Acariformes | |
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Trombidium holosericeum (Trombidiformes: Trombidiidae) |
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Scientific classification | |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Subphylum: | Chelicerata |
Class: | Arachnida |
Subclass: | Acari |
Superorder: |
Acariformes Zakhvatkin, 1952 |
Clades and orders | |
The Acariformes are the more diverse of the two superorders of mites. Over 32,000 described species are found in 351 families, and an estimated total of 440,000 to 929,000 species occur, including undescribed species.
The Acariformes can be divided into two main clades - Sarcoptiformes and Trombidiformes. In addition, a paraphyletic group containing primitive forms, the Endeostigmata, was formerly also considered distinct. The latter is composed of only 10 families of little-studied, minute, soft-bodied mites that ingest solid food, such as fungi, algae, and soft-bodied invertebrates such as nematodes, rotifers, and tardigrades. These clades were formerly considered suborders, but this does not allow for a sufficiently precise classification of the mites and is abolished in more modern treatments; the Endeostigmata are variously considered to form a suborder on their own (the old view) or are included mainly in the Sarcoptiformes, thus making both groups monophyletic.
Another group often mentioned is the Actinedida, but in treatments like the present one, this is split up between the Sarcoptiformes (and formerly the separate Endostigmata) and Trombidiformes (which contains the bulk of the "Actinedida"), because it appears to be a massively paraphyletic "wastebin taxon", uniting all Acariformes that are not "typical" Oribatida and Astigmatina. The Trombidiformes present their own problems. The small group Sphaerolichida appears to be the most ancient lineage among them. However, the Prostigmata are variously subdivided into the Anystina and Eleutherengona, and Eupodina. The delimitation and interrelationships of these groups are entirely unclear; while most analyses find one of the latter two, but not the other to be a subgroup of the Anystina; neither of these mutually contradicting hypotheses is very robust; possibly this is a simple error because phylogenetic software usually fails in handling nondichotomous phylogenies. Consequently, it may be best for the time being to consider each of the three main prostigmatan lineages to be equally distinct from the other two.