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Amplectobeluidae
Extinct clade of Cambrian organisms From Wikipedia, the free encyclopedia
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Amplectobeluidae is a clade of Cambrian radiodonts. It currently includes five definitive genera, Amplectobelua, Lyrarapax, Ramskoeldia, Guanshancaris and a currently unnamed genus from the lower Cambrian aged Sirius Passet site in Greenland.[1] There is also a potential fifth genus, Houcaris, but that genus has become problematic in terms of its taxonomic placement.[2][3]
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Definition
In 2014, Amplectobeluidae was defined as the most inclusive clade including Amplectobelua symbrachiata but not Anomalocaris canadensis, Tamisiocaris borealis, or Hurdia victoria.[4]
Description
Amplectobeluids could be recognized by frontal appendages with well-developed first distal endite, which forming a pincer-like structure that presumably better suited for a grasping function.[4][5] Complete body fossils of amplectobeluids are only known by Amplectobelua and Lyrarapax, both showing combination of characters resembling Anomalocaris (i.e. streamlined body; small head with ovoid sclerites; well-developed swimming flaps; a pair of caudal furcae).[6][7][8][9][10] Another distinctive features only known in amplectobeluid genera were pairs of gnathobase-like structures (known by Amplectobelua and Ramskoeldia),[9][11] or an oral cone with combination of tetraradial arrangement and scale-like nodes (known by Lyrarapax and Guanshancaris).[8][12][13]
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Classification
Early in 2014, "Anomalocaris" kunmingensis was tentatively assigned to Amplectobelua by Vinther et al.[4] Later that year, however, the discoverers of Lyrarapax unguispinus ignored that assessment and created a genus within Amplectobelua sensu Vinther et al.[7] An indeterminate frontal appendage assignable to this group is known from the Parker Slate of Vermont.[14]
Phylogeny
An a posteriori-weighted phylogenetic analysis in 2014 found the following relationships within the Amplectobeluidae:[7]
References
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