Sunday 20 December 2020

AMMONOIDS, BIVALVES AND POLAR BEARS OF SVALBARD

 This marvellous block is filled with Aristoptychites (syn=Arctoptychites) euglyphus (Mojsisovics, 1886) and Daonella sp., oyster-like saltwater clams or bivalves from the Middle Triassic (Ladinian) outcrops in the Botneheia Formation of Spitzbergen, in Edgeøya and Barentsøya, eastern Svalbard, Norway. 

Daonella and Monotis are important species for our understanding of biostratigraphy in the Triassic and are useful as an index fossil. Daonellids preferred soft, soupy substrates and we tend to find them in massive shell beds.

Svalbard is a Norwegian archipelago between mainland Norway and the North Pole. One of the world’s northernmost inhabited areas, it's known for its rugged, remote terrain of glaciers and frozen tundra sheltering polar bears, reindeer and Arctic fox. The Northern Lights are visible during winter, and summer brings the “midnight sun”—sunlight 24 hours a day.

The Botneheia Formation is made up of dark grey, laminated shales coarsening upwards to laminated siltstones and sandstones. South of the type area, the formation shows several (up to four) coarsening-upward units. 

The formation is named for Botneheia Mountain, a mountain in Nordenskiöld Land at Spitsbergen, Svalbard. It has a height of 522 m.a.s.l., and is located south of Sassenfjorden, east of the valley of De Geerdalen. 

Polar Bears, Ursus maritimus
As well as lovely ammonoids and bivalves, we've found ichthyosaur remains here. We had been expecting too, but it was not until the early 2000s that the first bones were found.

Two specimens have of ichthyosaur have been recovered. They comprise part of the trunk and the caudal vertebral column respectively. 

Some features, such as the very high and narrow caudal and posterior thoracic neural spines, the relatively elongate posterior thoracic vertebrae and the long and slender haemapophyses indicate that they probably represent a member of the family Toretocnemidae. 

Numerous ichthyosaur finds are known from the underlying Lower Triassic Vikinghøgda Formation and the overlying Middle to Upper Triassic Tschermakfjellet Formation, the new specimens help to close a huge gap in the fossil record of the Triassic ichthyosaurs from Svalbard.

There is a resident research group working on the Triassic ichthyosaur fauna, the Spitsbergen Mesozoic Research Group. Lucky for them, they often find the fossil remains fully articulated — the bones having retained their spacial relationship to one another. Most of their finds are of the tail sections of primitive Triassic ichthyosaurs. In later ichthyosaurs, the tail vertebrae bend steeply downwards and have more of a fish-like look. In these primitive ancestors, the tail looks more eel-like — bending slightly so that the spines on the vertebrae form more of the tail.

Maisch, Michael W. and Blomeier, Dierk published on these finds back in 2009: Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen Band 254 Heft 3 (2009), p. 379 - 384. Nov 1, 2009

The lovely block you see here is in the collections of the deeply awesome John Fam. The image of the Polar Bears, Ursus maritimus, is courtesy of the Fossil Huntress.