Cartorhynchus: helping ichthyosaurs crawl back into the mainstream.

Over the last 12 months or so, I’ve been researching ichthyosaurs for my masters project, and since then, I’ve been working on publishing my results. As such, I’ve learnt a fair bit of ichthyosaur palaeobiology and systematics. I’m no expert, but at this early stage in my academic career, I can say that at the moment, ichthyosaurs (specifically ichthyosaur endocranial anatomy) are my ‘specialisation(s)’, perhaps even making me an ichthyo-sir (heh). To this end, Motani et al.’s recent publication in Nature was massive news for ichthyosaur palaeobiologists. And that’s why it’s got its own little blog post.

What’s all the fuss about then? This year (2014) marked the anniversary of the 200 years since the first appearance of ichthyosaurs in scientific literature, and ichthyosaurs are closely associated with palaeontological celebrities, both historical (Mary Anning) and rather more recent (Alfred Romer). In those 200 years, we’ve learnt a lot about ichthyosaurs, and whilst they’re not ‘some kind of fish-lizard’, they are diapsid reptiles that were some of the first tetrapods to evolve a thunniform (fish/tuna-like) bodyplan, which aided them in their marine adventures. We know what colour some of them were thanks to melanosomes (Lindgren et al. 2014), we also know that they gave birth to live young, like mammals and some sharks do. We have exceptional fossils of ichthyosaurs actually giving birth, and others with amazing detailed and undisturbed soft tissue outlines. However despite all these amazing discoveries, we still don’t know a whole lot about two major aspects of ichthyosaur palaeobiology: their precise biomechanical function (we can’t create fancy 3D digital models due to the lack of 3D specimens, most ichthyosaur remains are mostly pancake-flat, even the really awesome ones) and perhaps more importantly, how they place in wider diapsid phylogeny.

The miracle of ichthyosaur birth, over 200 million years-ago. Very cool.

The miracle of ichthyosaur birth, over 200 million years-ago. Very cool.

Now before I go any further, it might be a good idea to explain what I mean by diapsid. Diapsida is a group of organisms (more specifically tetrapods) that have two temporal fenestrae (holes) in each side of their heads. Now this is a pretty large group, including archosaurs (dinosaurs, birds and crocs), lizards, snakes and tuataras. So whilst we have some vague idea where ichthyosaurs lie within this pretty large evolutionary tree, we’re not entirely sure. Why? Well because we don’t have transitionary fossils, ichthyosaurs previously (before Motani et al. 2014) appeared in the fossil record as highly adapted marine reptiles, well suited to the marine environment (remember, they look like fishes). So without any hint of which precise group of terrestrial organisms they evolved from, the topic of where ichthyosaurs came from is highly debated. So much in fact that in 2006, a very prominent ichthyosaur worker, Michael Maisch declared that the placement of ichthyosaurs within Diapsida was “…impossible…” (Maisch et al. 2006) without more basal specimens.

The internal phylogeny of ichthyosaurs isn’t a much better state either, with tree topologies changing at every opportunity of the last 10 years or so, threatening to change again when new systematic methods are applied. This again is largely due to the lack of well preserved three-dimensional specimens. But it’s not all doom and gloom, amazingly preserved specimens like those used in Lindgren et al. 2014 have shown us the colour of these ancient fish-dolphins (joke name, please don’t take it seriously), and Fischer et al. 2013’s discovery of Malawania has helped, to some degree, solve the internal phylogeny of at least neoichthyosaurs and ophthalmosaurs (ichthyosaurs from the Jurassic onwards). And obviously, my work on ichthyosaur endocranial and neuroanatomy from an exceptionally three-dimensionally preserved specimen will be hopefully  well received (more on that in the coming months). So it’s not all doom and gloom. But still, ichthyosaurs aren’t exactly the Brangelina of the palaeontological scene, no sir, those celebrity couples occupying all the headlines are dinosaur discoveries such as Deinocheirus and Dreadnoughtus, and the number of ichthyosaur workers isn’t exactly huge.

To my shocked delight, on the afternoon of the 5th of November, 2014 I stumbled upon a fresh new ichthyosauriform, in a Nature paper. Good heavens! Could it be true? Well, of course, other wise I’d have spent the last hour typing madly about ichthyosaurs for no apparent reason. Catorhynchus lenticarpus (‘shortened snout’, ‘flexible wrist’) is a weird, small beast. At first glance, you’d be forgiven for thinking that Catorhynchus wasn’t even a ichthyosaur at all. Well, technically, it isn’t an ichthyosaur at all, it’s an ichthyosauriform.  Catorhynchus comes from the Lower Triassic, approximately 248 million years-ago, and whilst some would call it an ‘ichthyosaur’, the Ichthyosauria (essentially all of the things your properly allowed to call ‘ichthyosaurs’) didn’t occur until later on in the Triassic. So, what the hell is Catorhynchus? Simple, it’s an ichthyosauriform, an ichthyosaur-looking creature which is more closely related to Ichthyosaurus communis than to a hupesuchian? Wait, what the hell are hupehsuchians, and what do they have to do with anything?

Hupehsuchians, think ichthyosaurs but a little more 'vacant' looking.

Hupehsuchians, think ichthyosaurs but a little more ‘vacant’ looking.

Good question. Hupehsuchians are a weird bunch of marine reptiles, who you’d be very much forgiven for calling ichthyosaurs, because well, they look quite a lot like ichthyosaurs. This simple fact has led many researchers to state that ichthyopterygians and hupehsuchians were related, however, there’s been little evidence to really cement this (just because two organisms look the same/have similar features, doesn’t mean they’re closely related. For example birds and bats both have wings, but they evolved powered flight independently and convergent to each other). As I’ve previously said, this is due to the lack of really primitive fossil ‘ichthyosaurs’ as well as our fairly poor understanding of where ichthyosaurs fit relative to other diapsids. However, Catorhynchus has given us a glimmer of hope, enabling us to, for the first time, really start to understand how ichthyosaurs first came about. Now, thanks to Catorhynchus, we think that ichthyosauromorphs (which now includes hupehsuchians) originated in China in the Earliest Triassic, which was a warm tropical archipelago ‘back in the day’. This is interesting, as we know that other groups of marine reptiles, such as sauropterygians (plesiosaurs, pliosaurs et al.) may have also originated in this area at the same time, so Earliest Triassic China may have provided very good conditions to harbour the evolution of many marine reptiles.

Phylogeny of ichthyosauromorphs, modified from Motani et al. 2014.

Phylogeny of ichthyosauromorphs, modified from Motani et al. 2014.

Don’t worry, I’ll stop teasing you now, I’ll actually talk about the fossil for a bit. With a host of unusual features such as really short snout, large flippers and a short body length (the shortest of all ichthyosauromorphs, estimated at a tiny 40 cm) and a really deep lower jaw, Catorhynchus is a weird beast. Yet, despite all these abnormalities, it looks like an ichthyosaur, I mean look at those big eyes! However, it also looks like a juvenile ichthyosaur. For me, and other ichthyosaur workers I’ve spoken to, this is the main reason why people of sceptical about drawing so many big conclusions from Catorhynchus. However, other people (untrustworthy creator of reptileevolution.com) have said that it certainly can’t be an ichthyosaur, and has to be an ‘ichthyosaur-mimic’, because yeah, if it has loads of scientifically diagnostic features of an ichthyosaur the most obvious answer is that it wants you to think it’s an ichthyosaur, just to troll the scientific community, and then years later scream ‘psyche!’ to everyone, you know, because fossils love to mess with us, the jerks.

Catorhynchus fossil from Motani et al. 2014. E represents a  newborn Chaohusaurus, for comparison.

Catorhynchus fossil from Motani et al. 2014. E represents a newborn Chaohusaurus, for comparison.

ANYWAY. I think it’s worth pointing out that it realistically might turn out to be a juvenile, even though Motani et al. do present some evidence that it’s a fully grown adult, for example the forefins of Catorhynchus are almost as long as its skull, a feature found exclusively in adult individuals. However, it’s also worth mentioning that even despite this, Motani et al. don’t completely dismiss the possibility of this specimen being a juvenile. Essentially, I feel it’s best to take this discovery with a pinch of salt until we find a few more specimens of Catorhynchus. Despite this uncertainty, we can be fairly sure that Catorhynchus may have been amphibious. Yeah, that’s right, amphibious and NOT an amphibian. Other articles have said that Catorhynchus is an amphibian, this is incorrect, as Amphibia form their only little group of organisms, which ichthyosauromorphs aren’t part of! However, Catorhynchus is amphibious, i.e. it shares its time between land and water. How do we know this? Well from the fossil, Motani observed that the carpus may have allowed the flipper to bend in a way much like the flippers can bend in seals, and since seals have flippers for limited terrestrial locomotion, it seems likely that this was also the case for the flippers of Catorhynchus. Motani also presents a case for suction feeding in Catorhynchus, which brings the contentious debate of whether other ichthyosaurs fed via suction feeding back to the table.

To summarise Motani and friends have presented the world with a new ichthyosauromorph which, if verified with further specimens, will help us to really start to understand how ichthyosaurs (and perhaps marine reptiles more widely) first evolved, as well as to understand the place of ichthyosauromorphs within Diapsida. And since it was published in Nature, it might turn a few heads, perhaps persuading more people to join the very small field of ichthyosaur of palaeobiology. As always let us know what you think, comment below or Tweet us (or indeed, even Facebook us).

Not only was it amphibious, Catorhynchus was also the most miserable of all the ichthyosauromorphs.

Not only was it amphibious, Catorhynchus was also the most miserable of all the ichthyosauromorphs.

Deinocheirus: why beer-bellies are bad-ass and the importance of being weird

Today started out as a fairly normal day. I overslept thanks to marathonning House late into the night/morning (note: not due to working late/early on my publication, oops), I dragged myself out of bed and into the office. I then, still half-asleep checked Twitter (the morning ritual was well underway) and then suddenly, I displayed both ends of the NedryGrant excitement chart (patent pending) simultaneously. Deinocheirus. It was DeinocheirusDEINO-RUDDY-CHEIRUS! At the moment, I’m in an office full of volcanologists, so no-one understood my excitement (in fact most thought I had some form of disposition, I mean I was practically frothing at the mouth with excitement). I immediately texted Richard and all my other palaeontological friends/colleagues with two words: DEINOCHEIRUS PUBLISHED.

My face on the morning of the 22nd October 2014. (I even laughed like a Dilophosaurus).

Story time

So why was I so stupidly excited? Well, I’m glad you asked. To explain this excitement, our tale begins in 1965. It was July, and the Polish-Mongolian Palaeontological Expedition had stumbled upon a ‘monster’ find. Forelimbs and a shoulder girdle 2.4 metres long belonging to a 70 million-year-old dinosaur with surely the largest forearms of a bipedal animal ever. However, that was all they found. What in the Seven Hells was this magnificent beast? Surely these the arms of some superpredator, akin to Allosaurus or perhaps a mega-Velociraptor? Deinocheirus mirificus was (‘unusual horrible hand’) was ‘born’. For seven-years, this was the most likely explanation. In this time, palaeontologists and members of the public alike went wild with fantastical recontructions of this new and wacky beast, some even going as far as noting that the arms were used much like those of a giant sloth. Alas, in 1972 John Ostrom (the guy responsible for revolutionising the way we think about dinosaurs in relation to birds in the 60s) noted that the bones in the forearm of Deinocheirus appeared similar to those found in the ornithomimosaurs, a group of secondarily-herbiverous theropod dinosaurs very similar to modern ostriches. This agreed with the sentiments of the team that initially discovered Deinocheirus, so it was settled, the beast was in fact an ornithomimosaur. Mystery solved. Right?

Dem Claws.

Dem Claws.

Unfortunately not. Fast forward a little over 40 years later to October 2013, and we still hadn’t found any more remains of the all-too mysterious Deinocheirus. That was all to change. At the SVP 2013 Symposium (one of the biggest annual events in palaeontology) there were hushed, exciting whisperings of new Deinocheirus material (apparently, I couldn’t afford to go). And then, a speaker emerged and confirmed it, Deinocheirus was back, the mystery was apparently solved. New material had been discovered and we now had a 95% complete skeleton to work with. However, this wasn’t fully shown at SVP, and the entire palaeontological community had to wait with baited breath until the work was published. One of the greatest mysteries of 20th and 21st century dinosaur palaeontology had been solved, but we had to wait. It was agonising. Personally, I grew up enthralled with the mystery of Deinocheirus as did many palaeontologists, both young and old, so to be kept in the dark like this was painful.

The Big Reveal

Fast forward again, exactly (pretty much) to a year later. Late October 2014. A dreary-eyed, 20-something-year-old palaeo grad-student is almost hyperventilating over an image he found on Twitter. Ladies and gentlemen, Deinocheirus has landed. And bloody hell if it isn’t the weirdest thing we’ve ever seen.

Deinocheirus-990x980

The Beer-Bellied weirdo in all it’s glory. Deinocheirus mirificus.

Mystery Solved

Standing almost as tall as T. rex, and weighing in at a hefty 6 tonnes Deinocheirus is the biggest ornithomimosaur to dateSo it was big, no biggie right (heh)? Wrong, in addition to it’s monstrous size it’s also (and I might have already said this) bloody weird. With a really deep lower jaw, no teeth, huge forearms, relatively small hindlimbs, a big old “beer belly” (the best description of dinosaur’s anatomy ever, thanks Tom Holtz!) and tall neural spines (similar to those seen in SpinosaurusDeinocheirus sure is different to the ‘typical’ ornithomimosaurian body plan of Galimimus, with long legs and many other features that suggested it was a fast runner. Quite the opposite, Deinocheirus was a big, sluggish brute with a huge appetite. After 50 years, the mystery of Deinocheirus seems to be solved then, it’s a incredibly odd looking, slow moving, bulky, T. rex sized, beer-bellied behemoth. Myth busted, right?

Skeletal reconstruction of Deinocheirus mirificus. Modified from Lee et al. 2014.

Skeletal reconstruction of Deinocheirus mirificus. Modified from Lee et al. 2014.

Again, wrong. These new specimens are that good that we can already begin to hypothesise how Deinocheirus actually lived out it’s seemingly odd, slow lifestyle. Deinocheirus was discovered in the Nemegt Formation, a deposit which is 70 Million years-old (Late Cretaceous), and was an ecosystem similar to that of the Okavango delta today. First off, over 1400 gastroliths were present, probably used to aid in digestion of food, (mainly plants) making up for the lack of teeth. The morphology of it’s jaws and its broad bill (similar to those found in hadrosaurs and ducks) suggest that certain muscles associated with biting were small, meaning that Deinocheirus probably ate soft (and possibly water-dwelling) plants. But there wasn’t just some stones in that big beer belly, no sir! Evidence of a half-eaten fish was found as well, indicating that Deinocheirus was no means a fussy eater, and probably a ‘megaomnivore’ eating pretty much anything it could get it could swallow. This seems to fit well, especially when you consider Deinocheirus’ place in the Nemegt ecosystem, as generalist ‘all you can eat’ type deal (finally, a dinosaur I can relate to) it wouldn’t be in such harsh competition with the other herbiverous dinosaurs in the area that mostly ate plant matter from trees. However, not only do you need to outcompete you friendly neighborhood herbivores to keep on truckin’ in a Cretaceous world, you also need to be not eaten yourself. The main threat in the Nemegt ecosystem was probably the 12 metre long, 5 ton tyrannosaur, Tarbosaurus. However, Deinocheirus seemingly has an answer to everything by sacrificing speed for bulk and size, it was probably too big (and bloody hell, those claws) for Tarbosaurus to safely take on.

Deinocheirus_fin_colcorr_lres

Deinocheirus in situ. Image credit: Andrey Atuchin.

We also know a few more tricks that Deinocheirus had up its exceedingly large sleeves. Remember those Spinosaurus-like neural spines? They were probably there to support the bulky beer belly, similar to an “asymmetrical cable-stayed bridge“. It also had broadended tip-toes (pedal unguals, to be technical), allowing it not to sink when wading into wetter areas. And those claws? No longer used as lethal disembowlers, but for digging/plant gathering. So Deinocheirus seemingly was perfectly adapted to life on the braided, meandering rivers of the Nemegt ecosystem, unafraid of pesky Tarbosaurus, perfectly content to munch away until its heart (and beer belly) was content, and then waddling to the next patch of river to devour (and P.S Deinocheirus didn’t half walk funny).

And the moral of the story is…

By now, you’ve probably found literally hundreds of grammatical and spelling errors, due to the fact that I’ve been excitedly vomiting words onto my laptop in wave after wave of dino-induced mania. Yes it’s weird, and yes I love it because it’s pretty much me in dinosaur form, but why is this important? You’ll probably see this on IFLS (I F***ing Love Science) in a summary post, with ‘weird fat dinosaur discovered’ alongside ‘cure for cancer found’ and ‘artificial intelligence finally sorted’, making palaeontology, yet again look like the stupid and childish sibling of all the other sciences (e.g. “dino with big nose discovered”, unfortunately not a joke). But this is more than just some crazy guys with beards and stetsons finding a random pile of bones and shouting eureka until Nature finally publishes their work. Oh no. This, as well as many other finds over the last year shows us just how extreme dinosaurs can get. In the past 12 months, we’ve had a new, now with more swimming (TM) Spinosaurus recontruction, Dreadnoughtus, possibly the largest dinosaur ever, as well as long-snouted and pygmy tyrannosaurs. Not to mention feathered ornithischians (R). Dinosaurs have often been regarded as evolutionary extremes, and we’re only now beginning to understand just how these extreme animals lived and evolved.This understanding allows us to further understand evolution works, and how organisms can evolve in various environments and under different conditions.Not only is Deinocheirus a weird and wonderful beast, but when we look at it as a living, breathing animal, rather than a poster-child for all things weird and wonderful, we can begin to further understand  the evolutionary processes involved in theropods, a group which would garner the evolution of an incredibly diverse and successful group of animals, the birds. Deinocheirus exemplifies that palaeontologists, by investigating extremely adapted animals, such as dinosaurs, can further the understanding of the the process of evolution, one of the most important processes on Earth, and just how far it can go, and what wonderfully strange creatures it can help to explain.

So there you have it. Deinocheirus. It sure is a good day to be a palaeontologist.

What’s New(s): 11/04/2014

Avid readers of TDS, we have again not published as often as we’d have liked to over the last few weeks, as deadlines are piling up over here in TDS Towers. Fear not, as below is a bountiful harvest of palaeontological news, five of the most succulent morsels, handpicked by Richard and I, for your entertainment.

Embry-old

Fossilised creatures generally, even those as big as dinosaurs are pretty rare. The forces of nature and preservation all stack up against palaeontologists when we try and find fossils. So when very small fossilised early stage embryos from over 500-million-years-ago are found, it certainly doesn’t go unnoticed. Whilst not new to science, the latest publication of fossil embryo’s gives some much needed insight into how such small and delicate structures were fossilised. Researchers from Missouri and Virginia Tech have found fossilised embryos in the Shuijingtuo Formation (China) which are around 500 million years-old (from the Cambrian period). Despite not being the oldest fossilised embryos (the fossil record of embryos stretches back beyond 580 Mya in the Doushantuo Formation, Pre-Cambrian), the Shuijingtuo embryos contain the soft tissue impressions of the chorion (the fertilisation envelope). The authors also suggest that in this fossil deposit, the preservation of these soft tissues is more common due to these tissues being (somehow) selectively phosphatized. At this point, how these small and rare embryos got to be preserved is all that is known of the Shuijingtuo embryos, but future discoveries on what organisms these embryos belonged to, or even better preserved embryonic soft tissues will prove to be very exciting reads in the months and years to come.

Whilst not the embryos in question, they have caused a massive stir over the years.

Ancient ‘Sp-eye-ders’ from M(ontce)A(u-les-Mines Lage)RS(tätte)

I’m (Ryan) a huge arachnophobe. So I wasn’t best pleased when Richard brought this (albeit interesting) tidbit of news to my attention. A new extinct species of harvestman from the Carboniferous, Hastocularis argus, was recently discovered in France which has allowed the authors to comment on the evolution of the group. It’s also thrown up some eye-opening surprises. Before I continue on the subject, the jovial title of this story is wrong. Whilst harvestmen are arachnids, they aren’t spiders, they’re actually more closely related to mites. Regardless, the discovery of H. argus has allowed Garwood et al. to investigate the origins of harvestmen more closely, as the exoskeletons of these arachnids are rarely preserved in the fossil record. With the creation of a new mite suborder, Tetrophthalmi (which includes H. argus and the Devonian species, Eophalangium sheari), Garwood et al. have, contrary to previous beliefs, argued that the diversification of modern harvestmen occured later in geological time (Carboniferous, rather than Devonian).

The (albeit not so scary looking) Hastocularis argus rendered in full 3D glory.

The (albeit not so scary looking) Hastocularis argus rendered in full 3D glory.

Modern harvestmen have just a single set of eyes, the medial pair (central). However, the 305-million-year-old H. argus has two pairs of eyes, a medial and a lateral (outer) pair. In the same paper, Garwood et al. report that work on modern harvestmen has revealed that despite the passage of over 300 million years, they still retain some genetic framework for these lost lateral eyes. This paper (despite being on arachnids *shudders*) is pretty great, as it combines modern 3D visualisation techniques (CT scanning), phylogenetics and some genetic work in order to really get a handle on the origins of a previously poorly known group. This again proves that the combination of palaeontology and biology is a real ‘dream team’ when it comes to unearthing evolutionary relationships.

 Cambrian heart-thropod’s gets palaeontologists’ blood pumping

I genuinely rewarded myself with a break after making that title, the puns have (if I do say so myself) been exceptional this week. Regardless, a fascinating insight into the evolution of the cardiovascular system has been published in Nature Communications this week (7th April). An exceptional specimen of Fuxianhuia protensa, a 520-million-year-old arthropod from Chenjiang deposits has been described, and with a cardovascular system almost intact. Even though the phylogenetic placement of Fuxianhuia is controversial to say the least, in 2012 it was discovered that Fuxianhuia had a relatively complex brain, suggesting by the early Cambrian, arthropods already had similar visual capabilities as modern insects.

 

Fuxianhuia reconstruction from Ma et al. (2014). a) cardiovascular system and CNS; b) whole body reconstruction; c) cardiovascular system in relation to the gut.

Fuxianhuia reconstruction from Ma et al. (2014). a) cardiovascular system and CNS; b) whole body reconstruction; c) cardiovascular system in relation to the gut.

Perhaps it is a tad unsurprising that this latest Fuxianhuia discovery reveals that the cardiovascular system of arthropods from the early Cambrian were relatively advanced, and more than able to keep the ‘complex’ brain oxygenated with blood. The combination of an advanced cardiovascular and neural/visual system has led Ma et al. to conclude that F. protensa had well developed sensory (using vision and its antennae) system, and in life it was a highly mobile forager. They also conclude that even by the Cambrian Explosion, arthropods had evolved many advanced biological systems.

Teenage Mutant Ninja Hupehsuchians, swimming in a half shell.

Because what would a blog post on TDS be without a marine reptile? (Also, it’s taken until the 4th news piece to get to a tetrapod, what is this nonsense?). Moving on swiftly, the next discovery presents a new species of marine reptile, Parahupehsuchus longus. After taking a quick look at the holotype of P. longus (pictured below) you’d be very much forgiven if you thought it was an early Triassic ichthyosaur. P. longus is in fact a hupehsuchian, which a group of diapsid reptiles from around 250 Ma, and are known exclusively from one locality, in Hubei Province (China).

An incredibly dumb looking hupehsuchian, Nanchangosaurus (a close relative to Parahupehsuchus).

An incredibly dumb looking hupehsuchian, Nanchangosaurus (a close relative to Parahupehsuchus).

So what makes Parahupehsuchus so cool? Well in its defenceP. longus has a weird expansion of its ribs (similar to the ribs of turtles, that’s how they ‘make’ their carapace) which overlap to form a ‘bony tube’. As indicated by the aforementioned pun, Chen et al. think that this is used as a defence mechanism. Whilst the fact that the same kind of defence mechanism (revolving around the expansion of the ribs) has convergently evolved in at least 2 groups of marine diapsids is fairly interesting, it’s the wider implications of this discovery that really make Parahupehsuchus cool. What does any creature needs a defence mechanism for? That’s right Captain Obvious, defence. This almost definitely means that during the early Triassic, there were large predators and a higher trophic level was present at this time. This is odd, you wouldn’t expect this trophic level to recover so quickly after the Permo-Triassic extinction event (commonly referred to as ‘when life nearly died’, so you know, it’s pretty potent). Chen et al. make 2 pretty bold claims from this one discovery, stating that the recovery from the event was faster in the marine realm (specifically faster in marine predators) and that this marine tetrapod predator trophic level is probably the first one ever to emerge in evolutionary history.

Bird’s and pterosaurs had to Cope with one another

Cope’s rule, simply put is a hypothesis that states evolutionary lineages, over time, increase in size. Pterosaurs have long been the poster child of Cope’s rule in the fossil record (along with horses) going from small rhamphorhynchids in the late Triassic to the huge (and probably flightless) azhdarchids of the Cretaceous. The study by Benson et al. set out to try and understand this apparent trend in pterosaur size evolution further. They found that up until the late Jurassic/early Cretaceous the average wingspan didn’t really go above 1m, and over the cretaceous there was a sustained increase in wingspan, until you reach the monstrous 10m+ wingspans of azhdarchids such as Quetzacoatlus northropus.

Obligatory funny, only very slightly related picture.

Obligatory funny, only very slightly related picture.

A controversial notion that it was the emergence and radiation of the (somewhat smaller) birds in the late Jurassic/early Cretaceous that drove the evolution of large size in pterosaurs. In a unexpected turn of events, Benson et al. actually suggest that this may well be the case, citing a possible combination of ‘intrinsic factors’ (such as terrestrial living in azhdarchids and other flight mechanisms in other groups) and ‘extrinsic factors’ (such the evolution of birds, which would have taken the niches occupied by small aerial feeders away from the pterosaurs) as the cause of the switch to selection of a larger body size in pterosaurs. It just goes to show that competition can be, in some cases, used to explain macroevolutionary processes and patterns.

References

Brose, J. et al.  (2014) Possible Animal Embryos from the Lower Cambrian (Stage 3) Shuijingtuo Formation, Hubei Province, South China. Journal of Paleontology: March 2014, Vol. 88, No. 2, pp. 385-394.

Garwood, R. J. et al. (2014). A Paleozoic Stem Group to Mite Harvestman Revealed through Integration of Phylogenetics and Development. Current Biology, http://dx.doi.org/10.1016/j.cub.2014.03.039.

Ma, X. et al. (2014). An exceptionally preserved arthropod cardiovascular system from the early Cambrian. Nature Communications 5, 3560, doi:10.1038/ncomms4560.

Chen X-h, et al. (2014) A Carapace-Like Bony ‘Body Tube’ in an Early Triassic Marine Reptile and the Onset of Marine Tetrapod Predation. PLoS ONE 9(4): e94396. doi:10.1371/journal.pone.0094396

Benson et al. (2014). Competition and constraint drove Cope’s rule in the evolution of giant flying reptiles. Nature Communications 5, 3567, doi:10.1038/ncomms4567.

Taxon of the Week: Koumpiodontosuchus

Dear reader, don’t be put off by such a name, nor by the fact that poor little Koumpiodontosuchus has been dwarfed by Nanuqsaurus, the recently descovered ‘pygmy’ tyrannosaur (more on that when Richard finishes the latest What’s News), because this little Cretaceous critter raises some interesting questions about eusuchian phylogeny. It’s also going to be fairly short, as Richard and I are crazy busy at the moment.

Sometime in March 2011, a lady, out with her family, discovered part of the skull of Koumpiodontosuchus, and almost immediately handed it over to Dinosaur Isle, a museum on the Isle of Wight, UK (as can be seen in my dorky picture on the about page of TDS). In a rather coincidental turn of events, some months later the second part of the skull was donated to the same museum by other denizens of the Isle of Wight. The now completed skull was then meticulously studied by Dr. Steve Sweetman et al. of the University of Portsmouth. Cut to the present day, and what we have is a new species of bernissartiid crocodile (a group that includes some of the smallest neosuchian crocs, i.e. modern crocs and their immediate ancestors) from the Early Cretaceous. Koumpiodontosuchus adds to the already diverse ecosystem we see in the Early Cretaceous of the Isle of Wight, which includes an allosaur (Neovenator), Iguanodon, Polacanthus (a thyreophoran), Eotyrannus, good old Baryonyx and a brachiosaur (as well as some azdharchid pterosaurs and mammals).

A wonderful reconstruction of early Cretaceous life on the Isle of Wight. Courtesy of Mark Witton.

A wonderful reconstruction of early Cretaceous life on the Isle of Wight. Courtesy of Mark Witton.

Estimated at only 66cm in total length, Koumpiodontosuchus aprosdokiti (roughly meaning button toothed, unexpected) is a small croc with a big name. As the name suggests, Koumpiodontosuchus has ‘button’ teeth (broad and flat) situated at the back of the jaw, with pointier teeth towards the front. This dental arrangement meant that Koumpiodontosuchus could have a good crack at both catching fish at eating hard-shelled material such as molluscs. Despite its neat arrangement of teeth, its not Koumpiodontosuchus’ crowning glory. That prize belongs to the choanae.

Koumpiodontosuchus reconstruction, again by Mark Witton. Also, casual Neovenators in the back there.

Koumpiodontosuchus reconstruction, again by Mark Witton. Also, casual Neovenators in the back there.

In crocodiles, the choanae are found in the upper jaw and form the internal nostril openings (holes). Despite containing all the extant crocodiles and their recent common ancestors, Neosuchia has a subgroup called Eusuchia (“true” crocodiles”) in which all modern crocs are found. Now, there are many defining features that allow palaeontologists/taxonomists/biologists to distinguish eusuchians from the larger pool of neosuchians, but a big defining feature in recent years has been the placement of the choana(e) within the pterygoids, towards the back of the skull (if you’re getting a bit lost with crocodilian cranial anatomy, the Witmer/Holliday Lab 3D alligator project really does help a bunch). Bringing it back to the early Cretaceous of the Isle of Wight, Koumpiodontosuchus is a non-eusuchian neosuchian (it’s just a neosuchian, no big deal), so you’d expect it not to have its choana placed at the back of the skull, between the pterygoids. 

Holotype of Koumpiodontosuchus. Choana circled in red. Amended from Sweetman et al (2014).

Holotype of Koumpiodontosuchus. Choana circled in red. Amended from Sweetman et al (2014).

Well would you look at that, a choana at the back of the skull and between the pterygoids, now that sure is a turn out for the books. So what does this mean? Well it adds to the amassing evidence from other extinct crocs (e.g. the Madagascan Mahajangasuchus, a rather ugly looking brute from the late Cretaceous) that the placement of the choana(e) within the pterygoids, on its own, might not be a might sign from the taxonomic gods that the croc you’re looking at is a eusuchian.

TL;DR: Koumpiodontosuchus is a cool new (small and cute) croc from the early Cretaceous of the Isle of Wight who, despite its size, manages to further challenge the taxonomic rules that define key groups of crocodylomorphs. Pretty cool, even if a tad unpronounceable.

Taxon of the Week: Limusaurus

As a treat, this week’s Taxon of the Week is a dinosaur. Even better, it’s a dinosaur with very small hands. Despite it’s small hands, it’s managed to cement itself amidst a pretty sizeable debate, yes ladies and and gentle, this week’s TotW is Limusaurus inextricabilis.

The facts

Limusaurus was discovered in 2009 by Xing Xu, a Chinese palaeontologist whose seemingly always discovering a new species of dinosaur (over 30 valid species to date). At around 1.7m in length (roughly the size of a large-ish dog), Limusaurus was far from the biggest and most exciting looking new dinosaur of 2009, however, it was certainly a bit weird:

  • For starters it’s the first Asian ceratosaur ever described. Yes, you heard right a ceratosaur.
  • For your main course, it’s herbiverous.
  • To finish off with dessert, it’s got a beak.
Limusurus. Not your average ceratosaur.

Limusurus. Not your average ceratosaur.

True, whilst indeed not your average ceratosaur (or for that matter, theropod) such traits aren’t that weird in primarily carniverous clades. Within Theropoda, there’s many secondarily herbiverous taxa, incl. everyone’s favourite weirdo taxon, the therizinosaurs. Let’s also not forget the well known beaked herbiverous theropods, ornithomimosaurs. Oh, and did you know crocodylomorphs had a crack at beaks and herbivory (of course they did). Even though I keep harping on about its small hands, for frak’s sake, just take a look at alvarezsaurs (with even more pathetic arms than T. rex). So why exactly am I taking the time to blog about Limusaurus?

Mononykus trying, the meme that couldn't be due to it's preposterously pathetic forelimbs. Hastily drawn by me.

Mononykus trying, the meme that couldn’t be due to it’s preposterously pathetic forelimbs. Hastily drawn by me.

A debate as simple as 1, 2, 3

If you’re a fan of dinosaurs/palaeontology then you should be aware that birds evolved from theropod dinosaurs. News flash: this isn’t new. This notion really started to gain ground after seminal work by John Ostrom in the late 1960s/early 1970s (including that famous drawing of the ‘naked Deinonychus‘ as Richard likes to call it) who noted a lot of avian-like features in Deinonychus. On top of that, palaeontological records show multiple transitional forms between smaller theropods and birds (e.g. the ever eminent Archaeopteryx), and even some of the larger theropods show avian affinities (e.g. the cranial pneumatic sinuses found in Alioramus). Those are only a select few pieces of evidence that have made the evolutionary link between birds and theropods almost undeniable, there’s a so many more, it’s astounding (incl. inferred behaviour, such as avian sleeping positions in theropods: Xu & Norell 2004, and apparent egg brooding behaviour in Oviraptor: Norell et al. 1995). Watch the video if you need more peer reviewed proof that dinosaurs (even if they did look a bit like birds) were awesome. Try and show a little respect.

However, there’s always new discoveries that just love to get people arguing. The issue revolves around digit homology/identity. Essential, theropods (via evolution) ‘lost’ two fingers (digits) to arrive at the three-fingered hand seen in most theropods (aside from the aforementioned ‘weird taxa’, who lost more than 2). The same is true for birds. However, the debate revolves around which digits are lost, and which 3 form the fingers of the hand. In tetanurans (essentially the more advanced theropods, and by extension birds), it has long been thought that digits IV and V were lost, leaving a three-fingered hand consisting of digits I, II and III. Now, you’d expect birds, by being derived tetanurans to have this digital formula.  Well that would be nice wouldn’t it. Unfortunately the question of I,II,II or II,III,IV in modern birds has been debated for a very long time. New evidence in the mid-late 1990s from developmental and genetic studies showed us that the three digits of the avian hand actually developed from digits II, III and IV. Gasp, a spanner in the works!

This new evidence was then used (rather wrongly) to attempt to oppose the hypothesis that birds evolved from dinosaurs (Feduccia 2002). While I agree, the 90s developmental evidence from modern birds creates some novel evolutionary dynamics to investigate, it cannot be used to deny the whole host of other evidence that links dinosaurs to birds. Following on from the developmental studies, genetic studies in the early 2000s showed that during the ontogeny of some birds, the digit identity would change from the initial II,III,IV to I,II,III. This led to the occurrence of the ‘Frame Shift’ hypothesis, which suggests that certain genetic pathways associated with dinosaur/avian digit identity allow for ‘rapid’ changing of digit homology throughout dinosaurian/avian evolution (at it’s core, and that’s a very simplified summary). Not to be bogged down by detail (genetics isn’t my strong suit), developmental geneticists thought they’d cracked it, and that the change in digit identity over avian/dinosaurian evolution was likely to have been caused by these frame shifts.

Feduccia's (2002) argument in a nutshell.

Feduccia’s (2002) argument in a nutshell.

Enter Limusaurus. So, finally, we come to Limusaurus’ role in all of this. In 2009, Xu et al. looked at Limusaurus’ small hands and went “you know what, that’s a reduced digit I” (NOT ACTUAL QUOTE), which makes Limusaurus’ digit identity II, III, IV. As we discovered right at the start of this article (before the I made my lack of genetics knowledge crystal clear), Limusaurus is a ceratosaur, which isn’t a tetanuran, but a more primitive theropod, meaning that the II,III,IV digit identity may well be shared by most/all tetanurans, with Limusaurus representing an intermediate of sorts. Thus Xu et al. state that the digit identity of Limusaurus is more in favour of a slower, stepwise acquisition of the digit identity seen in advanced tetanurans, and eventually birds. But, as the famous saying goes, you know what small hands means…(small gloves?)

That’s right, a big controversy.

If you're confused (don't worry, so am I), this may help.

If you’re confused (don’t worry, so am I), this may help.

The small gloves are off

The Xu et al. (2009) caused a fairly serious debate, with authors such as Vargas et al. arguing that the digit condition seen in Limusaurus is derived, and based on developmental and genetic work that they (Vargas et al.) carried out, suggest that faster genetic shifts occurred in the evolution of birds. Xu et al. quickly responded (and quoted  Arthur Conan Doyle in a somewhat dramatic conclusion) and argued that the shift proposed by Vargas is not likely when the digit (and manus) morphology of fossil tetanurans is considered.

I’d sincerely like to end this post with a succinct conclusion, saying that the debate has, over the last few years been wrapped up. However, such large debates in palaeontology, due to the very nature of our field (i.e. everything we love is dead) are rarely fully resolved. This case is no exception. Researchers from Yale (Bever et al. 2011) and other top world universities have stated time and time again that the frame shift hypothesis is still viable in the context of avian evolution, and in a recent summary by Xu and Mackem, Xu is not so sure, saying neither hypothesis has evidence to topple the other. Not one for revelling in an unnecessarily depressing ending (*coughs* Firefly) I’ll leave you with this: yes, we can’t always find all the answers to big questions in palaeontology and evolution, but by creating a synergistic relationship between palaeontology and biology (genetics, evo devo etc.), future discoveries in both fields are sure to shed some light on even the biggest of debates.

If you’d like to read more on this subject, and weren’t put off by my murdering of the genetics side of things, then I’d highly recommend the aforementioned Xu & Mackem (2013) paper for a recent summary of the field (see references below, it’s in bold).

References

Xu, X. et al. (2009). A Jurassic ceratosaur from China helps clarify avian digit homologies. Nature 459, 940-944.

Xu, X. & Mackem, S. (2013). Tracing the Evolution of Avian Wing Digits. Current Biology 23, R538–R544 (and references therein).

Bever, G., S. et al. (2011). Finding the frame shift: digit loss, developmental variability, and the origin of the avian hand. EVOLUTION & DEVELOPMENT 13:3, 269–279.

Vargas, A.O., Wagner, G.P. & Gauthier, J.A. in Nature Proceedings (2009).

Vargas, A.O. & Wagner, G.P. Frame-shifts of digit identity in bird evolution and Cyclopamine-treated wings. Evolution & Development 11, 163-169 (2009).

Young, R. L. et al. (2011). Identity of the avian wing digits: problems resolved and unsolved. Dev Dyn. 2011 May;240(5):1042-53.

Taxon of the Week: Beelzebufo.

Yet again, Richard and I are falling behind on delivering on the blog front. For that, we apologise. The next 7 days (hopefully) should bring numerous posts to make up for lost time, including an opinion piece!

Anyway, on with the show. If you follow palaeontological news in any sense, then you’ll probably have heard about a new marine reptile called Atopodentatus. If you haven’t heard of Atopodentatus, imagine if you will the offspring of a basal sauropterygian, Predator, and Cthulu that potentially could have filter fed. Or, you could just check out Brian Switek’s well written Atopodentatus article (with pretty pictures). That’s right, this week we’re going against the grain, and focusing in on a big Cretaceous amphibian, that’s made for a big controversy. I assure you, it’s going to be ribbeting.

Big facts: “we’re gonna need a bigger pond”.

This week, our TotW is Beelzebufo ampinga. Before we knuckle down and attempt to remove the f(r)og from the controversy, let’s get down to the basics. B. ampinga was discovered in 2007 by a team from Stony Brook University from the Maevarano Fm, Madagascar, the remains dated to 70-65Ma (late Cretaceous). The initial paper had little to work with, as the holotype only consists of a few cranial elements, with a few vertebrae, a urostyle and a tibiofibula. However, even with such few remains, the initial size estimates for Beelzebufo are astonishing: with a length of over 40cm, and its head alone estimated at half that in width (20cm!). This immediately bestows Beelzebufo with the crown of the largest frog to ever have lived. Beelzebufo was initially placed within the Ceratophryinae (the common horned frogs), which is unusual and is the basis of most of the controversy surrounding B. ampinga (more on that later). Due to it’s phylogenetic position, Beelzebufo has hyperossification in the skull, stabilising connections between the upper jaw and the skull, a huge mouth, oh, and sharp teeth. What does this mean? Well, like all other ceratophyrines Beelzebufo probably was carniverous, and by being so large, many agree that it would have been an ambush predator of small vertebrates, such as small/baby dinosaurs. So a frog that eats dinosaurs, no wonder they called it Devil Frog.

Evans2008

The holotype of Beelzebufo. Bones that were discovered in white. Modified from Evans et al. (2008).

Earlier in 2014, Beelzebufo was back. This time a (open access!) paper was published, showing off many new specimens of the Devil Frog. These specimens (64 since 2007) were far more complete than the original published findings, and have shown us that it was far weirder than previously imagined. It also gave us a more complete picture of B. ampinga as an organism and as a species. By looking at the squamosal of different individuals it became apparent that there was a lot of intraspecific variation present in B. ampinga, with a size difference of up to 20% present between certain individuals. This has found to be caused by different individuals having different bone growth rates and patterns. Now, the simplest explanation is everyone’s favourite, sexual dimorphism (in modern ceratophryines, the females are larger than males in 90% of cases). However, studies on extant frogs have shown that bone growth patterns and maturation times in anurans can be dependent on other factors such as seasonal food and water availability, as well as temperature.

SOON.

SOON.

Another intriguing fact is that Madagascar at that time was seasonal arid, with dry periods being especially water-sparse. So how does a large amphibian like Beelzebufo cope? Again, material from the 2014 publication (Evans et al. 2014) helps us to possible answer this. Hyperossification (especially in the skull) is prevalent in Beelzebufo. This is apparent in the initial discovery also, but combine this with evidence from Evans et al. (2014), features such as the loss of a tympanic membrane, tall neural spines and cranial exostosis go some way towards confirming that Beelzebufo was a burrower. Thus enabling it to escape desiccation during extreme dry spells. Not only did Evans et al. (2014) provide us with a wealth of new information on an important fossil anuran, but it also came with some fantastic 3D skeletal morphological reconstructions.

Evans2014

The aforementioned pretty digital reconstruction. Also, those posterolateral flanges, phwoar. Modified from Evans et al. (2014).

Big controversy

As has been eluded to, Beelzebufo caused a big splash. Evans et al. (2008) placed B. ampinga within Ceratophryinae, a subfamily found only in South America, based on mainly cranial characters and a supporting phylogenetic analysis. Evans commented that the discovery of a late Cretaceous ceratophryine in this area is ‘unexpected’. Indeed, if you look at the palaeobiogeography it still looks squiffy, with the Madagascar-Seychelles-India tectonic plate losing contact from South America 120 million years-ago. However, even this is debated. Multiple lines of evidence now suggest some land-link was present between South America and Madagascar, including many molecular studies (ratite birds, iguanin lizards et al.) and physical similarities present between South American and Madagascan dinosaurs, crocodyliforms and mammal. So a ceratophryine from the Cretaceous of Madagascar isn’t so crazy, right?

Wrong. Two years after the initial Evans publication Ruane et al. (2010) carried out rigorous testing on the phylogenetic position of Beelzebufo. In Evans et al. (2008), it was apparently established that B. ampinga was a crown-group Ceratophryinae, and a sister taxon to the living Ceratophrys. Ruane et al. had a big problem with this reasoning, stating that the relationship between Beelzebufo and Ceratophrys is supported by 1 out of 81 characterstics, support values for the relationship between these two were also low in the phylogenetic study. Ruane et al. (2010) used molecular phylogenies (with data from extant anurans) in tandem with Beelzebufo, using it as a calibration point, to calculate the timings of the emergence of the MRCA (most recent common ancestor) of modern ceratophryines. With Beelzebufo used in this way, the emergence time of the ceratophryine MRCA was way before the times calculated by other studies, using well established datasets.Ruane et al. came to the conclusion that contrary to Evans’ initial hypothesis, Beelzebufo was a) not a sister taxon of Ceratophrys or b) definitely not a crown-group ceratophryine. However, Ruane et al. don’t really give us more than that, apart from saying it might be some sort of stem-group ceratophryine or a crown-group Hyloidea (a superfamily). If were throwing ballpark ideas around for the phylogenetic position of Beelzebufo, then I’m gunning for a stem-group Hynerian.

dominarrygelxvi

Dominar Rygel XVI, a fine example of Hynerian for all those nerds who don’t watch Farscape.

The Evanpire Strikes back

Not one for lying down Evans et al. (2014), now armed with many more specimens than last time around, resurrected the phylogenetic controversy surrounding B. ampinga. In the 2014 publication, the phylogenetic position of Beelzebufo was restored to the initial hypothesis, stating that Beelzebufo was indeed a crown-group ceratophryine, with this relationship holding true even when different tree-making steps and calibration points were used. Evans et al. also deal with many of the issues raised by Ruane et al. For example, Ruane et al. argue that the low support values between Beelzebufo and Ceratophrys indicate that they might not be sister taxon (and hence Beelzebufo isn’t part of the ceratophryine crown-group). Yet Evans et al. point out that support values are low even in studies that solely consider extant ceratophryids.

The fuzzy phylogenetic positioning given to Beelzebufo by Ruane et al. (maybe stem-group this, or crown-group that) is put under fire by Evans et al. I’ve already said that the Cretaceous MRCA emergence time is Ruane’s main argument against B. ampinga as a crown-group ceratophryine, however what I’ve not yet said (and what Evan’s et al. 2014 love to point out) is that Ruane et al. almost positively place another mid-late Cretaceous frog, Baurubatrachus as a ceratophryid (crown and/or stem), which still means that the MRCA is somewhere in the Cretaceous. Evans was quick (p.54) to point out that Ruane et al. at this point were being somewhat hypocritical in this regard. Finally, Evans points out that the hyperossification present in Beelzebufo is also present in living ceratophryids, another compelling line of evidence in support of the crown-group hypothesis. Despite being confident in their findings, Evans et al. still give a passing mention of the notion that hyperossification (and other ceratophryid characters) may be present due to convergent evolution, however, for the time being (and to conclude!) Beelzebufo appears to be (for the time being) a crown group ceratophryid. *Sighs*.

You've made it past the long-winded bit. Well done, have a pretty picture.

You’ve made it past the long-winded bit. Well done, have a pretty picture.

Big importance

Well done, you’ve made it through a very poorly written account of the s**t-storm which is the phylogenetic positioning of Beelzebufo. By this point, you’ve probably seen the words crown, stem, Beelzebufo, et al. and ceratophryine/d/inae enough to last multiple lifetimes, so then, why should we care about Beelzebufo and it’s position within the ‘tree of life’. You should care for two reasons: 1) the timing of the emergence of ceratophryids, 2) the importance of correctly using fossils in phylogenetic studies.

All glory to the importance of Beelzebufo. You will obey.

All glory to the importance of Beelzebufo. You will obey.

You should remember that the biogeography of Madagascar in the Cretaceous creates problems for the ceratophryid hypothesis. Ali et al. (2008, 2009 2011) have recently noted that land bridges between Madagascar and South America were severed by 115-112Ma. If this is true, (and presuming Beelzebufo and undiscovered others didn’t raft across the seaways, which is actually a large presumption, giving the thick skinned Beelzebufo would weather the salty waters well, for a frog) this pushes the emergence time of ceratophryids to before these dates. This is again contrary to studies that have found the emergence times of crown-group Hyloideans (a superfamily if you remember) to be around 88Ma. As has been stated many times of this blog, any fossil, even an incomplete specimen, if found in the certain places at certain times can cause palaeontologists/phylogeneticists/biologists to have to seriously reconsider the state of the field.

This leads nicely onto the second reason why Beelzebufo is important. Hypocritical arguments aside, Ruane et al., using Beelzebufo as an example, shows how any study using fossils as certain anchor points in phylogenetic studies MUST look closely at the phylogenetic position (and the evidence behind it) of the fossil taxa, and decide if this is appropriate. Any mistakes when involving fossil taxa in these studies affects conclusions with wide reaching implications, such as the divergence/emergence times of certain, and sometimes, very large clades.

And finally, Beelzebufo kinda looks like Hypno Toad. That’s pretty rad.

References

  • Evans, S. E. et al. (2008). A giant frog with South American affinities from the Late Cretaceous of Madagascar. Proc. Natl. Acad. Sci. USA 105: 2951–2956.
  • Evans S. E. et al. (2014). New Material of Beelzebufo, a Hyperossified Frog (Amphibia: Anura) from the Late Cretaceous of Madagascar. PLoS ONE 9(1): e87236. doi:10.1371/journal.pone.0087236
  • Ruane S. et al. (2011). Phylogenetic relationships of the Cretaceous frog Beelzebufo from Madagascar and the placement of fossil constraints based on temporal and phylogenetic evidence. J Evol Biol 24: 274–285.
  • Ali J. R., Aitchison J. C. (2008). Gondwana to Asia: plate tectonics, paleogeography and the biological connectivity of the Indian sub-continent from the Middle Jurassic through end Eocene (166–35 Ma). Earth-Science Reviews 88: 145–166.
  • Ali J. R., Aitchison J. C. (2009). Kerguelen Plateau and the Late Cretaceous southern-continent bioconnection hypothesis: tales from a topographical ocean. J Biogeogr 36: 1778–1784.
  • Ali J. R., Krause D. W. (2011). Late Cretaceous bioconnections between Indo-Madagascar and Antarctica: refutation of the Gunnerus Ridge causeway hypothesis. J Biogeogr 38: 1855–1872.

Taxon of the Week: Postosuchus

In this week’s TotW, Ryan takes us through the posto child of the ‘rauisuchians’, Postosuchus.

When someone mentions the Mesozoic, you instantly think about dinosaurs. Admit it, it’s fine, there’s no judgement on this blog. You also will predominately think about dinosaurs from the Jurassic and the Cretaceous, with good old T. rex and co. (allosaurs, carcharodontosaurs, spinosaurs etc.) ruling the roost at the top of the food chain, whilst sauropod behemoths (amongst other ridiculously sized herbivores) wandering about in herds etc. etc. However, the Triassic (seemingly the Cretaceous and Jurassic’s ugly sister) is often forgotten about. Yes, we don’t have things which are outrageously large or ridiculously bipedal (or do we..?), but in the Triassic, crurotarsans (crocodile-line archosaurs) were having a bit of a field day.

awesomesozoic

The image that immediately springs to mind as soon as you mention ‘Jurassic’ or ‘Cretaceous’. Clearly.

Here on TDS, we think the Triassic (as well as plenty other eras, not just the Jurassic and Cretaceous) is pretty awesome too. The Triassic was a time of recovery, the Permian-Triassic mass extinction event had been and gone (and almost taken all of life on Earth with it). Dinosaurs were just starting out, and sitting on top of the food chain was, you guessed it, Postosuchus. If you look at the skull of Postosuchus kirkpatricki below, look carefully. Back in the 1980s famous palaeontologists thought Postosuchus (along with Poposaurus) could be a tyrannosaur ancestor. You can see where they’re coming from. Postosuchus was first discovered in 1922, and for 60 odd years after that, people didn’t really know what to make of it. First reports penned it as a Coelophysis, 20 years later, other finds were thought to belong to a new phytosaur. It wasn’t up until 1985 that the holotype, a well preserved skull and some postcranial remains, of Postosuchus kirkpatricki was formally announced. 

BronzePostosuchus

Totally not a dinosaur. No seriously.

Weighing in at almost 300kg, at reaching almost 4m when fully grown, Postosuchus was one (if not the) largest predator in the Triassic. With good long distance vision, a decent sense of smell, and a possible Jacobson’s organ, and oh, not to mention, over 7cm dagger-like teeth, this killing machine well may have taken down a fair few aetosaurs in it’s time (not a small feat). So fairly fearsome, but not as impressive as the theropods that were to come later in the Mesozoic, surely? Well, again, no.

tumblr_m3zd8iT4YA1rrpn3bo1_500

These coelophysoids clearly came to the wrong neighbourhood.

What makes Postosuchus (and many other ‘rauisuchians‘) so interesting are its hindlimbs. One of the major dinosaurian innovations was the erect hindlimb posture, enabling more efficient locomotion. In the Triassic, descendants of crocodiles (who now have the ‘sprawling’ hindlimb posture) such as Postosuchus had a go at this hindlimb arrangement (evolutionary speaking). Whilst debated, many palaeontologists view Postosuchus (amongst other Triassic crurotarsans) as being bipeds (or at the very least facultative bipeds). So that means Postosuchus could use it’s forelimbs to kill things as well as it’s terrifyingly huge mouth (like bears do). To summarise, Postosuchus is a nightmare-inducing, killer croc-bear from back in time. It also raises the question (to be investigated by a future blog post on TDS, hopefully) of why exactly did dinosaurs survive through to the Jurassic, and rauisuchians go extinct, and why did crurotarsans go back to being solely quadrupedal?

biobeast-sm

Killer croc-bear from back in time. (Thank you internet).

Told you the Triassic was awesome. (Also, more to come on the locomotory strategies of Triassic crurotarsans to come, right after I finish my final 4th year exams…).

Bonus picture (because it’s cool and reasonably accurate, although not as accurate as the previous picture):

Postosuchus_mural

There’s no escape from the Post(o) Man (not actually a man).

References

  • Case, E. C. (1922). “New reptiles and Stegocephalians from the Upper Triassic of western Texas”. Carnegie Institution of Washington Publication 321: 1–84.
  • Case, E. C. (1932). “On the caudal region of Coelophysis sp. and on some new or little known forms from the Upper Triassic of western Texas”. University of Michigan Museum of Paleontology Contributions 4 (3): 81–91.
  • Case, E. C. (1943). “A new form of Phytosaur pelvis”. American Journal of Science 241 (3): 201–203. doi:10.2475/ajs.241.3.201.
  • Chatterjee, S. (1985). “Postosuchus, a new Thecodontian reptile from the Triassic of Texas and the origin of Tyrannosaurs”. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 309 (1139): 395–460. doi:10.1098/rstb.1985.0092.
  • Drymala, S. & Bader, K. (2012). Assessing predator-prey interactions through the identification of bite marks on an aetosaur (Pseudosuchia) osteoderm from the Upper Triassic (Norian) Chinle Formation in Petrified Forest National Park (Arizona, USA). Journal of Vertebrate Palaeontology, Program and Abstracts 2012, p89.

What’s New(s): 6/01/2014 incl.; Naked Dinosaurs, Saudi Arabian dinosaurs and Ichthyosaur storms.

Christmas is a time of rest, festive cheer, spending time with loved ones and (probably most importantly) food.       This is seemingly not the case for academics. Firstly, Richard and I have been busy revising for our January finals, so whilst we’ve tried to give you a few juicy morsels over to tide you over the festive season, we’ve not really had chance to bring you the latest news. Coupled with this is that over this year’s festive period there’s been a lot of palaeontology going on. Holiday, what holiday?

blog

PhD Comics, get used to laughing (and crying) along to them as a postgrad.

So here is a What’s News(s) bumper edition, with 5 of the biggest news stories in palaeontology over the festive period. This week, we’ve got Saudi Arabian dinosaurs, naked dinosaurs, ichthyosaurs, body-size trends in evolution and some Hungarian palaeoneurobiology! Since we don’t want to spam you, we might start evolving our What’s New(s) sections so they are weekly, rather than as-and-when the news comes out (unless it’s really cool).

The first Saudi Arabian dinosaurs. Like has been previously stated, new dinosaur finds aren’t rare occurrences. They happen roughly every 1.5 weeks. Big deal right. Wrong (again). Benjamin Kear’s team have discovered a few caudal vertebrae and some teeth from Saudi Arabia, from the Maastrichtian (75 Ma, ish), and have confidently identified the vertebrae to be from a titanosaur, and the teeth to be from an abelisaurid. The confidence of these groupings is the first time that fossils the Arabian peninsula have been able to be classified as dinosaurian without contention. It also stretches the palaeogeographical ranges of titanosaurs and abelisaurids to the northern margin of Gondwana, whilst showing us (with just one find) that dinosaur ecology in this area may have been quite diverse in the mid-late Cretaceous. The papers also open access (over here on PloS One).

saudidinos

A-C: vertebra of a titanosaur from Saudi Arabia; D-F: tooth of a abelisaurid (again from Saudi Arabia). From Kear et al. (2013).

Naked dinosaurs a common sight during the Mesozoic. For a pretty ‘young’ blog, we’ve already mentioned naked dinosaurs (ooo err!) twice. That says a lot about Richard and I. Moving swiftly on… Since the discovery of the feathered Sinosauropteryx in 1996 (and a plethora of other feathered Chinese dinosaurs since) has caused a bit of frenzy. So much so, that even the Jurassic Park conceded, and created this monstrosity (they’ve now de-conceded, and have yet again ignored feathered dinosaurs). Since 1996, palaeontologists have endeavoured to find just how far back feathers go in the dinosaur lineage. Up until the early 2000s, we thought we had it covered, and that feathers were ancestral to theropods (with discoveries such as Dilong paradoxus, a feathered tyrannosaur sparking fierce debate over whether good old T. rex  had a majestic feathered coat). Yet, as always, it only takes one discovery to turn everything upside down. Pscittacosaurus was that discovery. Pscittacosaurus is a ceratopsian (basal relative to the frilled dinosaur celebrity Triceratops), but with some proto-feathers. Crazy times.

bakker deino

Richard’s favourite naked dinosaur, Deinonychus (which probably wasn’t naked at all).

Paul Barrett then set about to try and solve just where the feathered dinosaur bus stopped. He and his team looked at all of the dinosaur skin impressions found to date, looking for any sign of feathers (or similar structures) and then considered the data is a evolutionary context. He concluded that despite Pscittacosaurus, most ornithischians (ceratopsians, ornithopods, pachycephalosaurs and thyreophorans) and sauropods would have had scales. With the majority of dinosaurian clades having scales rather than feathers, Barrett tentatively concluded (at SVP 2013, in sunny Los Angeles) that scales were probably the ancestral condition in dinosaurs.  But by now we know that all it takes is one feathered dinosaurs from the Triassic (or even the early Jurassic) to upheave this study.

The I(chthyosaur) of the Storm. Quick bit of local (for British palaeontologists  anyhow) news for everyone. After heavy storms (no, seriously, before any Americans/Canadians/anywhere with ‘proper weather’ complain) a 1.5 m long partial ichthyosaur skeleton has been revealed at the base of a cliff in Dorset, and is being restored by the Jurassic Coast Heritage organisation. Three ichthyosaurs have been revealed in similar ways after storms in the past year along the Jurassic Coast. So remember kids, 80mp/h winds and floods aren’t all bad.

Ichthyosaur_hharder

That’s right, icthyosaurs can fly. And then they become storms. True story (Not actually true).

Growing fields: body-size trends throughout the fossil record. Whilst by no means is the study of body-size trends through evolutionary history a new field, but Mark Bell has just published a brilliant, relatively short and Open Access (whoop!) introduction to body-size trends in the fossil record. The article really does make you feel rather small (literally). It also goes through some long established rules on body-size evolution (e.g Cope’s rule), whilst also noting some nice examples of giganticism and dwarfism in the fossil record. Finally, he also states that new computer simulations/software maybe able to help us to further understand these trends in the future.

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Where’s Wally, PhyloPic edition. (From Bell 2013 and PhyloPic).

The very Hung-a-ry dinosaur brain. This gem of palaeontological news really does show how fieldwork and digital analysis can produce fantastic results. A new find of a partial skull of Hungarosaurus (from, you guessed it, Hungary) has enabled Hungarian palaeontologists to made a cast of the endocranial cavity, allowing them to analyse the braincase of this European anklyosaur. Initial results suggest that the cerebellum (area of the brain associated with motor control) is larger in volume than other ankylosaurs. This may well mean that Hungarosaurus was better able to run than other anklyosaurs (well known for not being the fastest of starters…).

hungarybrain

Endocast of Hungarosaurus. cbl=cerebellum (roughly circled, from Osi et al. 2013)

References:

Kear BP, Rich TH, Vickers-Rich P, Ali MA, Al-Mufarreh YA, et al. (2013) First Dinosaurs from Saudi Arabia. PLoS ONE 8(12): e84041. doi:10.1371/journal.pone.0084041

Mayr, G., Peters, D. S., Plodowski, G. & Vogel, O. Naturwissenschaften 89, 361–365 (2002)

Zheng, X.-T., You, H.-L., Xu, X. & Dong, Z.-M. Nature 458, 333–336 (2009).

http://www.nature.com/news/feathers-were-the-exception-rather-than-the-rule-for-dinosaurs-1.14379

http://www.bbc.co.uk/news/uk-england-dorset-25548426

http://www.palaeontologyonline.com/articles/2014/trends-body-size-evolution-fossil-record-growing-field/

Ősi, Attila, Pereda Suberbiola, Xabier, and Földes, Tamás. 2014. Partial skull and endocranial cast of the ankylosaurian dinosaur Hungarosaurus from the Late Cretaceous of Hungary: implications for locomotion, Palaeontologia Electronica Vol. 17, Issue 1; 1A; 18p;
palaeo-electronica.org/content/2014/612-skull-of-hungarosaurus

FAQ: Richard.

To give people an idea of who we actually are before we start dinosauring at you, we thought we’d introduce ourselves via a series of ‘FAQs’.  Here’s mine!

Richard

First and foremost, what’s your favourite dinosaur?

At the age of 6 I’d immediately have answered Deinonychus, but the naked kind (eg. picture below) without any feathers.  I would then have proceeded to bore you with my standard soliloquy on how the raptors in Jurassic Park were actually more like Deinonychus, thus justifying my obscure dinosaur choice.

bakker deino

The awkward, naked sprint from shower to bedroom was a problem even in the Cretaceous.

Since then my dinosaur tastes have progressed a bit, but I think I’ll still pick Deinonychus.  As well as being nicely symbolic of the paradigm shift towards viewing dinosaurs as active animals, it has also become feathered fairly recently, representing another change in dino-views.  It also had HUGE CLAWS.

Secondly, what’s your favourite (preferably extinct) animal?

While lots of things are awesome I think I probably ought to choose the Devonian placoderm, Dunkleosteus.  While (obviously) all Palaeozoic fish are exciting, a 10m long one with shearing jaw bones is particularly so.  Also comes highly recommended as a fancy dress costume.

What’s your area of ‘expertise’?

I think ‘expertise’, as opposed to actual expertise, is definitely the right word to use.  I enjoy systematics and evolution-based themes, in pretty much any group.  My project this year is on a group of armoured, jawless fish called heterostracans, so I’m looking forward to learning about them as the year progresses.   My undergrad degree is in Zoology, so I like to flatter myself that I bring a critical zoological eye to palaeobiology.  This is probably not actually the case.

How did you get into palaeontology?

Playground conversations about Jurassic Park and the fact that Walking With Dinosaurs came out when I was small and impressionable both contributed to a love of palaeontology from a young age.  My grandfather is a zoologist who has done work on dinosaurs, and so he fanned the flames by doing things like introducing me to a robotic Iguanodon (see picture).  I then wanted to be a military historian for a bit, before doing a degree in natural sciences, which eventually became zoology as I tried to get as far away from cellular biology as possible.  This zoology degree heavily featured palaeo, which reignited my love of it and led me to this master’s degree.

iguano robot2

The model T-8Ig Terminator was swiftly scrapped by Skynet, after proving to be even less successful at blending into human society than Arnold Schwarzenegger.

What do you do in your spare time?

Mainly musical things.  I play the ukulele and the clarinet, and dabble in a number of other instruments.  I also enjoy singing; previously this has been in Chapel Choirs and things, but has more recently been barbershop.  I also enjoy reading and baking bread.

Favourite palaeontological paper?

I really like this paper describing paired anal fins (weird!) in the jawless fish Euphanerops because the fossil is quite pretty and it has a really nicely structured, clear diagram portraying the evolution of paired fins in vertebrates.  It also provides a tantalising glimpse into the evolution of key characters in gnathostomes (jawed fish), which (as with so much in evolution) seems to form an evolutionary mosaic rather than a straightforward progression from one character state to another.

SansomPhyloOrig

Bask in the clarity of this figure! Green is for dorsal fins, red is for paired fins and blue is for anal fins. Adapted from Sansom et al, 2013

You’re a palaeontologist, so you’re like Ross from ‘F.R.I.E.N.D.S’?

Ross never actually seemed like a very good palaeontologist, so I hope not.  I’ve also only been married twice.

Any tips for any budding palaeontologists out there?

I suspect that I still count as a ‘budding palaeontologist’, but disregarding that my tips would probably centre around a general theme of ‘get keen’.  There’s an enormous number of blogs and things on palaeobiology on the internet, and through the medium of Twitter you can get information on opportunities and palaeo news directly from palaeontological luminaries (or at least those luminaries who have Twitter).