Palæos:		Lobopoda
INVERTEBRATES		Lobopoda Home

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Velvet worms, represented by a single surviving genus Peripatus with 70 species, possessing a soft chitinous exoskeleton and tracheae.  The embryonic development is identical to that of annelids and uniramious arthropods, and these creatures seem to represent a missing link between the two groups.  However, modern molecular phylogeny has shown that annelids and arthropods are not at all closely related (contrary to previous opinion), in which case (and contra to the arguments of Ernst Haeckel and many other Darwinists since) embryology is not necessarily a good aid to phylogeny. Conversely it has been suggested note that the Onychophora are actually modified arthropods, rather than the other way around.  Some Cambrian forms (the Microdictyoniida, which includes the fossil genera Ayshenia, Hallucigenia (spectacularly misinterpreted when first discovered, and by Gould in Wonderful Life), Microdictyonia, and Xenusion) have been placed in this group on the basis of superficial appearance, but the relationship is by no means certain.

In the last decade a more developed picture of Cambrian lobopod morphology has taken shape, due mainly to Ramsköld's work on the Chengjiang lagerstätte. In a recent write up, Ramsköld and Junyuan analyze the Cambrian lobopoda together with Recent Onychophora, and locate the extant onychophorans as ingroup Cambrian "lobopodians" on the basis of four synapomorphies.

<==o LOBOPODA [Onychophora sensu lato] (lobopods, velvet worms)
   `--o †MICRODICTYONIIDA (Cambrian Lobopods - paraphyletic)
      |-- †Hallucigenia
      |-- †Ayshenia
      |-- †Microdictyonia
      |-- †Xenusion
      `--o ONYCHOPHORA (velvet worms)
         |-- Peripatidae 
         `-- Peripatopsidae

Reference(s):

Parker, S. P. (ed.), 1982: Synopsis and classification of living organisms. Vols. 1 & 2 --McGrew-Hill Book Company

Edgecombe, ed. Arthropod Fossils and Phylogeny, chap. 3, "Cambrian Lobopodians: Morphology and Phylogeny" by Lars Ramsköld and Chen Junyuan

Ballard, J. W. O., G. J. Olsen, D. P. Faith, W. A. Odgers, D. M. Rowell, P. W. Atkinson. 1992. - Evidence from 12S Ribosomal RNA sequences that Onychophorans are modified Arthropods. Science 258:1345-1348.

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