In western Mongolia, the dragonfly H. baissicus is preserved
together with C. longipoda in the Dzun-Bain Formation where
Ephemeropsis and Lycoptera are absent (Vrsanský, 2008). Their joint
appearance suggests a Barremian or Aptian age (Vrsanský, 2008). A
comparative study of insects inthe Zaza FormationandtheDzun-Bain
Formation shows that the two formations are coeval or the former is
older than the latter (Zherikhin et al.,1999). Therefore the Dzun-Bain
Formation is tentatively considered to beAptian or earlyAlbianin age.