Field of Science

Histological Evidence of Trauma in Dicynodont Tusks

Whitney, M. R., Ting Tse, Y., and C. A. Sidor. 2019. Histological evidence of trauma in tusks of southern African dicynodonts. Palaeontologia Africana 53: 75-80. PDF.

Abstract -
Dicynodonts were a clade of globally-distributed therapsids known for their abundance in the fossil record and for surviving the Permo-Triassic mass extinction. The group had distinctive dental adaptations including a beak and, in many species, paired maxillary tusks. The function of these tusks has long been of interest, yet remains poorly understood.We report here on two instances of unusual morphology in tusk dentine from specimens of: 1) Lystrosaurus from the Karoo Basin of South Africa and, 2) an unidentified dicynodontoid from the Luangwa Basin of Zambia. In both, the cross-sectional shape of the tusk root is lobed and infolded, which histological features suggest is a result of abnormal dentine deposition. We infer that this abnormal morphology is likely the consequence of trauma given its reparative nature and structural similarities to trauma-related morphologies reported in the tusks of modern elephants. This study demonstrates that histological sampling of dicynodont tusks can shed light on the biology of this important clade of therapsids.

Examining Functional Convergence Between Triassic Phytosaurs and Slender-Snouted Crocodylians

A new preprint in PeerJ.

Lemanis R., Jones A.S., Butler R.J., Anderson P.S.L., and E.J. Rayfield. 2019. Comparative biomechanical analysis demonstrates functional convergence between slender-snouted crocodilians and phytosaurs. PeerJ Preprints 7:e27476v1https://doi.org/10.7287/peerj.preprints.27476v1

Abstract - Morphological similarities between the extinct Triassic archosauriform clade Phytosauria and extant crocodilians have formed the basis of long-proposed hypotheses of evolutionary convergence. These hypotheses have informed the reconstructions of phytosaur ecology and biology, including feeding preferences, body mass, soft tissue systems, mating behaviours, and environmental preferences. However, phytosaurs possess numerous cranial apomorphies that distinguish them from modern crocodilians and potentially limit ecomorphological comparisons. Here, we present the first computational mechanical comparison of phytosaur cranial strength to several extant crocodilian taxa using two biomechanical approaches: beam theory and finite element analysis. We demonstrate mechanical convergence between the slender-snouted phytosaur Ebrachosuchus neukami and modern slender-snouted crocodilians. We provide evidence that the phytosaurian premaxillary palate is functionally equivalent to the crocodilian secondary palate. The premaxillary palate is associated with greater resistance to biting induced stress, lower strain energy, higher resistance to bending and torsion, as well as increased performance under tension. In all tests, Ebrachosuchus performed worse than all tested crocodilians, showing higher stress under equivalent loading conditions. These findings have implications for the proposed feeding ecology of slender-snouted phytosaurs and corroborate previous broad assessments of phytosaur ecology based on morphological comparisons to crocodilians; however, we urge caution in overextending those assessments given the current paucity of comparative functional data.

Why are Temnospondyl Skulls Bumpy?

Today Bryan Gee at Temno Talk Blog discusses and evaluates the various hypotheses of why temnospondyl skulls (and other bones) have heavily ornamented, irregular surfaces.

If you missed the link here it is again.

Triassic Park is Temporarily Closed: What Happens at Petrified Forest During a Government Shutdown

[Disclaimer: I am a furloughed Federal employee and this is a personal blog. It is not my intent to take a political side or to make a a political statement here. I am simply explaining what a shutdown is for those who might not understand and its effects on a specific park and program].

On December 22, 2018 funding appropriations for the U.S. National Park Service ended. What does this mean? It means that Congress and the President have not allocated funding to allow the Service to pay its bills and keep functioning. There is a little known law on the books called The Antideficiency Act passed in 1884 that prevents "the incurring of obligations or the making of expenditures in excess of amounts available in appropriations of funds". In other words, U.S. Government agencies cannot spend more money each year than they are appropriated by Congress.

One of the President's and the Congress' main jobs is to develop a budget each year for the functioning of the Federal Government. If they fail to develop, and pass by law, a Federal budget then the Antideficiency Act kicks in after the last day of lawful appropriations expires. This time that occurred at 12:01 EST on December 22, 2018. The Act requires that the Federal Government initiate a shutdown, which includes the furlough of pre-determined "non-essential" staff and the limitation of services.

What is meant by 'non-essential" staff? Basically positions and employees that do not have a health-safety, law enforcement, or cybersecurity role. In National Parks a handful of "essential" staff are kept on the guard the park entrances, and keep up some basic maintenance duties such as water and other utility monitoring. Computer and network monitoring is also provided for. Unfortunately scientific work is not considered essential. It's also important to note that although essential staff are required to work, there is no funding so they do not receive pay for their work time during a shutdown.

Since 1976 there have been 22 funding lapses and shutdowns, three in 2018 including the present one. The current one is now a day short of being the longest in history, 22 days. This shutdown is also different because unlike other shutdowns the National Parks have been kept 'open'. The closure of parks during the 17 day 2013 shutdown was not well received by the public and was considered a black eye for the Obama Administration. The current administration did not want to face this and ordered the parks to stay open, but with the greatly reduced "essential" staff. This has led to resource damage, overflowing toilets, etc... situations now being remedied by volunteers and other actions being taken.

At Petrified Forest National Park in Arizona the park is closed at night and parks with limited hours are allowed to close those areas normally closed for a portion of the day. Because of the vast amounts of petrified wood and how easily it can be removed the main portion of the park is closed to protect these resources. However, as a service to visitors and travelers on Interstate 40 the restaurant and gas station at the north end of the park, run by a permitted concessionaire, remain open.

This has caused a lot of confusion with the public because they see on the news where parks are "open", but don't always realize that only limited services can be offered because there are no staff. So visitor centers and bathrooms are closed at most parks and this is generally unexpected. I highly recommend that anyone planning on visiting a National Park in a shutdown time do some research first to see what is available For example at Petrified Forest the visitor centers are not open, but there are bathroom services. There are also some exhibits and some petrified wood outside of the restaurant. The Grand Canyon is open because it is such a large economic draw for the State of Arizona, that the state is providing the funding to keep some of the basic services operating and some of the park open. Again do some research before visiting and don't expect full services.

The thing that is most significant to regular readers of this blog is that the paleontology program at the Petrified Forest (and other units) is a non-essential service and is temporarily closed. Thus park scientists are unable to go to work. This means fossils threatened by erosion don't get collected and preserved, collected fossils don't get prepared or curated, and research does not get done. Fortunately wintertime is not a major collecting season for us so the first point is not critical. However, planning for the summer field season is usually done now and cannot happen and we fall behind in recruiting student interns and working with other researchers. Even more important the NPS scientists cannot apply for external funding sources (e.g., NSF), so we rely on internal grant funding. This year grant proposals were due in January 11, but this year none will be submitted by the deadline. What this means for future grant funding is uncertain.

Another thing to realize is that a lot of research in National Parks is done by permitted outside institutions and with a shutdown that work cannot be done, permits and fieldwork are cancelled or postponed. This is not only paleontology but also ecology, archaeology, etc... The park maintains several air quality monitoring stations that require weekly upkeep and data collection. Weeks of non-collection cause sizeable gaps in data that can render a whole year of data unusable. Fortunately this year there was no outside paleontology research work scheduled for this time, although in the 2013 shutdown several research groups were affected. Since that time we try to warn groups not to schedule trips that correspond to funding end periods.

Again my purpose here is not to pass judgment on political reasons for this or any other shutdown. I know that a lot of paleontology enthusiasts don't necessarily understand how government shutdowns work and what effects they can have on our scientific work.  I hope I have sufficiently explained the process. Those of us who have chosen civil service understand that our work can be temporarily disrupted by funding lapses. Regardless when the park reopens we will get back to our duties of caring for the park fossils and researching their significance for the public and the scientific community. I'm confident that our law enforcement who have to work during the shutdown are doing a great job protecting park resources and explaining this situation to any park visitors. They deserve a lot of thanks.


Extinction and the Rise of Dinosaurs - What Will the Microvertebrates Tell Us?

Brian Switek has a great year end article (based mainly on the recent Allen et al., study in Palaeontology) regarding the loss of most pseudosuchian groups in the end-Triassic extinction and discussion on why the dinosaurs were mostly unaffected.

According to their findings body size was not a factor; however, there are not too many data regarding Middle Triassic - Early Jurassic microfaunas. My intern, colleague and Virginia Tech grad student Ben Kligman is adding to this information. Ben started a couple of years ago at Petrified Forest National Park looking at a new microsite in the Blue Mesa Member of the park. This unit and roughly the same horizon had been the subject of several previous microvertebrate studies that despite being nearly two decades apart had generated roughly the same results, a lot of teeth and scales that could only be assigned to broad taxonomic levels. Thus, I was not enthusiastic about this at first. However, Ben tackled this new site with gusto and developing a new sampling technique with the help of PEFOs lead preparator and curator Matt Smith, very quickly built a sample of over 100 different morphotypes. Even more important this new technique allowed preservation of relatively complete jaw elements.

<i>Palacrodon browni</i> from the Chinle Formation of Arizona.
From Kligman et al 2018. Acta Palaeotologica Polonica 63(1).


Ben already has several publications about new these finds (Kligman et al., 2017; Kligman et al., 2018) and several more in the works. Furthermore, this research won the Student Poster Prize at the 2018 Society of Vertebrate Paleontology meeting. Ben is now sampling a wider stratigraphic range of sites and his work will help us further understand the effects of the end-Triassic extinction.

New Blog TemnoTalk: A Blog About All Things Temnospondyl

Introducing a new blog by my friend and colleague Bryan Gee from the University of Toronto. Since his first find of half of a metoposaur skull in Petrified Forest National Park quite a few years back now Bryan has been obsessed with the fossil record of temnospondyls, a group with constituents that are not always well studied (e.g., Late Triassic North American metoposaurids).

Bryan embarked on a series of discoveries at the Petrified Forest that kindled a badly needed interest in these forms and has resulted in quite a few recent publications (Gee et al., 2017; Gee and Parker, 2017; Gee and Parker, 2018) and an upcoming paper reexamining the anatomy and taxonomy of the metoposaurid <i>Anaschisma</i>.  Bryan is one of the most prolific writers I have ever seen and has published a number of papers now as a graduate student (see his Google Scholar page here). I look forward to his blogging and I've added the link to the Chinleana blogroll.