Question: What group of languages includes the old version of the language associated with the myth where two canines watch over the Chinvat Bridge?

full_context: Document 1: Cerberus Palus: Cerberus Palus is a plain in the Elysium quadrangle of Mars, centered at . It is 470 km across and was named after a classical albedo feature Cerberus.
Document 2: Iranian languages: It is possible that other distinct dialect groups were already in existence during this period. Good candidates are the hypothethical ancestor languages of Alanian/Scytho-Sarmatian subgroup of Scythian in the far northwest; and the hypothetical "Old Parthian" (the Old Iranian ancestor of Parthian) in the near northwest, where original *dw > *b (paralleling the development of *ćw).
Document 3: Iranian languages: What is known in Iranian linguistic history as the "Middle Iranian" era is thought to begin around the 4th century BCE lasting through the 9th century. Linguistically the Middle Iranian languages are conventionally classified into two main groups, Western and Eastern.
Document 4: Dog: In Greek mythology, Cerberus is a three-headed watchdog who guards the gates of Hades. In Norse mythology, a bloody, four-eyed dog called Garmr guards Helheim. In Persian mythology, two four-eyed dogs guard the Chinvat Bridge. In Philippine mythology, Kimat who is the pet of Tadaklan, god of thunder, is responsible for lightning. In Welsh mythology, Annwn is guarded by Cŵn Annwn.
Document 5: Iranian languages: In addition to Old Persian and Avestan, which are the only directly attested Old Iranian languages, all Middle Iranian languages must have had a predecessor "Old Iranian" form of that language, and thus can all be said to have had an (at least hypothetical) "Old" form. Such hypothetical Old Iranian languages include Carduchi (the hypothetical predecessor to Kurdish) and Old Parthian. Additionally, the existence of unattested languages can sometimes be inferred from the impact they had on neighbouring languages. Such transfer is known to have occurred for Old Persian, which has (what is called) a "Median" substrate in some of its vocabulary. Also, foreign references to languages can also provide a hint to the existence of otherwise unattested languages, for example through toponyms/ethnonyms or in the recording of vocabulary, as Herodotus did for what he called "Scythian".
Document 6: Odin: In Old Norse texts, Odin is depicted as one-eyed and long-bearded, frequently wielding a spear named Gungnir, and wearing a cloak and a broad hat. He is often accompanied by his animal companions and familiars—the wolves Geri and Freki and the ravens Huginn and Muninn, who bring him information from all over —and rides the flying, eight-legged steed Sleipnir across the sky and into the underworld. Odin is the son of Bestla and Borr and has two brothers, Vili and Vé. Odin is attested as having many sons, most famously the gods Thor (with ) and (with ), and is known by hundreds of names. In these texts, he frequently seeks greater knowledge, at times in disguise (most famously by obtaining the Mead of Poetry), makes wagers with his wife Frigg over the outcome of exploits, and takes part in both the creation of the world by way of slaying the primordial being and giving the gift of life to the first two humans Ask and Embla. Odin has a particular association with Yule, and mankind's knowledge of both the runes and poetry is also attributed to him, giving Odin aspects of the culture hero.
Document 7: Iranian languages: Old Persian is the Old Iranian dialect as it was spoken in south-western Iran by the inhabitants of Parsa, who also gave their name to their region and language. Genuine Old Persian is best attested in one of the three languages of the Behistun inscription, composed circa 520 BC, and which is the last inscription (and only inscription of significant length) in which Old Persian is still grammatically correct. Later inscriptions are comparatively brief, and typically simply copies of words and phrases from earlier ones, often with grammatical errors, which suggests that by the 4th century BC the transition from Old Persian to Middle Persian was already far advanced, but efforts were still being made to retain an "old" quality for official proclamations.
Document 8: Iranian languages: The other directly attested Old Iranian dialects are the two forms of Avestan, which take their name from their use in the Avesta, the liturgical texts of indigenous Iranian religion that now goes by the name of Zoroastrianism but in the Avesta itself is simply known as vohu daena (later: behdin). The language of the Avesta is subdivided into two dialects, conventionally known as "Old (or 'Gathic') Avestan", and "Younger Avestan". These terms, which date to the 19th century, are slightly misleading since 'Younger Avestan' is not only much younger than 'Old Avestan', but also from a different geographic region. The Old Avestan dialect is very archaic, and at roughly the same stage of development as Rigvedic Sanskrit. On the other hand, Younger Avestan is at about the same linguistic stage as Old Persian, but by virtue of its use as a sacred language retained its "old" characteristics long after the Old Iranian languages had yielded to their Middle Iranian stage. Unlike Old Persian, which has Middle Persian as its known successor, Avestan has no clearly identifiable Middle Iranian stage (the effect of Middle Iranian is indistinguishable from effects due to other causes).
Document 9: Western Iranian languages: The Western Iranian languages are a branch of the Iranian languages, attested from the time of Old Persian (6th century BC) and Median.
Document 10: Iranian languages: The multitude of Middle Iranian languages and peoples indicate that great linguistic diversity must have existed among the ancient speakers of Iranian languages. Of that variety of languages/dialects, direct evidence of only two have survived. These are:
Document 11: Dog: In Asian countries such as China, Korea, and Japan, dogs are viewed as kind protectors. The role of the dog in Chinese mythology includes a position as one of the twelve animals which cyclically represent years (the zodiacal dog).
Document 12: Iya (mythology): In Lakota mythology, Iya is a storm-monster, brother of Iktomi the spider. He eats humans, animals and consumes villages to satisfy his otherwise endless appetite. This fact, however, does not make him bad or evil; he simply performs a duty and is considered a sacred being. He is the eye of the storm, and offers protection to those caught in his wake. The tornado, the snowstorm, the hurricane or the thunderstorm would all be considered manifestations of this deity. He travels with his storms in a fabulous tipi painted with magical symbols, and when he appears, he is often faceless and formless. His home is said to be under the waters, where he resides with his mother, Unk.
Document 13: Iranian languages: Two of the earliest dialectal divisions among Iranian indeed happen to not follow the later division into Western and Eastern blocks. These concern the fate of the Proto-Indo-Iranian first-series palatal consonants, *ć and *dź:
Document 14: Dog: Humans would also have derived enormous benefit from the dogs associated with their camps. For instance, dogs would have improved sanitation by cleaning up food scraps. Dogs may have provided warmth, as referred to in the Australian Aboriginal expression "three dog night" (an exceptionally cold night), and they would have alerted the camp to the presence of predators or strangers, using their acute hearing to provide an early warning.
Document 15: Dog: In Islam, dogs are viewed as unclean because they are viewed as scavengers. In 2015 city councillor Hasan Küçük of The Hague called for dog ownership to be made illegal in that city. Islamic activists in Lérida, Spain, lobbied for dogs to be kept out of Muslim neighborhoods, saying their presence violated Muslims' religious freedom. In Britain, police sniffer dogs are carefully used, and are not permitted to contact passengers, only their luggage. They are required to wear leather dog booties when searching mosques or Muslim homes.
ground_truth: Iranian languages
sub_queries: In what mythology do two canines watch over the Chinvat Bridge? Answer: Persian
Old Persian >> part of Answer: Iranian languages