Dakotaraptor

Dakotaraptor (meaning "thief from Dakota") is a possible chimaeric genus of maniraptoriform theropod dinosaur that lived in western North America during the Late Cretaceous period. The remains have been found in the Maastrichtian-aged Hell Creek Formation, dated to the very end of the Mesozoic era, making Dakotaraptor potentially one of the last surviving dromaeosaurids, though other researchers have disputed its classification. One of the largest dromaeosaurids, measuring 4.35–6 m (14.3–19.7 ft) and weighing 220–350 kg (490–770 lb), the remains of D. steini were discovered in a multi-species bonebed. Elements of the holotype and referred specimens were later found to belong to trionychid turtles, and it is unclear whether further analysis of potential non-dromaeosaurid affinities of the holotype and referred material can be properly conducted, because currently the type specimen is housed in a private collection. Phylogenetic analyses of D. steini place it in a variety of positions within Dromaeosauridae.

In 2005, paleontologist Robert DePalma in Harding County, South Dakota discovered a fluvial bonebed bearing the remains of a variety of dinosaurian and non-dinosaurian remains, which yielded a partial skeleton attributed by DePalma to a large dromaeosaurid. Subsequently, the same site produced additional dromaeosaurid remains.

In 2015, the type species Dakotaraptor steini was named and described by Robert A. DePalma, David A. Burnham, Larry Dean Martin, Peter Lars Larson, and Robert Thomas Bakker. The generic name, Dakotaraptor, combines a reference to South Dakota and the Dakota people with the Latin word raptor, meaning "plunderer". The specific name, steini, honors paleontologist Walter W. Stein. Dakotaraptor was one of eighteen dinosaur taxa from 2015 to be described in open access or free-to-read journals.

The holotype, PBMNH.P.10.113.T, was found in a sandstone layer of the upper Hell Creek Formation, dating to the late Maastrichtian. It consists of a partial skeleton of an adult individual, albeit without a skull. It contains a piece of a back vertebra, ten tail vertebrae, both humeri, both ulnae, both radii, the first and second right metacarpals, three claws of the left hand, a right thighbone, both shinbones, a left astragalus bone, a left calcaneum, the left second, third and fourth metatarsal, the right fourth metatarsal, and the second and third claw of the right foot. An assigned furcula was later excluded from the specimen.

Apart from the remains of the holotype, bones were discovered in the site that also belonged to Dakotaraptor, but which represented a more gracile morph. These included the specimens PBMNH.P.10.115.T (a right shinbone), PBMNH.P.10.118.T (a connected left astragalus and calcaneum), and KUVP 152429 (originally identified as a furcula, but now also excluded from the known remains of Dakotaraptor). Additionally, four isolated teeth were referred (PBMNH.P.10.119.T, PBMNH.P.10.121.T, PBMNH.P.10.122.T, and PBMNH.P.10.124.T). These fossils are part of the collection of The Palm Beach Museum of Natural History. Other referred fossils are KUVP 156045 (an isolated tooth) and NCSM 13170 (a third supposed furcula that was later identified as not belonging to Dakotaraptor).

The elements originally identified as the furcula of Dakotaraptor were U- to V-shaped, suggested by the describers to be similar to many other dromaeosaurids, such as Velociraptor, and even the large spinosaurid theropod Suchomimus. In 2015, a study by Victoria Megan Arbour et al. proposed that the presumed Dakotaraptor furculae in fact represented a part of a turtle’s armor, the entoplastron of Axestemys splendida, a member of Trionychidae. In 2016, DePalma et al. recognized that none of the referred furculae actually belonged to Dakotaraptor and excluded them from its hypodigm. In 2024, even the dinosaurian elements of Dakotaraptor were questioned, with supposed traits diagnostic for dromaeosaurs also referrable to caenagnathids and ornithomimosaurians.

Dakotaraptor is exceptionally large for a dromaeosaurid, with an estimated adult length of 5.5 m (18 ft). In 2016, other estimations suggested a length of 4.35–6 m (14.3–19.7 ft) and a weight of 220–350 kg (490–770 lb).

This approaches the size of one of the largest known dromaeosaurids, Utahraptor. Dakotaraptor, however, does not have the proportions and adaptations of Utahraptor, but more closely resembles smaller dromaeosaurids, like Deinonychus.