Dendrogramma, a strange new genus

A recent paper in PLoS ONE (by Jean Just, Reinhardt Møbjerg Kristensen, and Jørgen Olesen) reports the new species Dendrogramma discoides (marked with asterisks in the image from the paper above) and Dendrogramma enigmatica (unmarked above). These species were found in waters off south-east Australia.

Specimens from this new genus were collected in 1986, and preserved in formaldehyde. This is a pity, because the organisms have not been found again, and the formaldehyde has destroyed their DNA.

DNA analysis would have been useful to work out in which animal phylum to place Dendrogramma. The usual candidates (left to right above) are Porifera (sponges), Ctenophora (comb jellies), Cnidaria (jellyfish), and the Bilateria – such as Echinodermata (which are bilaterally symmetrical as larvae) or Chordata.

The fascinating Dendrogramma specimens are not bilaterally symmetrical, and are not sponges. They lack specialised features of the Ctenophora and Cnidaria, such as Cnidarian stinging cells. So what are they? It seems likely that either a new phylum has to be defined; or that Dendrogramma must be placed in a restored Coelenterata (a former phylum which once contained the Ctenophora and Cnidaria); or that the boundaries of Ctenophora or Cnidaria need to be extended – but without DNA, the decision is difficult.

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One thought on “Dendrogramma, a strange new genus

  1. Pingback: 2014 in review | Scientific Gems

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