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
Cairo spiny mouse Cairo spiny mouse The Cairo spiny mouse ("Acomys cahirinus"), also known as the common spiny mouse, Egyptian spiny mouse, or Arabian spiny mouse, is a nocturnal species of rodent in the family Muridae. It is found in Africa north of the Sahara, where its natural habitats are rocky areas and hot deserts. It is omnivorous and feeds on seeds, desert plants, snails, and insects. It is a gregarious animal and lives in small family groups. The Cairo spiny mouse grows to a head and body length of about with a tail of much the same length. Adults weigh between .