Borchgrevinkium

Borchgrevinkium Temporal range: Lochkovian, 416–411.2 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Restoration of B. taimyrensis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Clade:	Euchelicerata
Clade:	Prosomapoda (?)
Genus:	†Borchgrevinkium Novojilov, 1959
Type species
†Borchgrevinkium taimyrensis Novojilov, 1959

Borchgrevinkium is an extinct genus of chelicerate arthropod. A fossil of the single and type species, B. taimyrensis, has been discovered in deposits of the Early Devonian period (Lochkovian epoch) in the Krasnoyarsk Krai, Siberia, Russia. The name of the genus honors Carsten Borchgrevink, an Anglo-Norwegian explorer who participated in many expeditions to Antarctica. Borchgrevinkium represents a poorly known genus whose affinities are uncertain.

It had several unique characteristics that differentiated it from many other arthropods, such as its long parabolic (nearly U-shaped) prosoma (head), its elongated first and second segments and the presence of paired "ridges" in the surface of its third to tenth tergites (dorsal halves of the segments). Furthermore, the opisthosoma (the "trunk") of Borchgrevinkium was triangular, and its telson (the posteriormost division of its body), short and wedge-shaped. It was a small animal, approximately 3 centimetres (1.2 inches) long.

The only known specimen of the genus was collected in 1956 and described in 1959 by the Russian paleontologist Nestor Ivanovich Novojilov. He determined that it was a eurypterid and classified it in the family Mycteroptidae. However, its classification changed repeatedly over the years, being transferred from Eurypterida to Xiphosura and back to Eurypterida some time later. Borchgrevinkium is tentatively considered as a prosomapod, with more fossil material needed to ensure its current classification.