Inconsistent plural forms in Mesozoic achievements (literally unplayable!)

[restive spade]

Objectives for Mesozoic achievements, such as "75 Archosaurs created", have dinosaur names in plural in some cases and in singular in others.
Archosaurs, Ornithischias, Sauropods, and Velociraptors are in plural while everything else is singular (at least until Archaeopteryx, I don't have further achievements).
It's not even consistent for different endings (which I could let slide because Latin is hard) - for example, Pterosaur is in singular.