Last night I was reading your checklist of aquatic cryptids from the CFZ blog. The section I found most interesting was the one on Marine Saurians. I had already seen your blog posting on Gambo and the Ambon sea serpent, and I agree that they do seem to form a type separate from the traditional Marine Saurian. What is not clear is the identity; as you stated, it can't be a crocodile because of its smooth skin, and it can't be a whale because it has four flippers. I began doing research into other common candidates to try and find a suitable match.
It can't be an archaeocete. It has too many teeth. And aside from that, no archaeocete that I know of matches Gambo's anatomy.
Gambo (left) compared to Rhodocetus (center) and Protocetus (right). I don't include any more advanced archaeocetes (i.e. Basilosaurus) because they match even less. (All images from wikipedia)
Likewise, I am unable to find a pliosaur species that specifically matches Gambo's anatomy, especially in the shape of the head.
Gambo (left) compared to Macroplata (center) and Liopleurodon (right). Note the neck length in Macroplata compared to Gambo, and likewise compare the shape of Gambo's head to that of Liopleurodon. (Images again from wikipedia)
Likewise, it can't be a mosasaur because, even if they're body shapes DID match, we have fossils showing that mosasaurs had scaly skin, unlike the smooth skin reported in Gambo.
So what candidates DO we have left? After searching the internet for other candidates, I came across a page on wikipedia about a rather obscure group of plesiosaurs called the Polycotylidae. Here's the definition from wikipedia:
Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to the Leptocleididae.
With their short necks and large elongated heads, they resemble the pliosaurs, but closer phylogenetical studies indicate that they share many common features with the plesiosauridae and elasmosauridae. They have been found worldwide, with specimens reported from New Zealand, Australia, Japan, Morocco, the USA, Canada, the former states of the USSR and South America. In 2010, Thililua was transferred to Leptocleididae.
I began searching for images of these creatures and was immediately struck by the similarity to Gambo and the Ambon sea-serpent.
The Polycotylid Trinacromerum (left) and the Ambon sea-serpent (right). Note in particular the shape of the head.
Gambo (left) compared with the skeleton of Dolichorhynchops (right) from wikipedia...
...and with a reconstruction of a living "Dolly" from National Geographic. Note the shape of the head of "Dolly" compared to the shape of Gambo's head.
Gambo by Pristichampsus (Tim Morris) at Deviantart.com, compared to Edgarosaurus from wikipedia.
One reason why a Polycotylid would be a good candidate is their size. Dolichorhynchops grew 12 to 15 feet long; Gambo was reported as being 15 feet long. Also, Gambo was reported as having smooth skin. We know from fossils of the plesiosaur Attenborosaurus that plesiosaurids had smooth skin; it is therefore inferable that the closely related polycotylids would have also been smooth-skinned. Admittedly, tooth count is still a problem; Gambo still has twice as many teeth as fossil polycotylids do. Likewise, fossil polycotylids had nostrils located near the eyes, as opposed to the end of the snout. However, because the general anatomy of a polycotylid fits with Gambo and the Ambon sea-serpent, I am willing to dismiss these discrepancies as minor problems.
I propose, then, that the smaller Marine Saurians, such as Gambo, the Ambon creature, and the Java creature, represent a form of surviving polycotylid plesiosaur. I also propose that they are removed from the larger Marine Saurian group and are put in their own new category, one closer to the long-necked sea-serpent.
Please write back with your thoughts, criticism, and any corrections needed. I hope this may help in clearing up the identity of Gambo and kin.
To which I replied that this sounded like a very good case to call an invocation of Occam's Razor and therefore I was in favor of making the adjustments to all future versions. I mentioned that Pliosaurs were regularly included as candidates for Marine Saurian reports by other authors and that the thought that some reports could be Polycotylids had occured to me before along with the possibility that some of the larger Marine Saurian reports could be something like Liopleurodon, but I chose not to mention that on the blogs (mostly to simplify things) However in this case, I second the motions that Tyler has advanced. Against the idea we have the possible objections that the reconstructions of Gambo show the flippers too short and the tail too long to be one of these Plesiosaurs, but the reconstructions are only rough guides and not the productions of actual eyewitnesses.
Polycotylids are some of the more recent Plesiosaurs and actually an offshoot of the longer-necked Plesiosaurs like Elasmosaurs, and which became shorter-necked secondarily. By doing this, they became faster and more manoeverable, and so they gained a competetive edge. And I have heard of Freshwater Monsters that might also fit the same description: some people have spoken of them as "Nothosaurs" but up to now the best explanation has been that they were the young of the longer-necked Plesiosaur-shaped creatures, but which had not grown the longer necks. Their distribution is irregular but on the other hand they are alleged to be captured fairly often (The 4 foot long creature Sir Arthur Conan Doyle saw off Greece and called either a "Plesiosaur" or an "Ichthiosaur" on different occasions could be one, and if so, the shape would be the reason why he had a confusing use of labels for it. He said he had heard of something similar being caught in a net off Australia. That could also be useful information.)
Best Wishes, Dale D.[PS, Pristichampsus AKA Tim Morris has granted me permission to use his images from Deviant Art. Just in case anybody is wondering about that part.]