Field of Science

Paleohistology of Rauisuchid Osteoderms

Yes, I am still in Argentina. I'd planned on posting a little more, especially since I visited Ischigualasto National Park and spent some hours prospecting in the Ischigualasto Formation (it did not disappoint) but I've been up to my eyeballs in aetosaur specimens and trying to keep myself fed (meals take a long time here), so forgive me. Meanwhile here is a paper I've been waiting on for awhile now regarding osteoderm histology of rauisuchids with comparisons to some other archosaur groups as well.

Scheyer, T. M. and J. B. Desojo. 2011. Palaeohistology and external microanatomy of rauisuchian osteoderms (Archosauria: Pseudosuchia). Palaeontology (advance online publication) DOI: 10.1111/j.1475-4983.2011.01098.xhttp://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2011.01098.x/abstract

Abstract - The presence of postcranial dermal armour is plesiomorphic for Archosauria. Here, we survey the external microanatomy and histology of postcranial osteoderms (i.e. dorsal paramedian and caudal osteoderms) of rauisuchians, a widely distributed assemblage of extinct predatory pseudosuchians from the Triassic. The osteoderms of eight rauisuchian taxa were found to be rather compact bones, which usually lack significant bone remodelling or large areas of cancellous bone. The presence of highly vascularized woven or fibrolamellar bone tissue deposited in the core areas indicates higher growth rates during earlier life stages, whereas a more compact parallel-fibred bone matrix indicates reduced growth rates in later development. This pattern of change corroborates earlier studies on long bone histology. With the exception of a bone tissue found in the sample of Batrachotomus kupferzellensis, which might be the result of metaplastic ossification, the general mode of skeletogenesis is comparable with intramembraneous ossification. The lack of cancellous bone tissue and remodelling processes associated with bone ornamentation, as well as the predominantly intramembraneous mode of ossification, indicates that rauisuchian osteoderm formation differs profoundly from that of the osteoderms of the only extant pseudosuchian lineage, the crocodylians.

First Evidence of Aetosaurs from the Plateosaurus Quarry of Germany

Matzke, A. T., and M. W. Maisch. 2011. The first aetosaurid archosaur from the Trossingen Plateosaurus Quarry (Upper Triassic, Germany). Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen (advance online publication) DOI: 10.1127/0077-7749/2011/0203http://www.ingentaconnect.com/content/schweiz/njbgeol/pre-prints/0203

Abstract -Two associated cervical paramedian osteoderms and one isolated paramedian osteoderm of an aetosaur from the famous Trossingen Plateosaurus Quarry are described. They represent the first evidence of aetosaurs from Trossingen as well as the stratigraphically youngest remains of this group from Germany. Therefore, the Trossingen assemblage consists now of four species level taxa. Hitherto only three species level taxa were known from this quarry. Plateosaurus longiceps and Proganochelys quenstedti from complete specimens as well as one tooth of cf. Liliensternus. The finds indicate that more small- to medium-sized taxa may be present in the Trossingen Quarry.

New Capitosaur from the Middle Triassic of Spain

I'm still in Argentina. In San Juan now at the IV Congreso Latinamericano Paleontologia de Vertebrados. Yesterday was the early theropod symposium and many crocodylomorph talks. The basal archosaurs symposium starts today and runs through tommorrow. Etiquette precludes me from directly posting on details of the talks; however, I may find some willing to let me share.  In the meantime here is a new temnospondyl paper:

Fortuny, J., Galobart, À, and C. De Santisteban. 2011. A New Capitosaur from the Middle Triassic of Spain and the Relationships within the Capitosauria. Acta Palaeontologia Polonica 56:553:556. http://www.bioone.org/doi/abs/10.4202/app.2010.0025

Abstract - Capitosaurs were the largest and homogeneous group of Triassic temnospondyl amphibians with cosmopolitan distribution. However, their interrelationships are debated. The first capitosaur cranial remains found in the Iberian Peninsula were assigned to Parotosuchus; herein, a re-description of this material, together with information on other remains recovered from the same site, enables us to classify them as a new genus: Calmasuchus acri gen. et sp. nov. (Amphibia: Temnospondyli) from the early-to-middle Anisian (early Middle Triassic). This capitosaur had a combination of plesiomorphic and non-plesiomorphic characters, such as posterolaterally directed tabular horns, paired anterior palatal vacuities, and unique morphology of the lower jaw. By cladistic analysis, we propose a new phylogeny for the monophyletic capitosaurs. In the analysis, Capitosauria is supported by seven synapomorphies. Wetlugasaurus is the most basal member of the clade. The score of the Russian taxon Vladlenosaurus alexeyevi resulted in a clade including Odenwaldia and the latter taxa. The Madagascarian Edingerella is the sister taxon of Watsonisuchus. Finally, Calmasuchus acri, the new taxon described here, appears as a more derived form than Parotosuchus. The new genus is the sister taxon of the CyclotosaurusTatrasuchus and EryosuchusMastodonsaurus clades.

Candelariodon barberenai, a New Cynodont from the Middle Triassic of Brazil

Oliveira, T. V., Schultz, C. L., Soares, M. B., and C. N. Rodrigues. 2011. A new carnivorous cynodont (Synapsida, Therapsida) from the Brazilian Middle Triassic (Santa Maria Formation): Candelariodon barberenai gen. et sp. nov. Zootaxa 3027: 19–28.

Abstract - A new small cynodont, Candelariodon barberenai gen. et sp. nov., from the Middle Triassic of Brazil (Santa Maria Formation) is reported. The new taxon is represented by a partial mandible having some complete teeth. The morphology of the dentary and splenial is similar to other carnivorous cynodonts, except for the absence of the angular process of the dentary. The anterior-most lower teeth are slightly expanded buccolingually with a tall and posteriorly curved main cusp and one or two accessory cusps. The posterior-most preserved lower postcanine, however, has lingual and buccal rows of cusps, each formed by four anteroposteriorly aligned cusps, separated by a shallow basin. This tooth resembles the posterior-most lower teeth of Aleodon Crompton 1955 from the Middle Triassic of Tanzania, but the anterior-most teeth of Candelariodon and Aleodon are essentially different. In this context, the phylogenetic relationships of the new taxon remain unclear until the discovery of more informative material.

Day 1 - Buenos Aires - Museo Argentino de Ciencias

I'm now in Buenos Aires having arrived yesterday. I was fortunate to have the same flight as Casey Holliday (although he was bumped up to first class!) so we travelled together the first day here. Our first day was spent at the Museo Argentino de Ciencias Naturales (MACN) with me looking at aetosaur skulls (courtesy of Dra. Julia Desojo) and Casey looking at some crocodylian skulls. Had an energetic lunch with Julia and Oliver Rauhut (who was also visiting).  Here is a photo of Julia and Oliver in Julia's office trying to work on some research despite our repeated intrusions and partaking of the local beverage of choice.



Here is a photo of the Museo Argentina de Ciencias Naturales.


Beautiful skull of the aetosaur Neoaetosauroides engaeus.



Day 2: Intense aetosaur discussion with Julia Desojo and examination of a new taxon she is proposing.

IV Congresso Latino-Americano de Paleontologia de Vertebrados

I'm off to San Juan Argentina to attend and present two talks at the IV Congresso Latino-Americano de Paleontologia de Vertebrados. I'm also planning to do some aetosaur research in Buenos Aires and San Miguel de Tucuman. An added bonus is a field trip to Ischigualasto National Park.  This years meeting promises to be well attended with lots of great talks. In addition there are two symposia (Triassic and Jurassic theropods and basal archosaurs) heavy on Triassic research. You can read more about the meeting here:

http://www.congresopaleo.com.ar/bin-debug/congreso.html

Hopefully I'll see many of you there!

New Deep Bodied Vertebrate from the Middle Triassic of China

Thanks to Ben Creisler for pointing this new paper out to me. I know the post title is slightly misleading, but how many of you would have come here if I had put "deep-bodied fish"? ;)

This is very well preserved specimen and pretty cool, admit it. :).

Xu, G. -H., and F.- X., Wu. 2011. A deep-bodied ginglymodian fish from the Middle Triassic of eastern Yunnan Province, China, and the phylogeny of lower neopterygians. Chinese Science Bulletin online first. DOI: 10.1007/s11434-011-4719-1. 

 

Abstract - The Ginglymodi are a group of ray-finned fishes that make up one of three major subdivisions of the infraclass Neopterygii. Extant ginglymodians are represented by gars, which inhabit freshwater environments of North and Central America and Cuba. Here, we report the discovery of well-preserved fossils of a new ginglymodian, Kyphosichthys grandei gen. et sp. nov., from the Middle Triassic (Anisian) marine deposits (Guanling Formation) in Luoping, eastern Yunnan Province, China. The discovery documents the first known fossil record of highly deep-bodied ginglymodians, adding new information on the early morphological diversity of this group. The studies of functional morphology of extant deep-bodied fishes indicate that Kyphosichthys is not a fast swimmer but has a good performance in precise maneuvering, representing a morphological adaptation to structurally complex habitats (e.g. thick macrophyte beds, rocky areas, or coral reefs), which differs from the other members of this group. A cladistic analysis with the new fish taxon included supports the hypothesis that the Ginglymodi are more closely related to the Halecomorphi than to the Teleostei. Represented by Felberia, Kyphosichthys, and Dapedium, a highly deep and short fish body type has independently evolved at least three times in the stem-group neopterygians, ginglymodians, and basal teleosts within the lower neopterygians of the Triassic.

Mesozoic Shark Nurseries - Evidence from the Triassic of Kyrgyzstan

Very cool paper, especially since the Chinle Formation in Petrified Forest National Park also contains shark egg capsules (Palaeoxyris). The Petrified Forest specimens are the only ones known from North America.

Fischer, J., Voigt, S., Schneider, J. W., Buchwitz, M., and  & S. Voigt. 2011. A selachian
freshwater fauna from the Triassic of Kyrgyzstan and its implication for Mesozoic shark nurseries. Journal of Vertebrate Paleontology 31:937-953.

Abstract - Habitat partitioning and site fidelity of spawning grounds are well-documented phenomena in extant selachians, but little is known about the reproductive strategies of their fossil relatives. Here we describe the selachian fauna of the Middle to Late Triassic Madygen Formation in southwestern Kyrgyzstan, Central Asia, based on several dozen tooth crowns and egg capsules. The material is assigned to three new taxa: Lonchidion ferganensis, sp. nov., and Palaeoxyris alterna, sp. nov., being teeth and egg capsules of hybodontid sharks, and Fayolia sharovi, sp. nov., being egg capsules of probable xenacanthids. Teeth of L. ferganensis, sp. nov., were almost exclusively found in pelecypod-rich shallow lacustrine mudstones and belong to juvenile individuals. Oxygen and strontium isotope data of tooth enameloid indicate freshwater conditions of the ambient water at the time of tooth mineralization. The egg capsules are common findings in near-shore lake deposits as well. Considering the mass co-occurrence of juvenile teeth and egg capsules in the study area, we propose that hybodontid/ xenacanthid sharks recurrently occupied littoral zones of the Madygen lake for spawning. The small number of full-grown individuals points to habitat partitioning of juveniles and adults wherefore the study site is interpreted as a shark nursery. The oviposition strategies inferred from this fossil example are remarkably similar to those of modern sharks, suggesting that the reproductive patterns seen in extant sharks originated well before the Cenozoic.
http://dx.doi.org/10.1080/02724634.2011.601729

LACM Dinosaur Institute Hiring Paid Intern

Dinosaur Institute hiring paid intern. Please pass along.

Feel free to pass this along to any interested parties/mailing lists.

The Dinosaur Institute at the Los Angeles County Natural History Museum is currently seeking applicants for Proyecto Dinosaurios, a 1-year paid internship designed to encourage under-represented students to pursue careers in the geosciences. In order to apply, students must 1) currently be enrolled in a 2-yr community or junior college, 2) be a minority, preferably hispanic, 3) be eligible to work in the US (citizen or permanent resident), and 4) be interested in the sciences.

It's short notice, but if you know of any potential applicants please pass the information on to them. The application is due Sept 16, so passing this along soon would be greatly appreciated. Feel free to contact me (theropods@gmail.com) with any questions or interest and I'll pass it on.

-JTH
The Dinosaur Institute does some work in the Chinle at Petrified Forest as well as many other places.  Maybe we'll see the sucessful applicant here for a little bit.

New Capitosaur from the Early Triassic of Poland

Sulej, T., and G. Niedźwiedzki. in press. A new large capitosaur temnospondyl amphibian from the Early Triassic of Poland. Acta Palaeontologica Polonica available online 09 Sep 2011 doi:10.4202/app.2011.0025
 

Abstract - The Early Triassic record of the large capitosaur amphibian genus Parotosuchus is supplemented by new material from fluvial deposits of Wióry, southern Poland, corresponding in age to the Detfurth Formation (Spathian; late Olenekian) of the Germanic Basin. The skull of the new capitosaur shows an “intermediate” morphology between that of Parotosuchus helgolandicus from the Volpriehausen - Detfurth Formation (Smithian; early Olenekian) of Germany and the slightly younger P. orenburgensis from European Russia. These three species may represent an evolutionary lineage that underwent a progressive shifting of the jaw articulation anteriorly. The morphology of the Polish form is distinct enough from other species of Parotosuchus to warrant erection of a new species. The very large mandible of [new taxon name removed until formal publication] indicates that this was one of the largest tetrapods of the Early Triassic. Its prominent anatomical features include a triangular retroarticular process and an elongated base of the hamate process.

Petrified Forest National Park Adds 26,000 Acres to Protect Triassic Fossils

Some of the big news today in northeastern Arizona is the announcement that Petrified Forest National Park has purchased over 26,000 acres of private land as part of its ongoing expansion effort authorized by Congress in 2004. These new lands (the Paulsell or Hatch Ranch) mostly lie to the east of the existing park, but also includes about 8 square miles west of the park boundary. These lands are rich in fossil resources and have been worked in the past by the University of California (Berkeley), the Smithsonian, the American Museum of Natural History, and most recently by the University of Texas at Austin. The park hopes to continue these partnerships and is excited regarding the information this land acquisition will provide regarding the paleontology of the Late Triassic. Furthermore, the are strata cropping out on these lands that are not exposed within the old park boundary, significantly enhancing our understanding of the local stratigraphy.

You can read a little more about this here and here.

More on the Paleoecology of Triassic Turtles

Benson, R. B. J., Domokos, G., Várkonyi, P. L., and R. R. Reisz. 2011. Shell geometry and habitat determination in extinct and extant turtles (Reptilia: Testudinata). Paleobiology 37:547-562. doi: 10.1666/10052.1
Abstract - A variety of means, including forelimb proportions and shell bone histology have been used to infer the paleoecology of extinct turtles. However, the height-to-width ratio of the shell (as a one-parameter shell model) has been dismissed because of its unreliability, and more complex aspects of shell geometry have generally been overlooked. Here we use a more reliable, three-parameter geometric model of the shell outline in anterior view as a means to assess turtle paleoecology. The accuracy of predictions of extant turtle ecology based on our three-parameter shell model is comparable to that derived from forelimb proportions when distinguishing between three ecological classes (terrestrial, semiaquatic, and aquatic). Higher accuracy is obtained when distinguishing between two classes (terrestrial and non-terrestrial), because the contours of aquatic and semiaquatic turtles are often very similar. Our model classifies Proterochersis robusta, a stem turtle from the Late Triassic of Germany, as non-terrestrial, and likely semiaquatic. Our method, combined with inferences based on limb proportions, indicates a diverse range of ecotypes represented by Late Triassic stem turtles. This implies that the ecological diversification of stem-group turtles may have been rapid, or that a substantial period of currently cryptic diversification preceded the first fossil appearance of the turtle stem lineage during the Late Triassic.

High Latitute Triassic Flora from Antarctica

Escapa, I. H., Taylor, E. L., Cúneo, R., Bomfleur, B., Bergene, J., Serbet, R., and  T. N. Taylor. 2011. Triassic floras of Antarctica: plant diversity and distribution in high paleolatitude communities. Palaios 26:522-544.
Abstract - Continental Triassic sequences in Antarctica are among the most continuous and best represented in Gondwana. Triassic fossil plants have been collected sporadically from Antarctica since the beginning of the twentieth century, but our knowledge of the vegetation during this time has dramatically increased during the last three decades. Here we review the fossil record of Triassic plants as representatives of natural groups from sites along the Transantarctic Mountains, using the fossils as evidence for successive vegetational changes through the Triassic, taking into account that these plant communities were living under particular high-latitude (70° or higher) paleoclimatological conditions, including a polar light regime. Even though our knowledge of the Triassic floras of Antarctica is still incomplete, this survey shows that these floras were remarkably diverse. Lycopsids, equisetaleans, ferns, seed ferns, ginkgoaleans, and conifers were major components of the landscape in Antarctica during this time. The diversity of gymnosperms is exceptional, with almost every major clade of seed plants present, despite the high paleolatitude; however, each clade is often represented by only one or a few genera. The occurrence of permineralized peat, along with compression-impression floras, has increased our knowledge of the morphology, reproductive biology, and evolution of many of the plants in these floras. In general, floral changes in Antarctica during the Triassic can be recognized elsewhere in Gondwana, especially in South America, although a strict correlation based on macrofossils is still not possible. Thus, this contribution represents the first attempt to bring together information on Triassic floras from continental Antarctica (excluding the Antarctic Peninsula) within a biostratigraphic framework and thereby to compare these floras with those from lower latitudes.

PEFO Summer Fieldwork Parts 3 and 4

Susan has the rest of her summer exploits in the Chinle Formation up at The Forgotten Archosaurs (Parts three and four). Reading through makes me wish I was there ;). Isn't she glad that she wrote everything down?

Complex Tetrapod Burrows from the Middle Triassic of Morocco

Too bad there are not any body fossils associated with this find....
Voigt, S., Schneider, J. W., Saber, H.,  Hminna, A.,  Lagnaoui, A.,  Klein, H.,  Brosig, A., and J. Fischer. 2011. Complex tetrapod burrows from Middle Triassic red beds of The Argana Basin (Western High Atlas, Morocco). Palaios 26:555-556.

Abstract - Although burrowing ability has been widespread in tetrapods for more than 300 million years, subsurface dwelling structures that indicate communal behavior are poorly evidenced from pre-Cenozoic strata. Here we present recently discovered tetrapod burrows from Middle Triassic red beds of the Argana Basin in central Morocco, whose complexity suggests an origin by gregarious animals. The well-preserved burrows occur in interbedded mudstones and sandstones interpreted as channel and overbank deposits of ephemeral, braided streams. All burrows originate from the top of thick-bedded sandstones and descend as moderately inclined (10°–30°), partially spiral tunnels to laterally extended, branched chambers in underlying mudstones. Tunnel segments are biconvex to planoconvex in cross section, up to 20 cm wide and 12 cm in maximum height and exhibit transverse scratch marks along the ceilings and sidewalls. Distinctive burrow characteristics include a laterally sinuous geometry (wavelength λ  =  38–45 cm; amplitude A  =  5–10 cm) of the tubelike passages and the presence of grouped alcoves in terminal chambers. We attribute the burrows to procolophonids or therapsids based on closely associated tetrapod tracks and the limited diameter of the excavations. Our findings represent the second oldest record of communal fossorial behavior by tetrapods and the oldest example from low-latitude areas. Beyond providing refuge from predators, these elaborate underground structures probably functioned as a buffer against diurnal or seasonal variations of air temperature and humidity in a semiarid habitat that was situated just north of the paleoequator.

Summer Fieldwork at PEFO pt. 2

Susan Drymala has another post up at The Forgotten Archosaurs. I like the photo of the seat belt restraining the fossil jacket.