Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Parthĕnŏpaeus, i, m., = Παρθενοπαῖος, the son of Meleager and Atalante, one of the seven who went against Thebes: inclutus armis Parthenopaeus, Verg. A. 6, 480; Stat. Th. 4, 248; cf. Hyg. Fab. 99.