Panarthropoda

Panarthropoda Temporal range: Cambrian - Recent PreꞒ Ꞓ O S D C P T J K Pg N Molecular clock and ichnofossils indicate a possible Ediacaran origin[1] [2]
Panarthropods include onychophorans such as Peripatopsis and arthropods such as polydesmid millipedes
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Nephrozoa
(unranked):	Protostomia
Superphylum:	Ecdysozoa
(unranked):	Panarthropoda Nielsen, 1995
Phyla
†" paraphyletic ) Onychophora Tardigrada Arthropoda

Panarthropoda is a proposed

Interrelationship

Panarthropoda (Lobopodian taxa controversial)* (Lobopodian taxa controversial)* Antennacanthopodia * Crown-group Onychophora (Lobopodian taxa controversial)* Crown-group Tardigrada Siberiid lobopodians * Gilled lobopodians * Opabinia Radiodonta Euarthropoda

Summarized interrelationship of Panarthropoda, with focus on phylogeny between lobopodians (asterisk) and extant panarthropods (bold). Relationship between the total-group of extant panarthropods is unresolve (see text for discussion).[5][6]

There are three competing hyphotheses for the interrelationship between the extant panarthropod phyla, each known as Tactopoda (Arthropoda+Tardigrada), Antennopoda (Arthropoda+Onychophora), and the sister relationship between Onychophora and Tardigrada (Lobopodia sensu Smith & Goldstein 2017).^[22]

Tactopoda had been supported by

• 
  Anatomy of

  onychophoran

  anterior region, showing specialized appendages (ant, md) and deutocerebrum (D).
• 
  Nervous system of a tardigrade, showing ventral nerve cord with segmented ganglia (ga1-4).
• 
  remipede arthropod

  , showing the presence of both deutocerebrum (dc) and ventral nerve cord (vnc) organized by segmented ganglia.

Within extinct lobopodians, at least Antennacanthopodia are widely accepted as part of the onychophoran stem-group.^{[28][4][29][30][31][27][32][33][6][34][35]} On the other hand, siberiids (Siberion, Megadictyon and Jianshanopodia) and gilled lobopodians (Pambdelurion and Kerygmachela) represent transitional forms between typical lobopodians and basal arthropods (e.g. Opabinia and Radiodonta).^{[28][4][29][30][31][27][32][5][6][33][34][7][8][35][36][9]} The positions of most other lobopodians (e.g. Hallucigenia and luolishaniids as stem onychophorans^{[4][29][30][31][27][32][35]} or stem panarthropods^[33][34][36]), including the lobopodian members of tardigrade stem-group (represented by Onychodictyon ferox^{[4][29][30][31][27][32][35]} or Aysheaia^[33][34][36]) are more controversial.

Sialomorpha, a genus of microinvertebrate discovered in Dominican amber in 2019, is also considered to be a panarthropod. However, due to the unusual combination of tardigrade and mite-like characteristics, its exact placement is uncertain.^[37]

See also

• List of bilaterial animal orders

References