| Cupitheca | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Superphylum: | Lophotrochozoa |
| Class: | † Hyolitha |
| Order: | † incertae sedis |
| Genus: | † Cupitheca |
Cupitheca is a genus of Cambrian hyolith with the unusual distinction of shedding the apex of its camerate conical shell. As with Triplicatella and Hyptiotheca , its designation to the hyolithids or orthrothecids is not straightforward, exhibiting as it does a mixture of the characters that would normally demark the two subtaxa of Hyolitha. [1]
Agnostida is an order of arthropod which have classically been seen as a group of highly modified trilobites, though some recent research has doubted this placement. Regardless, they appear to be close relatives as part of the Artiopoda. They are present in the Lower Cambrian fossil record along with trilobites from the Redlichiida, Corynexochida, and Ptychopariida orders, and were highly diverse throughout the Cambrian. Agnostidan diversity severely declined during the Cambrian-Ordovician transition, and the last agnostidans went extinct in the Late Ordovician.
Hyoliths are animals with small conical shells, known as fossils from the Palaeozoic Era. They are at least considered as lophotrochozoan, and possibly belongs to lophophorates, a group which includes the brachiopods, while others consider it as basal lophotrochozoan, or even mollusc.
Sidneyia is an extinct arthropod known from fossils found from the Early Cambrian-age Maotianshan Shales to the Mid Cambrian Burgess Shale formation of British Columbia. 144 specimens of Sidneyia are known from the Greater Phyllopod bed, where they comprise 0.27% of the community.
The Emu Bay Shale is a geological formation in Emu Bay, South Australia, containing a major Konservat-Lagerstätte. It is one of two in the world containing Redlichiidan trilobites. The Emu Bay Shale is dated as Cambrian Series 2, Stage 4, correlated with the upper Botomian Stage of the Lower Cambrian.
Haplophrentis is a genus of tiny shelled hyolithid which lived in the Cambrian Period. Its shell was long and conical, with the open end protected by an operculum, from which two fleshy arms called helens protruded at the sides. These arms served to elevate the opening of the shells above the sea floor, acting like stilts.
A number of assemblages bear fossil assemblages similar in character to that of the Burgess Shale. While many are also preserved in a similar fashion to the Burgess Shale, the term "Burgess Shale-type fauna" covers assemblages based on taxonomic criteria only.
The end-Botomian mass extinction event, also known as the late early Cambrian extinctions, refer to two extinction intervals that occurred during Stages 4 and 5 of the Cambrian Period, approximately 513 to 509 million years ago. Estimates for the decline in global diversity over these events range from 50% of marine genera up to 80%. Among the organisms affected by this event were the small shelly fossils, archaeocyathids, trilobites, brachiopods, hyoliths, and mollusks.
Cambrorhytium is an enigmatic fossil genus known from the Latham Shale (California), and the Chengjiang (China) and Burgess Shale lagerstätte. 350 specimens of Cambrorhytium are known from the Greater Phyllopod bed, where they comprise 0.7% of the community.
Salterella is an enigmatic Cambrian genus with a small, conical, calcareous shell that appears to be septate, but is rather filled with stratified laminar deposits. The shell contains grains of sediment, which are obtained selectively by a manner also observed in foramanifera. The genus was established by Elkanah Billings in 1861, and was named after the English palaeontologist John William Salter.
The Mount Cap Formation is a geologic formation exposed in the Mackenzie Mountains, northern Canada. It was deposited in a shallow shelf setting in the late Early Cambrian, and contains an array of Burgess Shale-type microfossils that have been recovered by acid maceration.
The cephalopods have a long geological history, with the first nautiloids found in late Cambrian strata, and purported stem-group representatives present in the earliest Cambrian lagerstätten.
Stenothecoida is a taxon of bivalved fossils from the Early to middle Cambrian period. They look a bit like brachiopods or bivalve molluscs.
Turcutheca is a Tommotian genus of shelly fossil whose affinities are uncertain, generally considered as an orthothecid hyolith (which would make it a brachiopod, but also resembling the ellesmeroceratids.
Mobergella is a millimetric Lower Cambrian shelly fossil of unknown affinity, usually preserved in phosphate and particularly well known from Swedish strata, where it is diagnostic of lowermost Cambrian rocks. Originally interpreted as a monoplacophoran, the circular, cap-shaped shell resembles a hyolith operculum, with concentric rings on its upper surface, and seven pairs of internal muscle scars. It is never found in association with a conch, and its affinity therefore remains undetermined. Nevertheless, its heavy musculature does seem to indicate that it functioned as an operculum.
The orthothecids are one of the two hyolith orders.
Hyolithellus is a conical tubular fossil from the Cambrian, originally considered a hyolith but since reinterpreted tentatively as an annelid worm.
Eximipriapulus is a genus of priapulid-like organisms, perhaps belonging to the crown group, known from the Chengjiang biota.
Conotheca is a genus of Cambrian hyoliths.
Hyolithohelminths are phosphatic tubular fossils from the Cambrian period. They were sedentary, possibly infaunal, organisms; once thought to have opercula, these structures are now understood to be unrelated shells.
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