Rashi on Deuteronomy 14:7/רש"י על דברים י״ד:ז׳

1השסועה — (lit., a cleft one) is a certain animal which has two backs and two spinal columns (Chullin 60b). — Our Rabbis asked, “Why are these (the clean and unclean beasts and fowls) here repeated” since the names have already been mentioned in Leviticus XI? They replied: the repetition was necessary so far as quadrupeds are concerned because of the שסועה, and so far as fowls are concerned because of the ראה, both of which are not mentioned in Torath Cohanim (i.e. Leviticus) (Chullin 63b).