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.

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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.

What’s new(s): 22/03/14

We’ve got a range of stories for you in this week’s What’s News including evolving cetaceans, pygmy dinosaurs, and aquatic ground sloths.

A long-mandibled porpoise

Cetaceans are fairly weird animals to begin with: secondarily aquatic even-toed ungulates (like cows and sheep) that are grouped with hippos in the colourfully-named group, the Whippomorpha.  They’ve lost their back legs, have adapted their front ones to form flippers, and have developed dorsal and tail fins, and this morphology has proved extremely successful as they have radiated to fill many niches in the oceans, including filter feeding, suction feeding and giant squid eating.  A new fossil porpoise has recently been described from the Pliocene of California that adds to this diverse array of morphologies with it’s bizarrely shaped lower jaw.  The lower jaw of Semirostrum cerutti extends well past its upper jaw to form a prognathous projection, which was apparently well nourished by arteries.  This morphology is most similar to the mandibular morphology of skimmer birds, which fly low and close to the water while using their long and highly sensitive lower beaks to probe for underwater prey.  The authors argue that the properties of Semirostrum’s mandible suggest it did a similar thing in sediment at the bottom of the sea.

skimmer porpoise

A reconstruction of a ‘skimming’ Semirostrum and his joyous friend.  (From Racitot et al)

Evolving echolocation

Continuing on the whale-y theme, modern whales are split into two groups: the Odontoceti, or toothed whales, and the Mysticeti, or baleen whales.  The baleen whales filter feed small animals with their baleen, while the toothed whales (which include Semirostrum, who we just met) use echolocation to locate their larger prey, which involves emitting calls and listening to their echoes like a sort of biological sonar. These echolocating  vocalisations are associated with a unique array of features in odontocete skulls, that serve to amplify and  receive the sound.  The newly described Oligocene whale fossil Cotylocara macei is argued to possess these features, including dense snout bones argued to act as an acoustic reflector and a lot of room for the anchoring of a muscle associated with echolocation, the maxillonasolabialis (yep, apparently that’s a thing).  This brings the evolution of echolocation firmly down the odontocete stem, meaning that it evolved shortly after they diverged from mysticetes about 34-30 million years ago.

Whale phylo

If Cotylodira did echolocate, it suggests an origin where the arrow is pointing.  From Geisler et al.

Swimming sloths

As well as the familiar cetaceans, many other mammal groups have famously made the move to an aquatic life including manatees, seals and otters.  Common adaptations to this aquatic life are pachyostosis, the swelling of the solid outside layer of bone, and osteoschlerosis, the densification of bone, adaptations which are both argued to have evolved to reduce the animals buoyancy.   Were you to visit the Miocene-Plocene of Peru you might meet a less well-known aquatic mammal with these adaptations: the ground sloth genus, Thalassocnus.  While modern sloths seem happy to go for the occasional swim, this animal was adapted to an underwater life, and probably fed on marine vegetation.  A number of species of Thalassocnus existed throughout time, and Amson et al studied slices of their bones to track the evolution of pachyostosis and osteoschlerosis.  They found it could be tracked through the successive species as they increasingly adapted to aquatic life, offering a rare high-resolution view of the evolution of a trait, as well as further proof that sloths are awesome.

sloth bones

The ribs of Thalassocnus plotted onto a phylogeny, becoming denser as the genera adapted to marine life. The fact I put up this and resisted the urge to post one of the internet’s many sloth pictures is a testament to my dedication to palaeobiology and to you, dear reader. From Amson et al.

Pygmy Tyrannosaur

Another thing that’s awesome is, of course, dinosaurs, and we have two dinosaurs for your delectation and delight this week.  The first of these is a tyrannosaur, Nanuqsaurus hoglundi, the generic name (Nanuqsaurus) of which means ‘polar bear lizard’, surely one of the cooler (pun obvs intended) dinosaurian names.  This tyrannosaur was described last week from material found in Alaska, and defies the popular perception of tyrannosaurs as enormous carnivores by being relatively small.   As well as adding to our understanding of tyrannosaur diversity, this is particularly interesting as Alaskan members of another dinosaur genus, Troodon were found to be about 50% larger than their more southerly counterparts.  This was originally argued to be due to Troodon’s characteristically large eyes giving it a competitive advantage over other theropods in the low light conditions of the Arctic, selecting for larger body size.  The fact that Alaskan tyrannosaurs are, conversely, smaller is argued by the authors to add weight to this idea, with the claim that the opposite situation applied due to their diminished ability to see: a lowered competitive advantage resulted in selection for reduced size.

Pygmy

Size of Nanuqsaurus (A) compared to other tyrannosaurs (B-E, T. rex is B).  ‘Normal’ Troodon is F, with Alaskan Troodon as G.  From Fiorillo and Tykoski.

The ‘chicken from hell’

You’ve probably already heard of the second dinosaur that we encounter this week, the ‘chicken from hell’, Anzu wyliei.  Given that the generic name of the taxon is taken from an ancient Mesopotamian feathered demon (tbh, probably trumping polar bear lizard) one might question why it needs to be described as a ‘chicken from hell’, but hey ho.  Anzu is a new, and the most complete, member of the Caenagnathidae, members of the oviraptorsaurs like the more familiar Oviraptor. The Caenagnathidae contains taxa such as the massive Gigantoraptor, but so far is poorly known; Anzu goes some way to solving its relationships.   Like many other oviraptorsaurs it had a large, cassowary-like crest and no teeth; much debate has been had over exactly what dietary niche this group inhabited, and no firm answer has yet been reached.  Whatever its exact niche, Anzu is about 67million years old, and so it dates from immediately prior to the K/T mass extinction, and was found in the famous Hell’s Creek formation, showing that this locality still has information, and dinosaurs, to offer.

Screen Shot 2014-03-22 at 17.06.24

Anzu’s skeleton reconstructed. From Lamanna et al.

References

  • Racicot et al (2014) Unique feeding morphology in a new prognathous extinct porpoise from the Pliocene of California, Current Biology
  • Geisler et al (2014) A new fossil species supports an early origin for toothed whale echolocation, Nature
  • Amson et al (2014) Gradual adaptation of bone structure to aquatic lifestyle in extinct sloths from Peru, Proc. Roy. Soc. B
  • Fiorillo and Tykoski (2014) A diminutive new tyrannosaur from the top of the world, PLOS One
  • Lamanna et al (2014) A new large-bodied oviraptorsaurian theropod dinosaur from the latest Cretaceous of Western North America, PLOS One

What’s New(s) 7/04/2014: Definitely not just Torvosaurus

This week, the internet’s latched onto Torvosaurus and not let go. However, there’s been plenty more new palaeontological discoveries than a new European megacarnivore.

Torvosaurus gurneyi: Europe’s new heavyweight

If you haven’t heard about the new species of Torvosaurus that’s been discovered this week, then you’ve either been hiding under a rock, or you just simply hate dinosaurs. The news come from Portugal, after Hendrickx & Mateus redescribed bones initially thought to belong to the American species Torvosaurus tanneri. They name a new species, Torvosaurus gurneyi (named after James Gurney, artist of the wonderful Dinotopia series), distinct from T. tanneri based on numerous features including less teeth on the maxilla (for example). Dated to 157-145 Ma, T. gurneyi roamed the late Jurassic, and it would be hard to miss, considering size estimates settle around 33ft in length. Sure, it’s not T. rex, Spinosaurus or Giganotosaurus, but it does mean that T. gurneyi is the largest carniverous dinosaur discovered in Europe to date. So what does this all mean? Considering two species are now found on either side of the Atlantic, Hendrickx & Mateus hypothesise that some form of geographical barrier (such as geological uplift) separated multiple populations of Torvosaurus, and these (now completely separate) populations evolved to different local conditions (this idea is commonly termed vicariance).

Skeletal reconstruction of Torvosaurus gurneyi from Hendrickx & Mateus (2014).

Skeletal reconstruction of Torvosaurus gurneyi from Hendrickx & Mateus (2014).

Adipose fins no longer (of a) single (origin).

Far from it for me to encroach on Richard’s beloved fish, but this week new insight into adipose fins has shed some light on convergent evolution of fins (and vertebrate limbs more generally). You’re wondering what an adipose fin is, aren’t you? Go and look at the figure below.

Redundant caption is redundant.

Moving on, Stewart et al., using phylogenetic and anatomical evidence from over 600 species of fish concluded that the adipose fin, despite being widely regarded as vestigial with no clear/agreeable function, has been found to have evolved repeatedly and independently. Adipose fins have also evolved multiple features such as fin rays, which suggests that complexity and new types of tissue can evolve by activating certain developmental modules. Stewart et al. earmark this study as important to future work on the evolution of the limbs (and their complexity) in vertebrates. The study also challenges the long held notion that dermal skeleton evolved first, followed by the evolution of the endoskeleton. It also hints thats one may evolve without the other.

Daohugou, Jehol’s attractive older sibling

Yes, that was an unnecessarily creepy title. Moving on. The Jehol Biota, over in China is a lower Cretaceous ecosystem, represented by numerous localities (mainly of the exceptionally preserved lagerstatte variety). Jehol localities have given us a plethora of exceptionally preserved dinosaurs, pterosaurs, birds and mammals over the last 20 ish years. Recently, older deposits (Jurassic) from the same geographical region have been discovered. Sullivan et al. link the Daohugou locality to numerous other localities by the presence of a salamander, Chunerpeton tianyiensis, the key species that confirms the link of these localities to form the Daohugou biota. Much like in last week’s What’s New(s), with the discovery of a ‘new Burgess Shale’, this exceptionally preserved ecosystem has an incredible potential to provide vital information on the evolution of dinosaurs, birds, pterosaurs and mammals. The locality has already produced 13 well preserved pterosaurs (as well as five salamanders, two lizards, five dinosaurs, four mammals, oh, and a frog), so the future looks bright for Jehol’s older sibling.

Aforementioned salamaber. Also, dat preservation.

Aforementioned salamaber. Also, dat preservation.

Ocepeia: a very old afrotherian

The final two stories revolve around Cenozoic taxa, because it’s all too apparent that TDS is considerably lacking in Cenozoic palaeontological goodness. The first story centres around afrotherians, a superorder of mammals that have an African origin (including elephants, tenrecs, aardvarks, hyraxes and dugongs). The afrotherian in question is Ocepeia (O. grandis and O. daouiensis). A Ocepeia skull was discovered in the Selandian of Ouled Abdoun Basin (what a name) in Morocco. It dates to around 61 Ma, which immediately makes it the oldest afrotherian skull to ever be discovered. Now this is interesting, because this skull shows a mixture of primitive and derived features, as well as a mix of ungulate-like afrotherian (elephants, sea cows and hyraxes) and insectivore-like afrotherian (aardvarks, sengis, tenrecs and golden moles) features. This means that Ocepeia appears to be a ‘transitional form’ between these two subgroups of Afrotheria. This in turn provides significant evidence that Afrotheria may well have evolved specifically within Africa in the latest Cretaceous/early Tertiary. Pretty cool, for a mammal.

Reconstruction of Ocepeia from Gheerbrant et al. (2014).

Gastornis goes vegetarian for lent

Second in our short series of Cenozoic news is Gastornis. If you haven’t heard, Gastornis is a 2m tall terror bird which lived approximately 56-45 Ma (Paleocene-Eocene kinda time), that was previously thought to terrorise and eat small horse ancestors. This horse-heavy carniverous diet has been but into question for some time, and new evidence from Angst et al. suggests that whilst looking terrifying, only the plants of the Paleocene and Eocene had to worry about that enormous beak. Angst et al. form two lines of evidence, first they looked at carbon isotopes of bone apatite, and compared it to other herbivores (both mammals and birds). They found the results of this isotope analysis to be similar to the results gained from the other herbiverous taxa. Secondly, they look at (hypothetical) reconstructed jaw muscles of Gastornis, and again found that it shared similar looking jaw muscles to other herbiverous birds. Don’t worry Gastornis, you’re still scary to me (I mean your an almost 7 foot tall bird with a beak that looks like it can cut a man in half).

Don’t worry kids, science says these two are just playing and having fun.

 

References

Hendrickx C., Mateus O. (2014) Torvosaurus gurneyi n. sp., the Largest Terrestrial Predator from Europe, and a Proposed Terminology of the Maxilla Anatomy in Nonavian Theropods. PLoS ONE 9(3): e88905. doi:10.1371/journal.pone.0088905

Stewart, T. A. et al. (2014). The origins of adipose fins: an analysis of homoplasy and the serial homology of vertebrate appendages.Proceedings of the Royal Society B: Biological Sciences, 2014; 281 (1781): 20133120 DOI: 10.1098/rspb.2013.3120

Sullivan, C. et al. (2014). The vertebrates of the Jurassic Daohugou Biota of northeastern China. Journal of Vertebrate Paleontology 34 (2): 243 DOI:10.1080/02724634.2013.787316

Gheerbrant E. et al. (2014) Ocepeia (Middle Paleocene of Morocco): The Oldest Skull of an Afrotherian Mammal. PLoS ONE 9(2): e89739. doi:10.1371/journal.pone.0089739

Angst, D. et al. (2014). Isotopic and anatomical evidence of a herbiverous in the Early Tertiary giant bird Gastornis. Implications for the structure of Paleocene terrestrial ecosystems. Naturwissenschaften DOI 10.1007/s00114-014-1158-2

 

What’s new/s 03/03/14

What’s news has been neglected a bit over the last few weeks, but fear not! Here are five exciting palaeo news stories from the last month or so:

Placoderm faces

For no particularly good reason, placoderms are a group close to my heart.  This group of fish existed during the Devonian, and are the earliest example of vertebrate with jaws in the fossil record,  As well as being generally awesome, they are also crucial to understanding how gnathostomes, the jawed vertebrates, evolved from their jawless ancestors.  Dupret et al have CT imaged a primitive placoderm, Romundina, and have shown that it has a mixture of jawless fish (‘agnathan’) and gnathostome  cranial  characters.  As with so much of evolution, the transition to attaining jaws seems to have been piecemeal, part by part, an example of mosaic evolution, with cerebral proportions remaining largely unchanged with the evolution of jaws.

Romundina

Romundina in all its glory. This is the head with front end to the left, the large, round holes are the orbits. (from phys.org)

Even more Burgess Shale

The Cambrian is famous for the weird and wonderful fossil taxa that existed during it, and the most famous Cambrian fossil site is the Burgess Shale, in the Canadian Rockies.  Since the early 20th century the incredible preservation of this site has given us an invaluable window into life 500 million years ago.  While the Burgess Shale animals were famously argued by Stephen Jay Gould to represent experimentations in body plans alien to anything alive today, more recent work has shown that actually these animals are early relatives of groups such as arthropods (ie. insects, crustaceans etc) and vertebrates (ie. you).  The other week another site was described from the Burgess Shale; hopefully this will mean we’ll see lots of new Cambrian beasties over the next few years, as well as more information on known ones,  continuing to fill in our picture of early animal evolution.

Burgessnew

A range of weird and wonderful Cambrian fossils from the new assemblage. (from Caron et al)

Aquatic Acanthostega

We already met Acanthostega, the earliest known tetrapod, a few weeks ago, when we were looking at Tiktaalik and the transition of vertebrates onto land.   Acanthostega possesses a mixture of aquatic and terrestrial qualities: like a fish, it has gills and a tail fin, but like a modern tetrapod it had digits and a ‘neck’ between the head and body.  This has been taken to demonstrate that tetrapods actually evolve many ‘adaptations to land’, such as digits, while the still lived in water, in contrast to the historical view that a (presumably rather optimistic) fish crawled onto land and only then adapted to it. Recent work by Neenan et al suggests that Acanthostega’s jaw was adapted to aquatic, rather than terrestrial, feeding, which they argue refutes recent suggestions that it might have fed on land, or at least above water.

Optimistic fish

An optimistic fish (from Pixar.wikia.com)

Playing around with flight

Imagine, if you will, a bird.  Chances are that you’re imagining something that’s probably feathered and beaked*.  The fossil record, however, shows us that many traits that we associate with birds, such as feathers and beaks, evolved before birds came into existence as a group.  Feathers are perhaps the best example, found in many dinosaurs not particularly closely related to birds, but it is also true of various skeletal characters.  Work by Mark Puttick and others shows that this is the case with the comparatively long forelimbs of birds, which originated before the origins of the group, amongst earlier dinosaurs.  Gliding dinosaurs like Microraptor suggest that many groups were independently evolutionarily ‘playing around’ with feathered gliding, it was just the birds that happened to evolve powered flight and make it through to today.

*If not, you may want to double check that you know what a bird is.

Microraptor

Microraptor: Evolutionary experimentation with flight? (from nhm.co.uk)

Primitive live birth in ichthyosaurs

As we’ve seen before on The Dinosirs, ichthyosaurs were a very successful group of Mesozoic reptiles, highly adapted to an aquatic life.  One oft quoted adaptation viviparity, or live birth, as a fully aquatic amniote can’t get back onto land to lay eggs.  This is also seen in other groups of marine reptile, such as plesiosaurs and mosasaurs.  However, a recent paper by Motani and others has suggested that actually live birth was present in ichthyosaurs’ terrestrial ancestors before they became aquatic.  They argue this based on a fossil of a very early ichthyosaur, Chaohusaurus, which appears to have been fossilised giving birth.  While this is fairly common in ichthyosaur fossils, all previous fossils have been found giving birth to babies tail first as in modern day whales, possibly as an adaptation to prevent suffocation.  This fossil demonstrates that Chaohusaurus  gave birth head first, as in most terrestrial vertebrates.  Motani et al argue that this demonstrates that ichthyosaurs evolved from terrestrial viviparous ‘head first’ ancestors, only later switching round as an adaptation to marine life as in whales today.  This is contrary to the traditional view, but does fit with our picture of modern reptiles: many groups of lizard are viviparous.

Viviparity icthyo

Chaohusaurus.: green, red and blue below are the ribs, paddle and tail of the mother respectively. Small ichthyosaur can be seen com in out headfirst in yellow. (from Motani et al)

 

References

Dupret et al (2014) A primitive placoderms sheds light on the origin of the jawed vertebrate face, Nature

Caron et al (2014) A new phyllopod bed-like assemblage from the Burgess Shale of the Canadian Rockies, Nature communications

Neenan et al (2014) Feeding biomechanics in Acanthostega and across the fish-tetrapod transition, Proc. Roy. Soc. B

Puttick et al (2014) High rates of evolution preceded the origin of birds, Evolution

Motani et al (2014) Terrestrial origin of viviparity in Mesozoic marine reptiles indicated by Early Triassic embryonic fossils, PLOS One

What’s New(s) 31/01/14

So, only four days late putting this up.  I’ll save the things happening this week for Fridays post, but fear not! Plenty occurred in the paleontological world last week.  Some of it’s even non-Mesozoic (gasp!).

journal.pone.0084709.g020

Look at those ichthyosaurs go! Diversity remains roughly constant with the Jurassic throughout their Cretaceous range. From Fischer et al.

The last hurrah of the ichthyosaurs.  This group of iconic Mesozoic marine reptiles, who recently starred in TOTW, didn’t quite make it all the way to the K/T party, and went extinct during the late Cretaceous.  Traditionally the group has been seen as going out on a bit of a whimper after a lengthy decline from the Jurassic.  New work on European ichthyosaurs by Fischer et al has shown that this picture isn’t necessarily correct, with ichthyosaurs showing a pretty stable diversity throughout their existence, at least in Europe.

Screen Shot 2014-02-04 at 10.23.53

Polypterus having a breathe. From Graham et al.

Stem tetrapods can breathe easy with the news that Polypterus, a basal ray-finned fish, breathes air through its spiracles.   These large paired openings on its had have previously been argued to have a use in air breathing, but Graham et al have for the first time demonstrated this to actually be the case.  Stem tetrapods (the lineage of fish leading up to terrestrial vertebrates, including our friend Tiktaalik) possessed spiracles which have been linked to the transition to air breathing, and this work supports this argument.

Silesaur

Reconstruction of the size of NHMUK R16303 (grey) in comparison to a more normally sized silesaurid. From Barrett et al.

Giant Silesaurids!  Silesaurids are a group of Triassic archosaurs thought to be somewhere near the base of the dinosaur lineage, and so are important to understanding early dinosaur evolution.  Previously silesaurids have all been fairly small animals, particularly when compared to their later dinosaurian brethren.  Barrett et al have, however, described the femur of an unprecedentedly large silesaurid from Tanzania.  This specimen, with the catchy name NHMUK R16303, shows that silesaurids gained bigger sizes than previously thought, bigger than some early dinosaurs, with implications for ideas of why and how dinosaurs were so successful.

Penguinterrogation

The paper just has pictures of bits of broken femur in, so instead here’s a picture of a penguin undergoing what appears to be some kind of interview. From Wikipedia.

An ancient seabird has been described from the Palaeocene of New Zealand by Mayr and Scofield, and unlike everything else described from this locality it isn’t a penguin!  While I love penguins as much as the next man, this fleshes out the picture of the avian fauna of this area shortly after the K/T extinction.  It also continues to expand the picture of the diversity of birds in the Palaeocene, showing that the dinosaurs were still doing pretty well.  Extinct indeed.

800px-Fishfinger1

Apologies for the decline in picture usefulness through this post, but it was a either this or a complicated schematic of the action of Hox genes which I’d have done a poor job of explaining.   From Wikipedia.

Fish fingers. For a long time, scientists have been trying to reconcile the digits of tetrapods with fishes’ fins.  These two structures that are superficially similar, but frustratingly different in layout.  While fossil data has been building up a picture of this transition, ‘evo-devo’ studies have also been providing valuable information.  One such recent study, by Woltering et al, suggests that the digits of tetrapods aren’t in fact homologous (ie. evolutionarily the same) to the fin radials in a fishes’fin.  This is based upon the expression of Hox genes (genes that dictate the layout of a developing organ) in zebrafish and mice.  When Hox genes from the fish were expressed in developing mice, they only affected development in the proximal parts (ie. arm) of the limb, suggesting fish don’t use the ‘digit-causing’ part of their genetic toolkit.  This in turn suggests the two structures are not homologous.

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.

Bell_gigantism_Figure-1

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

What’s New(s): Unidirectional airflow, a load of hot air?

Whilst being old (last week’s) news, the discovery of unidirectional airflow in monitor lizards is:

  1. Really cool.
  2. Really important.
  3. Allows TDS to explain some key methods/principals used by palaeontologists.

Before we get bogged down in phylogentic-y goodness, let me introduce unidirectional airflow. As humans (and mammals more generally) we suck at breathing. Compared to birds, our respiratory system is pretty inefficient, but that’s fine, we’re not running around at full speed all day. Our breathing system is called tidal breathing, and involves the mixing of ‘new’ air and ‘old air’ in the lungs. This means that there’s not a huge amount of ‘fresh’ air in our lungs, meaning, compared to birds (and the like, more on that later) less oxygen enters the bloodstream per respiratory cycle. However birds have employ a neat trick called unidirectional airflow. Essentially, they’ve got a few more respiratory chambers which allows oxygen to enter the bloodstream during both inhalation and exhalation (by virtue of being a one-way system). This means a birds respiratory system are relatively efficient, which is great for them, as flying’s seriously hard work.

1.14355_MonitorLizard_Skeleton_edit

Unidirectional air flow, shown off excellently by our friend the Savannah monitor lizard.

Up until 2010, unidirectional airflow was only thought to exist in birds. But it has also been found in crocs (Farmer et al. 2010). So another scaly thing with a more efficienty respiratory system than us, big whoop. Yes actually, because with the help of Extant Phylogenetic Bracketing (EPB) we can learn a lot more about the success of diapsids (fancy name for the group containing all the birds, crocs, lizards, tuataras and oh, dinosaurs) during the Mesozoic.

Extant Phylogenetic Bracketing is essentially using common sense to infer anatomy and behaviour in extinct organisms. For something so widely used today, it’s only really been applied in palaeontology since 1995 (Witmer 1995). At it’s core we use our knowledge of what anatomical features (and possibly behaviour) modern organisms have, and put them into an evolutionary context to infer what features their common ancestors might have had. Birds, crocodiles and lizards are an excellent example of how palaeontologists have mastered EPB. So to use UA as an example, if we know birds have it, as do crocs, we can infer that dinosaurs may have had a UA respiratory system, because the last common ancestor of birds, dinosaurs and crocodiles (point A on the diagram below) may have had UA.

UA_phylotree

Very abridged (i.e no pterosaurs, sorry) of the diapsid tree (excluding Mesozoic marine reptiles). A is the last common ancestor of crocs and birds, B is the origin of birds, crocs, dinosaurs and lizards.

Cool story bro, but what about monitor lizards? Ok, so using EPB we’ve inferred that dinosaurs have UA due to their extant relatives both having UA. So if we now factor monitor lizards into the equation, we can now infer that the last common ancestor of birds, dinosaurs, crocs and lizards (i.e diapsids, point B on the diagram above) probably used unidirectional airflow as a respiratory strategy. This means that UA (originally thought to be unique to birds) originated 100 million years before birds evolved. But that’s not all.

1.14355_Image-1_5_SavannahMonitorLizard_CherylErtelt

Just another scaly thing with a more efficient respiratory system than us. All hail the savannah monitor lizard.

Lizards and Birds (and to a certain degree, crocs) are hugely successful organisms. A more efficient respiratory system has certainly aided in their almost global (niche) domination. This may explain why diapsids (dinosaurs in particular) were so diverse and successful during the Mesozoic (and also perhaps why they were so bloody big). So it looks like savannah monitor lizards are a…breath of fresh air.

References

Farmer, C. G. and Sanders, K. (2010). Unidirectional Airflow in the Lungs of Alligators. Science 327, 338–340.

Witmer, L. M. (1995). “The extant phylogenetic bracket and the importance of reconstructing soft tissues in fossils”, in Functional morphology in vertebrate paleontology (ed. J. J. Thomason), pp. 19–33. Cambridge University Press

Schachner, E. R. et al. (2013). Unidirectional pulmonary airflow patters in the savannah monitor lizard. Nature http://dx.doi.org/10.1038/nature12871

What’s New(s): Acheroraptor.

‘Whats New(s)’ is our new (poorly titled) news and views-esque section, where we keep you up-to-date on the latest findings in palaeontology, as well as explaining some key ideas behind them. For TDS first ever What’s New(s) we’ve got the exciting discovery of Acheroraptor! It also represents the first post on TDS with actual content (and dinosaurs). Huzzah!

New dinosaur fossils are being found all year round. No big deal, right? Wrong. Quite a lot of these new fossils fall under 3 very interesting categories:

  1. Crazy looking (a technical term).
  2. Exceptional preservation (and a shameless Bristol Palaeo plug).
  3. Macroevolutionary importance.
acheroraptor_fossil

Maxilla (top) and dentary (bottom) of Acheroraptor (with non-isolated teeth).

Acheroraptor falls into number 3. Not only does it have one of the best names ever, Acheroraptor temertyorum (literally meaning ‘Underworld thief’), but it’s one of the first major fossils (previously all we had was just isolated teeth) of dromaeosaurs (velociraptors and their close relatives) from North America in the Late Cretaceous. I say ‘major fossils’ but it’s still only 2 bones in the skull, a full maxilla and an almost complete dentary. Oh, and some non-isolated teeth. Nonetheless, the little blighter is (apparently, according to a wonderful reconstruction by Danielle Dufault) a cutie!

archeroraptor

As ‘underworld thieves’ go, this ones adorable.

So why is it important? Palaeontologists reconstruct evolutionary relationships by looking at how morphological features vary between different species. So, the more complete the fossil record is for a species, the more features you can compare, and the more confidence you can have when inferring the evolutionary relationship. So, going from a few isolated teeth, to a couple of (relatively) whopping great big skull bones is a fantastic leap! So, Acheroraptor has (despite being ‘American‘) been found to be more closely related to Asian dromaeosaurs, such as Velociraptor mongoliensis. This means that there was more faunal interchange between ‘America’ and ‘Asia’ back in the Late Cretaceous.

Cool right?

References

Evans, D. C., Larson, D. W. and Currie, P. J. (2013) A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from the latest Cretaceous of North America, Naturwissenschaften, 100(11), 1041-1049