# Utahnax

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Extinct genus of gilled lobopodian

Utahnax Temporal range: Drumian PreꞒ Ꞓ O S D C P T J K Pg N Fossil of Utahnax A reconstruction of the known parts of Utahnax Scientific classification Kingdom: Animalia Stem group: Arthropoda Class: †Dinocaridida Family: †Kerygmachelidae Genus: †Utahnax Lerosey-Aubril and Ortega-Hernández, 2022 Species: †U. vannieri Binomial name †Utahnax vannieri Lerosey-Aubril and Ortega-Hernández, 2022

***Utahnax*** is a genus of [kerygmachelid](/source/Kerygmachelidae)[1] lobopodian from the [Drumian](/source/Drumian) of Utah, containing one species, ***Utahnax vannieri***, either from the [Marjum](/source/Marjum_Formation) or [Wheeler](/source/Wheeler_Shale) formation.

## Description

*Utahnax'*s preserved section is roughly 6 cm (2.4 in) long, with at least eight pairs of ventral flaps similar to those found on *[Kerygmachela](/source/Kerygmachela)*. Unusually, it does not appear to have had legs, suggesting the ventral flaps are broadened lobopods similar to the ventral flaps on radiodonts, and casting doubt on whether *Kerygmachela* had legs or whether reported "lobopods" are actually muscles of the flaps.[2] In addition, it may have borne complex digestive glands similar to those of [radiodonts](/source/Radiodonta).

## Ecology

As *Utahnax* nests firmly within the predatory clade of "gilled lobopodians", it can be assumed that it was also predatory. Its lack of lobopods also suggests it was primarily if not wholly pelagic, occupying a similar niche to radiodonts. This may explain the paucity of gilled lobopodians in the fossil record, as they may have competed with radiodonts in the pelagic predatory niches.[2]

## Etymology

The genus name *Utahnax* is derived from Utah, where it was found, and the Greek word *anax*, meaning "king" or "ruler". The species name *vannieri* honours Jean Vannier for their extensive work on fossil ecdysozoans.[2]

## Distribution

*Utahnax* is known from only a singular part and counterpart. As the fossil was not precisely labelled, it is unknown where exactly it was found in Utah, although an origin in the [Weeks Formation](/source/Weeks_Formation) or most of the Wheeler Shale can be ruled out due to differing fossil preservation methods.[2]

## References

1. **[^](#cite_ref-1)** McCall, C. R. A. (2023). "A large pelagic lobopodian from the Cambrian Pioche Shale of Nevada". *Journal of Paleontology*. **97** (5): 1–16. [Bibcode](/source/Bibcode_(identifier)):[2023JPal...97.1009M](https://ui.adsabs.harvard.edu/abs/2023JPal...97.1009M). [doi](/source/Doi_(identifier)):[10.1017/jpa.2023.63](https://doi.org/10.1017%2Fjpa.2023.63).

1. ^ [***a***](#cite_ref-LeroseyAubril_2-0) [***b***](#cite_ref-LeroseyAubril_2-1) [***c***](#cite_ref-LeroseyAubril_2-2) [***d***](#cite_ref-LeroseyAubril_2-3) Lerosey-Aubril, R.; Ortega-Hernández, J. (2022). "A new lobopodian from the middle Cambrian of Utah: did swimming body flaps convergently evolve in stem-group arthropods?". *Papers in Palaeontology*. **8** (3) e1450. [Bibcode](/source/Bibcode_(identifier)):[2022PPal....8E1450L](https://ui.adsabs.harvard.edu/abs/2022PPal....8E1450L). [doi](/source/Doi_(identifier)):[10.1002/spp2.1450](https://doi.org/10.1002%2Fspp2.1450). [S2CID](/source/S2CID_(identifier)) [250076505](https://api.semanticscholar.org/CorpusID:250076505).

v t e Lobopodians Kingdom: Animalia Clade: Bilateria Superphylum: Ecdysozoa Clade: Panarthropoda Controversial taxa Diania Fusuconcharium Lenisambulatrix Microdictyon Onychodictyon Paucipodia Quadratapora Xenusion Hallucigeniidae Carbotubulus Cardiodictyon Hallucigenia Rhombocorniculum Thanahita Luolishaniidae Acinocricus Collinsium Collinsovermis Entothyreos Facivermis Luolishania Miraluolishania Ovatiovermis Onychophoran-related taxa Antennacanthopodia Helenodora Orstenotubulus Tritonychus Arthropod-related taxa Hadranax Jianshanopodia Megadictyon Siberion Aysheaiidae Aysheaia Palaeocampa "Gilled lobopodians" Kerygmachelidae Omnidens Pambdelurion Opabiniidae (Also see Dinocaridida) Related categories Category:Lobopodia

v t e Dinocaridida Kingdom: Animalia Clade: Bilateria Superphylum: Ecdysozoa Clade: Panarthropoda Phylum: Stem-group Arthropoda Dinocaridida Caryosyntrips ?Parvibellus Omnidens Pambdelurion Youti Also see Lobopodia Kerygmachelidae Kerygmachela Utahnax Mobulavermis Opabiniidae Opabinia Utaurora Mieridduryn Radiodonta see Radiodonta Category

Taxon identifiers Utahnax Wikidata: Q125019781 GBIF: 12174041 IRMNG: 11924499

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Adapted from the Wikipedia article [Utahnax](https://en.wikipedia.org/wiki/Utahnax) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Utahnax?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.