Dakotaraptor steini was named in 2015 as a very large dromaeosaurid from the upper Hell Creek Formation of South Dakota. The original reconstruction reached about 5.5 metres and combined long legs, a large second-toe claw and possibly feather-bearing forearms.
The taxon quickly became controversial. One element in the holotype and two referred bones described as theropod furculae proved to be parts of softshell-turtle shells. They were formally removed, while the remaining disarticulated bones may themselves represent more than one animal or taxon. Dakotaraptor is therefore a published name with an unstable anatomical foundation.
Quick facts
| Scientific name | Dakotaraptor steini DePalma et al., 2015 |
|---|---|
| Proposed group | Dromaeosauridae, Eudromaeosauria |
| Age | Late Cretaceous, late Maastrichtian, shortly before the K–Pg boundary |
| Range | Harding County, South Dakota, United States |
| Formation | Hell Creek Formation |
| Holotype | PBMNH.P.10.113.T, disarticulated bones from a multi-species accumulation |
| Original length | Approximately 5.5 m |
| Skull | Not preserved |
| Diet | Carnivorous if the dromaeosaurid interpretation is correct |
| Status | Disputed because the material may be composite |
Testing a disputed skeleton
Vertebrae and limb bones were published together, but proximity in a mixed deposit does not prove one skeleton.
Three supposed furculae were softshell-turtle entoplastra and were formally removed from the referred material.
The estimate scales large limb bones as one dromaeosaurid. Reassignment would require a new reconstruction.
Family relationships favour plumage, while the proposed quill knobs matter only if the ulna belongs to the named taxon.
Discovery and naming
Robert DePalma found the material in 2005 in Harding County. It came from the upper Hell Creek Formation, within tens of metres of the end-Cretaceous boundary. DePalma and colleagues named D. steini in 2015. The genus combines Dakota with Latin raptor, and the species honours palaeontologist Walter Stein.
The holotype, PBMNH.P.10.113.T, was deposited at the Palm Beach Museum of Natural History and initially interpreted as an adult skeleton. The site was a multi-species bone accumulation, however, so association requires anatomical evidence in addition to spatial closeness.
What remains after correction
After removal of the supposed furcula, the listed holotype includes part of a dorsal vertebra, ten tail vertebrae, paired humeri, ulnae and radii, hand elements, a right femur, both tibiae, ankle and metatarsal elements and toe claws. Separate leg bones and teeth were also referred.
The collection sounds extensive but is not articulated. No skull, neck, pelvis or dependable torso sequence joins the elements. Bones could have entered the deposit from several animals after transport or separate deaths. That makes the case different from a single partial skeleton preserved in anatomical order.
The turtle-bone correction
Three U-shaped elements were originally identified as furculae, the fused clavicles of theropods. Comparison with Hell Creek turtles showed that they were entoplastra, central bones from the lower shell of a softshell turtle similar to Axestemys splendida.
The original authors accepted the finding and issued a correction that removed all three from the hypodigm. Correcting one error is a strength of scientific review, but it also demonstrates that the original assemblage included another vertebrate and justifies rechecking every isolated element.
Size and the giant second-toe claw
The largest published tibia is about 67.3–67.8 centimetres long and the femur about 55.8 centimetres. Scaling against dromaeosaurids produced the original body length near 5.5 metres. Mass estimates of several hundred kilograms are even more dependent on the chosen model and the assumption that the compared bones belong together.
A second referred tibia is smaller and more slender. The first description proposed sex or individual variation, but without associated skeletons it could instead reflect age or a different theropod. Our size guide explains why one headline value cannot replace the underlying range and material.
A large second-toe ungual, about 16 centimetres in a straight line and longer around its outer curve, supported the giant “raptor” interpretation. If correctly identified, it was a raised grasping claw. No trace records how the animal used it.
Feathers and classification
The original study described regularly spaced marks on an ulna as attachment points for large feathers. Similar quill knobs occur in Velociraptor. If this ulna belongs to a large dromaeosaurid, it supports wing-like forearm feathers in a non-flying animal.
No feather impressions accompany the bones, and disputed association applies to the ulna too. Dromaeosaurids are expected to be feathered from broader comparative evidence, but “Dakotaraptor’s quill knobs” remain conditional on identification. The evidence rules are set out in the integument guide.
Phylogenetic analyses placed the scored material among eudromaeosaurs, sometimes near large Utahraptor. Later authors highlighted probable chimerism, and a large theropod analysis stated that a multi-taxon hypodigm could not yet be excluded. This is not a formal synonymisation, but it makes the precise family position unstable.
Hell Creek without a behavioural story
Hell Creek recorded rivers, floodplains, wetlands and wooded lowlands at the end of the Cretaceous Period. Tyrannosaurus rex, Triceratops, Edmontosaurus, armoured dinosaurs, turtles and mammals shared the formation.
Co-occurrence does not prove interaction. Without a secure skull, tooth row or feeding trace, Dakotaraptor cannot confidently be assigned a particular prey or cast as a pack-hunting rival of Tyrannosaurus. A large feathered dromaeosaur is a plausible illustration of the original diagnosis, not a complete fossil portrait.
Evidence, inference and reconstruction
| Evidence level | Examples |
|---|---|
| Directly published | Disarticulated vertebrae and limb bones from a mixed Hell Creek accumulation |
| Corrected error | Three “furculae” were softshell-turtle entoplastra and are excluded |
| Conditional inference | About 5.5 m length, dromaeosaurid identity and large forearm feathers |
| Unknown | Skull shape, exact skeleton, colour, prey, speed and social behaviour |
Frequently asked questions
Is Dakotaraptor a valid genus?
The name was formally published and a correction removed turtle bones, but several studies regard the remaining material as potentially mixed. A comprehensive revision is still needed.
Was Dakotaraptor really 5.5 metres long?
That estimate came from scaling large limb bones in the original description. It depends on those bones belonging to one giant dromaeosaurid and may change if the material is reassigned.
Did Dakotaraptor have feathers?
Dromaeosaurids are strongly expected to have feathers. Supposed quill knobs on one ulna may support large forearm feathers, but the taxonomic identity of individual bones remains disputed.
Why were turtle bones included with Dakotaraptor?
The fossils came from a multi-species accumulation. Three U-shaped softshell-turtle plastron bones were mistaken for theropod furculae and later formally removed.