Monday, September 28, 2015

Mad-packed with all nine essential nutrimites to fortify your X-Zone!

So extreme! X-treme! Even more extreme than Extreme Blu!

I might find the name a little 90s for my liking (although I guess that Clone High reference I just made is circa 2002), but this is a must-see exhibit that shows off a whole lot of cool animals you probably haven't heard of before. It's an awesome mix of fossils, casts, life restorations of extinct mammals, skeletons and taxidermy mounts of unusual modern mammals, nice graphics, and fun interactive stations. Here's a slice of highlights from the opening party I attended last Friday!

Giant rhino relative Indricotherium (Paraceratherium?) greets you as you enter the exhibit. Ancient rhino relatives are really cool and don't get enough love!

Uintatherium, a weirdly ornamented archaic Palaeocene mammal, and not one you see in too many museum exhibits.

And check out this sivathere skull - this is a giraffe relative!

The exhibit includes a nice diagram showing the changes that occurred between the earliest synapsids, like Dimetrodon, to modern mammals, and even talks about the concept of 'crown groups'.

This floofular Macrauchenia looks like something straight of Jim Henson's workshop. Macrauchenia is a South American hoofed mammal that's part of a larger group of hoofed mammals from that continent of confusing and uncertain ancestry - we'll see a few more later.

Lots of exhibits showcased particular features of mammal anatomy and showed convergences across clades. Here's Thylacoleo, the marsupial lion, with Thylacosmilus, the marsupial sabre-tooth in the background.

Speaking of teeth, this exhibit showcased extreme incisors - that's a narwhal skull in the back, and an extinct elephant called Platybelodon in the front.

And more weird teeth: the extinct giant marsupial Diprotodon.

Real mammoth hair!!!

Way back in the Eocene, things were a bit toastier than today, and Arctic Canada was a lush forest inhabited by Coryphodon. This guy is one of the earliest really big mammals that evolved after the K-Pg extinction, but doesn't have any close living relatives despite its hippo-like appearance.

One of the most spectacular specimens in the exhibit, this Scarrittia is a notoungulate, another of those weird South American hoofed mammals. It probably would have looked somewhat rhino-like when alive, but I'm always weirded out by the lack of a gap between the front teeth and the molars, like you see in things like cows and horses.

Bonus alive mammals! We got to meet several living animals during the opening festivities, including...

Jerry the binturong, from the Conservators Center.

Plus this shy armadillo...

...hungry sloth....

and curious bat-eared fox from the Flying Fox Conservation Fund!

Extreme Mammals is at the North Carolina Museum of Natural Sciences until March 27, 2016, and is well worth a couple of visits! Have you seen Extreme Mammals on its tour? Tell me about it in the comments!

Thursday, September 17, 2015

Burgers and Hot Dogs

Sydney Mohr is a friend and colleague of mine whose art you will have seen in the news lately, if you are inclined to read about ankylosaurs. She's done amazing reconstructions of two ankylosaurs for me in the last year - Ziapelta and Gobisaurus - and so I asked her to take a few minutes and tell us about her process for creating her palaeoart. Also this way I get to show off more of her drawings, so yay!

Sydney decided that this Gobisaurus was named Burger, and that seemed fine with me.

Once we got started on Gobisaurus, I sent Sydney a pile of photos of both Gobisaurus and its close relative Shamosaurus, and some of my own very rough sketches of what the osteoderms might have looked like. Gobisaurus isn't completely known, so we're guessing a bit on the osteoderm arrangement in the final version and using Shamosaurus for the cervical armour. Here are the earliest sketches Sydney sent me - so many great poses and personality. Also, here's a Sydney in her natural habitat (thanks John Acorn for the photo!).

One of the things I really like about your art is that it's obvious you are very familiar with animal anatomy and behaviour – your dinosaurs have real animal personalities. Can you tell us about some of your inspirations for your palaeoart? 

The best inspiration any artist can have when reconstructing extinct animals animals! In most cases that's the best if not the only source of reference we have, at least when it comes to external appearances. Depending on what type of fossil I'm drawing, I'll try to find an extant analogue/s that may share some characteristics, like habitat and environment, diet, colour scheme, etc. For colour in particular I often mix and modify schemes from two or more animals, all the while keeping the fossil's apparent paleobiology and habitat in mind. I'll peruse images of modern animals on the web to get an idea of the posture and stance I want the fossil animal to be in, as well as the lighting and angle. A lot of a creature's emotion comes from the face, so I really like to focus on eyes. Getting the shape, depth, colour, and light just so can make a huge difference in terms of giving a drawing personality. It also isn't a bad idea to look at other artist's work, obviously not to copy directly, but you might get ideas for new methods or techniques that you can adopt and fit into your own style. 

Mr Iridescent - a beautiful take on Microraptor. So shiny and chrome.

This reminds me, I think you said the Ziapelta reconstruction you did for our paper was inspired by a photo of a bird that you took! And that in turn reminds me that you are also a pretty great bird photographer - do you find that you get a better sense for conveying personality and movement in your dinosaurs by observing birds in the wild yourself?

So I did! The proudest grackle ever! 

I can see the family resemblence! Also, when I found out the Gobisaurus was named Burger, I asked if the Ziapelta had a name. Naturally, it was Hot Dog.

And definitely, seeing any animal in their habitat first hand can create a narrative in your mind that you can translate to paper. Birds are great to watch because a lot of the time they're always on the move and engaging in a variety of behaviours that are both interesting and fun to watch, as well as perfect fodder for a dinosaur reconstruction.  

You are also working on a Masters with Phil Currie at the University of Alberta! Would you like to tell us about what you're working on?

The thought of Mesozoic birds with bonafide teeth has really interested me for a while, so the plan is to explore the evolution of tooth loss in birds by comparing the implantation and replacement rates of small theropod (like dromaeosaurids and troodontids) and bird teeth. Looking into the anatomy of the jaw and the inner structures of the teeth of these closely related groups will hopefully yield some informative results. It's not easy because the stuff I need is comparatively rare and pretty darn tiny! I'm working entirely with Alberta material at the moment, and doing so has led me in other directions in terms of understanding the province's Cretaceous avian fauna, which is most represented in terms of numbers by, you guessed it, teeth!

Pygostylia Panoply: at the bottom, the toothy Early Cretaceous enantiornthine Rapaxavis, and up top, the duck-like (and toothless) Presbyornis.

Do you have a favourite taxon to illustrate?

Birds and feathered theropods are definitely up there.The more I do ankylosaurs though the more I enjoy drawing them. [YES FOLKS, YOU HEARD IT HERE: ANKYLOSAURS > THEROPODS.] They're so unique compared to anything else around today! I also enjoy doing mammals as well, like ungulates and carnivores (fossil or modern) and primitive examples from the Mesozoic. 
I am but a young'un: a perfectly floofular dromaeosaur chick. 

What medium/media do you like to work in?

I stick almost exclusively to traditional media; mainly pencil work, both black and white and colour, although I occasionally work in acrylic or watercolour. I prefer to work with fine tooth paper so I can vary my pencil strokes, blend more easily, and just have an overall smoother surface to work on. Coloured paper is also really fun to work with, like blue or black, because it makes drawing ocean scenes with pencil pretty simple. I've also dabbled in digital art via photoshop, but most of the time I only use it to fix mistakes and touch up scanned pencil drawings. In my case I find I have much more control with pencil and paper, and the results seem to be a bit more realistic, at least to my eyes. 

Ichthyornis dispar: a classic fossil bird, brought to life!

Do you have any advice for other people who are interested in creating their own palaeoart? Any common pitfalls to avoid, or things to think about when they are recreating an extinct animal?

I think one of the most important aspects of reconstruction is attention to detail, such as the dot of light and reflections in an eye, or the wind disturbing and ruffling fur or feathers, or the bulge of a muscle as a limb is flexed, or the crumpling of skin as it moves in a certain direction or shifts under the weight of the animal. Light, movement, and substance. Those kinds of little and almost unnoticeable features can take a simple reconstruction of a fossil to something that feels tangible and alive. In terms of pitfalls to avoid, I would say there isn't too much to worry about if you're just playing around and having fun, because hey, it's just art! That being said, if you're going for a publishable, as-accurate-as-possible, realistic style of depiction, then it's a good idea to become familiar with your subject, especially anatomy. If you can read up and get as close as possible to the original source material, like scientific papers, then you're that much closer to getting your skeletal anatomy down pat. Knowing some anatomy of modern animals is extremely helpful as well, as it informs how muscle and skin attaches to the bone and changes the outline of the body.

Thanks Sydney! You can check out more of Sydney's amazing art and photography at her website, DeviantArt gallery, and Flickr gallery.

Tuesday, September 15, 2015

Evolving Planet

Today we embark on an adventure, an adventure through time and space (but not outer space or inner space, just regular space). Welcome, to the Evolving Planet.

This is the Field Museum's fossil hall, and it's a great exhibit with tons of interesting fossils presented in a really accessible and immersive way.

We travel through the Big 5 mass extinctions, with each clearly marked with a discussion about how life on earth changed at each event. I'm skipping through the first couple of eras here because I'm a stinkin' amniote worker and also I wasn't very good at photographing some of the stuff in low-light settings, but rest assured there was an awesome shark fossil and many cool things in the Palaeozoic.

I have a secret love for the Permian, so imagine my delight when I stumbled upon a room full of pareiasaur skeletons (like this Bradysaurus) and Eryops and captorhinids. A bounty!

Also, hooray for non-Dimetrodon sphenacodontids! We got Dimetrodon AND Ophiacodon AND Sphenacodon! Whoa!

On to the dinosaur hall, there are some cool dinosaurs that you won't see in every museum. Here's Parasaurolophus cyrtocristatus, a species of Parasaurolophus with a shorter and more rounded crest compared to the species more often illustrated in books, P. walkeri.

And dwarfed by the giant Apatosaurus (?) is this comparatively little Rapetosaurus, a titanosaur from Madagascar.

Hey look, it's a vintage-y Archaeopteryx reconstruction! Love the Victorian fancy pigeon look that's happening here.

PALAEOSCINCUS SPOTTED. One thing that I really love is that a bunch of old Charles Knight paintings are still displayed with pride throughout the exhibit, with interpretive signage putting them into context for what we've learned since they were painted. Here we can see a classic 'Palaeoscincus', an old interpretation of what Late Cretaceous ankylosaurs looked like back when we didn't have as much information about nodosaurids vs. ankylosaurids. This fellow has the long, relatively unornamented snout and large shoulder spines of Edmontonia (a nodosaurid), and the tail club of Ankylosaurus (an ankylosaurid).

Let's finish off with a quick peek into the Palaeocene! And what's this, not one but TWO pantodonts? (Also, whoa, Coryphodon is really big.)

Bonus photo! In the fishbowl prep lab, they are working on Cryolophosaurus bones collected during the last expedition in 2011!

Saturday, September 12, 2015

Snapshots from the Field Museum

Last week I got a chance to visit the Field Museum in Chicago for the first time! It's a great big museum with lots of cool stuff, so I figured I'd share a few impressions from my lunchtime jaunts through the exhibits. Let's get started with all the fossil exhibits outside of the main fossil hall (there are several, but some of them are kind of hidden away!).


Sue the Tyrannosaurus is most definitely not hidden away, and occupies a place of pride in the museum's main entrance hall. Sue is undeniably a great fossil, although I (and I suspect probably some other palaeontologists as well) have mixed feelings about this fossil: it's incredibly well preserved, but the intense backstory to Sue's acquisition is filled with several unpleasant twists and turns. I'm glad Sue found a home in a museum, but I wish it hadn't been placed up for auction - Sue's auctioning may not have directly led to the trend of putting dinosaurs up for auction for millions of dollars, but I feel like it set a bad precedent all the same.

One thing that's particularly enjoyable about this specific Tyrannosaurus skeleton are the abundant pathologies to be found. Sue has a busted/infected shin, holes in its jaw, and rough bumpy spots on its vertebrae. These vertebrae near the end of the tail have a big mass of crinkly bone around them. It's obvious Sue got up to some trouble during its life, and it's interesting to speculate on the causes of the various oddities in the skeleton (and indeed, others have!).

 Extinct Madagascar

Sadly, this exhibit is tucked so far out of the way that basically nobody had wandered back there besides me (you need to go through the conservation gallery to reach it). It's also a little bit specimen-sparse, a trend I've noticed recently in many museums and which I find somewhat concerning. However, I feel like it makes up for the lack of 3D objects in its cool and unusual subject matter - the extinct fauna of Madagascar. The main point to the gallery was showcasing the social media response to new images of Madagascar's prehistory, and the scientific process that went into those images. It was an interesting way to approach the topic, but might have been more compelling with video, audio, or more fossils.

It was pretty cool to see an Aepyornis (elephant bird) egg and life-size silhouette. They really were terrifyingly large and strange birds.

A highlight for me was this Palaeopropithecus skeleton - a lemur that lived and looked like a sloth.

Tracking the Reptiles of Pangea

Tucked away in the African mammals area was a room devoted to palaeontological fieldwork in Tanzania, featuring the newly described silesaurid Asilisaurus! This isn't a skeleton you're going to see in most museums - I only wish more people had been stepping into this little exhibit room to check it out.

A nice touch was showing the original fossil material in its cabinet-ready storage foam. Those are some nice fossils.

And one last fossil....

Seriously, how were these machines not in constant use? They're in the hallway leading towards the bottom-floor cafeteria, and you can get yourself a freshly-made retro Triceratops, Brontosaurus, Tyrannosaurus, or Stegosaurus. I made a Brontosaurus and consider it $2 extremely well spent, especially since it meant I got rid of a bunch of dimes and nickels I didn't know what to do with:

Next time: Evolving Planet!

Monday, August 31, 2015

How the ankylosaur got its tail club

Ankylosaur tail clubs are odd structures, odder than they are usually given credit for. They represent substantial modifications to two different skeletal systems – the endoskeleton, in the form of the caudal vertebrae, and the dermal skeleton, in the form of the caudal osteoderms. The centra of the caudal vertebrae lengthen but stay robust, and the neural arches undergo huge changes, such that the prezygapophyses, postzygapophyses, and neural spine become a robust, V-shaped structure on the top of the centrum, and which creates a tightly interlocking vertebral series with almost no flexibility. We call this the handle of the tail club. The osteoderms at the tip of the tail smush together and two of them become huge: although the tail club knob is small in some species, there are colossal knobs exceeding 60 cm in width. The ankylosaur tail club represents one of the most extreme modifications to the tail in terrestrial tetrapods.

Look at that thing. That is a weird thing.
(This is UALVP 47273, a really nice club that I studied for my MSc work on tail club biomechanics.)

One of the questions I became interested in during my MSc research on ankylosaur tail club biomechanics was how the tail club evolved in the first place. Most ankylosaurs with tail clubs are known from a relatively narrow slice of time right at the end of the Cretaceous, but when and where did the tail club first evolve? Did the stiffening of the tail occur before the enlargement of the tail osteoderms, or vice versa? Or did both changes happen at about the same time? This was a fun question to address during my PhD research, once I had a fairly well resolved phylogeny of ankylosaurids, and once I had looked at tons of ankylosaurid fossils.

So, how did the ankylosaur get its tail club? Well, based on what we see in the fossil record, it looks like the changes to the vertebrae predate the changes to the osteoderms – in other words, the handle comes first and the knob comes later. There is at least one ankylosaur out there that seems to have a tail club handle but not a knob: Gobisaurus!

Hello Gobisaurus! Many many thanks to my friend and colleague Sydney Mohr for preparing this awesome illustration of Gobisaurus for me.

Gobisaurus, a shamosaurine ankylosaurid, has a really nice complete tail club handle that is indistinguishable from other ankylosaurid tail club handles, but does not have a knob. And it's not just because the knob is broken off – it seems as though the last vertebrae in the tail are preserved, because they look very similar to the terminal vertebrae in a CT scan of a tail club from the University of Alberta collections. It's likely that Gobisaurus had osteoderms along the sides of the tail like we see in most other ankylosaurs, but it doesn't appear that there were osteoderms tightly enveloping the tip of the tail.

An even earlier ankylosaur seems to show some changes towards acquiring a tail club handle, as well. Liaoningosaurus, a basal ankylosaurid known only from a very small juvenile, has distal caudal vertebrae where the prezyapophyses extend about 50% the length of the adjacent vertebra. This is what we see in ankylosaurid tail clubs, but not in more basal taxa like Mymoorapelta where the prezygapophyses are much shorter. Liaoningosaurus is missing the tip of the tail and also lacks osteoderms on most of its body because it's a juvenile, so it's harder to say whether or not it had a tail club knob based just on the fossil alone.

I also did a cool and relatively simple thing with my phylogenetic tree to see if I could better understand the likelihood that some ankylosaurs without preserved tail material had a tail club handle or full tail club with a knob. Unsurprisingly, all shamosaurine and ankylosaurine ankylosaurids probably had a tail club handle. Liaoningosaurus is part of a basal polytomy of ankylosaurids, and it was a bit more equivocal whether or not any of these taxa was likely to have a tail club handle or not, partly because another basal ankylosaurid in this region of the tree, Chuanqilong, does not have modified distal caudal vertebrae.

All ankylosaurine ankylosaurids more derived than Pinacosaurus (so including things like Tsagantegia, Saichania, Euoplocephalus, etc.) almost certainly had a tail club knob, and shamosaurine ankylosaurids probably did not. Crichtonpelta, the most basal ankylosaurine, may or may not have had a tail club – we'll need more data to know for sure. There is amounted skeleton of Crichtonpelta at the Sihetun visitor center in Liaoning, and it is shown with a tail club, but it isn't clear whether or not this is sculpted or original material belonging to this specimen, and a full description of this material is necessary.

Gobisaurus and Liaoningosaurus both lived much earlier than the more familiar tail-clubbed ankylosaurs: Gobisaurus is no younger than 92 million years old, and Liaoningosaurus is about 122 million years old. The earliest ankylosaurid with a tail club in the fossil record is Pinacosaurus (from the Campanian), although there is a caveat to this: Talarurus, which is a bit older than Pinacosaurus, should have a full tail club based on its position in the phylogenetic tree, and while a tail club handle is known for this taxon, we haven't found a tail club knob for Talarurus. Talarurus is in kind of a weird spot phylogenetically, since it's from Mongolia but comes out as closely related to North American ankylosaurines, so I think it's worth keeping an eye on this taxon in the future – perhaps Talarurus is another taxon with only a handle and not a knob, which would fit a bit better with its chronologic position if not its phylogenetic position.

Regardless, the changes to the vertebrae of ankylosaurs, starting with Liaoningosaurus at least 122 million years ago and continuing on towards Gobisaurus about 92 million years ago, seem to have occurred long before ankylosaurs evolved a huge osteodermal knob at the end of the tail. Was a stiff tail as good a weapon as a full tail club with a knob? What drove the evolution of the knob so long after the evolution of a stiff handle? And why did ankylosaurs even evolve a tail club at all? Now that I've had fun investigating how ankylosaurs might have used their tails, and how the tail club evolved, the next question feels like it should be 'why' stay tuned for more tail club fun over the next year or so as I make an attempt at that question!

Read it for yourself! Arbour VM, Currie PJ. In press. Ankylosaurid dinosaur tail clubs evolved through stepwise acquisition of key features. Journal of Anatomy.

Sunday, August 23, 2015

Know Your Ankylosaurs: Everybody's in this Together Edition

So with all of those posts about ankylosaur taxonomy over the last few weeks, what have we learned about the evolution of this group? Over the course of my PhD research, I was able to identify a bunch of new characters that seemed useful for understanding ankylosaur phylogenetic relationships, including characters related to the cranial ornamentation, pelvis, and osteoderms. Although ornamentation and osteoderms can be tricky, they can still yield useful information if you're careful about how you construct the characters.

Here's a sampling of some of the new characters from the supplementary file that goes along with the paper. Long live rainbow ankylosaur skulls.

With all the new information, here's what the results of the analyses gave us (click to embiggen):

From this, we can take away some interesting points:

1. Gondwanan ankylosaurs are probably not ankylosaurids, but they also don't form a single evolutionary group. Whatever "Minmi" is, it's a very basal kind of ankylosaur, possibly outside the split between Ankylosauridae and Nodosauridae. It's a little bit harder to say what's going on with "Antarctopelta" (previously considered an ankylosaurid), and the Argentinian ankylosaur: both came out as relatively derived nodosaurids, but my dataset isn't designed to test the interrelationships of nodosaurids. I wouldn't be surprised if future analyses incorporating more nodosaurids and more nodosaurid-based characters found that these two species were closely related. It would also be interesting to know which lineage of nodosaurids (probably a lineage from North America) dispersed into South America in the Late Cretaceous in order to give us these two ankylosaurs.

2. There are nodosaurids in the early-mid Cretaceous of Asia, but not necessarily the ones that have been proposed previously. Zhongyuansaurus, for example, was first described as a nodosaurid but is instead a junior synonym of the shamosaurine ankylosaurid Gobisaurus. However, a couple of taxa, like Taohelong, Sauroplites, and Dongyangopelta, are recovered as basal nodosaurids. At present, there doesn't seem to be much overlap between Asian nodosaurids and ankylosaurids, which is interesting! Why didn't nodosaurids hang on in Asia once ankylosaurids evolved, when the two groups seem to have coexisted pretty happily in North America later on?

3. The ankylosaurids from the Late Cretaceous of North America represent a dispersal of Asian ankylosaurines sometime during the early-mid Late Cretaceous. The earliest ankylosaurine is probably Crichtonpelta, from China, and North American ankylosaurines are a deeply nested clade within Ankylosaurinae. We propose the new name Ankylosaurini for the North American ankylosaurines (plus Talarurus, for now).

Here, have some frowny-faced rainbow ankylosaurs. Ankylosaurs are very serious dinosaurs.

4. Where do ankylosaurids first evolve? Unfortunately, that question isn't easy to answer right now: down at the base of Ankylosauridae, there's a mix of taxa from North America and Asia. The position of Gastonia as an ankylosaurid tips the scales slightly in favour of a North American origin for the clade, but some analyses recover this taxon as a nodosaurid, so I think we should be a little cautious about this result. One step up the tree, we've got a polytomy of Aletopelta and Cedarpelta (both from North America) and Liaoningosaurus and Chuanqilong (both from China). Does Ankylosauridae originate in North America with something like Cedarpelta, with a subsequent migration and diversification into Asia? Or does this group originate in Asia with something like Liaoningosaurus and Chuanqilong, and Cedarpelta represents an immigration into North America?

5. And finally, what's going on with ankylosaurids in the mid-Cretaceous of North America? Why don't we find any ankylosaurids between Cedarpelta and the later ankylosaurins? Did 'endemic' North American ankylosaurids go extinct during that time? And why does Aletopelta have such a weird basal phylogenetic position despite being from the Campanian? I don't really have answers for some of these questions, although if you come to the Society of Vertebrate Paleontology meeting in Dallas this October I'm going to try addressing some of them. For now, Aletopelta remains the biggest ankylosaurid enigma to me – it really shares very few things in common with the other Campanian ankylosaurids and I doubt it is an ankylosaurin from the Asian immigration into North America – could it represent a distinctive lineage of North American ankylosaurids stemming from things like Gastonia or Cedarpelta, for which we just don't have other representatives at the moment? Or, is it a nodosaurid masquerading as an ankylosaurid because I haven't sampled the right taxa or characters?

Darn you Aletopelta, why must you vex me so?

As usual, I wind up with more questions than answers every time I try to figure something out.

That wraps up the summaries for this paper, but stay tuned for some more cool research coming out in the next few weeks, and some summer fieldwork recaps!

Arbour VM, Currie PJ. In press. Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs. Journal of Systematic Palaeontology.