Friday, 27 February 2015

Fossil casts are not "fake"

After the news story a few weeks ago about the replacement Dippy the Diplodocus at the Natural History in London with a blue whale skeleton, there has been a lot of talk in the media and palaeontology community. I'm not going to go into why Dippy should or shouldn't be replaced, as it has been covered by numerous palaeontologists and news sites (for example, palaeontologist Steve Brusatte and HuffPost Technical Editor Michael Randle argue it's a good thing, while others like palaeontologist Mike Taylor disagree with the idea), but I will talk about another thing that has come up since then. One thing that a lot of non-palaeontologists have been saying is “oh well it was fake anyways” since it was made up of replica bones rather than real fossils. This is something that really bugs me.

I’m not sure why this has been picked up so much recently that casts and replicas are just “fake”. First of all, fake is something that is made with the intent to deceive. Fake money is meant to replace real money, or fake designer purses are meant to look like the real ones they imitate so people don’t know you have a fake. A replica or cast of a fossil is not meant to deceive. That is not the purpose. Any signs about the specimen will (or at least should) state whether the specimen is a skeleton, cast, or composite. No one is trying to trick you! You just have to read the signs!

The next important point is how these casts are made. Fossil casts are made from real fossils. There are many ways of making them, and I’m no expert so I won’t discuss that here. What I know is that people who make fossil casts, especially good ones, is that they put A LOT of effort into making them look as accurate and real as possible. They are most often made from some kind of mould that is made from the fossil using something like silicone or rubber. After that, plaster or something else hard is poured into the mould which allows for the exact structure of the original to be seen. Finally, the cast is painted and coloured in a way that matches the original specimen. When done properly and well, these casts look almost identical to the original fossil and only close examination by experts will reveal it as a cast. The best cast I have seen was of the pterosaur “Dawndraco” (or Pteranodon if you prefer) in the American Museum of Natural History (AMNH) pterosaur exhibit that ended in January. Just 2 weeks before I had seen the original at the University of Alberta, and was so convinced by the cast that I actually emailed the people who made it to confirm that it was indeed a cast (it wasn’t labeled as a cast, naughty AMNH!). Only because I knew it was not original was I able to spot the signs, but it was hard. The important thing to note here is that they are not just “fake” fossils that are made from someone’s head. These are (usually) skilled professionals who are basing their model off of a real fossil, and it is meant to look as close as possible to the original.
Original specimen of "Dawndraco kanzai", a pteranodontid from Kansas. Original housed at the University of Alberta
Cast of "Dawndraco kanzai" on display in the pterosaur special exhibit at the American Museum of Natural History
It's a bit hard to tell from the pictures as the lighting and angle is different, but I can tell you that they looked incredibly similar and the cast looked very real.

The final point to make with this is why museums have casts, especially as their large centre pieces. There are 2 reasons for this. First of all, fossils are rare. Despite what you may think by seeing all these fantastic fossils in museums, they are exceedingly rare. Not every museum has the money to buy a real fossil, or the ability to go out into the field and dig up their own, so they have to rely on casts. If not for casts, very few people would be able to see the specimens. Additionally, if fossils are rare, beautiful, complete fossils that look like Dippy are exceptionally rare. Most often fossils are found with bones missing, or smashed. Fossil replicas and casts allow for these missing bits to be filled in from other partial skeletons, which is what we call a composite skeleton. These can be made from skeletons that are incomplete so some bones are real, some are not. And of course, when we do find one of those exceptionally rare complete or near-complete fossils, casts allow us to share them with the world and show other people. And finally, fossils are of course extremely fragile. It can be very difficult to mount a skeleton in a way that isn't going to damage the specimen, especially if they are fragile. For this reason, museums will sometimes put the cast on display, and keep the original specimen in the collections in order to preserve it. Does it make it any less amazing? Personally, I don't think so. I'd rather know that the original is being conserved and properly looked after than see it on display in a museum. 

Fossil casts are not “just a fake”. They are replicas of rare and uncommon treasures. Without casts, most of the world would not be able to see these treasures. Dippy, for example, comes from the Morrison Formation of the USA originally. The likelihood of the Natural History Museum in London getting it’s hands on a complete skeleton of a large sauropod from the USA is pretty unlikely. So what would you prefer, no dinosaur at all? Or an exact replica of a real one that existed on another continent, allowing you to wonder in awe?

Thursday, 19 February 2015

People-snatching pterosaurs

I'm sure by now everyone has seen the recent Jurassic World trailer and palaeontologists and dinosaur fans alike have been salivating over it. The paleontological community is mostly in uproar over the scientific inaccuracies, mainly related to the lack of feathers on the theropod dinosaurs (for a few examples see Brian Switek here, Mark Witton, etc), but there have also been a few other comments about some problems with the creatures seen in the movies.

Of course for me, I notice how poorly done the pterosaurs are with respect to their contemporaneous dinosaurian relatives (remember, pterosaurs aren't dinosaurs!). I think Mark Witton put it the best:
I'm not going to go into the general inaccuracies of the pterosaurs (e.g. they should be covered in fibres, more meaty, etc), but I will talk about this problem of people-snatching pterosaurs. This is something that goes back quite far in Hollywood and dinosaur-related movies. There is always an image of a large pterosaur (typically Pteranodon) swooping down and picking up a person and flying away.
Nice grainy image of the Pteranodon flying away with a poor, unsuspecting woman in Jurassic World
Painting of a Peregrine falcon by John Gerrard
Keulemans. Notice the foot on the front bird and
how it is grasping the branch. 

Drawing of a Golden Eagle foot by Lydekker (1895)
showing the 4-digit structure of the foot.
There are several reasons for this, and I'm going to demonstrate this by comparing them with birds. In order to pick something up like that, you need some kind of grasping foot. Anyone who has had any type of raptor (as in the bird raptors - hawks, eagles, etc.) sit on their arm knows what this feels like. Their feet have 3 forward-facing clawed toes, and one reversed digit, known as the reversed hallux that faces backwards, allowing for a 4 digit grasping claw. This is what allows birds to perch on a branch, as they are able to grasp the branch to prevent themselves from falling off. This is also what allows these kinds of birds to pick up their prey as they swoop down. An important thing to note about that is that their prey is typically quite a bit smaller than they are (e.g. mice, rabbits, fish, etc.), although some of the larger birds have been known to kill bigger animals such as deer, antelope, etc. However, if a bird does this, it doesn't fly off with the prey, but rather will kill it and eat it in place. If it's going to fly off with it, it'll go for something much smaller. Another key bit of information with birds that do this - they have strongly muscled legs. Birds take off with their legs, and in comparison have very muscly feet and legs.

With that in mind, let's think about pterosaur feet. Pterosaurs have slender, weakly muscled feet. While the earlier non-pterodactyloids had 4 long, slender clawed digits that would have been flat on the ground during walking (in a plantigrade posture), the 5th digit was still elongated but did not touch the ground when walking (but was also not reversed as seen in birds). In more derived pterodactyloids, the 5th digit is almost entirely lost. None of these digits are reversed like in birds, and do not show the grasping structure as is typically shown in movies. Furthermore, pterosaur legs are weakly muscled, with most of their musculature occurring in the wings. They simply would not have had the musculature present to grasp prey in the same way that birds do.
Drawing of pterosaur hindlimbs from Witton (2013). A represents a pterodactyloid hindlimb (Anhanguera) with the nearly missing digit V, while B shows a non-pterodacctyloid (Rhamphorhynchus) with an elongated (but not clawed) digit V. 
The final "nail in the coffin" so-to-speak about people-snatching pterosaurs is the problem of weight. As I mentioned above, birds pick up small prey, typically much smaller than their body mass. Pterosaurs, however, are depicted picking up children or full grown humans. As it's typically Pteranodon being represented this way, we'll look at them. A large Pteranodon had a wingspan of about 6 m, and weighed probably somewhere around 35 kg if you go with the heavier estimates that I tend to favour from Witton (2008). The woman shown above that was carried off quite easily by a Pteranodon was probably somewhere around 60 kg at least. That means that it would have had to have been capable of carrying something and flying off with more than double it's initial mass. Considering there are already debates about if large pterosaurs were capable of flight (ok this isn't normally debated in Pteranodon, but I'm trying to prove a point!) there is no way it could fly if it was suddenly responsible for flying off with an additional 60 kg. Flight is hard enough as it is, and that additional mass would make it impossible. Then when you consider that 35 kg is a heavy estimate, moving do the lighter estimates and more "shrink-wrapped" pterosaurs to quote Witton, there is just no way.

So next time you see a pterosaur flying off with a person in tow in any kind of movie/tv show/etc., remember that it just couldn't happen. If pterosaurs were alive today, that would not be a concern we would have to deal with!

Special thanks to Tony Martin for giving me the idea for this post!

Witton, MP (2008) A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana B28: 143-158.
Witton, MP (2013) Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press, Princeton, USA. 304 pages. 

Saturday, 14 February 2015

Pterosaurs are not dinosaurs!

This post isn't the kind of post I normally do, but it stems from a conversation I had with someone at Science Borealis when they shared my Canadian pterosaur post and incorrectly called them dinosaurs. Being a pterosaur palaeontologist, this is something that I deal with constantly, the misconception that pterosaurs are 'flying dinosaurs'. I am going to try to explain why this is scientifically inaccurate.

The first thing to understand is that both the terms "dinosaur" and "pterosaur" are scientific terms with specific definitions and meanings, just like a mammal, reptile, or fish. All of these are scientific names that are used within the common tongue, but hold specific scientific definitions. Dinosaur stems from Dinosauria, the name of the group that includes all dinosaurs, while pterosaur represents a member of the Pterosauria or Pterosauromorpha. There is a tendency in popular culture to call any large extinct animal, particularly if it lived during the Mesozoic, a dinosaur. Unfortunately, this is incorrect. Pterosaurs were not dinosaurs, marine reptiles (like plesiosaurs, ichthyosaurs, and mosasaurs) were not dinosaurs, and neither was Dimetrodon, that weird sail-backed reptile from the Permian. In fact it's more closely related to you and I than it is to dinosaurs as it is a mammal-like reptile. To learn more about that, you can go to a blog I previously wrote for Jurassic Forest called Mesozoic Musings.

So how are pterosaurs and dinosaurs related, if at all? 

Pterosaurs and dinosaurs are closely related, meaning they share a number of features, but are still distinct groups, or clades as we call them in biology. They both belong to a group called the Archosauria, which includes crocodilians, dinosaurs (including birds, as they evolved from dinosaurs and therefore are dinosaurs by definition), and pterosaurs. Archosaurs share a number of characteristics including an antorbital fenestra (a hole in the skull in front of the eye) and teeth set in sockets. However, early in archosaurian evolution there was a split between crocodilians and their close relatives (the crurotarsans or pseudosuchians) and birds and their closest relatives, including dinosaurs and pterosaurs (known as the avemetatarsalians). Avemetatarsalia is a mouthful, but it's pretty easy to break down. Basically this group is united by a bird-like ankle, among other features. Within this group is another group called the Ornithodira, which means bird-neck, again uniting the group with features of the neck that are bird-like, and includes both pterosaurs and dinosaurs.

So now we know that pterosaurs and dinosaurs are united by a number of features including (but not limited to) an antorbital fenestra in the skull, teeth set in sockets and a bird-like structure of both the ankle and neck.
Cladogram from Nesbitt (2011) showing the relationships in the Archosauria, including the Avemetatarsalia, Ornithodira, Pterosauromorpha (including pterosaurs and their close relatives) and the Dinosauromorpha.

What features separate pterosaurs and dinosaurs?

There are a large number of features that distinguish each group, and they are very different anatomically, but I will only mention some of the major ones, specifically features that pterosaurs have and dinosaurs do not. Pterosaurs are highly modified for flight, and right now, we don't fully understand how they evolved. Several of the features that distinguish them from dinosaurs and other animals are related to this. The two most obvious features include:
1.  An elongated 4th digit (finger) to which a flight membrane attached. Pterosaurs have lost their fifth digit (their pinky finger), but have an extremely long 4th finger. Imagine you had no pinky, but a ring finger that was longer than the rest of your arm. These is a feature unique to pterosaurs, and found in all pterosaurs. 
2. Possession of a pteroid bone. In the pterosaur wrist, an additional bone is present called the pteroid.  This bone points most likely antero-medially (forward and into the middle in flight) and likely controlled the position of the wing membrane in between the wrist and the body. This bone is not found in any other animal.
Drawing of the wing of the pterosaur "Santanadactylus pricei" showing the elongated 4th finger and pteroid bone. Image from Witton (2013), redrawn from Wellnhofer (1991).
There are a number of other anatomical features that separate pterosaurs from dinosaurs that are unrelated to the wing, including several features in the skull (e.g. their skull is very long with respect to their vertebral column), vertebrae (e.g. their neck vertebrae are long compared to other vertebrae), and legs. In total, there are at least 13 characters that unite the Pterosauromorpha, that are not found in combination or at all in dinosaurs. 

Hopefully this has shown why palaeontologists cringe whenever someone calls a pterosaur a flying dinosaur. To quote Brian Switek's article on the same topic, "calling a pterosaur a dinosaur is an error of the same order of magnitude as saying that our species is a marsupial". So next time you talk about a pterosaur, or write an article about one, please don't call them a dinosaur! 

Nesbitt, SJ (2011) The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pages.
Wellnhofer, P (1991) Weitere Pterosaurierfunde aus der Santana-FOrmation (Apt) der Chapada do Araripe, Brasilien. Palaeontographica 215: 43-101.
Witton MP (2013) Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press, Princeton, USA. 304 pages. 

Friday, 6 February 2015

Canadian pterosaurs

It's pretty common knowledge that Canada is rich in fossils, and particularly well known for both the Cambrian Burgess Shale in the Rocky Mountains of British Columbia, and of course the Late Cretaceous dinosaur-bearing formations of southern Alberta. Additionally, marine fossils from a bit earlier in the Cretaceous are found from when Alberta was covered by the Western Interior Seaway, including fish, sharks, and marine reptiles. The Late Cretaceous formations are most famous for dinosaurs, but also preserve plants, mammals, turtles, other reptiles, and pretty much everything you would expect to find in the ecosystem. They also exist all over the province with body fossils round in all corners, while footprints and trackways are commonly found in the northwest and into British Columbia. If you're interested in learning more about the dinosaurs of Alberta, check out this Palaeocast interview I did with Dr. Phil Currie of the University of Alberta.

But what about the pterosaurs?

But we're not interested in the dinosaurs of Alberta. They are well documented, and we know they are common, but what about pterosaurs? In a Late Cretaceous environment full of dinosaurs, we would expect pterosaurs to be found as well. Other similarly aged formations around the world have pterosaurs, so Canada should too. In the slightly older marine sediments, pterosaurs such as Pteranodon and Nyctosaurus are found commonly (at least Pteranodon is) in the US, where the sediments come from the same Western Interior Seaway as found in Alberta. Pteranodon is the best known pterosaur by number, with thousands of Pteranodon fossils found so far from the chalk formations of Kansas. Moving into the latest Cretaceous where the dinosaur fossils dominate, similarly aged formations frequently uncover azhdarchid pterosaurs, specifically large ones. In the Hatzeg basin of Romania, Eurazhdarcho represents a smaller azhdarchid, while Hatzegpteryx is a massive 10-11m wingspan pterosaur, and pterosaur fossils are relatively common. Moving southeast, there's the giant Arambourgiania from Jordan (pictured below), and then into Texas we have the best known Quetzalcoatlus, both a smaller form, and the giant Q. northropi.
The giant pterosaur Arambourgiania with a giraffe and human for scale. Image copyright Mark Witton.

Alberta pterosaurs

Knowing that similarly-aged rocks all over the world produce pterosaur fossils, we would expect to find them in Alberta. However, while they do exist, they are very uncommon. The first pterosaur found in Canada was a partial first wing-finger phalanx from the Oldman Formation of Alberta described in 1972[1]. It was a pretty unexciting find (at least in terms of the material present), and represented a pterosaur with a wingspan of around 3.5 m. 10 years later, a long bone shaft and cervical (neck) vertebra were found and attributed to the giant pterosaur from Texas, Quetzalcoatlus[2]. However, more recently the long bone shaft has been interpreted as a possible elongated cervical vertebra, as they are very long and can look like long bones if the ends have been broken off [3].
The first pterosaur from Canada - a first wing phalanx from the Oldman Formation in Alberta. Image from Russell (1972).
An incomplete cervical vertebra in dorsal view of cf. Quetzalcoatlus. Image from Currie and Russell (1982).
So far, there is only one partial associated skeleton that likely represents a single animal and consists of a cervical vertebra, rib, humerus, pteroid, metacarpals III and IV and a tibia (TMP 92.83) [3-4]. This is thought to have a wingspan of about 5 m, corresponding with the smaller Quetzalcoatlus from Texas. One of the interesting features of this specimen is that the tibia has a velociraptorine tooth embedded in it, likely from the dinosaur Saurornitholestes, thought to be a result of scavenging [4].
Tibia of TMP 92.83 showing bite marks (a, b, c) and an embedded velociraptorine tooth (d). Image from Currie and Jacobsen (1994).
Right humerus of TMP 92.83. Image from Godfrey and Currie (2005).
Distal end of a non-azhdarchid wing
metacarpal from the Oldman Formation.
Image from Currie and Padian (1983).
A few other fragmentary isolated bits have been found including several cervical vertebrae, a few wing bones (humeri, metacarpals, wing phalanges, etc.), and some leg bones (femora, tibiae, and a metatarsal). The majority of the specimens are thought to be azhdarchids, with smaller bones possibly representing Montanazhdarcho and larger ones being similar to Quetzalcoatlus. However, there are a few that seem to represent a species other than an azhdarchid. This is represented by two partial wing (4th) metacarpals, one of which was originally described as a tibia [5], but is clearly a metacarpal. These distal metacarpals closely resemble the ornithocheiroid pterosaurs Santanadactylus and Pteranodon, suggesting maybe some ornithocheiroids were present in Alberta as well [3]. Unfortunately with so few and fragmentary remains, we don't know for sure. Also unfortunate is the lack of skull material from Alberta, with no cranial specimens reported so far.

Pterosaur track from the Wapiti Formation of
northwest Alberta. Image from Bell et al. (2014).
Of course body fossils aren't the only fossils we find. There is one reported footprint from a pterosaur from northern Alberta, southwest of Grande Prairie near the Wapiti River. This print is interpreted as a right manus (hand) print from a large pterosaur, estimated at 7.7 m wingspan [6]. It is currently the largest pterosaur print known from North America. Unfortunately, as it is an isolated print with no associated bones it is not possible to assign it to a group, but has tentatively been assigned to the ichnospecies (what we call specific types of trace fossils) Haenamichnus. Additionally, similarly large pterosaur tracks have been found in the Alaskan Cantwell Formation possibly of similar age to the Wapiti Formation in Alberta.

Other Canadian pterosaurs

Of course this post is about pterosaurs in Canada, not just Alberta. So is there any evidence of pterosaurs in the rest of Canada? Well the short answer is there is very little. I mentioned above that no cranial material had been found of pterosaurs in Alberta, so imagine how excited we were in 2010 when the anterior portion of an upper jaw was described of a new pterosaur Gwawinopterus (which I think is an awesome name) from Hornby Island in British Columbia. It was interpreted as an istiodactylid pterosaur from the Upper Cretaceous, but was based on a fairly unimpressive specimen from a nodule with a lot of teeth and not much else to see [7]. Unfortunately, that specimen has consequently been reinterpreted as a fish [8], so there is still no known pterosaurian cranial material from Canada. 
Image of "Gwawinopterus", now known to be a saurodontid fish rather than a pterosaur. Image from Arbour and Currie 2010.
While "Gwawinopterus" may not be a pterosaur, there is still a limited amount of evidence of pterosaurs from Hornby Island, which is currently being worked on [9]. The other potential place that would be a prime candidate for finding pterosaurs in Canada would be Saskatchewan. However, to my knowledge, no evidence of pterosaurs has ever come out of the province. If anyone knows differently, please let me know!

Why are they so uncommon?

Now that we've gone through the relatively desolate pterosaur fossil record of Canada, we can start to think of why this is the case. There is no reason to believe that pterosaurs were not present in these ecosystems as we know that they existed (sometimes in large number) in similar ages and environments around the world, and we have a number of their fossils from Alberta, even if they are rare and fragmentary. The answer then must be in pterosaurs themselves. Anyone who works on pterosaurs knows how uncommon they are in the fossil record, and how notoriously poorly preserved they can be. There are a few examples of pterosaur bone beds, but these are extremely uncommon and you can read about them in one of my previous posts if you're interested. The main reason for this is their hollow bones. You may recall that pterosaur bones are typically extremely thin-walled, and their bones are mostly full of air, a product of their respiratory system which we call pneumaticity. This, unsurprisingly, makes their bones extremely fragile and not as commonly fossilised as their contemporaries. The fact that birds are also uncommon in the fossil record of Alberta, and share this feature of highly pneumatic skeletons, may support this. It may just be that the environment of the Late Cretaceous of Alberta was not receptive to the fossilisation of extremely fragile pterosaur bones. 

Of course we'll keep looking, and maybe we'll find a pterosaur bonebed in Dinosaur Provincial Park... If anyone knows of any pterosaurs lying around from Canada that haven't been described, please get in touch! I'm always looking for things to procrastinate my PhD a bit more ;)

1. Russell, DA. 1972. A pterosaur from the Oldman Formation (Cretaceous) of Alberta. Canadian Journal of Earth Sciences 9: 1338-1340.
2. Currie, PJ and Russell, DA. 1982. A giant pterosaur (Reptilia:Archosauria) from the Judith River (Oldman) Formation of Alberta. Canadian Journal of Earth Sciences 19: 894-897.
3. Godfrey, SJ and Currie, PJ. 2005. Pterosaurs. In Currie, PJ & Koppelhus EB (eds): Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Indiana University Press, Bloomington, 292-311.
4. Currie, PJ and Jacobsen, AR. 1994. An azhdarchid pterosaur eaten by a velociraptorine theropod. Canadian Journal of Earth Sciences 32: 922-925. 
5. Currie, PJ and Padian, K. 1983. A new pterosaur record from the Judith River (Oldman)Formation of Alberta. Journal of Paleontology 57: 599-600.
6. Bell, PR, Fanti ,F, and Sissons, R. 2013. A possible pterosaur manus track fro the Late Cretaceous of Alberta. Lethaia 46: 274-279.
7. Arbour, VM and Currie, PJ. 2010. An istiodactylid pterosaur from the Upper Cretaceous Nanaimo Group, Hornby Island, British Columbia, Canada. Canadian Journal of Earth Sciences 48: 63-69.
8. Vullo, R, Buffetaut, E, and Everhart, MJ. 2012. Reappraisal of Gwawinopterus beardi from the Late Cretaceous of Canada: a saurodontid fish, not a pterosaur. Journal of Vertebrate Paleontology 32: 1198-1201. 
9. Arbour, VM and Currie, PJ. 2010. An istiodactylid pterosaur from the Nanaimo Group, Vancouver Island, British Columbia, Canada. In Flugsaurier 2010: Third International Symposium on Pterosaurs abstract book. Acta Geoscientica Sinica 31, Supp. 1: 3.