Onychodictyon

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Onychodictyon
Temporal range: Cambrian Stage 3
Onychodictyon-ferox-t.jpg
Onychodictyon ferox fossil from Chengjiang
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
(unranked): Panarthropoda
Phylum: "Lobopodia"
Class: Xenusia
Order: Paronychophora
Family: Onychodictyon
Genus: Onychodictyon
Hou, Ramsköld, & Bergström, 1991
Type species
Onychodictyon ferox
Hou, Ramsköld, & Bergström, 1991
Species
  • O. ferox
  • O. gracilis
Restoration of Onychodictyon ferox 20210822 Onychodictyon ferox diagrammatic reconstruction.png
Restoration of Onychodictyon ferox

Onychodictyon is a genus of extinct lobopodian known from the Lower Cambrian Chengjiang Maotianshan Shales in the Yunnan Province in China. [1] It was characterized by a stout body covered by fleshy papillae and pairs of sclerotized plates with spines, [2] [1] [3] representing part of the diverse "armoured lobopodians" alongside similar forms such as Microdictyon and Hallucigenia . [1]

The maximum length of Onychodictyon is 70 mm (2.8 in). [1] It has a resemblance to Microdictyon (net-like sclerite ornament) [4] but also Aysheaia and tardigrade (basally-fused terminal leg pair). [5] Each leg have a pair of curved claws that are thought to have aided Onychodictyon climb onto other organisms. [6] Onychodictyon sclerites appear to have molted with some specimens exhibiting perfectly conjoined plates from successive molts. [7]

Onychodictyon is represented by two species: O. ferox which has a pair of simple eyes and feathery antenniform appendages on its head; [3] and O. gracilis which has a blunt front end without evidence of any appendages. [1]

Related Research Articles

Lobopodia Group of extinct worm-like animals with legs

The lobopodians, members of the informal group Lobopodia, or the formally erected phylum Lobopoda Cavalier-Smith (1998), 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, worm-like fossil panarthropods such as Aysheaia and Hallucigenia.

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

Hallucigenia is a genus of Cambrian animal resembling worms, known from articulated 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. Hallucigenia is later recognized as part of lobopodians, a grade of Paleozoic panarthropods where the velvet worms, water bears, and arthropods arose.

Maotianshan Shales

The Maotianshan Shales are a series of Early Cambrian deposits in the Chiungchussu Formation, famous for their Konservat Lagerstätten, deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales form one of some forty Cambrian fossil locations worldwide exhibiting exquisite preservation of rarely preserved, non-mineralized soft tissue, comparable to the fossils of the Burgess Shale. They take their name from Maotianshan Hill in Chengjiang County, Yunnan Province, China.

<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.

<i>Microdictyon</i> Extinct genus of animals

Microdictyon is an extinct armoured worm-like animal coated with net-like scleritic plates, known from the Early Cambrian Maotianshan shale of Yunnan China and other parts of the world. Microdictyon is part of the ill-defined taxon – Lobopodia – that includes several other odd worm-like animals that resembling worm with legs, such as Hallucigenia, Onychodictyon, Cardiodictyon, Luolishania, and Paucipodia. The isolated sclerites of Microdictyon are known from other Lower Cambrian deposits. Microdictyon sclerites appear to have moulted; one sclerite seems to have been preserved during ecdysis.

Panarthropoda Animal taxon

Panarthropoda is a proposed animal clade containing the extant phyla Arthropoda, Tardigrada and Onychophora. Panarthropods also include extinct marine legged worms known as lobopodians ("Lobopodia"), a paraphyletic group where the last common ancestor and basal members (stem-group) of each extant panarthropod phylum are thought to have risen. However the term "Lobopodia" is sometimes expanded to include tardigrades and onychophorans as well.

Dinocaridida 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 comes from Greek, "deinos" and "caris", referring 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, Opabinia, Pambdelurion and Kerygmachela. It is most likely paraphyletic, with Kerygmachela and Pambdelurion more basal than the clade compose of Opabinia, Radiodonta and other arthropods.

Anomalocarididae Clade of extinct arthropods

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

Jianshanopodia

Jianshanopodia decora is a Cambrian lobopodian. Its frontal, grasping appendages bear wedge-shaped plates. Its limbs branch, instead of being tipped with claws as many lobopods' are. It has a sediment-filled gut surrounded by serially repeated diverticulae. It is thought to have sucked up prey with its short 'trunk'. It mainly crawled on the sea floor, but could swim when necessary. Its mouth resembles those of anomalocaridids and priapulids.

Radiodonta Extinct order of Cambrian 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 latter 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>Miraluolishania</i> Extinct genus of lobopodians

Miraluolishania is an extinct lobopodian known from Chengjiang County in China. It is remarkable for the possession of lensed pit-eyes. The only species, Miraluolishania haikouensis, was described from the Maotianshan Shales at Haikou by Jianni Liu and Degan Shu in 2004. In 2009, a team of palaeontologists at the Yunnan University, led by Xiaoya Ma reported the discovery of 42 other specimens from Haikou. With the help of Swiss palaeontologist Jan Bergström, Ma and Hou came to the conclusion that all the specimens were the same species as Luolishania; another lobopod discovered from the Chengjian in 1989. Chengjian is 40 kms from Haikou and the fossil fauna are different. A reassessment by Liu and Shu's team at the Northwest University in 2008 established that Luolishania and Miraluolishania are distinct animals.

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

Diania is an extinct genus of lobopodian animal 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 jointed exoskeleton and Diania was suggested to be close to the origins of arthropods, but many later studies have denied this interpretation.

Megadictyon

Megadictyon is a genus of Cambrian lobopodian with similarities to Jianshanopodia and Siberion. Occasionally mis-spelt Magadictyon.

<i>Houcaris</i> Genus of radiodonts

Houcaris is a genus of tamisiocarididid radiodonts known from Cambrian Series 2 of China and the United States. It contains two species, Houcaris saron and Houcaris magnabasis, both of which were originally named as species of the related genus Anomalocaris. The genus Houcaris was established for the two species in 2021 and honors Hou Xianguang, who had discovered and named the type species H. saron in 1995 along with his colleagues Jan Bergström and Per E. Ahlberg.

Acinocricus is a genus of extinct worm 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 worm 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>Thanahita</i>

Thanahita is a genus of extinct lobopodian and known from the middle Silurian Herefordshire Lagerstätte at the England–Wales border in UK. It is monotypic and contains one species, Thanahita distos. Discovered in 2018, it is estimated to have lived around 430 million years ago and is the only known extinct lobopodian in Europe, and the first Silurian lobopodian known worldwide.

Hallucigeniidae

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 retatives are still controversial, and the family consists of at least four genera.

<i>Lenisambulatrix</i>

Lenisambulatrix is a genus of extinct worm belonging to the group Lobopodia and known from the Lower Cambrian Maotianshan shale of China. It is represented by a single species L. humboldti. The incomplete fossil was discovered and described by Qiang Ou and Georg Mayer in 2018. Due to its missing parts, its relationship with other lobopodians is not clear. It shares many structural features with another Cambrian lobopodian Diania cactiformis, a fossil of which was found alongside it.

<i>Erratus</i> Cambrian arthropod

Erratus is an extinct genus of marine arthropod from the Cambrian of China. Its type and only species is Erratus sperare. Erratus occupies a transitional position between lobopodians and true arthropods, and its discovery has helped scientists understand the early evolution of arthropod trunk appendages. Some of the stem-arthropods like radiodonts did not have legs, instead they had flap like appendages that helped them swim. Erratus on the other hand had not only flaps but also a set of primitive legs. It also supported the theory that the gills of aquatic arthropods probably evolved into the wings and lungs of terrestrial arthropods later in the Paleozoic.

References

  1. 1 2 3 4 5 Liu, Jianni; Shu, Degan; Han, Jian; Zhang, Zhifei; Zhang, Xingliang (2008). "The lobopod "Onychodictyon" from the Lower Cambrian Chengjiang Lagerstätte revisited" (PDF). Acta Palaeontologica Polonica. 53 (2): 285–292. doi: 10.4202/app.2008.0209 .
  2. Ramsköld, L.; Xianguang, Hou (1991). "New early Cambrian animal and onychophoran affinities of enigmatic metazoans". Nature. 351 (6323): 225–228. doi:10.1038/351225a0. ISSN   1476-4687. S2CID   4309565.
  3. 1 2 Ou, Qiang; Shu, Degan; Mayer, Georg (2012). "Cambrian lobopodians and extant onychophorans provide new insights into early cephalization in Panarthropoda". Nature Communications. 3 (1): 1261. doi:10.1038/ncomms2272. ISSN   2041-1723. PMC   3535342 . PMID   23232391.
  4. Steiner, M.; Hu, S.X.; Liu, J.; Keupp, H. (2012-02-02). "A new species of Hallucigenia from the Cambrian Stage 4 Wulongqing Formation of Yunnan (South China) and the structure of sclerites in lobopodians". Bulletin of Geosciences: 107–124. doi: 10.3140/bull.geosci.1280 . ISSN   1802-8225.
  5. Smith, Martin R.; Ortega-Hernández, Javier (2014). "Hallucigenia's onychophoran-like claws and the case for Tactopoda". Nature. 514 (7522): 363–366. doi:10.1038/nature13576. ISSN   1476-4687. PMID   25132546. S2CID   205239797.
  6. ""Onychodictyon ferox" Lobopodian Fossil from Chengjiang". The Virtual Fossil Museum. The Virtual Fossil Museum. Retrieved 1 December 2019.
  7. Topper, Timothy; Skovsted, Christian; Peel, John; Harper, David (2013). "Molting in the lobopodian "Onychodictyon" from the lower Cambrian of Greenland". Lethaia. 46 (4): 490–495. doi:10.1111/let.12026.