| Haikoucaris Temporal range: | |
|---|---|
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| Reconstruction of Haikoucaris ercaiensis | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | † Megacheira |
| Clade: | † Cheiromorpha |
| Genus: | † Haikoucaris Chen et al., 2004 |
| Species: | †H. ercaiensis |
| Binomial name | |
| †Haikoucaris ercaiensis Chen et al., 2004 | |
Haikoucaris is a genus of megacheiran arthropod that contains the single species Haikoucaris ercaiensis. It was discovered in the Cambrian Chengjiang biota of China. [1]
Haikoucaris measured about 38 mm in body length. [1] The elongated body compose of a semicircular head shield, 13 trunk tergites and presumely a short, spine-like telson. [1] [2] The head possess a pair of unstalked eyes, a pair well-developed great appendages, as well as 3 more appendage pairs of unknown detail. [2] Each of the great appendage consists of a 2-segmented peduncle and a 3-segmented claw. [2] Each of the trunk segment possess a pair of biramus appendages that each comprising a leaf-shaped exopod and a possibly 7-segmented endopod. [2]
Haikoucaris may have been a predator, with its great appendages and exopod suggested to be used for hunting and swimming respectively. [2]
Within megacheirans, Haikoucaris is generally accepted to be a member of the clade Cheiromorpha alongside Yohoia and Leanchoiliidae. [3] [4] [5] [6]
Sanctacaris is a Middle Cambrian arthropod from the Burgess Shale of British Columbia. It was most famously regarded as a stem-group chelicerate, a group which includes horseshoe crabs, spiders and scorpions, although subsequent phylogenetic studies have not always supported this conclusion. Its chelicerate affinities regain support in later observations, alongside the reassignment of Habelia optata as a sanctacaridid-related basal chelicerate. It has been placed as a member of the extinct family Sanctacarididae alongside Wisangocaris and Utahcaris.
Sidneyia is an extinct arthropod known from fossils found from the Early to the Mid Cambrian of China and the Mid Cambrian Burgess Shale of British Columbia, Canada.
Canadaspis is an extinct genus of bivalved Cambrian arthropod, known from North America and China. They are thought to have been benthic feeders that moved mainly by walking and possibly used its biramous appendages to stir mud in search of food. They have been placed within the Hymenocarina, which includes other bivalved Cambrian arthropods.
Jianfengia is an extinct genus of Middle Cambrian (Atdabanian) megacheiran arthropod found in the Maotianshan Shale Lagerstätte of China. It contains the single species Jianfengia multisegmentalis. The body is extremely elongated, though the animal itself was relatively small at less than 4 centimetres (1.6 in) in length. The head has a pair of stalked eyes, a hypostome/labrum complex, a pair of great appendages with five podomeres, and four pairs of biramous limbs. The maximum known number of trunk segments is 27, though most known specimens have 20, which are associated with pairs of biramous appendages, and the body ends with a telson spine. It has been placed as a member of the family Jiangfengiidae, alongside Fortiforceps and Sklerolibyon as well as possibly Parapeytoia.
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.
Habelia is a genus of extinct arthropod from the Middle Cambrian, thought to be one of the earliest known relatives of chelicerates. Its fossils have been found in the Burgess Shale in British Columbia, Canada. Fifty-four specimens of Habelia are known from the Greater Phyllopod bed, where they comprise 0.1% of the community.
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.
Pseudoiulia is a genus of Cambrian arthropod known from the Chengjiang Biota of Yunnan, China, containing the single species P. cambriensis. It is considered poorly known, but has been somewhat associated with other Chengjiang Biota fauna such as Dongshania folliformis and Pissinocaris subconigera. In 2013, Pseudoiulia was suggested to be a member of the family Kootenichelidae, alongside Kootenichela and Worthenella.
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 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 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.
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.
Kootenichela deppi is an extinct arthropod described from the Middle Cambrian of the Kootenay National Park, Canada. It is originally considered to be a member of "great appendage arthropods", although subsequent studies questioned its affinity. Kootenichela appears to be the sister taxon of Worthenella, from cladistic analysis.
Tokummia is a genus of fossil hymenocarine arthropod, known only by one species, Tokummiakatalepsis, from the middle Cambrian Burgess Shale as found in a quarry in Marble Canyon in Canada.
Offacolus is an extinct genus of euchelicerate, a group of chelicerate arthropods. Its only species, O. kingi, has been found in deposits from the Silurian period in the Wenlock Series Lagerstätte of Herefordshire, England. The genus is named after Offa, a king from the ancient kingdom of Mercia, and colus, a person who dwelled among the Offa's Dyke. The species name honors Robert Joseph King, a British mineralogist who found the fossils of Offacolus.
Hymenocarina is an order of extinct arthropods known from the Cambrian. They possess bivalved carapaces, typically with exposed posteriors. Members of the group are morphologically diverse and had a variety of ecologies, including as filter feeders and as predators. Recent research has generally considered them to be stem or crown group members of Mandibulata, due to the presence of mandibles in some species.
Kylinxia is a genus of extinct arthropod described in 2020. It was described from six specimens discovered in Yu'anshan Formation in southern China. The specimens are assigned to one species Kylinxia zhangi. Dated to 518 million years, the fossils falls under the Cambrian period. Announcing the discovery on 4 November 2020 at a press conference, Zeng Han of the Nanjing Institute of Geology and Paleontology, said that the animal "bridges the evolutionary gap from Anomalocaris to true arthropods and forms a key ‘missing link’ in the origin of arthropods," which was "predicted by Darwin’s evolutionary theory." The same day the formal description was published in Nature.
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.
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.
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.
Sklerolibyon is an extinct genus of megacheiran arthropod, known from the Cambrian aged Chengjiang biota of Yunnan, China. It is a member of the family Jianfengiidae, alongside Jianfengia and Fortiforceps, and possibly also Parapeytoia. Specimens are around 2.5 centimetres (0.98 in) in length. The body is greatly elongated, and head shield is heavily sclerotised, with a pair of spines radiating outward from the sides. Alongside the pair of great appendages, there are a pair of stalked eyes and at least two other pairs of limbs on the cephalon. The trunk has 34 segments with corresponding biramous appendages, with typically megacheiran paddle-shaped exopods. The tail is unknown but like Jianfengia probably ended in a telson spine.
Fortiforceps is an extinct genus of Cambrian megacheiran arthropod known from the Chengjiang biota of Yunnan, China. It was originally described by Hou and Bergström in 1997, and redescribed in 2020. It was relatively small, at 4 centimetres (1.6 in) or less in length. The head had a large pair of stalked eyes, a pair of frontal projections, as well as a pair of great appendages, like other megacheirans, along with two other cephalic appendages. The trunk had either 20 or 22 segments, depending on the specimen. These segments had pronounced blade-like spines on their upper-outer edge. Each of the trunk segments were associated with pairs of biramous limbs, which probably have seven podomeres and like other megacheirans, have paddle-shaped exopods. The trunk terminated with a forked tailpiece, which on their outer edges had rod-like structures. The two lobes were separated by a rectangular central piece. It has been placed as a member of the family Jiangfengiidae, alongside Jianfengia, Sklerolibyon and possibly Parapeytoia.
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