The Kronosaurus is a marine reptile that served as one of the main antagonists in The Trench. There were at least three Kronosaurs that resided in the Mariana Trench, where they have evolved to hunt in packs and evolved gills.
They were first encountered by the Proteus while it was exploring the Mariana Trench. The Kronosaurs later devoured the bodies of Sergei and Captain Hoppe and also ripped apart the Epimethius when Terry boarded it. A Kronosaur that entered the research station the Benthos attempted to devour Benedict Singer, but was killed along with Benedict when the walls of the room they were in are destroyed. The second Kronosaur was killed by pressure changing in the environment it was in and caused its head to implode, while the third and last Kronosaur was killed by Angel. Kronosaurus was listed in MEG: Hell's Aquarium as one of the prehistoric marine reptiles that the Dubai aquarium wants David to track down.