''Kiisortoqia soperi'' is an extinct species of

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

from the Early Cambrian Sirius Passet

Lagerstätte A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These for ...

in Greenland. While it had a superficially

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

-like bodyform, it also possessed large frontal appendages similar to those of radiodonts.

Description

The body of ''K. soperi'' consisted of a simple head shield, 16 trunk segments ( tergites) and a tail plate. In outward appearance the body is almost elliptical, about twice as long as wide, with the widest point in the front third of the body at the 3rd to 5th tergite. The head plate was simple, convex in shape, wider than long, and represented about 20% of the total body length. The tergites were short, about five times as wide as long, and the rear edge of each tergite overlapped the following by about a fifth of its length. The tergites 1–5 all had about the same width, the following tergites becoming narrower towards the posterior end of the animal. In the middle of the tergites an axis can be clearly seen, which constituted about half the width of a tergite and gave it a three-lobed shape. At the lateral ends of each tergite existed spines which increased in length towards the tail. The tiny tail was semi-circular, about half as long as wide. The front half to two-thirds of the tail shield also has a three-lobed shape. The first segment bore a ventral pair of large appeandages, which are about half to two-thirds as long as the body. They consisted of a cylindrical stem and about 15 segments. The segments had a flat outer side and two widely spaced spines. The other limbs – three pairs in the head region shield and 16 on the body segments – composed of two branches. The basipod was long, trapezoid-shaped and had two rows with different numbers of spines. The exopods were paddle-like lobes, which were fringed with bristles. The length was little more than two thirds of the length of the endopodite. Its gut is occasionally preserved in three dimensions, perhaps in phosphate.

Ecology

It is believed that ''Kiisortoqia'' was a

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

y swimmer. The large paddle-like exopods were probably suitable for swimming. With its robust appendages, ''K. soperi'' could capture prey, probably using its prickly basipods to bring them to its mouth.

Etymology

The name of the genus is derived from the Greenlandic word ', meaning "predator" or "hunter". The specific epithet is in honor of Norman John (Jack) Soper who, together with A. K. Higgins, discovered the Sirius Passet fauna and collected the first fossils from the locality.

Distribution

More than 170 specimens of the species were recovered in the course of several expeditions between 1985 and 2006 from the Lower Cambrian Sirius Passet Konservat-Lagerstätte, in

Peary Land Peary Land is a peninsula in northern Greenland, extending into the Arctic Ocean. It reaches from Victoria Fjord in the west to Independence Fjord in the south and southeast, and to the Arctic Ocean in the north, with Cape Morris Jesup, the nor ...

, northern Greenland. The specimens are usually more or less completely preserved: disarticulated fossils were not discovered.

Systematic position

''Kiisortoqia soperi'' possesses three crown-arthropod homologies: a head shield with three pairs of limbs, plus the appendages; postappendage biramous limbs; and flap-like exopods fringed with setae. An exact position within the arthropods, however, cannot be determined, due to the possible lack of eyes and the ambiguous shape of the tail plate. A possible

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

of the appendages with the chelicerates is purely speculative. A later

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

analysis resolved ''Kiisortoqia'' as

sister A sister is a woman or a girl who shares one or more parents with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to refer to ...

to the rest of crown-group arthropods studied. A later study also suggested it was closely related to the morphologically similar '' Bushizheia'' known from the

Chengjiang Biota The Maotianshan Shales are a series of Early Cambrian deposits in the Chiungchussu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales ...

of China.

References

{{Taxonbar, from1=Q19842438, from2=Q1575382 Cambrian arthropods Prehistoric arthropod genera Fossils of Greenland Cambrian genus extinctions