Friday, December 17, 2010

Mamma mia, è un dinosauro!

It is Christmastime, which means it is time for me to make my annual pilgrimage to my favourite 13th-Century-Castle-that-is-also-a-Palaeontological-Museum in lovely Lerici, Italy.

Enter the Cortile dei Dinosauri to meet some friends from the Jurassic and Triassic.

A family of cynodonts relaxes on the sand.

Scutosaurus gives you the once over.

And my small thyreophoran friend Scutellosaurus steps hesitantly behind a sauropod.

The interior of the museum is also quite nice, and features many footprints from the area around Lerici. There's also a pretty nice selection of invertebrate fossils from around the world.

I feel strongly that I need to make this into a t-shirt.

You can read more about the dinosaurs of Italy in the book...the Dinosaurs of Italy, by Cristiano Dal Sasso. It is a very readable book geared to a lay audience and has wonderful information about Ciro, the remarkably well-preserved small theropod Scipionyx, and Antonio, the newly-named hadrosaur Tethyshadros.

Dal Sasso C, Signore M. 1998. Exceptional soft-tissue preservation in a theropod dinosaur from Italy. Nature 392: 383-387.

Dalla Vecchia FM. 2009. Tethyshadros insularis, a new hadrosauroid dinosaur (Ornithischia) from the Upper Cretaceous of Italy. Journal of Vertebrate Paleontology 29:1100-1116.

And for more information on dinosaur footprints from Lerici, check out:
Nicosia U and Loi M. 2003. Triassic footprints from Lerici (La Spezia, Northern Italy). Ichnos 10:127-140.

Wednesday, December 15, 2010

Tuesday, December 7, 2010

5 Questions for Tetsuto Miyashita

Well folks, you get two mini-interviews back to back this week! My friend and colleague Tetsuto Miyashita is a Masters student at the University of Alberta and recently published a new paper on a very interesting specimen of the tyrannosaurid dinosaur Daspletosaurus:

Miyashita T, Tanke DH, Currie PJ. 2010. Variation in premaxillary tooth count and a developmental abnormality in a tyrannosaurid dinosaur. Acta Palaeontologica Polonica 55: 635-643. APP is an open access journal, so you can download the article for free!

Tetsuto measures a little Tarbosaurus at the Paleontological Institute in Moscow.

1. What inspired you to conduct this study?

When I visited Tyrrell in 2007, my co-author Darren Tanke dropped a tyrannosaur premaxilla on my lap and quizzed me: "What's wrong with this specimen?" It's got only three tooth sockets, whereas almost all theropods, including all tyrannosaurids, have four. I started wondering what could mess up such a conservative trait.

2. Why is it important to consider development when studying fossils?

If you have two different species in front of you and wonder where the differences come from, you will find an answer in development. In other words, a sequence of evolutionary transformations are a history of modifications in developmental processes. Evidence is hard to find -- you can never visualize expression of genes in fossils. You rely on inferences, or simply speculate. But developmental interpretations based on morphology are arguably the most powerful voice in the narrative of evolution, because they explain how a diversity that we see in fossils and living forms was generated.

3. Did this particular individual have enormous teeth?

Yes. The tooth sockets are 25% larger than you expect for a normal tyrannosaurid. The teeth must have been larger accordingly. It is a trade off -- you reduce the number of teeth and create a space to accommodate larger teeth.

4. How do your findings affect using tooth count as a character in phylogenetic analyses?

Two parameters affect a tooth count: space in which teeth fit in and sizes of the teeth. So, rather than simply counting teeth (which is problematic for reasons below), why not measure variation in the two parameters? When you formulate a character simply on tooth count, you have to break up often continuous variation into a few discrete states. No matter how you break it up, justifying this is difficult. On top of that, when two factors are in play, it is more to the point to treat them separately.

5. Which is the better of the two Dinosaur Provincial Park tyrannosaurids, Gorgosaurus or Daspletosaurus?

Daspletosaurus: the rarer, the more massive, and the longer forgotten. But there is an indestructible Japanese cartoon character -- Gorgo 13. For the sake of Mr. Gorgo 13, I wish Gorgosaurus was more of a match for Daspletosaurus.

(Shamelessly stolen from Wikipedia.)

Thanks, Tetsuto! Now go find the matching premaxilla to that specimen so you can tell us all about asymmetry.

Monday, December 6, 2010

5 Questions for Scott Persons

A few weeks ago my friend and colleague Scott Persons published his first ever paper, detailing the results of the first phase of his Masters research at the University of Alberta. The paper received a fair amount of media and blog attention, but I demand attention as well, so here is a mini-interview with Scott  about the paper.

(But before we get started, you should check out Scott on Daily Planet, a very popular science variety show on Discovery Canada that I was shocked to learn is not carried by the American Discovery Channel. Tragedy!)
(Sadly, the frozen dissected lizard did not make the final cut for the segment.) 

1. What inspired you to conduct this study?

The inspiration to do a project on theropod tails came the summer before I began grad school in Edmonton. I was working at the Paleon Museum in Glenrock, Wyoming, and helping to put together a display case on the predatory dinosaurs of the Morrison Formation. Included in the display were two tail vertebrae. One from an Allosaurus and one from a Torvosaurus . . . and they looked really different! (For those of you interested, one major difference is the angle of the caudal ribs. In Torvosaurus the caudal ribs are strongly angled backwards, while the caudal ribs of Allosaurus are nearly perpendicular to the neural spines.) I asked the curator, Shawn Smith, about the differences, and he told me that no one really understood the functional significances. So, that got me thinking about tails, and this study was only the first part of a much larger project investigating theropod tail morphology and function.

2. What are some of your favourite Tyrannosaurus reconstructions?

That’s hard. T. rex is the most commonly depicted dinosaur, and a lot of paleo artists, from Charles Knight to James Gurney, have given us their renditions. Two of my favorites are John Gurche’s illustration of Sue and Michael Skrepnick’s “The ‘King’ prepares to defend his meal” (I’m not sure that’s the proper title). Not only do these depictions get the anatomy right (for the most part), but they succeed in conveying a visceral sense of power and menace. Recently, my favorite is Scott Hartman’s depiction of Stan, because it was created in collaboration with my study and really shows off the beefiness of the tail.

(Scott Hartman's excellent drawing can also be seen in Persons and Currie 2010 --Victoria)

3. Could Tyrannosaurus outrun the Jeep in Jurassic Park?

Well, that depends on how fast you think the Jeep was going. John Hutchinson and Stephen Gatesy have watched this cinematic sequence closely, and they concluded that the Jeep was traveling at over 40 mph (64 kph). No, I don’t think T. rex could go that fast.

But Jurassic Park was actually pretty specific about the T. rex’s intended top speed. Early in the film Richard Attenborough says to Sam Neill “Well, we’ve clocked the T. rex at 32 miles per hour.” Could a Tyrannosaurus do 32 mph (51.5 kph)? That would be about twice as fast as a modern elephant, but not much faster than a black rhinoceros (although maximum rhino speeds are hotly debated). I think it’s important to emphasize that my study only provides one of the many pieces of evidence needed to answer this question, and I think a lot of those pieces are still missing.

However, if we want to force the issue, and if I had to place a bet at the Dino Derby, I’d bet on “yes”. But (just to hedge my bet) the T. rex that I’d enter in the race would be a sub-adult. Young tyrannosaurs were lighter and had proportionately longer shins, so they were probably significantly faster than the bulkier adults.

4. How does this relate to the idea that Tyrannosaurus rex was a scavenger rather than a predator? This is an important and timely debate.

Your sarcasm is well founded. The scavenger vs. predator debate has largely been perpetuated by paleontologist Jack Horner, who is a vocal advocate for the scavenger hypothesis. But, in his book The Complete T. rex, Horner wrote “I’m not convinced T.rex was only scavenger, though I will say so sometimes just to be contrary and to get my colleagues arguing.” – p. 218. Add to this the recent discovery of hadrosaur tail vertebrae with healed tyrannosaur bite wounds, and it’s safe to say the debate over whether T. rex was purely a scavenger is basically over (if, indeed, it ever really existed).

But, if we let ourselves be provoked by this contrarian notion, the tail study’s results are relevant. If Tyrannosaurus was a scavenger, then the big theropod wouldn’t need a large M. caudofemoralis, because it doesn’t take much athleticism to catch a rotting corpse, and a slowpoke T. rex would have been poorly adapted to chase after live prey. So, if Tyrannosaurus had a small M. caudofemoralis and was incapable of rapid locomotion, this would support the scavenger hypothesis. As it turns out, T. rex had what it took to chase and catch dinosaurs like ceratopsians (the horned dinosaurs) and hadrosaurs (the duckbilled dinosaurs) while they were still alive.

[Note from Victoria: I myself have no problem with speculating on the feeding strategies of Tyrannosaurus. However, I knew that this would be what many media sources would jump on with regards to Scott's paper, even though it is not the most interesting aspect of the study, and was correct. So there.]

5. Will it blend?

As demonstrated by Dickson et al. (2007), everything blends . . . except Chuck Norris.

Lastly, Victoria, in case your readers aren’t aware, I’d like to point out how helpful and important your work on ankylosaur tails was to this study. The theropod tail project has built directly on the caudal muscle classification scheme outlined in your 2009 paper in PLoS One.

Well Scott, with that you can occupy the same office as me for the next few weeks at least, I'd say.

You can find Scott's paper online here (PDF not available just yet though, I'm afraid). Scott also did a great guest post over at Dave Hone's Archosaur Musings which is well worth a read.
And finally, Pete would like me to point out the amusing list of results if you google 'scott persons tyrannosaur'.

Friday, December 3, 2010

In search of Cryolophosaurus.

Today my supervisor Dr. Philip Currie and his research associate and wife Dr. Eva Koppelhus embark on a two-month expedition to Antarctica as part of the larger Transantarctic Vertebrate Paleontology Project. And just what the heck are they looking for all the way down there?

This dude:

(Image by my very talented friend and colleague Robin Sissons!)

This is Cryolophosaurus ellioti, the Frozen Crested Lizard. It's an important animal for a couple of reasons: 1) it's weird, 2) it's old, and 3) it's cold. It is one of just a handful of dinosaurs known from the continent and as such it's a pretty important animal biogeographically speaking. Antarctica was not exactly warm during the Jurassic, but it was actually pretty close to its current position over the south pole and would have had extended periods of darkness and potentially cool winters. It is also from a poorly-sampled age in the evolution of theropods, the Early Jurassic, and so it can help us understand early theropod evolution.

Cryolophosaurus also has some pretty interesting anatomical features, the most notable of which is the transverse crest on the top of the skull. The crest is formed of the lacrimal and nasal bones. Cryolophosaurus is very large considering that it is Early Jurassic in age - it is of comparable size to some of the largest Ceratosaurus specimens from the Late Jurassic. A recent phylogenetic analysis showed that Cryolophosaurus is found in a clade of medium-sized Early Jurassic theropods that includes Dilophosaurus wetherilli, 'Dilophosaurus' sinensis, and Dracovenator.

You can keep up with the expedition via the Field Museum Expeditions website, which will have more information in the coming days - click on the box next to "Pete Mackovicky and Nate Smith - Dinosaurs in Antarctica" near the bottom of the map.

Update: The expedition website is now up. There is a stunning amount of resources on the website, so I'd highly recommend checking out expeditions@fieldmuseum - Beardmore Glacial Region, Antarctica.

Hammer WR, Hickerson WJ. 1994. A crested theropod dinosaur from Antarctica. Science 264 (5160): 828–830.

Smith ND, Makovicky PJ, Hammer WR, Currie PJ. 2007. "Osteology of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica and implications for early theropod evolution. Zoological Journal of the Linnean Society 151 (2): 377–421.