| Parvibellus Temporal range: | |
|---|---|
 | |
| Holotype specimen | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Superphylum: | Ecdysozoa |
| (unranked): | Panarthropoda |
| Genus: | † Parvibellus |
| Species: | †P. atavus |
| Binomial name | |
| †Parvibellus atavus Liu et al. 2022 | |
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.
Parvibellus is small panarthropod with length of around 5 mm (0.20 in). The head bore a pair of small frontal appendages and ventrally directed circular mouth. There is no evidence that Parvibellus had eyes. The elongated trunk possesses 11 pairs of lateral appendages and a pair of terminal projections. [1]
In the original description, The trunk appendages were interpreted as swimming flaps, which suggest a nektonic life style and close relationship with stem-group arthropods such as the "gilled lobopodians" Kerygmachela and Pambdelurion , opabiniids and radiodonts. [1] However, recent research suggests it may instead be a larval siberiid, a group of benthic lobopodian nest within arthropod stem-group, and the trunk appendages were re-interpreted as stout lobopods. Since it may represent the larva of any described siberiids from the same strata (e.g. Megadictyon , Jianshanopodia ) and cannot be accurately identified, Parvibellus is considered to be a nomen dubium. [2]
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.
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.
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.
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.
Anomalocaris is an extinct genus of radiodont, an order of early-diverging stem-group arthropods.
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.
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.
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.
Megacheira is an extinct class of predatory arthropods defined by their possession of spined "great appendages". Their taxonomic position is controversial, with studies either considering them stem-group euarthropods, or stem-group chelicerates. The homology of the great appendages to the cephalic appendages of other arthropods is also controversial. Uncontested members of the group were present in marine environments worldwide from the lower to middle Cambrian.
Jianshanopodia is a monotypic genus of Cambrian lobopodian, discovered from Maotianshan Shales of Yunnan, China.
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.
Cucumericrus decoratus is a species of putative radiodont known from a few poorly preserved specimens. Only fragments of trunk cuticle and corresponded appendages had been revealed, while important radiodont features such as frontal appendages are unknown in this species. The trunk cuticle possess irregular wrinkles and may had been soft in life. Each of the trunk appendage compose of a dorsal flap-like element and a ventral stubby leg with unknown distal region, structurally comparable to the trunk appendages of gill lobopodians and euarthropod biramous appendages. The legs have been interpreted as somewhere between annulated lobopod legs and segmented arthropod legs.
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.
Megadictyon is a genus of Cambrian lobopodian with similarities to Jianshanopodia and Siberion. Occasionally mis-spelt Magadictyon.
Erratus is an extinct genus of marine arthropod from the Cambrian of China. Its type and only species is Erratus sperare. Erratus is likely one of the most basal known 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.
Deuteropoda is a proposed clade of arthropods whose members are distinguished from more basal stem-group arthropods like radiodonts by an anatomical reorganization of the head region, namely the appearance of a differentiated first appendage pair, a multisegmented head, a hypostome/labrum complex, and by bearing pairs of segmented biramous limbs.
Laminacaris is a genus of extinct stem-group arthropods (Radiodonta) that lived during the Cambrian period. It is monotypic with a single species Laminacaris chimera, the fossil of which was described from the Chengjiang biota of China in 2018. Around the same time, two specimens that were similar or of the same species were discovered at the Kinzers Formation in Pennsylvania, USA. The first specimens from China were three frontal appendages, without the other body parts.
Mieridduryn is a genus of extinct 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 shale type lagerstätte located in the country of Wales. This animal's taxonomic affinities are somewhat unclear, but there are some hypotheses. One is that this animal represents a new grade of stem-euarthropods that evolved features similar to the Cambrian aged opabiniids. Another is that if the features seen in Mieridduryn are convergent, and not homologous, to those seen in radiodonts, then this animal represents a late surviving opabiniid.
Kerygmachelidae is a family of gilled lobopodians from the Cambrian period. Currently three genera are included in the family: Kerygmachela from the lower Cambrian of Greenland, Utahnax from the middle Cambrian of Utah, and Mobulavermis from the lower-middle Cambrian of Nevada. These animals are characterized by well developed frontal appendages similar to other dinocaridids like the radiodonts, except the ones present in these genera are horizontal to one another, and do not curve downward. These animals were most likely nektonic predators, using their large trunk flaps to swim in the water column, and using their frontal appendages to grab small-sized prey.
Mobulavermis is an extinct genus of Cambrian kerygmachelid lobopodian from the Pioche Shale, the Combined Metals Member of the Pioche Formation in Nevada; USA. The type species is M. adustus, known from the holotype and paratype.