cnidaria

A few other fun ones are Cnidaria and Ctenophora (both phyla containing some varieties of jellyfish) where in both cases the c is silent.

Maybe the first animal with nervous system (a common ancestor of Cnidaria and Bilateria) was the first to have a sleep-wake cycle.

Out of the 3.5 billion years that the planet has sustained life, animals (first sponges, then cnidaria, etc.) have only been around for 630 million.

By the way, even Cnidaria (jellyfish etc) exhibit sleep-wake cycles [1].

Well, other than Cnidaria but who counts them anyways.

At a tender age of 20, were you sir a Johns Hopkins Biology student faced with an essay question in a final exam about the types of reproduction in the Cnidaria phylum?

What's fascinating is that finding new animal phyla is apparently something that has happened a few times in the last century, and they aren't able to place this creature into a phyla yet - it's close to a jellyfish and comb jellies, but not close enough to be included in the Cnidaria or Ctenophora phylum.

> they don't have blood at all Then that would be an evolutionary in-spec configuration, since Cnidaria-phylum species have evolved under selection pressure for hundreds of millions of years in that "never losing blood, because it doesn't have any" configuration.

Cnidaria are an interesting comparison, because they are radially symmetric but not members of Bilateria.

They're both in the phylum Cnidaria, and that would have been a more vague term had I entered it.

They're in the phylum Cnidaria, which includes the likes of jellyfish and anenomes.