I was reading a piece by Melissa Hogenboom on the currently-recognised 35 different…well, let’s call them kinds of animals. A few years back I’d have been happy calling them phyla, but a phylum, like other rigid taxonomic ranks, is becoming unfashionable these days, as is the idea than all evolutionary trees fit neatly into same hierarchical categories. It’s a bit like how forms that want your postal address assume you have a state and ZIP code. (New Zealand has never has states, and when I was a kid there were no postcodes either.)
Nevertheless, the idea of fundamental difference in basic body plans is an interesting one; currently there are 35 different ways of being an animal. Some of these ways are enormously successful, others barely exist. There are over a million species of arthropods, 100,000 chordates (including us), 11,000 cnidarians, 1,200 ribbon worms, 100 comb jellies, 11 species of horseshoe worms, and a single kind of placozoan.
Most of these 35 groups contain just a few hundred species, or even fewer; the animal kingdom seems to have a “long tail”. In the literal sense, too, since the most common animal body plan is some kind of worm.
Hogenboom apparently had some difficulty preparing her story, particularly having to extract usable photographs from the one or two researchers working on some of the more obscure groups. I feel her pain. Still, when you’re the world expert on a family of tiny parasites that only live in squid kidneys, I doubt you have a press kit ready.