A variant spelling of the headword exists, with accent on the penult, but the sense is dubious in either case: see Cunliffe, p. 273 and LSJ s.v. mo/rfnos, -o(.
The headword and glosses (see n. 1-2 below) are generated from Homer, Iliad 24.316 (web address 1) and its scholia, where the masculine accusative singular form of the headword, mo/rfnon (dusky), appears as an epithet of the eagle; cf. mu 1268 and Richardson, p. 305. As a substantive, though, the headword occurs at Aristotle, History of Animals 618b26. The change in accentuation from ultima to penult may indicate a change from adjective to substantive in the word's usage (Chantraine s.v. mo/rfnos).
[1] For the masculine accusative singular form of the headword, other lexica (see the references at Photius mu542 Theodoridis) and a scholion to Homer, Iliad 24.316 (see above) all provide the same gloss; cf. Etymologicum Magnum 591.16 (Kallierges).
[2] cf. (e.g.) the scholia to Homer, Iliad 24.316 (above) and Etymologicum Magnum 591.22 (Kallierges). The term moro/fonos occurs only in the explanations of this passage.
[3] The Suda appears to associate the ominous bird with a carrion eater; however, the reference at Homer, Iliad 24.316 (see above) is to a bird that is a mo/rfnon qhrhth=ra (dusky hunter, masculine accusative singular). The one plausible identity for the bird, assuming the treasury-door imagery for the huge wingspread at Homer, Iliad 24.317-18 (web address 1) to be accurate, is the Golden Eagle, Aquila chrysaetos (Richardson, pp. 305-6; Peterson, p. 77).