved. The description also included 9 paratype specimens from the same site, though these seem to represent a more gracile morphotype. These paratype specimens consist of hindlimb elements, several furculae, and isolated teeth (DePalma et al., 2015).
One particularly fascinating aspect of the Dakotaraptor remains is that the left ulna clearly shows the ulnar papilli, or quill knobs, like those found in some other dinosaurs as well as in modern birds. Based on the spacing of the knobs, it is estimated that there were 15 secondary wing feathers branching off the ulnar part of the forelimb (DePalma et al., 2015). Unfortunately, remains of the phalanges and other forelimb elements are not well enough preserved to determine the number/arrangement of feathers across the entire wing.
When a phylogenetic analysis of the Dromaeosauridae was conducted, it was found that Dakotaraptor steini was sister to Dromaeosaurus albertensis, and these two taxa in turn were sister to Utahraptor ostommaysorum (DePalma et al., 2015).
Dakotaraptor represents a significant leap in our understanding of the paleoecology of the Hell Creek Formation. Prior to its discovery and subsequent description, there was a strange dichotomy of carnivorous dinosaurs - small maniraptorans, and Tyrannosaurus. However, Dakotaraptor represents a transitional size form between these two groups, and as such requires us to reanalyze our views of the ecological and trophic interactions among dinosaurs and other taxa from Hell Creek. Additionally, the presence of two distinct morphotypes adds to our knowledge of the dynamics of body size in dromaeosaurids (DePalma et al., 2015). In fact, it may actually be evidence for sexual dimorphism - though if this is the case we do not know which morph represents males and which represents females.
Another interesting possibility is that Dakotaraptor may have competed with immature T. Rex (or mature Nanotyrannus lancensis, if it is indeed a distinct species), partially due to the possibility that it hunted in packs (DePalma et al., 2015). If this is the case, it would certainly be an amazing sight to behold!
Well, I hope you all enjoyed the very last dinosaur Creature Feature! Next week we will start to get into the less well-known vertebrates from Hell Creek!
Acknowledgements:
DePalma, Robert A.. Burnham, David A, Martin, Larry D, Larson, Peter L, & Bakker, Robert T. 2015. The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation. Paleontological Contributions (14).
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