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Monthly Archives: March 2014

News: “Egg thief” dinosaur from Hell Creek FINALLY named!

All I can say is “It’s about time!!!”

After sitting around for years without an official description, a bird-like dinosaur found in the Hell Creek Formation has finally been given a name. I’m very happy about that. What I’m not happy about is the name that was actually chosen – Anzu wyliei, a name that I REALLY don’t find appealing.

Last year, I read that a bird-like dinosaur more commonly found in the Gobi Desert was discovered in North America. Furthurmore, I found out that it was actually on display in Pittsburgh, and had been for several years – it shows just how horribly behind the times I am. However, I was aghast when I learned that this creature didn’t even have a name. I asked “What the hell’s been taking them (meaning the scientists) so long?” Well now the wait is over.

Anzu (I’m actually shuddering as I’m writing the name – I just loathe the way that it sounds) was a member of a family of dinosaurs called Caenagnathidae. The caenagnathids were a sub-group within a super-family of theropods known as the oviraptorosaurs, or “egg thief lizards”. These very bird-like dinosaurs are well-known from Asia, especially China and Mongolia, but they are almost unheard of anywhere else. Oviraptorosaurs ranged in size from five to twenty-five feet long, and might have evolved from the ornithomimids, the “bird mimics”, commonly known as “ostrich mimics” due to their ostrich-like appearance. The most famous of them was Oviraptor, “egg thief” found in Mongolia by the adventurous Roy Chapman Andrews. The name came from the discovery of a partial skeleton lying on top of a nest of eggs. Chapman and his colleagues thought that the animal was in the process of plundering the nest when it was killed. It wasn’t until later when the insides of the eggs were carefully examined that paleontologists discovered that the preserved embryos were that of other oviraptorosaurs. This animal wasn’t preying upon the eggs – it was the mother.

The caenagnathids have had a confusing history, dating back to the early 20th Century. In the early 1920s, the famous paleontologist Charles W. Gilmore was fossil hunting in Alberta, Canada, when he found the remains of a new and strange creature known only from a pair of incomplete hands. In 1924, he gave them the name Chirostenotes pergracilis. Another dinosaur was named based upon an incomplete foot, and it was called Macrophalangia. By the late 1970s, scientists realized that these two animals were the same, and Chirostenotes became the official name.

But what sort of creature was Chirostenotes? It was clearly a theropod – a bipedal meat-eater – but the bone structure was unlike any other theropod known. In fact, it looked very bird-like. It was believed that Chirostenotes was most similar to another mysterious dinosaur called Elmisaurus, which came from Mongolia during the late Cretaceous Period.

For a long time, Chirostenotes was the only North American oviraptorosaur, specifically a caenagnathid. It was found in rocks dated to the Campanian Stage (80-70 MYA) of the Cretaceous Period. Then, in the 1960s, another oviraptorosaur – and a very early primitive one at that – was found, named Microvenator, “the little hunter”. It lived in Montana approximately 100 million years ago alongside Deinonychus and Tenontosaurus. This showed that oviraptorosaurs were present in North America for much longer than previously suspected.

It had been believed for a while that Chirostenotes and its kind had become extinct a millions of years before the dinosaurs’ exinction. However, in the 1990s, fossils of an animal which might have been an oviraptorosaur were found in Montana in rocks that dated to the very end of the Cretaceous Period – the famous Hell Creek Formation, the home of Tyrannosaurus rex. No oviraptorosaur fossils had ever been found there before. In 1994, Canadian paleontologist Phil Currie, an expert on theropod dinosaurs, published a paper on a fragment of a lower jaw found at the “Sue” site. Based upon it’s shape, it was obviously an oviraptorosaur, specifically a member of the family Caenagnathidae. However, this specimen was significantly larger than any previously-known specimens. It could have been a larger specimen of Chirostenotes, or it might have been a new species.

The problem was that Chirostenotes was known only from a few fragmentary finds – a complete or nearly-complete skeleton had never been found. Then, a pair of incomplete skeletons were found in Hell Creek, and were described in 1995. Ever since then, they have been housed in the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. The staff at the Carnegie Museum even took these two skeletons, composited them together, and put the creature on display for the public! However, the creature still did not have a definitive identification. Paleontologists were uncertain as to whether “the Triebold specimens”, as they were called, were Chirostenotes or maybe another larger species.

In 2011, Matt Lamanna and other scientists announced that they were studying the Hell Creek oviraptorosaur in more detail. Based upon a preliminary view, they stated that it was very similar to Chirostenotes, but they shied away from going so far as to claim that it was a distinct species.

In 2013, a team from the Burpee Museum (the same museum famous for “Jane”, which might be either a Nanotyrannus or a juvenile T. rex, depending on who you ask) discovered the partial skeleton of a caenagnathid oviraptorosaur near the small town of Ekalaka, Montana. The bones were so large that they originally thought that they had found a T. rex; Professor Thomas Holtz of Maryland rushed to the site and confirmed the animal’s identity. This specimen was even larger than the Triebold specimens in the Carnegie Museum. It was affectionately nicknamed “Pearl”.

In 2014, Matt Lamanna and three other colleagues published a paper on the Triebold specimens collected from North and South Dakota. After an exhaustive analysis of the bones, they concluded that the Triebold specimens were not Chirostenotes or Caenagnathus, but constituted an entirely separate genus. They called it Anzu wyliei. According to Lamanna’s own report, the dinosaur was named after Anzu, a feathered bird-like demon from Mesopotamian mythology, and measured somewhere between ten to fifteen feet long.

What the heck does a Mesopotamian demon, feathered or otherwise, have to do with a North American dinosaur? I can understand if the fossils were found in Iraq, but they weren’t. I would actually be highly surprised if ANY dinosaur fossils were uncovered in Iraq. It would be a lot more fitting if it was given a traditional Greco-Latin name, something like Dakotaraptor, or maybe even named after a being from native Sioux Indian folklore, like Wakinyanoraptor (“Wakinyan” is the Sioux name for the thunderbird sky spirit).

But then again, what the heck does the white-skinned feathered serpent god from central Mexico have to do with an unusually large pterosaur from Texas, which neither looked anything remotely like a serpent, nor had feathers, nor came from Mexico? I’m talking about Quetzalcoatlus, for those of you who haven’t caught on. So I suppose I shouldn’t be too harsh. Still, Anzu … it just sounds SOOOOO wrong. Unfortunately, we’re all stuck with it.

The specimen uncovered by the team from the Burpee Museum is also likely a specimen of Anzu.

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.

News: Jurassic megalosaur from Portugal officially described

Hot off the presses! A new carnivorous dinosaur from Portugal has been officially named – Torvosaurus gurneyi.

The fact that Torvosaurus came from Portugal isn’t a revelation – it was, after all, featured prominently in an episode of the Discovery Channel mini-series Dinosaur Revolution (which I didn’t particularly care for). For years, people have known that there have been megalosaurid dinosaur fossils from Portugal, specifically the Lourinha Formation, which dates to the late Jurassic Period, about 150 million years ago. These fossils were tentatively ascribed to the species Torvosaurus tanneri, known from the Morrison Formation of the USA. However, upon closer examination, there are a few minor differences in the bone structure, so the Portuguese specimens were named Torvosaurus gurneyi, named after the famous paleo-artist James Gurney.

Torvosaurus was one of the last megalosaurid theropods, as they were being replaced by the allosaurids and the coelurosaurids. Torvosaurus and its kind ruled Europe during the middle and late Jurassic Period. It measured 30-35 feet long, giving Allosaurus a serious run for its money, and possibly weighed somewhere in the realm of four to five tons.

As if this wasn’t news enough, there are some dinosaur embryos from Portugal which might belong to Torvosaurus as well.

For more info, check out the websites listed below:

AMNH Allosaurus photos

Recently, I have decided that my Allosaurus color drawing, which I have re-tooled about four or five times and felt so proud of, actually needs to be re-tooled again. I had made that drawing the center focus of one of my blog posts some time ago.

 

One thing that immediately jumps out at me is that the tail is too narrow – there’s just not enough meat on it. I’ve noticed that many paleo-artists who follow what I like to call the “Gregory Paul School” of paleo-art often have their paleo-critters very shrink-wrapped, especially the tails. The tail’s weight needs to be proportionate to the weight of the front half of the animal; a tail that is not thick enough will make the animal front-heavy, and I can safely say that this Allosaurus looks front-heavy.

The second thing that I have a problem with are the lacrimal horns. Those are the rounded projections on the skull just in front of the eyes. Many times, I have seen paleo-artists put very large or at least prominent fin-like crests on Allosaurus skulls. I have always been loathe to do this, since I am a stickler for anatomical correctness. If there aren’t any crests, I don’t put them on. However, when I was volunteering at the American Museum of Natural History (or AMNH as it is commonly abbreviated), I took various photographs of the two Allosaurus skeletons that they have on public display. Based upon this information, I knew that I needed to redo my drawing. I have decided to include the photographs here for any future reference for any aspiring paleontologist or paleo-artist.

 

Here is that dynamic running Allosaurus that everyone sees when they come into the entrance hall. I want you to take note of several things. First, look at that beautifully curved neck. Second, look how large the arms are in proportion to the body. Third, look at that enormous Baryonyx-esque thumb claw on each hand. Fourth, notice that the body is a lot more rounded than many artists often show, who make the body appear narrower and flatter.

AMNH Allosaurus entrance hall

 

Here is a close-up of the entrance hall Allosaurus‘ skull. I’m sorry if the picture looks a little fuzzy – I think I jerked the camera when I took the shot. First, notice that the jaws are strongly U-shaped. Second, the face is pretty much flat on both sides. This animal had absolutely no stereoscopic vision. Third, there does not seem to be any real three-dimensionality to the face – not a whole lot of wrinkles, ridges, and bumps, but almost flat.

AMNH Allosaurus skull entrance hall

 

I had a lot of trouble finding pictures of Allosaurus hands and arms for my drawing. So here’s one, so that you can get your proportions just right.

Allosaurus arm photo

 

Now we move into the Hall of Saurischian Dinosaurs, located on the fourth floor. This is the room that is always the most crowded, aside from the entrance hall, because here is where the Tyrannosaurus skeleton is located, and seemingly every elementary school child in all of NYC wants to see it. This is the skeleton of Allosaurus seen in that hall. You might recognize the pose as being similar to a Charles Knight painting, which has been endlessly copied ever since. The two Allosaurus skeletons in the AMNH are meant to represent two modes of behavior: predator and scavenger. There are two things that I notice right away. First, it’s brown not gray –  a rather superficial difference. But what jumps out at me is that the skull is a slightly different shape. The skull used on the skeleton in the entrance hall has an almost flat jawline, producing a rectangular-looking skull – this is the skull that is most commonly seen in museums and in dinosaur anatomy books. However, the skull that you see here has a more curvaceous S-shaped jawline, and the skull itself appears to be fatter and more robust than the one mounted on the entrance hall specimen.

AMNH Allosaurus skeleton 1AMNH Allosaurus skeleton 2

 

Here is another view of the skull (again, sorry if it’s a bit blurry; I really need to work on not jerking the camera).

AMNH Allosaurus skeleton 3

 

Here are some various views of that same skull from different perspectives. I took these shots because just having a side view doesn’t really tell me a whole lot of information. Again, you will notice that the skull is flat-faced with no stereoscopic vision. The only way that Allosaurus could see what was directly in front of it was if it cocked its head to the side like a bird so that one of its eyes could see something. Also, look closely at the rounded lacrimal horns. Notice those linear grooves running along the surface. That means that these horns were covered with keratin, the same stuff that your fingernails are made out of. Also, notice that the lacrimal horns are pretty-much in line with the post-orbital bones (the bones behind the eye socket). This would infer that the horns were not as pronounced as I had shown in my drawing.

AMNH Allosaurus skeleton 4AMNH Allosaurus skeleton 5AMNH Allosaurus skeleton 6

 

Lastly, here is another photo of Allosaurus arms. Look at the size of those thumb-claws!

AMNH Allosaurus skeleton 7

 

Neckless Wonders: Feeding Techniques of Dimetrodon and other Early Terrestrial Tetrapods

There’s been a lot of talk recently on David Peters’ blog “The Pterosaur Heresies” (http://pterosaurheresies.wordpress.com/) on early synapsids – vertebrate tetrapods with one hole in the skull behind the eye. I find this interesting since, as you can tell from the website’s title, Mr. Peters has a particular interest in pterosaurs – those flying Mesozoic reptiles that are often mistaken for dinosaurs.

Another creature that’s often mistaken for a dinosaur is Dimetrodon. If you’re an adult reading this, you may not recognize the name, but you’ll probably know it when you see it. Ask any 6 year old child, and he or she will immediately tell you what one looks like. It measured ten feet long, walked on four legs, had a distinctively-shaped head with almost S-shaped jaws filled with an impressive array of teeth, and its most obvious feature was that it had a huge sail on its back, probably for regulating temperature.

Dimetrodon grandis, one of several Dimetrodon species. © Jason R. Abdale. March 28, 2016.

If you want some more detailed info, Dimetrodon, meaning “two long teeth”, was a multi-speciate genus of carnivorous terrestrial synapsid amniote tetrapod, specifically a member of Spenacodontidae, which lived during the early Permian Period.

I can already tell some of you are going “Huh???” Let me see if I can explain this in regular English.

The name Dimetrodon means “two long teeth” in ancient Greek; it does NOT mean “two kinds of teeth” as you will sometimes see in books (then the name would be Dimorphodon, a name which is already used for a pterosaur – a nice David Peters segway there). The name comes from the two impressively long canines that it had on each side of its upper jaw.

Dimetrodon is the genus name; a genus is a group of related species. To be “multi-speciate” means that this particular genus contains many species. Examples of Dimetrodon species include D. grandis, D. limbatus (probably the most common species), and D. milleri. The exact number of Dimetrodon species varies, depending upon who you ask, because some people claim that certain names are invalid. The last time I checked, there were about fifteen or so different species spread out across the Northern Hemisphere from Texas, USA to Germany.

“Carnivorous” means “meat-eating”, and “terrestrial” means “lives on the land”, but I think nearly everybody knew that already.

As stated earlier, a “synapsid” is a group within a larger group of animals called terapods. The word “tetrapod” is Greek for “four feet” – tetrapods are animals which have or at one time had four limbs. These include amphibians, reptiles, mammals, and birds – wings count as limbs. Even whales and snakes are considered tetrapods because they are descended from animals which DID have four legs. Tetrapods are further sub-divided into amphibians (frogs, toads, newts, slamanders, etc.) and amniotes. An “amniote” is an animal which reproduces by laying eggs with hard shells which retain moisture. Inside the egg is a fluid-filled membrane called the “amnion” or “amnios”, which helps keep the developing embryo inside hydrated. While amphibians must lay their eggs in water to keep them moist, amniotes have the freedom of laying their eggs on dry land.

Amniotes are broadly catagorized into four groups depending upon how many holes they have in their skulls behind the eye socket and where those holes are located.

1) Anapsid – Greek for “no opening”; aside from the nostril and the eye socket, there are no other holes in the skull.

2) Synapsid – “fused opening”; one hole behind each eye, positioned low. All mammals, including humans, are synapsids.

3) Euryapsid – “wide opening”, one hole behind each eye, positioned high. Includes marine reptiles like nothosaurs, plesiosaurs, and ichthyosaurs. All euryapsids became extinct at the end of the Mesozoic Era along with the dinosaurs. NOTE: I’ve heard that the term “euryapsid” is paraphyletic, meaning that it’s an artificial group composed of many different kinds of animals that aren’t actually related to each other. But determining whether or not a group is paraphyletic is a subject for another day, and I won’t get into it here.

4) Diapsid – “two openings”; there are two holes in the skull behind each eye socket. Dinosaurs were diapsids.

Dimetrodon belongs to the synapsid group of amniotes, the one which includes mammals and the ancestors of mammals. So, in an extreme way, despite its lizard-like appearance, Dimetrodon is our great-great-great-great-great-great-great (and so on) ancestor!

In terms of how many groups of synapsids there were/are, there were/are many. One of them was a group called the “pelycosaurs” – you will often see Dimetrodon being referred to as a member of this group. The pelycosaurs first appeared at the end of the Carboniferous Period about 300 million years ago, but they really became dominant during the early part of the Permian Period, about 280 million years ago. There were many different species, but the ones which grab everyone’s attention are the sail-backed ones like Dimetrodon and Edaphosaurus.

The pelycosaurs were divided into four families, and one of them was called Sphenacodontidae, defined as a family composed of the genus Sphenacodon and all other animals that are more closely related to Sphenacodon than to other animals. The various genera that compose this group are generically referred to as “sphenacodonts”. Dimetrodon was a sphenacodont.

There, understand now?

Dimetrodon is often mistaken for a dinosaur merely because it’s prehistoric and looks dinosaur-ish. I want to show you a picture to see what I mean – it’s a pencil drawing by Vladimir Nikolov made in 2010. I’m not going to put the picture here because I don’t have permission from the original artist to publish it here. The picture is found on DeviantArt, but a word of caution – DeviantArt is known to have viruses, so I would highly suggest that instead of clicking on the link, you would instead google the image “Dimetrodon grandis Vladimir Nikolov”, and see what picture pops up in your search results. It’s a very good picture, nicely done from an artistic standpoint. I like the fact that, unlike the vast majority of paleo-artists out there, this person chose to show Dimetrodon in an active Komodo Dragon style way, rather than dragging its belly using four very scrawney limp legs. I also like the color scheme.

But there are three problems with this picture. First, I don’t think that Dimetrodon had scales of any sort. I read somewhere that preserved skin specimens actually show that it had tough leathery hide. But then again, if Dimetrodon really was a very ancient proto-mammal, you wouldn’t expect it to have scales, right? Second, he says it’s supposed to be Dimetrodon grandis, but based upon the shape of its skull, it looks more like a Dimetrodon limbatus to me – that’s the species that you’re going to see on display in most museums. Third, which is I think the most serious, Dimetrodon didn’t actually have a neck! If you were to look at any of the hundreds of Dimetrodon skeletons which are on display all over the world, you will very quickly notice that their skulls seem to be bolted directly onto their shoulders with no neck in between.

Now that I think about it, there are many examples of land-dwelling tetrapods  from the Carboniferous and Permian Periods which do not have necks, especially the pelycosaurs. I’ve seen skeletons of many pelycosaurs, either in real life or images in books and on websites, and I can safely say that NONE OF THEM HAD NECKS!!!

The absence of a neck must have had some very peculiar effects on how these animals moved and especially how they ate. A neck is a wonderful thing. A neck is a flexible apparatus which enables the creature that has it to do several things:

1) The neck contains the vocal cords. The vocal cords attached to the larynx of a longer neck will likely produce different sounds than a shorter neck.

2) The neck enables the head to move without moving the body. A head can twist and turn to see and to find food while the body can remain motionless.

3) Connected to #2, a neck enables the head to have a wide range of movement during the actual process of feeding. A carnivorous animal can chomp down on a carcass, and then twist and turn its neck so that its head can wrench off a large chunk of meat.

There’s no denying that Dimetrodon had some very impressive choppers – after all, it’s named after its teeth. It also had a very large solidly-built head in proportion to its body size, which must have given it a very hefty bite. However, the absence of a neck must have meant that it fed in a certain way. It could not attack the way that meat-eating theropod dinosaurs could with their elegant S-shaped necks, nor could they even attack the way that lizards or crocodilians (who also have short necks) could. Even crocodilians have longer necks than Dimetrodon and its Paleozoic contemporaries. Due to its large sail, a Dimetrodon certainly couldn’t “death roll” the way that a crocodile can (watch any episode of The Crocodile Hunter to find out what a “death roll” is).

Dimetrodon could probaby swing its head from side-to-side reasonably well to a certain degree, but it would have had limited up-down flexibility, maybe just enough to flick its head back a bit and gulp a piece of meat down. If Dimetrodon had a free fully-mobile tongue the way that some reptiles and mammals do like us, then swallowing food would be easier. However, if it had a fixed tongue like fish, amphibians, and crocodilians, then it would have to rely on flinging the food into the back of the mouth in order to swallow it.

Here’s how I hypothesize Dimetrodon fed. I think that once it got its jaws firmly into something, it either shook its head from side-to-side like a shark, or it could have braced the meat with its front paws and then pulled its entire body backwards, thus pulling a piece of flesh off of its prey. This would be an example of “puncture and pull” feeding. It certainly did not have the necessary head mobility or the height to enable it to do “hatchet attack” feeding, where the jaws are stretched as wide open as they can possibly get and then the upper jaw is literally slammed downwards onto the prey like a guillotine.

I am not particularly inclined to engineering, physics, or mathematics, so somebody out there has to do a 3D computer model study on skull and neck mechanics in order to replicate how Dimetrodon and its neckless ilk might have eaten. However, based upon observations of the bones alone and looking at how modern animals feed, I’m pretty sure that this is how the neckless wonders of the late Paleozoic would have eaten.