Deuteropoda or "upper stem group arthropods" is a proposed
clade of
arthropods whose members are distinguished by an anatomical reorganization of the head region, namely the appearance of a differentiated first appendage pair (the '
deutocerebral' pair), a multisegmented head, and a
hypostome/
labrum complex.
The clade contains all living
arthropods (i.e.
chelicerates
The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mite ...
and
mandibulates) as well as several fossil groups that share these characteristics (e.g.
fuxianhuiids,
megacheirans and
Artiopoda
The Artiopoda is a grouping of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilo ...
), while excluding other fossil groups that are more 'basal' or 'primitive' (e.g.
anomalocarids and
lobopodians).
Defining characteristics
Members of Deuteropoda are characterized by the presence of a differentiated
labrum and a differentiated first '
deutocerebral' pair of appendages.
In contrast, lobopodians (part of the "lower stem group") and
onychophorans have a pair of pre-ocular or '
protocerebral' appendages, which presumably have evolved to be the
labrum of modern living arthropods.
Phylogeny
The cladogram below is a simplified summary of the
panarthropod
Panarthropoda is a proposed animal clade containing the extant phyla Arthropoda, Tardigrada (water bears) and Onychophora (velvet worms). Panarthropods also include extinct marine legged worms known as lobopodians ("Lobopodia"), a paraphylet ...
phylogeny, taking into account the differentiation between "lower stem group arthropods" and "upper stem group arthropods" as well as two new fossils found to be the most early branches of Deuteropoda
(living groups are marked in bold).
References
{{Reflist
Unranked clades
Arthropods