Tuesday, November 13, 2018

Microraptor: Beast of the Week

This week we shall check out a tiny dinosaur that has taught us more than we ever could imagine we'd learn about any fossil animal.  Enter Microraptor gui!

Microraptor was a small, feathered, meat-eating dinosaur that lived in what is now China, during the early Cretaceous, 120 million years ago.  Adults ranged in size between 2.5 and 3 feet long from snout to tail.  The genus name, Microraptor, translates to "Small Hunter/Thief".

Microraptor was a tiny member of the dromaeosaurid family of dinosaurs, and therefore was related to creatures like Deinonychus, Dakotaraptor, and the extremely popular Velociraptor.  Like it's larger cousins, Microraptor had and long thin tail for balance, three long claws on each hand and of course, the signature retractable "killer claw" on the second toe of each foot.  Microraptor had large eye sockets, indicating it had good vision, and a mouth armed with pointed teeth, some of which were serrated.

Watercolor life reconstruction of Microraptor gui  hunting a scorpionfly by Christopher DiPiazza.

Microraptor's real claim to fame is the fact that in preserved its feathers during the fossilization process, giving us a much clearer vision of what it looked like when alive.  Microraptor would have been as covered in feathers as most modern birds, and even had proportionally very long, primary feathers growing out of its arms and hands, forming wings.  More amazing, Microraptor also had long wing feathers on its legs and feet!  There were actually other kinds of dinosaurs that evolved to have primary feathers on their lower limbs we now know of, like Anchiornis or Changyuraptor, but Microraptor was the first of these to be discovered and described back in 2003. 

So why the extra set of wings?  At first it was proposed that Microraptor would have lived in trees and glided from branch to branch with its legs outstretched behind it, like a modern flying squirrel, using the leg wings to form a kite-like shape as it did so.  It was later determined that despite the fact that the fossilized skeleton had the legs in this position, that it was crushed flat in a position not true life during the decomposition and fossilization process.  Other known dromaeosaurs, and living birds can't position their legs that way without breaking them, and Microraptor likely was the same.  Instead, it is possible Microraptor's leg feathers could have provided extra lift when jumping or taking off.  Many paleontologists now think that Microraptor may have been capable of actual powered flight, and not just gliding.  It had a fused sternum, like most modern flying birds have, and its wing feathers were extremely long to the point where they, combined with its leg wings, almost certainly could have provided Microraptor the ability to get and stay off the ground if it needed to.  It's arm sockets, however, prevented Microraptor from lifting its arms above its shoulders, like modern flying birds can to perform a strong upstroke when flapping.  This doesn't mean that Microraptor still couldn't fly, it just means it wasn't as adept a flier as a lot of modern flying birds.  It would have been common to see Microraptor flying short distances, possibly from tree to tree, or from the ground to a tree to roost, but probably not soaring up in the sky. 

There are many specimens of Microraptor on the fossil record and several of them actually preserved food that had been ingested shortly before the Microraptor died.  Because of this wealth of fossil information, we know that Microraptor was a meat-eater, but wasn't picky or specialized in going after one kind of prey.  Among the known last meals include lizards, mammals, birds (yes, there were more modern-style birds back then, too) and even fish.

Cast of the skeleton and feathers of Microraptor gui on display at the American Museum of Natural History for their Dinosaurs Among Us seasonal exhibit.

For a long time, we always assumed that no matter how many fossils we found, we'd never know what colors prehistoric animals were.  Not the case with MicroraptorMicroraptor's feathers preserved so well, that when viewed under a microscope, organelles called melanosomes were found to still be present.  Melanosomes are responsible for determining what color waves reflect back when light hits the feather.  Whichever waves are reflected is the color we see.  Even though the color, itself, was not visible anymore, by comparing the shape of the fossilized Microraptor melanosomes to melanosomes of modern bird feathers, paleontologists were able to deduct what colors Microraptor would have had when it was alive.  As it turns out, Microraptor feathers were iridescent blackish bluish, like those of modern crows, grackles, and starlings!  Since the iridescence of feathers like these can only be noticed in the sunlight, this also supports the idea that Microraptor would have been active during the day and not at night, otherwise there wouldn't have been a reason for it to have evolved such reflective colors.  This being said, keep in mind these melanosomes were only observed in one specimen of Microraptor.  This doesn't mean that all Microraptors were this color throughout their whole lives.  It is entirely possible that only adults, or one sex was this color.  Or maybe Microraptor molted feathers, becoming a different colors depending on the season.  There is still room for imagination!

Modern Boat-Tailed Grackles have feathers that may have been similar to those of Microraptor.  Notice the shiny blue-black coloration.
That is all for this week!  As always feel free to comment below!

References

Chatterjee, S.; Templin, R.J. (2007). "Biplane wing planform and flight performance of the feathered dinosaur Microraptor gui"(PDF)Proceedings of the National Academy of Sciences104 (5): 1576–1580.

Jingmai O'Connor; Zhonghe Zhou & Xing Xu (2011). "Additional specimen of Microraptor provides unique evidence of dinosaurs preying on birds"Proceedings of the National Academy of Sciences of the United States of America108 (49): 19662–19665. 

Li, Q.; Gao, K.-Q.; Meng, Q.; Clarke, J.A.; Shawkey, M.D.; D'Alba, L.; Pei, R.; Ellision, M.; Norell, M.A.; Vinther, J. (2012). "Reconstruction of Microraptor and the Evolution of Iridescent Plumage"Science335 (6073): 
1215–1219. 

 Lida Xing; et al. (2013). "Piscivory in the feathered dinosaur Microraptor". Evolution67: 2441–2445.

Senter, P (2006). "Scapular orientation in theropods and basal birds, and the origin of flapping flight". Acta Palaeontol. Pol51: 305–313.

Xu, X., Zhou, Z., Wang, X., Kuang, X., Zhang, F. and Du, X. (2003). "Four-winged dinosaurs from China." Nature421(6921): 335-340, 23 Jan 2003.

Sunday, November 4, 2018

Harpymimus: Beast of the Week

This week we will be checking out a bird-like dinosaur that was named after a fearsome mythical creature.  Let's check out Harpymimus okladnikovi!

Harpymimus was a theropod dinosaur that lived in what is now Mongolia, during the early Cretaceous period, between 107 and 100 million years ago.  It measured a little over six feet long from snout to tail and would have almost certainly been covered in feathers when alive.  The genus name, Harpymimus, translates to "harpy mimic" in reference to the harpy, a monster from Greek mythology with the head of a human and body of a bird.  I'm not sure why this dinosaur, in particular was named after a harpy other than the fact that it was bird-like, which isn't really a unique feature among dinosaurs.

Harpymimus life reconstruction in watercolors by Christopher DiPiazza.

Harpymimus was a very early member of the group of theropod dinosaurs, called the ornithomimosaurs.  These dinosaurs are known for having had long legs, long, slender necks, and relatively small heads with beaks.  The late Cretaceous-living Gallimimus and Struthiomimus are more famous members of this group, and Deinocheirus was a very large member.  Since Harpymimus lived so much earlier than most of the other known ornithomimosaurs, it also showcases a number of features in its anatomy that would change as its descendants became more specialized.  This is a great example about how studying fossils allows you to see how the evolution of many kinds of organisms changed over millions of years, which also tells us a lot about organisms that are still alive with us today!

Harpymimus skeleton on display at the Mongolian Academy of Sciences)

Harpymimus had relatively large eye sockets, suggesting it could see well, and had a long, slightly down-turned snout.  It had teeth on the very tip of its lower jaw.  Teeth in general are considered an ancestral trait for this kind of dinosaur, since all the late Cretaceous ornithomimosaurs were completely toothless.  Harpymimus teeth were tiny and cylinder-shaped.  They would have been hardly noticeable unless you were to look directly into Harpymimus' mouth up close.  What these teeth were exactly for is a mystery.  Many hypothesize that Harpymimus could have been an omnivore, eating plant material as well as hunting for small prey, like invertebrates or other kinds of small animals it could snap up.

Harpyimimus had long arms tipped with three fingers on each hand, but the first digit was significantly shorter than the other two.  This is typical for most kinds of three-fingered theropods, but would eventually change in later-living ornithomimosaurs, which had three fingers of equal lengths on each hand.

Harpymimus had long, powerful legs, which would have enabled it to have run quickly.  While later ornihomimosaurs only had three toes on each foot, Harpymimus possessed a fourth (but digit 1) tiny toe, called a hallux, which was on the inside of each foot.  This is also a trait common to most theropods, but evolved out as ornithomimids became more specialized later in the Cretaceous.

That is all for this week!  As always please comment below or on our facebook page!

References

Barsbold, R. and Perle, A. (1984). [On first new find of a primitive orithomimosaur from the Cretaceous of the MPR]. Paleontologicheskii zhurnal2: 121-123

Kobayashi, Y. and Barsbold, R. (2005). "Anatomy of Harpymimus okladnikovi Barsbold and Perle 1984 (Dinosauria; Theropoda) of Mongolia." In Carpenter, K. (ed.) The Carnivorous Dinosaurs. Indiana University Press: 97-126

Thursday, October 25, 2018

Caelestiventus: Beast of the Week

This week we will be checking out a newly discovered creature that is one of the oldest known pterosaurs to date.  Let's check out Caelestiventus hanseni!

Caelestiventus lived in what is now Utah, USA, during the late Triassic period, about 208 million years ago.  It was a meat-eater, and based on the bones that have been found, would have had a wingspan of almost five feet.  The genus name, Caelestiventus, translates to "heavenly wind" and the species name, hanseni, is in honor of geologist, Robin Hansen.

Life reconstruction of Caelestiventus in watercolors by me.

Caelestiventus is particularly amazing because it is the oldest known pterosaur from North America.  On top of this, it lived in an arid, desert-like environment, which is not common in currently-known pterosaurs.  Even more amazing is that the bones from Caelestiventus are beautifully preserved in three dimensions.  Most pterosaur bones tend to become flattened during the fossilization process because they are so delicate.  The fact that Caelestiventus preserved as well as it did allowed paleontologists to get a better idea of the shape of he skull.  According to what was found, Caelestiventus would have had powerful jaws, due to ridge-like structures on the top of its skull where muscles would have attached in life.  Since paleontologists were able to scan the inside of the skull, including the space its brain occupied, they found that its eyesight would have been powerful, but the senses of smell and taste less so.

3D printed cast of Caelestiventus' skull.  This pterosaur is known from an almost complete skull and a piece of the wing.

Caelestiventus was a very close relative of the more famous, and slightly later-living pterosaur, Dimorphodon.  Both of these pterosaurs had proportionally gigantic skulls that were tall and armed with differentiating kinds of teeth, which is also unusual among known pterosaurs, let alone reptiles in general.  Caelestiventus, specifically had long, pointed teeth in the front of its jaws, which would have been ideal for capturing prey, and smaller, more blade-like teeth in the back of its jaws, which appear to have been more for processing food once in the mouth.

Exactly what Caelestiventus was eating is still mostly a mystery, but we do know there were a number of small reptiles, like sphenodonts (relaitves of modern tuataras),  pseudosuchians (relatives of modern crocodilians), and even some dinosaurs, that at least as babies, could have been food items for this pterosaur.   There were almost certainly a variety of insects alive back then, as well, that could have been a staple food source for Caelestiventus.

References

Britt, B. B.; Dalla Vecchia, F. M.; Chure, D. J.; Engelmann, G. F.; Whiting, M. F.; Scheetz, R. D. (2018). "Caelestiventus hanseni gen. et sp. nov. extends the desert-dwelling pterosaur record back 65 million years"Nature Ecology & Evolution.

Britt, B. B.; Chure, D. J.; Engelmann, G. F.; Shumway, J. D. (2016). "Rise of the erg—Paleontology and paleoenvironments of the Triassic-Jurassic transition in Northeastern Utah"Geology of the Intermountain West3: 1–32.

Tuesday, August 21, 2018

Prehistoric Beast Visits The Last American Dinosaurs at the National Museum

The school I teach for took a field trip to the National Museum of National History in Washington D.C. in the beginning of June.  Little did they suspect (actually they totally knew) I was going to have as much fun, if not more fun, than my students.  Frustratingly, the museums normal fossil hall, the David H. Koch Hall of Fossils, was under construction and will be open in June of 2019.  However, the museum knew that if they had no dinosaurs at all to show visitors there would be violent riots so they set up a great temporary exhibit, The Last American Dinosaurs.  Let's check it out!

As the title suggests, The Last American Dinosaurs showcases the creatures that lived at the very end of the Cretaceous period, called the Maastrichtian era, between 68 and 66 million years ago, from what is now Western North America.  This area is referred to as the Hell Creek formation.  These were the dinosaurs that suffered as a result of the famous meteorite hitting the earth, causing the extinction of the dinosaurs...but not really because birds are still alive.  A lot of the most famous dinosaurs lived in the United States during this time, so it was a good opportunity to show some fossils of them, alongside some not-so-well-recognized fossils from plants and other animals that also lived there.

The first thing you see when you walk in is a cast skeleton of my favorite dinosaur, Triceratops horridus!  I recognized this individual from this museum's original fossil hall, which I visited several years prior.  Casts are great to use as displays since they are lighter and therefore can be more easily mounted, less fragile and therefore are less stressful to worry about being mounted, and less valuable than the actual fossil and are therefore less of a tragedy if broken.  Finally, this lets paleontologists study the real bones in the lab behind the scenes, while the public can still enjoy what those fossils look like when they visit the museum.  Everybody wins.

The Triceratops mount is the first thing you see when you walk in this exhibit.

Next to the full Triceratops mount was a glass case that showed the inside of this magnificent dinosaur's skull.  This allowed visitors to see the size and shape of what the brain would have been relative to the rest of the skull.  It also showcased the ball-shaped section of bone on the back of the skull, that fit into a socket in the first neck vertebrae.  This ball and socket mechanism gave Triceratops and other ceratopsids a wide range of flexibility with their huge skulls.

Inside of a Triceratops' skull.

On the other side of the skeleton was another glass case showcasing casts of juvenile Triceratops and what would be considered a baby TriceratopsTriceratops is known from a wealth of specimens of varying ages.  We now know that as a youngster, this dinosaur's horns started small, and curved upwards.  As the dinosaur continued to grow and mature, the horns began to grow forwards.  This may have been to help signal to members of its own species whether or not the animal was mature, and therefore ready to mate or engage in intraspecies combat, in which case, more forward-facing horns would be more useful.

Few creatures cuter than a baby Triceratops.  Something about those little nub horns.

You can't have an exhibit on the latest Cretaceous without a Tyrannosaurus!  This exhibit showcases a cast of "Stan", a Tyrannosaurus who's original skeleton is at the Black Hills Institute in South Dakota.  This Tyrannosaurus is famous for the teeth being exceptionally long, although this may be due to them partially falling out of their sockets after the dinosaur died.

A replica of "Stan" is the center of the exhibit.

Edmontosaurus annectens (formally known as Anatosaurus and Anatotitan) is represented by a skull.  This giant plant eater is known from some beautifully preserved specimens, that even include skin impressions.  The display here focuses on their eating habits, and the fact that they had hundreds of small teeth which were adept at pulverizing tough plant material.

Can't do an exhibit about the Maastrichtian without Edmontosaurus annectens.

This exhibit doesn't ignore the smaller, less recognized creatures of the latest Cretaceous, however.  They have a wall featuring some of the mammals, a salamander, and even plant fossils, alongside the dromaeosaurid dinosaur, Acheroraptor, on display.  Despite the fact that large dinosaurs are the most exciting to most people, it is also exciting to learn about other aspects of the environment they lived in.  Mammals, although restricted to below a certain size range during the Mesozoic, were still extremely successful, widespread and in their own right, diverse.  Plants are fascinating to think about during this time and certain species are still very mysterious as to how they would have looked and grown.  Amphibians have been around since before reptiles, let alone dinosaurs, and are still going strong in many environments today, which by itself is awe-inspiring.


Wall of unsung Maastrichtian heroes.

Lastly I'd like to show this little infograph they have hanging on the wall.  It features silhouettes of all the nonavian dinosaurs that coexisted in this environment that we know of which is pretty cool and informative considering lots of people falsely assume all dinosaurs coexisted with each other.  That being said, it appears they are still missing a few, like Dakotaraptor and Dracorex.  (before you try to tell me Dracorex wouldn't be on there because it is thought to be a juvenile stage of Pachycephalosaurus, note that Stygimoloch, also a perceived growth stage of this dinosaur, is featured.  So there.)  I also couldn't help but notice that the Tyrannosaurus and Triceratops horridus appear to be taken from the original Jurassic Park concept and promotional art by Crash McCreery.  Mark Klinger's image of the oviraptorosaur, Anzu is also there.   A number of the other images look like they were taken from other artworks I've seen before and various stock images from the internet.  To the folks at the National Museum...all you needed to do was email me and I would have gladly taken the job as illustrator for you!

This was the one disappointment in an otherwise great exhibit for me.

Overall, I think this was a cool exhibit that does a great job temporarily satisfying anyone's appetite for paleontology when they visit the National Museum.  It does a good job educating the public on their old favorite dinosaurs, as well as introducing some lesser known creatures that deserve more attention.  That being said, I am still really looking forward to seeing what is in store when their permanent fossil hall is completed!

Sunday, August 5, 2018

Ingentia: Prehistoric Beast of the Week

This week we'll be checking out a newly discovered dinosaur that was a giant long before we thought giants existed.  Make way for Ingentia prima!

Ingentia was a plant-eating dinosaur that lived in what is now Argentina during the Late Triassic Period, between 210 and 205 million years ago.  Sadly, only a partial skeleton is known so far from two individuals, including vertebrae, shoulder blades, and arm and hand bones.  However, this material is enough, with the help of referencing other kinds of dinosaurs that are similar and closely related, to estimate Ingentia was between twenty five and thirty three feet long from snout to tail.  This makes Ingentia the largest known animal in its environment.  The genus and species of this dinosaur translate to "First Huge One".

Ingentia prima knocking over a tree fern (and scaring the daylights out of a sphenodontid)  in watercolors by Christopher DiPiazza.

Ingentia belonged to a group of dinosaurs called the sauropodomorphs, which which are famous for having long necks and eating plants.  Brontosaurus, Apatosaurus, Diplodocus, and Brachiosaurus are probably the most recognizable members of this group.  These famous dinosaurs are from the later major branch of the sauropodomorph tree, which flourished in the late Jurassic Period, growing to gigantic proportions and sporting column-like legs and feet.  Ingentia, however, appears to have been from the earlier branch of this major group of dinosaurs that flourished in the late Triassic and early Jurassic periods which were overall smaller in size.  They are sometimes referred to as the basal sauropodomorphs, or prosauropods.  The most famous member of this group of dinosaurs would be Plateosaurus. (Which is sadly still not nearly as famous as the late Jurassic giants mentioned earlier.)  Prosauropods had five fingers and three claws on each hand, and many species walked on their hind legs.

Since Ingentia appears to be from the basal sauropodomorph group, it supports the notion that extremely large body size in dinosaurs not only started much earlier than we thought, but it also occurred twice in the sauropodomorph family tree.  Looking at cross sections of Ingentia's bones, paleontologists could tell that it was growing in spurts throughout the year, probably based on the seasons.  During the times when food was more abundant, Ingentia grew rapidly.  It's growth slowed down when resources were less available.  This is in contrast to the growth patterns we see in the later kinds of sauropodomorphs which grew constantly, but at a more steady pace.

Figure from Apaldetti's paper describing Ingentia showing the known bones.

Ingentia's vertebrae show that they would have had air sacs in them in life, like modern birds have.  Ingentia wasn't using air sacs to fly, obviously.  They would, however, be great adaptations for staying relatively light for the animal's size, which allowed it to grow much larger than a creature that had solid bones.  This is why the largest dinosaurs exceed the largest land mammals, which have solid bones, by so much.  A mammal beyond a certain size would collapse under its own density, while a dinosaur, which is much lighter for its volume, could grow much more before hitting its threshold.  Air sacs also help keep the inside of the body from overheating, and help keep a more constant supply of fresh oxygen circulating throughout the body.

Ingentia has been depicted walking on all fours in life a lot so far, but since most of its hind limbs have yet to be uncovered, we still don't know for sure if it could also walk on just two legs, as well.  There is even a chance it was an obligatory biped, only walking on its hind legs, like its later relative, Plateosaurus.
 
That is all for this time!  As always feel free to comment below!

References

Apaldetti, Cecilia; Martínez, Ricardo N.; Cerda, Ignatio A.; Pol, Diego; Alcober, Oscar (2018). "An early trend towards gigantism in Triassic sauropodomorph dinosaurs". Nature Ecology & Evolution.

Monday, July 16, 2018

Helveticosaurus: Beast of the Week

This week we will be checking out an unusual reptile with anatomy that continues to stump paleontologists.  Let's check out Helveticosaurus zollingeri!

Helveticosaurus was a marine reptile that lived during the Triassic period, about 242 million years ago, in what is now Switzerland.  From snout to tail it measured a little over six feet long.  The genus name translates to “Swiss Reptile” in reference to where this creature used to live.

Life reconstruction of Helveticosaurus in watercolors by Christopher DiPiazza.

Helveticosaurus is known from an almost complete articulated skeleton.   Because of this we have know a lot about its anatomy.  However, its combination of features is so unusual that scientists are still unsure as to what Helveticosaurus was, beyond a kind of diapsid reptile.  Diapsids have two openings in their skulls beyond their nostrils and eye sockets.  It's a vast grouping of animals, so it doesn't really narrow down what Helveticosaurus was closest related to.

Helveticosaurus skeleton on display in the Paleontology Museum of Zurich, in Switzerland.

Helveticosaurus had a long tail that was flattened laterally.  This would have been ideal for swimming.   It probably used its tail, powered by large muscles at its base, as its main mode of propulsion in the water.  However, unlike a lot of other marine reptiles, Helveticosaurus also had proportionally long, and very powerful arms.  It may have used these arms, tipped with long fingers which may have been webbed in life, to help steer while swimming.  It has also been suggested that these arms could have been another source of propulsion.

Close up of Helveticosaurus' skull.  It was broken and crushed sometime in the 242 million years since the animal died, but you can clearly make out the extremely long teeth.

The skull of Helveticosaurus is also uniquely short, almost box-shaped and its teeth were long, curved, and pointed.  The longest teeth growing from the front of the snout.  This is an especially odd combination of adaptations since most marine animals with teeth like that possess long snouts to better capture swimming prey.  Most marine animals with short snouts, like Marine Iguanas, have small teeth, that when paired with the blunt snout, are ideal for clipping underwater plants and algae.  It has also been suggested that the short snout, which allows for more concentrated power when biting down, was an adaptation for eating shelled mollusks and crustaceans, like modern walruses do.  However, animals that eat that kind of prey have blunt, wide teeth, for crushing.  Helveticosaurus' long, narrow teeth look like they'd break if they were trying to crush hard shells.  Does this mean Helveticosaurus was an evolutionary failure?  Absolutely not.  It simply means we haven't figured out how it was feeding yet.  Hopefully a new discovery or idea will help us find out in the future!  As of now, most scientists agree that Helveticosaurus was eating meat in some form, based on its teeth.  Exactly which kind and how is still a mystery.

That is all for this week!  What do you think Helveticosaurus was using its odd combination of traits for?  Leave your ideas in the comments below!

Refereces

Bernhard Peyer (1955). "Die Triasfauna der Tessiner Kalkalpen. XVIII. Helveticosaurus zollingeri, n.g. n.sp.". Schweizerische Pal√§ontologische Abhandlungen72: 3–50.

Naish, D. (2008). "One of so many bizarre Triassic marine reptiles." Weblog entry. Tetrapod Zoology. 13 September 2008. Accessed 24 July 2009.

Neenan, J. M.; Klein, N.; Scheyer, T. M. (2013). "European origin of placodont marine reptiles and the evolution of crushing dentition in Placodontia". Nature Communications4: 1621

Friday, July 13, 2018

Dinosaurs at Nerd Nite Philadelphia

I had the privilege of being a speaker at Nerd Nite Philadelphia this week.  If you are not familiar, Nerd Nite is an organization that has people in a certain science, or other "nerdy" topic come into a bar and speak in front of an audience of other nerds about their field. 


I came in and talked about paleontology, different beasts that need more recognition, and particularly my experiences as a paleoartist and how depicting long extinct creatures certain ways can have positive, or sometimes detrimental, effects on how the public thinks about them. I also went into how it's a field that is always changing and that a hard-worked painting can become obsolete in a matter of seconds if a new, groundbreaking discovery is made.  (which is annoying, but ultimately still exciting.)


It was a lot of fun and I hope Nerd Nite decides to have me back soon.  Until then, here are a few snippets of video from the night.