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Everyone remembers the anticipation for the newest dinosaur film about to release in theaters nationwide, perhaps globally. It was back in 2001, that everyone waited for the newest installment in the Jurassic Park series. Then, when the audience saw the new theropod dinosaur, Spinosaurus aegyptiacus, the shocks through the theater at the animal that was larger and scarier than T-rex. Then, along came an inferior T-rex, who dies at the claws and jaws of what seemed to be a giant mutant crocodile. Then, everyone left, shocked, scared, awed, or disappointed. The monster stereotype of the past centuries was back. For a while it seemed as though the infamous Tyrannosaurus rex was “dethroned.” The question that most people asked themselves was “what happened?”
However, I would like to point out the truth about that “super predator” as well as it’s relatives such as Suchomimus tenerensis, And Baryonyx walkeri. Spinosaurids were a Cretaceous group of large theropod dinosaurs that had a skull similar to most crocodilians, both modern and prehistoric. In fact, Spinosaurus aegyptiacus, in particular, was NOT the crazy eat-everything-in-sight animal. It seems that Spinosaurus aegyptiacus had inherited that centuries-old stereotype from Tyrannosaurus rex.
I would like to also point out that Spinosaurids like Spinosaurus possibly never hunted on really at all. Most of what people saw in the movie was what director Joe Johnston put into the film. Jurassic Park III was WRONG!!!
The Truth about Spinosaurids:
Spinosaurids were similar to any other theropod in the fact that it DID NOT exist to eat everything. The common characteristics of spinosaurs were their lean, yet well muscled body, their long multi-fingered fore-arms that were possibly dexterous and their infamous crocodilian-like jaws. Another defining feature of all Spinosaurids were the fact that most of the species lived in the Cretaceous period without known relatives. As Spinosaurids go, this part of the evolutionary “tree” ienshrouded in mystery. I, howvever, will take my best guess as to the evolution of Spinosaurids.
First of all, we all know that dinosaurs evolved from archosaurs and other reptiles that survived the Permian extinction around 230 million years ago (correct me if I’m wrong.) As most archosaurs branched off and evolved into the dinosaurs, which in turn, branched off even more until 65 million years ago. A few of the reptiles, however, that preceded the crocodilians (these were archosaurs, you know) possibly branched off ino the crocodilians of the Mesozoic like Deinosuchus and Sarchosuchus imperator. These divided archosaurs that evolved into the dinosaurs and then branched off into the theropods which, again branched off into the crocodilian-like theropods, the spinosaurids. At least, that’s my guess. That’s all it is since we have very limited fossil evidence of the evolution of these unusual theropods.
Also, for more information on Spinosaurus aegyptiacus, check out my seventh Fossil Fact over at my blog.
So... what do you think? Please leave me a comment.
Well, you are right by saying that we have very limited fossil evidence of spinosaurids because the only ‘well preserved’ Spinosauridae are Baryonyx, Suchomimus, Irritator (of which we only have a skull, but the postcranial skeleton is currently described by Machado (2008)), Spinosaurus (of which we only have skull bones currently preserved) and Siamosaurus (which is curenlty described too). However, concerning their evolution, teeth from the Upper Jurassic have been interpreted by Fowler (2007) and Buffetaut (2008) as belonging to Spinosauridae, and Furtado at all. (2007) believe that Poekilopleuron bucklandii discovered in the Middle Jurassic limestone of France is also a Spinosauridae. It means that these crocodile-mimic dinosaurs probably emerged from the middle or late Jurassic from basal Spinosauridae such as Eustreptospondylus (Middle Jurassic). The latter has been described recently by Sadeir et al. (2008) and shares lot’s of synapomorphies with Spinosauridae. Therefore, Spinosauridae did not branched off from theropod very soon.
Secondly, spinosaurids are precisely known to eat everything because evidence of spinosaurid diet have been found in England (Baryonyx gastric contents) and Brazil (pterosaur vertebrae with spinosaurid teeth). These discoveries show that spinosaurid fed fished, but also dinosaurs such as Iguanodon, and pterosaurs.
Nekar
For the references, see my website :
http://spinosauridae.fr.gd/Liens-et-Bibliographie-relative-aux-Spinosauridae.htm
Sorry, I meant Eustreptospondylus (recently described by SadLeir et al. 2007) is a Spinosauroidea, not a Spinosauridae. And Spinosauridae teeth from the Late Jurassic have been found in Tanzania by Janensh (1920, 1925).
Nekar
Nekar- Well, that was the best guess I could make with what I knew. I had no idea of the fossils of Spinosauridae that dated back 145 mya. I also think I mentioned somewhere it seemed to me they “branched” off at some point in their evolution. I feel as though the Spinosauridae is one theropod family that is just enshrouded in mystery.