Kosher animals

Kosher animals are animals that comply with the regulations of kashrut and are considered kosher foods. These dietary laws ultimately derive from various passages in the Torah with various modifications, additions and clarifications added to these rules by halakha. Various other animal-related rules are contained in the 613 commandments.
Image:Schect.jpg|thumb|A 15th-century depiction of ''shechita''

Land animals

and both give the same general set of rules for identifying which land animals are ritually clean. According to these, any animal which "chews the cud" and has a completely split hoof is ritually clean, but those which only chew the cud or only have cloven hooves are unclean.
Both documents explicitly list four animals as being ritually impure:

The camel, for chewing the cud without its hooves being divided.
The hyrax, for chewing the cud without having cloven hooves; as the hyrax was not known to early English translators, the Hebrew term for this animal, שפן, has been interpreted in older English versions of the Bible as coney, a name with clear connections to words such as the Spanish conejo. The actual coney was an exclusively European lagomorph, and not present in Canaan; hyraxes, however, are still found in Southern and Eastern Africa, the Levant and Arabian Peninsula, with the shapan in the Book of Proverbs described as having lived on rocks. Despite their rabbit- or rodent-like appearance, hyraxes are actually one of the closest living relatives of elephants, still possessing "tusk"-like teeth—as opposed to the ever-growing, gnawing teeth of rodents or lagomorphs. Additionally, their feet do not have the small claws and digits of rodents or lagomorphs, instead resembling miniature elephant-feet, with toenails specially adapted for climbing rocks.
The hare, for chewing the cud without having cloven hooves.
The pig, for having cloven hooves without chewing the cud.

While camels possess a single stomach, and are thus not true ruminants, they do chew cud; additionally, camels do not have hooves at all, but rather separate toes on individual toe pads, with hoof-like toenails.
Although hares and other lagomorphs do not ruminate at all, they do typically re-ingest soft cecal pellets made of chewed plant material immediately after excretion for further bacterial digestion in their stomach, which serves the same purpose as rumination. They are also known to ingest their own and the droppings of other lagomorphs for nutritive reasons.
Although not ruminants, hyraxes have complex, multichambered stomachs that allow symbiotic bacteria to break-down tough plant materials, though they do not regurgitate it for re-chewing. Further clarification of this classification has been attempted by various authors, most recently by Rabbi Natan Slifkin, in a book, entitled The Camel, the Hare, and the Hyrax.
Unlike Leviticus 11:3-8, Deuteronomy 14:4-8 also explicitly names 10 animals considered ritually clean:

The ox
The sheep
The goat
The deer
The gazelle
The yahmur; this term, directly taken from the Masoretic Text, is used in modern Hebrew to refer to the fallow deer, while in Arabic it refers to the roe deer. Scholarship identifications of the biblical animal include, in addition to the fallow deer and roe deer, also the hartebeest, based on the Vulgate, which renders it as bubalum.
The the'o; this term, directly taken from the Masoretic Text, has traditionally been translated ambiguously.
The pygarg; the identity of this animal is uncertain, and pygarg is merely the Septuagint's rendering. The Masoretic Text calls it a dishon, meaning springing; it has thus usually been interpreted as some form of antelope or ibex. Specifically, Amar et al. interpret dishon as Arabian oryx.
The antelope
The camelopardalis; the identity of this animal is uncertain, and "camelopardalis" is merely the Septuagint's wording. The Masoretic Text calls it a zamer, but camelopardalis means camel-leopard and typically refers to the giraffe ; in taxonomy, several types of giraffes are placed under Giraffa camelopardalis. The traditional translation has been for the chamois, an alpine goat-antelope of Europe and parts of Asia Minor, but it has never naturally existed in Canaan; neither is the giraffe naturally found in Canaan. Consequently, the wild sheep ancestor, the mouflon, is considered the best remaining identification, despite not being related to the term "camel-leopard".

The Deuteronomic passages mention no further land beasts as being clean or unclean, seemingly suggesting that the status of the remaining land beasts can be extrapolated from the given rules.
By contrast, the Levitical rules later go on to add that all quadrupeds with paws should be considered ritually unclean, something not explicitly stated by the Deuteronomic passages.
The Leviticus passages thus cover all the large land animals that naturally live in Canaan, except for primates, and equids, which are not mentioned in Leviticus as being either ritually clean or unclean, despite their importance in warfare and society, and their mention elsewhere in Leviticus.
In an attempt to help identify animals of ambiguous appearance, the Talmud, in a similar manner to Aristotle's earlier Historia Animalium, argued that animals without upper teeth would always chew the cud and have split hoofs, and that no animal with upper teeth would do so; the Talmud makes an exception for the case of the camel, 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.

Origin

Many Biblical scholars believe that the classification of animals was created to explain pre-existing taboos. Beginning with Saadia Gaon, several Jewish commentators started to explain these taboos rationalistically; Saadia himself expresses an argument similar to that of totemism, that the unclean animals were declared so because they were worshipped by other cultures. Due to comparatively recent discoveries about the cultures adjacent to the Israelites, it has become possible to investigate whether such principles could underlie some of the food laws.
Egyptian priests would only eat the meat of even-toed ungulates, and rhinoceros. Like the Egyptian priests, Vedic India allowed the meat of rhinoceros and certain ruminants, although cattle were likely excluded as they were seemingly taboo in Vedic India; in a particular parallel with the Israelite list, Vedic India explicitly forbade the consumption of camelids and domestic pigs. However, unlike the biblical rules, Vedic India did allow the consumption of hare and porcupine, but Harran did not, and was even more similar to the Israelite regulations, allowing all ruminants and expressly forbidding the meat of camels.
It is also possible to find an ecological explanation for these rules. If one believes that religious customs are at least partly explained by the ecological conditions in which a religion evolves, then this too could account for the origin of these rules.

Modern practices

In addition to meeting the restrictions as defined by the Torah, there is also the issue of masorah. In general, animals are eaten only if there is a masorah that has been passed down from generations ago that clearly indicates that these animals are acceptable. For instance, there was considerable debate as to the kosher status of zebu and bison among the rabbinical authorities when they first became known and available for consumption; the Orthodox Union permits bison, as can be attested to by the menus of some of the more upscale kosher restaurants in New York City.

Water creatures

and both state that anything residing in "the waters" is ritually clean if it has both fins and scales, in contrast to anything residing in the waters with neither fins nor scales. The latter class of animals is described as ritually impure by Deuteronomy, Leviticus describes them as an "abomination" KJV Leviticus 11:10. Abomination is also sometimes used to translate and.
Although the Tanakh does not further specify, the Talmud makes the claim that all fish that have scales also have fins, and so practically speaking, we need to only identify organisms that have scales and can ignore the portion of the rule about fins. Nachmanides comments that the scales of a kosher fish must be able to be removed either by hand or by knife, but that the underlying skin does not become damaged with removal of the scales, and this opinion had been universally accepted by all halachic authorities at the time.
Scientifically, there are five different types of fish scales: placoid, cosmoid, ganoid, ctenoid and cycloid. The majority of kosher fish exhibit the latter two forms, ctenoid or cycloid, but the bowfin is an example of a fish with ganoid scales that is deemed kosher. As such, kosher status cannot be said to follow the rules of modern-day classification, and qualified experts on kosher fish must be consulted to determine the status of a particular fish or scale type.
These rules restrict permissible seafood to stereotypical fish, prohibiting the unusual forms such as the eel, lamprey, hagfish, and lancelet. In addition, they exclude non-fish marine creatures, such as crustaceans, molluscs, sea cucumbers, and jellyfish.
Other creatures living in the sea and rivers that would be prohibited by the rules include the cetaceans, crocodilians, sea turtles, sea snakes, and all amphibians.
Image:Acipenser oxyrhynchus.jpg|thumb|An oxyrhynchus sturgeon
Sharks are considered to be ritually unclean according to these regulations, as their scales can only be removed by damaging the skin. A minor controversy arises from the fact that the appearance of the scales of swordfish is heavily affected by the ageing process—their young satisfy Nachmanides' rule, but when they reach adulthood they do not.
Traditionally "fins" has been interpreted as referring to translucent fins. The Mishnah claims that all fish with scales will also have fins, but that the reverse is not always true. For the latter case, the Talmud argues that ritually clean fish have a distinct spinal column and flattish face, while ritually unclean fish don't have spinal columns and have pointy heads, which would define the shark and sturgeon as ritually unclean.
Nevertheless, Aaron Chorin, a prominent 19th-century rabbi and reformer, declared that the sturgeon was actually ritually pure, and hence permissible to eat. Many Conservative rabbis now view these particular fish as being kosher, but most Orthodox rabbis do not.
The question for sturgeon is particularly significant as most caviar consists of sturgeon eggs, and therefore cannot be kosher if the sturgeon itself is not. Sturgeon-derived caviar is not eaten by some Kosher-observant Jews because sturgeon possess ganoid scales instead of the usual ctenoid and cycloid scales. A vegetarian caviar substitute made from kelp has received kosher certification. Atlantic salmon roe is also kosher.