The Siberian tardigrade fossils differ from living tardigrades in several ways. A few small animals (nematodes, tardigrades, and rotifers) live in the river. Tardigrades and extremophiles were also sent into orbit. Microscopic adult marine crustaceans include some copepods, cladocera and tardigrades (water bears). Tardigrades are often found on lichens and mosses. This category includes tardigrades, arthropods, molluscs, and numerous types of worms. In 2014, research indicated that tardigrades were more closely related to arthropods than velvet worms. Tardigrades work as pioneer species by inhabiting new developing environments. The experiment studies the effects of tardigrades in a microgravity environment. Tardigrades have survived all five mass extinctions. Acclimation boosted the temperature needed to kill half of active tardigrades to . Tardigrades are oviparous, and fertilization is usually external. Tardigrades in the tun state fared a bit better, tolerating higher temperatures. A preliminary investigation of Zubarah uncovered four previously unknown species of tardigrades. Eutardigrada are a class of tardigrades (Tardigrada) without lateral appendices.