(Picture by Drhoz)
        In the Home-Earth timeline, the echinoderm lineages of starfish (asteroids) and brittle-stars (ophioroids) were seriously reduced, for a while, by the K-T event, and sea-cucumbers (holothurians) did rather well throughout. In part, this was due to the severe sea-level changes that were happening at the time, unrelated to the Chixalub event, causing the extinction of the prefentially shallow-water starfish and various specialised feeders. In Spec-world, the lack of the added destruction caused by the impact and eruptions and tsunamis and 'nuclear winter' etc, allowed many of these groups to survive the transition to the present day.

    A number of specialised sea-urchin groups survived well into the Tertiary, but most suffered the same fate as the Stromatoporata (reef-building sponges, which went extinct during the sea-level changes of the Cenozoic) in later extinction events.

    Some asteroids (sea stars) have gradually invaded a number of holothurian niches and the sea-cucumbers, whilst still dominating the deepest parts of the ocean despite, the asteroid invasion, have specialised into a larger number of gelatinous, pelagic and sessile, filter-feeding genera. No species have moved into freshwater or terrestrial habitats---a relief for marine biologists already startled by the giant balaenatheuthians, ktulus, freshwater ammonites, and death penguins.

    However, one undescribed species of brittle-star (similar to the Home-earth Ophiomastix annulosa) has been reported as causing paralysis in humans, after careless handling. It's suspected the venom, normally used to kill the small fish and crustaceans that are the ophioroid's normal prey, is also by chance highly poisonous to primates.

(Text by Drhoz)
    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 RL.  Rather, the asteroids dominate the sea floor while the holothuroideans have explored a number of novel lifestyles.
(Text by Daniel Bensen)
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