Adynomosaurus

Adynomosaurus; Temporal range: Late Cretaceous, Early Maastrichtian PreꞒ Ꞓ O S D C P T J K Pg N
	Restoration
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Order:	†Ornithischia
Clade:	†Ornithopoda
Family:	†Hadrosauridae
Subfamily:	†Lambeosaurinae
Genus:	†Adynomosaurus; Prieto-Márquez et al., 2019
Species:	†A. arcanus
Binomial name
	†Adynomosaurus arcanus; Prieto-Márquez et al., 2019

Adynomosaurus (meaning "weak shoulder lizard", in reference to the unexpanded shoulder blade) is a genus of lambeosaurine hadrosaurid dinosaur from the Late Cretaceous of what is now Catalonia, Spain.^[1]

Discovery and naming[]

In 2019, the type and only species Adynomosaurus arcanus, was named and described by Albert Prieto-Marquez, Víctor Fondevilla, Albert G. Selles, Jonathan R. Wagner and Angel Galobart in paleontological journal Cretaceous Research. The generic name is a composite of the Greek words ‘adýnamos’ (weak), ‘-mos’ (shoulder) and ‘sauros’ (lizard), and is a reference to the characteristically unexpanded morphology of the scapular blade of Adynomosaurus. The specific name arcanus means "secret" or "occult", alluding "to the elusive findings of taxonomically informative skeletal elements of this and other hadrosaurids in the South-Central Pyrenean Basin".^[1] It is based on MCD 7125 (Museu de la Conca Dellà, Isona, Lleida, Spain), a left scapula. This bone was one of a group of 34 bones recovered from the discovery site; the other bones have also been assigned to Adynomosaurus arcanus, and include vertebrae from the neck, sacrum, and tail, a sternal element, part of the pelvis, and parts of the forelimbs and hindlimbs. The discovery site, the Costa de les Solanes locality, is in rocks of the upper lower Maastrichtian Conques Formation.^[1]

Description[]

Scapulae of a standard lambeosaur; compared to this, the scapula of Adynomosaurus is underdeveloped, with reduced length and a small width on the bladed end (to the left)

In many respects, such as the vertebrae, humerus, femur, tibia, and metatarsals, the known anatomy of Adynomosaurus is indistinguishable from all other hadrosaurid dinosaurs.^[1] As a member of the hadrosaur family, it would've been a quadrupedal animal, while bearing the ability to walk upon its hindlegs bipedally. It would've had a long skull, ending in a beak, and a large array of complex teeth; as a lambeosaur, it would have possessed a cranial crest made of the nasal bones, filled with hollow internal passages.^[2] Despite its similarity to other hadrosaurs, some traits distinguish it from its relatives. Compared to other Spanish hadrosaurs, its dental anatomy stands out; the dentary of Koutalisaurus possesses tooth alveoli rotated slightly backwards, whereas in Arenysaurus and Blasisaurus they point upwards. Adynomosaurus possesses teeth intermediate to these conditions, rotated in the front half of the jaw but vertically oriented near the back. The tooth crowns are around three times taller than wide, also differing from the latter pair of genera, which have a more extreme ratio.^[1]

In regards to the anatomy of the postcranium, the supraacetabular crest of the ilium is V-shaped, and is extended very far back, all the way to the connection point with the ischium. Such an extreme extension of the crest is not presented in most lambeosaurines, but can be observed in Parasaurolophus cyrtocristatus as well as the Serrat del Corb hadrosaur. Also shared with these two taxa are features of the iliac process of the ischium; its dorsal and ventral (i.e. top and bottom) margins are nearly parallel and it is stout, with a broad articulate facet. The most distinctive part of its anatomy is its scapula, or shoulder bone, which bears the only traits unique to it among hadrosaurs. Specifically, the scapula is generally underdeveloped; its length, proportionally, seems to be the shortest of all hadrosaurs, though this is unable to be definitively confirmed due to incompleteness of the bone amongst known specimens. More definitively, the scapular blade (the flattened end) is only 75% the width of the proximal end (base) of the bone, unlike in all other lambeosaurines where it is as wide or wider. Likewise, the proximal constriction of the scapula - the middle portion connecting the proximal end to the blade - is very thin, hardly half as deep at the proximal end and around eighty percent the depth of the deepest section of the blade. The deltoid ridge of the bone is heavily reduced. These aspects of scapular anatomy are known to not be variable with age in other hadrosaurs, ruling out that as an expalantion of the condition in Adynomosaurus. The scapulae of Pararhabdodon and the Basturs Poble hadrosaur, from similar times and places, display more conventional anatomy, distinct from that of Adynomosaurus.^[1]

Classification[]

Adynomosaurus is member of the Hadrosauridae that including in clade Lambeosaurinae. It forms a polytomic relationships with Aralosaurus, Canardia, Jaxartosaurus, Tsintaosaurus, Pararhabdodon and other most basal know lambeosaurines.^[1]

References[]

^ ^a ^b ^c ^d ^e ^f ^g Prieto-Márquez, Albert; Fondevilla, Víctor; Sellés, Albert G.; Wagner, Jonathan R.; Galobart, Àngel (2018). "Adynomosaurus arcanus, a new lambeosaurine dinosaur from the Late Cretaceous Ibero-Armorican Island of the European Archipelago". Cretaceous Research. 96: 19–37. doi:10.1016/j.cretres.2018.12.002. S2CID 134582286.
^ Horner, J.A.; Weishampel, D.B.; Forster, C.A. (2004). "Hadrosauridae". In Weishampel, David B.; Osmólska, Halszka; Dodson, Peter (eds.). The Dinosauria (Second ed.). University of California Press. pp. 438–463. ISBN 978-0-520-24209-8.