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.