''Utaurora'' 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 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 ...

opabiniid Opabiniidae is an extinct family of bizarre marine stem- arthropods. Its type and best-known genus is ''Opabinia''. It also contains ''Utaurora''. Opabiniids closely resemble radiodonts, but their frontal appendages were basally fused into a pr ...

, which were bizarre

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...

-arthropods closely related to true

arthropods 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 ...

and

radiodonts Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the last two origi ...

; the type species is ''U. comosa''. The animal's fossils come 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 ...

of Utah. This genus is so far the only other known unquestionable opabiniid, with the other being ''

Opabinia ''Opabinia regalis'' is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte (505 million years ago) of British Columbia. ''Opabinia'' was a soft-bodied animal, measuring up to 7 cm in body length, and it ...

'' itself. There are other animals like ''

Myoscolex ''Myoscolex'' is an early animal species known from the Cambrian Emu Bay Shale in South Australia. It was interpreted as an annelid and some supports that theory, while it was also considered as an arthropod close to '' Opabinia'', through other ...

'' and ''

Mieridduryn ''Mieridduryn'' is a genus of extinct Dinocaridida, dinocaridid arthropod that lived during the Middle Ordovician of what is now the United Kingdom. This animal was described in 2022 based on a singular fossil found in Castle Bank, a Burgess Shal ...

'' that could be opabiniids, but the classification of those two genera is still debated.

History of study

The holotype specimen of ''Utaurora comosa'', KUMIP 314087, was collected from the

Wheeler Formation The Wheeler Shale (named by Charles Walcott) is a Cambrian ( 507 Ma) fossil locality world-famous for prolific agnostid and ''Elrathia kingii'' trilobite remains (even though many areas are barren of fossils) and represents a Konzent ...

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 ...

. It was initially described as a specimen of ''

Anomalocaris ''Anomalocaris'' ("unlike other shrimp", or "abnormal shrimp") is an extinct genus of Radiodonta, radiodont, an Order (biology), order of early-diverging stem-group arthropods. The first fossils of ''Anomalocaris'' were discovered in the ''Ogygop ...

'' in 2008. In 2022, Pates ''et al.'' reinterpreted the specimen as an opabiniid and described it as a new genus and species.

Etymology

''Utaurora'' is a

portmanteau A portmanteau word, or portmanteau (, ) is a blend of wordsUtah 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 ...

, in reference to where the specimen was found, and

Aurora An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of bri ...

, the name of a Roman goddess. The reference to Aurora was chosen as she is a goddess of the dawn who turned her lover into an insect, and ''Utaurora'' is an early species close to the origin of arthropods. The species name is Latin for "hairy" or "leafy", and refers to the appearance of the animal, with a hairy-looking dorsal surface and leaf-like arrangement of caudal blades.

Description

File:20220212 Utaurora comosa.png, Reconstruction File:20220214 Utaurora size.png, Size estimation File:20210807 Utaurora comosa trunk cross section.png, Cross section ''Utaurora'' closely resembles ''

'' and ''

Kylinxia ''Kylinxia'' is a genus of extinct arthropod described in 2020. It was described from six specimens discovered in Yu'anshan Formation (Maotianshan Shales) in southern China. The specimens are assigned to one species ''Kylinxia zhangi.'' Dated to ...

'', a pair of bizarre arthropods from the

Burgess Shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest foss ...

and the

Maotianshan Shales The Maotianshan Shales are a series of Cambrian, Early Cambrian deposits in the Chiungchussu Formation, famous for their ''Lagerstätte, Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized organisms or traces. ...

respectively, with 5 eyes and bizarre frontal appendages. Due to the incomplete discovery, it is uncertain whether ''Utaurora'' have these features as well. ''Utaurora'' differs from ''Opabinia'' in having more extensive setal blades covering its back and promixal region of each lateral flaps (covering only lateral flaps in ''Opabinia''), giving it a hairy appearance, and in having a tail fan composed of at least 7 pairs of caudal blades (3 in ''Opabinia'').

Classification

Based on its similarity to ''Opabinia'', the discoverers of ''Utaurora'' classified it in

Opabiniidae Opabiniidae is an extinct family of bizarre marine stem-arthropods. Its type and best-known genus is '' Opabinia''. It also contains '' Utaurora''. Opabiniids closely resemble radiodonts, but their frontal appendages were basally fused into a ...

. Their phylogenetic analyses generally found support for an opabiniid position. A third possible opabiniid, ''

'' is known from rocks of the

Emu Bay Shale The Emu Bay Shale is a geological formation in Emu Bay, South Australia, containing a major Konservat-Lagerstätte (fossil beds with soft tissue preservation). It is one of two in the world containing Redlichiidan trilobites. The Emu Bay Shale is ...

South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...

. However, because morphological features supporting this classification are controversial, a hypothesis has been put forward suggesting It may also have been an early worm.

References

Works cited

* {{taxonbar, from=Q110877777 Dinocarida Cambrian arthropods Prehistoric arthropod genera Fossil taxa described in 2022 Cambrian genus extinctions