EGU Blogs


The early evolution of birds – more complicated than trying to untangle your headphones..

Birds are a phenomenal story of evolutionary success. As modern-day dinosaur descendants, they occupy almost all environments and ecosystems around the globe, and are truly animals that capture our imaginations. However, how did they become so diverse, both in number and form? This is something only the fossil record can divine for us.

Birds first appear in the Middle to Late Jurassic of China and latest Jurassic of Europe (hello, Archaeopteryx), around 160-150 million years ago. Their first radiation, in terms of increasing species numbers, appears to have occurred in the Early Cretaceous of China, based on the fossil graveyards of the 125 million year old Jehol Biota. However, it has been argued that the timing of this radiation is strongly influenced by ‘the Lagersttäten effect’ – that is, periods of exceptional preservation in the fossil record. For the early evolution of birds, this is complicated by the fact that the earliest Cretaceous (around 145 to 125 million years ago) fossil record of birds is known from only rare and fragmentary material.

One of the earliest known birds, Archaeopteryx, from the infamous Solnhofen beds of Bavaria, Germany. (source)

One of the earliest known birds, Archaeopteryx, from the infamous Solnhofen beds of Bavaria, Germany. (source)

At some time around then, however, it is though that birds underwent a phase of rapid diversification of body forms, particularly geared towards increasingly small body sizes. This has important implications for the evolution of flight, but that’s another story.

A possible trigger for this diversification might have been with an extinction event at the end of the Jurassic, 145 million years ago, which saw the decimation of smaller-sized pterosaurs (their non-dinosaurian, winged cousins), particularly those known as rhamphorhynchids. Ecologically speaking, this would have opened up ‘ecospace’, for other animals to radiate into and occupy. Animals, such as birds.

What you would expect to see if this is the case, is increasing diversity of birds, which we do see, as well as increasing diversity of their body forms, their morphology, and ecological variants.

Were pterosaurs duking it out against birds for millions of years? (source)

Were pterosaurs duking it out against birds for millions of years? (source)

However, is this what we the fossils record for us? A recent study has shown that, despite the high diversity represented by the Jehol Biota, we actually see constrained levels of morphological diversity – known as disparity.

Much of the Jehol bird fauna seems to have been comprised of ground foragers, which is curious as they would all have been flight capable. Interestingly, this seems to be at odds with the local pterosaur fauna. These chaps were still owning the skies, and diversifying into an increasingly bizarre suite of forms.

Could it be, perhaps, that there was a sort of ‘fight for the skies’ happening at this time? Perhaps while both pterosaurs and birds radiating, they were competing to constrain the extent to which the others could evolve, and restricted them to particular ecologies. This hypothesis is certainly appealing, and tells of a sort of ‘fight for the skies’ in the early origin of birds.

Understanding why this was happening, and which roles birds were most successful in, is important for understanding their survival through the end-Cretaceous mass extinction and the demise of non-avian dinosaurs, as well as their rise to fame in modern times.


Mitchell, J. S. and Makovicky, P. J. (2014) Low ecological disparity in Early Cretaceous birds, Proceedings of the Royal Society, Series B: Biological Sciences, 281, 20140608. (link)

How fast was the demise of the dinosaurs?

How fast was the demise of the dinosaurs?

It’s dark. It’s always dark these days. Lights in the sky burn your eyes, so you keep your face to ground in the hopes that they’ll go away. But they don’t. The air is heavy. Heavy with poisons that make it difficult to breathe. Heavy with foreboding dread.

You, my unfortunate friend, are going through a mass extinction!

There have been five periods of mass extinction in the past. These represent major phases in the history of life where we see global reorganisations of ecosystems and their inhabitants.

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Top 10 dinosaur facts!

For those of you who may not have been aware, I was fortunate enough to recently publish a dinosaur book for kids, complete with build-it-yourself pop-out dinosaurs. I’ve recently published an article in The Guardian about it, which features much of the great artwork by Vladimir Nikolov. It’s all about some of the perhaps less well-known dinosaur facts that feature in the book, so enjoy!

IPC Day 2 – The evolution of giants

This is a slightly delayed summary of the sauropod symposium on day 2 of IPC4, following sessions the previous day on vertebrate taphonomy and diversity and extinction in the fossil record. This is also the final of these little summaries, and for that I apologise – my laptop is a bit kaput atm, and needs power sockets to run and which were not available in some of the rooms. I might be a little cheeky and ask a couple of the attendees to write personal summaries for here, but we’ll have to wait and see! Make sure you’re keeping a check on Palaeocast too, as Dave has been reporting non-stop from the conference.

On to sauropods, those giants of the Mesozoic!

Martin Sander launched right into the meat of things discussing the latest advances in trying to understand the physiology of gigantism in sauropods. A large team of researchers have been working on a cascade model of evolution featuring traits, selective advantages and feedback loops that lead to increasing body size in sauropods.

John Frominos switched modes completely to his investigation of the comparative function of vertebrae between sauropods and crocodylians. It seems that generally, concavo-convex vertebrae in crocs don’t offer much advantage in terms of flexibility, so the same may be true for sauropods. This talk was of particular interest for me, as atoposaurid crocs are some of the first crocodyliforms (early non-crown group crocs) to have procoelous vertebrae (with a convex front edge and concave back edge).

Jorge Calvo filled in with a replacement talk to describe some new remains of Futalognkosaurus from the Late Cretaceous of Argentina. Turns out it’s just a really cool, massive dinosaur, and among one of the largest and most well-known of sauropods.

Bernardo J. González Riga described new sauropod remains from Mendoza Province, and new information on the evolution of the sauropod pes (foot). Two new titanosaur species with unusual characteristics of their feet were mentioned, which is great as it sheds light on the evolution of locomotion in these big boys. Bernardo was also cool enough to take us to his lab to see the amazing new specimens, and provide wine and empanadas, so on the off chance that he reads this – thanks Bernardo and everyone else!

One of the leg bones of one of the new dinosaurs! A very humerus photo.

One of the leg bones of one of the new dinosaurs! A very humerus photo.

Matthew Lamanna, one of the chaps involved in the recent discovery of Dreadnoughtous, described some new Moroccan sauropods, and their implications for sauropod ecology and diversity in Africa. He provided the first evidence for theropods preying on sauropods, which is great as the large theropod fauna of North Africa, including Spinosaurus, were usually thought to have fed on a range of fish. Through detailed anatomical investigations, he also provided evidence for allopatric speciation in North African sauropods, at a time when the region was cut by a large epicontinental sea.

Kristi Curry-Rogers revealed to us new sauropods from Madagascar, as well as details on their evolution, ecology, and palaeobiology. One of the coolest findings was a giant hollow osteoderm, possibly used as a mineral reserve similar to modern camels! She announced the discovery of lots of new fossil sites, so the future of Madagascaran dinosaur discoveries should be exciting in the future.

Philip Mannion, my PhD supervisor, launched into a comprehensive new phylogeny of Jurassic-Cretaceous Gondwanan sauropods. Phil has been conducting first hand taxonomic revision of many old and new species around the world, and has built a new tree that paves the way for new biogeographic  and macroevolutionary analyses.

Jeffrey Wilson described a wonderful new skull of the titanosaur Tapuiasaurus that provides insights into their feeding behaviour. This is one of the few known titanosaur skulls, and shows some unusual features including a tooth wear pattern similar to heterodontosaurs (early ornithischian dinosaurs), and the animal may have even had a keratinous beak.

Diego Pol finished the session off by discussing faunal replacement in Jurassic sauropods. I didn’t catch the details on this though, as the session was running late and I had to dash to go and present my poster on the evolution and diversity of atoposaurid crocodyliforms! More on that once I’m back and have had time to recover though, although check out my recent PeerJ paper that describes a lot of what we presented.

So there we have it, still lots going on and plenty to discover about the biggest animals to ever walk the Earth! If you’d like to know more, leave a comment, or get in touch with one of the authors.