Dacentrurus (meaning "tail full of points"), originally known as Omosaurus, is a genus of stegosaurian dinosaur from the Late Jurassic and perhaps Early Cretaceous (154 - 140 mya) of Europe.

The generic name is derived from Greek ὦμος, omos, "upper arm", in reference to the robust humerus.

Part of the British Museum of Natural History collection was specimen NHMUK 46320, a pair of spike bases found in the Kimmeridge Clay by William Cunnington near the Great Western Railway cutting near Wootton Bassett.

These Owen in 1877 named Omosaurus hastiger, the epithet meaning "spike-bearer" or "lance-wielder", the spikes by him seen as placed on the wrist of the animal.

[5] (That specimen is sometimes mistakenly said to have been found at Fletton, Peterborough, Cambridgeshire, which is where Alfred Nicholson Leeds made most of his finds.)

In 1893, Harry Govier Seeley named Omosaurus phillipsii, based on a left femur of a young individual found at Slingsby, North Yorkshire, specimen YM 498, the epithet honouring the late John Phillips.

[7] "Omosaurus leedsi" is a nomen nudum used by Seeley on a label for CAMSM J.46874, a plate found in Cambridgeshire, the epithet honouring Alfred Nicholson Leeds.

[8] In 1910, Friedrich von Huene named Omosaurus vetustus, based on specimen OUM J.14000, a femur found in the west bank of Cherwell River, the epithet meaning "the ancient one".

[9] In 1911, Franz Nopcsa named Omosaurus lennieri, the epithet honouring Gustave Lennier, based on a partial skeleton in 1899 found in the Kimmeridgian Argiles d'Octeville near Cap de la Hève [fr] in Normandy, France.

[20] In 2021, remains attributed to Dacentrurus sensu lato were reported from the earliest Cretaceous (Berriasian) Angeac-Charente bonebed of France.

[21] In 2024, 11 specimens (including the holotype and referred material of Miragaia longicollum) from France, Portugal, and Spain were assigned to Dacentrurus armatus.

[22] Due to the fact it represented the best known stegosaurian species from Europe, the first known from articulated remains, most stegosaur discoveries in this area were referred to Dacentrurus.

[23] This included finds in Wiltshire and Dorset in southern England (among them a vertebra ascribed to D. armatus in Weymouth[24]), fossils from France and Spain and five more historically recent skeletons from Portugal.

[29] Peter Malcolm Galton in the eighties referred all stegosaur remains from Late Jurassic deposits in western Europe to D.

Most named species, among them Astrodon pusillus from Portugal based on stegosaur fossils, she considered to be nomina dubia.

She considered the specimens from mainland Europe to possibly represent a separate species, but as they were too limited to establish distinctive traits she assigned them to a Dacentrurus sp.

[30] In 2013, Alberto Cobos and Francisco Gascó described stegosaurian vertebral remains, which were found grouped together in the "Barranco Conejero" locality of the Villar del Arzobispo Formation in Riodeva (Teruel, Spain).

The remains were assigned to Dacentrurus armatus and consist of four vertebral centra, specimens MAP-4488-4491, from a single individual, two of which are cervical vertebrae; the third is a dorsal, and the last is a caudal.

[33][34][35] For a stegosaur, the gut was especially broad,[34] and a massive rump is also indicated by exceptionally wide dorsal vertebrae centra.

The rear third of the neck vertebrae and the entire dorsal series are massively built in that the maximal transverse width of their centra exceeds the maximum anterior-posterior length.

[27] If the material is limited to the holotype, as Maidment proposed, only a single autapomorphy, unique derived trait, remains: the straight upper edge of the ischium.

The upper side of the dorsal centrum shows a distinctive depression, an exaggeration of the small dent usually present in this position.

With Stegosaurus and Kentrosaurus, the same is true for the front vertebrae, but in those genera the posterior dorsals have processes pointing much more vertically, up to 35 degrees.

In the first caudal, the transverse processes are vertically deep and oriented horizontally with a conspicuous point on the front upper edge.

[24] The forelimb of Dacentrurus contains a massive humerus, its shaft protruding in an enormous deltopectoral crest, the attachment for a powerful musculature.

[36] The holotype specimen of Dacentrurus armatus contained a small blunt asymmetrical neck or front back plate.

[27] Dacentrurus was the first stegosaur of which good remains had ever been discovered; earlier finds as Paranthodon, Regnosaurus and Craterosaurus were too limited to be directly recognisable as representing a distinctive new group.

[37] In 1969, Ronald Steel agreed, even though Dacentrurus showed basal traits as an apparent lack of dermal plates and a long forelimb.

[24] Earlier often considered to have been a rather basal stegosaurid, Dacentrurus was by more extensive cladistic analyses shown to be relatively derived.

Combined with large deltoid crests on the humerus, they suggest a powerful musculus deltoideus making a strong humeral flexion and abduction possible.