Screenwashing, for victory!

So if you followed the link from my previous post over to the Great Plains Dinosaur Museum Facebook page, you would have seen a photo of a cute little pachycephalosaur squamosal spike that we found in the first week. Pachycephalosaurs are the famous dome-headed dinosaurs that are often shown headbutting each other (although the evidence supporting this behavior is controversial).

This pachycephalosaur spike came from "trucker's macrosite" which preserves a jumble of bones from various different species. Most of the time, bones in macrosites are water worn, or broken, but a small percentage are better preserved, so macrosites can be good places to look for skull bones, and other diagnostic elements.

One of the other interesting pieces collected from "truckers macrosite" is this fragment:

A braincase fragment from a theropod?

The specimen is constructed from quite thin-walled bone, and has numerous holes ("foramina") passing through it. I was wondering if this might be part of the braincase of a theropod dinosaur. The foramina would therefore represent the holes though which the cranial nerves passed. If anyone has a better idea for the identification of this bone, then I would be very appreciative (I am hoping it is not just parts of a large theropod vertebra).

Trucker's macrosite yielded additional pieces of theropod skull, but each of the interesting specimens from this site is incomplete, with broken ends where (presumably) pieces had broken off during recent weathering. So, in an attempt to find the missing parts of these tantalizing fragments, we returned to the site yesterday to do some intense surface collecting and screenwashing.

Peter Thomas (foreground) and Danny Anduza (shirtless) search for more treasures. Photo by Holley Flora.

Peter, Danny and Holley spent all day collecting every piece of bone from the surface and dry / wet screenwashing shovels of mud to find pieces that had been buried. Today we were trapped in camp by rain, so I started going through the surface collected material to see if we had any of our missing pieces.

Success!

Inside the third bag I looked in (collected by Holley) I found this little gem:

Pachycephalosaur squamosal spike, number 2!
The spiked tip is missing, so we will be back screenwashing again to try and find it!

Crewmember Holley Flora (one of my seasoned field crew from 2013 & 2014) had picked up another squamosal spike from a pachycephalosaur! This is almost certainly from the same specimen as our previous spike, so it is possible that there might be more at the site.

Pachycephalosaurus wyomingensis by Dr. Jordan Mallon.
The spikes we have found are from the back corners of the skull (squamosals) .
(Image from wikipedia)

You might be familiar with the recent research by my supervisor Jack Horner and Mark Goodwin from UCMP Berkeley. In 2009 they hypothesized that the dome and squamosal spikes of Pachycephalosaurus changed through growth. Young animals had no dome, but exhibited long spikes on the squamosals. The characteristic dome-head of Pachycephalosaurus developed through ontogeny, and was only fully-sized in adults. Curiously, adult Pachycephalosaurus had short rounded knobs on the squamosal, instead of the long spikes of youth.

The spikes that we found are quite small and fairly pointed (based on the angle of the sides, as the tips are missing), so we would interpret them as coming from a young Pachycephalosaurus.

As a bonus, in the next few bags of bone fragments, I found quite a few new pieces to go with the possible braincase. Overall, not a bad return for a rain day!

Reference

Horner, J. R., & Goodwin, M. B. (2009). Extreme cranial ontogeny in the Upper Cretaceous dinosaur Pachycephalosaurus.

New juvenile Triceratops and pieces of theropods

From a slow start... finally warming up

During our first week in the field we discovered many important microsites, but I was disappointed with the lack of sites yielding decent large material. However, in the past week we have started to find a few acceptable skeletal sites (and of course, even more microsites!), which is what I'll be reporting on here.

I'm also going to try and blog a bit more often, but with shorter posts each time.

Understanding growth in Triceratops-  a new juvenile Triceratops

One of the ongoing research projects for my coauthor John Scannella, and supervisor Jack Horner is the growth of the horned dinosaur Triceratops. We are especially interested in changes in the shape of the frill from juveniles through to adults, so any new discoveries of juvenile material is very welcome. In the first week we found a fragment from a juvenile Triceratops frill (which we collected) but a few days ago crew member Jack Wilson found a better partial frill which he called "Jack's Blue Juvie Trike":

"Jack's Blue Juvie Trike": Jack's new juvenile Triceratops includes this piece of the parietal (middle of the frill) and three "epiparietal" spikes.

Although it is quite fragmentary, "Jack's Blue Juvie" specimen preserves just the right pieces to tell us some new information about the ontogeny of the frill border. Research by Jack Horner and Mark Goodwin (Horner and Goodwin, 2006; 2008) has shown that in juvenile Triceratops (as seen here), the epiparietals are shaped like equilateral triangles and are unfused or "loose" on the edge of the frill. Through growth, the epiparietals become much less pointed, flattening into a spindle shape and completely fusing to the frill border in adulthood.

Complete Juvie Trike: This is "DF Juvie Trike III" that I found in 2008.
(skeleton on display at Museum of the Rockies, Bozeman; skull on exhibit at the Burpee Museum, IL, and the Smithsonian in Washington DC!).

"Count Trikeula" -an adult Triceratops

We have found a few adult Triceratops sites, but most of these have been quite poor. However, we have finally knocked into a decent Triceratops site which crew member Danny named "Count Trikeula":

Count Trikeula: After a few false starts, our first decent Triceratops site. Here (if you know what you are looking at) you can see part of the epijugal (cheek spike), and the edge of the squamosal (part of the frill).

Despite there being many fine Triceratops skulls in museums, most of these frustratingly lack any contextual data, so are not very useful for understanding Triceratops evolution. Sadly, this is especially true of the holotype(s) of Triceratops held at many venerable institutions on the east coast. 

However, recent collecting by the Museum of the Rockies (Montana State University) and UCMP Berkeley recovered ~100 new Triceratops skulls, and we took care to record contextual data, especially the stratigraphic position of the specimens (whether they occur in the lower or upper parts of the Hell Creek Formation). This effort has revealed that Triceratops evolves from the species T. horridus in the lower Hell Creek Formation to T. prorsus in the upper Hell Creek Formation (Scannella et al., 2014). If our 2014 paper is correct then "Count Trikeula" *should* be a Triceratops horridus. In this way, every new Triceratops specimen we find can be used to test the hypothesis proposed in the Scannella et al., (2014) paper.

Theropod bones

We've had quite a bit of luck finding bones from theropod dinosaurs, including some exceptional odds and ends that will be used for some new research. I'll be posting a bit more on these in the future, but in the meantime here are a few photos:

Theropod femur: This is a femur from a medium-sized theropod; either an immature T. rex, or maybe a very large ornithomimid (ostrich mimic). We dug around the bone but did not find any more bones at this site, so it looks like it is isolated, and not part of a skeleton. In the lower Hell Creek Formation, it is commonplace to find isolated bones like this, and they tend to be covered in a thin layer of white concretion, with the bone itself is fairly brittle. Theropod femora are not common finds however, so we will be jacketing and collecting this specimen.

Raptor phalanx: This is a toe bone from the foot of a small "raptor" dinosaur. I have published a few research papers on how small carnivorous dinosaurs might have used their feet in capturing and killing prey (Fowler et al., 2009; 2011), and even isolated finds like this can be informative.

BONUS 1! : Mystery bone

My crew and I are pretty good at identifying bones in the field. However, occasionally we come across interesting little fragments that have a distinctive shape, but which we cannot immediately identify. Many of these "mystery bones" have turned out to be important finds in the past, so we make a habit of picking them up. So in that vein: does anyone have an idea what this mystery bone might be?

Mystery bone: an isolated fragment from a channel lag deposit. The foramina and texture looks like skull fragment, but the bone is robust enough to suggest it is not from a theropod dinosaur. I was thinking it might be part of the lower jaw, maybe the distal end of a dentary where a predentary might attach. It has enough morphology to be identifiable. Suggestions welcome in the comments!

BONUS 2!: Great Plains Dinosaur Museum, Malta

Some of the fossils that we have found are temporarily on exhibit at Great Plains Dinosaur Museum, Malta. I have intentionally not mentioned a few of the things that are on display there, and you will need to visit the museum's Facebook page to see them (or even better, visit in person!). There are going to be some nice fossils going on display there in the next week or so.

Okay, we're heading off to do some more prospecting!

Denver.

References

Fowler, D. W., Freedman, E. A., & Scannella, J. B. (2009). Predatory functional morphology in raptors: interdigital variation in talon size is related to prey restraint and immobilisation technique. Plos One, 4(11), e7999.

 
Fowler, D. W., Freedman, E. A., Scannella, J. B., & Kambic, R. E. (2011). The predatory ecology of Deinonychus and the origin of flapping in birds. PLoS One, 6(12), e28964.

Horner, J. R., & Goodwin, M. B. (2006). Major cranial changes during Triceratops ontogeny. Proceedings of the Royal Society of London B: Biological Sciences, 273(1602), 2757-2761.

 

Horner, J. R., & Goodwin, M. B. (2008). Ontogeny of cranial epi-ossifications in Triceratops. Journal of Vertebrate Paleontology, 28(1), 134-144.

 

Scannella, J. B., Fowler, D. W., Goodwin, M. B., & Horner, J. R. (2014). Evolutionary trends in Triceratops from the Hell Creek Formation, Montana. Proceedings of the National Academy of Sciences, 111(28), 10245-10250.

 

First report: bad weather and microfossils

Murderwind!

So... last night we were hit by 60-80 mph winds and large quarter/golfball sized hail.

50-cent coin sized hail!
(Photo: J. Wilson)

My cheap tent was destroyed by the hail (I have a replacement). Hail also blasted the skylights off the trailer and put some holes in other plastic fixings around camp. The truck is okay. (Photo: J. Wilson)

Today we are clearing up debris, drying out sleeping bags, and cannibalising my tent to fix holes in others.

Prospecting for dinosaurs

The past couple of days we have been out prospecting and found some interesting things. We haven't come across a particularly good dinosaur site yet; We discovered four sites with scrappy Triceratops remains, and crewmember Danny found a Triceratops site that had nice preservation quality:

"Horns of Plenty": This is part of the frill of a Triceratops. This could have been a good site, but we could not locate the bone layer as it was very overgrown with plants. No matter, we will find another.

If we had been prospecting in the upper Hell Creek, then I would expect to run into a Triceratops site every 200 metres or so. However, the lower Hell Creek is much less rich for fossils, so we have to cover much more ground. We will keep looking, and I am sure we will turn up something good eventually.

Microsites

Despite not finding much large material, the past few days we have recorded four good microsites. Microsites yield lots of tiny fossils like teeth and small vertebrae, and occasional larger fossils like finger and toe bones (phalanges) and claws. Microsites are used by paleontologists like Dr. Greg Wilson and his students to study how the complete fauna of the Hell Creek Formation changes through time. Our new localities are all very low in the Hell Creek Formation, and so should provide valuable datapoints.

This is a metatarsal III (middle toe) of either a medium-sized Tyannosaurus rex, or a large ornithomimid dinosaur. This specimen was recovered from Danny's site "Danny's rex micro".

This is a tooth from a dromaeosaurid: a small "raptor" dinosaur. Jack Wilson found this at his site "Jack' Neck Microsite". This site is potentially SUPER-EXCITING as it yielded the posterior end of a cervical (neck) vertebra which *might* be from a pterosaur (which are incredibly rare in the Hell Creek). Black bar width 1cm.

Fish remains from"Warwick's diddy Microsite": a skull plate (left); two vertebrae (top); a ray tooth (right), and a toothed palate (bottom middle). Scale in cm.

A champsosaur vertebra (left) and turtle fragment (right) from "Warwick's diddy microsite".

Two phalanges (toe bones) from "Warwick's diddy microsite". Scale 1cm.

Tyrannosaurus teeth. Often commercial collectors will sell small teeth like this as "Nanotyrannus", but it has not been demonstrated that Nanotyrannus is actually a unique species. Research by tyrannosaur expert Thomas Carr (and others) shows that purported Nanotyrannus specimens actually represent immature Tyrannosaurus.

Teeth from the small raptor-like dinosaur Richardoestesia. No-one knows what Richardoestesia looked like as so far scientists have only found its teeth. These are very unusual-looking for theropod teeth, suggesting that this species might have had an unusual feeding method or ecology.

Another dromaeosaurid "raptor" tooth.

I'm saving the second-best fossil for last (assuming that Jack's vertebra is pterosaur). Here is a jaw of a marsupial found two days ago:

Marsupial lower jaw. I am hoping some mammal expert can help identify this specimen in the comments. It looks to me like Glasbius sp. maybe, or something related?

Ok, back to cleaning up camp!