''Pahvantia'' 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

hurdiid Hurdiidae is an extinct cosmopolitan family of radiodonts, a group of stem-group arthropods, which lived during the Paleozoic Era. It is the most long-lived radiodont clade, lasting from the Cambrian period to the Devonian period. Description ...

radiodont from the

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 ...

. It is known by a single species, ''Pahvantia hastata'', described from Wheeler Shale and

Marjum Formation The Marjum Formation is a Cambrian geological formation that overlies the Wheeler Shale in the House Range, Utah. It is known for its occasional preservation of soft-bodied tissue, and is slightly younger than the Burgess Shale The Burgess S ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

. Although it was once considered as

filter feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

using large number of putative setae, this structures are later considered as misidentification of trunk materials.

Description

File:20210516 Radiodonta head sclerites Pahvantia hastata.png, Head sclerites File:20210909 Radiodonta frontal appendage Pahvantia hastata.png, Frontal appendage File:20210218 Pahvantia size.png, Size estimation File:Rsos210664f06 (cropped).jpg, KUMIP 314089 File:Pahvantia KUMIP 314089 with counterpart.png, KUMIP 314089 compared to counterpart, showing supposed podomeres Genus name ''Pahvantia'' is named after

Pahvant Pahvant (''Pavant, Parant, Pahva-nits'') was a band of Ute people that lived in present-day Utah. Called the "Water People", they fished and hunted waterfowl. They were also farmers and hunter-gatherers. In the 18th century they were known to be f ...

in western Utah. It was originally described as possible arthropod with unknown affinity. One specimen is described as a specimen of ''Proboscicaris agnosta'', which is originally interpreted as bivalved arthropod, and now considered as head sclerites of '' Hurdia''. ''Pahvantia'' is a relatively small radiodont with estimated length up to . Similar to most of other hurdiid, ''Pahvantia'' had large dorsal head sclerite (H-element), and it was more than twice longer than wide. Based on frontal appendage, its morphology is most close to that of ''Hurdia'', although shape of sclerites are enough different to consider ''Pahvantia'' as distinct genus.

Interpretation of frontal appendage

Pahvantia fossil interpretation difference

Lerosey-Aubril and Pates (2018) considered fossil specimen KUMIP 314819 as frontal appendage with a multitude of long hair-like structures tentatively interpreted as

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 ...

hereafter. It was interpreted that frontal appendage had two different types of endites, two proximal short ones with robust plate-like structures with different widths, and five, apparently unpaired ones that are two to three times wider and around three times longer, with anterior margins that fringed by numerous setae. However, Moysiuk and Caron (2019) questioned this interpretation, with reasons such as unnatural fossil preservation against flexibility of structures, no differentiation between podomeres and endites that Lerosey-Aubril and Pates (2018) interpreted, too large frontal appendage size compared to other hurdiids. It was considered that whole morphology of "frontal appendage" shows several bands of lamellae and possibly represent disarticulated endites. Due to preservation status, researchers considered that morphology of frontal appendage is uncertain. In 2021, Moysiuk and Caron reinterpreted morphology of ''Pahvantia hastata'' with description of ''

Titanokorys ''Titanokorys'' is a genus of extinct hurdiid radiodont (a grouping of primitive stem arthropods which lived during the early Paleozoic) that existed during the mid Cambrian. It is the largest member of its family from the Cambrian, with a b ...

''. Researchers compared the part and counterpart of specimen KUMIP 314819, and they found actual part shows ''Hurdia''-like frontal appendage. "two proximal short endites with different widths" Lerosey-Aubril and Pates (2018) interpreted actually shows one endite and three overlapped endites. Other "five endites with numerous setae" are more comparable to gill blades (setal blades) on trunk segments.

Palaeoecology

''Pahvantia'' was originally interpreted as one of the examples of suspension feeding radiodont alongside '' Aegirocassis'' and ''

Tamisiocaris ''Tamisiocaris'' (from Latin ''tamisium'', sieve, and Greek ''karis'', crab, shrimp) is a radiodont genus initially only known from frontal appendages from the Buen Formation in Sirius Passet. Further specimens revealed that the frontal appenda ...

'', used numerous setae on frontal appendage to capture microscopic food particles suspended in the water column. However, after morphology of frontal appendage is reinterpreted, it is estimated that ''Pahvantia'' probably had nektobenthic lifestyle, captured larger prey living along or in the sediment, according to morphology of frontal appendage similar to ''Hurdia''.

References

{{Taxonbar, from=Q113550283 Cambrian arthropods Anomalocaridids Fossil taxa described in 1981 Cambrian genus extinctions