| Oelandocaris Temporal range: | |
|---|---|
 | |
| Life restoration | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Family: | † Oelandocarididae |
| Genus: | † Oelandocaris Müller, 1983 |
| Species: | †O. oelandica |
| Binomial name | |
| †Oelandocaris oelandica Müller, 1983 | |
Oelandocaris is an extinct genus of stem-mandibulate, [1] or possibly a megacheiran, [2] within the monotypic family Oelandocarididae.
Oelandocaris has a large head segment with a possible median eye, similar to peytoiids, making up roughly one half of its body. [3] It has five tergites, each with a biramous limb pair and a spike on their ends, and a cylindrical tail segment. In addition, the head has two biramous limb pairs, antennae and antennules, the posterior similar in structure to the bodily limbs, the anterior including the possible mandibles. It also has a pair of possible great appendages. The whole animal only measures about a millimetre long, similar in size to other Orsten fauna.
As the exopods of Oelandocaris's limbs are large and flattened, it is very likely that it was a swimming animal, and presumably planktonic, based on its size.
Oelandocaris derives from the island of Öland in Sweden, a primary location for Orsten fossils, and the Greek word καρίς, meaning "shrimp" or "crab". [3]
Oelandocaris is known from six specimens, all from the Orsten lägerstatten. The original specimen only preserved the body, however more complete specimens including limbs have been found.
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.
The Thylacocephala are group of extinct probable mandibulate arthropods, that have been considered by some researchers as having possible crustacean affinities. As a class they have a short research history, having been erected in the early 1980s.
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 (pan)arthropod head problem is a long-standing zoological dispute concerning the segmental composition of the heads of the various arthropod groups, and how they are evolutionarily related to each other. While the dispute has historically centered on the exact make-up of the insect head, it has been widened to include other living arthropods, such as chelicerates, myriapods, and crustaceans, as well as fossil forms, such as the many arthropods known from exceptionally preserved Cambrian faunas. While the topic has classically been based on insect embryology, in recent years a great deal of developmental molecular data has become available. Dozens of more or less distinct solutions to the problem, dating back to at least 1897, have been published, including several in the 2000s.
Odaraia is a genus of bivalved arthropod from the Middle Cambrian. Its fossils, which reach 15 centimetres (5.9 in) in length, have been found in the Burgess Shale in British Columbia, Canada.
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 Cambrian to the upper Ordovician.
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.
Cambropachycope 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.
Bundenbachiellus is an extinct genus of arthropod described from the Lower Devonian Hunsrück Slate of Germany. This genus is known from only one species, B. giganteus. Alongside its possible relative Enalikter from Silurian, it is possible that genus is late-living example of Megacheira, "great-appendage arthropod".
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.
Acheronauta is a genus of extinct worm-shaped arthropod that lived in the early Silurian Waukesha biota fossil site in southeast Wisconsin. This arthropod was first discovered alongside the biota in 1985, but was not fully described until October 2022. This creature was recognized and described as a possible early mandibulate. This description is very important as much of the fauna of the biota remain undescribed, and its discovery has allowed for paleontologists to get a better grasp of the diversity of the arthropod fauna at the site. Multiple phylogenetic analyses were performed, and it was found that this arthropod forms a previously undiscovered clade with the Devonian stem-arthropod Captopodus, and the somewhat enigmatic group Thylacocephala.
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.
Tanazios is a genus of Silurian stem-mandibulate.
Captopodus is an extinct genus of stem-mandibulate known from the Early Devonian. This creature was described in 2012 from four fossils found in the Hunsrück Slate, an early Devonian lagerstätten in Germany that represents one of the few marine sites from the Devonian with soft tissue preservation.
Cascolus is an extinct genus of stem-mandibulate known from the Coalbrookdale Formation.
Musacaris is an extinct genus of Cambrian arthropod from the Orsten Lagerstätte, formerly synonymous with Martinssonia. It contains only a single species, Musacaris gerdgeyeri.
Rehbachiella is a genus of Cambrian crustacean comprising the only species Rehbachiella kinnekullensis. It is a possible branchiopod from the Orsten of Sweden.
Bredocaris admirabilis is a genus of pancrustacean from the Cambrian Orsten.
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