The discovery of new animals with a unique body plan complicates phylogenetic hypotheses still further.
In 1986, oceanographers collected some unusual organisms from the deep (400–1000 m) seafloor off the coast of Tasmania. Described in 2014 as the new genus Dendrogramma, these are diploblastic animals only a few millimeters long, with a mushroomlike appearance: a disc connected to a stalk (Fig. 44.14). The stalk bears a mouthlike opening at its end, connected by a tubular passageway to a highly branched series of canals in the disc that are thought to function in digestion and, perhaps, circulation.
FIG. 44.14 Dendrogramma enigmatica. Reported for the first time in 2014, this is a diploblastic animal that is not easily placed within any existing phylum.
The animals exhibit some characters that resemble cnidarians and others that resemble ctenophores, but features that might place them unequivocally in either phylum are absent. Unfortunately, DNA appears not to have been preserved in the animals collected and so molecular sequencing cannot at present be used to place Dendrogramma on the animal tree. These animals may be aberrant members of known diploblastic phyla, or—just maybe—they represent a new phylum that will change our view of early branches on the animal tree.