A new phytosaur species (Archosauriformes) from the Upper Triassic of Jameson Land, central East Greenland

Abstract

Herein we describe phytosaurs from thin fluvial overbank sandstones of the Upper Triassic Malmros Klint Formation of the Fleming Fjord Group (central East Greenland). The new sample includes more than 150 disarticulated bones and teeth from small to large specimens belonging to at least four individuals. The fossils mostly consist of teeth and postcranial elements and permit the recognition of a new species of Mystriosuchus, M. alleroq, diagnosed by an Lshaped quadratojugal whose anterior suture trends anterodorsally and a tripartite degree of heterodonty. Humeral diaphyseal histology of one specimen reveals a fairly compact cortex that surrounds a cancellous medullary region followed by a remodeling zone containing scattered secondary osteons. Primary bone tissue is parallel-fibred with a moderate to low vascular density. The cortex is cyclically interrupted by distinct growth marks indicating a seasonal environment. A change in growth rate from moderate to low is documented within the outer cortex, indicating that at least this individual was close to somatic maturity. Mystriosuchus has formerly been known as an exclusively European taxon. The new findings support the European faunal influence in East Greenland during the Late Triassic inferred from other taxa such as temnospondyls and archosaurs. The mid-late Norian age of European Mystriosuchus suggests an additional age constraint for the vertebrate-bearing portion of the Malmros Klint Formation. http://zoobank.org/urn:lsid:zoobank.org:pub:4F91184A-4207-45ED-8214-D503161EA248 SUPPLEMENTAL DATA-Supplemental materials are available for this article for free at www.tandfonline.com/UJVP.

A late-surviving phytosaur from the northern Atlantic rift reveals climate constraints on Triassic reptile biogeography

“…YPM VPPU 7920 is the only substantial reptile body fossil recovered to date from the White Water Member, which consists of rhythmic sediments called sand-bank cycles [ 84 ] that are much more conducive to the preservation of ichnofossils [ 90 ]. Together with phytosaur remains from the Fleming Fjord Group of Greenland [ 57 ], YPM VPPU 7920 is the northernmost occurrence of a phytosaur in the Americas and adjacent islands; it is also the only example of this clade from Canada [ 90 ]. In the Norian-Rhaetian, the locality of origin for YPM VPPU 7920 sat towards the northern terminus of the great central Pangean rift system (Fig.…”

“…Formal description of the partial skull and osteoderm of this species allows for a revised understanding of the phylogenetic and morphological diversity of Late Triassic phytosaurs. The geological setting of Jupijkam paleofluvialis makes it one of the geologically youngest and northernmost occurrences of the clade Phytosauria ([ 90 ]; also see [ 57 ]). The minimum age of Jupijkam paleofluvialis is the Norian-Rhaetian boundary, meaning that this species is substantially younger than the other eastern North American phytosaur known from diagnostic material: Rutiodon carolinensis [ 17 , 90 ] and indeed most phytosaur diversity (Figs.…”

“…Mystriosuchus spp. [ 12 , 57 ] from Europe and Greenland exclusively includes longirostrine species, and some species of Machaeroprosopus also show elongated rostra [ 41 ].…”

“…The recognition of a new species of phytosaur, Jupijkam paleofluvialis , representing the northernmost extent of this clade (e.g., [ 22 , 90 ]:Fig. 29, inset; [ 57 ]) highlights the northernmost extend of Pangea as an unsampled region of phytosaur diversity.…”