Field of Science

Phytosaur Taxonomy Flowchart

I remember sitting down one evening back in 2001 and putting this together. It proceeds through time from left to right. This is why nobody wants to research phytosaur taxonomy!


Rhaetian Magneto-biostratigraphy from the Southern Alps (Italy): Constraints on Triassic Chronology

This is fairly significant as it argues for quite a long Rhaetian Stage of the latest Triassic. If this is correct it means that a sizable portion of the upper part of the Chinle Formation could actually be Rhaetian in age. Not bad considering not too long ago workers were arguing if the Rhaetian was really even applicable outside of the marine realm.

Muttoni, G., Kent, D.V., Jadoul, F., Olsen, P.E., Rigo, M., Galli, M.T., and A. Nicora. 2009. Rhaetian magneto-biostratigraphy from the Southern Alps (Italy): Constraints on Triassic chronology. Palaeogeography, Palaeoclimatology, Palaeoecology. doi: 10.1016/j.palaeo.2009.10.014.

ABSTRACT: New Late Triassic-earliest Jurassic magneto-biostratigraphic data have been obtained from three overlapping sections in the Southern Alps, Italy (Costa Imagna, Brumano, Italcementi Quarry), comprised of ~ 520 m of shallow marine carbonates outcropping in stratigraphic continuity. Characteristic magnetic components of presumed depositional age record a sequence of 9 normal and reverse polarity magnetozones (as defined by at least three stratigraphically superposed samples) linked by conodont and palynofloral evidence from this study and the literature to Rhaetian to Triassic–Jurassic boundary age. This represents a significantly larger number of polarity zones than previously recognized in more condensed
Rhaetian sections from the literature, and by inference represents more time. These data are placed in a broader Late Triassic temporal framework by means of correlations to published magneto-biostratigraphic data from the Tethyan marine Pizzo Mondello section and the Newark astronomical polarity time scale (APTS). This framework is consistent with a position of the
Norian–Rhaetian boundary (as defined at Brumano and Pizzo Mondello by the first appearance of Misikella posthernsteini) within Newark magnetozones E17r–E19r in the ~ 207–210 Ma time interval, in basic agreement with the position originally estimated in the Newark using pollen biostratigraphy (E18 at 208–209 Ma). This framework is also consistent with the position of
the Triassic–Jurassic boundary interval (placed at Italcementi Quarry at the acme of Kraeuselisporites reissingeri coincident with a negative carbon isotope excursion) correlative to just above Newark magnetozone E23r and just below the oldest CAMP lavas dated at ~ 202 Ma. Hence, we estimate the duration of the Rhaetian to be ~ 5.5–8.5 Myr (or even longer if the
Triassic–Jurassic boundary is instead placed above the negative carbon isotope excursion as at Kuhjoch, which is the designated GSSP for the base of the Hettangian), and encompassing 9 magnetozones. This duration contrasts with a duration of ~ 2 Myr and only ~ 4 magnetozones in several alternative published magneto-biostratigraphic schemes.

Just In Case You Missed This One

This came out about three weeks ago in PLoS ONE. Pretty cool study showing how different types of dinosaurs would negotiate a particularily difficult terrain.

Wilson, J. A., Marsicano, C. A., and R. M. H. Smith. 2009. Dynamic Locomotor Capabilities Revealed by Early Dinosaur Trackmakers from Southern Africa. PLoS ONE 4(10): e7331. doi:10.1371/journal.pone.0007331.

ABSTRACT

Background

A new investigation of the sedimentology and ichnology of the Early Jurassic Moyeni tracksite in Lesotho, southern Africa has yielded new insights into the behavior and locomotor dynamics of early dinosaurs.

Methodology/Principal Findings

The tracksite is an ancient point bar preserving a heterogeneous substrate of varied consistency and inclination that includes a ripple-marked riverbed, a bar slope, and a stable algal-matted bar top surface. Several basal ornithischian dinosaurs and a single theropod dinosaur crossed its surface within days or perhaps weeks of one another, but responded to substrate heterogeneity differently. Whereas the theropod trackmaker accommodated sloping and slippery surfaces by gripping the substrate with its pedal claws, the basal ornithischian trackmakers adjusted to the terrain by changing between quadrupedal and bipedal stance, wide and narrow gauge limb support (abduction range = 31°), and plantigrade and digitigrade foot posture.

Conclusions/Significance

The locomotor adjustments coincide with changes in substrate consistency along the trackway and appear to reflect ‘real time’ responses to a complex terrain. It is proposed that these responses foreshadow important locomotor transformations characterizing the later evolution of the two main dinosaur lineages. Ornithischians, which shifted from bipedal to quadrupedal posture at least three times in their evolutionary history, are shown to have been capable of adopting both postures early in their evolutionary history. The substrate-gripping behavior demonstrated by the early theropod, in turn, is consistent with the hypothesized function of pedal claws in bird ancestors.

Proof! Dinosaurs and People Co-existed!

Now I've seen it with my own two eyes, a place where dinosaurs and humans co-habitate. Here is a close-up of part of the village.

Notice the crude stone construction and lack of straight lines and 90 degree angles.

Here is one of the dinosaurs, a large 'brontosaur' with some kind of transport device on its back. Actually the dinosaur is the transport device.


Here is one of the 'human' inhabitants. Notice the primitive feature of on three digit on the pes...and a seriously large snozolla.



Here is a human powered mechanical transport.


Some kind of primitive service station. Fossils using fossil fuels. Ironic!



Watch out for the active volcano (presumably Mesozoic) and the large pterosaur! I wonder what the pterosaurs eat here?

Ah Ha! Question answered. Better watch the kids in the open.


Or maybe this is more appropriate? What a menu. I can't believe the humans in this place eat dinosaur meat. What more proof do you need for their co-existance?

They have giant snakes too! This place is not the safest little town.


At least some slightly modern technology.


For those of you who have not seen one of these places, it is a Bedrock Village, one of two small little theme parks built in the U.S. in the 1960s and based on the TV show, The Flintstones. This one in in Valle, Arizona, about 25 miles south of the Grand Canyon. The is another in South Dakota. The one in Arizona is a bit hokey, but my kids really enjoyed it, especially climbing through the giant snake, which is actually a tunnel. The show was primetime TV in the early 1960s and reruns through my childhood, a staple of Saturday morning cartoons. I wonder if they are still on the air?

I remember hearing somewhere that The Flintstones represent a large percentage Americans' only experience with 'prehistoric life' and of course it shows co-habitation of humans and dinosaurs mixed with 'stone age' versions of modern technology, which many bought into. They should have put a disclaimer at the end of each show that it is pure fiction and does not depict accurate events in life history.

End of Blogpost Disclaimer: If you have gotten this far and still believe that dinosaurs and humans did indeed co-exist you need to do yourself a big favor. Go down to your local Community College and take a Historical Geology class (and read this post). Please do pay attention, you won't regret it. Yabba-Dabba-Doo.

Fruitadens Paper Available Online From Royal Society Publishing

In case you are not aware, the full text and PDF files of the paper on Fruitadens, the new diminutive heterodontosaurid from North America, are available for download here. Don't forget the supplemental data files.

New Diminutive Heterodontosaur from North America

Good to see this out. Available online today is a new paper describing a new heterodontosaurid, Fruitadens haagarorum, from the Late Jurassic on Colorado, U.S.A.


There are lots of cool things about this critter:

1) Small size. Specimens of Fruitadens have a maximum body length of about 75 cm, making it the smallest known ornithischian. Histological work was done to determine the relative age of the specimens. It is estimated that the largest individual was about 4-5 years old at death, but had already slowed down its growth as is seen in sub-adult and adult non-avian dinosaurs.

2) Age. The specimen is Late Jurassic, making it one of the youngest known heterodontosaurids. Only Echinodon from the Early Cretaceous of England is younger. Interestingly both Echinodon and Fruitadens have small adult sizes, but it is possible to differentiate the two.

3) Plesiomorphic dentition. Fruitadens differs from older heterodontosaurs in possessing less sophisticated craniodental adaptations, thus was probably more of a generalist feeder. The authors believe that this adaptation, as well as small size, allowed the group to survive into the Late Triassic and Early Cretaceous. Also cool is that it seems to have regularly undergone tooth replacement, which is unknown in most other heterodontosaurs.


4) Theropod-like femur. One feature of Fruitadens that I find interesting is that the femur closely resembles that of theropods like Dilophosaurus and is very unlike that of ornithischians. Richard Butler assures me that the material represents a single taxon so this is an interesting characteristic. I often like to play devil's advocate and claim that there are no Triassic ornithischians (not even Pisanosaurus) despite a wealth of saurischians, and although I've been assured over and over by dinosaur workers that the saurischian line could not have given rise to the ornithischians, I always find synapomorphies like this (basal ornithischian with saurischian-like characters) of great interest. Hey, someones got to keep stirring the pot or we'll get too complacent.

4) Biogeography. Fruitadens is from the Upper Jurassic Morrison Formation of Colorado. This is the first described heterodontosaurid from North America. As it is from the Brushy Basin Member it was a contemporary of the classic dinosaurs such as Allosaurus, Camarasaurus, Stegosaurus, and Diplodocus.

Overall another great find. They just keep coming. Read more here and here.

Butler, R. J., Galton, P. M., Porro, L. B., Chiappe, L. M., Henderson, D. M., and G. M. Erickson. 2009. Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America. Proceedings of the Royal Society B. doi:10.1098/rspb.2009.1494.

Abstract-The extremes of dinosaur body size have long fascinated scientists. The smallest (<1>Fruitadens haagarorum, from the Late Jurassic of western North America that rivals the smallest theropods in size. The largest specimens of Fruitadens represent young adults in their fifth year of development and are estimated at just 65–75 cm in total body length and 0.5–0.75 kg body mass. They are thus the smallest known ornithischians. Fruitadens is a late-surviving member of the basal dinosaur clade Heterodontosauridae, and is the first member of this clade to be described from North America. The craniodental anatomy and diminutive body size of Fruitadens suggest that this taxon was an ecological generalist with an omnivorous diet, thus providing new insights into morphological and palaeoecological diversity within Dinosauria. Late-surviving (Late Jurassic and Early Cretaceous) heterodontosaurids are smaller and less ecologically specialized than Early (Late Triassic and Early Jurassic) heterodontosaurids, and this ecological generalization may account in part for the remarkable 100-million-year-long longevity of the clade.

Finally! Aetosaurs in National Geographic Magazine

The most recent issue of National Geographic has an article titled 'When Crocs Ruled' which mainly focuses on the long evolutionary history of the crocodile lineage and the threats extant crocodylians face today. One highlight of the article is the large two page spread of the Desmatosuchus mount from Petrified Forest National Park. It's a nice photo that almost makes me forget about the erroneous armor reconstruction (Unfortuntely, we'll need to remold and cast the whole thing to fix). I'm not as forgiving with the term "croc forerunner" in the title, because as we know aetosaurs were never crocodiles and their lineage did not give rise to the group. Still, I'm thrilled to see an aetosaur displayed prominently in National Geographic (but why not the cover?)

There is also a time line with some great reconstructions that gives props to Triassic forms such as Effigia, Postosuchus, and Proterosuchus. It also gives a good representation of crocodylomorph diversification through the later Mesozoic and Tertiary, something that often gets overshadowed by the dinosaurs, birds, and mammals.

There is also a secondary article by Paul Sereno titled "Strange Crocs of the Sahara", which again tries to demonstrate the great diversity in forms. Although I don't really care for terms such as 'RatCroc', 'DogCroc', and 'DuckCroc' they do seem to get the point across.

Latest Literature - Distribution of Supernumerary Carinae in Archosauriforms

Beatty, B.L., and A.B. Heckert. 2009. A large archosauriform tooth with multiple supernumerary carinae from the Upper Triassic of New Mexico (USA), with comments on carina development and anomalies in the Archosauria. Historical Biology 21:57-65. DOI: 10.1080/08912960903154511.

Abstract-Here we report a tooth of a large archosauriform from the Upper Triassic of New Mexico, USA that displays developmental anomalies of carina formation. This tooth has two supernumerary carinae, both on the lingual side of the tooth. Previously, carina anomalies of this sort were primarily known from theropod dinosaurs, but always from the labial surface. Integrating this specimen into a reassessment of the published accounts of carina anomalies in other fossil diapsids reveals that supernumerary carinae are more widespread throughout Archosauriformes than previously reported. Our interpretation of this developmental anomaly highlights the present lack of understanding of tooth development in archosaurs, particularly carina formation, and suggests that crown morphology development in archosauriforms may be constrained differently than it is in mammals. This developmental constraint may explain the differences observed between the complexity found in mammal and archosauriform cusp morphology.

More Triassic Repeat Photography - Ned Colbert (AMNH) at the Petrified Forest in 1946

In 1946 the American Museum of Natural History initiated fieldwork in the Chinle Formation of Arizona. Led by Edwin (Ned) Colbert, the goal of the expedition was to add to our knowledge of Triassic vertebrates and expand the museum's collection of Chinle Formation fossils. The previous year Colbert had travelled to the Petrified Forest with Charles L. Camp to check out Camp's old localities from the 1920s. This lead to a full blown, successful field season in 1946 (several amazing stories from this work can be found in one of Colbert's autobiographies - Digging into the Past). Set to return in 1947, Colbert never made it because on the way to the Petrified Forest he stumbled upon the huge deposit of vertebrates at the Coelophysis Quarry at Ghost Ranch, New Mexico. As a side note: he did return to the park briefly in 1947 to take part in the first ever Society of Vertebrate Paleontology field conference (see Camp et al., 1947; Nesbitt and Parker, 2005).

Fantastically, Colbert shot many rolls of Kodachrome (color) slide film of his Triassic work in 1946 and 1947. The 1946 set was purchased by the Petrified Forest shortly afterwards and some of these are still in the collections to this day. Since 2001 I have been actively trying to relocate two of the sites, the first a large bed of fresh water clams that AMNH staff proclaimed the greatest deposit of Triassic freshwater clams (Unionids) ever! Actually dozens of these sites occur throughout the park but when first discovered this was a big deal.

1946 shot of AMNH jeep parked near clam bed.


2009 photo of same site

The second site was where Colbert and crew collected the skull of a pseudopalatine phytosaur. This site was particularly intriguing as in the photo the outcrop being excavated looks very much like strata of the Blue Mesa Member. If this site really is in the Blue Mesa Member, this would represent a very low occurrence of a pseudopalatine phytosaur.


1946 photo of phytosaur skull excavation.

2009 photo of same site.

The park also has a very old map where Charles Camp's localities as well as those of National Park staff had been plotted. Colbert's 1946 sites were added to this map. Unfortunately, numerous visits to where these two sites were plotted failed to match up the photographs. By 2009 I had eliminated all possibilities except for one area of badlands south of a place called Billing's Gap. This past summer the interns and I were finally able to precisely relocate these sites. Interestingly both were situated very close to each other geographically and over 1.5 miles away from where they had been mapped! Also of interest was that the sites were in the upper portion of the Sonsela Member, thus no low occurrence of a pseudopalatine.

How fortunate we are that past researchers such as Colbert photographed their work (and he did it in color in 1946!). Even with dots on a map (and GPS coordinates) photos are indispensable for relocating sites and determining stratigraphic position of historic specimens. Nowadays with digital photography, there is no excuse for researchers not to photodocument every single site where fossils are collected.

For those interested in historic documentation of paleontology I encourage you to please check out the 2005 article I did with Sterling Nesbitt for a SVP field trip that year. It includes many previously unpublished photos from the 1947 field conference which was attended by notable VP'ers such as Romer, Gregory, Simpson, Colbert, etc... You can order the entire volume (with papers on the vertebrate faunas and plants of the Moenkopi and Chinle Formations from the Arizona Museum of Natural History.

REFERENCES

Camp, C.L., Colbert, E.H., McKee, E.D., and S.P. Welles. 1947. A guide to the continental Triassic of Northern Arizona. Plateau 20:1-8.

Nesbitt, S.J., and W.G. Parker. 2005. The 1947 Society of Vertebrate Paleontology Triassic fieldtrip, then and now, and its significance to Triassic vertebrate paleontology. Mesa Southwest Museum Bulletin 9:1-12.

Limusaurus and Bird Digit Identity

For those of you who may have missed this or are not subscribed to the Dinosaur Mailing List, this is a comment left for my recent post on Limusaurus, the strange new beaked ceratosaur from China. One of the purported significances of this specimen is that it shed light on the debate on dinosaur digit homologies. As you can see below, this new article is a response to that claim.

A. Vargas has left a new comment on your post "Limusaurus inextricabilis, a Bizarre Beaked Cerato...":

Vargas, AO, Wagner GP, and Gauthier, JA. Limusaurus and bird digit identity.

hdl.handle.net/10101/npre.2009.3828.1

Here is our response to the Limusaurus paper. It was recently rejected by nature, not for any technical reason but because it was considered not to be of sufficient interest/importance.
We have uploaded it at the nature precedings citable archive, because we think it is important there is a quick and citable reply that unlike Xu’s proposal, is consistent with the view of the larger community of theropod paleontologists, namely, that tetanuran digits still are I, II, III. We are preparing a longer paper on this topic.

The First Morphological Evidence for Turtles as Archosauromorphs

Bhullar, B.S., and G.S. Bever. 2009. An archosaur-like laterosphenoid in early turtles (Reptilia:Pantestudines). Breviora 518:1-11. doi: 10.3099/0006-9698-518.1.1

Abstract: Turtles are placed with increasing consistency by molecular phylogenetic studies within Diapsida as sister to Archosauria, but published gross morphology–based phylogenetic analyses do not recover this position. Here, we present a previously unrecognized unique morphological character offering support for this hypothesis: the presence in stem turtles of a laterosphenoid ossification identical to that in Archosauriformes. The laterosphenoid is a tripartite chondrocranial ossification, consisting of an ossified pila antotica, pila metoptica, and taenia medialis + planum supraseptale. It forms the anterior border of the exit for the trigeminal nerve (V) and partially encloses the exits for cranial nerves III, IV, and II. This ossification is unique to turtles and Archosauriformes within Vertebrata. It has been mistakenly dismissed as anatomically dissimilar in these two groups in the past, so we provide a complete description and detailed analysis of correspondence between turtles and Archosauriformes in each of its embryologically distinct components. A preliminary phylogenetic analysis suggests other potential synapomorphies of turtles and archosaurs, including a row or rows of mid-dorsal dermal ossifications.

Thanks to Randall Irmis for bringing this to my attention.

I Think the Jet Lag is Mostly Gone

I've been back from England for a few days but really have not had the energy to do too much with my evenings except try to get my sleep schedule back to Arizona time rather than London/Bristol, an 8 hour difference.

This year's SVP meeting was excellent and I totally enjoyed my time in Bristol and in London. While many attendees returned to the states after the meeting I went on to London for three days of work in the sub-basement of the Natural History Museum. I stayed at a neat little bed and breakfast in Parsons Green about six underground stops from the museum, which saved me some cash, and actually enjoyed my commute everyday. After eight hours of non-stop work in the museum, we would take the underground to various places in the city and check out sites such as the Tower of London, Buckingham Palace, Piccadilly Circus, and of course Westminster Abbey. Unfortunately I did not get to go into many of these places due to arriving after hours, but it was still cool to see the outsides. The last day Jeff Martz skipped the museum and went out to see to Victorian dinosaurs at Crystal Palace Park and caught a second copy of William Smith's map of England (we had seen another copy in Bristol), which of course represents the beginnings of geological mapping, stratigraphy, and biostratigraphy. Nightly we would stop at a little pub near our B&B for internet and a pint of Young's Bitter.

The museum was excellent although I admit I spent the majority of my time in the basement and did not really get to see much else. I was mainly studying specimens of the aetosaur Stagonolepis robertsoni which is mostly represented by natural molds in sandstone from the Elgin area of Scotland, and a series of old casts made from these molds. Without these casts it would be almost impossible to study this material and I was pleasantly surprised about how much information is available from them. I also was able to see some phytosaur material collected from Germany in the 1860s and originally described by Hermann von Meyer.

Although my research took up almost all of my time and attention I did sneak a peak at some of the amazing dinosaur material in the collections. It was an honor to look upon some of Gideon Mantell's Iguanodon specimens, and browse through specimens studied by Owen, Huxley, Seeley, Lydekker, and others, and to reminisce about the beginnings of dinosaur paleontology (which all started there). However, as is typical for museum study, there never seems to be enough time to complete your primary research, never mind look at other things in great detail. It is absolutely amazing how many fossils are out there and how many are in venerable institutions such as the Natural History Museum in London. I don't think that even the staff who work there are able to see everything during their careers.