Marrella
Marrella Temporal range:
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Fossil of Marrella | |
Life reconstruction of Marrella | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | †Marrellomorpha |
Order: | †Marrellida |
Family: | †Marrellidae |
Genus: | †Marrella Walcott, 1912 |
Species: | †M. splendens
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Binomial name | |
†Marrella splendens Walcott, 1912
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Marrella is an extinct
History
Marrella was the first fossil collected by
Marrella is one of several unique arthropod-like organisms found in the Burgess Shale. Other examples are Opabinia and Yohoia. The unusual and varied characteristics of these creatures were startling at the time of discovery. The fossils, when described, helped to demonstrate that the soft-bodied Burgess fauna was more complex and diverse than had previously been anticipated.[3]
Morphology
Specimens of Marrella range from 2.4 to 24.5 millimetres (0.094 to 0.965 in) in length. The head shield had two pairs of long posteriorly curved projections/spines, the posterior pair of which had a serrated keel. There is no evidence of eyes. On the underside of the head was a pair of long and sweeping flexible antennae, composed of about total 30 segments, projecting forward at an angle of 15 to 30 degrees away from the midline. On part of the antennae, the joints between segments bear setae. Behind and slightly above the antennae attached a pair of short and stout paddle-like swimming appendages, composed of one long basal segment and five shorter segments, the edges of the latter of which were fringed with setae.[5][2]
The body had a minimum of 17 segments (
A 1998 paper suggested that striations present on the front projection of well-preserved specimens of Marrella represented a
Ecology
Marrella is likely to have been an active swimmer that swam close to the seafloor (nektobenthic) with its swimming appendages used in a backstroke motion, with the large spines acting as stabilizers, as well as possibly also having a defensive function. They have been suggested to be filter feeders, with food particles sifted out of the water column by the posterior appendages during swimming before being passed forward by the appendages towards the mouth.[5]
Taxonomy
Marrella is placed within the
Marrellida |
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Occurrence
Marrella is the most abundant genus in the Burgess Shale.[14] Most Marrella specimens herald from the 'Marrella bed', a thin horizon, but it is common in most other outcrops of the shale. Over 25,000 specimens have been collected.[15] 5028 specimens of Marrella are known from the Greater Phyllopod bed, where they comprise 9.56% of the community.[16]
A few dozen specimens of an indeterminate species of Marrella have been reported from the Kaili Formation of Yunnan, China, dating to the Wuliuan stage of the Cambrian. A single fragmentary specimen of an indeterminate species is also known from the Balang Formation of Yunnan, China, dating to Cambrian Stage 4. Both deposits are earlier than the Burgess Shale.[17]
See also
References
- OCLC 44058853.
- ^ a b c Whittington, H. B. (1971). "Redescription of Marrella splendens (Trilobitoidea) from the Burgess Shale, Middle Cambrian, British Columbia" (PDF). Bulletin – Geological Survey of Canada. 209. Geological Survey of Canada: 1–24.
- OCLC 44058853.
- ^ Haug, J. T., Castellani, C., Haug, C., Waloszek, D., Maas, A. (2012). A Marrella−like arthropod from the Cambrian of Australia: a new link between "Orsten"−type and Burgess Shale assemblages. Acta Palaeontologica Polonica 58: 629–639. doi:10.4202/app.2011.0120
- ^ a b c García-Bellido, Diego & Collins, Desmond. (2006). A new study of Marrella splendens (Arthropoda, Marrellomorpha) from the Middle Cambrian Burgess Shale, British Columbia, Canada. Canadian Journal of Earth Sciences. 43. 721-742. 10.1139/e06-012.
- PMC 1689164.
- S2CID 84616434.
The full width of each sclerite [of Wiwaxia] is striated by finely spaced longitudinal lineations. Parker (1998) argued that these were superficial – although they are not visible on surfaces imaged under SEM and do not exhibit interference under transmitted light, so might be better interpreted as internal channels indicating microvillar secretion.
- PMID 31535028.
In Canadia, longitudinal striations along chaetae, which have previously interpreted as external evidence for iridescence, are concordant with the dimensions of microvilli and represent internal rather than external features.
- .
- ^ Pratt, Brian R.; Pushie, M. Jake; Pickering, Ingrid J.; George, Graham N. Synchrotron Imaging of Burgess Shale Fossils: Evidence for Biochemical Copper (Hemocyanin) in the Middle Cambrian Arthropod Marrella splendens. Archived from the original on 2016-03-09.
- ISSN 2296-701X.
- PMID 15129272.
- ISSN 0022-3360.
- OCLC 47650949.
- S2CID 40015864.
- S2CID 53646959.
- S2CID 129018525.
External links
- "Marrella splendens". Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. Archived from the original on 2020-11-12.
- "Reconstruction of Marrella from the collections of Charles Doolittle Walcott". Historical Art Gallery. National Museum of Natural History.