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Lonchidion, a prehistoric shark

Lonchidion

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.

News: “Nanook of the North”? New tyrannosaur species from Alaska

Paleontologists have recently announced the discovery and naming of a new tyrannosaur species from Alaska. They have called it Nanuqsaurus hoglundi.

The discovery was made by a team of paleontologists working for the Perot Museum of Nature and Science, located in Dallas, Texas; the team was led by Prof. Anthony R. Fiorillo. The fossils were found at the Prince Creek Formation in Alaska in 2006 when the team was hunting for ceratopsians (that’s “horned-faced” dinos, like Triceratops and Styracosaurus). They consist of the front portion of the lower jaw (the bone is called the “dentary” because that’s the bone in the lower jaw that has the teeth in it) and two small pieces of the upper jaw. The pieces were collected, and then gathered dust for a while until Prof. Fiorillo and his associate Dr. Ronald Tykoski re-examined them.

Admitedly, it’s not that much to go on, but apparently, it was enough to create not only a new species, but a new genus. That doesn’t surprise me at all, as paleontologists are well known to be afflicted with what I call “neogenitis” – “the new genus disease”. They just can’t resist making up new names for things. The name Nanuqsaurus derives from the Inupiak word nanuq, meaning “polar bear”, and the ancient Greek word sauros, “lizard”. The species name is in honor of the philanthropist Forrest Hoglund.

The fossils date to 70 million years ago. It appears to be closely related to both Tyrannosaurus rex and a close relative called Tarbosaurus bataar which lived in Mongolia (some paleontologists consider Tarbosaurus bataar merely to be an Asian species of Tyrannosaurus – personally, I don’t buy it for a few reasons, but I won’t get into them here). Based upon the size of the remains, limited though they may be, Nanuqsaurus may have been only half the size of T. rex.

Professor Fiorillo suspects that the animal’s small size might be a reference to a limited food supply up in the Great un-White North of the late Cretaceous. Although only three small pieces were recovered, it is strongly plausible that a northern tyrannosaur like Nanuqsaurus would be covered in an insulating layer of feathery fuzz.

Triceratops

Triceratops

Triceratops was the last and largest of the ceratopsians, the “horn-faced” dinosaurs – other familiar members of this group include Chasmosaurus, Styracosaurus, and Protoceratops. Triceratops existed from about 70-65.5 MYA, and measured 30 feet long. There are currently two confirmed species: T. horridus and T. prorsus; the first one is the more famous and numerous of the two. They can be distiguished by their short nasal horns. Triceratops horridus has a short fat nasal horn, positioned a considerable way up the snout, and sticks more or less straight up, perpendicular to the line of the skull. Triceratops prorsus has a somewhat longer and thinner nasal horn, it is positioned more to the front of the nose, and it is angled forward.

There’s also been a dispute raging over the past few years as to whether or not another ceratopsian species named Torosaurus is actually another older age stage of Triceratops. This is really complicated, so I won’t even bother to get involved in this academic brawl. All I can say is that this subject appears to be just as hotly and intensely debated as the whole dispute regarding T. rex as a predator or scavenger.

The drawing which you see here is Triceratops horridus. One thing that you’ll notice is how large the head is in proportion with the rest of its body. This is not artistic license – the head really was that big! The second thing that you’ll notice is the lack of detail on the skull, showing instead a scarred but still mostly smooth surface. Paleontologists including Jack Horner and Peter Larson suspect that the top of Triceratops’ skull, including its distinctive neck frill, was covered in a layer of keratin, the same stuff that your fingernails are made of. This horny / keratinous covering might have been colored dark, as horn tends to be, or it might have been bright red due to the numerous blood vessels which are imbedded into the frill’s structure. Perhaps the males were brightly and vividly-colored, while the females were more drab and subdued.

Triceratops, regardless of which particular species, was a very populous animal. In the Hell Creek Formation, 60% of the dinosaur fossils found there belong to Triceratops.

I started drawing this picture months ago, but I got stalled with my classes and with the publication process of my book, and so I had to stick it on the shelf. These past few days, I’ve tackled it hard and completed it. I used my preferred medium, regular No.2 pencil.

Goodbye, and I hope that all of you had a good holiday.

Acheroraptor: A new “raptor” dinosaur from the Hell Creek Formation

A few days ago, scientists announced the discovery of a new species of dinosaur – Acheroraptor, “thief from Acheron”. I’m sorry to disappoint all of you Aliens fans, but no, this dinosaur is NOT named after Planet LV-426, code-named “Acheron”. The name actually refers to the Acheron River in ancient Greek mythology, “the River of Pain”. This name is an obvious pun on the name of the place where the fossils were discovered – the Hell Creek Formation in Montana.

Not much is known about this animal, but here are a few statistics. As you can probabaly guess, Acheroraptor is one of the “raptor” dinosaurs made famous by Jurassic Park. Raptors are divided up into two main groups: the dromaeosaurids and the troodontids. Acheroraptor was a dromaeosaurid, and this brings up another issue…

In an earlier post, I talked about Dromaeosaurus, a dromaeosaurid raptor from western North America. I had stated that its teeth had been found in several different locations, including the Hell Creek Formation. Well, that was perfectly true when I wrote it, but not anymore. For the past few decades, paleontologists had been finding raptor teeth in the HCF, and since they looked similar to the teeth of Dromaeosaurus, these teeth were ascribed to that genus. However, Dromaeosaurus was only known from Canada, and its fossils were found in rocks that were dated much older than the Hell Creek Formation – ten million years older, to be exact. But few other raptor dinosaurs were known from late Cretaceous western North America, and the teeth did look more or less similar to the teeth of Dromaeosaurus, and so that was the identification that was given. Now, paleontologists have discovered that all this time they were perpetuating a case of mistaken identity. It actually happens quite often in this particular science. It appears that the teeth which had been found in the HCF for decades actually belonged to this new species, not Dromaeosaurus.

Acheroraptor’s fossils were found in rocks dated to the extreme end of the Cretaceous Period, 65.5 million years ago, right when the dinosaurs became extinct. It therefore appears that Acheroraptor is the earliest-known raptor, geologically-speaking, being around right up the the point when the asteroid hit.

There are few fossils to go on, consisting of a partial maxilla, a partial dentary, and numerous isolated teeth. Based upon shape and size, paleontologists have determined that Acherorapror was a dromaeosaurid, rather closely related to Velociraptor, and have hypothesized that it may have reached ten feet long. Perhaps in the near future, more fossils will be uncovered which will give us a more complete picture of this animal.

And speaking of pictures, here’s my picture of Acheroraptor! – good segway, right? I further improved the wings from my old Troodon and Ornithomimus drawings, and I made the subject a little more three-dimensional. Rather than standing perfectly sideways, it’s positioned on an angle.

I drew the first sketch when I was giving my English students their final exam on Wednesday December 18, and then I polished off the final product when I got home. I had originally intended it to be a full scene with the dinosaur walking along a forest pathway, but I wanted to get a drawing posted right away, and I just didn’t have the time to make a full Henderson-esque setting.

UPDATE: The original Acheroraptor drawing has been removed, because it was too inaccurate.

The striking black-white color scheme is based upon the coloration of the Northern Goshawk. If this drawing was in color, I would have given my creature transparent glassy red eyes. Making this drawing was a real pleasure, and I’m surprised that doing it didn’t take as long as I had expected – only five days. Keep your pencils sharp!

Ornithomimus

Ornithomimus (“bird mimic”) is a dinosaur genus belonging to a group commonly known as the “ostrich dinosaurs” or “ostrich mimics”. This name comes from their very ostrich-like appearance, with toothless beaks, long swan-like S-shaped necks, and powerful muscular legs. There are currently two known species of Ornithomimus: O. velox and O. edmontonicus. This genus lived in western North America at the end of the Cretaceous Period, 75-65.5 MYA.

It was most likely omnivorous, and you can tell that by the size of its belly. Plant-eating animals need large guts to process their food, in contrast to carnivorous animals. If you look at specimens of Ornithomimus, or indeed any ornithomimid dinosaur, particularly ones which preserve the gastralia (belly ribs), you will see that they outline the stomach area. In contrast to the somewhat starved bodies portrayed by many paleo-artists following in Gregory Paul’s footsteps, they clearly show a wide belly. Look here to see an example: http://en.wikipedia.org/wiki/File:Ornithomimus_edmontonicus.jpg

People had suspected for a while that Ornithomimus and its kind had feathers. There were two reasons for this. Firstly, there was its obvious bird-like appearance. Anything which looked THAT bird-like just HAD to have feathers! Well, it’s an interesting point in terms of comparative anatomy, but there was really no hard evience to support it, and no real credible analysis of various dinosaur types and their relations to birds which suggested that ornithomimids had feathers. The second reason answered that last point. With advances in phylogeny (determining where different species fit into the scheme of life and how they are related to each other), paleontologists have determined that the ornithomimids belong to a large group of very bird-like dinosaurs called the maniraptorans. This group included the ornithomimids, therizinosaurs, oviraptors, and the “real” raptors – the Jurassic Park-style raptors, specifically the dromaeosaurids and the troodontids. Maniraptorans are the closest ancestors of birds, and many of them are known to have been feathered. This would imply that the ornithomids were feathered as well. This argument was a bit more convincing than the “it looks like a bird so it must have feathers” argument which was around during the 80s and 90s. However, although it made a good point, there was still no physical evidence to back it up. If ornithomimids were feathered, why hadn’t any feather fossils been found in association with their skeletons?

In the early 2000s, that changed. When three specimens were examined more closely, scientists discovered that two of them possessed “quill knobs” (the places where feathers attach onto the bones) on the arms, and a third specimen – a juvenile – actually had feather impressions along its neck, back, and legs. In 2012, a report was published in the academic journal Science demonstrating that at least one ornithomimid species, Ornithomimus edmontonicus, was covered in feathers throughout its life, and that the adults actually had modern pennaceous feathers on their arms forming flightless wings. Click here to see a preview of this article: http://www.sciencemag.org/content/338/6106/510.

Ornithomimus

This is a drawing of Ornithomimus based upon the findings in that report. As you can see, the arms sport fully-developed albeit flightless feathered wings. Also take note that the feathers do not cover the whole body all around, but only the top and sides – the underside is bare. The color is my own aesthetic guesswork. I decided to make the throat bright red, which (I like to imagine) was used as a courtship display similar to modern reptiles and birds.

Take care, everyone.

Dromaeosaurus

Dromaeosaurus

Dromaeosaurus albertensis was a six-foot carnivore which lived in western North America during the Late Cretaceous Period. It is a distant cousin of Deinonychus and Velociraptor. Only one fragmentary skeleton was found in Alberta, Canada, although its teeth have been found in a number of localities, including the Hell Creek Formation. Like many members of Maniraptora, it is believed that Dromaeosaurus had feathers.

This drawing was made using that same time-consuming polygonal scale design that I used on my Giganotosaurus and Troodon drawings. I felt that I should make the scales as small as possible for this guy. Keep your pencils sharp.

Pachycephalosaurus

Pachycephalosaurus

Pachycephalosaurus wyomingensis was the last and largest of the so-called “dome-headed” dinosaurs. It measured fifteen feet long and lived 68-65.5 million years ago, right at the very end of the age of dinosaurs. Its fossils have been found in Wyoming (hence its name) and Montana, USA. The latter of the two localities is especially important, because this area is home to the Hell Creek Formation, a geologic formation which dates to the last days of the Mesozoic. It is within the Hell Creek Formation that most fossils of Tyrannosaurus have been found. It is possible that Pachycephalosaurus might have occasionally been prey for T. rex, but the presence of its foot-thick dome of solid bone and its sharp teeth-lined beak make this idea somewhat suspect.

The first remains of Pachycephalosaurus wyomingensis, which means “thick-headed lizard from Wyoming” were discovered during the 1850s in Montana. it consisted of pieces of the back of the skull (the squamosal bone) where there were several bony bumps. The eminent American paleontologist Joseph Leidy described this fossil, identifying it as armor, but he wasn’t sure what sort of animal it might belong to. He christened it Tylosteus (ancient Greek: tylos = “bump”; osteon = “bone”). In the first half of the 20th Century, two other fragmentary specimens were found, and in 1943, the name Pachycephalosaurus was created.

In the 1980s, it was realized that Tylosteus and Pachycephalosaurus were the same animal. According to the rules of the International Code of Zoological Nomenclature, the original name (Tylosteus) takes precedence, and any secondary names (such as Pachycephalosaurus) would have to be declared invalid.  In 1985, paleontologist Donald Baird was able to convince the ICZN to make an exception – to keep Pachycephalosaurus as its legitimate name and to discard the original name. He stated that the name Tylosteus hadn’t been used in over fifty years, and therefore shouldn’t be used. The ICZN granted his request, something that hardly ever happens! Usually, they are very “by the book”.

Pachycephalosaurus and its kind have generated a great deal of confusion and controversy since they were discovered. Most of the debating has pertained to their most obvious feature, their massive thick skulls. For a long time, it was assumed that these thick skulls were used for head-butting, like modern-day bighorn sheep. For years, paleontologists had an academic showdown over this idea, with some claiming that this idea was the only one that made sense, and others claiming that it was physically impossible for the animal to engage in head-butting behavior. For more information regarding this debate, you should watch the following two television programs:

Paleoworld, season 3, episode 3 – “Boneheads”. TLC, 1996.

Bizzare Dinosaurs. National Geographic Channel, 2009.

Now, the issue appears to be settled. Scientists at the University of Wisconsin recently conducted a study of various pachycephalosaur skulls from a number of different genera. If these dinosaurs did engage in some serious head-to-head combat, then their skulls would surely show some damage. After looking at over a hundred skulls, about 20% showed bone damage, specifically a condition called “osteomyelitis”, which is most commonly caused by trauma or injury to the bone. In other words, something hit it. For decades, the hypothesis that pachycephalosaurs engaged in head-butting has been conjecture. Now, we have the first hard evidence to support this idea. You can read more about their research and findings at the website article listed below.

“Study Confirms Head-Butting Behavior in Dome-Headed Dinosaurs”, by Natali Anderson (July 22, 2013). http://www.sci-news.com/paleontology/science-head-butting-dome-headed-dinosaurs-01247.html

The identity problem of Tylosteus and Pachycephalosaurus has resurfaced in recent years, but relating to different species. In the past few years, it has been proposed that two other pachycephalosaurs – Dracorex and Stygimoloch – are actually juvenile forms of Pachycephalosaurus. Watch the following videos for more information:

Dinosaurs Decoded. National Geographic Channel, 2009.

Bizarre Dinosaurs. National Geographic Channel, 2009.

“TEDxVancouver – Jack Horner – The Shape-Shifting Skulls of Dinosaurs”. http://www.youtube.com/watch?v=xYbMXzBwpIo

Lastly, it had been believed for many years that pachycephalosaurs belonged to a group of dinosaurs called the ornithopods. This is a very large group within Dinosauria, compsising hypsilophodonts, iguanodonts, and hadrosaurs (commonly known as “duck-billed” dinosaurs). This was because pachycephalosaurs appeared similar to these animals, especially the first on the list, the hypsilophodonts. These animals were bipedal, had beaks, and had front teeth – traits that were also present in pachycephalosaurs. However, recent re-examination of pachycephalosaur skeletons and cladistics have shown that they are not ornithopods at all; they are actually more closely related to the ceratopsians, the “horned” dinosaurs like Triceratops and Styracosaurus.

The drawing that you see here was made using a combination of shading and stippling, similar to my earlier drawing of Albertosaurus, but on a much smaller scale.

Albertosaurus

Albertosaurus

Albertosaurus, named after the province of Alberta, Canada, is one of the most well-known theropod dinosaurs. It is a distant relative of T. rex which lived in western North America approximately 75 million years ago (MYA). It was also one of the most wide-ranging, with fossils found from Alaska to New Mexico.

There’s another genus out there called Gorgosaurus. It used to be a species of Albertosaurus, but it was given its own genus distinction. Personally, I don’t think that the morphologic differences are that much to warrant a separate genus. Paleontologists are separated into “lumpers” (scientists who want to combine several different geni into just one genus) and “splitters” (scientists who want to take an established genus composed of multiple species and separate them into different genera). I’m kind of in the middle, but I’m leaning towards being a lumper.

Anyway, enjoy the drawing. Keep your pencils sharp.

Tyrannosaurus rex body

Tyrannosaurus rex body

It’s no secret that Tyrannosaurus rex had a large head – it measured five feet long! However, I’ve noticed that many paleo-artists have a tendency to make T. rex’s head too big in proportion to the rest of its body. Tyrannosaurus’ head was five feet long, but it’s body measured forty feet long. That means that its head was one-eighth the length of its body. That is very impressive. However, if we are to believe the physical proportions provided by some paleo-artists, it would appear that T. rex had a head that was much bigger, say around seven or eight feet long! That’s just ridiculous. The only Mesozoic carnivorous animals that have heads anywhere near those proportions are the gigantic “sea dragons” of the Mesozoic oceans – creatures like pliosaurs and mosasaurs. Here’s an example of an early drawing that I did of Tyrannosaurus rex in running pose. You’ll notice that it’s not as detailed as some of my later drawings, but that’s evolution for you – from simple to complex. Hope you enjoy.

Cretoxyrhina and Squalicorax

Cretoxyrhina and Squalicorax

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.