Omnidens

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Omnidens
Temporal range: Cambrian Stage 3
20210225 Omnidens size.png
Size estimation of Omnidens as a gilled lobopodian, with the only evident region (mouthparts) highlighted in dark grey.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
(unranked): Panarthropoda
Genus: Omnidens
Hou, Bergström, and Yang, 2006
Type species
Omnidens amplus
Hou, Bergström, and Yang, 2006

Omnidens amplus, meaning "large all-tooth", is an extinct species of large Cambrian animal known only from a series of large mouth apparatus, originally mistaken as the mouthparts of anomalocaridids. [1] When first named, it was interpreted as a giant priapulid, [1] but is now considered a panarthropod. [2] Its mouth apparatus closely resembles that of the smaller gilled lobopodian Pambdelurion , indicating it is likely to have been a close relative of that species, with which it may be synonymous. [2] With a maximum estimated body length of 1.5 metres (4.9 ft), Omnidens is suggested to have been the largest known free-living Cambrian organism. [2] Omnidens fossils are found in the Maotianshan Shales. [1]

Contents

History

The first-described specimen of Omnidens was first described in 1994. At the time, it was interpreted as the oral cone of an anomalocaridid, and it was used as evidence to claim that anomalocaridids could reach a maximum body length of up to 2 meters (6.6 ft). [3] Omnidens fossils were later described as specimens of Peytoia and Parapeytoia until finally being recognized as a distinct species in 2006 and named Omnidens amplus. [1] At this time, it was reinterpreted as a gigantic priapulid, at least 1 metre (3.3 ft) long, far exceeding most known priapulids in size. Omnidens was later identified as a close relative of the gilled lobopodian Pambdelurion. [2]

Description

Reconstruction of Pambdelurion, a smaller relative known from much more complete remains. 20191112 Pambdelurion whittingtoni.png
Reconstruction of Pambdelurion , a smaller relative known from much more complete remains.
Reconstruction of Megadictyon, which may have been the bearer of the Omnidens mouth apparatus. 20191118 Megadictyon cf. haikouensis.png
Reconstruction of Megadictyon , which may have been the bearer of the Omnidens mouth apparatus.

Omnidens is only known from mouthparts. The preserved mouthparts would have formed a short muscular, potentially protrusible pharynx surrounded by circles of spiny sclerites, which were reminiscent of the scalids of priapulids, kinorhynchs, and loriciferans. The inside of the pharynx was also lined with several rows of pharyngeal sclerites. Based on the large size of its preserved mouthparts, Omnidens is estimated to have reached a length of up to 1.5 metres (4.9 ft). [2] Its overall appearance was likely similar to that of its close relative Pambdelurion. Spines preserved near the mouthparts of Omnidens may belong to frontal appendages like those of other stem-group arthropods.

Classification

Onychophora

Tardigrada

Siberion

Jianshanopodia

Megadictyon

Kerygmachela

Pambdelurion

Opabinia

Radiodonta

Euarthropoda

Phylogenetic relationships of Panarthropoda, [4] with possible bearers of the Omnidens mouthparts bolded

Omnidens is classified as a stem-group arthropod. [2] It is so similar to Pambdelurion that the two taxa may be synonymous, but no Pambdelurion specimens are known from the same strata as Omnidens. It is possible that Omnidens mouthparts belong to the contemporary lobopodians Megadictyon or Jianshanopodia .

Distribution

Omnidens is a member of the Chengjiang Biota of China, [1] which dates to approximately 520 Ma, during Cambrian Stage 3. [5] Omnidens-like mouthparts have also been found in the slightly younger Xiaoshiba Lagerstätte. [6] Pambdelurion, which has mouthparts nearly identical to those of Omnidens, is from the Sirius Passet Lagerstätte of Greenland. [2]

Related Research Articles

<span class="mw-page-title-main">Lobopodia</span> Group of extinct worm-like animals with legs

Lobopodians are members of the informal group Lobopodia, or the formally erected phylum Lobopoda Cavalier-Smith (1998). They are panarthropods with stubby legs called lobopods, a term which may also be used as a common name of this group as well. While the definition of lobopodians may differ between literatures, it usually refers to a group of soft-bodied, marine worm-like fossil panarthropods such as Aysheaia and Hallucigenia.

<i>Hallucigenia</i> Genus of Cambrian animals

Hallucigenia is a genus of lobopodian, known from Cambrian aged fossils in Burgess Shale-type deposits in Canada and China, and from isolated spines around the world. The generic name reflects the type species' unusual appearance and eccentric history of study; when it was erected as a genus, H. sparsa was reconstructed as an enigmatic animal upside down and back to front. Lobopodians are a grade of Paleozoic panarthropods from which the velvet worms, water bears, and arthropods arose.

<i>Opabinia</i> Extinct stem-arthropod species found in Cambrian fossil deposits

Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte of British Columbia. Opabinia was a soft-bodied animal, measuring up to 7 cm in body length, and its segmented trunk had flaps along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a clawed proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed, where they constitute less than 0.1% of the community.

<span class="mw-page-title-main">Dinocaridida</span> Extinct class of basal arthropods

Dinocaridida is a proposed fossil taxon of basal arthropods that flourished in the Cambrian period with occasional Ordovician and Devonian records. Characterized by a pair of frontal appendages and series of body flaps, the name of Dinocaridids refers to the suggested role of some of these members as the largest marine predators of their time. Dinocaridids are occasionally referred to as the 'AOPK group' by some literatures, as the group compose of Radiodonta, Opabiniidae, and the "gilled lobopodians" Pambdelurion and Kerygmachelidae. It is most likely paraphyletic, with Kerygmachelidae and Pambdelurion more basal than the clade compose of Opabiniidae, Radiodonta and other arthropods.

<i>Anomalocaris</i> Extinct genus of cambrian radiodont

Anomalocaris is an extinct genus of radiodont, an order of early-diverging stem-group arthropods.

<i>Vetulicola</i> Fossil genus of marine animal

Vetulicola is an extinct genus of marine animal discovered from the Cambrian of China. It is the eponymous member of the enigmatic phylum Vetulicolia, which is of uncertain affinities but may belong to the deuterostomes. The name was derived from Vetulicola cuneata, the first species described by Hou Xian-guang in 1987 from the Lower Cambrian Chiungchussu Formation in Chengjiang, China.

<span class="mw-page-title-main">Anomalocarididae</span> Clade of extinct arthropods

Anomalocarididae is an extinct family of Cambrian radiodonts, a group of stem-group arthropods.

<i>Pambdelurion</i> Extinct genus of Arthropod

Pambdelurion is an extinct genus of panarthropod from the Cambrian aged Sirius Passet site in northern Greenland. Like the morphologically similar Kerygmachela from the same locality, Pambdelurion is thought to be closely related to arthropods, combining characteristics of "lobopodians" with those of primitive arthropods.

<i>Parapeytoia</i> Extinct genus of arthropods

Parapeytoia is a genus of Cambrian arthropod. The type and only described species is Parapeytoia yunnanensis, lived over 518 million years ago in the Maotianshan shales of Yunnan, China. Unidentified fossils from the same genus also had been discovered from the nearby Wulongqing Formation.

<i>Facivermis</i> Extinct genus of panarthropods

Facivermis is a genus of sessile lobopodian from the Lower Cambrian Maotianshan shales of China

<i>Jianshanopodia</i> Extinct genus of Cambrian lobopodian

Jianshanopodia is a monotypic genus of Cambrian lobopodian, discovered from Maotianshan Shales of Yunnan, China.

<span class="mw-page-title-main">Radiodonta</span> Extinct order of basal arthropods

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 originally refer to the family Anomalocarididae, which previously included all species of this order but is now restricted to only a few species. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and used for a variety of functions. Radiodonts included the earliest large predators known, but they also included sediment sifters and filter feeders. Some of the most famous species of radiodonts are the Cambrian taxa Anomalocaris canadensis, Hurdia victoria, Peytoia nathorsti, Titanokorys gainessii, Cambroraster falcatus and Amplectobelua symbrachiata, the Ordovician Aegirocassis benmoulai and the Devonian Schinderhannes bartelsi.

<i>Diania</i> Extinct genus of Cambrian animals

Diania is an extinct genus of lobopodian panarthropod found in the Lower Cambrian Maotianshan shale of China, represented by a single species - D. cactiformis. Known during its investigation by the nickname "walking cactus", this organism belongs to a group known as the armoured lobopodians, and has a simple worm-like body with robust, spiny legs. Initially, the legs were thought to have a jointed exoskeleton and Diania was suggested to be evolutionarily close to early arthropods, but many later studies have rejected this interpretation.

<span class="mw-page-title-main">Luolishaniidae</span> Extinct family of worm-like animals

The Luolishaniidae or Luolishaniida are a group of Cambrian and Ordovician lobopodians with anterior 5 or 6 pairs of setiferous lobopods. Most luolishaniids also have posterior lobopods each with a hooked claws, and thorn-shaped sclerites arranged as three or more per trunk segment. The type genus is based on Luolishania longicruris Hou and Chen, 1989, from the Chengjiang Lagerstatte, South China. They are presumed to have been benthic suspension or filter feeders.

<i>Cardiodictyon</i> Extinct genus of lobopodians

Cardiodictyon is a genus of lobopodian known from 518 millions years old Chengjiang Lagerstätte. 525 millions years old partial fossil is also reported. It has ~25 pairs of legs, each associated with a pair of dorsal plates.

<span class="mw-page-title-main">Amplectobeluidae</span> Extinct clade of Cambrian organisms

Amplectobeluidae is a clade of Cambrian radiodonts. It currently includes five definitive genera, Amplectobelua, Lyrarapax, Ramskoeldia, Guanshancaris and a currently unnamed genus from the lower Cambrian aged Sirius Passet site in Greenland. There is also a potential fifth genus, Houcaris, but that genus has become problematic in terms of its taxonomic placement.

<i>Acinocricus</i> Extinct genus of lobopodians

Acinocricus is a genus of extinct panarthropod belonging to the group Lobopodia and known from the middle Cambrian Spence Shale of Utah, United States. As a monotypic genus, it has one species Acinocricus stichus. The only lobopodian discovered from the Spence Shale, it was described by Simon Conway Morris and Richard A. Robison in 1988. Owing to the original fragmentary fossils discovered since 1982, it was initially classified as an alga, but later realised to be an animal belonging to Cambrian fauna.

Luolishania is an extinct genus of lobopodian panarthropod and known from the Lower Cambrian Chiungchussu Formation of the Chengjiang County, Yunnan Province, China. A monotypic genus, it contains one species Luolishania longicruris. It was discovered and described by Hou Xian-Guang and Chen Jun-Yuan in 1989. It is one of the superarmoured Cambrian lobopodians suspected to be either an intermediate form in the origin of velvet worms (Onychophora) or basal to at least Tardigrada and Arthropoda. It is the basis of the family name Luolishaniidae, which also include other related lobopods such as Acinocricus, Collinsium, Facivermis, and Ovatiovermis. Along with Microdictyon, it is the first lobopodian fossil discovered from China.

<span class="mw-page-title-main">Hallucigeniidae</span> Extinct family of lobopodian worms

Hallucigeniidae is a family of extinct worms belonging to the group Lobopodia that originated during the Cambrian explosion. It is based on the species Hallucigenia sparsa, the fossil of which was discovered by Charles Doolittle Walcott in 1911 from the Burgess Shale of British Columbia. The name Hallucigenia was created by Simon Conway Morris in 1977, from which the family was erected after discoveries of other hallucigeniid worms from other parts of the world. Classification of these lobopods and their relatives are still controversial, and the family consists of at least four genera.

<i>Wufengella</i> Extinct genus of invertebrates

Wufengella is a genus of extinct camenellan "tommotiid" that lived during the Early Cambrian. Described in 2022, the only species Wufengella bengtsonii was discovered from the Maotianshan Shales of Chiungchussu (Qiongzhusi) Formation in Yunnan, China. The fossil indicates that the animal was an armoured worm that close to the common ancestry of the phyla Phonorida, Brachiozoa and Bryozoa, which are collectively grouped into a clade called Lophophorata.

References

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