''Pauloterminus'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of bivalved arthropod known from

Early Cambrian The Cambrian Period ( ; sometimes symbolized 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 years ago ( ...

(about 520 to 516

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

)

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 ...

locality of northern Greenland. It is tentatively classified under the family

Waptiidae Hymenocarina is an order of extinct arthropods known from the Cambrian. They possess bivalved carapaces, typically with exposed posteriors. Members of the group are morphologically diverse and had a variety of ecologies, including as filter feede ...

. The genus only has a single species ''P. spinodorsalis''. It was first described by the paleontologist Rod S. Taylor in 2002. Its generic name is derived from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

'' paulus'' ("small") and ''

terminus Terminus may refer to: * Bus terminus, a bus station serving as an end destination * Terminal train station or terminus, a railway station serving as an end destination Geography *Terminus, the unofficial original name of Atlanta, Georgia, United ...

'' ("end"). The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

is from Latin ''spina'' ("thorn") and ''dorsalis'' ("of the back").

Description

The ovoid-shaped bivalved carapace encloses the head and the anterior section of the trunk. The carapace is slightly less than twice as long as it is tall, and becomes wider posteriorly. The largest known carapace is long and wide, while in the smallest known specimens it is less than a centimere in length. The head is poorly known, though it is suggested that they lacked eyes. One specimen has partially preserved pair of segmented antennae, which have at least 4 segments, which decrease in length towards the end of the antenna. The thorax was likely tube shaped, and had six segments, each associated with a pair of

biramous limb 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, plur ...

s, which decrease in size posteriorly. The limb

endopod 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, plur ...

s are thin and annulate, and approximately 1mm in width, while the

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, plur ...

s were lobe-shaped and bore

setae In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. Th ...

. The abdomen was limbless and had five segments, and terminated in a pair of segmented caudal flukes.

Taxonomy

In its original description, ''Pauloterminus'' was noted to be morphologically similar to ''

Waptia ''Waptia fieldensis'' is an extinct species of arthropod from the Middle Cambrian Burgess Shale ''Lagerstätte'' of Canada. It grew to a length of , and had a large bivalved carapace and a segmented body terminating into a pair of tail flaps. I ...

'' and ''

Chuandianella ''Chuandianella ovata'' is an extinct bivalved arthropod that lived during Cambrian Stage 3 of the Early Cambrian (about 520 to 516 million years ago). It is the only species classified under the genus ''Chuandianella''. Its fossils were recover ...

,'' both historically considered " waptiids", but it is unclear whether the group is monophyletic.

References

Prehistoric arthropod genera Fossils of Greenland {{paleo-arthropod-stub Hymenocarina