Although the Metamorphoses of the Roman poet Ovid constitute a massive compendium of narratives of transformations, this epic poem does not remotely exhaust the body of such Greco-Roman myths. The present text is extremely curt, but preserves some unique stories.
2 Translation (A. Westermann, Scriptores rerum mirabilium Graeci, pp. 222–223)
(1) King Lycaon (Lykáōn) was transformed into a wolf (lýkos) because he serves human flesh on his table for Zeus, who was being entertained as a guest by him.
(2) Argus (Árgos) the all-seeing guard of Io, when he was destroyed by Hermes, transformed into the bird peacock (taṓn) by the compassion of Hera; the great number of his eyes is (still) visible in his feathers.
[The peacock is the sacred bird of Hera.]
(3) When the nymph Syrinx (Sýrinx) was pursued by Pan, she threw herself into the river Ladon, reeds grew up, and Pan cut them, constructed an instrument from them, and called it sýrinx (‘pan flute’) in the honor of said nymph.
[The pan flute is, of course, sacred to Pan.]
(4) Cycnus (Kýknos), the son of Sthenelus, because of his mourning over Phaëthon, transformed into the bird of the same name (‘swan’).
[This is the famous Phaëthon, child of the Sun, who died attempting to fly the chariot of his father, with whose mourning various myths are connected.]
(5) Corone (Korṓnē), the daughter of Coroneus, the lord of the Phocians, fled the desire of Poseidon, and transformed into the bird of the same name (‘crow’) by the compassion of Athena.
[Pausanias 4.34.6 mentions a statue of Athena holding a crow in its hand; but the crow was said to be unable to approach her temple at Athens, according to Antigonus the paradoxographer (Collection of Miraculous Stories 12, off-site link). The bird is also associated with Leto, Artemis and Apollon.]
(6) Nyctimene (Nyktiménē), the daughter of Clymenus, fled the desire of her father, and was transformed into an owl (glaûx) by the compassion of Athena.
[The owl is, of course, sacred to Athena; see, e.g., Porphyry on Iliad 10.274.]
(7) When the Sun wanted to have intercourse with Leucothoe (Leukothóē), the daughter of Orchomenus, he took on the shape of the daughter of said woman (to be able to approach and sleep with her). When her father buried her alive (in punishment), the Sun transformed (her) into the frankincense-bearing tree, and made it grow from her tomb, and transformed her sister into the herb heliotrope, because she had accused (Leucothoe to their father).
[This myth is told more fully in Ovid, Metamorphoses 4.192–270. It is meant to explain why the two plants are sacred to the Sun; and note that, in PGM 1.63–64, in the context of an invocation of the Sun, the practitioner is directed to burn (uncut?) frankincense (and libate rose oil) on ashes of the plant heliotrope, on an earthen censer.]
(8) Leucone (Leukṓnē), the wife of Cyanippus, who was a man devoted to hunting, grew jealous and suspected that he was meeting another woman, followed him, hid in the forest unseen, and was torn apart by her husband’s dogs.
[This myth contains no transformation, neither here nor in other tellings; neither does the following, strictly speaking.]
(9) Polyhymnus (Polýhymnos) of Argus, who was enamored of Dionysus, promised to show him the way down into the underworld which he was seeking (to bring his deceased mother Semele to heaven), if he would grant him his graces (sexually). When the god acquiesced, he showed him that (the descent goes) through Lerna, which is an abyss. However, when Dionysus had lead Semele up, he found Polyhymnus dead; but wishing to keep his oath, he went to the grave of his lover, and rode(?) on a fig-wood phallus. On this account, some say, are phalloi set up for the god, as memorials of his faithfulness to the oath.