Over the past few years, studies of genomes have confused what we thought we knew about the origin of animal life. Instead of the simple sponges being the earliest branch off the animal tree, a group of relatively complex organisms, the ctenophores, seem to be the earliest branch. That finding has some serious implications, as it suggests that a nervous system evolved twice.

Now, some more traditional biology may upset the family tree even further. Old samples taken from the seabed near Tasmania contain examples of two different species that may belong to a phylum entirely unknown to us—one that split off near the base of the animal tree. The strange creatures also have features that suggest they may be related to remains from the Ediacaran, a period in which the first animal life appears in the fossil record.

The samples actually date from a research cruise taken nearly 30 years ago, where a "sled" was dragged along the ocean floor and samples returned to the surface. The new species weren't recognized as interesting when they were first found, so they were left mixed in with the rest of the collection, which was fixed with formaldehyde and then dumped in 80 percent ethanol. The samples suffered a bit of further abuse when one of the authors wanted to refresh the alcohol and was given 100 percent ethanol instead. (The paper actually notes, "Unfortunately absolute alcohol was provided without comment instead of the requested 80 percent ethanol.")

Despite all the time and abuse, however, it eventually became clear that the organisms were rather distinctive. Superficially, they look like mushrooms, but they are clearly not fungi. One reason that's obvious is because the base of the stalk has a mouth. The mouth (which doubles as an anus) opens up into a digestive cavity that extends up into the disk-like cap of the mushroom shape. There, the cavity fans out into a series of tubes that ensure all areas of the animal have access to nutrients—the authors call this a "gastrovascular system."

The organism clearly has three layers of cells: an external layer, an internal layer of cells, and another layer that lines the gastrovascular system. In this, it appears somewhat similar to both the ctenophores and another group called cnidarians, which include the jellyfish. But it lacks a long list of features from both of those groups. It doesn't have any cnidocytes, tentacles, a ring canal, or sense organs like the jellyfish, and it lacks cilia and organs found in ctenophores.

Jellyfish and ctenophores are notable for being radially symmetric. On some level, these new creatures are as well. But the mouth has a top and bottom, and one species has a notch out of a single location in its disk, suggesting that there are also "sides" present as it develops (whether they're left and right, top and bottom, or something else entirely isn't clear).

As a result, the authors assign the two species their own family, Dendrogrammatidae, after the branching pattern of the gastrovascular system. But this was a case where the peer reviewers (who often ask authors to tone down dramatic claims) thought they were being too cautious: "It has been suggested during review that Dendrogramma could represent a new non-bilaterian phylum. While we may agree, we refrain from erecting such a high-level taxon for the time being." (A phylum is the second highest level grouping of species, just below kingdom.)

The species are placed in the only genus of the family, Dendrogramma. One is named D. discoides after its disk, and the second D. enigmatica because, "This species has been and still is a great enigma."

What to make of all this? The authors aren't sure where to place these creatures relative to the other early branches of the animal tree, although they conclude they must have split off before bilaterians (animals with two sides, like insects and us). But they look equally similar to both jellyfish and ctenophores, which seem to be relatively distantly related.

Unfortunately, decades in ethanol will have killed any chance to look at the DNA of these organisms or to examine the expression of any proteins. Our best bet to clarify what these organism are will rely on obtaining new samples. A second cruise, performed in the same area in 1988, didn't find any, so this may not be a simple hurdle to clear.

However, the authors note that there may be some relatives we know from the fossil record. Most of the animal forms we're familiar with date back to what's called the Cambrian, which started about 540 million years ago. But the earliest animals appear before that, in a period called the Ediacaran. These organisms bear few similarities to any of the groups that thrived in the Cambrian and often appear to be a bizarre collection of fronds and branches.

But the authors say there's a group with the fantastic name trilobozoid medusoids, and this group looks vaguely similar to the new species. Those disappeared from the fossil record after the Ediacaran, but they'd puzzled paleontologists, some of whom put them in their own kingdom called the Vendozoa. There's no way to tell if these are related to the modern-day Dendrogrammatidae, but it's possible that the fossil record was revealing some of the earliest branches of the animal family tree.

PLoS one, 2014. DOI: 10.1371/journal.pone.0102976 (About DOIs).