Miragaia longicollum

Miragaia is based on holotype ML 433, a nearly complete anterior half of a skeleton with partial skull (the first cranial material for a European stegosaurid). Among the recovered bones were most of the snout, a right postorbital, both angulars of the lower jaws, fifteen neck vertebrae (the first two, which articulated with the skull, were absent), two anterior dorsal vertebrae, twelve ribs, a chevron, the shoulder bones, most of the forelimbs including a possible os carpi intermedium, a right first metacarpal and three first phalanges; and thirteen bony plates plus a spike. The specific name means "long neck" from the Latin longus, "long" and collum, "neck". A partial pelvis (ilium and pubic bone) and two partial dorsal vertebrae from a juvenile individual (specimen ML 433-A) were found at the same location, intermingled with the bones of the holotype, and were also assigned, as a paratype, to M. longicollum. Synonymy with Dacentrurus and Alcovasaurus In 2010, Alberto Cobos and colleagues noted that all the diagnostic characters of Miragaia longicollum are based on skeletal elements that are absent in the Dacentrurus holotype found in England in layers of about the same age, while all traits that can be compared are shared by both genera. Therefore, they proposed that Miragaia is a junior synonym of Dacentrurus, meaning that it is the same dinosaur, because it is not possible to differentiate the two taxa through their holotypes. '', with known material in white|left In 2019, Costa and Mateus argued that Miragaia longicollum is a valid taxon, describing a newly recognised specimen, MG 4863, that had already been excavated in 1959 by Georges Zbyszewski but was only prepared between 2015 and 2017. It consists of a skeleton that also contains tail vertebrae, the most complete dinosaur ever found in Portugal. They also renamed Alcovasaurus, which was discovered in 1908, into a possible second species: Miragaia longispinus. However, Sánchez-Fenollosa et al. (2024) supported the synonymy of Miragaia and Dacentrurus based on a new specimen of the latter from the Villar del Arzobispo Formation, and suggested that Alcovasaurus is a separate genus. In their re-description of the specimen MG 4863, Costa et al. (2025) argued that the two taxa are not synonymous based on comparison with the Dacentrurus holotype and that Alcovasaurus should be included as a second species of Miragaia. ==Description==

Size and diagnosis Miragaia was long yet relatively lightweight in comparison to other stegosaurs, reaching in length and in body mass. Histology shows that the holotype specimen reached sexual maturity at 14 to 15 years old, and skeletal maturity (full size) between 21 and 25 years old. The describers established six distinguishing traits. At their very midline, the praemaxillae meet in a small sharp point, set within a larger notch in the snout tip as a whole. The front lower side edge of the praemaxilla protrudes to below. At least seventeen cervical vertebrae are present. The neural spines of the middle cervical vertebrae have a notch at their lower front edge with immediately above it a process directed to the front. The vertebrae of the middle neck, rear neck and front back possess neural spines that have a transversely expanded upper end. On the neck two rows of triangular bony plates are present that have a lightly convex outer side and a notch at the upper front edge creating a hook. ==Classification==

In 2009, Mateus and colleagues performed a phylogenetic analysis and found Miragaia to group with Dacentrurus in a clade Dacentrurinae of the family Stegosauridae, newly named for the occasion, the sister group to Stegosaurus (the latter genus was in the cladistic analysis considered to include Hesperosaurus and Wuerhosaurus). In 2017, Raven and Maidment published a new phylogenetic analysis, including almost every known stegosaurian genus: The authors stressed that the only synapomorphy, shared derived trait, supporting the Dacentrurus-Stegosaurus clade was the possession of the long cervical postzygapophyses, and that these are in fact unknown for Dacentrurus itself, so that its close position to Stegosaurus was merely based on the new data provided by the description of Miragaia. ==See also==