INTRODUCTION & BIOLOGY
Unfair as it is to award some 50-million-year-old clades with barely 100 species with individual attention while relegating clades that are over half a billion years old and comprise many thousands of species to a couple of paragraphs, vertebrates (in particular, dinosaurs) are the focus of this site. In any case, echinoderms are another group that does not vary much from timeline to timeline.
There are some observable difference, however. In our home timeline, the echinoderm lineages of starfish (asteroids) and brittle-stars (ophiuroids) were seriously reduced, for a while, by the K-Pg event, and sea-cucumbers (holothuroids) did rather well throughout. In Spec, the lack of the impact event allowed many of these groups to survive to the present day.
The confusingly-named asteroids (more commonly called sea-stars or starfish) are benthic crawlers, with five pneumatic limbs, capable of exerting tremendous force on their prey. Most of Spec's sea-stars are fairly similar to their Home-Earth counterparts, but a few of this timeline's pre-Cretaceous lineages have evolved into some novel forms, including giant sea-floor scavengers.
Darthaster (Darthaster jonesi)
The darthaster (Darthaster jonesi) is a giant (often over a metre in diameter) sea-star that stalks slowly across the deep sea mud feeding on detritus.
Sea-cucumbers are present in Spec, and in great numbers, but for some reason these sack-like echinoderms have not fully exploited the bottom-feeding niches familiar to our timeline. Rather, the asteroids dominate the sea floor while the holothuroideans have explored a number of novel lifestyles.
Umbrella Cucumbers (Parapelagothuria sp.)
The umbrella cucumbers (Parapelagothuria) are an excellent example of the many free-swimming sea-cucumbers that abound in the deeper reaches of Spec's mysterious oceans. Almost jellylike in texture, the umbrella cucumbers drift above the deep ocean floor and catch the organic fragments that fall from the ocean surface far above. This particular species is known to bioluminesce spectacularly when disturbed by a predator, passing ktulu, or curious submersibles.
Rock-Sock (Chiantithuria timorensis)
The rock-sock (Chiantithuria timorensis) is a burrowing sea-cucumber species adapted to root itself deep beneath muddy sand, and extend its feeding tentacles, mouth, and anus up to the surface at the end of long retractable 'neck'. This particular species was discovered living in the shallow waters off the western coast of Australia.
There are some superficial resemblances between genus Chiantithuria and Home-Earth sea-cucumbers, but the form of the ossicles that support its leathery skin suggest it is more closely related to species that are known only from these ossicles, that in our world vanished with the passing of the Cretaceous.