Threatened arthropods and described. The total number of living arthropod species is probably in the tens of millions. One conservative estimate puts the number of arthropod species in tropical forests alone at six to nine million species. As a consequence of all of the above, most published estimates of the total number of endangered insects and arachnids are probably low by at least an order of magnitude. Conservatively at least eighty percent of all living animal species are arthropods. Since arthropods constitute the majority of the faunal biomass on Earth, their role is vital to the survival of large numbers of insectivores
Kosher animals (which, like the other ruminant even-toed ungulates, is apparently 'without upper teeth' though some citations.), even though the skulls clearly have both front and rear upper teeth. The Talmud also argues that the meat from the legs of clean animals can be torn lengthwise as well as across, unlike that of unclean animals, thus aiding to identify the status of meat from uncertain origin. Biblical scholars believe that the classification of animals was created to explain pre-existing taboos. Beginning with the Saadia Gaon, several Jewish commentators started to explain these taboos rationalistically; Said himself expresses an argument similar to that