Thursday, December 29, 2016

The Fight for Paleontology in Bears Ears

The Fight for Paleontology in Bears Ears

As many of you may have seen, on December 28th, 2016, President Obama used the authority assigned to him under the Antiquities Act of 1906 by Congress to declare a Bears Ears National Monument. Now most of the public debate surrounding this area has focused on the wealth of ancient sites, artifacts, rock art, and tribal connections to the area. But the paleontological resources of the area are also highly significant. I had been following with interest and then growing alarm as various advocacy groups began pushing for additional protection for various cultural and scenic resources in the area. State legislators were talking about a public lands "Grand Bargain." Tribal leaders and conservationists were talking about a national monument. No one was talking about the paleontological resources of the area. This was a great concern to me since that has been my field area for several years now and an area I have been involved in and around for well over a decade.
Moonrise over Comb Ridge, where my work has focused for the last several years.

Pushing for Paleontology

                So I took action. I went down to Bluff in March 2016 to attend Friends of Cedar Mesa's Celebrate Cedar Mesa and agitate. I poked at people; organizers, legislators, BLM administrators, and conservationists. I made a general nuisance of myself and apparently it did some good. Though no Utah state or federal legislators ever got back to me, the folks involved with monument status began communicating about the fossils in the area. It started with simple descriptions of the paleo resources of the area. When I was asked to compile a bibliography of the same, though, that's when I think I opened lots of eyes. The bibliographic list of publications together ran for over 20 pages and left many mineral-geology resources off (as they were being dealt with elsewhere).
Looking west from Bluff at Celebrate Cedar Mesa 2016
                That is when things accelerated. In April I was brought down to Bluff to talk to folks from FoCM and The Wilderness Society about the importance of the area to paleontology and about the 300 million years of stories in the area, preserved in the rocks of the Bears Ears area. Some of this was eventually made into a video highlighting our personal connections to the area.

The video of the personal and deep-time aspects of the area, produced by TWS.

                Around this time I was also asked to draft language that would protect paleontology in a monument, should the president move forward with a monument. I would have been happy to have provided similar input to the PLI as well, but considering they barred non-San Juan County residents from participating in the Bears Ears portion it isn't surprising that they didn't contact me. A rumor also began circulating that Sally Jewell, the Secretary of the Interior, would be visiting the region over the summer. I sent her a message inviting her to our field camp at Comb Ridge. While the invitation was turned down, I did get a response from her scheduling secretary; encouraging.

Increased Advocacy

                Over the summer the Secretary's travel plans firmed up and it became clear she would be visiting Bluff in July. I made the three hour trek down there and saw loads and loads of people. The line to get inside the community building in Bluff stretched back on itself multiple times in the heat and the organizers had set up an outside listening area. I patiently waited in line to get a number to speak. Despite arriving at (what I had assumed was) a decent time, I was unable to secure a seat inside. Instead I guzzled water outside with my friend Chris and listened to the first half hour of speakers come and go. The atmosphere was charged but no one was being too terribly rude. I got a text from an inside person and worked my way into the building where the atmosphere was more tense, more dense, but only slightly less hot than outside. 

View inside the Bluff Community Center. Photo by ReBecca Hunt-Foster.

                My number wasn't drawn as the day drew near its end but then the Secretary announced that she would be extending the meeting on account of all the people still in attendance. While several people had to leave, including Chris, most of the folks stayed. The Community Center did not seem to empty out, though as people from outside filled in the spaces. As luck/fate/random chance of the draw would have it, my number was called. In fact it was the second-to-last number called to speak. Like the Hamilton song says, I wasn't going to throw away my shot. Many folks had pre-written speeches in hand when they approached the mic but not me. I had an outline in my head and key ideas to touch on; I got up there and spoke based on that. I would like to think my lack of notes in hand and ease with the subject I was discussing helped but I cannot be sure.
Speaking to the panel in Bluff. Photo by David Rankin.
                After probably the most stressful two minutes of my career the meeting was essentially over. I helped pick up the best I could and chatted with folks from FoCM, TWS, the Utah legislature, and various friends before heading to a field camp just up the road. My conscience was clear at this point; I'd made my case to people who would make the decisions. I figured that my work was essentially done at this point.

Rob Goes to Washington

                As the summer progressed the Bears Ears radar went quiet for the most part. In September, though, things began to pick back up. I was asked for updated information to provide to the Administration and to speak around Colorado. Again, all of this was coming from the monument advocacy side; the PLI crowd still had not been in contact with me, though they had consulted with (and apparently not taken the advice of) other geoscientists who had been active in the Bears Ears area. Also in September the idea was broached to me by Scott of TWS of going to Washington DC and presenting to the White House, the Department of the Interior, and the USDA/Forest Service about paleo in the Bears Ears area. After a fair bit of stop-and-start action, along with an intervening paleontology conference, I ended up visiting DC for the first time ever on Halloween.
Yours truly standing inside the White House Council on Environmental Quality office.
                Having never been to DC before this was sort of a double whammy. Here I was, seeing historic buildings, sites, monuments, cemeteries, and departments for the first time but also going into these "Halls of Power" to meet with folks and talk about the land and science that is essentially my consuming passion. People asked if I was nervous going into this part. I wasn't, not really. I know the science, the landscape, the geology, and the region like the back of my hand.
                In the meetings questions came up about the publication record of certain regions, the relative rarity of certain resources, why certain areas on our map (more on that in a later post) weren't identified as "high potential", and what work was currently happening in the region (along with many others). These are questions I was able to answer but was also happy to be asked; it meant that the people in these departments were taking paleontology seriously and had done their background reading. I left DC knowing that the folks I had talked to were energized about paleontology and hopeful that their enthusiasm and the new information from me would be transformed into paleontology being protected in any future proclamation. Scott from TWS was likewise hopeful.

The Final Days

                After the election there was some serious concern among folks that despite all the legwork done by experts, advocates, and lawmakers on both sides of the issue that nothing would happen. Despite Rob Bishop et al. proclaiming that a Bears Ears National Monument would be a midnight monument, that the State of Utah would sue, etc., it was clear at the meeting (and from the amount of work that Bishop put in) that both sides of the issue wanted to see the area protected. There was frantic scrambling to make sure everything was in place should the President decide to act. In the midst of all this chaos some of my colleagues and I managed to put out a preprint on the first vertebrate traces from Comb Ridge, in the Bears Ears area. Everything was poised and ready but no one was really sure it was going to happen until it did. I got a call from an advocate about half an hour before the White House made the announcement; even then I was on pins and needles. Would paleo actually be protected?
                It is with great relief that I read the proclamation and saw that paleontology was explicitly called out and protected under the proclamation. Perhaps even more surprising (and gratifying) is that a large portion of the paleontology-specific text was mine. I had helped craft this. I had made a difference here. Before I got involved in the process no one on either side of the issue had considered paleontology in the region seriously. No matter what happens going forward we know that paleontology in the region will be protected. By explicitly mentioning it in the proclamation, the president has acknowledged that the resources are significant not only to the area but to the country as a whole.
The paleontological resources in the Bears Ears area are among the richest and most significant in the United States, and protection of this area will provide important opportunities for further archaeological and paleontological study. Many sites, such as Arch Canyon, are teeming with fossils, and research conducted in the Bears Ears area is revealing new insights into the transition of vertebrate life from reptiles to mammals and from sea to land. Numerous ray-finned fish fossils from the Permian Period have been discovered, along with other late Paleozoic Era fossils, including giant amphibians, synapsid reptiles, and important plant fossils. Fossilized traces of marine and aquatic creatures such as clams, crayfish, fish, and aquatic reptiles have been found in Indian Creek's Chinle Formation, dating to the Triassic Period, and phytosaur and dinosaur fossils from the same period have been found along Comb Ridge. Paleontologists have identified new species of plant-eating crocodile-like reptiles and mass graves of lumbering sauropods, along with metoposaurus, crocodiles, and other dinosaur fossils. Fossilized trackways of early tetrapods can be seen in the Valley of the Gods and in Indian Creek, where paleontologists have also discovered exceptional examples of fossilized ferns, horsetails, and cycads. The Chinle Formation and the Wingate, Kayenta, and Navajo Formations above it provide one of the best continuous rock records of the Triassic-Jurassic transition in the world, crucial to understanding how dinosaurs dominated terrestrial ecosystems and how our mammalian ancestors evolved. In Pleistocene Epoch sediments, scientists have found traces of mammoths, short-faced bears, ground sloths, primates, and camels.
- Proclamation establishing Bears Ears National Monument, December 28th, 2016 
                We are continuing our research in the area with two aggressive excavations scheduled for 2017 in the Bears Ears along with continuing high school field camp work, and I am glad that the administration was willing to listen to the concerns of scientists from around the country about this area and the importance of paleontology to understanding its history. Looking forward, this proclamation serves as a framework for future paleontological work in the region. Nearby Grand Staircase-Escalante National Monument has similar language in its proclamation. This language has enabled a flowering of scientific research across the Grand Staircase. Virtually all of the new dinosaur species coming from that area (>95% of them) have been described since the Monument was declared and the wording of the proclamation has allowed that to happen. Horned dinosaurs, duck-billed dinosaurs, and young relatives of Tyrannosaurus rex have all been named in the last two decades. Hopefully, with paleontology being singled out and protected in Bears Ears National Monument, a similar explosion in our knowledge of the past will occur here.
                There is still work to be done. The fossil-rich areas in and around Red Canyon, currently being worked by colleagues from the Museum of Moab and Appalachian State University, were excluded from the Monument. Of course, with the new administration coming in there are other questions about funding for this and other public lands. We have our work cut out for us. I am mostly happy but I am not content and complacent. More blogs will be forthcoming on this topic too - both about Bears Ears paleo and the process of making a monument.
                I would like to extend my tremendous thanks to all of my friends and colleagues. Field crews from SGDS and NHMU, under Andrew Milner and Randy Irmis were vital to me getting started in paleo in the Bears Ears, as was a GeoCorps internship with the BLM's Canyon Country District in 2013. Canyonlands Natural History Association, the Museum of Northern Arizona, and the Museums of Western Colorado have also directly made my work in this area possible. Conservationists Josh Ewing, Amanda Podmore, and Scott Miller listened when I started poking things with a sharp stick and ranting about paleo in the area. Thank you to all the folks who listened to me at the meeting in July in Bluff as well as in the offices of DC. All my colleagues who signed my letter that I pestered you about; many thanks! It made a difference. Thank you also to Randy, Jeff, and Kenshu for all the hard work getting the SVP to send a letter talking about the importance of paleo, regardless of how (monument vs. NCA) it would be preserved. Special thanks go out to Julie McHugh, Brian Engh, Tara Lepore, May Blueotter, Xavier Jenkins, and all the people who have been part of our Comb Ridge field crews. Many special thanks especially go to Jen McCollough and Abby Landmeier for all their support during this whole process. Now, prepare for more Bears Ears blogs in the coming year!
Portal to the Triassic in Bears Ears National Monument
Edited 12/30 to reflect more accurately how Bishop's PLI planning team interacted with other paleontologists.

Thursday, December 22, 2016

Ceratosaurus Part 2: What do we actually know about Ceratosaurus teeth?

What you'll notice about both of these diagnoses, however, is that they contain little in the way of dental characters. Sure they both say the premaxilla only contains three teeth, but that is of little help if you are trying to ID isolated teeth. This brings me to the crux of this post in the first place

As I said in a previous post, "Teeth attributed to Ceratosaurus do turn up in the field, however, and are usually distinguished by the presence of ridges near their bases."

 Madsen and Welles (2000) found "longitudinal grooves" in the anterior dentary teeth of Ceratosaurus magnicornis (this is not listed in their diagnosis. Another tooth character is though: "the teeth are longer and stouter."), and also cited "persistent parallel grooves on the medial surfaces of the premaxillary teeth and the anterior three teeth of the dentary," in the etymology for C. dentisulcatus (this morphology is not listed as an autapomorphy in their diagnosis - though "teeth more massive" is). Later in their publication, however, Madsen and Welles (p. 35) do state that, "lateral grooves are diagnostic of the premaxillary and anterior three teeth of the Ceratosaurus dentary," when discussing Ceratosaurus sp. from Tanzania. In the next paragraph they discuss "lingual grooves" as being characteristic of Ceratosaurus. They point out that these grooves are not diagnostic to the species level. There are two problems with this: there is now only one recognized species of Ceratosaurus, and the holotype lacks premaxillary and anterior dentary teeth.

While Gilmore does use some dental-based characters, they are not tied to a specific tooth morphology and instead deal with the number of teeth in the various tooth-bearing bones.

So what do we actually know about Ceratosaurus teeth?
Plate 17, Figure 1 from Gilmore (1920), showing the right side of the holotype of Ceratosaurus

Plate 17, Figure 2 from Gilmore (1920), showing the left side of the holotype of Ceratosaurus
The holotype lacks the apparently diagnostic teeth of Madsen and Welles' C. dentisulcatus. As you can see from Gilmore, the left hand side of the skull features no anterior teeth. The right side is equally bleak when it comes to anterior dentition. So we are now faced with a tooth morphology that may be diagnostic (but not used in a formal diagnosis) of a junior synonym that cannot be directly be compared with the holotype.

Continuing to muddy (or clarify?) the waters is C. ?meriani, from the Late Jurassic of Switzerland. Madsen and Welles (2000) figure it and refer it to Ceratosaurus sp., and Mickey Mortimer over at the Theropod Database says, "It differs from Genyodectes and Ostafrikosaurus in lacking mesial serrations. As it is of identical size and found in temporally equivalent beds, I believe it should be called Ceratosaurus meriani." Well there are other teeth from the Late Jurassic that have fluting and lack mesial serrations. Specifically some teeth referred to Ceratosaurus from the Morrison Formation of the American West. But why are they referred to Ceratosaurus? It is the right size and shape and comes from the right aged beds...but that's usually not good enough to assign to a highly exclusive clade.

So let's sum up what we can say about the teeth of Ceratosaurus (and please chime in if I've goofed somewhere):

  • Ceratosaurus nasicornis has no known premaxillary or anterior dentary teeth
  • C. magnicornis has both premaxillaries preserved but, again, no teeth preserved in situ. It also lacks a dentary
  • C. dentisulcatus preserves both an toothed premaxilla and dentary with the lingual surfaces of the premaxillary and anterior dentary teeth preserving apicobasal grooves.
  • C ?meriani lacks mesial serrations and appears to preserve apicobasal fluting
  • C. "stechowi" from Tendaguru has apicobasal fluting
  • C. "sulcatus" from Como Bluff, Wyoming preserves apicobasal fluting
  • Several teeth from the Mygatt-Moore Quarry have been referred to Ceratosaurus on the basis of apicobasal fluting.
So it seems that people are treating these apicobasal flutes (and in some cases the lack of mesial serrations) as diagnostic to Ceratosaurus. But apicobasal flutes are known in more taxa than just Ceratosaurus; several Triassic archosauriform tooth morphotypes possess them, as do temnospondyls, some phytosaurs, some early Jurassic dinosaurs (WFtP), spinosaurs, crocs, and gators. That's just tetrapods; I haven't wanted to dive deep into what sort of crazy dentition fish might have. As I understand it (though I don't have any sources right next to me at the moment) this adaptation would be useful for resisting strain on the tooth; basically the animal was punching through tough, wriggling stuff with its face. Understandable then that many things that eat tough prey would have this sort of adaptation.

Where does that leave us with Ceratosaurus? Well it leaves us with the possibility (not the certainty) that Ceratosaurus had apicobasal fluting on its anterior teeth. Certainly specimens with non-dental remains seem to suggest at least one species referred to Ceratosaurus previously had these flutes. I would urge caution, however, in assigning all Late Jurassic stout, fluted theropod teeth to Ceratosaurus. First off, the holotype doesn't have them, so the referral is based on previously referred specimens. That sort of secondary referral is done relatively frequently but it should give one cause for consideration. The second point is that we really don't have a good idea of the dental variation in other Late Jurassic theropods. We know the teeth of Allosaurus fairly well, but what can we say of the tooth structure at all major tooth positions in Torvosaurus, for example (especially considering derived megalosaurs, the spinosaurs, developed fluted tooth crowns as well)? Do we really know what the teeth were like in some of the mid-sized Morrison taxa as well? Since most aren't represented by good cranial remains we don't know what tooth variation is out there.

In closing, we can say that it is likely Ceratosaurus had fluted front teeth but because of problems with the type specimen and the plesiomorphic nature of dental fluting, the rampant homoplasy in tetrapod dentition in general, and the lack of information about other Morrison theropods' teeth it is unwise to assign isolated fluted teeth to Ceratosaurus at all. Hopefully descriptions of other Ceratosaurus specimens with preserved anterior teeth along with a better understanding of Morrison theropod tooth diversity will lead to more accurate diagnoses of these fluted theropod teeth.

Minor aside

Life happens. I've been off the blog game for almost the whole year but I am hoping to be back at it through 2017, especially in terms of blogging about our next publications we have coming out. I've also brought a couple amigos on board here at the Prehistoric Pub so we plan on at least not letting you all down too much this next year. Onward to the next paleo discovery!

Works Cited

Madsen, James H.; Welles, Samuel P. 2000. "Ceratosaurus (Dinosauria, Theropoda) a revised osteology." Utah Geological Survey Miscellaneous Publication 00-2. pp. 80

Wednesday, December 21, 2016

Introducing your new bartender, Xavier Jenkins!

Hi, all!
I'm new to prehistoric pub, and blogging in general. I figured that I'd introduce myself so you all can get to know me!

I'm Xavier Jenkins and I am a Freshman in Biological Sciences at Arizona State University. Throughout my entire life I've aspired to become a paleontologist, and in summer of 2015 I went on my first dig with paleontologist (and fellow blogger) Robert J. Gay.
                                     The Triassic Dream Team. Rob Gay, Tara Lepore, and I (Bottom right)
My research  has been focused on the paleoecology of the Chinle Formation of Utah, and I'll dig up anything I can there. Particularly, I want to get a better grasp on how these prehistoric monsters interacted with each-other, and I want to fully comprehend what this ancient environment looked like by employing methods such as screen washing to ensure that no fossil is left behind.

I am working on five or so projects relating to this research, including the description of new taxon and a mass mortality bone bed. I never thought I'd say this, but I've learned to love microfossils and I hope to be studying them for my professional career. Last summer, I worked as a Field Assistant at Comb Ridge and Fry Canyon with Robert Gay. Overall, I'm super excited to see what our research reveals! Every trip has revealed more and more, and now we got our self a bone-bed!

                              New taxon in the works. Look at those serrations! Scale=1 mm. Image is from Gay et al. 2016
In addition to doing research in the Chinle of Utah, I am working in an Ecology lab at Arizona State University, where I am studying the trophic levels of desert streams and the fish and invertebrates within. When I'm not procrastinating to study for my latest test I am either hanging out with my fiance, Madison, or I am playing Town of Salem with my friends and colleagues, Rob Gay and Nathan Van Vranken. I look forward to updating you all on our research, and I'll do my best to keep you entertained! Here's a link to our crew's latest preprint!

Wednesday, January 27, 2016

Ceratosaurus Part 1: The history of a predatory horned dinosaur.

Disclaimer: I promised you all a post about the teeth of Ceratosaurus. This is not that post. In reviewing the history of Ceratosaurus I found the post growing with background knowledge but no discussion of teeth. It make sense; there is backstory here dating back to Marsh in the 1880s! So I have decided to break this into two posts. The first post, this one, covers the history of Ceratosaurus research. The next post, out soon, will cover just the dental aspects of this charismatic animal.

Ceratosaurus, the "horned lizard," was cool beast, no doubt about it! Here we have a theropod with huge fangs that was over 20 feet long, and had bone studded armor along its back! And that is to say nothing about those flamboyant crests on its face; one sits above its nose and another one above each of its eye. It was initially described by Marsh back in 1884 and is relatively well known thanks to a number of specimens from across the American West, mainly in Colorado and east-central Utah. There are large animals, presumed to be adults, and smaller individuals (presumably juveniles) in our sample as well, so we should theoretically have a good grasp on what this animal was like. Let's take a look at the history of Ceratosaurus, starting after Marsh's initial publication.

Gilmore in 1920 redescribed Marsh's animal (thankfully!) and revised the diagnosis for Ceratosaurus. I have quoted him in full below.
Generic characters: Premaxillaries with three teeth; maxillaries with 15 teeth; dentary with 15 teeth; 9 cervical vertebrae plano-concave; dorsal vertebrae biconcave; 5 sacrals; distal caudals without special lengthening of prezygapophyses; pelvis coossified; pubis with closed obturator foramen; 4 digits in manus, first and fourth reduced; probably 3 digits in pes; dermal ossifications; abdominal ribs present.
Plate 17, Figure 1 from Gilmore (1920), showing the right side of the holotype of Ceratosaurus
Plate 17, Figure 2 from Gilmore (1920), showing the left side of the holotype of Ceratosaurus

This is a workable definition for the time but we know that some of these are not autapomorphies (things found only in one type of organism). In fact, some of these characters are ancestral for theropods, or even archosaurs. Still, we can't fault Gilmore. He was working with what comparative material he had at the time and did an excellent job. Perhaps most outstanding, even compared to papers being published in the 21st century, are his excellent illustrations of the material he is describing.

That same year (1920), Werner von Janensch published on several theropods recovered by German expeditions to the Tendaguru beds. The most famous of these is probably Elaphrosaurus bambergi, a medium sized ceratosaur subject to much speculation in the decades since. In this same publication Janensch commented on the presence of Allosaurus, which he later named Allosaurus tendagurensis (Janensch, 1925), though this has been suggested to be a carcharodontosaurid. Additionally, and relevant to the post here, he identified Ceratosaurus (?) sp., Megalosaurus (?) ingens, and Labrosaurus stechowi from the same beds.
The butt of Elaphrosaurus on display in Berlin during the 2014 SVP meeting.

Tibia, teeth, and dorsal vertebra of "Allosaurus tendagurensis", also on display in Berlin. Whatever it was, it was big.
 Janensch didn't illustrate his Ceratosaurus sp., which was based on three dorsal vertebrae, but he did illustrate his "Megalosaurus" ingens and "Labrosaurus" stechowi. These will be relevant to our discussion on the teeth of Ceratosaurus.
Figure 6 from Janensch (1920) with the tooth of  Megalosaurus (=?Ceratosaurus) ingens

Figures 7 & 8 from Janensch (1920) with a ?labial and basal view of the tooth of  Labrosaurus stechowi (=?Ceratosaurus sp.)
Work continued sporadically on the genus. In 1963 Jim Madsen and William Stokes presented at the Geological Society of America meeting in Provo about new material from the Cleveland-Lloyd Quarry in central Utah. It was obvious that there was more to this animal than had been previously described. The last (so far) phase in new Ceratosaurus species came in 2000 when Madsen and Sam Welles named two new species: C. magnicornis and C. dentisulcatus. C. magnicornis was so-named from its large nasal horn, while C. dentisulcatus derives its specific name from grooves Madsen and Welles saw on the premaxillary and anterior dentary teeth; this taxon included the remains initially described in that 1963 abstract, while C. magnicornis was named from remains found in western Colorado.

Your faithful author with part of the holotype of Ceratosaurus magnicornis at Dinosaur Journey in Fruita, Colorado
In addition to coining two new species, Madsen and Welles looked over the material that had previously been assigned to the genus by other workers, including the material from Tendaguru. This was the most comprehensive review of all the material assigned to Ceratosaurus to date. Here's a summary of their findings.
  • Ceratosaurus roechlingi (Janensch 1925) may be a very large Ceratosaurus but isn't diagnostic past Ceratosaurus sp.
  • Labrosaurus stechowi is likely a junior synonym of C. roechlingi
  • The Ceratosaurus vertebrae that Janensch (1920) identified as Ceratosaurus sp. are correctly IDed
  • Labrosaurus meriani (Janensch 1920), based on an isolated fluted tooth from the Bern Jura, in Switzerland is referred to Ceratosaurus sp.
  • Bones previously referred to Ceratosaurus from Oklahoma (Stovall, 1938) are indeterminate theropod bones at best
  • Ceratosaurus sp. teeth from western Colorado are in fact correctly IDed
  • Material collected by BYU at Dry Mesa, Colorado and Agate Basin, Wyoming, will be described soon and represent the largest known specimen of Ceratosaurus. As of 1999 the preparation of this specimen was complete.
  • Megalosaurus ingens, sometimes referred to as Ceratosaurus ingens (Rowe and Gauthier, 1990), is too big to be Ceratosaurus
  • Labrosaurus sulcatus, based on an isolated fluted tooth from the Morrison Formation of Colorado, is referred to Ceratosaurus sp.
Now some of these conclusions have held up while others have not been mentioned since 2000. Later workers, for example, don't discuss any non-North American Ceratosaurus sp. remains. There is probably a good reason for this; I will go into more detail about that on my next post. Other claims are somewhat odd (a junior synonym of a newer taxon that isn't diagnostic?). Even today, however, Madsen and Welles (2000) is the best review of all material historically assigned to Ceratosaurus.

2000 was a busy year for Ceratosaurus research. That year Brooks Britt and colleagues presented about new specimens of Ceratosaurus from Colorado, Utah, and Wyoming at the Society of Vertebrate Paleontologists annual meeting; this likely includes the material that Madsen and Welles referenced in their publication as being held at BYU. While some of this information has made its way into later publications, for the most part these specimens remain undescribed to my knowledge.

As paleontology is an evolving science, new analytical tools are always being developed. The same year that Madsen and Welles revised our view of Ceratosaurus and Britt et al. clued us in to new specimens from Wyoming, Oliver Rauhut used modern phylogenetic techniques to define Ceratosaurus as part of his Ph.D. thesis. His found the following autapomorphies (taken from Rauhut (2000) by way of Wikipedia, since I don't have access to the original thesis).
  • a narrow rounded horn core centrally placed on the fused nasals
  • a median oval groove on nasals behind horn core
  • a premaxilla with three teeth
  • premaxillary teeth with reduced extent of mesial serrations
  • chevrons that are extremely long
  • a pubis with a large, rounded notch underneath the obturator foramen
  • small epaxial osteoderms

Some of these characters still look good 16 years later, but some of them are a bit subjective, such as, "chevrons that are extremely long." This may be due to someone simplifying what Rauhut said for Wikipedia or it may reflect the long-term trend away from relative character states. Without having Rauhut's thesis I can't really say either way.

Breaking up this wall of text with a Ceratosaurus illustration. Image by DiBgd at English Wikipedia, CC BY 2.5
Rauhut (2000) wasn't the last word on the question of, "What is Ceratosaurus?" In 2008, Matt Carrano and Scott Sampson published a revised phylogentic analysis of the ceratosaurs. Since Ceratosaurus is kind of essential to understand if you're talking about a group of animals sharing its name, they came up with another revised diagnosis.
Ceratosaur with: (1) mediolaterally narrow, rounded midline horn core on the fused nasals, (2) medial oval groove on nasals behind horn core, (3) pubis with large, rounded notch underneath the obturator foramen, (4) small median dorsal osteoderms
As time passes you can see that the subjective characters have disappeared, such as the extremely long chevrons. Others characters are now better defined. We've arrived at what is essentially the definition we are using today in 2016 when we want to refer material to Ceratosaurus. Of course you may notice that this list is pretty small, meaning that most of the skeleton can't be used to identify individual bones. Carrano and Sampson (2008) do a couple of other interesting things in regards to the history of Ceratosaurus; they restrict the use of Ceratosaurus to North America (though without discussing the African material), and explain how the Madsen and Welles (2000) taxa are junior synonyms with no unambiguous autapomorphies. So from this point onward it is generally accepted that only one species of Ceratosaurus is valid, C. nasicornis, and that the genus Ceratosaurus is found only in the Morrison Formation of western North America, a point that Carrano et al. (2012) reiterate.

Juvenile Ceratosaurus partial skeleton on display at the North American Museum of Ancient Life. Photo by Zach Tirrell, CC BY-SA 2.0
Last, and most late-breaking, is a paper out today in JVP! In this paper Carrano and Choiniere discuss the arm of the holotype of Ceratosaurus from the US National Museum. The paper stays true to its subject and redescribes the arm, something the entire skeleton is in need of, as it has undergone de-mounting and additional preparation work. They found that, as many have suspected, the hand and arm of Ceratosaurus is most similar to those of early theropod dinosaurs like Dilophosaurus, and not as closely aligned with later theropods. Even from its fellow derived ceratosaurs, the Abelisauroidea, the hand and arm appear primitive - which would make sense considering its placement relative to abelisauroids in the theropod family tree. Carrano and Choiniere (2016) also show that Ceratosaurus didn't have a useless hand either. Although small and oddly shaped compared to contemporaneous Allosaurus, the hand of Ceratosaurus was still adapted to grasp items (though not to the same extent as other theropods). The lack of any preserved claws from across the Morrison associated with Ceratosaurus skeletons makes things even more difficult; was Ceratosaurus tiny-clawed, grabbing small prey items? Or did it have huge grappling-hook slashers, ready to grab on to passing sauropods? We just don't know.
Cast of the hand of the holotype of Ceratosaurus nasicornis. Note the lack of any preserved fingers. Photo by Smokeybjb, CC BY-SA 3.0
In conclusion, how can we sum up what we know of Ceratosaurus? Well there appears to be one wide-spread but relatively uncommon (compared to Allosaurus) species of Ceratosaurus that existed in western North America during the Late Jurassic. Variation that has led to different species in the Morrison Formation being named, such as Ceratosaurus magnicornis and Ceratosaurus dentisulcatus are best explained by individual variation and changes associated with the animal's growth. Other examples of Ceratosaurus may exist outside of North America but those specimens have not been rigorously examined since 2000. Numerous teeth from across western North America, Europe, and Africa have been referred to this animal, but most workers view the non-North American specimens as not part of the Ceratosaurus hypodigm. Are these referrals sound? For that, you'll have to wait until my next post!

Works Cited

Britt, Brooks, Chure, D. J., Holtz, T. R., Jr., Miles, C. A. & Stadtman, K. L. 2000. A reanalysis of the phylogenetic affinities of Ceratosaurus (Theropoda, Dinosauria) based on new specimens from Utah, Colorado, and Wyoming. Journal of Vertebrate Paleontology 20: 32A

Carrano, Matthew T., Roger BJ Benson, and Scott D. Sampson. 2012. "The phylogeny of Tetanurae (Dinosauria: Theropoda)." Journal of Systematic Palaeontology 10.2: 211-300

Carrano, Matthew T.  & Jonah Choiniere 2016. New information on the forearm and manus of Ceratosaurus nasicornis Marsh, 1884 (Dinosauria, Theropoda), with implications for theropod forelimb evolution. Journal of Vertebrate Paleontology

Carrano, Matthew T., and Scott D. Sampson. 2008. "The phylogeny of Ceratosauria (Dinosauria: Theropoda)." Journal of Systematic Palaeontology 6.02: 183-236.

Gilmore, Charles W. 1920. Osteology of the carnivorous Dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus. Bulletin of the United States National Museum 110: 1–154.

Janensch, Werner. "Über Elaphrosaurus bambergi und die megalosaurier aus den Tendaguru-Schichten Deutsch-Ostafrikas." Sitzungsberichte der Gesellschaft naturforschender Freunde zu Berlin 8 (1920): 226-235.

Janensch, Werner. 1925. "Die Coelurosaurier und Theropoden der Tendaguru-Schichten Deutsch-Ostafrikas". Palaeontographica, Supplement 7 1: 1–99.

Madsen, Jim H. Jr., and Stokes, William L., 1963, New information on the Jurassic dinosaur Ceratosaurus: Geological Society of America, Special Paper 73, p. 90 (abs.)

Madsen, Jim H.; Welles, Samuel P. 2000. Ceratosaurus (Dinosauria, Theropoda): A Revised Osteology. Utah Geological Survey. pp. 1–80.

Marsh, O.C. 1884. "Principal characters of American Jurassic dinosaurs, part VIII: The order Theropoda" American Journal of Science 27(160): 329–340
Rauhut, Oliver. 2000. The interrelationships and evolution of basal theropods (Dinosauria, Saurischia). Ph.D. dissertation, Univ. Bristol [U.K.]. 440 pp

Rauhut, Oliver W. M. 2011. "Theropod dinosaurs from the Late Jurassic of Tendaguru (Tanzania)". Special Papers in Palaeontology 86: 195–239.

Rowe, T., and Jacques Gauthier. 1990. "Ceratosauria." in The Dinosauria, Weishampel, Dodson, and Osmólska, eds. University of California Press. pp. 151-168.
Stovall, J. Willis. 1938. "The Morrison of Oklahoma and its dinosaurs." The Journal of Geology: 583-600.

Wednesday, January 20, 2016

"Why does science have to name every little thing?"

One of the most common questions I got when I was teaching as some variation on that theme. "Why do scientists have to make things so complicated?" "Why can't they just call it something simple?" It is a question bigger than just high school level as well; one of the barriers to effective science communication and education seems to be the general "fear" of overly technical language . The general public seems to view scientists as speaking in convoluted and complex terms.

It is true that scientists have devised some very complex ways of describing things that might seem simple to a layman. And sometimes we can get wrapped up in using the terms we are familiar with when talking about our research, to the detriment of any non-technical audience. The media is also partially to blame as well, with perpetuating ideas such as all prehistoric reptiles are dinosaurs. But why do these terms exist in the first place?

This brings me to Hendrickx et al. (2015). Hendrickx and his coauthors published a paper last year breaking down theropod dinosaur teeth and analyzing many different aspects of their morphology. In addition, the authors created a standardized terminology for future paleontologists to use when describing their dinosaur teeth. Hendrickx and his coauthors explain why creating such a terminology is needed succinctly; in effect answering the question of why scientists create names for so many things.
...several pivotal theropod taxa with well-preserved dentitions still lack a thorough dental description...leading numerous authors to identify isolated theropod teeth to broad clades with uncertainty...isolated teeth are key pieces of evidence to assess vertebrate paleoecological diversity and are often used for stable isotopic studies with various applications...A better understanding of theropod anatomy and morphological variation is therefore central to help resolving systematic relationships and to provide paleoecological clues. Tooth morphology is tied to diet, which has extensive evolutionary repercussions, such as morphological convergence, more than other parts of the skeleton. Yet, theropod teeth have been shown to possess many diagnostic features of taxonomic value...Although theropod teeth seem simple at first sight, this is effectively a result of the absence of comprehensive studies on tooth anatomy and morphological variation among theropods, as well as the lack of a uniform anatomical nomenclature.
What does the wall of text mean? Basically, theropod dinosaur teeth can be used to study evolutionary relationships, paleoecology, and several other important things in paleontology, but no one has bothered to come up with a good way to talk about them.

That's the crux of scientific terminology; coming up with a good way to talk about things. Good, in this case, means usable. Terms should describe well-defined parts of an organism's anatomy. If we say, "the tip of the tooth," on a tooth that has multiple "tips", how are we to know which specific tip we're talking about? Are there differences between "wrinkles" and "grooves?"

Figure 1 from Hendrickx et al., 2015

Without understanding the distinctions between subtle anatomical differences in different taxa, how are we to find out if these features are actually taxonomically important? A quick example from the Morrison Formation. Here in western Colorado we have basically two relatively common large theropods from the Morrison: Allosaurus and Ceratosaurus. Skeletal remains of Allosaurus, including teeth, seem to dominate in the Morrison making up 3/4 of all the theropod remains (Foster, 2007). Teeth attributed to Ceratosaurus do turn up in the field, however, and are usually distinguished by the presence of ridges near their bases. Now that we have Hendrickx et al.'s paper, we can go into a bit more depth. We can say, for instance, that the teeth attributed to Ceratosaurus have basal fluting, and these flutes are not seen in the contemporaneous Allosaurus. So this may help us distinguish between these teeth in the field and keeps us from mistaking Ceratosaurus teeth (with their flutes) with wrinkled or ornamented teeth (or tooth fragments).

The description of Ceratosaurus teeth by previous authors, however, has been lacking in detail and confusing, often using different terms for the same anatomical feature. As Hendrickx et al. note, having their framework in place will help facilitate such a description and they specifically mention Ceratosaurus as being in need of such a redescription. Hopefully such a project will be forthcoming. This topic will also be the focus of my next blog post!

Going forward I am hoping to see a theropod-wide tooth catalog. While Hendrickx et al. do point out that teeth are quick to change, evolutionarily speaking, to changes in diet and feeding behavior, they also note the taxonomic utility of teeth. While many theropod teeth can't be narrowed down to a genus or species, being able to address higher-level taxonomic questions with teeth is important. In addition, some taxa appear to have diagnostic dental modifications. Doing systematic studies and descriptions of theropod teeth may yield more information on what characters are taxonomically useful and potentially add autapomorphies to established genera.

My biggest complaint is that the authors did not examine what a theropod tooth is. They identify problems with past work, the utility of teeth, and the need for a framework but there is no way to determine if this framework is applicable to a given tooth. Obviously for teeth attached to theropod jaws this isn't a problem, but the majority of the dental fossil record for archosaurs consists of isolated shed teeth. While workers in the Cretaceous and Jurassic strata have this problem to a lesser degree (though it is possible that some crocodylomorphs developed similar tooth morphologies), those of us working in the Triassic are confronted with a host of dental convergences! One need look no further than the saga of Revueltosaurus to find examples of teeth that look similar between widely divergent clades. In the Triassic there are plenty of carnivorous reptiles, many with laterally compressed teeth. While in truth the terms developed by Hendrickx et al. (2015) are likely to be broadly applicable, a brief discussion of what synapomorphies exist among the dentition of theropods would have been appreciated, so that those of us working under all that overburden could sort our rauisuchian teeth from our dinosaur teeth just a little easier.

Works Cited

Foster, John. 2007. "Allosaurus fragilis". Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Bloomington, Indiana: Indiana University Press. pp. 170–176

Hendrickx, C., Mateus, O. and Araújo, R., 2015. A proposed terminology of theropod teeth (Dinosauria, Saurischia). Journal of Vertebrate Paleontology,35(5), p.e982797. 

Wednesday, January 13, 2016


So things have been slow at the pub here for a bit because several changes have occurred since our last post. I will summarize them here quickly!

1.  Gary Vecchiarelli, one of the founders of the Prehistoric Pub, has decided to step down from blogging, at least temporarily. That leaves just me (Rob) onboard as the sole blogger for the Prehistoric Pub. Consequently, posts may come slower than in the past. Be assured, however, that the Pub is not and will not be abandoned. Upcoming topics will be the theropod tooth paper review that was promised to you (and I'm sure you are all anxiously awaiting), as well as coverage of the Utah Friends of Paleontology annual meeting, coming up at the start of April in Moab - more details as that gets closer.

2. At the same time as Gary was departing the Pub, I as undergoing major life changes. I changed jobs and changed states and am now working at museum in Colorado. I love the area and job but the move has left little time for blogging. Now that I am settling in, expect blog posts to resume. I am shooting for two a month (not including this introductory one!) for 2016. One will probably be technical in nature while the other may be a reflection on general trends or topics in paleontology. And since this is the Prehistoric Pub, I will probably throw in a beer post or two throughout the year.

Cheers, and happy 2016 everyone!