Breakdown of Ellas dijeron que el oro es muy antiguo.
ser
to be
ellas
they (feminine)
muy
very
que
that / than
Questions & Answers about Ellas dijeron que el oro es muy antiguo.
Why is it dijeron and not "decieron" or "dijieron"?
Dijeron is the "they" form of decir (to say) in the preterite (completed past) tense. Decir is highly irregular: its stem changes to dij-. Also, verbs that get a j in their irregular past stem drop the i in the ending. So, instead of the normal -ieron ending for this group, it just takes -eron, making it dijeron.
Why use the present tense es if they "said" it in the past?
Just like in English, Spanish uses the present tense es here because the gold is still ancient today. When someone talks in the past about a general fact that remains true in the present, you can keep the second verb in the present tense.
Could I use viejo instead of antiguo here?
In English we can just say "They said the gold is ancient." Can I drop que in Spanish?