| Pararotadiscus Temporal range: | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Superphylum: | Deuterostomia |
| Stem group: | Ambulacraria |
| Clade: | † Cambroernida |
| Family: | † Rotadiscidae |
| Genus: | † Pararotadiscus Zhao and Zhu, 1994 |
| Species | |
| |
Pararotadiscus is an abundant jellyfish-like fossil from the mid-Cambrian, and one of the most abundant taxa in the Kaili biota. [1]
The Cambrian Period was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period 485.4 mya. Its subdivisions, and its base, are somewhat in flux. The period was established as "Cambrian series" by Adam Sedgwick, who named it after Cambria, the Latin name for 'Cymru' (Wales), where Britain's Cambrian rocks are best exposed. Sedgwick identified the layer as part of his task, along with Roderick Murchison, to subdivide the large "Transition Series", although the two geologists disagreed for a while on the appropriate categorization. The Cambrian is unique in its unusually high proportion of lagerstätte sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Cambrian biology surpasses that of some later periods.
The Maotianshan Shales are a series of Early Cambrian deposits in the Chiungchussu Formation, famous for their Konservat Lagerstätten, deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales form one of some forty Cambrian fossil locations worldwide exhibiting exquisite preservation of rarely preserved, non-mineralized soft tissue, comparable to the fossils of the Burgess Shale. They take their name from Maotianshan Hill in Chengjiang County, Yunnan Province, China.
Wiwaxia is a genus of soft-bodied animals that were covered in carbonaceous scales and spines that protected it from predators. Wiwaxia fossils – mainly isolated scales, but sometimes complete, articulated fossils – are known from early Cambrian and middle Cambrian fossil deposits across the globe. The living animal would have measured up to 5 cm (2 inch) when fully grown, although a range of juvenile specimens are known, the smallest being 2 millimetres (0.079 in) long.
The Kaili Formation(凯里組) is a stratigraphic formation which was deposited during the Lower and Middle Cambrian. The formation is approximately 200 metres (660 ft) thick and was named after the city Kaili in the Guizhou province of southwest China.
Leanchoilia is an megacheiran arthropod known from Cambrian deposits of the Burgess Shale in Canada and the Chengjiang biota of China. It was about 5 centimetres (2.0 in) long and had long, whip-like feelers mounted on frontal arm-like appendages. Its internal organs are occasionally preserved within the substrate in three dimensions.
Urokodia aequalis is an extinct genus of arthropod from the early Cambrian. The taxon is only known from the Maotianshan Shales of China based on some 15 specimens. Its segmentation resembles that of a millipede and it possessed head and tail shields with thorny spikes. It has some similarities to the arthropod Mollisonia that is known from both the Burgess Shale of Canada and the Kaili biota of China. Recently, the taxon has been considered a member of the order Mollisoniida, alongside Mollisonia, Thelxiope, and Corcorania, the group are suggested to be stem-chelicerates.
The Burgess Shale of British Columbia is famous for its exceptional preservation of mid-Cambrian organisms. Around 69 other sites have been discovered of a similar age, with soft tissues preserved in a similar, though not identical, fashion. Additional sites with a similar form of preservation are known from the Ediacaran and Ordovician periods.
Gordia marina is a lower Cambrian ichnofossil, and is the most common trace fossil in the Kaili biota displaying "smooth, cylindrical or subcylindrical, non-branching, winding and irregularly curving burrows, commonly self-overcrossing". Probably made by a worm-like creature displaying fodinichnial behaviour. It takes the form of unlined, curving parallel-walled burrows that often end with a nub, probably created as the creature probed the over- or under-lying sediment. It resembles Helminthopsis and Haplotichnus.
Bosworthia is a genus of branching photosynthetic alga known from the Middle Cambrian Burgess Shale. 20 specimens of Bosworthia are known from the Greater Phyllopod bed, where they comprise 0.04% of the community. One of its two original species has since been reassigned to Walcottophycus.
Mollisonia is an extinct genus of Cambrian arthropod. Species are known from the Burgess Shale, Langston Formation, and Wheeler Shale of North America, as well as the Chengjiang Biota of China. Twenty-one specimens of Mollisonia are known from the Greater Phyllopod bed, where they comprise less than 0.1% of the community. Remains possibly attributable to the genus are also known from the Ordovician Fezouata Formation of Morocco and Bøggild Fjord Formation Greenland. An observation published in 2019 suggests this genus is a basal chelicerate, closer to crown group Chelicerata than members of Habeliida. It is suggested to be closely related to Corcorania, Ecnomocaris, and Thelxiope, which together form the clade Mollisoniida, which are thought to be closely related to Chelicerata.
Eldoniids are an extinct clade of enigmatic disc-shaped animals which lived in the early to middle Paleozoic. They are characterized by their "medusoid" (jellyfish-shaped) bodies, with the form of a shallow dome opening to an offset mouth supplemented by filamentous tentacles. Internally, they have a distinctive C-shaped gut ringing around a central cavity. Most eldoniids are soft-bodied and can only be preserved in lagerstätte, but a few forms hosted small mineralized deposits.
Stellostomites is a discoidal animal known from the Cambrian Chengjiang biota and classified with the eldoniids.
Paropsonema is a discoidal animal known from the Cambrian Chengjiang biota and classified with the eldoniids.
Rotadiscus is a genus of discoidal animal known from the Cambrian Chengjiang biota and classified with the eldoniids.
Sphenothallus is a problematic extinct genus lately attributed to the conulariids. It was widespread in shallow marine environments during the Paleozoic.
Helminthopsis is the ichnogenus of a type of trace fossil that is found preserved on the bedding planes of fine-grained sedimentary rocks. It is characterized by short, curvilinear, non-branching, parallel-sided, unlined traces on bedding surfaces. It is thought to represent the submarine feeding trails of an invertebrate organism that worked the surface of muddy substrates in search of food. Because Helminthopsis traces never cross over themselves, the ichnogenus is distinguished from similar traces assigned to the Gordia ichnogenus. The similar sounding, but now obsolete, ichnogenus Helminthoida refers to a somewhat similar trace characterized by regular, back-and-forth meanders, whereas Helminthopsis traces are irregular.
The cambroernids are an informally-named clade of unusual Paleozoic animals with coiled bodies and filamentous tentacles. They include a number of early to middle Paleozoic genera noted as 'bizarre" or "orphan" taxa, meaning that their affinities with other animals, living or extinct, has long been uncertain. One leading hypothesis is that cambroernids were unusual ambulacrarian deuterostomes, related to echinoderms and hemichordates. Previously some cambroernids were compared to members of the broad invertebrate clade Lophotrochozoa; in particularly they were allied with lophophorates, a subset of lophotrochozoans bearing ciliated tentacles known as lophophores. However, this interpretation has more recently been considered unlikely relative to the deuterostome hypothesis for cambroernid origins.
The Wuliuan stage is the fifth stage of the Cambrian, and the first stage of the Miaolingian Series of the Cambrian. It was formally defined by the ICS in 2018. Its base is defined by the first appearance of the trilobite species Oryctocephalus indicus; it ends with the beginning of the Drumian Stage, marked by the first appearance of the trilobite Ptychagnostus atavus around 504.5 million years ago.
This is a list of the biota of the Burgess Shale, a Cambrian lagerstätte located in Yoho National Park in Canada.
Pseudoarctolepis is an extinct genus of bivalved arthropod known from the Cambrian period. The type species, P. sharpi was described by Brooks & Caster in 1956 from specimens found in the Wheeler Shale of Utah. It is unusual among Cambrian arthropods for having a pair of wing-like structures projecting outwards from the carapace. A second species, P. semicircularis has been described from the Kaili Biota in South China, which differs from the type species in the fact that the wings are semicircular rather than blade-like. A possible related form has been reported from the Ordovician of Portugal. They were relatively large, with some carapaces of P. sharpi reaching 11 centimetres (4.3 in) in length. The soft-bodied anatomy is poorly known, though the poorly preserved posterior anatomy of a specimen of P. sharpi is known, which consists of a narrow segmented abdomen, which ends with a pair of caudal rami. They are thought to have been actively swimming nektonic organisms. Affinities to the bivalved arthropod group Hymenocarina have been proposed, but the limited knowledge of the anatomy makes the referral tentative.