Dinomischus

Dinomischus; Temporal range: Chengjiang–Burgess Shale PreꞒ Ꞓ O S D C P T J K Pg N
	The holotype of Dinomischus isolatus collected by Walcott
Scientific classification
Kingdom:	Animalia
Phylum:	stem-group Ctenophora?
Genus:	†Dinomischus
Type species
	†Dinomischus isolatus; Conway Morris, 1977
Other species
	†D. venustusPeng et al., 2006

Last updated March 11, 2024

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.

History of study

In his pioneering excavations of the Burgess Shale, Charles Doolittle Walcott excavated the first, and at the time only, specimen. It had evidently caught his eye, for he had taken the trouble to carefully photograph it—but he never found the time to describe the organism, and it was not until 1977 that Simon Conway Morris described the animal. He tracked down two further specimens, collected by further expeditions by teams from Harvard and the Royal Ontario Museum, allowing him to produce a reconstruction.^[1]

Description

Dinomischus isolatus reached 20 mm in height,^[2] was attached to the sea floor by a stalk, and looked loosely like a flower. The cup-shaped body at the top of the stalk probably fed by filtering the surrounding seawater, and may have created a current to facilitate this.^[3] Its mouth and anus sat next to one another. Conway Morris was not able to say much about the organism. It consisted of a calyx (or body) on a long, thin stalk, surrounded by a whorl of 18 short "petals", which enclosed both openings of its U-shaped gut.^[2] The presence of this gut identified it as a metazoan, and the stem implied that it lived permanently attached to the sea floor by a small holdfast.^[1] The twenty or so "petals" borne by each organism were solid, plate-like structures, about two thirds the length of the calyx. It is speculated that they may have been covered with cilia—fine hairs—which would have wafted food down towards the organism's mouth.^[1]

Distribution

Further specimens have since been produced by similarly spectacular fossil sites in China. 13 have been found in the Chengjiang, then in 2006 one specimen was identified within the Kaili Formation.^[4] These organisms merited the erection of a new species, D. venustus, as their corrugated "petals" possessed radial rays.^[5] 13 specimens of Dinomischus are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community.^[6]

Affinity

Dinomischus is not the only sessile, stalked organism from the Cambrian, but it has no obvious relatives in other genera. Siphusauctum gregarium (known as the "tulip animal") has been recovered from the Burgess Shale, but has a clearly different basic anatomy, with multiple openings at the base of the calyx, an anus at the top, and a large six-petaled internal organ interpreted as a filter-feeding device.^[7]Dinomischus has also been likened to Eldonia and Velumbrella , although unlike Dinomischus these medusoid organisms have tentacles.^[8]

A number of affinities were considered, but on the basis of available evidence it didn't quite seem to fit into any extant phylum.^[1] The most similar organisms were the much smaller entoprocts, but even these modern organisms are difficult to classify.^[9] The new data on D. venustus have added little to the debate; while a suggestion of echinoderm affinity has been floated,^[10] no phyla are compellingly similar to the organism.^[11] Other modern ideas, even if a little tenuous, include a suggestion that the organism may have been parasitic, dwelling on the carapaces of larger organisms.^[12]

In 2019, Dinomischus and other Cambrian forms were hypothesized to be stem-gruop ctenophores. This leads to the assertion that ctenophores evolved from immotile, suspensivorous forms, a lifestyle similar to that of polyps.^[13] Cladogram after Zhao et al., 2019:

Crown Cnidaria

Xianguangia

Daihua

Dinomischus

Siphusauctum

	Galeactena

	Crown Ctenophora

A later study suggested that Dinomischus, Diahua and Xianguangia formed a clade, Dinomischidae, with Siphusauctum more closely related to modern ctenophores.^[14]

Related Research Articles

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The Maotianshan Shales (帽天山页岩) are a series of Early Cambrian sedimentary 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 of British Columbia, Canada. They take their name from Maotianshan Hill in Chengjiang County, Yunnan Province, China.

Nectocaris is a genus of squid-like animal of controversial affinities known from the Cambrian period. The initial fossils were described from the Burgess Shale of Canada. Other similar remains possibly referrable to the genus are known from the Emu Bay Shale of Australia and Chengjiang Biota of 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 centimetres (2 in) when fully grown, although a range of juvenile specimens are known, the smallest being 2 millimetres (0.08 in) long.

Ottoia is a stem-group archaeopriapulid worm known from Cambrian fossils. Although priapulid-like worms from various Cambrian deposits are often referred to Ottoia on spurious grounds, the only clear Ottoia macrofossils come from the Burgess Shale of British Columbia, which was deposited 508 million years ago. Microfossils extend the record of Ottoia throughout the Western Canada Sedimentary Basin, from the mid- to late- Cambrian. A few fossil finds are also known from China.

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.

Leanchoilia is a megacheiran arthropod known from Cambrian deposits of the Burgess Shale in Canada and the Chengjiang biota of China.

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<i>Odaraia</i> Extinct genus of crustaceans

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.

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.

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The fossils of the Burgess Shale, like the Burgess Shale itself, are fossils that formed around 505 million years ago in the mid-Cambrian period. They were discovered in Canada in 1886, and Charles Doolittle Walcott collected over 65,000 specimens in a series of field trips up to the alpine site from 1909 to 1924. After a period of neglect from the 1930s to the early 1960s, new excavations and re-examinations of Walcott's collection continue to reveal new species, and statistical analysis suggests that additional discoveries will continue for the foreseeable future. Stephen Jay Gould's 1989 book Wonderful Life describes the history of discovery up to the early 1980s, although his analysis of the implications for evolution has been contested.

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.

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Siphusauctum is an extinct genus of filter-feeding animals that lived during the Middle Cambrian about 510 million years ago.

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Vetulicola rectangulata is a species of extinct animal from the Early Cambrian of the Chengjiang biota of China. Regarded as a deuterostome, it has characteristic rectangular anterior body on which the posterior tail region is attached. It was described by Luo Huilin and Hu Shi-xue in 1999.

Hallucigeniidae is a family of extinct worms belonging to the group Lobopodia that originated during the Cambrian explosion. It is based on the species Hallucigenia sparsa, the fossil of which was discovered by Charles Doolittle Walcott in 1911 from the Burgess Shale of British Columbia. The name Hallucigenia was created by Simon Conway Morris in 1977, from which the family was erected after discoveries of other hallucigeniid worms from other parts of the world. Classification of these lobopods and their relatives are still controversial, and the family consists of at least four genera.

This is a list of the biota of the Burgess Shale, a Cambrian lagerstätte located in Yoho National Park in Canada.

Daihua sanqiong is a possible ancestor of comb jellies. It was a sessile relative to comb jellies. It had combs with cillia just like modern day comb jellies.

References

1 2 3 4 Conway Morris, S. (1977). "A new entoproct-like organism from the Burgess Shale of British Columbia" (PDF). Palaeontology . 20 (4): 833–845.
1 2 Hou, X.-G. (2004). The Cambrian Fossils of Chengjiang, China : The Flowering of Early Animal Life. Blackwell Publishing. ISBN 978-1-4051-0673-3.
↑ "Dinomischus isolatus". Hooper Virtual Paleontological Museum.
↑ Peng, J.; Zhao, Y.; Lin, J.-P. (2006). "Dinomischus from the Middle Cambrian Kaili Biota, Guizhou, China". Acta Geologica Sinica . 80 (4): 498–501.
↑ Hagadorn, J.W. (2002). "Chengjiang: Early Record of the Cambrian Explosion". In Bottjer, D.J.; Etter, W.; Hagadorn, J.W.; Tang, C.M. (eds.). Exceptional Fossil Preservation: a unique view on the evolution of marine life. Columbia University Press. ISBN 978-0-231-10255-1.
↑ Caron, Jean-Bernard; Jackson, Donald A. (October 2006). "Taphonomy of the Greater Phyllopod Bed community, Burgess Shale". PALAIOS. 21 (5): 451–65. Bibcode:2006Palai..21..451C. doi:10.2110/palo.2003.P05-070R. JSTOR 20173022. S2CID 53646959.
↑ O'Brien, Lorna J.; Caron, Jean-Bernard (2012-01-18). "A New Stalked Filter-Feeder from the Middle Cambrian Burgess Shale, British Columbia, Canada". PLOS ONE. 7 (1): e29233. Bibcode:2012PLoSO...729233O. doi: 10.1371/journal.pone.0029233 . ISSN 1932-6203. PMC 3261148 . PMID 22279532.
↑ Dzik, J. (1991). "Is fossil evidence consistent with traditional views of the early metazoan phylogeny?" (PDF): 47–56.{{cite journal}}: Cite journal requires |journal= (help)
↑ Lieberman, B.S. (2008). "The Cambrian radiation of bilaterians: Evolutionary origins and palaeontological emergence; earth history change and biotic factors". Palaeogeography, Palaeoclimatology, Palaeoecology . 258 (3): 180–188. Bibcode:2008PPP...258..180L. doi:10.1016/j.palaeo.2007.05.021.
↑ Chen, J.Y.; Zhou, G.Q. (1997). "Biology of the Chengjiang fauna". Bull. Natl. Mus. Nat. Sci. 10: 11–105.
↑ Conway Morris, S. (1987). "Cambrian enigmas". Geology Today . 3 (3–4): 88–92. doi:10.1111/j.1365-2451.1987.tb00495.x.
↑ Bassett, M.G.; Popov, L.E.; Holmer, L.E. (2004). "The Oldest-Known Metazoan Parasite?" (PDF). Journal of Paleontology . 78 (6): 1214–1216. doi:10.1666/0022-3360(2004)078<1214:TOMP>2.0.CO;2. ISSN 0022-3360. S2CID 86756106.
↑ Zhao, Yang; Vinther, Jakob; Parry, Luke A.; Wei, Fan; Green, Emily; Pisani, Davide; Hou, Xianguang; Edgecombe, Gregory D.; Cong, Peiyun (2019-04-01). "Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan". Current Biology. 29 (7): 1112–1125.e2. doi:10.1016/j.cub.2019.02.036. hdl: 1983/40a6bcb8-a740-482c-a23c-7d563faea5c5 . ISSN 0960-9822. PMID 30905603. S2CID 84844387.
↑ Zhao, Yang; Hou, Xian-guang; Cong, Pei-yun (2023-01-01). "Tentacular nature of the 'column' of the Cambrian diploblastic Xianguangia sinica" (PDF). Journal of Systematic Palaeontology. 21 (1). doi: 10.1080/14772019.2023.2215787 . ISSN 1477-2019.

External links

"Dinomischus isolatus". Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011.