I have come across a reference (in the Wikipedia article on Caucasian-Albania) to a campaign by Pompey the Great against the Kingdom of Albania in the Caucasus Mountains; Plutarch reports that while Roman forces were fording the Alazan River they were attacked by the forces of Oroezes, King of Albania. Pompey defeats the Albanians, and then "…after the battle, Pompey set out to march to the Caspian Sea, but was turned back by a multitude of deadly reptiles when he was only three days march distant, and withdrew into Lesser Armenia…". What reptiles are being referred to here (apparently capable of compelling Roman Legions, commanded by a popular war-leader, to reverse their direction of march) and what was so special or dangerous about them? Additionally, have there been any historical inaccuracies concerning Pompey’s actions in Caucasian-Iberia and his reported activities in Hispania/the Iberian Peninsula during the Sertorian War (or have I been reading too many Dan Brown novels)?
I can only find the occurrence of this event in Vol.V of Plutarch's "The Parallel Lives" After looking into the terrain of hyrcania and the present day reptile species inhabiting the area I would assume Pompey was fearful of the various venomous snakes that inhabit the forests. I imagine he didn't fancy his chances marching a legion through a snake infested route. My guess would be either Naja oxiana or Gloydius halys. Could not find any information on extinct reptiles in the area though. Thus, the possibility of a much more terrifying giant lizard resembling a komodo dragon remains.