Monday, 22 June 2015

Palaeontology in Canada

A few weeks ago I had the opportunity to attend the Canadian Society of Vertebrate Paleontology meeting in Kelowna, BC. It was a fantastic meeting full of Canadians, and people working in Canada on vertebrate palaeo including some of the fields brightest minds. We had 2 full days devoted to talks and posters, ranging from fish to mammals and everything in between – lots of dinosaurs, marine reptiles, pterosaurs (from me of course), ichnology (fossil trackways), crocodiles, teeth, macroevolution, and the list goes on. I won’t discuss the research presented as much of it is currently unpublished, in prep or in press, but I can tell you that there is a lot of awesome stuff coming out of Canada in palaeontology right now.

In the last talk, David Evans from the Royal Ontario Museum talked about how we’re in another “golden age” of dinosaur discovery in Canada, and I think this is an important and interesting idea. He had a neat graph that showed new dinosaur species named over time, and we’re currently on a strong upward trend even when comparing to the early 1900’s when dinosaur hunting in Canada was getting going with the likes of Barnum Brown, Lawrence Lambe and more.

Of course this is something that can be said with the entire world, with new fossil-rich areas being found in China, Brazil, Africa, etc. However, I think it’s important to highlight and remind people just how significant Canada is in understanding the history of the Earth and in palaeontology. We have numerous world famous fossil sites representing almost animals from the earliest existence up to the most recent fossils, from vertebrates to invertebrates to plants, and several very important sites from coast to coast. There are too many to list, but here are a handful of sites or significant fossil finds from Canada that are extremely important in understanding the past and how our world came to be how it is today.
  1. The Burgess Shale – I’m sure most of you have heard of this - up in the Rocky Mountains of Yoho National Park, British Columbia, an exquisite fossiliferous area represents some of the earliest recognizable animals from the Middle Cambrian, from a time known as the Cambrian Explosion. This period represents a time of significant evolution, and these fossils show us what the Cambrian seas would have looked like, with some of the first vertebrates like Pikaia, and numerous arthropods like Hallucinogenia (named because it is so weird you just must be hallucinating), and Anomalocaris. The reason this is so significant is that these animals are known almost exclusively from soft tissues, which are difficult to preserve in the fossil record. Yet here, thousands of soft-bodied organisms are preserved that give us a window into an early stage of evolution in many animal groups. Recognised for it’s importance, the Burgess Shale is part of the Canadian Rocky Mountain Parks UNESCO World Heritage Site named in 1984.
    Anomalocaris reconstruction by Nobu Tamura
  2. Dinosaur Provincial Park – And of course I have to talk about this as well. Dinosaur Provincial Park (DPP) is located in southern Alberta, and is also a UNESCO World Heritage Site, known for – you guessed it – dinosaur fossils. From the Late Cretaceous, this area is one of (if not THE) best place in the world to view the ecosystems from this time period. Not just dinosaurs are found here, but also turtles, pterosaurs, crocodilians, mammals, plants, and more. Basically anything you would expect to be in that kind of ecosystem is represented, from big animals like T. rex and Triceratops to smaller dinos like Saurornitholestes (although the smaller the animal the less common they are). Dinosaurs have been coming out of DPP for well over 100 years, and with the continued field work of groups like Phil Currie and the University of Alberta, David Evans at the Royal Ontario Museum, and of course the Royal Tyrrell Museum in Drumheller where most of the material is housed, it’s not going to stop anytime soon. If you want to hear more about the dinosaurs in Alberta and DPP, check out my Palaeocast episode with Phil Currie.
    Hoodoos in Dinosaur Provincial Park. Photo by Joanne Merriam
  3. Ellesmere Island – Up in the frozen north of Nunavut lies a large island where several fossils have been found. While not traditionally thought of as a fantastic place to look for fossils, northern Canada has yielded a significant number of things like plesiosaurs, dinosaurs, and from Ellesmere Island – Tiktaalik. Tiktaalik is an amazing fossil, what we might call a “transition fossil”. From the Late Devonian period, long before dinosaurs when animals were just starting to colonise the land, Tiktaalik shows a perfect ocean to land transition, somewhere between a water-dwelling fish and a land-dwelling tetrapod (four-legged animals). It had fish gills, scales, and fins, but a mobile neck and pectoral girdle, ribs, and lungs of a tetrapod, as well as many bones and joints that lie somewhere in between. It is a true mosaic of features and just might be somewhere in the middle of fish and tetrapod, which has led to the term “fishapod”.
    Reconstruction of Tiktaalik by Obsidian Soul.
    Tiktaalik fossil from Ellesmere Island. Image by Eduard Solà.
  4. Carboniferous of Nova Scotia – There are two sites in Nova Scotia, both dating to different parts of the Carboniferous Period that deserve a mention. The first one is the oldest of the two sites, found at Blue Beach. This is not publicly or scientifically well known, but represents an important period in tetrapod evolution, as it represents part of a time period known as ‘Romer’s Gap’. During the Early Carboniferous, there are a conspicuously low number of tetrapod fossils or sites bearing these known from around the world, leading palaeontologists to wonder what happened during this time. Is this actually a gap where few tetrapods existed? Or is it some kind of bias preventing them from being preserved or found? Well thanks to some fossils recently described from Blue Beach, we are starting to understand this period a bit better, and the evidence is suggesting the gap is not a real gap in tetrapod evolution
  5. Hylonomus by Nobu Tamura
    • Later on in the Carboniferous brings us to Joggins Fossil Cliffs. Here fossils of tetrapods, fish, and much more are found, often within fossilized "tree" stumps (actually a club moss or lycopodiphyte Sigillaria, which is a tree-like plant). This area was a lush, forested swampland 310 million years ago, from the so-called "Coal Age", known for the large number of coal seams produced by the coalified. The trees are preserved in situ, meaning they are in their life position, standing upright. Often, these trees are hollowed out, and vertebrate fossils are found within the tree trunks, including amphibians and some of the earliest reptiles, including Hylonomus, the first indisputable reptile from fairly complete remains, and Archaeothyris and Protoclepsydrops, the earliest synapsid reptiles.
  6. Mistaken Point, Newfoundland – Here we have fossils from the earliest of animal evolution, the Ediacaran. These rocks date from the Precambrian, approximately 550 million years old. Mistaken Point has some of the most diverse and well-preserved fossil assemblages from this time period, an important time in organism evolution on Earth. The fossils consist of imprints of soft-bodied organisms, unlike anything alive today, typically of frond-like and leafy forms with or without stalks, some with branching network-like forms, and others more like spindle-shapes with pointed ends. The exact affinities of these fossils are still poorly understood and heavily studied, but it is difficult when they are so unlike anything today or even other fossils. This is definitely an important locality in understanding the history of our planet.
    The 'spindle-shaped' fossil Fractofusus from Mistaken Point
    (Image by MistakenPoint)
Of course this is not it for important Canadian fossil localities. From East to West, North to South, every province and territory has it’s share: the Peace Region of northeast BC is known from some of the best ichnological finds with dinosaur, bird, and more footprints, as well as body fossils from the Late Cretaceous of the small islands of Denman and Hornby; Alberta has some fantastic palaeobotany sites such as Joffre Bridge of Paleocene age as well as amazing ammonites that have been preserved in such a way that the gemstone ‘ammolite’ is a favourite in jewelry; Saskatchewan has it’s share of Late Cretaceous dinosaur and marine vertebrate finds, as well as some mammal fossils from the Cypress Hills Formation; Manitoba is home to the Pierre Shale Formation, a marine formation known for many marine fossils including the Tylosaurus, a mosasaur, including 'Bruce' who is the largest mosasaur on display in the world at 13 m long; Ontario is home to the Gunflint Chert, an early Proterozoic (approx. 1.8 billion years old) site with some of the earliest fossils of cyanobacteria; Migwasha National Park in Quebec is home to more Devonian aged fossils including fish that are thought to be ancestral to tetrapods, and well preserved plant spores; Prince Edward Island was recently in the news for a new find, the only reptile known from the specific time period 300 million years ago; the Yukon is best known for it's Pleistocene Ice-Age fossil mammal sites including mammoths; and finally the Northwest Territories has a number of Paleozoic sites with marine invertebrate fauna such as brachiopods, trilobites, corals, and also marine vertebrates like acanthodian fishes. 

Canada is full of fossils, and is very important palaeontologically speaking for a number of different plant and animal groups, ages, and evolutionary questions. This is by far not a comprehensive list, but just a few examples of what Canada has to offer in palaeontology. Let me know of any other famous ones I’ve missed – I’m always interested in hearing about Canadian palaeo and I’m sure there are some out there I haven’t heard of…

Tuesday, 9 June 2015

Predation traces in the fossil record

Traditional palaeontology as we think of it consists of finding bones, shells, etc., and describing them and mounting the skeletons in a museum to look at. However, most of the actual science is looking at things like behaviour. From looking at bones, how can we infer the animal’s behaviour? And more than that, how can we figure out things like predation and interactions between different animals?

Of course, your average bone isn’t going to tell you this kind of information, but bones with bite traces can start to give us these hints. Bite traces on bones can tell us that the animal was attacked, and in what way. If the bone shows evidence of healing, then the animal was obviously attacked while it was still alive and survived the attack. However, if there is no evidence of healing (and this is substantially more common), then the animal was dead. Whether or not it was a fatal blow where the animal was attacked and died, or whether it was dead for some time before being chewed on can be harder to tell.

Bite traces on Late Cretaceous dinosaur bones showing
serrated marks. From Jacobsen and Bromley (2009).
Majungatholus tooth showing denticles and bite traces
showing denticle marks. From Rogers et al. (2003).
Different kinds of bites can leave different traces on the bone, as well as different kinds of teeth. Fine detailed analysis can help us understand exactly how these marks were made, and by what kind of animal. For example, teeth with denticles (small tooth-like projections) can often leave drag traces from the denticles on the bone after biting and dragging, which can only be made by denticles or serrated teeth. Many theropod dinosaurs have denticles, including tyrannosaurs, dromeosaurs, troodontids, etc. Conversely, many crocodilians do not have denticles or serrated tooth, but rather have a simple cone-shaped tooth, so the lack of serration traces can suggest this kind of predator (but does not necessarily mean that). Additionally, different bite traces can indicate different behaviours such as gnawing. Mammalian gnawing leaves very distinct traces on the bones that are not produced by other means. This has been seen in Late Cretaceous dinosaur bones that were gnawed on by multituberculate mammals. Bite traces can range from punctures (when the tooth breaks through the bone cortex) and pits (a single vertical bite with no cortical breakage), to scores and drags, caused when the animal bits and drags its teeth across the bone.
Multituberculate gnaw traces on several Late
Cretaceous bones. From Longrich and
Ryan (2010). 

Unfortunately, determining the exact predator can be extremely difficult, if not impossible in many cases. Generally we can narrow it down to “theropod”, “crocodile”, “mammal”, or other broad categories like that. If you’re in an area where there are very few theropod predators for example, than you can make a reasonable assumption that that is what caused it. Or if you have other evidence, like for example numerous shed teeth from a tyrannosaur like Albertosaurus, then it’s not unreasonable to assume that bite traces may be due to Albertosaurus.

However, there are cases where the predator can be identified. One example of where the predator is clear is a beautifully preserved azhdarchid pterosaur from Alberta. The animal consists of a partial skeleton (7 bones to be exact) with wing, leg, and vertebrae present. The coolest part of this is that one of the long bones has several bite traces on the shaft on one end (Currie and Jacobsen 1995). This alone would not be enough to identify the cultprit. However, conveniently, it also has a partial tooth still embedded in the bone. This tooth can be identified as a dromaeosaurid tooth. The only dromaeosaurid known from this time in this area of the world is Saurornitholestes, which is pretty well known from teeth and a few skeletal remains in Dinosaur Provincial Park, Alberta, where this pterosaur was found. It’s a pretty cool specimen, especially considering how rare pterosaur remains are in Alberta. To find one with bite traces and a tooth is pretty cool! Teeth are not infrequently embedded in bone, and this has happened in other pterosaur remains, as well as dinosaurs and many other extinct animals.

Azhdarchid pterosaur long bone with tooth embedded (right side, bottom of the bone). Image by Liz Martin. 
Close up of pterosaur bone with tooth emedded and bite traces visible. Image by Liz Martin
The nature of the bite can also tell us about the nature of the animal making the traces. Most bite traces found in the fossil record are typical of scavenging. They show no evidence of healing, and are often found in areas that wouldn't typically be covered in bites if it were something like live inter or intra-specific competition such as the ends of bones. However, there are also bite traces in the fossil record that show evidence of healing. A tyrannosaur (Daspletosaurus) shows evidence of several healed bites on its skull, leading the authors to believe this was some kind of intra-specific competition with other Daspletosaurus (Hone and Tanke 2015).


Examples of dermestid mandible marks on
Jurassic Camptosaurus bones. From Britt
et al. (2008).
Of course predation traces are not restricted to vertebrates. They are commonly found on things like ammonites, which were often predated on by mosasaurs in the Cretaceous oceans. And of course predation traces or scars are not limited to being caused by vertebrates. Many invertebrates are capable of scarring bones and shells. Dermestid beetles are well known today for decomposing flesh and cleaning of skeletons, but they can also leave traces on the bones, and have been found in dinosaur fossils. Molluscs are known for using their "thorny tongue" or radula to scrape away shells in order to get inside the shell at the animal living inside. These bore-holes are common in modern shells and frequently seen in the fossil record as well. Sometimes these borings are stopped partway through the shell, and considered "unsuccessful", while they are often termed "successful" as the hole goes through the shell to the unsuspecting clam or oyster within.

In addition to predation traces, there are also several other kinds of marks that can be found on a specimen, including trample traces, transport marks (abrasion, etc.), and other kinds of breakage indicators. This leads to the field of taphonomy, which is basically everything that has happened to an animal from the time it dies to when it is discovered by a palaeontologist. These things tell us about the environment it lived in and aspects of its preservation, and is much to wide of a topic to discuss here. Maybe next time!

Determining the different marks or traces on fossil bones, where they came from, and what other animal may have caused them can be extremely difficult, despite the fact that these marks can be extremely common in the fossil record.

NOTE: Since posting this, Lothar Vallon has pointed out that there is a specific scientific definition for the use of marks vs. trace, in case anyone is wondering why I use trace in most places and mark in others. You can see his comment below!

References
Britt, BB, et al. 2008. A suite of dermestid beetle traces on dinosaur bone from the Upper Jurassic Morrison Formation, Wyoming, USA. Ichnos 15: 59-71.
Currie, PJ, and Jacobsen, AR. 1995. An azhdarchid pterosaur eaten by a velociraptorine theropod. Canadian Journal of Earth Sciences 32: 922-925.
Hone, DWE, and Tanke, DH. 2015. Pre- and postmortem tyrannosaurus bite marks on the remains of Daspletosaurus (Tyrannosaurinae: Theropoda) from Dinosaur Provincial Park, Alberta, Canada. PeerJ 3: e885.
Jacobsen, AR, and Bromley, RG. 2009. New ichnotaxa based on tooth impressions on dinosaur and whale bones. Geological Quarterly 53: 373-382.
Longrich, NR, and Ryan, MJ. 2010. Mammalian tooth marks on the bones of dinosaurs and other Late Cretaceous vertebrates. Palaeontology 53: 703-709.
Rogers, RR, et al. 2003. Cannibalism in the Madagascan dinosaur Majungatholus atopus. Nature 422: 515-518.

Thursday, 23 April 2015

Fossils and Geology

A few weeks ago, I was demonstrating on a geology field course in Wales. It was fantastic for several reasons - I had a great time, it was out on the coast of Wales mostly on the coast, and more importantly, it reminded me of my love for geology. It's been a while since I've done some geology, about 6 years to be exact, and I really enjoyed looking at rock types, folds, faults, and all those other fun things.

One of the other things I remembered on the trip was the occasional animosity that is seen between geologists and palaeontologists. I remember in my undergrad geology classes how geologists would rant about how they hated palaeontology and fossils, and vice versa for palaeontologists regarding rocks and geology. Then in Wales, one of the lead staff members would make a face each time we found a fossil or discussed them. While I will admit to preferring fossils over rocks (obviously, I'm a palaeontologist...), there is one important thing to remember: palaeontology and geology NEED each other. And palaeontology especially would not exist without geology.

To start with the obvious side, fossils are basically rocks made of bones, shells, soft tissue, etc. of long dead animals or plants. The process of fossilisation means that the organic material is literally replaced over time with rock and mineral. This is done primarily by highly-mineralised pore water in the ground and sediment. As an animal dies and is buried by sediment, highly mineralised water flows through the sediments and around the dead body, and over time, the minerals in the water will replace the tissues of the body, primarily the hard tissue. Soft tissue is generally decayed and broken down, while the hard tissues of bone and teeth remain replaced as rock. Being able to tell what type of rock now makes up the fossils can be important in figuring out the environment that the fossil was deposited in. Even more important is that the rocks surrounding the fossils can contain clues about how the animal died and the environment in which it lived. For example ripples in sandstone tell us there was a current, while fine laminated sediment like mudstone tells us that the animal died in a quiet low-energy environment like a lake or lagoon where fine sediments settled over a long period of time to the bottom. The presence of specific minerals can tell us things as well. Pyrite is formed in low-oxygen environments, so pyritised fossils mean a low-oxygen environment like the bottom of a deep ocean. Having a background in geology can definitely help in understanding palaeontology, specifically in order to understand the environment that the plant or animal was living in.

On the other hand, palaeontology and fossils can tell us specific things about the environment and geology of an area. There are fossils called Index Fossils, which are fossils that lived for a very little amount of time, and a specific time. They are obviously identifiable, and the fact that they are only found at very specific times means that when they are found, we know exactly what time period those fossils come from. Additionally, fossils can be helpful in determining geological structures like bedding planes. Sedimentary rocks are deposited in layers called beds. These layers are deposited as horizontal beds as sediments fall from lakes or rivers, for example. Through geological processes, these beds can be folded, faulted and overturned, making it difficult to tell which way is up and what has happened geologically speaking. This is where fossils, and in particular trace fossils can come in to help clear up some of the problems. If an animal is walking around on the bottom of the ocean or lake, the footprints or traces will be on a single bedding plane. If preserved and fossilised, these traces can tell us which way was "up" on the bed when it was deposited. This can help us understand what geological processes have happened in the past in terms of folding and faulting.
Trilobite trace fossil from Wales. This showed at this particular locality that the bedding planes here were nearly vertical, and allow us to see that there was some significant folding in this area, specifically an an anticline in the bay where this was found.
So as you can see, geologists need palaeontologists, and palaeontologists need geologists. Or even better, it's important for geologists and palaeontologists to learn about each others subject. So here it is - palaeontologists: stop hating on geology and rocks! You need it! And now geologists: fossils aren't so bad, and they teach us things every day! We need each other, so stop with all the malice.

Tuesday, 14 April 2015

Late Cretaceous of Romania

For the last 2 weeks, I have been on fieldwork in Transylvania (western Romania) with the University of Southampton Vertebrate Palaeontology group. This is part of a long-term project between several groups including British, American, and Romanian organisations looking at the vertebrate palaeontology of this area. This is the 3rd year this Easter trip has run, and was the biggest yet (25 strong at it's largest!).

The area was first recognised as being an important vertebrate palaeontology location by Baron Franz Nopsca, the Hungarian aristocrat and palaeontologist of the late 1800's and early 1900's who is widely thought to be the kickstarter of palaeontology in the region.

Geological Setting

When mentioning fieldwork in Romania, and in particular Transylvania, most people think of vampires, castles and mountains, and have no idea about the palaeontological significance (or even topography) of the region. While there are outcrops of many ages, the areas that we are interested in are of Late Cretaceous (Maastrichtian) age, deposited approximately 72-66 million years ago. This is the last time period of the Cretaceous, culminating in the end Cretaceous extinction 66 million years ago that saw the extinction of pterosaurs, non-avian dinosaurs, and many more. There are the Carpathian mountains, and also several plateaus and rivers where much of the fossils come from.

In particular, there are 2 areas of interest in Transylvania that yield Maastrichtian deposits - the lesser known sedimentary Transylvanian Basin in the area of Sebeş and Alba Iulia, and the famous Haţeg Basin to the southwest. During the Late Cretaceous, this area was characterised by an island environment, and is represented by both terrestrial and marine deposits in the area, with the younger terrestrial/continental deposits overlying the older marine sediments. Numerous islands were found in this area of the world, with Haţeg Island being one of the major islands. 

Palaeontology of the Area

Transylvanian Basin

Râpa Roşie
There are numerous sites in the Transylvanian Basin that have yielded vertebrate remains, and many different groups of animals have been found. At the river site Sebeş-Glod the theropod Balaur bondoc was found[1], which has an interesting double sickle-clawed foot and has proven to be highly controversial in it's placement among theropods. Balaur was a small theropod estimated at just 1.5m in length from an incomplete skeleton unfortunately lacking a skull. Also from Glod is the azhdarchid pterosaur Eurazhdarcho, which had a wingspan of around 3m and is known from an incomplete skeleton as well with no skull[2]. Further finds include additional dinosaurs (Zalmoxes, titanosaurid sauropods), turtles, crocodylomorphs, and more. At Petreşti (also a river site) a number of fossils have been found including pterosaurs and the ornithopod dinosaur Zalmoxes[3]. A productive site at Lancrăm has produced fossils of numerous groups including primarily titanosaurs (Magyarosaurus) and ornithopods (Telmatosaurus and Zalmoxes), but also turtles and crocodylomorphs[4]. Oarda de Jos is another river locality that may have represented a bird breeding colony[5], but also includes turtles, amphibians, fish, lizards, crocodylomophs, dinosaurs and mammals [4]. While it has been suggested that pterosaur material has been found here, this was actually a misidentified turtle [6-7]. The final site I will highlight from the Transylvanian Basin is that of Râpa Roşie, the "Red Ravine". This is a breathtaking site that reminds me of the badlands of southern Alberta, but with massive imposing red cliffs. Vertebrate fossils from here include crocodylomorphs like Allodaposuchus, turtles, azhdarchid pterosaurs, titanosaurid sauropods, ornithopods (both Telmatosaurus and Zalmoxes), ankylosaurs, and theropods[4]. In the Transylvanian Basin alone there are numerous vertebrate groups represented from several fossil-bearing localities showing just how rich this region is, and this is just a snapshot of all the localities! 
The foot of Balaur bondoc from Csiki et al. [1]

Haţeg Basin

Vadu
Sînpetru sandstone











While the Transylvanian Basin is certainly fossiliferous, the Haţeg Basin is the more famous of the two, and arguably even more fossil-rich. The first site to discuss is near the town of Sînpetru (or Sânpetru sometimes), and is the stratotype of the Sînpetru Formation. This is now a protected site so no hammering or digging is allowed, but you can still go and take a look to see if anything is there on the surface. Here, several dinosaur, crocodile, turtle and mammal fossils have been found. Not far from Sînpetru is the river site of Vadu, which is set in the middle of the basin with the Carpathian Mountains on all sides. This is a very shallow river with fossils consisting of birds, dinosaurs, crocodylomorphs and much more. Another interesting site is Tustea, which is best known for a large number of dinosaur eggs, including egg clutches, which are thought to be from the ornithopod dinosaur Telmatosaurus or the titanosaurid Magyarosaurus due to the presence of their fossils in this region as well. Additionally, turtle, crocodylomorph, mammal, and pterosaur fossils have also been found here, one of the most famous perhaps being that of the giant pterosaur Hatzegopteryx thambena, which was described first from here and another site Vălioara[8]. Finally one of the most active sites in recent years is that of the Barbat River at Pui. Numerous dinosaur fossils have been found here including the ornithopods Telmatosaurus and Zalmoxes, pterosaur fossils like the recently described short-necked azhdarchid vertebra[9], turtles (e.g. Kallokibotion), crocodylomorphs, mammals, and more. 
Artists impression of a short-necked azhdarchid pterosaur based on a cervical vertebra from the Barbat River described by Vremir et al. [9]. Image copyright Mark Witton.

 Interpretations and observations

Little Magyarosaurus being tormented by a flock of
Hatzegopteryx - a possible use of terrestrial stalking. Image
copyright Mark Witton.
Interpreting the palaeoecology and palaeobiology of different animals in this region has been a heavily debated and hot topic in palaeontology over the last few decades. Island dwarfism is a process that applies today to animals living on islands where their size is limited and over many generations animals get smaller and smaller as their resources are limited. Nopsca first suggested this was what had happened on Haţeg Island in the Late Cretaceous since most of the dinosaurs in particular are significantly smaller than their contemporaries in other parts of the world. For example, Magyarosaurus was a titanosaurid sauropod dinosaur, a kind of large long-necked dinosaur. Unlike what we are used to seeing as the giant long-necked dinosaurs like Apatosaurus, this dinosaur was less than 2m tall. Additionally the ankylosaur Struthiosaurus is smaller than other members of its group. Currently, very few theropod remains are known, and the best known is that of Balaur, which is similar in size to a small chicken at approximately 50 cm high and 2 m long. With theropods being so rare, what would the main predator in such an environment be? Well one thought is that the giant pterosaur Hatzegopteryx terrorised the land animals as the major predator[10]. With this animal being by far the largest found so far, this is a well supported theory. These points all suggest that the Late Cretaceous islands of Romania were a strange and dangerous place to live.

New finds?

 
Corvin Castle in Hunedoara
Barbat River in the snow
Unfortunately I can't reveal too much about our trip yet as there are publications imminent and forthcoming, but I will say that we had a very productive year. We visited a number of sites in both the Transylvanian and Haţeg Basins, and found a lot of bone. Some highlights include some pterosaur material (both cranial and postcranial), a partial ornithopod dinosaur skeleton, and some additional bits and bobs. We had a great time wading through rivers, getting snowed on, checking out little museums, and some of us even got to go see a castle (although not the famous Dracula castle, it's still an awesome castle). 

Keep following for news on the new finds as they become available. I'll update when we have more news!

Special thanks to Prospectiuni and the National Geographic Society for funding for this trip. Without them, this trip would not be possible!








References
1. Csiki, Z., et al. 2010. An aberrant island-dwelling theropod dinosaur from the Late Cretaceous of Romania. PNAS 107: 15357-15361.
3. Vremir, M., et al. 2014. Petreşti-Arini — An important but ephemeral Upper Cretaceous continental vertebrate site in the southwestern Transylvanian Basin, Romania. Cretaceous Research 49: 13-38.


4. Vremir, M. 2010. New faunal elements from the Late Cretaceous (Maastrichtian) continental deposits of Sebeş area (Transylvania). Terra Sebus. Act Musei Sabesiensis 2: 635-684.


5. Dyke, GJ., et al. 2014. A drowned Mesozoic bird breeding colony from the Late Cretaceous of Transylvania. Naturwissenschaften 99: 435-442.
6. Grellet-Tinner, G., and Codrea, VA. In Press. Thalassodromeus sebesensis, an out of place and out of time Gondwana tapejarid pterosaur. Gondwana Research. In Press - online July 2014.
7. Dyke, GJ., et al. In Press. Thalassodromeus sebesensis — A new name for an old turtle. Comment on "Thalassodromeus sebesensis, an out of place and out of time Gondwana tapejarid pterosaur", Grellet-Tinner and Codrea (online July 2014 DOI 10.1016/j.gr.2014.06.002). Gondwana Research. In Press - online August 2014.
8. Buffetaut, E., et al. 2003. Giant azhdarchid pterosaurs from the terminal Cretaceous of Transylvania (western Romania). Geological Society, London, Special Publications 217: 91-104.
9. Vremir, M., et al. 2015. A medium-sized robust-necked azhdarchid pterosaur (Pterodactyloidea: Azhdarchidae) from the Maastrichtian of Pui (Haţeg Basin, Transylvania, Romania). American Museum Noviciates 3827:1-16.





Sunday, 29 March 2015

Ptiny pterosaurs of the Late Cretaceous

Forgive me for the title, it was just too tempting when talking about little pterosaurs!

Azhdarchid pterosaurs are known from the Late Cretaceous mostly of North America, Europe, and Africa, with fossils found in Alberta, Montana, Texas, Romania, the Baltics and more. Several genera are known ranging from 2.5 m wingspan Montanazhdarcho all the way up to 10-11 m Quetzalcoatlus and Hatzegopteryx. 

Pterosaurs have been shown to increase in size over the Cretaceous, with the largest pterosaurs ending up at the end of the Cretaceous in the azhdarchids. In the mid-Jurassic, birds started to appear, giving the pterosaurs competition in the skies. Some studies have suggested that both groups were able to survive by occupying different niches [1], others have shown that pterosaur diversity did not decrease until the Late Cretaceous so this was unlikely to be caused by birds [2], while recently it has been suggested that birds outcompeted small pterosaurs, driving them to the gigantic sizes seen in Late Cretaceous azhdarchids [3]. Of course, this is not agreed upon, and other studies suggest it's a preservational bias that is keeping the small Late Cretaceous pterosaurs from being preserved, not that they didn't exist at all [4].

There is some evidence of smaller pterosaurs from the Late Cretaceous including those of Montanazhdarcho and Eurazhdarcho, but also some smaller fragments around that point to some very small pterosaurs. Another small pterosaur is one called Piksi, known from small fragments from the Two Medicine Formation. First described as a bird, only a few small wing fragments have been found including the distal humerus, and the proximal radius and ulna [5]. It had an estimated wingspan of just 1 m, and is thought not to be an azhdarchid, but an ornithocheiroid, a group not really present in the Late Cretaceous. This is the first example of a possible small pterosaur in the Late Cretaceous, but there are also potential examples of small pterosaurs from other parts of the world, but no clear examples yet.

While small pterosaurs are obviously not common in the Late Cretaceous, there do seem to be some examples which suggest there is something else going on than just them being outcompeted by birds. Another interesting fact is that there are no confirmed records of azhdarchid juveniles from this time either. Obviously for there to be giant pterosaurs, they have to be juvenile at some point. While there are reports of other pterosaur juveniles at different time periods around the world (e.g. "Nemicolopterus", Pterodactylus, Hamipterus) and even embryos (like Pterodaustro), we would expect to find juvenile azhdarchids, yet these haven't been found. Often in the fossil record we find that that are biases in what is preserved and what isn't, and these biases change between environments, throughout time, and in different localities. One such bias is known from Dinosaur Provincial Park in Alberta, where azhdarchid pterosaurs are known from. Very few small dinosaurs or animals in general are found in this area, and this is especially seen in juveniles. Juveniles are extremely rare. If this is known from other areas and taxa, why not for pterosaurs?
"Nemicolopterus" which may be a juvenile Sinopterus, a tapejarid from the Lower Cretaceous of China. Image copyright John Conway. 


The fact that no juvenile Late Cretaceous pterosaurs have been found makes me extremely reluctant to agree that no small pterosaurs existed during this time. There must be some kind of preservational bias keeping small pterosaurs and juveniles from being preserved. As we find more localities and more fossils, more evidence is suggesting that there were more than just giant pterosaurs around in the Late Cretaceous, we just need to find them!

Next week I'm off to Romania on the hunt for these tiny pterosaurs (and the big ones too)... Wish me luck!

References
1. McGowan, A. J., and Dyke, G. J. 2007. A morphospace-based test for competitive exclusion among flying vertebrates: did bats, birds and pterosaurs get in each other's space? Journal of Evolutionary Biology 20: 1230-1236.
2. Butler, R. J. et al. 2009. Estimating the effects of the rock record on pterosaur diversity patterns: implications for hypotheses of bird/pterosaur competitive replacement. Paleobiology 35: 432-446.
3. Benson R. B. J. et al. 2014. Competition and constraint drove Cope's Rule in the evolution of giant flying reptiles. Nature Communications 5: 3567. 
4. Vremir, M. et al. 2015.A medium-sized robust-necked azhdarchid pterosaur (Pterodactyloidea: Azhdarchidae) from the Maastrichtian of Pui (Haţeg Basin, Transylvania, Romania). American Museum Novitates 3827: 1-16.
5. Agnolin F. L. and Verrichio D. 2012. Systematic reinterpretation of Piksi barbarulna Varricchio, 2002 from the Two Medicine Formation (Upper Cretaceous) of Western USA (Montana) as a pterosaur rather than a bird. Geodiversitas 34:883-894.

Tuesday, 17 March 2015

Bring azhdarchids down to the ground

Last week, palaeontologist Mike Taylor (of SVPOW) brought up a very good point on twitter:
And many of us whole-heartedly agree. Flying models of azhdarchid pterosaurs are what typically grace museums, if they appear at all. These are impressive, but also often missed. For example, at the AMNH pterosaur exhibit on that ended earlier this year, there was a giant fleshed out azhdarchid model on the ceiling. The problem? It was in a room with lots of things that people were more interested in, and hardly anyone actually looked up and saw it. Even once you do see it, it's hard to really understand how big it is, and that it is really a model of a real, flying animal.
Full-sized flying azhdarchid model at the State Museum of Natural History, Karlsruhe
An azhdarchid pterosaur standing to attention with a giraffe
and human for scale. Image copyright Mark Witton.
However, if you stand an animal on the ground next to something they are used to seeing (or even better, where they can stand next to it), the scale suddenly becomes a lot more clear and it's much easier to be amazed by the size. Take Mark Witton's iconic azhdarchid with giraffe for scale - it allows us to really appreciate how big these animals were. I think everyone would agree that a giraffe is a very tall animal, and the biggest azhdarchids were just as tall. Tell me that isn't impressive! Pterosaurs don't always need to be depicted with their wings outstretched and flying. They were equally as impressive on the ground walking around on all fours. Additionally, depicting a pterosaur on the ground teaches people that pterosaurs were actually quadrupedal animals. They were not walking around on their hind limbs like birds, and like many old depictions show. They walked with their wing finger bent up behind them and their hand down on the ground as shown in the image above. We know this is true thanks to the anatomy combined with a number of trackways attributed to pterosaurs that clearly show 2 different sets of prints: a hind limb set and a forelimb set. Bringing those pterosaurs down to the ground both reiterates how large they were, AND teaches people something about their biology. What could be wrong with that?

I can personally attest to how impressive a standing floor mount of an azhdarchid can be, and what it can do. I've always been interested in palaeontology, but was never sure exactly what I wanted to study. That was until I went to France in 2009 on a family trip during my undergraduate degree. I had heard about a small but interesting natural history museum in Esperaza, and we decided to check it out. Here I saw my first (and only) azhdarchid floor mount, and was instantly amazed. I'm not sure how long I stood there, but  I can tell you that I spent probably 20 minutes looking at this thing from different angles in awe. That was the moment that I decided I wanted to study pterosaurs, and it was that instant that made me ask the question "how did these large animals fly?". And to top it off, that mount isn't even showing the azhdarchid standing to full height. It's sprawling quite a bit, and should be even taller.
The Quetzalcoatlus standing skeletal mount in Esperaza (sorry the picture isn't great!)
While they are frequently depicted in palaeoart down on the ground, they are so rarely shown this way in museums. I wholeheartedly agree with Mike Taylor and Mark Witton about this - bring azhdarchids down to the ground! Let people stand beside them and look up at them. It's the best way to truly show how big the animal is. It's what I owe my current love for pterosaurs to!

- Thanks to Mike Taylor and Mark Witton for the idea, and Ben Miller and Joe Hancock for the blog post encouragement!

Monday, 9 March 2015

AMNH Pterosaur Exhibit

From April 5 to January 4 the American Museum of Natural History in New York (AMNH) had a special exhibit called "Pterosaurs: Flight in the Age of Dinosaurs". I was lucky enough to make it to see the exhibit over the final weekend while I was on a research trip to see the collections.

The exhibit was curated by the AMNH palaeontology curator Dr. Mark Norell, and Brazilian pterosaur expert Dr. Alexander Kellner, with some help from Dr. Mike Habib, a palaeontology and flight expert (and one of my many supervisors). It included fossils from all over the world, and was generally very well done in my opinion, encompassing some controversies in pterosaur palaeontology, old and new ideas, and some of the most recent studies and finds. It was also accompanied with a fantastic gift shop including a very-well illustrated book based on the exhibit.
The front of the book, featuring a Tupandactylus.
Back cover featuring an assortment of pterosaurs.
Dsungaripterus skeleton
It started in the same way as most exhibits with a background of pterosaur research, explanation of what pterosaurs are, and an overview of their diversity. They discussed pterosaur locomotion, including some fossils of footprints and various things. The exhibit was full of life-size skeletal models of pterosaurs that hung over top of you as you went along, which was a really cool addition, including Dsungaripterus shown here.

It was starting at about this point in the exhibit that I started getting really excited. First of all, there were some really well done (and also simple) educational displays explaining features like the wing structure in pterosaurs (vs. birds and bats) and the hollow aspect of the bones. Of course anyone who has read my blog before and seen my posts on pneumaticity in pterosaurs and birds will guess that I like hollow bones. I enjoyed the explanations and diagrams on the hollow bones and the comparison of pterosaur bones to airplane wings with the trabeculae acting as struts (see image below). However, there is some evidence that the trabeculae in the shaft actually didn't do a lot in terms of strengthening the bone and preventing bending or torsion, but still a cool analogy.
The next room of the exhibit focused on the flight capabilities of pterosaurs, and included a number of flight games that allowed people to stand in front of a camera and pretend to be a pterosaurs. It was entertaining to watch the kids flap around and try to be a pterosaur while the pterosaur on-screen mimicked what you did. They included flying, taking off, taking off from water, picking up fish from water, chasing insects, etc. The unfortunate thing about these videos is that they were so distracting to the kids that most of them failed to notice the giant life-size model of Quetzalcoatlus northropi suspended from the ceiling above. It was so big (and the lighting was so poor and I forgot my flash) that I didn't get a picture, but it was impressive. Along with it was a replica of the humerus, just to show how big it really was.
Quetzalcoatlus northropi humerus replica
The rest of the exhibit focused on looking at the different sizes, shapes, and possible functions of the cranial crest, followed by a special focus on the Araripe Basin of Brazil where a large number of exceptional pterosaur fossils (and much more) come from. 

The highlights of the exhibit for me included:
The "Dark-wing" Rhamphorhynchus
1. The "Dark-wing" Rhamphorhynchus - Anyone who works on pterosaurs knows this fossil as one of the best preserved, three-dimensional Rhamphorhynchus fossils from the Solnhofen in Germany. The best part of this fossil, however, is that it also preserves a large amount of soft tissue, and is the fossil that gave us the first true insight into the internal structure of the wing membrane. It is a truly wonderful fossil, and is actually owned by a private fossil collector in Germany, so is rarely seen on display. This was the first time the specimen had been on display outside of Germany, and it was a joy to see. I was hoping to be able to examine it after the exhibit was done, however, that was not possible.
AMNH 22555 - Anhanguera santanae
2. AMNH 22555, one of the best preserved specimens of Anhanguera santanae - This specimen is a beautifully preserved skeleton including the head, neck, much of the pectoral girdle (but unfortunately only bits and pieces of the wing), trunk, pelvic girdle, and some of the legs. It shows very well how weird the body proportions of pterosaurs can be with a massive head, long neck, small trunk, and tiny pelvis. It's especially interesting to me for several reasons: a) it was described by pterosaur legend Peter Wellnhofer; b) It is 3-D and therefore much of the original structure can be determined; and c) I have had the opportunity to view CT scans of it thanks to Pat O'Connor, who previously scanned the specimen. After the exhibit finished, I also was lucky enough to examine it up close in collections for several days. 
Romanian pterosaur bones. Top right is a syncarpal
(wrist bone), and bottom left is a cervical (neck)
vertebra.
3. Romanian pterosaurs - At the very end of the exhibit, where many people walked past thinking it was not interesting, was a small display on the "next big thing" in pterosaur palaeontology, including 2 casts of giant Romanian pterosaur bones. This is interesting to me first of all because my research group in Southampton does field work in Romania where these bones are found and is involved with these studies (and I was lucky enough to have one of those bones placed in front of my by my supervisor early in my PhD), but also because as a pterosaur palaeontologist any giant pterosaur bones are interesting to me. I was also happy to see an image by my friend and great palaeo-artist Mark Witton in the case, showing Romanian pterosaur Hatzegopteryx. There is some great stuff coming out of Romania, and I'm looking forward to heading back at the end of the month. Maybe we'll find more! 

Of course with any exhibit, and with a pterosaur one in particular, there are going to be some things I'm unhappy with. There were 3 I can think of, but they have annoyed me quite a bit. These are:
Goofy looking Nyctosaurus with a fleshy crest.
1. The constant depiction of Nyctosaurus with a fleshy sail-like head crest - In the portion of the exhibit on head crests, there is a replica of the famous crested Nyctosaurus skull. Along with this is a portion of text that read "Most scientists think these bony prongs were connected by soft tissue... Some think they could have remained bare, like deer antlers". I was quite surprised when I read this, and immediately consulted with fellow pterosaur-palaeontologist Dave Hone, and we agreed that we didn't know anyone that still thought there was soft tissue. In fact, there is no evidence to suggest that there was soft tissue on their crest... Every image of Nyctosaurus in the exhibit was reconstructed to have a giant, awkward sail on it's head!
2. Discussion of skim-feeding - This isn't particularly surprising as there are a number of people that support this, but there is also a significant amount of evidence that says they were not able to do this. Dip-feeding, yes. Skim-feeding, no. I haven't looked at it empirically, but I can just think mentally that once a pterosaur opened it's mouth in the water there would be so much drag that it wouldn't be very good for the animal's jaw. I know that Darren Naish and Mark Witton have looked at this a lot, and it seems to make sense that they couldn't feed that way. However, there was no discussion of these problems or other views, not entirely surprisingly.
3. "Dawndraco" cast - This bit has annoyed me for a few reasons. First of all, there is much debate about the validity of this species. Despite this, there was a massive cast and focus on the species, and no mention of the other viewpoints. This leads me to my next problem with it, which you may be familiar with if you read my post on fossil casts. It's a minor problem, but it still annoys me... The original of this specimen is housed at the University of Alberta, my old university. The specimen on display at the AMNH was a cast of the original. Despite other casts in the exhibit correctly stating that they were casts, this specimen said it was the original skeleton. And to frustrate me even more, the specimen number was incorrect! This specimen has a history of being incorrectly referred to in the literature, despite being one of the best pteranodontid specimens in existence. Give credit to the correct institutions, label specimens correctly, and don't say it's an original when it isn't... I'm sure it was an honest mistake, but how can so many "honest mistakes" come with one specimen?!

So there's my take on the AMNH pterosaur exhibit. Anyone who wants to know more about it can go to their website where there are videos to watch and some more information. I wish I could have posted this in time to recommend people to go, but unfortunately, I only got to see it on the last day... However, I get to enjoy it again each time I have a shot or make a drink from this awesome shot glass: