Palaeos		Panarthropoda
Ecdysozoa		Overview

Ecdysozoa: Panarthropoda

ECDYSOZOA
|==SCALIDOPHORA
`--+--NEMATOIDA
   |
   `--PANARTHROPODA
      |--Aysheaia
      `--+--TARDIGRADA
          `--+--Xenusiidae
             |--ONYCHOPHORA
             `--+--Luolishaniidae
                `--+==Siberiidae
                   `--+==DINOCARIDIDA
                      `--ARTHROPODA

A selection of Cambrian lobopodians and protoarthropods; "non-missing links" between worms and arthropods. Clockwise from upper left, Anomalocaris, Aysheaia, Opabinia. and Kerygmachela. Artwork by Renato de Carvalho Ferreira via Wikipedia. Creative Commons Attribution-Share Alike

In this and the following several units we consider one of those fascinating instances of evolution, the transition from one body type; in this case, the soft-bodied ancestral worm; to a radically different type, the armoured and jointed skinned arthropod. Like the evolution of vascular land plants from green algae, brachiopods, annelids and molluscs from earliest Cambrian "coat of mail" ancestors, vertebrates from early deuterostomes, amphibians from fish, birds from dinosaurs, and mammals from reptiles, this is one of those extraordinary stories well documented through a convergence of the fossil record, comparative morphology (of both extinct and extant forms), and molecular phylogeny. It was also one of the most dramatic aspects of the Cambrian explosion, as the lobopodians and protoarthropods that resulted from this burst of evolutionary creativity were among the most spectacular creatures of their time; cruising superpreditors, five eyed aliens, and walking catuses are among some of the strange players of this evolutionary drama. For now our coverage is still rather scanty, but it is hoped that this can be adressed in future. MAK120419