Green Tea and Velociraptors

Green Tea and Velociraptors

They might be giants, but how could they live with each other?

Sauropod dinosaurs are the biggest animals to have ever walked on land. They are instantly recognised by their long, sweeping necks and whiplashed tails, and nearly always portrayed moving in herds, being stalked by hungry predators.

In recent years, a huge amount of taxonomic effort from scientists has vastly increased the number of known species of sauropod. What we now know is that in many areas we had two or more species co-existing alongside each other.

A question that arises from this, is how did we have animals that seem so similar, and with such high energy and dietary requirements, living alongside one another? Was there some sort of spinach-like super plant that gave them all Popeye-like physical boosts, or something more subtle…?

Camarasaurus

Hi there, Camarasaurus! One of the iconic dinosaurs of the Morrison Formation (source)

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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.

Reference

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)

Palaeontology in the 21st Century

Palaeontology is the study of the history of life on Earth. Whenever I get asked what I do, my answer always gets a predictable response: either “Oh, like Ross from Friends?” “So Jurassic Park?” or “So you dig dinosaurs?”

Neither of these are close to what myself, my colleagues, or the broader field are doing. Well, apart from the digging dinos. We have to have some perks (not that I’ve actually ever been on a dig…).

What I want to highlight are a couple of recent developments in the field that show that palaeontology is just as technically advanced as any other major domain of science out there. They both involve the genesis and analysis of large data sets that we’re constantly using to test large-scale patterns and processes through time – known as macroevolution. Trying to decipher the patterns and processes of evolution leading towards the modern, extant fauna we have today is key in predicting their future as we destroy the planet.

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A letter to the Editor of the Zoological Journal of the Linnean Society

This post is one inspired by the actions of Ethan White and a couple of other ecologists. Spurred on by their actions, I decided to write a letter to the Editor of a major journal in my field, the Zoological Journal of the Linnean Society. Ethan has performed similar actions too, and this letter draws quite a bit on what he has previously written. The theme revolves around requesting that the Linnean Socciety journals allow submission of manuscripts that have been previously published as a preprint (a non-peer-reviewed version of a manuscript), as the present policy is not supportive of open research and the rapid and free dissemination of research. Anyway, here’s the letter: [Read More]

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