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
Tuft-tailed spiny tree-rat Tuft-tailed spiny tree-rat The tuft-tailed spiny tree rat ("Lonchothrix emiliae") is a spiny rat species from South America. It is known from Brazil south of the Amazon River, where it has been found in grassland and gallery forest. It is the only species in the genus Lonchothrix. Very little is known about this rodent. It is small with an average adult weight of about 138 grams. It is nocturnal and solitary in habits. The genus and species were described by Oldfield Thomas in 1920. The genus name "Lonchothrix" derives from the two ancient greek words (), meaning "spear", and ,