| Wujicaris Temporal range: Early Cambrian, | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Clade: | Mandibulata |
| Clade: | Pancrustacea |
| Genus: | † Wujicaris Zhang et al, 2010 |
| Species: | †W. muelleri |
| Binomial name | |
| †Wujicaris muelleri Zhang et al, 2010 | |
Wujicaris muelleri is an Early Cambrian crustacean, from the Maotianshan Shales of China.
Wujicaris is a crustacean known from the Chengjiang Lagerstatte, uniquely fossilised in Orsten-type preservation and known from four larval specimens in the early metanauplius stage roughly 270 μm long. It and the possibly related taxon Yicaris both heavily resemble the metanaupli of modern crustaceans such as barnacles, [1] thus possibly suggesting the existence of Thecostraca during the Cambrian. [2] Wujicaris possesses a large, pointed cephalic shield with an oval structure tentatively dubbed the "dorsal organ", a pair of possibly median eyes, an unsegmented body along with five pairs of appendages, three of those being mouthparts and the other two being antennae. In addition, the labrum and hypostome are fused together, forming a large complex near the front of the organism.
Wujicaris derives from the town of Wuji, along with the word caris, meaning "shrimp". The specific name, muelleri honours the late Klaus Müller, discoverer of Orsten-type preservation. [2]
The Chaetognatha or chaetognaths are a phylum of predatory marine worms that are a major component of plankton worldwide. Commonly known as arrow worms, they are mostly nektonic; however about 20% of the known species are benthic, and can attach to algae and rocks. They are found in all marine waters, from surface tropical waters and shallow tide pools to the deep sea and polar regions. Most chaetognaths are transparent and are torpedo shaped, but some deep-sea species are orange. They range in size from 2 to 120 millimetres.
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”.
A nostril is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation. Fish do not breathe through noses, but they do have two small holes used for smelling, which can also be referred to as nostrils.
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.
The Pentastomida are an enigmatic group of parasitic arthropods commonly known as tongue worms due to the resemblance of the species of the genus Linguatula to a vertebrate tongue; molecular studies point to them being highly-derived crustaceans.
Waptia is an extinct genus of arthropod from the Middle Cambrian of North America. It grew to a length of 6.65 cm (3 in), and had a large bivalved carapace and a segmented body terminating into a pair of tail flaps. It was an active swimmer and likely a predator of soft-bodied prey. It is also one of the oldest animals with direct evidence of brood care. Waptia fieldensis is the only species classified under the genus Waptia, and is known from the Burgess Shale Lagerstätte of British Columbia, Canada. Specimens of Waptia are also known from the Spence Shale of Utah, United States.
The Cambrian explosion is an interval of time beginning approximately 538.8 million years ago in the Cambrian period of the early Paleozoic, when a sudden radiation of complex life occurred and practically all major animal phyla started appearing in the fossil record. It lasted for about 13 to 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well.
Tardigrades, known colloquially as water bears or moss piglets, are a phylum of eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them Kleiner Wasserbär'little water bear'. In 1776, the Italian biologist Lazzaro Spallanzani named them Tardigrada, which means 'slow steppers'.
Arthropods are invertebrates in the phylum Arthropoda. They possess an exoskeleton with a cuticle made of chitin, often mineralised with calcium carbonate, a body with differentiated (metameric) segments, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They form an extremely diverse group of up to ten million species.
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 Cambrian to the upper Ordovician.
Ercaicunia is genus of bivalved Cambrian arthropod from the Chengjiang biota of Yunnan, China. It contains a single species, E. multinodosa that was described by Luo et al. in 1999. The total length of the body ranges from 8 to 11 millimetres. The bivalved carapace covered about a third of the total body-length, and has up to six serrations on its forward edge. The head has a pair of large uniramous antennae, as well as a smaller pair of secondary antennae, as well as pair of mandibles and maxillae. The trunk has 16 pairs of biramous appendages. Specimens were CT scanned in 2019, which suggested it to be a stem-group crustacean. Other subsequent studies have recovered it as a member of Hymenocarina, which contains other bivalved Cambrian arthropods.
Hadranax is a genus of large lobopodian known from the lower Cambrian Sirius Passet Lagerstätte. This genus is characterized from other lobopodians due to multiple groups of four nodes running along its trunk region, similar to Kerygmachela, and a pair of extremely large frontal appendages that were possibly as long as the animal's entire body. This lobopodian is one of the rarer members of the Sirius Passet fauna, with only around three fragmentary specimens being known.
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.
Carbotubulus is a genus of extinct worm belonging to the group Lobopodia and known from the Carboniferous Carbondale Formation of the Mazon Creek area in Illinois, US. A monotypic genus, it contains one species Carbotubulus waloszeki. It was discovered and described by Joachim T. Haug, Georg Mayer, Carolin Haug, and Derek E.G. Briggs in 2012. With an age of about 300 million years, it is the first long-legged lobopodian discovered after the period of Cambrian explosion.
Balhuticaris is a genus of extinct bivalved hymenocarine arthropod that lived in the Cambrian aged Burgess Shale in what is now British Columbia around 506 million years ago. This extremely multisegmented arthropod is the largest member of the group, and it was even one of the largest animals of the Cambrian, with individuals reaching lengths of 245 mm (9 in). Fossils of this animal suggests that gigantism occurred in more groups of Arthropoda than had been previously thought. It also presents the possibility that bivalved arthropods were very diverse, and filled in a lot of ecological niches.
Phosphatocopina is an extinct group of bivalved arthropods known from the Cambrian period. They are generally sub-milimetric to a few millimetres in size. They are typically only known from isolated carapaces, but some found in Orsten-type phosphatized preservation have their bodies preserved in high fidelity in three dimensions.
Goticaris is a genus of small extinct Cambrian arthropods, known from the Orsten lagerstätten in southern Sweden. It appears to have several apomorphic features, notably including a single large compound eye.
Musacaris is an extinct genus of Cambrian arthropod from the Orsten Lagerstätte, formerly synonymous with Martinssonia. It contains only a single species, Musacaris gerdgeyeri.
Cambrocaris baltica is an Upper Cambrian arthropod from Poland.