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
Jaliscan spiny pocket mouse species to the interior. Jaliscan spiny pocket mouse The Jaliscan spiny pocket mouse ("Heteromys spectabilis") is a species of heteromyid rodent endemic to Mexico. The specific name "spectabilis" means "striking", and refers to the animal's relatively bright coloration. It was formerly placed in the genus "Liomys", which is now recognized to be paraphyletic and has been subsumed into "Heteromys". The Jaliscan spiny pocket mouse is a relatively large member of its genus, measuring in head-body length, with a tail about the same length again. Adult males weigh about on average, while females are significantly smaller, weighing on average. The fur