Sir Richard C. Jebb, Commentary on Sophocles: Oedipus at Colonus

κτίσας, “"having instituted,"” brought into use among men, as one could say “κτίζειν νὁμιμα” on the analogy of “κτίζειν ἑορτήν” etc. Greek mythology places Poseidon in two distinct relations to the horse. (a) As creator. Servius ad Verg. Geo. 1. 12 “ideo dicitur ecum invenisse quia velox est eius numen et mobile sicut mare.” (So waves on a rough sea are “"white horses,"” Ital. cavalloni.) The Thessalians connected this myth with the cult of Poseidon “Πετραῖος”, who had caused the first horse (“Σκύφιος”) to spring from a rock in Thessaly,—the name being taken from “σκύφος”, a rocky cup, where perh. marks in the rock were shown. From Tzetzes on Lycophron 767 it seems that this legend was in later times localised at Colonus also. Arcadia and Boeotia, too, had their legends, in which the first horse was called “Ἀρίων” (the wondrous steed of Adrastus in Il. 23.346). (b) As tamer. This was the prominent trait of the Corinthian and Attic legends. At Corinth Poseidon was worshipped as “δαμαῖος”, and Athena as “χαλινῖτις” (cp. Pind. Ol. 13.65 ff.). In Thessaly the horse-yoking Poseidon was called “ἴμψιος”: Hesych. “ἴμψας: ζεύξας Θετταλοί, ἴμψιος Ποσειδῶν ὁ ζύγιος”. In Aesch. PV 462 ff. Prometheus is the first who taught men to drive animals,— “ὑφ᾽ ἅρμα τ᾽ ἤγαγον φιληνίους ι ἵππους”.