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Jon Tennant

Jon began university life as a geologist, followed by a treacherous leap into the life sciences. He spent several years at Imperial College London, investigating the extinction and biodiversity patterns of Mesozoic tetrapods – anything with four legs or flippers – to discover whether or not there is evidence for a ‘hidden’ mass extinction 145 million years ago. Alongside this, Jon researched the origins and evolution of ‘dwarf’ crocodiles called atoposaurids. Prior to this, there was a brief interlude were Jon was immersed in the world of science policy and communication, which greatly shaped his views on the broader role that science can play, and in particular, the current ‘open’ debate. Jon tragically passed away in 2020.

The origin of a second wave of supreme-swimming crocodiles

January 5, 2015
The origin of a second wave of supreme-swimming crocodiles
The skull of Pholidosaurus purbeckensis from the UK. (Source)

Millions of years ago, crocodiles were far more diverse (and weird) than the ones we still have around today. They ranged from armoured, tank-like forms living on land and feeding on plants, to 9 metre long fully-fledged swimmers out in the open oceans.

In the Jurassic period, most of the crocs we know of were of this second kind, the whole marine forms. These comprised a group known as thalattosuchians, and they had long snouts for snapping up fish, salt glands, and even flipper-like arms and legs adapted for a swimming lifestyle. Let’s just call them fish-crocs for now.

These fish-crocs, although supreme hunters and generally awesome, went extinct at some point in the early Cretaceous, about 120 million years ago. The reasons for this are unknown, but it could be due to unfavourable environmental conditions, or perhaps they were out competed by other marine super-predators such as pliosaurs. It was a sad time for croc-kind.

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Twitter logos for conference talks

January 4, 2015

Recently, there was a pretty massive discussion about the practice of live-tweeting at conference talk hosted on this blog. While the discussion is by no means over, or particularly conclusive, one idea to emerge was having an icon of some sort on slides during talks to indicate whether or not they could be live-tweeted. Sarah Werning has been kind enough to create and share some logos following this, and I strongly encourage academics to use these when presenting to avoid any future confusion or conflict over this. It only takes an extra couple of minutes to ‘twitter-proof’ a presentation. Of course, you can simply ask at the beginning for your audience not to tweet, rather than plastering these on every slide, if that’s how you choose to roll.

Dwarf crocodiles are the cutest, even if they’ve been dead for 150 million years..

December 27, 2014
Dwarf crocodiles are the cutest, even if they’ve been dead for 150 million years..

Europe 150 million years ago must have been a brilliant place to go on holiday. Tropical islands, warm lagoons to bathe, a warm climate, and nine metre long crocodiles noshing on anything that couldn’t swim fast enough. Ok, so maybe not that great for humans, but if you were an ancient archosaur, living alongside dinosaurs and other now extinct animals, life must have been pretty sweet.

These giant crocodiles were known as metriorhynchids, and were fully adapted to swim in the seas. Living alongside them, though, were smaller but by no means less impressive crocodiles known as atoposaurids. These are the cute little, but unfortunately extinct, guys I’ve been studying as part of my PhD for the last couple of years, and they are some of the best preserved fossil crocodiles we’ve got.

Alligatorellus bavaricus, newly named from Bavaria, Germany. Tennant and Mannion (2014)

Alligatorellus bavaricus, newly named from Bavaria, Germany. Tennant and Mannion (2014)

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Minerals and the search for life on Mars

December 8, 2014

This was originally posted on James Lewis’ personal blog at:
 http://marsblogger.wordpress.com/2014/12/08/minerals-and-the-search-for-life-on-mars/

(Re-posted with permission)

Understanding if life could ever have existed on Mars is one of the most challenging scientific questions facing us in the 21st Century. We know that the Martian surface at present is an arid environment bombarded with ultraviolet radiation, so the chance of finding living organisms existing there today is extremely unlikely. However, Mars has not always been this way, its history is divided into three distinct geological periods; the Amazonian, Hesperian, and the Noachian. The oldest of these, the Noachian, is likely to have been a significantly more promising time for life to potentially evolve as liquid water persisted on or near the surface long enough to carve valleys into the Martian surface and leave behind distinctive rock units. For example, in Gale Crater Curiosity Rover discovered minerals that indicated the presence of a freshwater lake at the time of their formation billions of years ago, an environment favourable to life or at least life as we understand it on Earth.

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