Ecdysozoa Classification

Dinocaridida: Classification

Abbreviated Dendrogram
Panarthropoda ╘═Siberiidae │ └─Dinocaridida ├─Kerygmachela └─┬─Pambdelurion └─┬─Opabinia └─┬─Anomalocarididae │ ├─Hurdia │ └─┬─Anomalocaris │ └─Laggania └─┬─Schinderhannes └─Arthropoda

Dinocaridida (1)
Dinocaridida (2)
Anomalocarididae (1)
Anomalocarididae (2)

There does not seem to be a current evolutionary-linnaean taxonomy for the Dinocaridids, and that classification as there is about a decade out of date. The following is offered as a provisional arrangement, until something better comes along MAK120507

Superphylum Ecdysozoa Aguinaldo et al. 1997 (cont.) Phylum Lobopodia Snodgrass, 1938 (cont.) or Arthropoda Subphylum Protarthropoda Lankester, 1904 Class Dinocaridida Collins 1996 (monotypal - Order Radiodonta) Orders and families unspecified: the basal dinocaridids (Kerygmachela & Pambdelurion, probably each deserve a monotypal family, E Cam of Greenland) Order Opabiniida Størmer 1944 (currently monotypal, Opabinia regalis Walcott 1912 only, M Cam of Nth Am) Family Opabiniidae Walcott 1912 Order Radiodonta Collins 1996 Family Anomalocarididae Raymond 1935 (nektonic apex preditors; Cam to Dev, Cosm. ) Subfamily Anomalocaridinae (Anomalocaris & co; Cam to E Ord, Cosm. ) Subfamilies unspecified (Schinderhannes, Parapeytoia, and other forms more advanced to the arthropod condition than standard Anomalocarididae, Camb to Dev)


Such is their status as transitional forms that dinocaridids can equally be considered highly arthropod-like lobopodians or stem arthropods. Although there is a tendency to consider more primitive forms like Kerygmachela as lobopod and more derived froms like Anomalocaris as arthropods, this creates an artificial distinction between a grade of very similar animals (Kerygmachela's only really distinctive primitive feature here is the centrally located, xenusian-like mouth) MAK120503

Regardless of which phylum they are included in, we believe that Dinocaridids are distinct enough (as transitional forms) to deserve their own subphylum MAK120503

As defined by Collins, Dinocarids are bilaterally symmetrical arthropods with a body divided into two principal tagmata, recalling the prosoma and opisthosoma of chelicerates, and a non-mineralised cuticle. The front part shows no external segmentation, bears one or more pre-oral claws, one or more pairs of prominent eyes, and a ventral mouth; differing from other arthropod classes in possessing no antennae and only one appendage or pair of pre-oral appendages on the prosoma, and in bearing gilled lateral lobes on the metameric trunk. The jaws vary from none to forms with both radiating teeth and teeth in rows. - Chris Clowes..

Collins (1996, p. 291) restricted the Radiodonta to exclude the Opabiniidae and, although these genera were not described at the time, certainly he would have excluded Kerygmachela and Pambdelurion also. These two taxa are highly problematic, being known from a single locality, the Sirius Passet location in northeastern Greenland, and occupying an uncertain position intermediate between the onychophorans, anomalocaridids, and euarthropods. Graham Budd, who described both taxa, interprets them to imply that at least the biramous arthropods actually arose from within the anomalocaridids, the biramous limb having evolved before full cuticular sclerotisation. - Chris Clowes..

We have here made an arbritrary distinction between mainstream anomalocaridids, which constitute a mostly Cambrian monophyletic clade, and more advanced and derived forms. MAK120503

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