Anyway, National Geographic News reports we have a new contender for biggest fossil marine reptiles. It is one of the icthyosaurs, which look like a bit like obese giant dolphins with an extra pair of flippers toward the rear. The newest fossil jaw, from Somerset in the United Kingdom, compared to the jawbones of more complete icthyosaur specimens, indicates an animal of just under 26m (85 feet)!
Dr. Darren Naish, a paleobiologist I know who is quoted in the article, is a cautious man when it comes to claims of gigantic prehistoric beasts: he has argued strongly that estimates of 27m for the giant fish Leedsichthys and 18m+ for the pliosaur called the"monster of Aramberri," are enormously overstated. However, he agrees the estimate for this titanic icthyosaur looks correct based on the jawbone, which is nearly a meter long. (Darren knows icthyosaurs: for one of his related posts, see here.)
If the article writer is a little overenthusiastic in comparing the animal to a blue whale (a blue whale over 33m long is on record) it is nevertheless an awe-inducing creature. The new species (unnamed at present) was apparently larger than the biggest predator now living anywhere, the sperm whale.
So that will do fine as a monster.
Icthyosaur (copyright unknown)