''Toothy Toothy Whales Mk.III''

Here we go again! I would call this update Kronos Rising, but I don't want to be associated with that.

The Monster of Aramberri: The 140-million-year-old pliosaur from Mexico isn't extremely long (as vertebral length, obviously, is the best way to estimate overall length, as opposed to vertebral width or height, I used the mean given by McHenry from those results). It is quite robust, on the other hand, since the latter dimensions are unusually large, and so it would have an estimated mass of ~10.4 tonnes rather than the ~8.6 tonnes we would get from isometrically scaling down other pliosaur models, making it the second largest pliosaur currently known, after Kronosaurus queenslandicus.

Pliosaurus macromerus?: Specimen OUM J.10454 (''the Cumnor mandible'') was originally estimated at 2.87 m, interpreted by McHenry as coming from a pliosaur over 17 tonnes, but the measurements of its symphysis are only 30% larger in linear dimensions than the P.macromerus holotype, which has a lower jaw 1.73 m in length. Using the proportions of P.carpenteri, this results in much more modest dimensions. This downsize is in agreement with a comment by Richard Forrester, who believes the Cumnor mandible could have been reconstructed up to a meter too long.

Kronosaurus boyacensis: The Colombian kronosaur, although seemingly not having been too well-studied since its discovery nearly 30 years ago, is still a remarkable specimen, missing only the tail (K.queenslandicus shares this issue, due to which we speculated the tail to be roughly 80% as long as the torso, which is generally true of most plesiosaurs with complete tails), which makes its total length very hard to mistake. 

Kronosaurus queenslandicus MCZ 1285: With a name referencing a devourer of gods, it does seem that Kronosaurus ''devoured'' everything in its way, both in the sense of its ecology and size rankings. MCZ 1285 preserves a nearly complete postcranial skeleton, although it is missing a skull, which can be inferred from the even more complete K.boyacensis to be over 2.5 meters (along the midline; the maximum measurements would have been larger, and I'm not even mentioning the lower jaw). 

Pliosaurus kevani: Being nested in a polytomy with P.carpenteri and P.funkei, its proportions could have been closer to the latter, which would make it far more impressive (you can see the carp-edition in AlternatePrehistory 's chart) or to the former, as is represented here. Its skull was used as a reference for that of P.funkei.

Pliosaurus funkei PMO 234.136: The previous one was based on a 1:5 skull-to-body-length ratio (which is kinda, err, nonexistant in the genus), while the new one is closer to 1:4 or so. The vertebrae are all around 9% longer than in PMO 234.135, indicating a length of almost nine meters.

Pliosaurus carpenteri: One of the most complete and relevant of Pliosaurus specimens, this smaller species was added in for its reference in the proportions of P.macromerus as well as.. idk, aesthetics.

Pliosaurus funkei PMO 234.135: The original ''Svalbard Pliosaur''. Knutsen et al. (2012) indicates that the flippers of Pliosaurus funkei were absolutely enormous in comparison to its body relative to other pliosaurs (here they are shown in perspective, as pliosaur flippers were not parallel to the sagittal plane in life, which makes them look shorter). Unfortunately, that means that scaling from a flipper alone grossly overestimated the size at first - as it turns out, the Svalbard Pliosaur is not a specimen of record-breaking size, although still quite large.

References:
Tarlo (1959) "Stretosaurus gen. nov., a giant pliosaur from the Kimeridge Clay"
McHenry (2009): ''Devourer of Gods: the palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus''
Knutsen et al. (2012): ''A new species of Pliosaurus (Sauropterygia, Plesiosauria) from the Middle Volgian of central Spitsbergen, Norway''
Knutsen (2012): ''A taxonomic revision of the genus Pliosaurus (Owen, 1841a) Owen, 1841b''
Benson et al. (2013): ''A giant pliosaurid skull from the Late Jurassic of England''
Páramo-Fonseca et al. (2016): ''Stenorhynchosaurus munozi, gen. et sp. nov. a new pliosaurid from the Upper Barremian (Lower Cretaceous) of Villa de Leiva, Colombia, South America''
Pliosaurus funkei, P.carpenteri and P.macromerus skeletals by (see his chart of Pliosaurus species, which also includes P.rossicus and carp-edition P.kevani)
Original research by and (as in reading through a billion confusing papers and getting measurements and stuff) 

Previous version for comparison

UPDATE 02/09/18: Replaced Pliosaurus and Kronosaurus queenslandicus silhouettes (both of them given by ). Also updated macromerus and carpenteri sizes.