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| Issi saaneq Beccari, Mateus, Wings, Milàn & Clemmensen, 2021 DOI: 10.3390/d13110561 |
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
