''Thulaspis'' is an extinct genus of

artiopoda Artiopoda is a clade of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomor ...

n arthropod from the

Cambrian Stage 3 Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approxima ...

aged

Sirius Passet Sirius Passet is a Cambrian Lagerstätte in Peary Land, Greenland. The Sirius Passet Lagerstätte was named after the Slædepatruljen Sirius, Sirius sledge patrol that operates in North Greenland. It comprises six places in Nansen Land, on the eas ...

site in Greenland. It is thought to be a close relative of '' Squamacula'', and is possibly one of the most basal members of Artiopoda.

Description

''Thulaspsis'' was relatively large-sized. The largest specimen is about wide and long. The carapace is overall oval-shaped was convex and likely stiff in life, with a raised central axis. The head is broad and bears a pair of antennae, which have at least 20 rectangular segments, and likely two pairs of

biramous The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, ...

(two branched) limbs.The body has 15 thoracic segments, which curve forwards in the first few segments, before becoming straight in the fourth and fifth segments, then increasingly posteriorly curved in subsequent segments. At least the first 11 thoracic segments are associated with pairs of biramous limbs. The biramous limbs have robust endopods (lower, leg-like branches), and flap-shaped

exopod The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip (a ...

s (upper branches). The body terminates with a

pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...

Taxonomy

''Thulaspsis'' has been consistently recovered as more closely related to the genus '' Squamacula'' that to other artiopods. However, their relationships to other artiopodans are unresolved, though analyses often recover the pair as close to the base of the group. Implied weights parsimony phylogeny after Berks et al. 2023.

Ecology

''Thulaspsis'' was likely a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

animal that lived on the seafloor, though the flap-like exopods suggest that it was capable of short bursts of swimming when necessary. It likely consumed soft-bodied prey.

References

{{Taxonbar, from=Q121358688 Artiopoda Prehistoric arthropod genera Fossil taxa described in 2023