Happy mother's day, paleo fans! Hope you all got mom something special. Because if she was a reptile, chances are that less than 1% of you would survive to adulthood!

Now speaking of motherhood, it's time to honor the mothers (and fathers) of all mammals - I'm talking about those lovable creatures we call the Synapsids of the Permian period - a.k.a "that weird time before there were any dinosaurs which was full of odd animals nobody can pronounce but that are still cool ". Today we go on an artistic journey of epic proportions through the time of the Permian Synapsids, a group of transitional forms between reptiles and mammals - they have also been known as proto-mammals, stem-mammals, and (formerly) mammal-like reptiles. If you already are familiar with Synapsids, skip straight to the end of the post, because I have posted some new drawings of these creatures I'm working on. Nevertheless, curiosity seduces you and will not let go... so, onward!

By the way, despite all the vicious conspiracy theories circulating about me on the mammalophobic dino-art blogoshpere, this has absolutely *nothing* to do with the ArtEvolved crew deciding to form a Synapsid gallery. (lolz!)

The Permian, for those of you who don't know, was the time period right before the Triassic, and probably the most turbulent and volatile time in the ENTIRE history of vertebrates - warm-bloodedness evolved for the first time, reptiles were easily ten times more diverse (and deadly) than today, and entire superclasses of animals appeared and largely went extinct all within a few million years. A totally new tier of food chains emerged, and cold-blooded reptiles would never again dominate the land. Ancient continents were colliding, the climate changed at rates that would even shock the CEO of ExxonMobil, and at least twice, the entire large-fauna ecosystem of the planet was killed and reborn. And when the Permian finally ended, 90% of all life on earth - both on land and under water - was gone forever.

A miracle indeed that the direct ancestors of both dinosaurs and mammals survived unscathed, while larger and grander creatures dropped dead all around them.

Some of the oldest and longest-surviving groups of creatures - familiar faces like giant lungfish, trilobites, crocodile-sized amphibians, and even large groups of winged insects, disappeared almost entirely. There are many theories for the extinction - from climate change to volcanism, to seismic activity from continental collisions releasing trapped pockets of toxic gases under the ocean floor, to changes in ocean currents and weather patterns, to interspecific epidemics after the formation of Pangea (i.e. the Cortez phenomenon), and yes, even that oft-repeated favorite of K-T catastrophists, the inevitable asteroid impact! Of course, if ALL of these things happened together, then the death of 90% of living organisms is not too hard to imagine.

BUT, now let's go back to a time before the chaos, when the earth was rich and full of life, and life was simpler... (lol, I swear I'm probably ripping off the intro to one of Tolkien's stories without even knowing it). Here is the dirt on the Permian period and the Synapsids.

Enter the Permian. And the Synapsids.

1. A new kind of reptile

Around 290 million years ago, the earliest reptiles (or rather, "stem-reptiles" with little similarity to today's artificially classified "reptile" groups - and still bearing a resamblance to their amphibian ancestors) - diversified into several types.

*The Anapsids, had their jaw muscles entirely encased by a very compact skull. Thus there was not much room for muscle expansion, and they were restricted to developing short jaws and tiny brains - they sacrificed reach, leverage, and brain size to improve their limited biting power. They evolved into creatures like modern turtles, which all have short jaws with toothless beaks.

Turtle skull: an Anapsid -
note the total lack of holes behind the eye socket.

*The Diapsids developed two holes on either side of the rear skull, so that the jaw muscles that attached below could expand upwards and outwards without squeezing the brain. Many of the most successful animals in history have come from this lineage - Archosaurs, Crocodiles, Lizards (and subsequently snakes), Pterosaurs, Dinosaurs (and thus Birds) just to name a few. With the appearance of the first dinosaurs (and some would argue, even earlier Archosaurs) the Diapsida were permanently split into warm-blooded and cold-blooded classes.

The crocodile - a cold-blooded Diapsid

Velociraptor - a warm-blooded Diapsid

*The Synapsids developed one jaw-muscle hole on either side of the rear skull. In the earliest versions, the Pelycosaurs (Dimetrodon and its kin), the holes faced sideways, allowing outward (but not upward) expansion of the jaw muscles. As the jaw muscles started vertically from the lower jaw, they were forced to curve outwards in early Synapsids - a rather crude configuration that required huge jaw muscles for any decent amount of power, and equally large spaces to contain them - and not much was left for the brain. Initially, despite having a stronger bite and more jaw leverage than Anapsids, the very first Synapsids were at a disadvantage to the Diapsids, because unlike Diapsids, they did suffer from "squeezed brains" whenever they bit something. The mammals, which successfully conquered the "squeezed brain" problem, are present-day synapsids, though NOT all Permian synapsids were closely related to mammals.

Dimetrodon - a cold-blooded Synapsid

A horse (Equus), a warm-blooded Synapsid

There was also a fourth group called Euryapsids, who had a single pair of jaw muscle holes like Synapsids, but in a different position relative to the skull bones. Euryapsids became aquatic, and evolved into Ichthyosaurs, Placodonts, Nothosaurs, and Plesiosaurs. But they are often today classed as simply an early offshoot of the Diapsids who lost the lower pair of jaw muscle openings. The science of early reptile origins continues to be problematic, murky, and hotly debated (and in my view, badly mismanaged) - and where Euryapsids truly came from is not so relevant to this post, so - moving on!

The early synapsids, known as the Pelycosaurs, all had long torsos and tails, and the sprawling legs typical of cold-blooded reptiles (though they were totally unrelated to the diapsids we call "reptiles" today). Pelycosaurs split into five families, mafia-style. (Survival against their equally matched Diapsid cousins was an offer they couldn't refuse!)

1. Ophiacodontidae (long-bodied, primitive, and perhaps even aquatic - the earliest family)

Ophiacodon by Dmitri Bogdanov

2. Sphenacodontidae (the first carnivores to develop different types of teeth and reinforced jaws - Dimetrodon's group, which, like the Corleones, eventually wiped out the other four families! Other member of this family, like Sphenacodon and Haptodus, lacked sails.)

Dimetrodon by Raúl Martín

3. Edaphosauridae (plant-eaters with small heads and perhaps herd behavior - e.g. Edaphosaurus - which developed its dorsal sail independently of Dimetrodon)

Edaphosaurus by Arthur Weasley

4. Varanopidae (small carnivores named for their facial resemblance to Varanid [monitor] lizards - but they arose millions of years EARLIER! Perhaps chronologically, they should be called Varanids, and the monitor lizards should be called Varanopids instead!)

Varanops by Dmitri Bogdanov

5. Caseidae (very slow, pin-headed plant-eaters with freakishly huge bellies, sprawling legs no longer than those of the other families, and seemingly no natural defenses except, in a few cases, SIZE).

Skeleton of Cotylorhynchus, the biggest of the Caseids,
at the Oklahoma Museum of Natural History

All of these groups were a leap forward from the Anapsids and proto-reptiles of the Carboniferous, but they still faced a problem - their cold-blooded metabolism made them slow and inefficient for terrestrial life, and their squeezed brains were an added disadvantage.

But within a few million years, the early cold-blooded synapsids like the sail-backed Dimetrodon and Edaphosaurus were dead, replaced by the first warm-blooded synapsids - and the first warm-blooded creatures in the earth's history. They were likely descendants of one of Dimetrodon's Sphenacodontid cousins (some say it was certainly Haptodus, though I say "prove it!"). These new Synapsids were known as "Therapsids" ("beast-holed faces"). And their jaw muscle holes were rotated more upward than those of Pelycosaurs. Upward AND outward expansion in a single hole allowed the skull, mandible, and brain to grow wider and larger. The "squeezed brain" problem was history. A larger brain allowed for more development of the senses, including hearing. In the new Therapsids, the rear bones of the jaw slowly began to shift toward the ear canal, and developed into complex structures to aid hearing. It marked the transition between the reptile's single ear bone, and the three-boned inner ear of the mammal. The Therapsids, initially small and insignificant, overran the still cold-blooded diapsids and spread all over the Earth. Better hearing and sharper senses made these creatures better hunters. The world quickly became a scarier place.

2. The Kazanian Revolution

Not only did the independence of Therapsid predators from sun-basking allow them to decimate many early diapsids, but the Therapsid herbivores also outcompeted their reptilian counterparts, scaling steeper inclines and feasting in forests out of the reach of most reptiles. They became more erect than their sprawling ancestors, and some grew to huge sizes, with the biggest - such as the African genus Moschops, tipping the scales at over a ton. Not very big by dinosaur standards, but it dwarfed most every land vertebrate that came before it. Its biggest enemy was another Therapsid, the similarly huge Anteosaurus, a predator that was nearly mammalian except for its lack of molars.

Moschops by Dmitri Bogdanov

Anteosaurus by Dmitri Bogdanov

These creatures lived in the Kazanian epoch (which has been called by at least a thousand other names depending on which country you're from), a few million years after Dimetrodon. The Kazanian Therapsids, were true "proto-mammals". They had an erect or semi-erect posture, warm-blooded bone microstructure, and grew to large sizes quickly. The Kazanians were not known to have hair, but neither have scale impressions been found with them. Their skin type is unknown, but most artists conservatively restore them with non-scaly, naked skin like many large mammals today. There were both large and small Kazanians, but of course the big ones come to mind first. Their strongholds were high-latitude areas like present-day South Africa and Russia - areas which even then were relatively dry and had extreme climates, off limits to most reptilian cold-bloods.

3. The Tartarians

The Kazanians disappeared altogether within a few million years. Never again would Moschops graze the ferns of the Karoo basin. Nor would its Russian cousin Ulemosaurus ever roam the plains of Kazan. Only some of their tiny and very distant cousins survived. The Dicynodonts, a branch of a insignificant family of small Kazanian therapsids that lived in the shadow of the Moschops-like forms, weathered out the mass extinction and grew larger to fill in the niche of top herbivore. They also did away with the incisors of their ancestors and grew tough beaks for grazing, as well as tusks for fighting. The top carnivore niches were filled by the Theriodonts, a cluster of three groups of fast, fanged, and probably hairy predators: Gorgonopsians, Therocephalians, and Cynodonts - the group which branched off into the first mammals.

Various Tartarian therapsids - those with deep snouts and long fangs are Gorgonopsians.
Drawings by mojcaj.

This epoch of lumbering, beaked plant-eaters and furry, wolf-like hunters was called the Tartarian (again, it's ridiculous how many other names this timespan has been given in different countries). The Dicynodonts and the three clans of Theriodonts managed to fill nearly every niche the Kazanians had left vacant. Yet this time of diversity was also beginning to be plagued by a global decline. The continents were joining together as tectonic plates collided. Increased volcanic activity, earthquakes, and warmer ocean currents emerged, and the weather patterns became increasingly dry, leaving the newly-formed supercontinent Pangaea a barren wasteland. Fish stocks plummeted. Amber deposits from that time indicate the presence of huge amounts of deadly hydrogen sulfide gas, perhaps from increasingly disturbed undersea volcanoes and fissures. The Tartarian Therapsids may have simply choked to death on fumes. And - well, we can never rule out the possibility of an asteroid for good.

Gorgonopsians, like the saber toothed cats that mimicked them much later, went the way of - well - the Dimetrodon! The ancient trilobites in the sea bit the dust after nearly 300 million years of survival (including at least two earlier mass-extinctions). The water was too toxic for most fish and shellfish. And on land, the warm-bloodedness of the therapsids, which had ensured their supremacy for millions of years, placed costly energy demands on them that doomed them to certain destruction in a continent increasingly parched and devoid of food. The smallest of Cynodonts, Therocephalians, and Dicynodonts were the only therapsids that survived the annihilation of their once grand clade.

The Triassic - Pyrrhic recovery and submission

The diapsid reptiles, on the other hand, flourished. They quickly evolved into a group called Archosaurs, whose first wave, the Pseudosuchians or "False Crocodiles", dominated the land and eventually the water as well. From the big headed Rauisuchian carnivores, to armor-plated hebivores like the Aetosaur Stagonolepis, to crocodile-mimic Phytosaurs, and even true crocodiles themselves, the Archosaurs did the Therapsids one better - they managed to survive in Pangaea without true warm-bloodedness, and often grew to large sizes that would retain heat without needing to move and eat constantly - the so-called "lukewarm metabolism" or mass-homeothermy. The crocodiles, following the Phytosaur model, became patient river ambush predators and gave up any semblance of energy-hungry warm-bloodedness entirely, though they still retained four-chambered hearts. The Archosaurs as a whole became an entire ecosystem, diversifying to fill every niche, until the Therapsids were beyond hope of survival.

The few remaining therapsid families to survive the Permian mass extinction had paid a high cost. Much of their foothold on land had been lost to Archosaurs. Pushed by evolutionary competition, a few cynodonts were desperately beginning to show potential aquatic tendencies, but before they could evolve to populate the rivers, the Archosaurs had already filled those niches - and wiped out these "proto-otters" before they had a chance.

The Dicynodonts once again emerged and grew to huge sizes rivalling the long-dead Kazanians, but their best days were truly behind them. Their warm-blooded metabolism did not automatically translate into speed or agility, and many of them were too ravenous to survive in low-biomass areas (where reptiles thrived), yet too ponderous to outrun the big predators which often hid in more lush, dense vegetation. Slow and ungainly, they became fodder for fast-moving Rauisuchian hunters. Once the Pangaea climate became more stable, the Cynodonts downsized and evolved all the basic features needed to become true Mammals, submitting until further notice to the terror of the larger and stronger Diapsid nemesis, while the over-specialized Dicynodonts, relics of a bygone era, were unwittingly wiped out in the Archosaur-dominated frenzy.

The Triassic Takeover: Archosaurs (in black) drive the Cynodonts and Dicynodonts (in white) into extinction in every major herbivorous and carnivorous niche. Near the top you can also see some early dinosaurs like Dilophosaurus, Heterodontosaurus, and Plateosaurus.
(Image from Bakker's 1986 book The Dinosaur Heresies, p. 417)

Within a few more million years, the Archosaurs, who had driven the therapsids to the brink of extinction, were themselves threatened by a group of their seeminly insignificant (and strangely bipedal) relatives - the first Dinosaurs. And when warm-bloodedness re-emerged in full force with the dinosaurs - it was here to stay.


... so without further ado, here are my new drawings of Permian Synapsids (I hope to add more when I'm not working on dinosaurs and other things...)

The Hunt: A pack of Inostrancevia take down a Scutosaurus

Inostrancevia was the largest of the Gorgonopsians, hailing from Russia and growing to the size of a large bear. Its prey included the even more massive Scutosaurus, a huge, slow Anapsid reptile that ate ferns and other low-growing plants. Inostrancevia has long been m y favorite protomammal ever since I saw the PaleoWorld series on TV back in 1995 (and for those of you that remember it... that show was an absolute masterpiece in every way). And I always imagined Gorgonopsians - the big ones anyway - to have been pack hunters like lions and wolves today. Now some of my more conservative colleagues will say "no, they didn't have the brain power to coordinate a pack hunt" or "they were just too primitive to pull it off" or "why the hell are you giving them fur and whiskers and the ability to jump?". These are empty complaints at best. Remember, my intention is to show them as believable living creatures, based on the best current information about their anatomy and phenotype - not as an outdated monograph of some naturalist textbook from the Darwin era. Much of the prejudice against pack-hunting protomammals comes form the outdated assumption that they were cold-blooded reptiles.

But even most warm-blooded predators today are not pack hunters, and ironically, cold-blooded crocodiles and monitor lizards will swarm a struggling victim even though they are not launching a pre-meditated strategy - and they do not compete with each other until after the prey is dead. Even the most primitive therapsids would have had at least that much collective hunting ability.

And of course hairy Gorgonopsians look far more beautiful than scaly ones.

Portrait of Estemmenosuchus mirabilis

This is clearly a work in progress. I deliberately over-darkened this image (as you can tell from the filled-in portion of the cheek flange) so the outlines would become more visible. I'm obviously nowhere near finished on this one, and it took a lot of wrangling with various photographs and estimating the skull's uncrushed shape, to finally get the proportions right. I plan to put a lot more textured detail on the "crown" and the cheek flanges.

Estemmenosuchus mirabilis was a Kazanian epoch therapsid, a relative of fellow-Kazanian Moschops, and almost as big. Both creatures belonged to the suborder Dinocephalia, and were among the earliest creatures adapted to ritual head-butting behavior. Their new status as warm-blooded animals meant more energy for mating rituals and more competition among males. While some Dinocephalians, like Moschops and Ulemosaurus, simply grew thickened skull domes, Estemmenosuchus took headgear in a far more radical direction. It had two ornate crown-like bone structures above the eyes, two huge horizontal cheek flanges, large fangs (certainly for fighting, or else this creature, which had the back teeth of a primitive plant-eater, may have actually been an omnivore) - and it even sported a small nose horn, a feature that would not re-emerge until the heyday of the Dinosaurs. Out of all these structures, the cheek flanges were the largest. Another species, Estemmenosuchus uralensis, had smaller and rounder flanges (some suspect the two species are simply males and females of the same animal). The "third eye" (actually a scale-like gland) was also large.

There is a scarcity of decent restorations of this beast. In fact, I can recall only ONE picture of Estemmenosuchus that really looked believable to me, and that was a vivid gray-and-red painting by David Peters done for a monumental timeline-book of dinosaurs and other extinct animals. The book is almost certainly out of print, I don't remember the title, and the painting is nowhere to be seen on the web (David Peters himself, though a very talented artist of the first caliber, seemingly ruined his career by promoting some wildly speculative and unscientific restorations of Pterosaurs which the paleo-art world has done its best to avoid and disown - though I prefer to remember the far better work he produced in the 90's).

Caught Red-handed!
Today, I don't see any recent restorations of Estemmenosuchus that can really be considered "high-fidelity" so I am doing the first one. I know some will disagree and point to John Sibbick's drawing of the creature - with its slit lizard lips, vacant dunce-cap stare, and seemingly frozen jaws. But this is more like a monument than a live portrayal of the real beast (interestingly, I've seen Sibbick's drawing wrongly attributed to Gregory Paul on at least two websites, like this one - even though it's pretty easy to tell that his style is nothing like Paul's). Sibbick has a flair for extremely detailed 3D textures, but he has often made anatomical errors in his work, particularly with sauropods and ceratopsians - and now, a therapsid. Raúl Martín also did a painting of Estemmenosuchus, which, unlike most of his work, looks nothing short of comical. Fabio Pastori also tried his hand at Estemmenosuchus, which, aside from the overdone neon-purple airbrushing, is a direct ripoff of Sibbick's version, down to the same nostril shape, crown shape, mouth, and even the ends of the cheek flanges! Now I'm not interested in bashing other artists - but this case is truly sad; on his website, the guy doesn't even give Sibbick a smidgen of credit for the original! Not to mention the only noticeable differences are those strange pustules on the throat, and the excessive amounts of drool - more like some sort of fantasy dragon than a realistic therapsid. Hey, I call 'em like I see 'em. And Sibbick's drawing has been around a lot longer. (BTW, I personally think neon purple just looks tacky.)

John Sibbick ....................... and Fabio Pastori

They both have the same flattened appearance and straight-edge lips to the skull, which matches neither the fossils nor the original monograph engraving (shown HERE). And both restorations also ignore the fact that large Dinocephalians had a sharp head-neck angle - so that Estemmenosuchus rarely (if ever) held its head with the snout pointing straight forward like that. Like Moschops, its head was held nose-down: a perfect all-purpose position for feeding, drinking, charging, and head-butting. Sibbick and Pastori would do well to look closer at the actual skeleton and how it articulates.

So I will be following the actual skull far more closely, to produce a completely original (and far more accurate) drawing of Estemmenosuchus. Based on the scar ridges on both the dentary and mandibular regions, this animal also had primitive cheeks - whereas all extant "restorations" (like Sibbick's and Pastori's) lack them entirely. Cheeks, after all, started out both in mammals and dinosaurs, as humble extensions of the jaw adductor muscles, which were already quite prominent in the earliest Synapsids. Here is a skull photo (I've had to enhance some details and shading due to the bad resolution, but rest assured I didn't add any features that weren't already there).

Estemmenosuchus mirabilis skull - red ovals clearly indicate where the attachment ridges for the cheek muscles are. These early cheeks probably did not have as much capacity as those of modern mammals, but Estemmenosuchus certainly did not have naked gums or skinny lizard lips. However, it evolved its cheeks independently of true mammals (i.e. Cynodont descendants).

So yeah.... cheeks.

Next week it'll be back to the dinosaurs, but I hope to finish Estemmenosuchus and some other therapsid images pretty soon. So keep checking this post.

More Ceratopsian Madness!!!

Posted by Nima On Monday, May 4, 2009 11 comments

Hey everyone, it's been a messy past few weeks so progress was literally snail paced. I was sick with the flu, my computer was infected with spyware (and had to be rebooted) and I had a mess of exams and other issues to tackle...

But I did want to get some artwork done, and the fact that the ArtEvolved blog seemed a bit lacking in Chasmosaurs for its Ceratopsian Gallery just screamed out for attention. Chasmosaurus itself has always been my second favorite dinosaur (after Brachiosaurus) and it's a fitting challenge for a high-detail illustration.

And instead of simply being ripped apart by a predator, I wanted to show this ceratopsian fighting back.

I'd had this image in the back of my mind for a while, a Chasmosaurus charging at a predator whose attack failed. Lunch strikes back. This concept was actually inspired by a drawing John Conway did, of Chasmosaurus belli chasing away a Daspletosaurus torosus. You can see his drawing HERE.

And the image stuck in my head. This was one of those pieces where you just look at it and you get this insane burning desire to do something like it, only with your own personal twist. I HAD to do something like that. And it would HAVE to be better than Conway's already impressive version (at least to my eyes). Now Conway's work is under a creative commons license that requires you to credit the artist if you "use" his work - so this would technically be illegal if I didn't give him credit. So of course I will. The dinoart community, as small as it is, doesn't need any lawsuits - no Sue fiasco, and no Archaeoraptor either.

Only thing is, I planned to change the Chasmosaurus belli to a Chasmosaurus kaiseni (which I still consider a separate species) because I wanted something with much more impressive horns.

Above: skull of Chasmosaurus kaiseni.

Below: Chasmosaurus kaiseni in the foreground, compared with Chasmosaurus belli in the background (both skulls are in the AMNH).

I also decided to replace the Daspletosaurus with an Albertosaurus, which was more common at that time in Chamosaurus's Canadian habitat. Aside from that, I'm not a particularly big fan of Daspletosaurus getting chased by its prey... not really sure why, but for the dynamics of the scene, Albertosaurus just looks better in my mind. I'm NOT a follower of Dale Russell's theory that Daspletosaurus was the main predator of horned dinosaurs while Albertosaurus stuck mostly to duckbills (I don't buy most of Russell's theories period, but that's another story). And nothing screams 'Alberta' like Albertosaurus. So I replaced the Daspletosaurus with a subadult Albertosaurus libratus.

Thus I completely replaced the head (BTW, in any case the original head doesn't exactly resemble Daspletosaurus either - it's a lot shallower and more crocodylian than the actual skull of Daspletosaurus - and the notch in the upper lip just looks odd on any advanced tetanuran - it's almost Dilophosaurian up close! For reference see below...)

Left: Daspletosaurus skull. Right: John Conway's Daspletosaurus. I marked both with diacritical lines added to show the discrepancies: Red = lip line: smooth in the skull, notched in the drawing. Pink = depth of the skull about halfway between the eye and the nostrils: unusually shallow like a croc or phytosaur in the drawing. Yellow = depth of lower jaw at a position corresponding to the lacrimal bone in the upper skull: moderately shallow in skull, unusually deep in drawing). Green circles = orbital horns: small, unfused, and upward-pointing in the skull, but wide, flat, and and fused in the drawing. Blue line = incline of snout just below preorbital ridges and rugosities: steeper in the skull than in the drawing, which is the only possibility considering the proportional differences in snout depth!

Of course the skeptical can always look at the untouched originals. Conway's piece is indeed detailed, well thought-out and very skillful in perspective... it's just not Daspletosaurus. Yes I know I'm being harsh; it's nothing personal, just the art. John Conway is overall a very accomplished and talented artist who I'd probably say easily outranks 95 % of paleoartists out there - his Daspletosaurus, for all its errors, is far more accurate than, say, the work of Ely Kish or Josef Moravec (...don't even get me started...). Of course, such critiques of my own work are equally welcome. It's how we all improve.

But back to Albertosaurus: it was a more common predator, had a longer snout, and is relatively easier to draw. The body was pretty similar to Daspletosaurus, but more slender - though in this seemingly subadult stage depicted in Conway's drawing, they would both have been of similar physique.

*** A NOTE ON ALBERTOSAURUS: Phil Currie and a few other paleontologists have recently re-labeled A. libratus with its original 1920s name, "Gorgosaurus libratus" - though going on Gregory Paul's more reliable classification, I decided there isn't enough difference between A. libratus and the type species A. sarcophagus, to kick the former out of the genus Albertosaurus.) I still think there are enough similar derived traits between A. libratus and A. sarcophagus to consider libratus as a member of Albertosaurus.***

Long story short, I first emailed Conway to make sure it was okay to draw the scene with the changes I have described above. He replied that it was fine, and even claimed that he probably didn't own the poses of the dinosaurs in his image... in any case he seemed pleased that I would give him credit for the original concept.

After that, I started work on the drawing. There were a number of mostly small issues that needed resolving.

*First I lengthened the predator's tail (based on the most current skeletal proportions of Albertosaurus; Daspletosaurus skeletons also had similar proportions, and Conway's Daspletosaurus seemed unusually short-tailed, and the tail looked a bit too stiff).

*I reduced the rather extreme and improbable angle of the predator's head-turning (as well as raising the head and making the neck larger) - in any case, both Albertosaurus and Daspletosaurus had eyes that faced sideways, so the ideal head position for the predator to keep its eye on the charging Chasmosaurus would be a profile.

*I curved the end of Chasmosaurus's tail more upward to stay clear of its hind legs

*I added a skin flap to enclose Chasmosaurus's shoulder retractor muscle (latissimus dorsi), which itself seems strangely absent in Conway's version.

*I also added skin flaps for the caudofemoralis muscles on both animals (look at Greg Paul's 1988 T.rex pair painting to get an idea of how this would look from behind).

*I lowered the angle of the predator's arm and made it larger to properly scale with the body (the arm angle and size on the Conway original looked more Abelisaurian than Tyrannosaurian).

*I gave the predator an open mouth with tongue showing (as if panting).

*I put sharper outlines on the Chasmosaurus frill studs and other small facial features.

*I enlaeged the corner studs on the frill (as well as re-scaling their perspective and the rest of the upper frill).

*I altered the stance of the Chasmosaurus's hands and fingers, to a more impact-absorbing one (the dinosaur is jumping and eventually will have to land on its fingers, not its carpal bones).

*I did a TOTAL redesign of the skin textures for both animals - more detail, more wrinkles, and smaller scales. I also kept in mind the presence of a very rich skin texture of large scute-scales surrounded by smaller ones for Chasmosaurus, based on known Ceratopsian skin impressions - Conway's Chasmosaurus seems unusually smooth considering this.

*I also put some substantial patterns on both animals - stripes for the Albertosaurus, and blotches for his ceratopsian foe.

*I redrew the body of Chasmosaurus to be more in line with the creature's likely musculature (Greg Paul's Chasmosaurus muscular diagram published in Dinosaurs Past and Present (1987) was a very useful reference in this regard). The result was more blocky than Conway's version.

*I drew the segments for the fleshy pads under the Chasmo's toes (you'd think this is easy, but it was insanely tedious. The pads would more or less follow the pattern of the toe bones - but finding a good picture of ceratopsian toe bones was a major pain in the phalanges!) As each toe had a different number of bones, the number of pad segments was also likely to have varied. I also made the Albertosaurus's toe pad segments more defined.

Above is John Conway's drawing from his Paleontography website.


BELOW is my initial sketch.

And further below, is my progress so far. Click on the image to see the full detail. Albertosaurus is finished except for the tongue, the teeth have been redone from the initial sketch to match the skull of A. libratus. Also notice the sharper angles in Chasmosaurus's spine and torso relative to the initial sketch.

Pretty much all that's left is the tongue and the Chasmosaurus's rear half. I hope to finish this soon. And thanks to Mr. Conway for creating the original drawing, being totally cool with my reinterpretation of the scene, and answering my questions.