So, the other day, was looking through one of my favorite older monographs "On Some Remarkable Forms of Animal Life...Researches on the Structure and Affinity of the Genus Brisinga" by George Ossian Sars, Professor of Zoology at the University of Christiania and came upon this cool older idea of Echinoderm Phylogeny (i.e., an evolutionary tree):
The phylogeny recounts some very early ideas about metazoan relationships originally developed by Ernst Haeckel and modified by Sars. The monograph was published in 1875. Darwin's ideas on evolution had only been around since 1859.
This particular monograph emphasized brisingid starfish, which look sorta like a weird mutant hybrid between a "normal" looking starfish, a crinoid, and a brittle star:
but what was NEAT and weird about Sars take on this animal's history?
The fundamentals of this phylogenetic idea was that the Echinodermata were formed by "Colony Forming Vermes" which was another way of saying "Let's take 5 or more of these"
have them all connect at the jaws, fusing into a 5+worm formation projecting outward and then literally TRANSFORM turn them into something kinda like this:
But Sars hypothesized that brisingids were essentially a separate and independent "step" between these "colony forming vermes" and starfish and other echinoderms...essentially a missing link to ALL echinoderm diversification!!
And that seems kinda reasonable..when you look at it...
I could easily see how this could be "spun" this into the ancestor of crinoids, ophiuroids, and asteroids+echinoids+holothuroids!
Especially since the general gist of the phylogeny from there is that echinoderms were given towards greater "concrescense" or centralization...So from independent worms coalescing to bigger, lumpier things.
So holothurians or sea cucumbers would be chief evidence of "concrescence"..especially with something like the armored and essentially sessile Psolus, which was seemingly even LESS pentameral than other cucumbers.
This is my next pitch to NSF. So don't go stealing it!