Panarthropoda

 ( Extant Cambrian First Appearances ) 

Tactopoda had been supported by mitochondrial gene arrangements, palaeontological and neuroanatomical evidences, specifically the presence of segmented ganglia shared by arthropods and tardigrades. Antennopodia united by the presence of specialized head appendages and deutocerebrum (additional second section of the brain), but subsequent anatomical studies suggest these features were convergently evolved between onychophoran and arthropod lineages. Onychophorans and tardigrades shared some lobopodian traits (e.g. soft cuticle, lobopodous appendages and peripheral nerve roots), but these were generally considered to be plesiomorphies traced back to the last common ancestor of Panarthropoda or Ecdysozoa. While most phylogenomic analyses support the monophyly of Panarthropoda, the results of interrelationship between the three phyla are less correlated—some of them inconsistently placing Tardigrada within Arthropoda, while the others mostly recovering either Antennopoda or Onychophora+Tardigrada. A study published in December 2024 supported the sister relationship of Onychophora and Arthropoda.

File:Britannica 1911 Arthropoda - Peripatus head.png|Anatomy of onychophoran anterior region, showing specialized appendages (ant, md) and deutocerebrum (D) File:Tardigrade zenuw.jpg|Nervous system of a tardigrade, showing ventral nerve cord with segmented ganglia (ga1-4) File:20200213 Remipedia Nectiopoda central nervous system.png|Nervous system of a remipede arthropod, showing the presence of both deutocerebrum (dc) and ventral nerve cord (vnc) organized by segmented ganglia

The "Lobopodia" are paraphyletic; they include the last common ancestor of arthropods, onychophorans and tardigrades.

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.

• List of bilaterial animal orders