Field of Science

New Early Middle Jurassic Tetanuran Theropod from China

Well this appears to be Jurassic week on Chinleana. Again not a Triassic specimen, but early Middle Jurassic dinosaurs tend to be rare and this one appears to be a fairly plesiomorphic tetanuran. The authors claim that it is more plesiomorphic than Sinraptor, Yangchuanosaurus, and "Szechuanosaurus", although they were not able to support this with a phylogenetic analysis at this time.

Wu, X., Currie, P.J., Dong, X., Pan, S., and T. Wang. 2009. A new theropod dinosaur from the Middle Jurassic of Lufeng, Yunnan, China. Acta Geologica Sinica 83:9-24.

Abstract – A new theropod dinosaur, Shidaisaurus jinae gen. et sp. nov., has been described on the basis of an incomplete skeleton. The specimen was found near the base of the Upper Lufeng Formation (early Middle Jurassic) in Yunnan, China. It is the first theropod dinosaur from the Middle Jurassic of Yunnan. Shidaisaurus jinae is distinguishable from other Jurassic theropods by certain features from the braincase, axis, and pelvic girdle. The absence of any pleurocoels in the axis or in any anterior dorsal vertebrae suggests that the new Lufeng theropod is relatively primitive and more plesiomorphic than most of the Middle to Late Jurassic theropods from China. Most Chinese taxa of Jurassic theropod dinosaurs have not been well described; a further detailed study will be necessary for us to determine their phylogenetic relationships with Shidaisaurus jinae.

Early On-line Publications and Establishing Taxonomic Names

I may have not been paying attention lately but when I was downloading the new paper yesterday on the new stegosaur Miragaia from the Royal Society website I noticed something at the bottom of the download cover sheet that surprised me as I do not recall seeing anything like this previously.

Advance online articles have been peer reviewed and accepted for publication but have not yet appeared in the paper journal (edited, typeset versions may be posted when available prior to final publication). Advance online articles are citable and establish publication priority; they are indexed by PubMed from initial publication. Citations to Advance online articles must include the digital object identifier (DOIs) and date of initial publication.


So the editors of the Proceedings of the Royal Society B are claiming that new taxon names such as Miragaia longicollum are established upon publication online, so in this specific case M. longicollum was established on February 25, 2009 and until the article comes out in print it is cited with this date (I have fixed this in my previous post and am glad that they explicitly state how to cite an advance article).

What does the International Code of Zoological Nomenclature (ICZN) say about this? Jerry Harris had an article a few years back (Harris, 2004) where he recommended amendments to Articles 8 and 9 of the code to accommodate DOIs and advance online publications. Specifically this would deal with Articles 8.6, which states that on-line publications must deposit hard copies “in at least 5 major publicly accessible libraries which are identified by name in the work itself” and Article 9.8 which states that “text or illustrations distributed by means of electronic signals” do not constitute valid work (ICZN, 1999). Thus, according to the ICZN, the name would not be valid until the printed version is made available to the public (unless an amendment has already been made, which I am unaware of). Countering this Harris (2004) argued that on-line publications met the availability criteria and that DOIs provide unique, archived identifiers that fix the date of publication, and thus proposed:

“I propose to the Commission that, under Article 78.3 ('Amendments to the Code'), Articles 8 and 9 of the current Code require both pro- and retroactive (to the effective date of the Fourth Edition, I January 2000) modification to accommodate the following issue: documents published electronically with DOl numbers and that are followed by hard-copy printing and distribution be exempt from Article 9.8 and be recognized as valid, citable sources of zoological taxonomic information and that their electronic publication dates be considered definitive. Note that this does not require electronic publications to have DOl numbers; only that any paper appearing in electronic format that does have a DOl number, and is followed by traditional, hard-copy issuance, is an acceptable place for the appearance of zoological nomenclatural action. Electronic publications lacking DOl numbers lack the citability benefits enjoyed by DOl registered documents and, regardless of whether followed by hard-copy release, will still be subject to Article 9.8 and be considered invalid for zoological nomenclatural actions. Such a change may be issued as a Declaration (Article 78.3.3 and subject to the provisions of Article 80.1), since it entails only minor changes to Articles 8.1.3 and 9.8, as follows (recommended additions in italics): Article 8.1.3. It must have been produced in an edition containing simultaneously obtainable copies by a method that assures numerous identical and durable copies, including documents that contain identical Digital Object Identifier numbers and for which electronic documents are followed by hard-copy release. Article 9.8. Text or illustrations distributed by means of electronic signals (e.g. by means of the World Wide Web), except where such material meets the provisions of Article 8.1.3”.


Given all of this, I want to know does the statement by The Royal Society fix the publication date for the name Miragaia longicollum as February 25, 2009?

As a side note check out Adam Yates comments at Dracovenator on the taxonomic name of this specimen.

Harris, J.D. 2004. 'Published Works' in the electronic age: recommended amendments to
Articles 8 and 9 of the Code. Bulletin of Zoological Nomenclature 61:138-148.

International Committee of Zoological Nomenclature. 1999. International Code of Zoological Nomenclature 4th Edition. The International Trust for Zoological Nomenclature, London, 126 pp.

New Long Necked Stegosaur Miragaia longicollum

Not Triassic but still really cool. This is a new advance paper in Proceedings of the Royal Society B on a new long necked stegosaur from the Late Jurassic of Portugal. Appropriately named Miragaia longicollum it has at least 17 cerival vertebrate due to "cervicalization" of the dorsal column. Very cool. Even cooler is that it is available for free from the Royal Society website. The photo below is from here.

REFERENCE

Mateus, O., Maidment, S.C.R., and N.A. Christiansen. 2009. A new long-necked ‘sauropod-mimic’ stegosaur and the evolution of the plated dinosaurs. Proceedings of the Royal Society B, Published online on February 25, 2009. DOI 10.1098/rspb.2008.1909.

Phytosaur Skull Preparation

Back in November of 2008 I mentioned a new phytosaur skull collected from Petrified Forest National Park during the summer. Encased in a sandstone horizon of the Jim Camp Wash beds of the Sonsela Member (Chinle Formation), the skull is from the type locality of Pseudopalatus jablonskiae and was recovered about 100 meters from the spot where the type skull was collected. As I stated this skull is important because it may represent a second specimen of P. jablonskiae, but more complete than the type skull. Alternatively it could represent another phytosaur taxon which was a contemporary of P. jablonskiae. Because the skull is from the upper Jim Camp Wash beds, above the Jasper Forest bed it should be a pseudopalatine.

















The picture on the left shows the initial discovery. The skull is dorsal side up and beneath the rock hammer. Squamosals showing on the left [below the hammer handle] and the external nares showing on the right just below the hammer head. The picture on the right shows the beginning of the excavation. The sandstone was very well indurated and we needed a rock saw and hammers and chisels to block out the skull for removal. The resulting jacket weighed a few hundred pounds.

Late last week we cracked open the jacket and PEFO preparator Matt Brown started removing the rock. As of Tuesday morning this is what was exposed:



As you can see the upper left corner of the skull is now partially exposed. The squamosals are broad in dorsal view, thus the skull does belong to a pseudopalatine. The squamosals are more posteriorly extended than in the type of P. jablonskiae; however, this appears to be a larger specimen. Unfortunately the posterodorsal surfaces of the squamosals were what was exposed at discovery and thus were somewhat eroded. Also, the rock is much harder than we expected and the separation from the bone is not always clean. Some of the bone within the rock is actually fractured as it is softer than the surrounding matrix. Still, during excavation we located the tip of the premaxilla and both quadratojugals, so we are fairly certain that we have a complete and undistorted skull. Only time will tell. Over the next month or two I'm hoping to document the entire preparation process here and we will discover exactly what this skull is and how well it is preserved. Stay tuned.

Latest Literature

Some new papers, one on the phylogeny of the Parareptilia and two on the Permian branchisaurid Apateon. I know that the last two are not Triassic but they are close enough! Plus, more papers on temnospondyls.

Tsuji L. A. and J. Muller. 2009. Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade. Fossil Record 12:71-81. DOI 10.1002/mmng.200800011

ABSTRACT - In the present study, the historical development of Parareptilia as a phylogenetically valid clade is summarized, and for the first time a modern phylogenetic definition of both Parareptilia as well as Eureptilia is presented, which will facilitate the study of problems of early amniote classification. Furthermore, a preliminary study of the rates of diversification in parareptiles is performed on the basis of topological information on species diversity. While acknowledging that the bias of the fossil record also needs to be considered for a more definitive statement on parareptile diversification, our results show that a significant increase in diversification rate could be recorded only among Triassic procolophonoids, making it difficult to interpret evolutionary novelties such as herbivory or impedance-matching hearing as being key innovations that might have driven diversification.

Witzmann, F. 2009. Cannibalism in a small growth stage of the Early Permian branchiosaurid Apateon gracilis (Credner, 1881) from Saxony. Fossil Record 12:7-11. DOI 10.1002/mmng.200800006

ABSTRACT - An almost complete specimen of the branchiosaurid temnospondyl Apateon gracilis (Credner, 1881) with a skull length of approximately 7 mm from the Early Permian Dohlen Basin in Saxony is described that possesses a nearly complete conspecific specimen of approximately 4 mm skull length in its digestive tract. This is the first evidence of cannibalistic behaviour in small growth stages of branchiosaurids, whose dentition and hyobranchial morphology suggest adaptations to the capture of small invertebrates and feeding on small phyto- and zooplankton by filtering from the water. Therefore, cannibalism in small branchiosaurids certainly represents an exceptional case, possibly triggered by unfavourable environmental conditions.

Frobisch, N.B., and R.R. Schoch. 2009. The largest specimen of Apateon and the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae. Fossil Record 12:83-90. DOI 10.1002/mmng.200800012

ABSTRACT - Two distinct developmental trajectories, metamorphosis and neoteny (the retention of larval somatic features in adult animals), have been reported for the small gill-bearing branchiosaurids of the Late Carboniferous and Early Permian of central Europe. Based on a very large specimen of the species Apateon caducus (Ammon, 1889), anatomical features characteristic for the neotenic phenotype of branchiosaurids are described. Large neotenes lack changes that occur during a short phase of transformation into terrestrial adults (metamorphosis), such as ossification of the braincase and palatoquadrate and intercentra, further ossification of the girdles and formation of muscle attachment scars and processes on the limb bones. They also lack a distinct sculpturing of the dermal skull roofing elements with deep polygonal ridges and grooves. Instead, larval somatic features are retained including ossified branchial denticles indicative of open gill slits and accentuated larval-type sculpturing of the dermal skull roof. Large size, high degree of ossification as compared to the larvae, and the presence of uncinate processes on the ribs clearly demonstrate an adult ontogenetic stage. Neotenes remained in the aquatic environment throughout their life and were most likely not capable of effective terrestrial locomotion. The frequency distribution of the two phenotypes in modern salamander populations and the environmental cues that influence the development of them provide a comparative framework for the discussion of the evolution of the two life history pathways in branchiosaurids.

Blogroll Updates and Thanks

Several regular readers have confessed to me that they often access my blog to check out my blogroll, which makes it easy to scroll down and view the topics of recent posts from a variety of blogs. I try to add new links regularly, especially to pages that I find myself travelling to often although I sometimes do not post on these additions. Anyhow, I have recently added a few new blog links as well as links to other pages of interest including Triassic researcher pages (Randy, please let me know when you move your CV page to your new institution) and National Park related sites (hey...I work in a national park). Anyhow, my readership has increased quite a bit since last August when I started the site and I'd like to thank everyone who drops by, especially my regulars. Please feel free to drop me a line or comment if there are other aspects of Triassic paleo and geology you would like to see covered in the future or if there are any links that I should add. Thanks again.

WAVP - 2009

Petrified Forest National Park had the honor of hosting (along with Northland Pioneer College) the annual meeting of the Western Association of Vertebrate Paleontologists (WAVP) last weekend. For those of you who do not know about WAVP, it is essentially an unchartered group of paleontologists mainly from the western U.S. who meet yearly in February. The format is informal and it is a great forum for students to get experience presenting their research (indeed this is why the annual meeting was established). I gave my first talk at a WAVP meeting years ago.

This year we had over 60 attendees from a variety of institutions and 21 presentations (19 talks, 2 posters) ranging from Devonian to Pleistocene. We also had two field trips, one to some fossil localities at Petrified Forest National Park (which required some slogging through the mud due to a winter storm earlier in the week) and a later trip to the Cretaceous Moreno Hills Formation in the Zuni Basin of New Mexico (holotype locality of the dinosaurs Nothronychus and Zuniceratops).

Because it was held in the park we had a larger than usual Triassic contingent. Bill Mueller and Gretchen Gurtler (Texas Tech University) presented posters on the fauna of the Upper Triassic Dockum Group, focusing on basal phytosaurs. Max Langer (Universidade de São Paulo, Brazil), who was in the park doing research on early dinosaurs, gave a presentation on the Triassic faunal sequences in Brazil. Axel Hungerbuehler (Mesalands Community College) and students provided an update of new finds from the Redonda Formation of the Dockum Group. Jeff Martz and I presented the preliminary results of our recent stratigraphic and biostratigraphic revisions of the Chinle Formation at the Petrified Forest. Jeff has discussed this work in some detail at his blog Paleo Errata, and I am providing our WAVP meeting abstract below.

The WAVP meeting was a great time to catch up with a lot of friends and colleagues and check out some new research on a variety of vertebrate groups and time periods. At SVP meetings concurrent sessions and just the general busy atmosphere usually precludes me from seeing presentations outside of Mesozoic archosaurs, so these smaller meetings are very interesting. The location of next year's meeting is not established but hey that is WAVP. You can also read more about this years meeting here.

Revisions to the Lithostratigraphy and Vertebrate Biostratigraphy of the Chinle Formation (Upper Triassic) of Petrified Forest National Park

Jeffrey W. Martz and William G. Parker, Petrified Forest National Park, Petrified Forest, AZ, USA.

THE GEOLOGY and paleontology of the Upper Triassic Chinle Formation in Petrified Forest National Park and the surrounding region of northern Arizona has been extensively studied for over a century. Over this period, the broad lithostratigraphic framework of the park was generally agreed upon by most workers, and extensive vertebrate remains were collected and described. These studies led to the landmark 1985 study by Rob Long and Karen Ballew, which made critical contributions to phytosaur and aetosaur taxonomy, and recognized an important faunal turnover occurring at about the level of the Sonsela sandstone bed, between what were later called the “Adamanian and Revueltian land vertebrate faunachrons.” Further advances have been made in recent years to improve the stratigraphic resolution of this faunal transition, and to clarify the systematics of Upper Triassic vertebrate taxa.

Lithostratigraphic revisions made in recent years by some workers have identified a package in the middle of the Chinle Formation dominated by sandstone with lesser interbedded conglomerate and mudstone, which has been named the Sonsela Member. This recent work has also presented a novel correlation between two of the most prominent sandstone units within this member: the traditional Sonsela sandstone bed (here called the Jasper Forest Bed) and Flattops sandstone number one. The correlation of these two units has had important ramifications for vertebrate biostratigraphy and biochronology by resulting in an apparent overlap in the ranges of the taxa defining and characterizing the Adamanian and Revueltian.

Over the past year, the careful walking out of contacts between various lithologic bodies has falsified the recent revisions, and re-established the stratigraphic separation between the Sonsela sandstone bed and Flattops sandstone number one, as well as supporting the stratigraphic equivalence of the Jasper Forest Bed and Rainbow Forest Bed. This eliminates the apparent overlap between the faunas of the Adamanian and Revueltian. Moreover, our work establishing the precise stratigraphic position of both old and new fossil localities within this lithostratigraphic framework has allowed plotting the biostratigraphic ranges of taxa with a greater degree of precision than previously known, and allows precise stratigraphic placement of the Adamanian-Revueltian boundary. The available biostratigraphic information indicates that this faunal transition occurs just above the Jasper Forest Bed, during important shifts in the depositional pattern of the Chinle Formation.

New Basal Sauropodomorph from South America

Martinez, R.N., and O.A. Alcober. 2009. A Basal Sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the Early Evolution of Sauropodomorpha. PLoS ONE 4: e4397. doi:10.1371/journal.pone.0004397

Abstract

Background: The earliest dinosaurs are from the early Late Triassic (Carnian) of South America. By the Carnian the main clades Saurischia and Ornithischia were already established, and the presence of the most primitive known sauropodomorph Saturnalia suggests also that Saurischia had already diverged into Theropoda and Sauropodomorpha. Knowledge of Carnian sauropodomorphs has been restricted to this single species.

Methodology/Principal Findings: We describe a new small sauropodomorph dinosaur from the Ischigualsto Formation (Carnian) in northwest Argentina, Panphagia protos gen. et sp. nov., on the basis of a partial skeleton. The genus and species are characterized by an anteroposteriorly elongated fossa on the base of the anteroventral process of the nasal; wide lateral flange on the quadrate with a large foramen; deep groove on the lateral surface of the lower jaw surrounded by prominent dorsal and ventral ridges; bifurcated posteroventral process of the dentary; long retroarticular process transversally wider than the articular area for the quadrate; oval scars on the lateral surface of the posterior border of the centra of cervical vertebrae; distinct prominences on the neural arc of the anterior cervical vertebra; distal end of the scapular blade nearly three times wider than the neck; scapular blade with an expanded posterodistal corner; and medial lamina of brevis fossa twice as wide as the iliac spine.

Conclusions/Significance: We regard Panphagia as the most basal sauropodomorph, which shares the following apomorphies with Saturnaliaand more derived sauropodomorphs: basally constricted crowns; lanceolate crowns; teeth of the anterior quarter of the dentary higher than the others; and short posterolateral flange of distal tibia. The presence of Panphagia at the base of the early Carnian Ischigualasto Formation suggests an earlier origin of Sauropodomorpha during the Middle Triassic.

Triassic Critter Tributes on You Tube

I have just found out about these. On You Tube there are a variety of "tributes" to a number of Mesozoic archosaurs, including many from the Triassic. These are basically slide shows of photos of various reconstructions set to music (hard rock/heavy metal).

Here is a small sample of what is available, tributes for Euparkeria, Saurosuchus, and Postosuchus. Out of these three my fave is probably the Saurosuchus tribute (I've always had a soft spot for "emo-core"). I admit, however, that I do not entirely understand these song selections. I mean, "Arms Wide Open" for Postosuchus?! What gives?





The Aetosaur Paper That Changed Everything

Recent events have gained the aetosaurs, those Late Triassic armored pseudosuchians, as bit of notoriety lately (see here, here, here, and here), but all of this aside the truth is that these critters are important index fossils for non-marine Upper Triassic strata worldwide.

Unbenownst to many is the impressive pedigree of paleontologists who have worked on aetosaurs. Louis Agassiz named the first aetosaur taxon (Stagonolepis robertsoni) in 1844 (admittedly he thought he was describing large ganoid fish scales from the Devonian, hence the name); Thomas Huxley (yeah, that Thomas Huxley) wrote two monographs on crocodian nature of Stagonolepis, and indeed it was this work that finally convinced poor old Roderick Murchison and his colleagues that portions of the Old Red Sandstone where actually "new" and Triassic in age. The famous German paleontologist H. von Meyer described aetosaur material from Germany in 1861, although until fairly recently these osteoderms were thought to belong to the phytosaur Phytosaurus. Aetosaurus was also described from Germany by O. Fraas in 1887.

E.D. Cope described the first North American aetosaur material, Typothorax and Episcoposaurus in the late 1800s, and not to be outdone, his bitter rival O.C. Marsh also described an aetosaur (Stegomus), but the first two taxa were thought to be phytosaurs at the time. Other European and North American paleontologists to collect and or publish on aetosaurs include Freidrich von Huene, E.C. Case, Barnum Brown, Charles Camp, Ned Colbert, Glen Jepsen, John Wilson, Joe Gregory, and Don Baird. But again to many of the early workers the majority of these remains were considered to be phytosaurs. Aetosaurus was considered an "aetosaur" obviously, but in reality few workers really understood what an aetosaur was. Work in the 1940s through 1960s by Howard Sawin, Joe Gregory, Glen Jepsen, and Don Baird started differentiating aetosaurs from phytosaurs. In 1962, Gregory even suggested that the Phytosaurus material from Germany actually belonged to aetosaurs, however, he retracted this in 1969. By this time aetosaurs has also been found in South America (e.g., Casimiquela, 1961) and Alick Walker had published his influential monograph on Stagonolepis in 1961.

By the earlier 1980s aetosaurs were relegated to a role of being relatively uninteresting "armored thecodonts" and in western North America only two taxa were recognized, Typothorax and Desmatosuchus, but this was all about to change.

In the 1920s Charles Camp of the University of California Museum of Paleontology (UCMP) at Berkeley had conducted extensive research in the Chinle Formation of Arizona, including in the area of Petrified Forest National Park (it was a monument at the time and much smaller in size). Camp collected numerous specimens, took copious field notes and also photographed some of his sites. Although he only published on the phytosaurs (Camp, 1930) and the dicynodonts (Camp and Welles, 1957) he had collected the remains of many different groups including aetosaurs.

In 1981 Robert Long and Kevin Padian of the UCMP reinstituted Camp's field program at the Petrified Forest. Literally following in Camp's footsteps through the detailed notes and photos they relocated the majority of Camp's old collecting sites and discovered many more new ones. Through 1985, numerous specimens were collected including lots of aetosaur material. Camp (1930) had suggested that the phytosaurs of the Chinle Formation were of biostratigraphic significance and Long and his colleagues discovered that the same thing was true for the aetosaurs.

The results of this work culminated in a large monograph on Upper Triassic non-marine tetrapods of the American Southwest (Long and Murry, 1995); however, in 1985 a shorter article was published that would have far reaching affects for the studies of phytosaurs and aetosaurs. The paper titled "Aetosaur dermal armor from the Late Triassic of southwestern North America, with special reference to material from the Chinle Formation of Petrified Forest National Park" by Robert Long and Karen Ballew was published in a symposium volume (Museum of Northern Arizona Bulletin 54). The paper described and figured new and existing aetosaur material from the Chinle Formation and erected several new taxa. Groundbreaking were the following hypotheses:


1) The dorsal ornamentation pattern on aetosaur osteoderms was diagnostic to taxa and even small pieces of osteoderms could be accurately identified.

2) Instead of only two aetosaur taxa in the American Southwest, there were five, each dignosable by a unique combination of osteoderm characters. Recognozed taxa were Typothorax coccinarum, Desmatosuchus haplocerus, Calyptosuchus wellesi (new taxon), Paratypothorax sp., and "Typothorax" meadei.

3) Based on osteoderm characters "Typothorax" meadei was not referable to Typothorax but instead represented a new genus. This was also later stated by Murry and Long (1989) and Small (1989); however, the new genus was named by Hunt and Lucas in 1990 (who coincidently had edited the 1989 volume containing the first two papers).

4) The purported wide osteoderms of the phytosaur Phytosaurus actually belonged to an aetosaur, which Long and Ballew named Paratypothorax andressi.

5) Following Camp (1930) and Gregory (1957) the aetosaurs and phytosaurs of the American southwest had biochronological significance, demonstrating two distinct assemblages in the Chinle Formation (the type faunas of the Adamanian and Revueltian land vertebrate faunachrons of Lucas and Hunt, 1993).

These five hypotheses revolutionized aetosaur (and phytosaur) research by demonstrating a wide diversity of forms through distinguishable character diagnoses, whereas prior to this spiked forms were assigned to Desmatosuchus and forms with a radial plate ornamentation were assigned to Typothorax despite the fact that the type species of Typothorax, T. coccinarum, does not possess this type of armor ornamantation.

Although recent work (e.g., Martz and Small, 2006, Parker, 2003, 2007, 2008a, b; Parker et al. 2008) has demonstrated that paramedian osteoderm ornamentation is shared within more inclusive clades rather than species and that the shoehorning of taxa into Long and Ballew's five recognized taxa was masking aetosaur diversity, this 1985 paper forms the foundation of all current work on aetosaurs.



Artwork from top to bottom: paramedian plates of Desmatosuchus spurensis, Calyptosuchus (Stagonolepis) wellesi, and Typothorax coccinarum based on material from the southwest USA. All are from Long and Ballew (1985).

REFERENCES

Agassiz, L., 1844. Monographie des poisons fossils du Vieux Grés Rouge ou Systéme Dévonien (Old Red Sandstone) des Iles Britanniques ed de Russie. Jent et Gassman, Neuchâtel, 171 pp.

Camp, C. L., 1930. A study of the phytosaurs with description of new material from western North America. Memoirs of the University of California 10:1-174.

Casamiquela, R. M., 1961. Dos nuevos estagonolepoideos Argentinos (de Ischigualasto, San Juan). Revista Asocíacion Geológia de Argentina 16:143-203.

Case, E. C., 1920. Preliminary description of a new suborder of phytosaurian reptiles with a description of a new species of Phytosaurus. Journal of Geology 28:524- 535.

Cope, E. D., 1877. Report upon the extinct Vertebrata obtained in New Mexico by parties of the expedition of 1874: U.S. Geographical Surveys west of the 100th Meridian [Wheeler], part 2, p. 1-370.

Cope, E. D., 1892. A contribution to the vertebrate paleontology of Texas. Proceedings of the American Philosophical Society 30:123-131.

Fraas, O., 1877. Aëtosaurus ferratus Fr. Die gepanzerte Vogel-Eshe aus dem Stubensandstein bei Stuttgart. Württembergische naturwissenschaftliche Jahreshefte 33(3):1-22.

Gregory, J. T., 1953b. Typothorax and Desmatosuchus. Postilla 16:1-27.

Gregory, J. T., 1962b. The genera of phytosaurs. American Journal of Science 260:652-690.

Gregory, J. T., and F. Westphal, 1969. Remarks on the phytosaur genera of the European Trias. Journal of Paleontology 43(5):1296-1298.

Gregory, J.T. 1957. Significance of fossil vertebrates for correlation of Late Triassic continental deposits of North America. 20th Internat. Geol. Cong. Seccion I - El Mesozoico del hemisferio occidental y sus correlaciones mundiales, 1956, pp. 7-25.

Huene, F. von, 1915. On reptiles of the New Mexico Trias in the Cope Collection. American Museum of Natural History Bulletin 24(15):485-507.

Huene, F. von, 1920a. Osteologie von Aëtosaurus ferratus O. Fraas. Acta Zoologica 1:465-491.

Hunt, A. P., and S. G. Lucas, 1990. Re-evaluation of “Typothoraxmeadei, a Late Triassic aetosaur from the United States. Paläontologishe Zeitschrift 64:317-328.

Jepsen, G. L. 1948. A Triassic armored reptile from New Jersey. State of New Jersey Department of Conservation Miscellaneous Geologic Paper, pp. 1-20.

Long, R. A., and K. L. Ballew. 1985. Aetosaur dermal armor from the late Triassic of southwestern North America, with special reference to material from the Chinle Formation of Petrified Forest National Park. Museum of Northern Arizona Bulletin 47:45-68.

Long, R. A, and K. Padian, 1986. Vertebrate biostratigraphy of the Late Triassic Chinle
Formation, Petrified Forest National Park, Arizona: preliminary results; pp. 161- 169 in Padian, K. (ed.), The Beginning of the age of Dinosaurs: faunal change across the Triassic-Jurassic boundary. Cambridge University Press, Cambridge.

Long, R. A., and P. A. Murry. 1995. Late Triassic (Carnian and Norian) tetrapods from the southwestern United States. New Mexico Museum of Natural History and Science Bulletin 4:1-254.

Lucas, S. G., and A. P. Hunt, 1993a. Tetrapod biochronology of the Chinle Group (Upper Triassic), Western United States.

Meyer, H. von, 1861. Reptilien aus dem Stubensandstein des oberen Keupers. Palaeotographica 7:253-346.

Murry, P. A., and R. A. Long, 1989. Geology and paleontology of the Chinle Formation, Petrified Forest National Park and vicinity, Arizona and a discussion of vertebrate fossils of the southwestern upper Triassic, pp. 29-64 in S. G. Lucas and A. P. Hunt (eds.), Dawn of the age of dinosaurs in the American southwest. New Mexico Museum of Natural History. Albuquerque.

Parker, W. G. 2003. Description of a new specimen of Desmatosuchus haplocerus from the Late Triassic of Northern Arizona. Unpublished M. S. thesis, Northern Arizona University, Flagstaff, 315 p.

Parker, W. G. 2007. Reassessment of the aetosaur “Desmatosuchuschamaensis with a reanalysis of the phylogeny of the Aetosauria (Archosauria: Pseudosuchia). Journal of Systematic Palaeontology 5:41–68.

Parker, W. G. 2008a. Description of new material of the aetosaur Desmatosuchus spurensis (Archosauria: Suchia) from the Chinle Formation of Arizona and a revision of the genus Desmatosuchus. PaleoBios 281–40.

Parker, W.G. 2008b. How many valid aetosaur species are there? Reviewing the alpha-taxonomy of the Aetosauria (Archosauria: Pseudosuchia) and its implications for Late Triassic global biostratigraphy. Journal of Vertebrate Paleontology 28:125A.

Parker, W.G., Stocker, M.R., and R.B. Irmis. 2008. A new Desmatosuchine aetosaur (Archosauria: Suchia) from the Upper Triassic Tecovas Formation (Dockum Group) of Texas. Journal of Vertebrate Paleontology 28:692-701.

Sawin, H. J., 1947. The Pseudosuchian reptile Typothorax meadei. Journal of Paleontology 21:201-238.

Small, B. J., 1989b. Aetosaurs from the Upper Triassic Dockum Formation, Post Quarry,
West Texas; pp. 301-308 in S.G. Lucas and A.P. Hunt (eds.), Dawn of the age of dinosaurs in the American Southwest. University of New Mexico Press, Albuquerque.

Walker, A. D., 1961. Triassic reptiles from the Elgin area: Stagonolepis, Dasygnathus and their allies. Philosophical Transactions of the Royal Society, London, Series B, 248:103-204.

Wilson, J. A., 1950. Cope’s types of fossil reptiles in the collection of the Bureau of Economic Geology, the University of Texas. Journal of Paleontology 24:113-115.

Everything You Ever Wanted to Know About Theropod Furculae

Here is an important new paper by my friends and colleagues Sterling Nesbitt and Alan Turner. Where was this paper months back when we had a detailed discussion/disagreement on dinosaur furcula homology in my Age of the Dinosaurs class?

Nesbitt, S.J., Turner, A.H., Spaulding, M., Conrad, J.L., and M. A. Norell. 2009. The theropod furcula. Journal of Morphology early view. DOI: 10.1002/jmor.10724

ABSTRACT - The furcula is a structure formed by the midline fusion of the clavicles. This is the element which is unique to theropods and is important for understanding the link between birds and other theropods. New specimens from basal theropods suggest that the furcula appeared very early in theropod history. We review furcula development, function, and morphology, as well as the anatomical terminology applied to it. Furcular morphology is highly variable in crown-group avians but is rather conserved among nonavian theropods. Here we review, or describe for the first time, the furculae in many nonavian theropods. Furculae occur in nearly all major clades of theropods, as shown by new theropod specimens from the Early Cretaceous of China and a close inspection of previously collected specimens. Informative phylogenetic characters pertaining to the furcula occur throughout Theropoda, though care should be take to consider taphonomic effects when describing furcular morphology.

Another New Paleontology Blog - The Theatrical Tanystropheus

A new blog has come to my attention called "The Theatrical Tanystropheus" and is written by Mark Mancini, a student at Mesalands Community College in Tucumcari New Mexico. Mark is a student of "Herr Doktor" Axel Hungerbuehler and therefore is being properly exposed to the Triassic, which he features often in his posts.

You can check it out for yourself at: http://tanystropheus.wordpress.com/

Separating the Rock Point from the Chinle

ResearchBlogging.org

William R. Dickinson, George E. Gehrels (2006). U-Pb ages of detrital zircons in Jurassic eolian and associated sandstones of the Colorado Plateau: Evidence for transcontinental dispersal and intraregional recycling of sediment Geological Society of America Bulletin, preprint (2008) DOI: 10.1130/B26406.1

Following on the heels of their earlier paper on Triassic paleodrainage pattern in North American (Dickinson & Gehrels, 2008) is this new paper in GSA Bulletin using detrital zircons to determine the provenance of Jurassic rocks (Glen Canyon and San Rafael Groups) of the Colorado Plateau. The exact location of the Triassic/Jurassic boundary in western North America has long been an issue of contention as has the exact correlations of many of the units. A redbed siltstone unit underlying the Wingate Sandstone was given two names, in Arizona it was named the Rock Point Member of the Wingate Sandstone (Harshbarger et al., 1957), whereas in Utah it was named the Church Rock Member of the Chinle Formation. The Triassic/Jurassic boundary was traditionally placed between the tops of these units and the overlying Wingate Sandstone (e.g., Stewart, 1957). Dubiel (1989) assigned the Rock Point as a member of the Chinle Formation and Lucas (1993) raised it to formational rank along with his rank increase of the Chinle to a group. Lucas and Hunt (1992) also assigned strata (the siltstone member of the Chinle Formation) above the Petrified Forest Member in the Chama Basin of New Mexico to the Rock Point Formation. Recently Zeigler et al. (2008) argued that based on differing paleomagnetic polarities, the siltstone member and the Rock Point could not be the same unit. Furthermore Zeigler and Geissman (2008) demonstrated that the siltstone member possesses a magnetic paleo pole similar to the Moenave Formation. Although alternatively considered Triassic (pre-1950s) or Jurassic (post-1950s) the strata in the lower part of the Moenave Formation, as well as the base of the Wingate Sandstone) are now believed to be Late Triassic in age based mained on vertebrate biostratigraphy (e.g., Lucas and Tanner, 2007).

The new paper by Dickinson and Gehrels also considers the basal Wingate and Moenave to be Late Triassic; however, based on detrital zircon provenance they consider the lower Moenave and the Rock Point/Church Rock to be lateral equivalents and remove the Rock Point/Church Rock from the Chinle Formation. This makes the top of the Owl Rock Member the top of the Chinle Formation, placing the Rock Point back into the Glen Canyon Group. In the Moab/Arches area the "black ledge" sandstone (at the base of the Church Rock Member) forms the base of the Glen Canyon Group, and the Church Rock is now part of the Glen Canyon Group as well.

Going back to the recent work by Zeigler et al. (2008) and Zeigler and Geissman (2008) regarding the stratigraphic position and nomenclature of the siltstone member. Based on the paleo pole the siltstone member as equivalent to the Moenave is supported by Dickinson and Gehrel's work; however, the issue of the differing magnetic polarities is circumstantial evidence that the Rock Point and siltstone member are not the same unit. Stratigraphic correlation is based on lithologic similarities and it is possible that the Rock Point between northern Arizona, Utah, and New Mexico is time transgressive as depostion is not always synchronous. It would be interesting to test the paleomagnetism of other Rock Point/Church Rock outcrops for comparison. Also unresolved is the lack of Owl Rock strata in Northern New Mexico. Dubiel (1989) argued that the siltstone member was a lateral equivalent of the Owl Rock and this also needs to be tested by sampling the Owl Rock.

All of this recent work by Kate Zeigler and colleagues as well as Dickinson and Gehrels appears to be raising as many questions as are being answered; however, it appears clear that we are getting closer to finally having a handle on these correlations and nomenclature problems, instead of relaying solely on a single line of evidence, vertebrate biostratigraphy.

REFERENCES

Dickinson, W. R., and G. E. Gehrels. 2008. U-Pb ages of detrital zircons in relation to paleogeography: Triassic paleodrainage networks and sediment dispersal across southwest Laurentia. Journal of Sedimentary Research 78:745-764.

Dubiel, R.F., 1989, Sedimentology and revised nomenclature for the upper part of the Upper Triassic Chinle Formation and the Lower Jurassic Wingate Sandstone, northwestern New Mexico and northeastern Arizona. New Mexico
Geological Society Guidebook 40:213–223.

Harshbarger, J.W., Repenning, C.A., and J.H. Irwin. 1957. Stratigraphy of the Uppermost Triassic and the Jurassic Rocks of the Navajo Country: U.S. Geological Survey Professional Paper 291, 74 p.

Lucas, S.G. 1993. The Chinle Group: revised stratigraphy and biochronology of Upper Triassic nonmarine strata in the western United States. Museum of Northern Arizona Bulletin.

Lucas, S.G., and A.P. Hunt. 1992. Triassic stratigraphy and paleontology, Chama Basin and adjacent areas, northcentral New Mexico. New Mexico Geological Society Guidebook 43:151–172.

Lucas, S.G., and L.H. Tanner. 2007. Tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 244:242–256.

Stewart, J.H. 1957. Proposed nomenclature of part of Upper Triassic strata in southeastern Utah: The American Association of Petroleum Geologists Bulletin 41:441–465.

Zeigler, K.E., and J.W. Geissman. 2008. Magnetostratigraphy of the Upper Triassic Chinle Group and Implications for the Age and Correlation of Upper Triassic Strata in North America. Geological Society of America Abstracts with programs (online).http://a-c-s.confex.com/crops/2008am/webprogram/Paper47897.html

Zeigler, K. E., Kelley, S., and J. W. Geissman. 2008. Revisions to stratigraphic nomenclature of the Upper Triassic Chinle Group in New Mexico: New insights from geologic mapping, sedimentology, and magnetostratigraphic/paleomagnetic data. Rocky Mountain Geology 43:121-141.

The Tragic Tale of Machaeroprosopus and Acompsosaurus

In 1914 Maurice Mehl (then at the University of Wisconsin-Madison) collected vertebrate material from the Chinle Formation near Cameron Arizona and near Fort Wingate New Mexico. Work that resulted in the discovery of a nearly complete phytosaur skull and the large sacrum of a "new form" (UW 3811), which he named Acompsosaurus ("sturdy lizard")wingatensis (Mehl, 1915). A full description of this material followed a year later in which Mehl et al. (1916) erected a new genus of phytosaur, Machaeroprosopus ("knife face"), for the skull from near Cameron, with the type species of M. validus. The descriptions of these specimens are good; however, whereas the 1916 paper contains a photographic plate (albeit very poor) of the type specimen of A. wingatensis; the holotype skull (UW 3807) of M. validus is only represented by line drawings. Furthermore, although Mehl et al. (1916) mention the presence of osteoderms with the type of A. wingatensis, unfortunately they do not describe or figure these elements as they can be diagnostic for aetosaurs.

In 1922, Mehl assigned another new species of phytosaur from New Mexico (although he erroneously says Arizona in the article title), M. andersoni, to the genus Machaeroprosopus and in 1928 erected another new genus, Pseudopalatus ("false palate"), for a skull (P. pristinus) from the Petrified Forest of Arizona (Mehl, 1922; 1928).

In his classic 1930 monograph on the phytosaurs, Charles Camp assigned five new species to Machaeroprosopus (M. adamanensis, M. lithodendrorum, M. zunii, M. tenuis, and M. gregorii). He also argued that Pseudopalatus pristinus was very similar to M. tenuis and assigned it to the genus Machaeroprosopus although as a distinct species (Camp, 1930).

Despite that no new species were assigned to the genus after 1930, the name Machaeroprosopus was heavily used in the literature until Joseph Gregory's revision of the phytosaurs in 1962. Gregory (1962) considered Machaeroprosopus to be a junior synonym of the east coast taxon Rutiodon and assigned all of the species, with the exception of M. gregorii, which he assigned to Phytosaurus, to that genus; however, he also noted that he was not able to examine the holotype of M. validus as it could not be located.

Westphal (1979) brought attention to the missing holotype of M. validus, noting that it had been missing since about 1958 (presumably when Joe Gregory went to see it), and asking if anyone had any information on the specimen.

Previously Gregory (1953) had also addressed the taxonomic status of Acompsosaurus, which he recognized to represent the pelvis of an aetosaur; however, he notes that has "not been able to examine the specimen). Gregory (1953) suggested that Acompsosaurus may be a synonym of Typothorax (comparing to T. meadei, which is now Longosuchus).

However, one researcher who had examined the material was E.C. Case, who in 1929 wrote that he "had the opportunity to study the specimen [A. wingatensis holotype] in the museum of the University of Wisconsin". Unfortunately this is the last documentation of a worker examining the holotype. I assume that Case studied the skull of M. validus as well as he never mentions it as missing in any of his subsequent phytosaur work.

The type specimen of M. validus became of importance again in 1989 when Karen Ballew removed R. pristinus and R. tenuis and restored the genus Pseudopalatus with P. tenuis as a junior synonm of P. pristinus. This is because Ballew (1989) and subsequent authors consider M. validus, based on the description and line drawings, to be very similar (if not identical) to Pseudopalatus. Thus, if the missing holotype were found, Pseudopalatus would be a junior synonym of Machaeroprosopus and that genus name would once again be valid. M. validus is also unique and thus important in that is is the only phytosaur with a purported 'overbite' in that the upper jaws protrude much more anteriorly than the lower jaws; however, this condition can only be ascertained by direct inspection of the specimen. Drawing below from Mehl et al. (1916).



The holotype of Acompsosaurus is also of importance because based on existing descriptions and its stratigraphic position it probably represents an aetosaur similar if not identical to Calyptosuchus (Stagonolepis) wellesi, named by Long and Ballew (1985). Thus, it too would be a valid taxon, although possibly as Stagonolepis wingatensis. Drawing below from Mehl et al. (1916).

So what happened to the the type specimens of M. validus and A. wingatensis? E. C. Case was the last documented worker to study them in the late 1920s and by the time Joe Gregory goes to see them in the late 1950s they are missing. Interestingly, Colbert (1947) assigned a beautiful skull from Arizona to Machaeroprosopus and in the paper provides skull measurements for M. validus that are not in Mehl et al. (1916). Did Colbert examine the specimen personally? Unfortunately he does not say, only stating in the acknowledgments that he examined the Berkeley material referred to the genus by Camp (1930). Thus all we can say is that the specimens were probably lost at some point between 1929 and 1958. Mehl moved to the University of Missouri in the 1920s and died in 1966.

A few years back I met a gentlemen at a meeting, the name escapes me now, who told me a story of being a graduate student at the University of Wisconsin-Madison in the 1950s - 1960s. He said that the museum hired a new curator who was a crinoid specialist. To make more room for his beloved crinoids, this gentleman disposed of some of the "old reptiles" in the dumpster! However, he did believe that the curator may have given the skull to the biology department. (Note: I am not trying to demean crinoids or people who study them, I am just relating the story as it was told to me).

I have since contacted the geology and biology departments inquiring about these specimens but to no avail and have not been able to corroborate this story; however, since researching this post I became aware that the UW Museum still exists and plan to contact them soon.

REFERENCES

Ballew, K.L. 1989. A phylogenetic analysis of Phytosauria (Reptilia: Archosauria) from the Late Triassic of the western United States, p. 309-339. In S. G. Lucas and A. P. Hunt (eds.), Dawn of
The Age of Dinosaurs in the American Southwest. New Mexico
Museum of Natural History, Albuquerque.

Camp, C.L. 1930. A study of the phytosaurs with description of new material from western North America. University of California Memoir 10:1-161.
Colbert, E.H. 1947. Studies of the phytosaurs Machaeroprosopus and Rutiodon. Bulletin of the American Museum of Natural History 88:57-96.

Gregory, J. T. 1953. Typothorax and Desmatosuchus. Postilla 16:1-27.

Gregory, J.T. 1962. The genera of phytosaurs. American Journal of Science 260:652-690.

Long, R.A., and K.L. Ballew. 1985. Aetosaur dermal armor from the Late Triassic of southwestern North America, with special reference to material from the Chinle Formation of Petrified Forest National Park. Museum of Northern Arizona Bulletin 54:45-68.

Mehl, M.G. 1915. New reptiles from the Trias of Arizona and New Mexico. Science 41:735.

Mehl, M.G. 1922. A new phytosaur from the Trias of Arizona. Journal of Geology 30:144-157.

Mehl, M.G. 1928. Pseudopalatus pristinus, a new genus and species of phytosaur from Arizona. University of Missouri Studies 3:1-22.

Mehl, M.G., Toepelmann, W.C., and G.M. Schwartz. 1916. New or little known reptiles from the Trias of Arizona and New Mexico with notes from the fossil bearing horizons near Wingate, New Mexico. University of Oklahoma Bulletin 103:1-44.

Westphal, K.W. 1979. Missing holotype of Machaeroprosopus validus (Mehl, 1916). Journal of Paleontology 53:741.

Another One!

I promise that I will write a real post soon, but here is another new Triassic temnospondyl paper! We just cannot seem to get enough temnospondyl papers these days...

Maganuco, S., and G. Pasini. 2009. A new specimen of trematosaurian temnospondyl from the Lower Triassic of NW Madagascar, with remarks on palatal anatomy and taxonomic affinities. Atti della Societtaliana di scienze naturali e del Museo civico di storia naturale di Milano 150:91-112.
Abstract - A new partial skull (preserved as a natural mould) of a trematosaurid temnospondyl from the Lower Triassic of the Ankitokazo Basin, Diégo Suarez Province, NW Madagascar, is described. It provides new information on the palatal anatomy, poorly known in the Malagasy trematosaurids, the more important concerning the morphology of the cultriform process, which is squared in cross section and comparatively wide. The new specimen represents a taxon well distinct from both Malagasy lonchorhynchine trematosaurid Wantzosaurus elongatus and other trematosaurid genera known out of Madagascar. The taxonomic and phylogenetic affi nities found between the new skull and all the Malagasy non-lonchorhynchine specimens so far described suggest that the material may belong to a single species, closely related to the German species Trematolestes hagdorni, and more similar to Tertrema acuta than to Trematosaurus brauni. The new skull is therefore tentatively referred to cf. Tertremoides madagascariensis, the only non-lonchorhynchine trematosaurid species from Madagascar that we regard as valid, following the systematic review by Schoch & Milner (2000).

This paper also cites an in press publication....

Maganuco S., Steyer J. S., Pasini G., Boulay M., Lorrain S., Bénéteau A. & Auditore M., in press – An exquisite specimen of Edingerella madagascariensis (Temnospondyli) from the Lower Triassic of NW Madagascar; cranial anatomy, phylogeny and restorations. Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano.

Both of these papers are from Simone Maganuco's PhD dissertation.

Reconstruction is Trematosaurus from Wikipedia commons.

Another New Reference and Amazingly Productive Publishing Paleontologists

This one just missed my "Latest Literature" post a few days back. I had commented earlier how 2008 was an amazing year for new temnospondyl papers (and basal turtles) and here is another in early 2009 (although it had been in press since 2007!).

By the way...I am often just blown away by the productivity of some vertebrate paleontologists. I recently linked to Richard Butler's webpage and here now is Rainer Schoch's. Just look at his upcoming output which includes the new paper featured here. Not only do these individuals produce so many papers, but they are all consistantly excellent. Hat's off to Drs. Schoch and Butler!

Damiani, R., Schoch, R.R., Hellrung, H., Werneburg, R., and S. Gastou. 2009. The plagiosaurid temnospondyl Plagiosuchus pustuliferus (Amphibia: Temnospondyli) from the Middle Triassic of Germany: anatomy and functional morphology of the skull. Zoological Journal of the Linnaean Society 155:348-373. doi:10.1111/j.1096-3642.2008.00444.x

Abstract: The cranial anatomy of the plagiosaurid temnospondyl Plagiosuchus pustuliferus, from the Middle Triassic of Germany, is described in detail on the basis of a newly discovered skull and mandibular material. The highly derived skull is characterized by huge orbitotemporal fenestrae, a reduction of the circumorbital bones – the prefrontal, postfrontal and (probably) postorbital are lost – and the expansion of the jugal to occupy most of the lateral skull margin. Ventrally the extremely long subtemporal vacuities correlate with the elongate adductor fossa of the mandible. The dentition is feebly developed on both skull and mandible. Ossified
?ceratobranchials and 'branchial denticles' indicate the presence of open gills clefts in life. The remarkably divergent cranial morphology of P. pustuliferus highlights the extraordinary cranial diversity within the Plagiosauridae, probably unsurpassed within the Temnospondyli. Specific structural aspects of the skull – including an extremely short marginal tooth row, feeble dentition and an elongated chamber for adductor musculature – together with evidence for a hyobranchial skeleton, suggests that P. pustuliferus utilized directed suction feeding for prey capture.

I have always wondered why temnospondyls are often given names that end with -saurus and suchus?