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This post is a couple of days late, but I hope you’ll forgive me. A few days ago, University of Bologna paleontologist Federico Fanti and his colleagues announced that they had discovered the fossilized remains of a thirty-foot crocodile in southern Tunisia within rocks dated to the early Cretaceous Period, about 130 million years ago. The skull alone was five feet long. The fossils had been found in December 2014, and the skeleton, remarkably, was associated (meaning that all of the bones came from one individual, and were not the jumbled remains of multiple individuals) and the skeleton was articulated (all of the bones were in their proper anatomical placement).
Machimosaurus rex, as it has been named, belonged to a group of oceanic crocodilians called the teleosaurids, which was thought to have gone extinct at the end of the Jurassic Period. The genus Machimosaurus had first been described in 1837 by the German paleontologist Christian von Meyer. Prior to the discovery of M. rex, there were four other species known to science, most of which lived in Europe during the Jurassic Period.
Although certainly large, Machimosaurus is still not as big as the two tie-winners for “largest crocodile ever”: Sarcosuchus and Deinosuchus, both of which measured forty feet long.
The discovery and naming of this crocodile was published in the journal Cretaceous Research.
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.
This is a drawing of Lonchidion, a hybodont shark from the Mesozoic Era. There were at least eleven different species, one of which was found in the Hell Creek Formation. I won’t get into all of the particulars regarding this genus or the Hell Creek species in particular (L. selachos). Their size depended upon the species, some being very small. Lonchidion selachos may have been three feet long, judging by the size of its dorsal spines. The drawing is based upon the preserved remains of other hybodont sharks, because specimens from the Hell Creek Formation consist mostly of teeth, well-preserved specimens of any Lonchidion species are very rare, and as far as I am aware, they looked more or less like other well-known hybodonts.
Hybodont sharks are identified by their large dorsal fin spines as well as the four large spines atop their heads, which are really overly-enlarged denticle scales found all over the rest of the body. Hybodonts first appeared during the Carboniferous Period, but it was during the Jurassic that they came into their own. However, by the Cretaceous Period, they were being replaced by so-called “modern” sharks very similar to the ones we see today. Lonchidion was one of the last surviving members of its kind before the whole hybodont group (the few species that remained, anyway) was completely wiped out at the end of the Mesozoic Era 65 million years ago.
Here are color pencil drawings of two geni of prehistoric fish. Their fossils have been found in central Europe in rocks dating to the late Triassic Period. Both of these fish belong to a group called the pycnodonts, and it seems that they fed primarily upon mollusks and small crustaceans. Pycnodonts first appeared during the late Triassic Period, and became completely extinct during the Eocene Epoch of the Tertiary Period.
The first one is called Brembodus ridens. Among its features was a short spike on its back formed by extensions of the skull bones. This might have been meant to deter predators, like a modern-day triggerfish.
The second fish is called Eomesodon liassicus. It looked remarkably similar to a modern-day tang or surgeonfish, except I’m not sure if the typical surgeonfish caudal blade (a sharp pointed piece of bone, located on both sides of the base of the tail, which could be extended if needed) has been found in association with specimens of this particular genus. As to the color, it’s pure guesswork on my part.
Hope you enjoy, and I look foward to any feedback.
Let’s change from dinosaurs to some other prehistoric life. Here are two prehistoric sharks. The large gray one on top is called Cretoxyrhina mantelli, more commonly known as the Ginsu Shark. The smaller blue one underneath is called Squalicorax falcatus, more commonly known as the Crow Shark. These two species are only a handful of prehistoric animals that have common names ascribed to them – most paleo-critters have only their scientific names.
Both of these prehistoric sharks lived in what was called the Niobrara Sea, also called the Western Interior Sea, which covered the central third of North America during the late Cretaceous Period. Both of these sharks are classified as being lamniform sharks, also known as mackerel sharks. This is the same group which includes the Mako and the Great White. “Modern” sharks first appeared on Earth towards the end of the Mesozoic Era, and both of these species are good examples of early modern sharks.
Cretoxyrhina was a large twenty-foot shark. It lasted from 100-82 MYA, and it was probably the top predator in its environment during that time. However, during the Cretaceous Period, a new group of marine carnivores appeared called mosasaurs. These creatures were literally oceanic lizards – in fact, their closest relatives are today’s monitor lizards, like the ten-foot Komodo Dragon. But mosasaurs got much bigger than this, with some reaching over forty feet long. The mososaurs out-competed this large shark for food and drove it into extinction.
The smaller Crow Shark appears to have been much more versatile. It evolved into several different species, some measuring six feet long, while others reached as high as sixteen feet in length.
One of the things that you’ll immediately notice about this drawing is that it’s in color. I very rarely make color drawings – I usually just stick to grayscale. The reason why is because I haven’t really gotten the knack for making illustrations in color yet. I’ve been working in black-and-white for a long time, and I dare say (at the risk of tooting my own horn) that I’ve gotten pretty good at it. I don’t like using color because it washes out all of the texture and detail. Well, it’s a learning process. I’m sure that I’ll get the hang of it sooner or later.
Keep your pencils sharp.