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. There is also a potential fifth genus, Houcaris, but that genus has become problematic in terms of its taxonomic placement.
Definition
In 2014, Amplectobeluidae was defined as the most inclusive clade including Amplectobelua symbrachiata but not Anomalocaris canadensis, Tamisiocaris borealis, or Hurdia victoria.
Description Amplectobeluids have frontal appendages with a well-developed first distal endite, which forms a pincer-like structure suited for grasping. Complete body fossils of amplectobeluids are only known for Amplectobelua and Lyrarapax, both showing a combination of characters resembling those of Anomalocaris; a streamlined body, a small head with ovoid sclerites, well-developed swimming flaps, and a pair of caudal furcae. Amplectobelua and Ramskoeldia have a pair of gnathobase-like structures,, while Lyrarapax and Guanshancaris have an oral cone with a tetraradial arrangement and scale-like nodes.
Classification
Early in 2014, "Anomalocaris" kunmingensis was tentatively assigned to Amplectobelua by Vinther et al. Later that year, however, the discoverers of Lyrarapax unguispinus ignored that assessment and created a genus within Amplectobelua sensu Vinther et al. An indeterminate frontal appendage assignable to this group is known from the Parker Slate of Vermont.
Phylogeny
An a posteriori-weighted phylogenetic analysis in 2014 found the following relationships within the Amplectobeluidae:
References