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 (), meaning "hair". "Lonchothrix" is a member of the Echimyini clade of arboreal Echimyidae rodents. The closest relative of "Lonchothrix" is "Mesomys", reflecting the fact that these taxa have once been classified in the same subfamily (Eumysopinae). These two genera share phylogenetic affinities with several taxa and clades: (i) "Echimys", "Phyllomys", "Makalata", "Pattonomys", and "Toromys" ; (ii) the bamboo rats "Dactylomys", "Olallamys", "Kannabateomys" together with "Diplomys" and "Santamartamys" ; and (iii) "Isothrix". 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,