''Aaveqaspis'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of small (about long) marine

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 ...

s of unclear affiliation, that lived during the early

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

period.

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

remains of ''Aaveqaspis'' were collected from the Lower

Sirius Passet Sirius Passet is a Cambrian Lagerstätte in Peary Land, Greenland. The Sirius Passet Lagerstätte was named after the Sirius sledge patrol that operates in North Greenland. It comprises six places in Nansen Land, on the east shore of J.P. Koch F ...

fossil-Lagerstätte of North Greenland. ''Aaveqaspis'' looks like a soft eyeless

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 At ...

with a weakly defined axis, a headshield (or

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...

) with stubby genal spines, 5 thorax segments also ending in stubby genal spines, and a tailshield (

pygidium The pygidium (plural 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 compo ...

) with a pair of massive tusk-like spines, and two smaller spines near the end of the axis. The only species presently known is ''A. inesoni'' (i.e. the genus is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

Etymology

The name of the genus is a compound of the Greenlandic word ' (

walrus The walrus (''Odobenus rosmarus'') is a large pinniped, flippered marine mammal with a discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. The walrus is the only living species in ...

), reflecting the likeness of the tail spines to the tusks of a walrus, and the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

word ' (

shield A shield is a piece of personal armour held in the hand, which may or may not be strapped to the wrist or forearm. Shields are used to intercept specific attacks, whether from close-ranged weaponry or projectiles such as arrows, by means of a ...

). The species was named after Jon R. Ineson to honour him for his studies of the Cambrian of North Greenland.

Description

''Aaveqaspis inesoni'' is almost flat (dorso-ventrally). Its body is narrowly oval in general outline, disregarding the two large spines. The upper non-calcified (or dorsal) side of the body consists of a cephalon, 5 thorax segments, and a pygidium. The axis is slightly raised, but without a discernible furrow defining its outline. The axis is about 20% of the width of the cephalon. The cephalon is half-round, and almost twice as wide as long (along the axis). The (posterolateral) corners of the cephalon are acute, ending in short stout spines. The back margin of the cephalon from the spine to the midline has in the pleural region a forward angle and is first concave, then convex, then concave again, attaining a backward angle when reaching the axis, and finally convex, with a small node or median spine reaching the back margin. This pattern is repeated with all thorax segments. Antennae are not known. Dorsal eyes are absent. The thorax segments are each about along the axis. The tail shield is dominated by a pair of large segmental marginal spines, reminiscent of large (or macropleural) spines in the thorax and of pygidial spines of certain trilobites. The one node it carries is larger and more sharply defined than the nodes on the segments. The frontal border of the tail shield is convex and curves laterally into the large spines which extend postero-laterally, constituting half the total body length. The back margin of the spines is concave and merges into the second pair of short, broad, triangular spines. Body parts on the belly (or ventral) side are not known, including any appendages.

Differences with recognized Liwiidae

'' Buenaspis forteyi'' and '' Liwia convexa'' are similar in general body form to ''A. inesoni''. ''B. forteyi'' is isopygous, with 6 thorax segments instead of the 5 of ''A. inesoni''. ''B. forteyi'' also differs by having a lengthwise mid-ridge on cephalon and pygidium, and the pygidium lacks marginal spines. ''Liwia'' has 4 thorax segments. Although the pygidium of ''Liwia'' has five pairs of modest marginal spines, the 2 pairs of spines and one node in ''A. inesoni'' suggest its pygidium is a composite of only two segments.

Distribution

''A. inesoni'' has been collected from the Lower Cambrian (Atdabanian)

Buen Formation The Buen Formation is a geologic formation and Lagerstätte in Peary Land, North Greenland. The shale preserves fossils dating back to the Early Cambrian period (Atdabanian in the local timescale, about 520 to 513 Ma).order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Nectaspida Nektaspida (also called Naraoiida, Nektaspia and Nectaspida) is an extinct order of non- mineralised artiopodan arthropods. They are known from the mid- Cambrian to the upper Silurian. Originally classified as trilobites, which they superficiall ...

and

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Liwiidae Liwiidae is a family of arthropods in the order Nektaspida. Members are known from the Cambrian and Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 mill ...

References

External links

* {{Taxonbar, from=Q18707590 Prehistoric arthropod genera Cambrian arthropods Cambrian Greenland Fossils of Greenland Sirius Passet fossils Buen Formation Fossil taxa described in 2009 Cambrian genus extinctions