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. (Note: speculative frontal appendage morphology is now known to be incorrect)
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
Species
  • O. amplusHou et al., 2006
  • O. qiongqiiLi et al., 2024

Omnidens, meaning "all-tooth", is an extinct genus of large Cambrian animal known only from a series of large mouth apparatus and sclerotized talon-like structures, 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, potentially even 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. Its specific name, amplus, means "large" or "giant". Omnidens was later identified as a close relative of the gilled lobopodian Pambdelurion. [2] . In 2024, additional remains were described from Xiaoshiba Lagerstätte, which were proposed as a new species, O. qionqii, after the mythical, man-eating Qiongqi, one of four ancient creatures in Chinese mythology, whose name means "distressingly strange". [4]

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.
A fossil of the partial mouth apparatus of Omnidens qiongqii from the Xiaoshiba Lagerstatte of China, in association with a small trilobite. Omnidens qiongqii fossil.jpg
A fossil of the partial mouth apparatus of Omnidens qiongqii from the Xiaoshiba Lagerstätte of China, in association with a small trilobite.

Omnidens is known primiarly from large mouthparts, and more recently, distal portions of the frontal appendages. 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. The mouth, unlike the oral cones of radiodonts, was arranged bilaterally, forming two laterally opposing sets of "jaws", composed of a number of tooth-plates, which are further divided into a basal plate and a nail-like spine. The frontal appendages are known from their distal-most portions, which appear as wide, heavily sclerotized bases, bearing a bilaterally symmetrical series of long talons. Additionally, elements which may represent bilaterally symmtrical head carapaces, and a number of small setal-blade like strucures, have been found associated with the mouthparts and talons. [4]

Classification

Onychophora

Phylogenetic relationships of Panarthropoda, [5] with possible bearers of the Omnidens mouthparts bolded

Omnidens is classified as a stem-group arthropod. [2] and, due to the striking similarities in their unconventional mouthparts, Omnidens is consistenlty found as a sister-taxon to the "gilled lobopodian" Pambdelurion whittingtoni. [2] [4] [6]

Distribution

Omnidens is found in both the Chengjiang Biota and the Xiaoshiba Lagerstätte of China, putting their age at approximately 520 Ma, during Cambrian Stage 3. [7] O. amplus and O. qiongqii are both known from the Chengjiang, but O. qiongqii is the only Omnidens species present at Xioashiba, where it is found in relative abundance (hundreds of specimens, primarily mouthparts). [4] [8] 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. However, other genera like Kerygmachela and Pambdelurion are often referred to as “gilled lobopodians”.

<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.

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

Dinocaridida is a proposed fossil taxon of basal arthropods, which flourished during the Cambrian period and survived up to Early Devonian. 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>Amplectobelua</i> Extinct genus of radiodont

Amplectobelua is an extinct genus of late Early Cambrian amplectobeluid radiodont, a group of stem arthropods that mostly lived as free-swimming predators during the first half of the Paleozoic Era.

<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>Kerygmachela</i> Extinct gilled lobopod

Kerygmachela kierkegaardi is a kerygmachelid gilled lobopodian from the Cambrian Stage 3 aged Sirius Passet Lagerstätte in northern Greenland. Its anatomy strongly suggests that it, along with its relative Pambdelurion whittingtoni, was a close relative of radiodont and euarthropods. The generic name "Kerygmachela" derives from the Greek words Kerygma (proclamation) and Chela (claw), in reference to the flamboyant frontal appendages. The specific name, "kierkegaardi" honors Danish philosopher Søren Kierkegaard.

<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>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. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and used for a variety of functions. Radiodonts are among the earliest large predators, 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 gainesi, Cambroraster falcatus and Amplectobelua symbrachiata. The later surviving members include the subfamily Aegirocassisinae from the Early Ordovician of Morocco and the Early Devonian member Schinderhannes bartelsi from Germany.

<i>Cucumericrus</i> Extinct genus of arthropod

Cucumericrus ("cucumber-leg") is an extinct genus of stem-arthropod. The type and only species is Cucumericrus decoratus, with fossils discovered from the Maotianshan Shales of Yunnan, China.

<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.

<i>Onychodictyon</i> Extinct genus of worms

Onychodictyon is a genus of extinct lobopodian known from the Lower Cambrian Chengjiang Maotianshan Shales in the Yunnan Province in China. It was characterized by a stout body covered by fleshy papillae and pairs of sclerotized plates with spines, representing part of the diverse "armoured lobopodians" alongside similar forms such as Microdictyon and Hallucigenia.

<i>Houcaris</i> Genus of radiodonts

Houcaris is a possibly paraphyletic radiodont genus, tentatively assigned to either Amplectobeluidae, Anomalocarididae or Tamisiocarididae, known from Cambrian Series 2 of China and the United States. The type species is Houcaris saron which was originally described as a species of the related genus Anomalocaris. Other possible species include H. magnabasis and H. consimilis. The genus Houcaris was established for the two species in 2021 and honors Hou Xianguang, who had discovered and named the type species Anomalocaris saron in 1995 along with his colleagues Jan Bergström and Per E. Ahlberg.

<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.

<i>Parvibellus</i> Extinct Genus of Panarthropod

Parvibellus is an extinct genus of panarthropod animal known from the Cambrian of China. It is known from only a single species, P. atavus, found in the Cambrian Stage 3 aged Chengjiang Biota of Yunnan, China.

<i>Shucaris</i> Genus of radiodont from the Early Cambrian

Shucaris is a genus of radiodont of uncertain taxonomic placement from the Lower Cambrian Maotianshan Shales in Yunnan, South China. The type and only species is S. ankylosskelos, known from multiple specimens comprising frontal appendages, multiple endites, gnathobase‐like structures, a nearly complete body, a head carapace complex, and one body flap associated with setal blades.

References

  1. 1 2 3 4 Hou, Xianguang; Bergström, Jan; Jie, Yang (2006). "Distinguishing anomalocaridids from arthropods and priapulids". Geological Journal. 41 (3–4): 259–269. Bibcode:2006GeolJ..41..259X. doi:10.1002/gj.1050. S2CID   83582128.
  2. 1 2 3 4 5 6 7 8 Vinther, Jakob; Porras, Luis; Young, Fletcher J.; Budd, Graham E.; Edgecombe, Gregory D. (2016). "The mouth apparatus of the Cambrian gilled lobopodian Pambdelurion whittingtoni". Palaeontology. 59 (6): 841–849. Bibcode:2016Palgy..59..841V. doi:10.1111/pala.12256. hdl: 1983/16da11f1-5231-4d6c-9968-69ddc5633a8a . ISSN   1475-4983. S2CID   88758267.
  3. ↑ Chen, Jun-Yuan; Ramskold, Lars; Zhou, Gui-Qing (1994). "Evidence for Monophyly and Arthropod Affinity of Cambrian Giant Predators". Science. 264 (5163): 1304–1308. Bibcode:1994Sci...264.1304C. doi:10.1126/science.264.5163.1304. PMID   17780848. S2CID   1913482.
  4. 1 2 3 4 Li, Wei; Yang, Jie; Yang, Xiaoyu; Dhungana, Alavya; Wang, Yu; Zhang, Xiguang; Smith, Martin R. (November 2024). "Omnidens appendages and the origin of radiodont mouthparts". Papers in Palaeontology. 10 (6). doi:10.1002/spp2.1600. ISSN   2056-2799.
  5. ↑ Howard, Richard J.; Hou, Xianguang; Edgecombe, Gregory D.; Salge, Tobias; Shi, Xiaomei; Ma, Xiaoya (2020). "A Tube-Dwelling Early Cambrian Lobopodian". Current Biology. 30 (8): 1529–1536.e2. doi: 10.1016/j.cub.2020.01.075 . ISSN   0960-9822. PMID   32109391.
  6. ↑ McCall, Christian R. A. (September 2023). "A large pelagic lobopodian from the Cambrian Pioche Shale of Nevada". Journal of Paleontology. 97 (5): 1009–1024. doi:10.1017/jpa.2023.63. ISSN   0022-3360.
  7. ↑ Hofmann, M. H.; Li, X. H.; Chen, J.; MacKenzie, L. A.; Hinman, N. W. (2016). "Provenance and temporal constraints of the Early Cambrian Maotianshan Shale, Yunnan Province, China". Gondwana Research. 37: 348–361. Bibcode:2016GondR..37..348H. doi: 10.1016/j.gr.2015.08.015 .
  8. ↑ Li, Wei; Yang, Jie; Zhang, Xiguang (2018). 寒武系第3阶小石坝化石库Omnidens-like口器研究. 中国古生物学会第十二次全国会员代表大会暨第29届学术年会论文摘要集.
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