Monday, February 25, 2013

[Paleontology • 2009] Miragaia longicollum ‘wonderful goddess of the Earth’ • A new long-necked 'sauropod-mimic' stegosaur and the evolution of the plated dinosaurs

Miragaia longicollum
Art: Davide Bonadonna |

Stegosaurian dinosaurs have a quadrupedal stance, short forelimbs, short necks, and are generally considered to be low browsers. A new stegosaur, Miragaia longicollum gen. et sp. nov., from the Late Jurassic of Portugal, has a neck comprising at least 17 cervical vertebrae. This is eight additional cervical vertebrae when compared with the ancestral condition seen in basal ornithischians such as Scutellosaurus. Miragaia has a higher cervical count than most of the iconically long-necked sauropod dinosaurs. Long neck length has been achieved by ‘cervicalization’ of anterior dorsal vertebrae and probable lengthening of centra. All these anatomical features are evolutionarily convergent with those exhibited in the necks of sauropod dinosaurs. Miragaia longicollumis based upon a partial articulated skeleton, and includes the only known cranial remains from any European stegosaur. A well-resolved phylogeny supports a new clade that unites Miragaia and Dacentrurus as the sister group to Stegosaurus; this new topology challenges the common view of Dacentrurus as a basal stegosaur.

Keywords: Stegosaurian dinosaurs; Miragaia longicollum; Dacentrurus; neck elongation; niche partitioning; sexual selection

Miragaia skeleton. 
Image courtesy Octavio Mateus

Etymology: Miragaia, after the locality and geological unit of the same name; longicollum, after the Latin longus(long) and collum (neck), in reference to its long neck. In addition, the stem Mira- can be read as the feminine form of Latin mirus, meaning wonderful, while Gaia is the Greek goddess of the Earth, so the name also means ‘wonderful goddess of the Earth’.

Locality and horizon: Close to Miragaia at the municipality of Lourinhã (Portugal) in the Late Jurassic (Upper Kimmeridgian–Lower Tithonian) Miragaia Unit of the Sobral Formation (Lourinhã Group).

a family of Miragaia feeding
by ~EoFauna on @deviantART 

Mateus, Octávio; Maidment, Susannah C.R.; and Christiansen, Nicolai A. 2009. A new long-necked 'sauropod-mimic' stegosaur and the evolution of the plated dinosaurs. Proceedings of the Royal Society B: Biological Sciences. 276 (1663): 1815–1821. doi:10.1098/rspb.2008.1909