The reef glider is a massive, omnivorous nudibranch from the Shallow Seas in 100 million AD, in The Future is Wild.
The large form of a reef glider can often be seen sweeping through the water, silhouetted against the bright surface and throwing its shadow across a red alga reef. From its bulbous, teardrop-shaped body protrude three pairs of paddles. A long bunch of streamer-like filaments trails behind. It is difficult to believe that this is a variety of nudibranch, bigger than any of its relatives. During previous times, they were unflatteringly called sea slugs but, despite their ugly common name, they have been dainty-looking creatures, colorful and elegant, their gills forming fernlike arrays on their backs.
100 million AD, nudibranchs have evolved into substantial animals, with adult reef gliders growing to the size of seals. Like their ancestral relatives, they are brightly colored, their gills flowing behind them in a long train of silky fibrous plumes, like the tail of certain birds of paradise. The reef glider's head sports a pattern of bumpy, scent-detecting chemical receptors, called rhinophores, and groups of eye Reef gliders mounted on stalks. It has a horny, beaklike mouth. Unlike its relatives, the reef glider no longer relies on simply crawling across a reef by expanding and contracting its body. It has developed paddles, which are fleshy extensions of its invertebrate body. Each pair beats in turn, propelling the animal slowly through the water.