Wednesday, 25 November 2015

Survey time! Please take part :)

To my readers...

I've teamed up with Science Borealis, Dr. Paige Jarreau from Louisiana State University and 20 other Canadian science bloggers, to conduct a broad survey of Canadian science blog readers. Together we are trying to find out who reads science blogs in Canada, where they come from, whether Canadian-specific content is important to them and where they go for trustworthy, accurate science news and information. Your feedback will also help me learn more about my own blog readers.

It only take 5 minutes to complete the survey. Begin here:

If you complete the survey you will be entered to win one of eleven prizes! A $50 Chapters Gift Card, a $20 surprise gift card, 3 Science Borealis T-shirts and 6 Surprise Gifts! PLUS everyone who completes the survey will receive a free hi-resolution science photograph from Paige's Photography!  

It's a great chance for me to get feedback on who is reading my blog, and for Dr. Jarreau to get more detailed feedback about Canadian science blogs in general, but of course, you don't need to be Canadian to take part. Please take the time to fill out the survey, and you may even win a prize!

FYI I'm registered with Science Borealis as Liz Martin-Silverstone, so that is probably the name to use when they ask.

Thanks to all in advance!

Thursday, 19 November 2015

To self-fund a PhD or not? That is the question...

I am a (partially) self-funded PhD student. As such, prospective PhD students often ask me if I would recommend going into a PhD without secure funding, which is a bit of a complicated issue. Doing a PhD self-funded has it's ups and downs, and pros and cons, which I'm going to try to summarise here, as it's something I think a lot about.

To start, I'll explain my situation a bit. As many of you know, I'm a PhD student at the University of Southampton in the UK, however, I'm originally from Canada, which complicates things. I have just started my 3rd year of a 3-4 year PhD on pterosaur biomechanics. As I'm not from the UK, yet doing a PhD here in the UK, funding has always been difficult. Before starting at Southampton, I had intended on doing a PhD at the University of Bristol, where I did my MSc. Unfortunately, I was unable to secure any funding, and was looking at the prospect of ending up approximately £80000 in debt at the end, assuming I would be unsuccessful of finding any funding (which, indeed, was an unlikely event). With this daunting prospect, I decided to try for a PhD at the University of Southampton, where my now supervisor was confident I would secure something. After interviewing fairly well, I ended up being given an offer that was suggested to be quite good for an international student: the graduate school would cover half of my tuition, and I would receive a Research Training Support Grant (RTSG) of an unknown amount (at least £1100 per year), and I would be responsible for the rest. No stipend, still responsible for about £9000 a year of tuition, and a lower RTSG than students funded through research councils like NERC. 

Seeming like a much better offer than nothing, I accepted, confident I would eventually manage to find some more funding. At the end of my first year, I successfully was granted an NSERC award from the Canadian science funding agency, a hearty sum of $21000 CAD per year. My supervisor was also able to secure some additional research funding for me in order to cover my CT scans (of course I chose a project that isn't cheap), and I've since managed to get some funding from external sources to cover travel or research trips (thanks to the Palaeontological Association and Geological Society of London, and one of my supervisors - Mike Habib). However, I have applied for far more than that (nearly 20 if I counted correctly, since my MSc, and I'm not telling you how many were successful). In fact I don't know of any other PhD student that has applied to the same number of grants/scholarships/awards as I have, and while I have definitely improved over time, it's still just as depressing when you get that "sorry, you weren't selected" letter. The reality is that as an international student, even if the university covers half of my tuition, I'm still responsible for £9000 a year in fees, which is barely covered by my Canadian scholarship, and I have nothing to cover my living expenses. In fact, if it wasn't for my husband's PhD funding (and now job) and some help from both of our fathers (thanks Dad and dad-in-law!), we never would have been able to make it work. 

This sounds pretty unpleasant and unappealing, so what are the pros of doing it on your own? There aren't a lot of advantages, but I would argue that there are some major ones. First of all, you don't have the same kind of pressure to finish. In the UK, PhD's are funded for 3 years, with the possibility of extending it to 3.5, but rarely 4. As I've started my 3rd year, this means most of my friends are aiming to finish by the end of this year, or the middle of next year. I, however, don't have that rush. I've been surviving without my living expenses being covered for 2.5 years now, and an extra year isn't going to kill me. I am able to focus on the problem at hand without massively stressing over getting it done by this time next year. The other advantage is that I don't have a funding agency breathing down my neck, directing my research. Because I am self funded, the project is more-or-less up to me. Of course my supervisors give me suggestions and help, but what I do and where I go with it is more up to me than those who have been given funding for specific projects. These two major advantages of left me pretty happy with my PhD project and where I'm going.

However, would I recommend it? Not unless you have something to fall back and catch you if you can't find funding. Don't go into it expecting to find full funding in your first year, especially if you're not from the country you're doing your PhD in. So many funding bodies don't provide funding to people from outside the UK/EU, and they don't give funding for tuition or living expenses. It's pretty easy to find funding to cover conferences or research expenses, but a lot harder to help out with your dinner and to put a roof about your head. 

There are also a lot of problems that pop up and that you wouldn't expect, and I can think of 2 examples of things that have happened to me. First of all, it makes the possibility of extensions a bit terrifying. If something happens to you and you need to suspend your PhD, you can get an extension to go beyond the normal 4 year limit. It may seem like a good offer, but it's a bit of a trojan horse - if you don't have funding, and are barely living day-to-day, that extra few months may kill you financially, and there is no funding agency to ask for help, even if it would help your project. Another problem I've had is funding for Open Access. I am a big proponent of Open Access publications. However, did you know that in the UK universities will only cover the fees if you are funded by a UK research council? I didn't... I've been able to get fee waivers for both of my papers published with PLOS ONE, but it wasn't easy. And I don't have the money to throw around for a PeerJ subscription either. It makes it just that little bit harder to do than for people who can just ask their uni to pay.

So, my advice? Don't start a self-funded PhD unless you know that you can finance it yourself if need-be. Everyone assumes they'll find funding later on, but it's really hard to get once you start. You might get lucky and get some, or you might not, so be aware of that before you start. And to supervisors and academics: for the love of all of us self-funded students, don't promise money that you don't have! I've heard countless stories of people starting with the promise of funding from supervisors that just doesn't appear. If you want a student that badly, find money for them without lying or promising something you don't have, even if you're doing it out of the goodness of your heart and are positive you will find money. Sometimes, you don't, so don't say it until it's in your hands! It's much harder to realise a year into a PhD that you can't afford it when no funding appears than to just hold off in the first place and wait for secure funding. And finally, if you're going to do it, make sure it is something that you truly want to work on and that you are happy with. Don't pay to do a PhD that you will end up hating. It is absolutely not worth it.

After posting this, I realised that I should really add this: I am fortunate because I am not fully self funded, but I know a number of people that are, with varying degrees of support. While I have some tuition covered, I still pay more than anyone else I know for a PhD (with the exception of one other self-funded person I know). Other people have fees waived, but less RTSG, and some still pay fees, or have no RTSG, or both, but none with a stipend. There are varying branches to the self-funded tree. and I can only truly comment on the one I am on: I have a fairly large amount of funding, but not nearly enough to cover my fees or living costs.

Any other self-funded PhD's out there who have comments, please leave them! I'd love to hear other people's opinions.

Monday, 2 November 2015

Skeletal mass in birds

I've spent a lot of time on this blog rambling about estimating mass in extinct animals, including talking about the "lightweight" skeleton in birds, pterosaur bone mass, and the likelihood of giant pterosaurs weighing as low as 70 kg. Now I'm going to talk a bit more about this problem, specifically looking at the relationship between skeletal mass and total body mass in birds, the topic of my most recent paper.

In 1979, a paper came out looking at the relationship between skeletal mass and total body mass in birds, which was remarkably similar to that same relationship in mammals [1]. Since the two groups had such a similar relationship, the same was to estimate the total body mass in pterosaurs, after estimating the skeletal mass using simple geometric methods [2]. Because mammals and birds are so different and far apart in the evolutionary tree, it was thought that a similar relationship between the two meant that other animals like pterosaurs would share a similar relationship. Of course, I'm interested in pterosaur mass, so these methods are interesting to me.

During my MSc, my supervisor Colin Palmer and I looked at the original 1979 study a bit closer and found some slight problems with it. First of all, while they sampled a large number of bird taxa, each species average skeletal and body mass was determined from just 1-6 individuals, with most of them being just a single individual. How can they know this is a normal average weight? Additionally, the original data were presented in a log-log scale, showing a nice tight relationship with little variability. However, when the data were plotted on a linear scale, significant variability could be seen. This made us more interested in the topic.

When I started my PhD, my supervisor Gareth Dyke told me about a big dataset that his friend Gary Kaiser had meticulously collected on over 700 bird specimens from the Royal British Columbia Museum, which included total body mass and skeletal mass for over 400 individuals from 79 species. This dataset has more individuals than the original, but fewer species, meaning we had 1-30 individuals for each species, giving us a much better picture of average mass and variation within a species. With some help from an undergraduate student Ria McCann, and a lot of stats help from Orsi Vincze, we started to look at this dataset and saw some pretty interesting patterns, which we recently published in PLOS ONE [3]. First of all, our new dataset turned out to result in a pretty similar relationship to the original study, which was good news. We also found that there was even more variability within our dataset than the original study, which isn't surprising with a large number of individuals per species. For example within a single species, the rhinoceros auklet, total body mass varied from 0.4-0.6 kg (approximately 33%), while skeletal mass were varied by almost a factor of two. At a total body mass of about 470-490 g, the measured skeletons weighed in from 26 g to 34 g. This is a large range for a single species. Total body mass ranged from just 256 g, up to 616 g.
Variation in body mass and skeletal mass in the rhinoceros auklet.
Of course, that range could be due to age, and we thought it may be possible that age would affect these relationships. Unfortunately, it can be difficult to determine age of a bird if it is found dead (as most of these specimens were), so the only age classes we could determine was whether the bird was within it's hatchling year, or above that. However, we found no statistical difference between the two groups, suggesting that this feature does not change ontogenetically, which was a bit surprising. We also looked at males vs. females, as it was suggested that this could change things. We know that female birds regulate the amount of calcium in their bones depending on what cycle of egg-laying they are in, as they use the calcium from their eggs to make the hard shells. Again, however, we found no statistical differences between the two groups.
Sexual variation between male (blue) and female (red) birds
One thing I was most looking forward to testing was if there were any differences between different flight modes. Birds that fly in different ways having different body set ups with slightly different morphological adaptations, like longer, more slender wings for birds that soar. But are their skeletons built differently? For example, do birds that spend more time on ground, so-called 'burst-adapted' birds like pheasants and ptarmigans, have more robust skeletons that are maybe less 'light-weight' than traditional bird skeletons? Well at least between the 3 main flight modes we tested (soaring, continuous-flapping, and flap-gliding), they are not different. Unfortunately, we didn't have a large enough sample size of burst-adapted flyers to see if they were statistically different. I'd like to look at this more as my hunch is they will be different. I'd also be interested in seeing how passerines would be different, as passerines use a type of flying that is referred to as intermittent-bounding, where they kind of hop through the air with intermittent periods of flapping and not. Our new data set didn't have any passerines in it, which is fairly uncommon since they make up a large number of modern bird species.
Different flight modes - blue = soaring, red = flap-gliding, green = continuous flapping.
But why is this important? Well going back to the original question about mass estimation, we found that these results were correlated with phylogeny. This means that for a group of modern birds, like Neornithes, this relationship holds true. However, as you move further from this group, the relationship is going to be less and less supported. So moving into groups with no modern representatives like enantiornithine birds, which are significantly different from modern birds, or non-avian theropod dinosaurs, this relationship is going to be less accurate. Finally, moving all the way to pterosaurs, which are the sister group to dinosaurs, this relationship may not yield an accurate result, which is something that we hinted to in my first paper on pterosaur bone mass estimation [4].

I think that using the more traditional methods of volumetric mass estimation is likely to be more accurate for pterosaurs, for this reason, rather than using skeletal correlates as is becoming more common. Unfortunately, that requires more complete skeletons and a lot more work. Pterosaurs have no modern analogues or close relatives, suggesting that skeletal correlates are not going to work. Jon Tennant wrote a great post on this paper as well over at PLOS Paleo if you want to take a look!

Another thing I'd like to point it is the dataset we used. Gary Kaiser and Carl Jonsson collected a large amount of data on these specimens, including measurements of various skeletal elements, most of which we didn't use in this study. We know that a lot more information can be used from this dataset and many more interesting studies can use it, and we have posted the data up on the PLOS One website as supplementary material. We hope that someone can use the data for more in-depth studies like this! Please share if you know someone who could use it!

1. Prange HD et al. 1979. Scaling of skeletal mass to body mass in birds and mammals. American Naturalist 113: 103-122.
2. Witton MP. 2008. A new approach to determining pterosaur body mass an its implications for pterosaur flight. ZittelianaB 28: 143-158.
3. Martin-Silverstone E, Vincze O, McCann R, Jonsson CHW, Palmer C, Kaiser G, Dyke G. 2015. Exploring the relationship between skeletal mass and total body mass in birds. PLOS ONE 10: e0141794.
4. Martin EG and Palmer C. 2014. A novel method of estimating pterosaur skeletal mass using computed tomography scans. Journal of Vertebrate Paleontology 34: 1466-1469.

Friday, 16 October 2015

Exceptionally preserved Early Cretaceous mammal

There's an ongoing theme/belief in vertebrate palaeontology that if you want to work on Mesozoic mammals, you have to like teeth. This stems from the fact that a large number of early mammal or mammaliaform fossils are actually teeth, and the different species, genera, or even families are primarily distinguished from each other due to the features of their different teeth, and in particular their molars. This can be related to their exact dental formula (i.e. how many incisors, canines, premolars and molars they have), the number of cusps found on specific teeth, etc. In fact, many names of species or families come from the teeth: Morganucodon, one of the best known early mammals means "Glamorgan tooth", from the Vale of Glamorgan in Wales where it was first found, identified first by a tooth; and eutriconodonts have three ("tri") cones or cusps ("con") on their teeth, while many more end with "dont" or "don" or "dens", all different ways to say teeth.

This is not to say that these animals are known only from teeth. Morganucodon for example is known from many bones. Unfortunately, in the area of Wales where they are commonly found, the skeletons are all broken up and the bones are often broken, and always separated from each other (disarticulated), making it difficult to do more studies with them. However, once in a while, a very well preserved Mesozoic mammal pops up, which is where Spinolestes xenarthrosus comes in. Described this week in Nature by Thomas Martin and colleagues, this new mammal is very interesting.
Fossil of Spinolestes xenarthrosus from Martin et al. (2015).
Spinolestes xenarthrosus is a newly described eutriconodont mammal from the Early Cretaceous of Spain. The skeleton reveals a variety of functional features, suggesting Spinolestes was a proficient mover on land, and may have dug into the ground when necessary, but not necessarily adapted for this kind of lifestyle as it lacks the dental and skeletal characters typically associated with animals that habitually live underground. It had vertebrae similar to those found in xenarthrans (anteaters, armadillos and sloths), a condition that it evolved convergently (meaning the existence of this feature in both groups is not due to shared ancestry, but rather it evolved twice). While these are all interesting features, what is the most remarkable about this specimen is the soft tissue and integumentary structure preserved.

Spinolestes, amazingly, has a number of organs preserved including the outer ear, and possible lung, and liver tissue. The authors have even identified the presence of a muscular diaphragm. Spinolestes is characterized by having a mane containing long “guard hairs” along the neck and shoulder region, and longer hairs along the middle of the back and tail, making a hairy crest along the midline of the animal, while the rest of the body is covered in more typical shorter, soft underfur. In addition to these hairs, it also had “protospines” along the back of the hip-region, which are larger than hairs and formed by several smaller hair-like filaments merging together, similar to how spines are formed in modern mammals like hedgehogs. These features in combination show that mammals evolved this covering of a softer undercoat, denser and thicker guard hairs, and stiffer spines already in the Early Cretaceous, relatively early on in mammal evolution, a feature that is still seen in mammals today.
Lifelike reconstruction of Spinolestes xenarthrosus by Oscar Sanisidro
Martin T, Marugán-Lobón J, Vullo R, Martín-Abad H, Luo Z, Buscalioni AD. 2015. A Cretaceous eutriconodont and integument evolution in early mammals. Nature 526: 380-384. 

Tuesday, 13 October 2015

In Honour of Ada Lovelace - Female Palaeontologists

Today is Ada Lovelace Day. Many of you (like me initially) may not know who Ada Lovelace was, or what the day symbolises. Ada Lovelace was a British mathematician, who is widely regarded as being the first computer programmer. In 1842, she translated and expanded on an Italian article on the "Analytical Engine", a machine invented by her friend, the inventor Charles Babbage. This article contained such thorough and advanced notes and are attributed with including the first algorithm to be carried out by a machine, and were inspiration for Alan Turing's work on the first modern computers in the 1940s.

Living in the 1800s, this was a massive feat for women in science. Ada Lovelace Day aims to celebrate and recognise the achievements made by women in STEM fields - that is science, technology, engineering, and math. Some obvious examples come to mind of scientific achievements by women throughout history, including (but not limited to): Marie Skłodowska Curie (commonly known as Marie Curie), who was the first female Nobel prize winner known for her research in radioactivity; Rosalind Franklin, whose discoveries in chemistry and x-ray crystallography were integral in the understanding of the structure of DNA; Jane Goodall, who has done wonders in our understanding of modern primate behaviour, and ecology; and of course Mary Anning, whose fondness for fossils on the beaches of Lyme Regis lead to a number of scientific discoveries and the recognition of the Jurassic Coast World Heritage Site.

Aside from Mary Anning, there are a large number of female palaeontologists who have made exciting discoveries, and are continuing to do pioneering research. This is by no means a complete list, but here are a few female palaeontologists that have inspired me, and have made significant contributions to the field:

Kay Behrensmeyer (AKA Anna K. Behrensmeyer)

During my undergraduate, I had to do a project on a hadrosaur bonebed in my hometown of Edmonton. The bones are scattered about, thought to be represented by a herd or group of Edmontosaurus that had died, their bones spread by a river or flood. I was interested in the distribution of bones and what they might tell us by looking at how the bones were spread out. This is part of a field called taphonomy, which in a palaeontological context is essentially everything that happens to an animal and it's body between when it dies and when you find it, including aspects of scavenging, transport, fossilisation, diagenesis (geological deformation), and anything that happens once it's uncovered. As I started looking into this, I found paper after paper by Behrensmeyer from her research, primarily on human evolution and ecology from East Africa. Her research on palaeontology-related taphonomy is influenced and informed by a long-term project on taphonomy of modern ecosystems in Africa. She has gone on to write books and book chapters on taphonomy, with many of her characterisations and observations becoming the pillar of modern taphonomic research. Today, she continues to look into taphonomy of palaeo-ecosystems and reconstructing and comparing ecosystems through time. Her work has been absolutely vital in understanding many aspects of past ecosystems and paleo-ecology. She is currently the Curator of Vertebrate Paleonotology and Taphonomy in the Smithsonian National Museum. 

Emily Rayfield

Emily Rayfield is currently one of my supervisors in my PhD, and is a Professor at the University of Bristol. Her research focuses on biomechanics and how you can use it to determine function, often using modern animals to inform on fossils. She is well-known for kick-starting the use of Finite Element Analysis (FEA) in order to understand fossil skulls, such as looking at stress and strain, and further deduce feeding strategies. Much of her work focuses on computed tomography (CT) scans to look at the structure of bone, and how this can inform us on locomotion and function of extinct animals. Rayfield also works on how function and ecological diversity change through time, and has worked on a large number of vertebrate groups including non-avian and avian dinosaurs, mammals, fish, crocodylians, and much more.

Mary Leakey

Matriarch of the famous Leakey family, Mary Leakey was integral to our understanding of primate evolution from the family's research in the Olduvai Gorge of East Africa. She discovered the first skull of Proconsul, an extinct ape thought to be on the branch of primates leading to hominids, as well as Zinjanthropus, a robust australopithecine hominin (much closer to Homo than Proconsul). Leakey was also responsible for finding and classifying a number of stone tools found at various hominin sites, and the Laetoli footprints, a very famous trackway showing three individuals walking (2 side-by-side, one walking in the footsteps of another) of hominin with a human-like gait from 3.7 million years ago. These tracks showed without a doubt that hominins had evolved bipedality (walking on 2 feet rather than 4) by this time, a significant find. Mary Leakey's work stretched both the fields of palaeontology and anthropology, more widely regarded as a palaeoanthropologist, and was essential in our understanding of primate and hominid evolution.

Jenny Clack

The evolution of tetrapods (vertebrates living on land, having 4 limbs rather than fins) has long been a hot-topic of study in palaeontology. We know that life started in the water, and the first vertebrates were fish, but how did they get onto land? Jenny Clack has devoted her career to understanding this transition, looking at early tetrapods during the Devonian and Carboniferous, and has been integral in understanding this important period of the Earth's history.   Some examples of her work include discovering more material and recognising the importance of Acanthostega, a primitive tetrapod with transitional features including both fish and tetrapod features, and the slightly younger Ichthyostega, another primitive, transitional tetrapod, both of which are from Greenland. Clack has also spent a lot of time in search of fossils from "Romer's Gap", a so-called gap in the tetrapod fossil record during the Late Devonian and Early Carboniferous, an important time in tetrapod evolution. Her work has helped to fill this gap and has populated the "gap" with many more fossils. Jenny Clack's research has vastly improved our understanding and knowledge of early tetrapod evolution, and how fish first came out of the ocean and onto land.

Of course, I don't have time to talk about all of the great female palaeontologists out there, but I wanted to feature those four as particularly inspiring or important in my mind. Below is a list of other female palaeontologists that I know (not including students, or the list will never end), and by all means is not a comprehensive list, but are some that I thought of and wanted to feature. I'm open to suggestions to add to the list, but I can't feature all of them! There are too many, which I think means we're doing a great job!

  • Victoria Arbour 
  • Charlotte Brassey
  • Jen Bright 
  • Marie-Céline Buchy
  • Anusuya Chinsamy-Turan
  • Kristi Curry-Rogers
  • Allison Daley
  • Susan Evans
  • Catherine Forster
  • Pam Gill
  • Ursula Göhlich
  • Anjali Goswami
  • Rebecca Hunt-Foster
  • Christine Janis
  • Diane Kermack
  • Zofia Kielan-Jaworowska
  • Eva Koppelhus
  • Susannah Maidment
  • Erin Maxwell
  • Maria McNamara
  • Henneke Meijer
  • Angela Milner
  • Elizabeth Nicholls
  • Halszka Osmolska 
  • Stephanie Pierce
  • Laura Porro
  • Edina Prondvai
  • Taissa Rodrigues
  • Laura Säilä
  • Bettina Schirrmeister
  • Daniela Schwarz-Wings
  • Mary Schweitzer
  • Jessica Theodor
  • Pat Vickers-Rich
  • Lindsay Zanno 
  • Darla Zelenitsky
And of course to my 2 awesome VP group-mates in Southampton, Aubrey Roberts and Jessica Lawrence Wujek! Also if people are interested in more, check out Trowel Blazers which is devoted to women in palaeontology, archaeology and geology!

Monday, 21 September 2015

Meet Mosaiceratops - the Mosaic ceratopsian

Although most of my posts are on pterosaurs, I did get my palaeontological start working on a ceratopsian dinosaur called Centrosaurus as an undergrad in Alberta. While I don't actively work on them anymore (other than trying to finish the manuscript!), they do still hold a special place in my heart, which is why I was very interested in a new species of ceratopsian named today. 

The evolution of ceratopsians (horned dinosaurs best known as animals like Triceratops and Centrosaurus) is not entirely understood. They are generally though of as being closely related to pachycephalosaurs (the dome-headed dinosaurs like Pachycephalosaurus), and are normally remembered for their large horns and bone frills, often well ornamented. The first ceratopsians com from the Upper Jurassic of China, while neoceratopsians first appear in the Lower Cretaceous, with most more derived species being found in the Upper Cretaceous. Although best known for the horns and frills, ceratopsians didn't always have crazy ornamentation. Basal ceratopsians and early neoceratopsians didn't have any horns and had only very little frills. A new species of basal neoceratopsian, Mosaiceratops azumai has been named from the Upper Cretaceous of China, by Zheng et al. (2015). 

Mosaiceratops is significant because of it's mosaic of features reflected in the name, meaning "mosaic horned-face", the mosaic made of a number of characters previously found only in some other groups. A single partial skeleton is known, including part of the skull and a large portion of the post-cranial skeleton. 
Mosaiceratops fossil (a), drawing (b), and skeletal reconstruction (c) from Zheng et al. 2015
The interesting part about Mosaiceratops is the mosaic of features. While it is still considered to be a basal neoceratopsian, it is found quite late, as most basal ceratopsians are found during the Lower Cretaceous. Despite this, it has several plesiomorphic ("ancestral") characters that are not found in other basal neoceratopsians. It also contains features that were previously only found in psittacosaurids, among the basal ceratopsians and basal neoceratopsians. Mosaiceratops is not a psittacosaurid, meaning these features are not diagnostic to that group. One of these features includes the lack of teeth on the premaxilla. This is something seen in more derived neoceratopsians, and psittacosaurids, but not in the rest of the basal neoceratopsians, suggesting that in ceratopsian evolution, there had to be reversals somewhere. Zheng et al. (2015) suggest that lack of premaxillary teeth is a diagnostic feature of the Psittacosauridae and Neoceratopsia, and the animals neoceratopsians that have premaxillary teeth actually underwent a reversal to the primitive condition found in basal ceratopsians. If this is the case, this is one of the few times there has been a major reversal like this in dinosaur evolution, although the authors recognise their analyses are not as well supported as they could be. Additionally, Mosaiceratops has features that are in-between psittacosaurids and more derived neoceratopsians, which places it in this position in a phylogenetic analysis. 
Phylogenetic position of Mosaiceratops from Zheng et al. 2015
Mosaiceratops is extremely important in helping us understand early ceratopsian evolution. We are slowly starting to fill the holes and figure out how this clade evolved. This is yet another case that shows that evolution does not happen in any specific order. Animals can have a mosaic of features that are shared with those more primitive AND those more derived than them, and there is no clear direction of traits or evolution. 

If you want to learn more about ceratopsians, and another fairly recently named basal neoceratopsian, Aquilops, check out this Palaeocast episode with Andy Farke. 


Wednesday, 9 September 2015

Pterosaur with 2 eggs?

Understanding reproduction in extinct animals can be extremely difficult as we lack the necessary information of soft tissues. However, there are certain things we can learn from fossils, and particularly well preserved fossils are even better.

3D preserved Hamipterus eggs with soft impressions
showing a soft pliable egg (Wang et al. [4]).
For example, we know that pterosaurs were egg-layers like other reptiles. In a phylogenetic context, pterosaurs are located in between crocodiles and birds in terms of modern animals, which both lay eggs, meaning it was most likely pterosaurs would have too. Thanks to fossils, we know that they did. While pterosaur egg fossils are rare, they do exist. The first pterosaur eggs were found in China[1-2], and Argentina[3] and come from Early Cretaceous pterodactyloids. The eggs have embryos preserved, and the material from Argentina can even be identified as Pterodaustro. Further pterosaur eggs have been found, and we know that pterosaur eggs were softer (much like those found in snakes) rather than hard calcareous shells like those seen in birds, thanks to one of the first finds that suggested pterosaur shells were leathery[2], and some 3D preserved eggs with impressions in them, from the Hamipterus bonebed in China[4].

Kunpengopterus counterslab and drawing showing 2 eggs
in black from Wang et al. [5]
This is a recent study that I saw presented at Flugsaurier 2 weeks ago, where Alex Kellner mentioned it in his talk on pterosaur reproduction. A pterosaur described a few years ago has been recently restudied, and is potentially teaching us a bit more about pterosaur reproduction in a paper published in July. Wang et al. [5] discovered some interesting features in the counterslab of the pterosaur Kunpengopterus. The counterslab is not fantastically preserved, in fact the images make it hard to see things, but what they have pointed out are not one but two eggs present with the individual. One egg is visible just below the pelvis, as if it had been expelled shortly before or after death, while the other is still visible within the body cavity. In close up images, you can see two rounded egg-shaped structures in these areas. The first egg, the one below the pelvis, was identified initially when this specimen was first described. The second one, however, is new. For the first time, it seems that pterosaurs could have 2 eggs in their body at once.
Outline of eggs from A) the pelvic region, and B) inside the body cavity from Wang et al. [5].
So what does that mean? Who cares if they have 2 eggs? Wang et al. [5] further go into the significance of this find. They suggest that this pterosaur was actually a pregnant female, pregnant with 2 eggs when it died. Having 2 eggs at once is a sign of having 2 functioning oviducts, which is interesting because while most extant reptiles have 2, birds have only 1 functioning oviduct. In birds, this has been thought of as relating to decreasing mass for the evolution of flight, especially as non-avian dinosaurs appear to have 2 functioning oviducts as well. The thought was that having only 1 functioning oviduct was essential to decrease mass in order to achieve flight. However, that seems not to be the case if pterosaurs were able to have 2 oviducts, while being the largest animals ever to achieve powered flight.

This new study provides a lot of interesting information about pterosaur reproduction that we previously didn't know, and of course for me, it's interesting when it comes to the evolution of flight. I'm always interested when people suggest that flight couldn't have evolved without things like the reduction of an oviduct. I think this study shows that mass reduction to achieve flight is not as straight forward or "black and white" as we may have previously thought. Different taxa do different things, and what may be valid in birds, is not valid in pterosaurs, and vice versa.

1. Wang and Zhou. 2004. Pterosaur embryo from the Early Cretaceous. Nature 429: 621. 
2. Ji et al. 2004. Pterosaur egg with a leathery shell. Nature 432: 572. 
3. Chiappe et al. 2004. Argentinean unhatched pterosaur fossil. Nature 432: 571-572.
4. Want et al. 2014. Sexually dimorphic tridimensional preserved pterosaurs and their eggs from China. Current Biology 24: 1323-1330.
5. Wang et al. 2015. Eggshell and histology provide insight on the life history of a pterosaur with two functional ovaries. Annals of the Brazilian Academy of Sciences.