Temporal range: Late Jurassic
The holotype or type specimen the genus is based on, AC 663, is part of the collection of the Amherst College Museum of Natural History. It was collected by professor Frederic Brewster Loomis. However, the only available information regarding its provenance is that given on the label: "Lance Creek", a county in east Wyoming. Loomis himself thought that it stemmed from the Lance Formation, dating from the Late Cretaceous Maastrichtian.
In 1963 the specimen was brought to the attention of John Stanton McIntosh, who later, together with William Coombs and Dale Russell, decided to create a new genus and species for it. The type species is Dyslocosaurus polyonychius. The genus name is derived from Greek dys, "bad, "poor", and Latin locus, "place", a reference to the lack of knowledge about the exact site it was discovered in. The specific name is derived from Greek polys, "many", and onyx, "claw". The describers interpreted the remains, consisting of some limb bones, as those of a diplodocid dinosaur. From this they concluded that it in fact dated from the Late Jurassic Period, like most diplodocids. The species would then be unique in having four, or perhaps five, claws on the foot, whereas other diplodocids have only three — hence the specific name. A species similar to Dyslocosaurus would have made the tracks of the ichnospecies Brontopodus birdi from the Early Cretaceous, that also features four claws.
In 1998 Paul Sereno and Jeffrey A. Wilson gave an alternative interpretation: the specimen would come from the Lance Formation after all but be a chimera: in this case a mix up of titanosaur limb bones and theropod phalanges.
- McIntosh, J., Coombs, W. and Russell, D., 1992, "A new diplodocid sauropod (Dinosauria) from Wyoming, U.S.A.". Journal of Vertebrate Paleontology, Volume 12, Number 2: 158-167