Wednesday, August 26, 2015

Palaeo-Study: What's with all these feathery theropods?

((Author's Note: As my debut post here, I'd like to make my own little series called Palaeo-Study; where I will discuss more serious topics that wouldn't fit into a Paleo Profile, but deserve their own posts. As such, this is not going to be a short post. Enjoy!

As many are likely aware, palaeontologists have considered birds to be direct descendants of the theropods for a very, very long time. This is, obviously, because of the taxon known as Archaeopteryx ("first wing"), which was first described in 1861 by Christian Erich Hermann von Meyer.

Archaeopteryx reconstruction showing what we know about the animal.
Credit for the image goes to Nobu Tamura.

This small dinosaur has caused a bit of a cladistic controversy for decades; palaeontologists have been split on if it was a true avian, albeit the most primitive of them, or if it was a highly bird-like maniraptoran. Currently, consensus seems to be on the former, though it remains under debate.
The genus has also played a pivotal role in solidifying the concept of evolution as the palaeontological consensus; as it has both features of more advanced true birds (pennaceous feathers and a mostly-feathered body) and traits of non-avian maniraptorans (teeth, clawed fingers).

However, for as pivotal as this genus is, this also means that it has caused a fair bit of controversy, especially for those who do not believe in abiogenesis or evolution as the origin of life. An animal with traits of two types that these people distinctly separate disrupts their faith; and they either say it's a bird and nothing more or, in more extreme cases, call it a hoax fossil (likely in reference to the actual hoax fossil that was called "Archaeoraptor"). There are multiple factors that separate the two, however;
  • Archaeopteryx was found in Germany, while "Archaeoraptor" was found in China, a location known for it's instances of bootleg or faked fossils.
  • Archaeopteryx is known from multiple well-preserved specimens that clearly could not have been Frankensteined together. "Archaeoraptor" was made of multiple, quite damaged specimens that looked as if they were patched together.
  • Archaeopteryx was Late Jurassic, while "Archaeoraptor" is just an assortment of Cretaceous animals stitched together.
As for other feathery theropods, ones that people often bemoan and ridicule are Velociraptor and Tyrannosaurus; both due to bias. Feathers get commonly associated with things like chickens, which are considered derpy, stupid meals on legs. Meanwhile, scales get associated with dragons, which are seen as awesome, powerful beasts. The comparisons are unfair, obviously; why compare a mild bird like a chicken to a powerful monster like a dragon?

Again, the answer is bias; people want to "show" how ridiculous feathers on dinosaurs are, and so say that it makes them look like giant chickens instead of badass prehistoric dragons. But this isn't the case; a fully feathered Tyrannosaurus running at you is always going to be just as scary as a scaly one doing the same, because while we may say we have a preference, the fact is that our instinct will tell us what to do regardless of the animal's integument. This is also why people find bears scary when one runs at them, but not when looking at photos; it's the fight-or-flight response in action.

A good example of this sort of mental conditioning is Jaws, and the impact it had on sharks in the public eye. Jaws was a masterful horror movie, but it inadvertently caused a wave of fear-mongering that has yet to subside, and caused many to vilify sharks. The same is, in some manner, true in this instance; people fear-monger that feathered dinosaurs look "stupid" and "not scary", and thus they aren't immediately profitable, so movies don't make them look cool and scary, rinse and repeat ad infinum

To put it another way...if it was actually happening to you, you wouldn't care about how feathered-up that T.rex was, you'd just want to get as far away from it as possible. Feathers are not inherently "less scary" than scales; it's just people are conditioned to think they are. Popular culture certainly doesn't help the image, either; when what Hollywood considers "good" is a good 5-10 years behind what we'd find acceptable, that poses a big problem to scientific accuracy (then again, nobody in Hollywood seems to give a brontosaur's backside about that anyways... :p). 

In terms of phylogeny, we know 100% that most all coelurosaurian theropods had some amount of feathering. How extensive it was varies, but all known coelurosaurs have feathers; this is undeniable fact. For example, we know Velociraptor had pennaceous feathers on it's arms (that is, arms with a central shaft, like birds) due to quill knobs left on the forearm of specimens, was but the size of an ocelot...and was, to be blunt, quite stupid and couldn't run fast at all; but of course, popular culture would have you think they were leathery, lightning-quick, man-sized superpredators smarter than whales, dolphins and some primates. And that's not even getting into the other issues that movie has.

All coelurosaurs, including tyrannosaurs, had feathers. This is not for debate, it's pretty much confirmed at this point. Technically, feathers may spread back into the base of Archosauria (or at least Avemetatarsalia), as modern alligators carry the base genetics for creating feathers in their DNA, just rendering them into scutes instead. This suggests feathers (or at least some kind of filamentous structure) are a basal archosaur trait, and that crocodylians shed them (turned off the gene) as they became more adapted to a semi-aquatic lifestyle, and likely closes the notion that the two structures are separate genes. In essence, crocodile scales....are really very primitive forms of feather.

So really, this could just mean all dinosaurs have the possibility of possessing feathers, as they would all have to have beta-keratin. If they did is uncertain, that they could is. And it's not like feathers are detrimental; after all, feathers give our fine dromaeosaur friend the power to run up walls and lets him pin his prey and eat it alive; surely, those can't be considered "weak" and "dumb" abilities?
So chin up about Velociraptor being enfluffled! It just makes it so that you literally have no escape from it other than shooting the darn thing.

Or running quickly.

Either way, it's more dangerous than the roid-rage super raptors we see in pop culture in terms of terrain adaptability. Not even the walls are safe!

Editors' note: It is important to remember that rarely anything in the field of Paleontology can be considered absolute. Velociraptor was almost certainly feathered, but the debate whether or not T. rex was remains controversial. For evidence in favor of scaled tyrannosaurs, refer to here (check under 'Yutyrannus the tyrannosaur?' and 'The Feather Scale Dichotomy')  -

Author's reply: While it's certainly plausible that more advanced tyrannosaurids did undergo some amount of feather reduction, the benefits of feathers in a thermophysical sense is too much to suggest that all or even most of their feathers became reticulae. The most accurate conservative depiction of the genus is the newly revamped design in use by the game Saurian, which can be seen here.

However, evidence is leaning towards a subtropical climate for Hell Creek, and an average temperature not that far from the Yixian's, which may suggest that either Hell Creek had a consistent cold period or that it was overall cooler than we've predicted. Even if it was subtropical, more feathers on the animal make it more effective at thermoregulation than an unfeathered animal. I may decide to make a post showing how common arguments for naked tyrannosaurs are flawed sometime in the near future.

Saturday, August 22, 2015


Dinosauria would like to welcome our newest writer, Justin Banner! Take it away, Justin!

Hello, fellow dinosaur fans! I'm Coelophysis here. I was mentioned in a post regarding paleoart here under my real name, Justin Banner. I am proud to say I am now a proud part of the Dinosauria family here, alongside RaptorRex.

As an avid paleontology enthusiast and unprofessional paleoartist, I feel the need to enlighten you with as much Dinosaur-related stuff as I can. So I hope you all enjoy my being here, and my up-and-coming contributions to this blog.


- Coelophysis

Tuesday, August 18, 2015

Paleo-Profiles: Albertosaurus/Gorgosaurus

Author's note: Raptorrex here, thought I'd try something new out. Basically, Paleo-Profiles are biographies of prehistoric animals. More often than not, the animal addressed correlates to the previous post. Example: If I were to review a book about Tyrannosaurus, then the Paleo-Profile would be T. rex. The main goal of this project is to give information for school projects and such. Expect these to come once a month. 

Image Credit: Luis Rey

 Name: Albertosaurus 
Species: A. sarcophagus
Discovery: Osborn, 1905
Geologic era: Campanian of the Late Cretaceous
Geographic area: Canada/USA
Family: Tyrannosauridae of the suborder theropoda

Name: Gorgosaurus
Species: G. libratus
Discovery: Lambe, 1914
Geologic era: Campanian of the Late Cretaceous
Geographic area: Canada/USA
Family: Tyrannosauridae of the suborder theropoda

Albertosaurus, one of the best-studied tyrannosaurids to date, lived during the Late Cretaceous of North America, with a habitat ranging from Alaska all the way down to Texas. Like most other tyrannosaurs of its time, Albertosaurus is characterized by a sleek build, triangular horns above its eyes, and remarkably short arms. Based on current fossil evidence, we know that Albertosaurus (as well as Gorgosaurus) was a particularly common predator during its time. In Alberta, Canada, the Dry Island bonebed has allowed paleontologists to uncover more than 25 different individuals of varying age. Not only have the findings shown that Albertosaurus populations were abundant, it has also been a revolutionary change in the way tyrannosaur behavior has been proposed. The idea of tyrannosaurs living and hunting in packs was first hypothesized by Dr. Gregory S Paul in his book Predatory Dinosaurs of the World, alluding to the behavior of the big cats today. Actual fossil evidence for this hypothesis would be found in the late 90's by a team led by Dr. Philip Currie of the Royal Tyrrell Museum. At the very least, Albertosaurus lived in small families, possibly to protect their young.

Gorgosaurus (bottom) and Albertosaurus (top)
Image credit: Fabio Pastori

Gorgosaurus was discovered a little less than a decade after Albertosaurus, again, in Alberta. Gorgosaurus follows the same body structure of other tyrannosaurids, though the eye sockets are rounder on Gorgosaurus than that of other tyrannosaurids. Like its larger contemporary cousin, Gorgosaurus is extremely well-studied, with multiple specimens having been found. Skin impressions belonging to Gorgosaurus show a texture like that of modern birds. Although no evidence of feathers have been found, it is assumed that Gorgosaurus was covered in plumage in at least one growth stage. 

Gorgosaurus did not live a happy life. Many specimens are adorned with injuries such as infections and fractures. A pathological study on Gorgosaurus specimen TMP94.12.602 reveals a fracture in the right fibula's shaft, as well as rib fractures and bite lesions on the skull. All the wounds were shown to be healing.

Image credit: Natural History Museum of London

It's been long debated whether or not Gorgosaurus can be considered the same genus as Albertosaurus. Before, it was commonly accepted to lump the two into the same genus, though more recent studies show otherwise. Skull anatomy of Albertosaurus is more similar to that of Daspletosaurus, another contemporary tyrannosaurid, and Tyrannosaurus than it is to Gorgosaurus. Albertosaurus also has proportionately smaller fore limbs. To quote Dr. Currie, "[Albertosaurus and Gorgosaurus] were no more similar than Daspletosaurus and Tyrannosaurus [were]." For now, unless new research pops up, Albertosaurus and Gorgosaurus can be regarded as different genera.

The tropical ecosystem of Cretaceous Alberta was teeming with life. Albertosaurus and Gorgosaurus not only lived alongside each other, but as well as a another tyrannosaurid, Daspletosaurus. The more slender build of Albertosaurus and Gorgosaurus suggests that they were better suited to hunting hadrosaurids, while Daspletosaurus tackled armored prey. Hadrosaurids such as Parasaurolophus, Lambeosaurus, and Corythosaurus were most certainly abundant during the time. With the disappearance of most sauropods, the "duck-billed" dinosaurs had relatively low competition for food. Ceratopsians, the horned dinosaurs, were another relatively common dinosaur at the time. Pachyrhinosaurus, Chasmosaurus, Spinops, and Styracosaurus were some, but not all, of the ceratopsians to have lived with the tyrannosaurs. Among them were ankylosaurs such as Euoplocephalus, filling in an ecological niche the stegosaurs of the Jurassic Period left behind. Smaller predators like the ornithomimosaur Struthiomimus and the dromaeosaur Dromaeosaurus hunted smaller prey. Champsosaurus, a relative of the modern-day gharial, populated lakes and rivers. Overall, a lush and tropical climate allowed for an extremely diverse ecosystem of many different organisms.

Gorgosaurus libratus -  Called the 'opisthotonic' pose, caused by contraction of neck muscles during/after death
Photo by the author

References/Further Reading

"Royal Tyrrell Museum." Royal Tyrrell Museum. N.p., n.d. Web. 18 Aug. 2015.

Mccord, Robert. "Arizona Museum of Natural History." Arizona Museum of Natural History. N.p., n.d. Web. 18 Aug. 2015.

Switek, Brian, and Julius Csotonyi. Prehistoric Predators. N.p.: n.p., n.d. Print.

Palmer, Douglas, Simon Lamb, Angeles Gavira Guerrero, and Peter Frances. Prehistoric Life:. New York, NY: DK Pub., 2009. Print.

Benton, M. J. Walking with Dinosaurs: Fascinating Facts. New York: Dorling Kindersley Pub., 2000. Print.

Pim, Keiron. Dinosaurs the Grand Tour: Everything worth Knowing about Dinosaurs from Aardonyx to Zuniceratops. N.p.: n.p., n.d. Print.

Paul, Gregory S. Predatory Dinosaurs of the World: A Complete Illustrated Guide. New York: Simon and Schuster, 1988. Print.

Monday, August 17, 2015

Museum Visits: Royal Tyrrell Museum Part 3

For a dinosaur enthusiast, there's little that can make one geek out as much as the Royal Tyrrell Museum's Dinosaur Hall can. Filled to the brim with replica casts and real fossil specimens, its enough to make the most hardcore dino fan look around with sheer awe.

The Late Jurassic Camarasaurus, from the Morrison Formation, is the first attraction in the Dinosaur Hall. 

Head over to the right of the Camarasaurus and visitors can find an Allosaurus with its latest meal, an unfortunate Camptosaurus. A Stegosaurus (albeit in an outdated "retro" pose) watches the vicious attack.

Not surprisingly, the bulk of the dinosaur that make up the exhibit hail from the Cretaceous era, such as this Gorgosaurus (right) and Euoplocephalus (left). As an avid ankylosaur lover, the Euoplocephalus mount looks absolutely gorgeous. It's a bit of a shame most ankyosaur remains are, for the most part, incomplete.

Gorgosaurus makes another appearance, this time scavenging the carcass of a Centrosaurus. The diorama represents the famous bone bed discovered in Alberta containing at least 200 Centrosaurus remains. Whether or not it was a flash flood that killed the ceratopsians, it's certain that theropods and other carnivores would have scavenged the bodies.

Remarkably well-preserved fossils of Pachyrhinosaurus.

Psittacosaurus lived in Mongolia and is considered one of the earliest known ceratopsians. Lack of facial horns and a bipedal stance certainly don't make it look like Triceratops, but it matches other primitive ceratopsians like Aquillops.

Chasmosaurus, like Pachyrhinosaurus and Centrosaurus,lived in Alberta and were most likely a substantial prey item for tyrannosaurs like Gorgosaurus and Albertosaurus.

Hadrosaurs were abundant during the Cretaceous, Canada especially. Pictured are Lambeosaurus (above) and Gryposaurus (below).

A collection of hadrosaur skulls.

Ornithomimus attempts to make off with Maiasaura eggs.

Back near the Gorgosaurus mount you can find several Dromaeosaurus.

The museum even has a marine exhibit! Mosasaurs, plesiosaurs, pliosaurus, the exhibit showcases what life would been like in the Western Interior Seaway.

The Maastrichtian Cretaceous is our final stop in the Mesozoic era, and the familiar three-horned face finally appears! Triceratops was, you guessed it, one of the very last dinosaurs to live during the Cretaceous.

Hypacrosaurus, the near the highest lizard (that's what its name means! It was almost as tall as Tyrannosaurus).

Tyrannosaurus claims its position as king in the hall, looming gleefully over every other dinosaur. This specific mount is pretty notable for appearing in that old IMAX film T. rex: Back to the Cretaceous

A close-up of the tyrant king's skull.

There's only one more exhibit after the dinosaur hall, and its the Age of Mammals. Next time, we'll visit our modern ancestors in the Tertiary era!