The ever popular Spinosaurus. Originally found in the desert near Egypt (mid Cretaceous rocks) at the beginning of the 20th century, all the original material was lost during the bombing of Germany during WWII. We are lucky to have drawing of the material so all was not lost! The original material which consisted of the front part of the lower jaw, a few neck vertebrae, a few tail vertebrae, and most of the back vertebrae with the elongated neural spines. The original restoration was of a giant allosaur with a sail, like this drawing. The exact size of is hard to pinpoint. The original material appears to not have been fully grown. Sizes from 50 to 65 feet have been offered, but we'll have little to no idea until a new skeleton is found.
For a long time that was the restoration, until the 80's, when Baryonyx was found. It was quickly discovered that the 2 species were very similar, that gave us our first decent peek at what a spinosaur looked like. In this restoration I bulked up the skull a bit, the lower ends shortly after the tip, but the back of the jaw bone looks very robust. So I toyed with the idea that Spinosaurus was sort of returning to a more predatory dinosaur, Baryonyx was considered a fish eater (even though iguanadon bones were found in it's stomach contents, along with fish scales) so the skull was more delicate.
In 2003 it was suggested that Spinosaurus was actually a chimera (made up of more than on animal) since it was found in a bone bed with other animals. The jaw belonging to a spinosaur, the neck to a relative of Acrocanthosaurus. The back to a sauropod (all of the three major dinosaur branches produced a 'fin' back.) I actually like the idea (I suggested a hadrosaur for the backbone since the older adults bones seem to mimic theropods, something I didn't know until I saw Valley of the T. rex with Jack Horner. But a sauropod would explain the great size) I liked the idea of a chimera, the sail would be a great hindrance to an active predator. But science changes and moves on...
It was reported that a new skull was found earlier this decade, something that would have been around 8 feet long. Now there was/is a possible relative of Spinosaurus, or in this case a subspecies, also found in Africa, this was dubbed Spinosaurus marocannus. Only the front part of the upper jaw was found, it was very delicate. But this new skull, seemed to link the 2 species/subspecies together, the new skulls teeth matched the original lower jaws teeth so it appears that the more robust skull I drew was wrong, so this drawing was done.
This is the most recent drawing, based on all the info I could find online. It looks like Spinosaurus is actually closely related to the South American spinosaur Irritator. At first Irritator was thought to be a pterosaur (it's skull is really strange even for a spinosaur,) but the new skull material for Spinosaurs matches it rather closely, even similar in tooth count.
What appears to be emerging is a very different animal than originally described. Long and lean, the nostril s far back on the skull, the neck designed for a more heron like attack. It appears to be a giant fish eater, perhaps it was forced to the water as it's great length wouldn't protect it from the other giant theropods that shared it's environment? (Carcharadontosaurus, Deltadromeus and possibly a few others, the remains are too scrappy.)
But what of the sail? It's been theorized that it was for fat storage, but the spines are very thin, I doubt they could have supported much weight. Possibly for cooling? Other theropods with similar size didn't have one, but maybe it helped when fishing in the afternoon, it does get hot inthe sun. I've also heard it was used as an actual sail for swimming... We know theropods could swim, we have 'foot' prints, really just nail prints;) But none of the other spinosaurs with associated skeletons show aquatic adaptions.. So I had an idea. It might be wrong, but what about a shade for hunting in the sun? Something to keep the glare of the sun off the water so it can see the fish below? Or maybe a combination of these? That's the most plausible scenario seeing as most parts of the body preform several functions.