Tokummia

Tokummia is a genus of fossil hymenocarine arthropod, known only by one species, Tokummia katalepsis, from the middle Cambrian (508 million years old) Burgess Shale as found in a quarry in Marble Canyon in Canada.[1]

Tokummia
Temporal range:
Life restoration
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Order: †Hymenocarina
Family: †Protocarididae
Genus: †Tokummia
Species:
†T. katalepsis
Binomial name
†Tokummia katalepsis
Aria & Caron, 2017

Etymology

The genus name Tokummia named after Tokumm Creek which runs through the Marble Canyon where it was found. The species name katalepsis means Greek word for "seizing", "gasping" or "holding".[1]

Morphology

Tokummia has a cylindrical body, with the anterior half covered by a 8.78 cm (3.46 in) long bivalved carapace. At the front of the animal, there are a pair of antennae, possible eyes, mouthparts (mandibles, maxillule and maxilla) and prominent pincer-like maxillipeds. These shows the oldest record of arthropod pincers. Posterior to the maxillipeds are 50 leg-bearing trunk segments. Each of its biramous leg has 5-segmented basipods, followed by an exopod (flap-like outer branch) and 7-segmented endopod (leg-like inner branch). The anterior 10 leg pairs have basipodal endites (inner spines) while the remaining leg pairs have widen exopods. The trunk terminated with a pair of caudal rami.[1]

Paleoecology

Tokummia is suggested to be a bottom feeder, being able to walk on the sea floor, and to occasionally swim, and used its pincers to catch prey.[2]

Taxonomy

According to the original description of Tokummia, hymenocarines like Tokummia, Branchiocaris, Canadaspis and Odaraia are stem group Mandibulata, the group includes myriapods, hexapods and crustaceans,[1] and this theory is supported in multiple subsequent studies.[3][4][5][6]

References
  1. Aria, Cédric; Caron, Jean-Bernard (26 April 2017). "Burgess Shale fossils illustrate the origin of the mandibulate body plan". Nature. 545 (7652): 89–92. Bibcode:2017Natur.545...89A. doi:10.1038/nature22080. PMID 28445464. S2CID 4454526.
  2. "Ouch! U of T paleontologists identify 508-million-year-old sea creature with can opener-like pincers". University of Toronto News.
  3. Aria, Cédric; Caron, Jean-Bernard (2017-12-21). "Mandibulate convergence in an armoured Cambrian stem chelicerate". BMC Evolutionary Biology. 17 (1): 261. doi:10.1186/s12862-017-1088-7. ISSN 1471-2148. PMC 5738823. PMID 29262772.
  4. Zeng, Han; Zhao, Fangchen; Niu, Kecheng; Zhu, Maoyan; Huang, Diying (2020). "An early Cambrian euarthropod with radiodont-like raptorial appendages". Nature. 588 (7836): 101–105. Bibcode:2020Natur.588..101Z. doi:10.1038/s41586-020-2883-7. ISSN 1476-4687. PMID 33149303. S2CID 226248177.
  5. Aria, Cédric; Zhao, Fangchen; Zhu, Maoyan (2021-03-22). "Fuxianhuiids are mandibulates and share affinities with total-group Myriapoda". Journal of the Geological Society. 178 (5). Bibcode:2021JGSoc.178..246A. doi:10.1144/jgs2020-246. ISSN 0016-7649. S2CID 233952670.
  6. Izquierdo‐López, Alejandro; Caron, Jean‐Bernard (2021). Zhang, Xi‐Guang (ed.). "A Burgess Shale mandibulate arthropod with a pygidium: a case of convergent evolution". Papers in Palaeontology. 7 (4): 1877–1894. doi:10.1002/spp2.1366. ISSN 2056-2799. S2CID 236284813.
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