Starfish first appeared in the fossil record in the Cambrian. The first known asterozoans were the Somasteroidea, which exhibit characteristics of both groups. Starfish are infrequently found as fossils, possibly because their hard skeletal components separate as the animal decays. Despite this, there are a few places where accumulations of complete skeletal structures occur, fossilized in place in Lagerstätten — so-called "starfish beds". By the late Paleozoic, the crinoids and blastoids were the predominant echinoderms, and some limestones from this period are made almost entirely from fragments from these groups. In the two major extinction events that occurred during the late
Eastern spiny mouse species is nocturnal, avoiding the heat of the day and foraging at night for seeds, and sometimes insects and grasses. It is a sociable animal and lives in small groups. Females become mature at about two months of age and can produce litters of up to five young after a gestation period of about 42 days. Another female in the family group may help with care of the young, which are weaned after about a fortnight. Its spiny hair may help to prevent predation, perhaps making the animal harder to swallow, and this mouse is also capable of shedding its