Field of Science

You Don't Need to Purchase Articles for Outrageous Fees Anymore. You Can Now RENT Them Instead!

In putting together my last post I noticed something interesting (disturbing?) from the Cambridge Journals site.  If you would like to purchase a PDF of the Parringtonia gracilis redescription paper I just mentioned it will cost you $45.00 U.S. The atrociousness of this has been discussed in detail at several other blogs most notably by the SV-POW guys.  Anyhow, for those of you who don't want to (or can't afford to) shell out this kind of cash for a single article there is now another option available.  You can rent the article instead for the low(er) price of $5.99 U.S.!!!  You get 24 hour access to the article, which is probably enough to cram in a couple of readings if you don't really want to fully comprehend the paper. Also just think of the hard drive space you'll save if all of your PDFs 'disappeared' after a 24 hour period.  Currently I'm very hard pressed to think of a reason why this would be attractive. I suppose if you simply wanted to download the article and print it for future use.... Anyone else able to present this in a positive light?

Redescription of the Archosaur Parringtonia gracilis from the Middle Triassic Manda Beds of Tanzania

Here is another redescription of another of the enigmatic archosauriforms from the Middle Triassic Manda Formation. This study confirms the affinity of Parringtonia gracilis and Erpetosuchus granti, and reinforces the importance of redescribing these older taxa using an apomorphy-based approach and placing them in a modern phylogenetic analysis. Unfortunately the exact position of Erpetosuchidae with Archosauria was not able to be precisely determined.

Nesbitt, S. J., and R. J. Butler. 2012. Redescription of the archosaur Parringtonia gracilis from the Middle Triassic Manda beds of Tanzania, and the antiquity of Erpetosuchidae. Geological Magazine (FirstView article), 14p. doi:10.1017/S0016756812000362 

Abstract - Parringtonia gracilis Huene, 1939 is represented by both cranial and postcranial material collected from the lower Middle Triassic (Anisian) Lifua Member of the Manda beds in southwestern Tanzania. This aberrant taxon was previously proposed to have affinities with pseudosuchian archosaurs, and specifically with the enigmatic Erpetosuchus granti from the Upper Triassic of Scotland. Here, we confirm the close affinities of Parringtonia gracilis and Erpetosuchus granti based on the following unambiguous synapomorphies: mediolaterally expanded posterior portion of the maxilla, alveoli present only in the anterior half of the maxilla, and absence of tooth serrations. Furthermore, the two taxa share osteoderms with deep sculpturing, a deep fossa on the dorsal margin of the neural spines and a heavily waisted shaft of the scapula. We added both Parringtonia gracilis and Erpetosuchus granti into a comprehensive phylogenetic analysis of early archosaurs and found that these taxa are clearly referable to Archosauria but that relationships are poorly resolved at the base of this clade. However, our analysis demonstrates that Erpetosuchus granti is not closely related to Crocodylomorpha, as has been hypothesized previously. The Erpetosuchidae are a clade of small-bodied archosaurs that have a poor fossil record but have members from both northern and southern Pangaea, ranging temporally from the Middle to Late Triassic. Thus, Erpetosuchidae is part of the early archosaurian radiation.

Diandongos​uchus, A New Archosaur from Triassic of China

There are lots of incredible specimens coming out of the Middle Triassic in recent years (SVP attendees will see another in a talk this year by Sterling Nesbitt and colleagues), and this amazing fossil from the Ladinian of China does not disappoint. It consists of most of a partially articulated/associated skeleton found in marine sediments not far from where the early diverging poposauroid  Qianosuchus mixtus was  recovered some time ago.

The authors have provided color figures that allow the reader to see many of the details of the skeleton; however, the semi-articulated nature of the specimen seems to prelude dismantling of the specimen to see three dimensional views of the specimen. Furthermore, because it is in a marine shale, some crushing of the specimen has occurred. This is unfortunate because it does not allow clear study of the ilia or of the ends of the femora, which would provide key characters for the taxonomic placement of the specimen. Li et al. do code the specimen into Sterling Nesbitt's recent (2011) phylogenetic matrix of Archosauriformes and it is recovered, with much support, as the earliest diverging poposauroid. This is of interest of course because it suggests that the plesiomorphic conditions for poposauroids are quadrupedal, toothed, long-snouted forms that lack an expanded dorsal sail, possess osteoderms, and are possibly semi-aquatic. Compare this to other members of the clade such as Effigia okeeffae. The amount of morphological variation in this group is incredible.

I'll admit that I'm not entirely convinced of the phylogenetic placement of this specimen, but unfortunately I cannot get into the details of why at this time. Let's just say that this is an extremely interesting taxon that should be the subject of debate for a while to come. I do really wish the ilia were better preserved or more visible, but it is really hard to complain about such a beautiful fossil.

Li, C., Wu, X.-C., Zhao, L.-J., Sato, T. and L.-T. Wang. 2012. A new archosaur (Diapsida, Archosauriformes) from the marine Triassic of China. Journal of Vertebrate Paleontology 32(5): 1064-1081. DOI:10.1080/02724634.2012.694383

Abstract - A new Middle Triassic archosaur, Diandongosuchus fuyuanensis, gen. et
sp. nov., is described on the basis of a skeleton from the Zhuganpo Member (Ladinian) of the Falang Formation, eastern Yunnan Province, China. It is primarily characterized by the nasal process of the premaxilla extending posteriorly well beyond the external naris, the super-sized coracoid foramen laterally bordered by the scapula, the ischium with a strongly expanded medial portion anteroposteriorly longer than the proximodistal height of the bone, and anteriorly notched cervical osteoderms. D. fuyuanensis is a pseudosuchian on the basis of the crocodile-normal tarsal joint and other features, such as the distal end of the ulna in posterolateral view squared off, osteoderms with a distinct anterior process, the presacral vertebrae dorsally covered by more than one osteoderm, dorsal osteoderm alignment dorsal to presacrals 10–24 staggered, the pubis-ischium contact reduced to a thin proximal contact, and the medial contact of the ischia extensive but the dorsal margins separate. It is from a marine deposit but shows few morphological adaptations of the postcranial skeleton for a semiaquatic way of life when compared with Qianosuchus from the Anisian limestone of the same area. A phylogenetic analysis derived from an existing data matrix suggests that the new archosaur occupies the basal-most position in Poposauroidea and further confirms the poposauroid status of Qianosuchus. On the basis of current information, the discovery of Diandongosuchus does not firmly underscore the affinity of the semiterrestrial vertebrate faunas between the eastern and western regions along the northern coastline of the Tethys.

More Photos from the Petrified Forest

I'm currently creating a database of all of our photos from the last decade of paleontological work at Petrified Forest National Park and am working through 2002. These photos were taken by Daniel Woody who was investigating the Sonsela Member of the Chinle Formmation and assisting with the paleontology work. I'm amazed how far the quality of digital photos have over the decade!

Phytosaur lower jaw in the Crystal Forest

Phytosaur quadrate bone in the Blue Mesa Member

Triassic Fieldwork in Utah

Randall Irmis of the Utah Museum of Natural History is posting about current fieldwork in the Triassic of Utah.  You can check out the first post here and check back for more to follow.

Reevaluating the 'Prosauropods' of the Upper Triassic Caturrita Formation of Brazil

Bittencourt, J. S., Stock da Rosa, A. A., and M. C. Langer. in press. Dinosaur remains from the ‘Botucaraí Hill’ (Caturrita Formation), Late Triassic of south Brazil, and their stratigraphic context. Historical Biology. DOI:10.1080/08912963.2012.694881

Abstract - Vertebrate fossils recovered from sites nearby the Botucaraí Hill and Candelária (Caturrita Formation) depict a diverse Late Triassic tetrapod fauna from south Brazil. These records are of key importance to the biostratigraphy of the upper sections of the Rosario do Sul Group. A lithological and biostratigraphic survey on the main fossil localities of the Botucaraí Hill area confirms the occurrence of the lower Hyperodapedon and the upper Riograndia Assemblage Zones in the region, the latter yielding early saurischians. In this paper, three incomplete dinosaur specimens, an isolated sacral vertebra, an articulated left pubis–ischium and an isolated right ischium, from the ‘Botucaraí Hill’ site are described. A comparative survey suggests that these specimens have sauropodomorph affinities, but probably more primitive than typical ‘prosauropods’ from the Norian-Early Jurassic. Regardless of the phylogenetic position of Guaibasaurus as theropod or sauropodomorph, their occurrence in the Caturrita Formation, which also yielded ‘core prosauropods’ from the Santa Maria region, suggests either the survival of early members of the clade with more derived ‘prosauropods’ or that heterochronous faunas are sampled from that stratigraphic unit.

Examining the Effects of Dataset Quality on Paleodiversity Studies

I would love to do a similar study for the Chinle Formation...

Irmis, R. B., Whiteside, J. H., and C. F. Kammerer. In press.  Non-biotic controls of observed diversity in the paleontologic record: An example from the Permo-Triassic Karoo Basin of South Africa.  Palaeogeography, Palaeoclimatology, Palaeoecology.  doi: 10.1016/j.palaeo.2012.07.014.
 Abstract - Paleodiversity trends through geologic time can be affected by a number of geologic, taphonomic, and anthropogenic biases that obscure or prejudice paleoecological patterns in the fossil record. Although much work has concentrated on the relationship between geologic exposure, sample size, and taxonomic richness (i.e., number of taxa), few studies have investigated the potential effects of dataset quality and changing taxonomy. We use four different specimen-level datasets of Permo-Triassic tetrapods from the Karoo Basin of South Africa to investigate how sample size, geologic outcrop, dataset quality, and taxonomic revision all affect observed estimates of generic richness, evenness, and relative abundance. Our results indicate that large-scale patterns of richness, evenness, and abundance, such as the effects of the end-Permian mass extinction, are generally robust to these potential biases across the four different datasets. In contrast, absolute values vary significantly as do finer-scale patterns. In agreement with past studies, taxonomic errors, revised taxonomy, and new taxa have little effect on patterns of richness and evenness; instead, the addition of large numbers of new specimens to the dataset has the largest effect on these paleodiversity metrics, despite application of samplestandardization. We conclude that although large specimen datasets (hundreds to thousands of specimens) are robust to various potential biases, and can recover large-scale paleobiologic trends, they are still affected by many non-biotic controls, and workers should strive to improve dataset quality and understand the underlying reasons for observed paleodiversity patterns.

New Ladinian Biostratigraphic Correlation Between South America and South Africa

Nice biostratigraphic correlation between the Santa Maria Formation of Brazil and the Karoo of South Africa. Partially fills the 'Ladinian Gap' in the Karoo.

Abdala, F., Marsicano, C. A., Smith, R. M. H., and R. Swart. 2012. Strengthening western Gondwanan correlations: a Brazilian dicynodont (Synapsida, Anomodontia) in the Middle Triassic of Namibia. Gondwana Research (advance online publication)

Abstract - Terrestrial Middle Triassic strata occur throughout continental Africa, and are particularly well exposed in South Africa, Tanzania, Zambia, and Namibia. The youngest age for all these African deposits is widely accepted as early Middle Triassic (Anisian). Fossils collected recently from the uppermost strata of the upper Omingonde Formation in Namibia highlighted the presence of Chiniquodon, a carnivorous cynodont previously only found in Ladinian-Carnian aged rocks of South America. In addition, work in progress indicates that a large archosaur, originally reported as Erythrosuchus, also discovered from levels close to the top of this unit, is in fact a rauisuchian, a group of archosaurs well known from Ladinian-Carnian beds of southern South America. Here we present the first record of the tuskless dicynodont Stahleckeria potens, from the top of the upper Omingonde Formation in central Namibia. This taxon was up until now only known from the Ladinian Dinodontosaurus Assemblage Zone of the Santa Maria Formation in southern Brazil. Thus, compelling evidence for a Ladinian age for the upper levels of the upper Omingonde Formation is provided by two therapsid and one archosaur taxa. The tetrapod fauna of the upper Omingonde Formation partially fills the gap of the well-documented hiatus (Ladinian gap), prevalent throughout the Karoo basins of south and central Africa. The presence of the same therapsid taxa in the Namibian Waterberg Basin and the Paraná Basin of Brazil during Middle Triassic suggests that these basins were biogeographically linked through a series of interconnecting lowlands, with no major ecological, climatic and/or physical barriers.

New ICS International Chronostratigraphy Chart Uses the Long Norian

The base of the Norian stage is set at ~228 Ma on the new chronstratigraphy chart of the International Commission on Stratigraphy.  Still needs further support and eventially a golden spike, but this is the first time the ICS has used the long Norian hypothesis on its published chart.

You can download the latest timescale from here: