Guest Post: The tyrants head south

Today Roger Benson guests on the Musings as he brings us news of the first tyrannosaur from Australia, or indeed any southern hemisphere continent. Take it away:

Tyrannosaurid dinosaurs are iconic, giant predators from around 85-65 million years ago. They lived in the Late Cretaceous of North America and Asia and were wiped out be the mass extinction that marked the end of the ‘Age of Dinosaurs’. After the discovery of Tyrannosaurus rex and close relatives in the early 20th century, for a long time, this is all we knew.

In the past 5–10 year, palaeontologists have been filling the gaps in the long early history of tyrannosaurs. They are now known as early as 170 million years ago (Middle Jurassic). Early tyrannosauroids were somewhat different to the Late Cretaceous giants. They are almost all the same size, or smaller than a man, and they generally have light skulls and long arms compared to T. rex. We know from Dilong (Early Cretaceous, China) that some at least had filamentous integument called ‘protofeathers’. Guanlong and Proceratosaurus from the Jurassic of England and China tell us that some had striking bony head crests. Raptorex, a Chinese tyrannosauroid reported last year in Science, shows us that the robust skulls and short arms of T. rex appeared in the Lower Cretaceous among fairly small (~80 kg) animals.

But a piece of the puzzle has been missing. All tyrannosauroids thus far have been discovered in the Northern Hemisphere. This is odd, as most long-lived dinosaur clades (tyrannosaurs spanned at least 100 million years) made it across the globe. Early in dinosaur history the continents were assembled into a single supercontinent, so this was easily possible. But perhaps tyrannosauroids never made it.

The new pubis. Image courtesy of Roger Benson.

Today, myself and colleagues reported a new specimen from 110 million year old rocks at Dinosaur Cove Australia, representing the first evidence that tyrannosauroids made it into the Southern hemisphere. The animal is estimated at 3 metres long and a weight of 80 kg, similar to a man based on comparison with the similarly-sized tyrannosaur Raptorex. The fossil is a single pubic bone (from the hips), recovered in 1989 during an expedition funded by National Geographic and the Australian Research Council, and led by Tom Rich at the Museum Victoria, Melbourne. Tom and his team blasted into the rocks at Dinosaur Cove using heavy equipment provided gratis by Atlas Copco, and explosives. They effectively created a ‘fossil mine’, from which hundreds of isolated bones were recovered. Most of these were difficult to identify definitively, but they have provided evidence of a range of dinosaur groups, including megaraptoran allosauroids, oviraptorosaurs, hypsilophodontids, and now tyrannosauroids.

With the tyrannosauroid pubis we got lucky. Tyrannosauroids have distinctive pubes showing coelurosaurian features such as a transversely narrow distal expansion (called the pubic boot). In tyrannosaurs the boot is especially large and, in tyrannosaurids there is a flange-like pubic tubercle. The identification isn’t just based on these features though. In fact, in almost every respect, our specimen is identical to the pubis of a derived tyrannosaurid like Albertosaurus. To show this as clearly as possible included a picture the two next to each other in our paper (thanks to Lara Shychoski for providing a photo of a tyrannosaurid pubis).The dig that yielded the new specimen. Image courtesy of Roger Benson.

We believe that our specimen show that, 110 million years ago, in the middle of its history, the tyrannosaur lineage was globally-distributed. This raises a question. Why then did tyrannosaurs grow to giant size late in dinosaur history in the north, but fade into obscurity in the south, where the apex predator mantle was taken up by other dinosaur groups? Only future discoveries can reveal the details of the radiation of southern tyrannosaurs.

Benson, R. B. J., Barrett, P. M., Rich, T. H. & Vickers-Rich, P. 2010. A southern tyrant reptile. Science 327, 1613.

17 Responses to “Guest Post: The tyrants head south”

  1. 1 Thomas R. Holtz, Jr. 26/03/2010 at 8:39 pm

    Congrats on the new discover, and once again (after my posts to FB & TetZoo) I want to publicly thank you and your team for the courage to not name a single-bone specimen!

    Now we need people to find the microsites of later Early Cretaceous Australia and start sorting some teeth!

    • 2 David Hone 26/03/2010 at 9:17 pm

      Well and India, Africa and South Anerica too Tom. Oli Rauhut went over it not too long ago, but there’s a bunch of barely sorted stuff from Tendaguru you can start on.

      • 3 Bob Strauss 26/03/2010 at 9:32 pm

        Oh, c’mon, can’t you name it? The kids who visit my site love names.

        How about a contest, the way they did with Dracorex?

      • 4 David Hone 27/03/2010 at 8:26 am

        But Bob that only works is there is good reason to identify it as new. Sure it is likely to be new given it’s location, but it has all the characteristics we see in other tyrannosaurs and noting unique. Thus naming it just adds a meaningless name to the files that confuses things, not clarifies them.

        Hopefully more, and diagnostic, material will emerge and then we can put a name to it. A partial skull, or some vertebrae or an arm will be out there and now we know that we’re looking for a tyrant, it should be easier to find it.

  2. 5 Allen Hazen 28/03/2010 at 6:23 am

    Didn’t Atlas-Copco’s donation of equipment get honored in the name of a taxon, “Atlascopcosaurus”? (To my ear a more interesting name than the recent “Fedexia”!)

    • 6 Bob Strauss 28/03/2010 at 7:24 am

      And let’s not forget Qantassaurus, after Qantas Airlines. Maybe corporate naming of dinosaurs will be the next big trend. (Speaking of which, anyone know any others? I had no idea about Atlascopcosaurus.)

      • 7 rorschachhamster 05/04/2010 at 10:39 pm

        Funny thought: Scientific classification most likely will survive all this corporations. To some future palaeontologists this names will be probably as meaningless as the most greek names to me.

      • 8 David Hone 06/04/2010 at 7:10 am

        Quite possibly, though it doesn’t stop it annoying me now. 😉

      • 9 Rob Schnautz 26/07/2010 at 8:12 am

        There would have been Mindarus ebayi, after the site where the fossil was discovered, but apparently commercial names were discouraged at the time, and it was named Mindarus harringtoni instead.

  3. 10 Jerry D. Harris 28/03/2010 at 11:52 pm

    I’ve always been surprised that paleontologists haven’t actively pursued beer brewers for funding (or, at least, free beer during field season!) in exchange for names…who knows when we’ll see Budweiseria, Samadamssaurus, or Fattiraptor…?

    • 11 David Hone 29/03/2010 at 8:43 am

      I must say I’ve never been fond of things named after companies. (Not sure if that’s just a beer-related joke or not Jerry). OK, if someone does help you out and you want to say thanks, well OK I guess, but you dear hear too many stories of “I’ll name something after you if you give us XXXX dollars, or let us dig here” and I can’t help but think this is a corruption of one of the last romantic bits of palaeo where one can really celebrate a colleague or pay tribute to people or just the taxon itself. My 2c at least.

  4. 15 SuperRaptor 01/04/2010 at 2:49 am

    Very, very exciting news. I’ve always suspected that tyrants lived down there. After all, they evolved before Pangaea had entirely split apart. But this finally proves it! I applaud the team for not naming non-diagnostic material…. Yes, I’m talking to you, Santanaraptor.

  1. 1 A Tyrannosaur From Down Under? | Dinosaur Tracking Trackback on 29/03/2010 at 9:58 pm
  2. 2 What can you do with a fragment? « Dave Hone's Archosaur Musings Trackback on 27/03/2011 at 12:14 pm
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