Parthe, dabis poenas: Crassi gaudete sepulti,
Signaque barbaricas non bene passa manus.(Ars Amatoria 1, 179-180)
Further to your answer I'd like to ask you if 'Crassi sepulti'
can also be translated as 'Crassus and his son buried'?
In “Parthe, dabis poenas: Crassi gaudete sepulti, /Signaque barbaricas non bene passa manus./ Ultor adest...” (Ovid, Ars Amatoria 1, 179-181) meaning:” O Parthian, you will pay the penalty: rejoice, o buried soldiers of Crassus, and you military standards that have suffered the shame of being captured by barbarous hands. / The avenger is here..” the expression "Crassi... sepulti" cannot be translated as "Crassus and his son buried" , first because there is no son of Crassus, second because “sepulti” followed by the genitive “Crassi” is a vocative plural (literally, “o buried”), finally because the vocative plural “sepulti” goes with the other vocative plural “signa” (military standards) to which "sepulti" is grammatically connected by the enclitic -”que”, so that both "sepulti" and "signa" go with the imperative “gaudete" (2nd person plural).
To conclude, there is no reason why "Crassi... sepulti" must be translated as “Crassus and his son buried", though Publius Licinius Crassus, son of Marcus Licinius Crassus, died in the battle with Parthians (See Plutarch, Life of Crassus, 25 ff)