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This is an idea that I’ve had knocking around in my head for a while. A recent post by fellow paleo-blogger Chase (who has a special interest in eastern North American Mesozoic life) on Dryptosaurus has spurred me to action in terms of writing a short article as well as doing some much delayed artwork.
For those of you who are too lazy to read Chase’s excellent article about this animal, Dryptosaurus was a medium-sized theropod dinosaur, approximately 20-25 feet long which lived in eastern North America during the late Cretaceous Period. Unfortunately, our total knowledge of this dinosaur is known from only a few fragmentary remains, including a hand claw that seems way too big in proportion with the rest of this animal’s body.
For as far back as I can remember, Dryptosaurus was classified as a tyrannosaur. But recently, I have my doubts about this classification. Even very primitive tyrannosaurs such as Guanlong and Proceratosaurus don’t have some of the anatomical features that Dryptosaurus appears to possess.
My curiosity centered around that claw. It didn’t look like a tyrannosaur claw – to me, it looked more like an allosaur claw. An unusually large hand claw also reminded me of another animal – Megaraptor, from South America. Originally, this was thought to be a gigantic dromaeosaur, but then it was hypothesized to be more closely related to the allosauroids, like Neovenator, Giganotosaurus, and Carcharodontosaurus. The allosaur-like claw would make this classification a good fit. Then I saw a picture of the skeletal remains of Australovenator, a megaraptorid that was discovered in (you guessed it) Australia. I immediately noticed similarities in the hand and body structure between Australovenator and Dryptosaurus.
- Massive thumb claws in comparison with the other finger claws.
- Short muscular arms and huge hands
- Slender lower jaws with small closely-packed hook-shaped teeth.
What I find really interesting is that in 2012, a hypothesis was put forward by Fernando Novas and other paleontologists that the megaraptorids might actually be extremely primitive members of the tyrannosaur family. In 2014, fragments from a juvenile Megaraptor were discovered, including part of the upper jaw. The structure of the juvenile Megaraptor’s maxilla was very similar to the structure of the dentary from Australovenator. That year, Juan Porfiri re-iterated Novas’ hypothesis that the megaraptorids might be primitive tyrannosaurs.
So, with all of that being said, I hypothesize that Dryptosaurus was a member of Megaraptora, which would make it the first of its kind found within North America.
How did Dryptosaurus feed? The large hook-shaped claws and the small hook-shaped closely-packed teeth seem to indicate that Dryptosaurus and other megaraptorids were fish-eaters. The fossils of Dryptosaurus were discovered in the New Egypt Formation and the Navesink Formation, the later of which is known for both dinosaur fossils as well as fossilized shells. Also, Australovenator was found in deposits that indicate a swampy still wetlands environment, full of bivalves, fish, and turtles. The fact that this megaraptorid was found in a water-rich environment full of aquatic life leads me to suspect that Dryptosaurus might have had a similar lifestyle.
To conclude this short article, I have a drawing of the enigmatic Dryptosaurus portrayed as a megaraptorid rather than as a typical often-illustrated tyrannosaurid. Who knows – maybe my less-than-scholarly idea about Dryptosaurus being a fish-eating megaraptorid will prove out to be right. Only time and the discovery of more specimens will tell.
Keep your pencils (and minds) sharp, everybody.