added Quaternary to 'periods' scale and switchced to using explicit base and top Ma values to avoid assuming that scales end at the Recent
added Quaternary to 'periods' scale and switchced to using explicit base and
top Ma values to avoid assuming that scales end at the Recent

paleobiodb/pbdb-new,paleobiodb/pbdb-new,paleobiodb/pbdb-new,paleobiodb/pbdb-new,paleobiodb/pbdb-new