Thursday, November 4, 2021

[Paleontology • 2021] Issi saaneq • A New Sauropodomorph Dinosaur (Saurischia: Plateosauridae) from the Late Triassic (Norian) of Jameson Land, Central East Greenland


Issi saaneq 
Beccari, Mateus, Wings, Milàn & Clemmensen, 2021
 
 
Abstract
The Late Triassic (Norian) outcrops of the Malmros Klint Formation, Jameson Land (Greenland) have yielded numerous specimens of non-sauropod sauropodomorphs. Relevant fossils were briefly reported in 1994 and were assigned to Plateosaurus trossingensis. However, continuous new findings of early non-sauropod sauropodomorphs around the globe facilitate comparisons and allow us to now revise this material. Here, the non-sauropod sauropodomorph Issi saaneq gen. et sp. nov. is described based on two almost complete and articulated skulls. The two skulls represent a middle-stage juvenile and a late-stage juvenile or subadult. Issi saaneq differs from all other sauropodomorphs by several unique traits: (1) a small foramen at the medial surface of the premaxilla; (2) an anteroposteriorly elongated dorsoposterior process of the squamosal; (3) a relatively high quadrate relative to rostrum height; (4) a well-developed posterodorsal process of the articular. These features cannot be explained by taphonomy, ontogeny, or intraspecific variation. Issi saaneq shows affinities to Brazilian plateosaurids and the European Plateosaurus, being recovered as the sister clade of the latter in our phylogenetic analysis. It is the northernmost record of a Late Triassic sauropodomorph, and a new dinosaur species erected for Greenland. Issi saaneq broadens our knowledge about the evolution of plateosaurid sauropodomorphs.

Keywords: sauropodomorph; Triassic; plateosaurid; dinosaur; Greenland


Systematic Palaeontology 
Dinosauria 
 Saurischia  
Sauropodomorpha 
 Plateosauridae 

Issi saaneq gen. et sp. nov. 

 Etymology: From Kalaallisut, “issi” meaning cold and “saaneq” meaning bone. Pronounced ‘is‐ y sa‐ah‐neq’. In reference to the conditions in which the fossils were recovered. We have selected a name in Inuit language to honor the local culture.

Horizon and Age: NHMD 164741 and NHMD 164758 were collected at Malmros Klint Formation, Flem‐ ing Fjord Group, of mid‐Norian stage of the Late Triassic

Diagnosis: Issi saaneq can be distinguished from other basal sauropodomorphs on the basis of a unique trait combination comprising six phylogenetic synapomorphies (i) and four cra‐ nial autapomorphies (ii). (i) weakly developed narial fossa (character 10, state 0); small subnarial foramen (12, 1); anterior margin of the external naris anterior to the mid‐length of the premaxilla (17, 0); anteroposterior length of the antorbital fossa less than that of the orbit (28, 1); antorbital fossa ending before the ventral process of the lacrimal (41, 1); strongly curved jugal process of the ectopterygoid (86, 1). (ii) the presence of a small fora‐ men at the medial surface of the premaxilla at the base of the lateral process of the pre‐ maxilla; an anteroposteriorly elongated dorsoposterior process of the squamosal; a quad‐ rate relatively tall in comparison to the rostrum height; a well‐developed posterodorsal process of the articular, square‐shaped in lateral view. Issi saaneq possesses features thought to be autapomorphic to other plateosaurids, i.e., five teeth in the premaxilla (as in Plateosaurus), a promaxillary fenestra (as in the Brazilian plateosaurids Macrocollum itaquii and Unaysaurus tolentinoi), a lateral sheet of bone in the lacrimal covering the posterodorsal corner of the antorbital fenestra (as in Plateosaurus trossingensis), and a secondary fossa ventral to the Meckelian groove (as in U. tolentinoi).




Conclusions:
 Two skulls of the new basal sauropodomorph (plateosaurid) dinosaur taxon Issi saaneq gen. nov. sp. nov. from the Late Triassic (Norian) of Jameson Land, central East Greenland are described based on data retrieved with μCT‐scan image segmentation and photogrammetry. Both specimens, NHMD 164741 and NHMD 164758, were recovered from the uppermost Malmros Klint Formation in Greenland, and due to strong morpho‐ logical similarities and no robust distinguishing features between them, are here regarded as a single taxon. The smaller NHMD 164758 represents an early‐stage juvenile, due to the reduced gap between the first premaxillary teeth and the anterior margin of the premaxilla, large orbit, low number of teeth positions in the dentary and an anteriorly deflected basipterygoid process of the basisphenoid. The specimen NHMD 164741 represents either a late‐stage juvenile or a young adult, due to a proportionally shorter orbit than NHMD 164758 and having a possible maximum of 20 dentary teeth positions. Issi saaneq differs from all other basal sauropodomorphs in four observed autapomorphies: (1) the presence of a small foramen at the medial surface of the premaxilla at the base of the lateral process of the premaxilla; (2) an anteroposteriorly elongated dorsoposterior process of the squamosal; (3) a quadrate relatively tall in comparison to the rostrum height; and (4)

Six ambiguous synapomorphies position Issi saaneq as the sister clade to Plateosaurus (Pl. trossingensis and Pl. gracilis). The Brazilian sauropodomorphs were recovered at the base of Plateosauridae and forming the sister clade to the clade containing Issi saaneq and Plateosaurus. Issi saaneq possesses a set of features thought to be exclusive of the Brazilian plateosaurids. Issi saaneq is the first sauropodomorph to reach the Northernmost parts of Laurasia and increases our understanding of the diversity of plateosaurids


 Victor Beccari, Octávio Mateus, Oliver Wings, Jesper Milàn  and Lars B. Clemmensen. 2021. Issi saaneq gen. et sp. nov.—A New Sauropodomorph Dinosaur from the Late Triassic (Norian) of Jameson Land, Central East Greenland. Diversity. 13(11), 561. DOI: 10.3390/d13110561