''Liwia'' is a genus of liwiid

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

. It includes the species ''Liwia plana'' and ''Liwia convexa'', both known from borehole samples several kilometers in depth from the Zawiszyn Formation in Poland, which has also yielded ''

Peytoia infercambriensis ''Peytoia infercambriensis'' is a species of Hurdiidae, hurdiid radiodont in the genus ''Peytoia''. ''P. infercambriensis'' is the geologically oldest known radiodont; its remains date to the Cambrian Stage 3, third age of the Cambrian. The typ ...

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Discovery and naming

The holotype of fossil of ''Liwia'' was found from the Zawiszyn Formation of Poland, and described in 1975. The original generic name ''Livia'' is derived from the name of the Liwiec River, near to where the fossils were found, although as this generic name was already preoccupied, it was changed in 1988 to ''Liwia''. The specific name for ''L. convexa'' derives directly from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word ''convexa'', to mean "rounded", relating to the curved appearance of the

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 ...

; whilst the specific name for ''L. plana'' derives directly from the Latin word ''plana'', to mean "flat", relating the overall flatness of this species.

Description

''Liwia'' is a genus of nektaspida, and the namesake of the

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 (geology), system, the second of six periods of the Paleozoic Era (geology), Era, ...

family, growing to around in length, with the longer, incomplete species being ''L. convexa''; and the shorter, more complete species being ''L. plana''. They have a oval shaped

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

, with four

thoracic The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main ...

segments, and a distinctive spiked pygidium, of which there are six pairs of rear-facing spines, with the three anterior spines being shorter, whilst the three posterior spines are longer.

References

Nektaspida Fossils of Poland {{nektaspida-stub