Scenella Temporal range: | |
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Dorsal view of the shell of Scenella tenuistriata | |
lateral view of the shell of Scenella tenuistriata | |
Scientific classification | |
Kingdom: | |
Phylum: | |
Superfamily: | |
Family: | † Scenellidae S. A. Miller, 1889 [2] |
Genus: | Scenella Billings, 1872 |
Synonyms [3] | |
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Scenella is an extinct genus of fossil invertebrate animal which is generally considered to be a mollusc; at various times it has been suggested that this genus belongs with the gastropods, the monoplacophorans, or the helcionellids, although no firm association with any of these classes has been established. [4] An affinity with the hydrozoa (as a flotation device) has been considered, [1] although some authors oppose this hypothesis. [5] A gastropod affinity is defended on the basis of six pairs of internal muscle scars, [6] whilst the serially-repeated nature of these scars suggests to other authors a monoplacophoran affinity. [1] However the specimens showing this scarring have not been convincingly shown to belong to the genus Scenella. [1] A similarity to the Ediacaran Ovatoscutum has also been drawn. [7]
The shell of Scenella is elongated along its anterior-posterior axis, and comprises concentric rings around a conical central peak. Radial and concentric corrugations exist in some species. [7] Some specimens are preserved as organic films, others appear to have been infilled with calcite. [1] They are usually preserved point-upwards, with their long axes consistently oriented; this probably represents their most stable position under their depositional current. [1] Soft parts have never been reported in association with Scenella, suggesting that the preserved fragments separated quickly from the associated tissue prior to burial. [1]
Scenella lived from the Cambrian to the Ordovician. Its remains have been found in Antarctica, Asia, Europe, and North America. Individual fossils are common throughout the Burgess shale, where they often occur in dense aggregations. [1] Where they overlap, specimens deform as by draping. [1] Specimens are sometimes cracked or torn, with margins often damaged by folding or "tattering". [1] 1206 specimens of Scenella are known from the Greater Phyllopod bed, where they comprise 2.29% of the community. [8]
Scenella is the only genus in the family Scenellidae. This family has no subfamilies and Scenella is the type genus of the family Scenellidae.
The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005 [3] categorizes Scenellidae in the superfamilia Scenelloidea within the Paleozoic molluscs of uncertain systematic position.
Species in the genus Scenella include: [9]
Species | Authority | Range |
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Scenella affinis | Ulrich and Schfield, 1897 | |
Scenella amii | (Matthew, 1902) Babcock and Robinson 1988 | Burgess Shale (Mid Cambrian, 508 million years ago) [8] |
Scenella anomala | (Billings, 1865) Wagner 2008 | |
Scenella augusta | (Billings, 1865) Wagner 2008 | |
Scenella barrandei | (Linnarsson, 1879) (Bergerg-Madsen and Peel, 1986) [10] | |
Scenella beloitensis | Ulrich and Scofield (1897) | |
Scenella clotho | Walcott, 1936 | |
Scenella compressa | Ulrich and Scofield (1897) | |
Scenella conica | Whiteaves, 1884 | |
Scenella conula | (Walcott, 1884) | |
Scenella conicum | (Whitfield, 1886) Ulrich and Scofield (1897) | |
Scenella hujingtanensis | Yu, 1979 | |
Scenella magnifica | Ulrich and Scofield (1897) | |
S.? mira | Vasil’yeva, 1994 | |
Scenella montrealensis | Billings (1865) | |
Scenella obtusa | (Sardeson, 1892) Ulrich and Scofield (1897) | |
Scenella orithyia | (Billings, 1865) Ulrich and Scofield (1897) | |
Scenella pretensa | Raymond, 1905 | |
Scenella radialis | Ulrich and Scofield (1897) | |
Scenella radians | Babcock & Robinson | |
Scenella radiata | Yu, 1979 | |
Scenella reticulata | (Billings, 1872) (type) [11] | |
Scenella retusa | (Ford, 1873) [12] | |
Scenella unicarinata | (Kobayashi, 1934) Wagner 2008 | |
Scenella varians | Walcott 1908 | |
Scenella venillia | (Billings, 1865) Wagner 2008 | |
Scenella tenuistriata | Chapman, 1911 | Mid Cambrian [13] |
Hallucigenia is a genus of lobopodian, known from Cambrian aged fossils in Burgess Shale-type deposits in Canada and China, and from isolated spines around the world. The generic name reflects the type species' unusual appearance and eccentric history of study; when it was erected as a genus, H. sparsa was reconstructed as an enigmatic animal upside down and back to front. Lobopodians are a grade of Paleozoic panarthropods from which the velvet worms, water bears, and arthropods arose.
Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte of British Columbia. Opabinia was a soft-bodied animal, measuring up to 7 cm in body length, and its segmented trunk had flaps along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a clawed proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed, where they constitute less than 0.1% of the community.
Marrella is an extinct genus of marrellomorph arthropod known from the middle Cambrian Burgess Shale of British Columbia. It is the most common animal represented in the Burgess Shale, with tens of thousands of specimens collected. Much rarer remains are also known from deposits in China.
Aysheaia is an extinct genus of soft-bodied lobopodian, known from the Middle Cambrian Burgess Shale of British Columbia, Canada
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.
Dinomischusis an extinct genus of stalked filter-feeding animals with the Cambrian period, with specimens known from the Burgess Shale and the Maotianshan Shales. While long of uncertain affintiies, recent studies have suggested it to be a stem-group ctenophore.
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.
Elrathia is a genus of trilobite belonging to Ptychopariacea known from the mid-Cambrian of Laurentia. E. kingii is one of the most common trilobite fossils in the USA locally found in extremely high concentrations within the Wheeler Formation in the U.S. state of Utah. E. kingii has been considered the most recognizable trilobite. Commercial quarries extract E. kingii in prolific numbers, with just one commercial collector estimating 1.5 million specimens extracted in a 20-year career. 1950 specimens of Elrathia are known from the Greater Phyllopod bed, where they comprise 3.7% of the community.
"...trilobite occupied the exaerobic zone, at the boundary of anoxic and dysoxic bottom waters. E. kingii consistently occur in settings below the oxygen levels required by other contemporaneous epifaunal and infaunal benthic biota and may have derived energy from a food web that existed independently of phototrophic primary productivity. Although other fossil organisms are known to have preferred such environments, E. kingii is the earliest-known inhabitant of them, extending the documented range of the exaerobic ecological strategy into the Cambrian Period."
Diraphora is an extinct genus of brachiopod that lived in the Cambrian. Its remains have been found in Australia and North America. 664 specimens of Diraphora are known from the Greater Phyllopod bed, where they comprise 1.26% of the community.
Helmetia is an extinct genus of arthropod from the middle Cambrian. Its fossils have been found in the Burgess Shale of Canada and the Jince Formation of the Czech Republic.
Chancelloria is a genus of early animals known from the Middle Cambrian Burgess Shale, the Comley limestone, the Wheeler Shale, the Bright Angel Shale and elsewhere. It is named after Chancellor Peak. It was first described in 1920 by Charles Doolittle Walcott, who regarded them as one of the most primitive groups of sponges. However, they are currently thought to be member of the group Chancelloriidae. 178 specimens of Chancelloria are known from the Greater Phyllopod bed, where they comprise 0.34% of the community.
Liangshanella is a genus of Cambrian bradoriid known from the Chengjiang biota and Burgess Shale. 6263 specimens of Liangshanella are known from the Greater Phyllopod bed, where they comprise 11.9% of the community.
Eldonia is an extinct soft-bodied cambroernid animal of unknown affinity, best known from the Fossil Ridge outcrops of the Burgess Shale, particularly in the 'Great Eldonia layer' in the Walcott Quarry. In addition to the 550 collected by Walcott, 224 specimens of Eldonia are known from the Greater Phyllopod bed, where they comprise 0.43% of the community. Species also occur in the Chengjiang biota, Siberia, and in Upper Ordovician strata of Morocco.
Takakkawia is a genus of sponge in the order Protomonaxonida and the family Takakkawiidae. It is known from the Middle Cambrian Burgess Shale that reached around 4 cm in height. Its structure comprises four columns of multi-rayed, organic spicules that align to form flanges. The spicules form blade-like structures, ornamented with concentric rings.
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.
Hamptonia is an extinct genus of sea sponge known from the Middle Cambrian Burgess Shale and the Lower Ordovician Fezouata formation. It was first described in 1920 by Charles Doolittle Walcott. 48 specimens of Hamptonia are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community.
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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, Urokodia, and Thelxiope, which together form the clade Mollisoniida, which are thought to be closely related to Chelicerata.
Pagetia is a genus of small trilobite, assigned to the Eodiscinid family Pagetiidae and which had global distribution during the Middle Cambrian. The genus contains 55 currently recognized species, each with limited spatial and temporal ranges.
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