I've heard from Marie-Celine Buchy, and I can put to rest some of the more obvious exagerations and mistakes made by the media. The monster comes from the La Casita Fm (Kimmeridgian), a few km north-west of the village of Aramberri, Nuevo Leon. The first very tenatative estimate of size was of around 15 meters, based a pectoral vertebra 22cm in diameter and other large elements, such as a pterygoid and a partial femur. Obviously this will be revised as the specimen is prepared and we learn more about its morphology.
It is reported by the media as being Liopleurodon ferox, though this was never mentioned by Dino or Marie-Celine. Although Liopleurodon has been reported from the Kimmeridge Clay most of the specimens are series of vertebrae which cannot be identified unambiguously as Liopleurodon based on our current knowledge of its post-cranial anatomy (which is close to non-existent at the moment), or elements such as a lower jaw which, according to Leslie Noè, are definitely not Lipleurodon. Following WWD, it seems that L.ferox has taken the crown as the biggest and fiercest predator ever (move over T.rex) as as such the archetypical big pliosaur. More about Liopleurodon here
Thanks to Tommy Tyrberg for bringing to the attention of the dinosaur mailing list the abstracts of the 6th European Workshop on Vertebrate Paleontology, Florence 2001. This includes the account by Dino Frey, Marie-Celine Buchy and Wolfgang Stinnesbeck (Page 30 athttp://digilander.libero.it/tulse/6ewvp/abstractbook%206ewvp.pdf)of various finds of marine reptiles from the area and mentions the 'Monster of Aramberri'. It was apparently mis-identified as a dinosaur. As an aside, whenever I visit a new collection I always look through the drawers marked 'ichthyosaur', 'dinosaur' and 'reptilia indet' - they are a rich source for new pleiosaur material.
Many reports on the monster are available on-line. They make an interesting study in the process of 'godzillaisation' - accounts of the specimen inflating the size and ferocity until it has acquired an awsome and improbable suite of characters. Its granite-chewing dentition is my personal favourite.
I'll update this page when I hear from Marie-Celine or Dino.