Darwinsaurus

Darwinsaurus (meaning "Darwin's lizard") is a genus of herbivorous styracosternan ornithopod dinosaur.

In the early nineteenth century dinosaur remains were discovered in the Shornden Quarry at Shornden near Hastings in East Sussex. These were first reported by Richard Owen in 1842. In 1889 they were referred to Iguanodon fittoni by Richard Lydekker. They were then assigned to Hypselospinus fittoni by David Bruce Norman in 2010.

In 2012 Gregory S. Paul named them as a separate genus and species. The type species is Darwinsaurus evolutionis. The generic name honours Charles Darwin for his theory of evolution. The specific name refers to evolution in general and specifically to the strong evolutionary radiation that iguanodonts, according to Paul, are a prime example of. The holotype, as indicated by Paul, is an associated skeleton that includes material catalogued under the numbers NHMUK R1831, R1833, and R1835 (Paul mistakenly included NHMUK R1836 in the genus, unaware that it came from the younger Wessex Formation). Included by Lydekker and Norman was also specimen NHMUK R1832, lower arm elements.

Paul in 2012 provided a short diagnosis of Darwinsaurus. The dentary, the front bone of the lower jaw, is straight. An elongated diastema is present between the beak and the row of teeth. The dentary is shallow below the diastema and deeper below the teeth. The foremost dentary teeth are smaller. The arm is very robust. The olecranon of the ulna is well-developed. Some carpalia are very large. The metacarpals are rather elongated. The thumb spike, the claw of the first finger, is massive.

Paul and Norman are in disagreement about the form of the diastema. According to Paul, an illustration in Lydekker (1889) shows that the fossil originally possessed a long and low gap between the tooth battery and the beak; subsequent damage would have removed three or four very small teeth in front of the main row. Norman, however, disputes this and thinks damage has considerably lowered the jaw, the front teeth originally having been large, resulting in a narrow diastema.

Paul considered Darwinsaurus a basal member of the Iguanodontia.

Norman (2013) considered Paul's description of Darwinsaurus to be inadequate, treating D. evolutionis as a junior synonym of Hypselospinus fittoni, and noting that NHMUK 1836, an associated partial skeleton from the late Barremian of the Isle of Wight, can referred to the species Mantellisaurus atherfieldensis. In a recent SVP abstract, Karen Poole considered Darwinsaurus a possible junior synonym of Huxleysaurus based on unpublished cladistic results.