Field of Science

Triassic Ornithischian? Krzyzanowskisaurus hunti revisited.

http://www.azstarnet.com/news/local/article_d4138dc4-60a2-544c-8ba8-45ed550df2c2.html

The Arizona Daily Star (Tucson, AZ), published this story earlier on local fossil collector Stan Krzyzanowski. Those of you familiar with dinosaur taxonomy may recognize the name in regards to the Triassic tooth taxon Krzyzanowskisaurus hunti, to which the story alludes.

This taxon, known from only a handful of isolated teeth, was originally described as a new species of the putative ornithichian dinosaur Reveultosaurus by Heckert (2002). When it was subsequently discovered that the type species of Revueltosaurus, R. callenderi, actually represented a non-dinosaurian pseudosuchian archosaur (Parker et al. 2005), Heckert (2005) referred R. hunti to this new genus, Krzyzanowskisaurus. Heckert's (2005:77) support for this new referral is that the teeth of K. hunti "appear more derived than R. callenderi, and are in fact more 'typically' ornithischian than those of R. callenderi". By more 'typically' ornithischian Heckert (2005:78) is referring to the presence of a "pronounced bulge on the lingual surface", which he hypothesizes as being homologous with the 'cingulum' found in basal ornithischian teeth. However, there is no strong evidence for this homology and thus there are no apomorphies whatsoever to support the referral of K. hunti to Ornithischia (Irmis et al. 2007). Likewise, no phylogentic analysis exists to support the claim that this tooth morphology would be more derived. In fact co-occurring fossils from the St. Johns area actually support the original referral of these teeth to Revueltosaurus, thus I maintain that no material from North America currently exists that can be unambiguously referred to Ornithischia (Parker et al. 2005; Nesbitt et al. 2007; Irmis et al. 2007), and the reconstruction below is most likely erroneous (and apparently plagiarized from Greg Paul, see the copyright and read the comments below).



The Krzyzanowski bonebed is a potentially interesting vertebrate microsite from the Chinle Formation near St. Johns (similar to sites in the same area collected by Charles Camp in the late 1920s), but to date has only received limited coverage in publications (e.g., Heckert et al. 2004; Heckert et al. 2005), including a claim by these authors as to the presence of what would be the only sauropodomorph material from the Upper Triassic of North America (besides Greenland, which is physiogeographically considered part of that continent).

REFERENCES

Heckert, A.B. 2002. A revision of the upper Triassic ornithischian dinosaur Revueltosaurus, with a description of a new species. New Mexico Musuem of Natural History and Science Bulletin 21:253–267.

Heckert, A.B. 2005. Krzyzanowskisaurus, a new name for a probable ornithischian dinosaur from the upper Triassic Chinle Group, Arizona and New Mexico, USA. New Mexico Museum of Natural History and Science Bulletin 29: 77–83.
Heckert, A.B., Lucas, S.G., and A.P. Hunt. 2005. Triassic vertebrate fossils in Arizona. New Mexico Museum of Natural History and Science Bulletin 29:16-44.

Heckert, A. B., Rinehart, L. F., Krzyzanowski, S. E., Lucas, S. G., and S.K. Harris. 2004. The Krzyzanowski bonebed: an Upper Triassic (Adamanian: latest Carnian) vertebrate fauna and its implications for microvertebrate studies. New Mexico Geology 26:64.

Irmis, R.B., Parker, W.G., Nesbitt, S.J., and J. Liu. 2006. Early ornithischian dinosaurs: the Triassic record. Historical Biology 19:3-22.
Nesbitt, S.J., Irmis, R.B., and W.G. Parker. 2007. A critical re-evaluation of the Late Triassic dinosaur taxa of North America. Journal of Systematic Palaeontology 5:209-243.

Parker, W.G., Irmis, R.B., Nesbitt, S.J., Martz, J.W., and L.S. Browne. 2005. The
Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. Proceedings of the Royal Society of London, B 272:963–969.
The image above is from the linked article.

Triassic Fish Faunas of Western Argentina

Lopez-Arbarello, A., Rauhut, O.W.M, and E. Cerdeno. 2010. The Triassic fish faunas of the Cuyana Basin, western Argentina. Palaeontology doi: 10.1111/j.1475-4983.2010.00931.x

Abstract - The continental deposits of the Cuyana Basin, western Argentina, have yielded the most diverse, but so far almost unstudied, Triassic ichthyofaunas of South America. Here, we review these faunas and show that only eight of the 29 named taxa can be considered valid, including the chondrostean Neochallaia, the acrolepid Challaia, Guaymayenia, a taxon of uncertain affinities, and five species of the perleidiform family Pseudobeaconiidae. The first three taxa most probably come from Middle Triassic sediments, while the pseudobeaconiids are of Late Triassic age. Other material, although not diagnostic, probably represents other species, and thus, the diversity of actinopterygians in the Cuyana basin is certainly higher than currently recognized. For the Late Triassic fish fauna, the absence of crown-group neopterygians and a single record of a sarcopterygian is noteworthy and probably indicates some degree of endemism in this fauna, also supported by the high abundance of pseudobeaconiids, which are unknown from other areas. Furthermore, on the basis of the age indicated by the fishes and the available geological information, we discuss the age of the local fauna of the Cerro Bayo, close to the city of Mendoza, and the Agua de la Zorra Formation, Uspallata.

Revised Stratigraphy of the Sonsela Member (Chinle Formation) in the Southern Part of Petrified Forest National Park, Arizona

One of the immediate problems facing me when I started working at Petrified Forest National Park in 2001 was the inability to often locate myself stratigraphically using existing lithostratigraphic models. This became particularly irksome in the winter of 2001 when I recovered a partial skeleton of the aetosaur Calyptosuchus wellesi from just below a prominent sandstone ledge in the central portion of the park. Calyptosuchus (=Stagonolepis) has been proposed as a biochronological index fossil of the Adamanian land vertebrate faunachron, which at that time was considered to represent the latest Carnian. The existing lithostratigraphic scheme divided the Petrified Forest Member of the Chinle Formation into upper and lower parts using a local sandstone called the Sonsela Sandstone bed. A major part of the problem was that various researchers differed on exactly what sandstone ledges in the park (and there are many) represented the Sonsela. Revisions by Andrew Heckert and Spencer Lucas in the Spring of 2003 (Heckert & Lucas, 2003 [imprint 2002]) and later that year by NAU graduate student Daniel Woody (Woody 2003, 2006) looked to address this problem by expanding the Sonsela Member to include more of these beds and to provide hypotheses of correlation. Unfortunately, attempts to map the park in 2006 at the 1:24000 scale realized that the new proposed correlations looked great on paper, but didn't work at the outcrop or on the map (Raucci et al., 2006). This reinforced doubts I was already having because of difficulty using the new scheme in the field, and simply stating that it represented a complex fluvial system wasn't helping.

In 2008 Jeff Martz was hired in a seasonal position at the park. Jeff had just completed his dissertation at Texas Tech University solving similar problems in the Upper Triassic Dockum Group of west Texas. Realizing that this was a perfect opportunity to examine and hopefully solve this problem once and for all I dragged him out to an area of the park known as the Flattops, near the center of one of the more stratigraphically challenging areas of the park. The Flattops area contains three prominent sandstone horizons termed the Flattops Sandstones #2-4 (Billingsley, 1985) which are only found in this area and restricted in their lateral extent. One of the points Jeff had stressed in his dissertation was the need to completely walk out beds in areas with complex stratigraphy in order to ascertain the proper superpositional relationships and correlations of beds. In the past a lot of this had been done using correlated measured sections or seemingly by 'eyeballing it'. I placed us on top of what was unambiguously Flattops Sandstone #2 and we proceeded to walk out numerous beds in the Sonsela Member. At first we assigned alpha names to each bed (e.g., A, B, C) and did not change these to existing bed level names until we could directly correlate to the 'type sections' for those beds. Fairly quickly we were able to work out most of the major correlations and superpositional relationships. We also were able to directly tie in all of our known fossil sites, including the site that had given me so much trouble since 2001.

The results of this work, which differs in significant ways from that of all previous workers, will be published on Friday, February 19th in the open access journal PLoSONE - Martz & Parker 2010. The media embargo ended today (Feb. 18th) and the paper is actually available now.

Figuring out the stratigraphic relationships of the southern portion of the park has allowed us to see support for various hypothesis regarding the depositional systems and biostratigraphy of the park, including the position of the Adamanian-Revueltian boundary (a proposed faunal and possibly floral turnover event; Parker & Martz, 2009). We have also been successful in correlating the northern and southern ends of the park, something that no previous researcher has been able to do conclusively. This allows us to amalgamate biostratigraphic data from both areas, allowing for a more robust biostratigraphic hypothesis. We are currently working on correlating other Chinle Formation outcrops in Arizona back to the park in hopes of developing regional lithostratigraphic and biostratigraphic models. A paper detailing our biostratigraphic hypotheses has been submitted and a paper discussing the north end stratigraphy and another on regional correlations are in the works.

One of the things we have tried to do with the PLoS ONE paper is to make our study completely reproducible. This was a problem we had with many of the past studies, rendering much of their data unusable. For example, stratigraphic measured sections can be highly subjective both in terms of where on the outcrop it was measured as well as how the individual units were broken out. In complex fluvial systems where beds can thicken, thin, or pinch out laterally over very short distances the ability to precisely relocate where a section was done is very important. To this end we have provided (and advocate that all future studies also do this) GPS coordinates as well as photos of all measured outcrops, showing not only the location but how the outcrop was separated into units. We also provide a copy of our geological map. Mapping was crucial to the determining of correlations, and as is stated in the paper, we have doubts about stratigraphic correlations made without the tool of geological mapping. Furthermore, any proposed mistakes in our work can be easily verified or refuted by future workers by using the map. Very important!

This project has been a lot of work, but also a lot of fun and it is refreshing that I can pretty much accurately place myself stratigraphically anywhere in the park. This is crucial for accurate plotting of fossil sites and for determining stratigraphic ranges of organisms. I hope that our colleagues find this work extremely useful for their own studies on the Chinle Formation as well.

Martz, J.W., and W.G. Parker. 2010. Revised lithostratigraphy of the Sonsela Member (Chinle Formation, Upper Triassic) in the southern part of Petrified Forest National Park, Arizona. PLoSONE 5(2)e9329. doi:10.1371/journal.pone.0009329

ABSTRACT

Background: Recent revisions to the Sonsela Member of the Chinle Formation in Petrified Forest National Park have presented a three-part lithostratigraphic model based on unconventional correlations of sandstone beds. As a vertebrate faunal transition is recorded within this stratigraphic interval, these correlations, and the purported existence of a
depositional hiatus (the Tr-4 unconformity) at about the same level, must be carefully re-examined.

Methodology/Principal Findings: Our investigations demonstrate the neglected necessity of walking out contacts and mapping when constructing lithostratigraphic models, and providing UTM coordinates and labeled photographs for all measured sections. We correct correlation errors within the Sonsela Member, demonstrate that there are multiple Flattops
One sandstones, all of which are higher than the traditional Sonsela sandstone bed, that the Sonsela sandstone bed and Rainbow Forest Bed are equivalent, that the Rainbow Forest Bed is higher than the sandstones at the base of Blue Mesa and Agate Mesa, that strata formerly assigned to the Jim Camp Wash beds occur at two stratigraphic levels, and that there are
multiple persistent silcrete horizons within the Sonsela Member.

Conclusions/Significance: We present a revised five-part model for the Sonsela Member. The units from lowest to highest are: the Camp Butte beds, Lot’s Wife beds, Jasper Forest bed (the Sonsela sandstone)/Rainbow Forest Bed, Jim Camp Wash beds, and Martha’s Butte beds (including the Flattops One sandstones). Although there are numerous degradational/
aggradational cycles within the Chinle Formation, a single unconformable horizon within or at the base of the Sonsela Member that can be traced across the entire western United States (the ‘‘Tr-4 unconformity’’) probably does not exist. The shift from relatively humid and poorly-drained to arid and well-drained climatic conditions began during deposition of the Sonsela Member (low in the Jim Camp Wash beds), well after the Carnian-Norian transition.

REFERENCES

Billingsley, G. H.,1985. General stratigraphy of the Petrified Forest National Park, Arizona. Museum of Northern Arizona Bulletin 54:3-8.

Heckert, A.B., and S.G. Lucas. 2002. Revised Upper Triassic stratigraphy of the Petrified Forest National Park. New Mexico Museum of Natural History and Science Bulletin 21:1-36.

Martz, J.W., and W.G. Parker. 2010. Revised lithostratigraphy of the Sonsela Member (Chinle Formation, Upper Triassic) in the southern part of Petrified Forest National Park, Arizona. PLoSONE 5(2)e9329. doi:10.1371/journal.pone.0009329

Parker, W. G., and J. W. Martz. 2009. Constraining the stratigraphic position of the Late Triassic (Norian) Adamanian-Revueltian faunal transistion in the Chinle Formation of Petrified Forest National Park, Arizona. Journal of Vertebrate Paleontology 29(3):162A.

Woody, D. T., 2003. Revised geological assessment of the Sonsela Member, Chinle Formation, Petrified Forest National Park, Arizona. Unpublished M. S. Thesis, Northern Arizona University, Flagstaff.

Woody, D. T., 2006. Revised stratigraphy of the lower Chinle Formation (Upper Triassic) of Petrified Forest National Park, Arizona. Museum of Northern Arizona Bulletin 62:17-45.

Reptile Assemblage from the Middle Triassic Moenkopi Formation of New Mexico

A very well-written and detailed paper demonstrating the importance of apomophy based identifications when assigning scrappy material to taxa for accurate determination of faunal assemblages. Further demonstrates the abundance of archosaurs, including primitive poposauroids and a possible shuvosaurid, in the Early to Middle Triassic rocks of the American Southwest.

Schoch, R. R., Nesbitt, S. J., Mueller, J. M., Lucas, S. G., and J. A. Boy, J. A. 2009, The reptile assemblage from the Moenkopi Formation (Middle Triassic) of New Mexico. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, DOI: 10.1127/0077-7749/2009/0030; Stuttgart.

Abstract: Focused collecting and excavation in the Moenkopi Formation (Anton Chico Member)of north-central New Mexico yielded a large quantity of tetrapod bones. Most of the finds were collected from intraformational conglomerates, and consist of isolated bones or bone fragments. The most abundant large members of the assemblage, the archosaurs, include at least three taxa: (1) a primitive suchian or archosauriform, (2) a primitive poposauroid (Arizonasaurus babbitti), and (3) a taxon similar to shuvosaurids. Less abundant remains are tentatively referred to archosauromorphs with rhynchosaur affinities. An analysis of the tetrapod Lagerstätten reveals that primary deposits formed in lakes that were located on floodplains. In these lakes, autochthonous conchostracans, actinopterygians, coelacanths, and temnospondyls were evidently preserved. Fluvial reworking of lacustrine deposits resulted in a secondary deposition of bones, teeth, coprolites, and wood in channel-borne conglomerates. However, the large amount of elements from terrestrial tetrapods indicates that these conglomerates acquired bones from additional primary deposits (?channels, paleosols?) that are still unknown.

A Well-preserved Thallatosaur and new Evidence on the First Appearance of Angiospermy in the Mesozoic

Things have been a bit slow in Triassic-land lately and I've been too busy to be creative; however, Jeff has posted some new pics over at Paleo Errata as things start to thaw out in some places.

There is one recent paper on on Triassic marine reptiles from China:

Zhao, L.-J., Sato, T., Liu, J., Li, C., and X.-C. Wu. 2010. A new skeleton of Miodentosaurus brevis (Diapsida:Thalattosauria) with a further study of the taxon. Vertebrata Palasiatica 48:1-10.

Abstract: A new thalattosaurian skeleton from the Upper Triassic Wayao Member of the Falang Formation, Guanling area, Guizhou Province, China can be referred to Miodentosaurus brevis. The postcranial skeleton of the specimen is well-preserved and so complete that it is worthy to be described. This new specimen provides a full knowledge of the osteology of the thalattosaurian, especially the anatomy of the pectoral girdle and both the fore and hindlimbs. The presence of a few teeth restricted to the anterior ends of both the upper and lower jaws and dorsoventrally flattened ungual phalanges indicate that M. brevis is not a pure carnivore. With new information, some individual variations are recognized and the digital formula(2-3-4-5-5) of the pes can be identified as one of the diagnostic features for the thalattosaurian.


This also may be of interest, although not containing a phylogenetic analysis, the seed plant described here is proposed to be the 'sister taxon' of angiosperms and thus angiospermy evolved more than once in separate groups, or it is derived from a common ancestor in the Triassic or early Jurassic.


Wang, X., and S. Wang. 2010. Xingxueanthus: An Enigmatic Jurassic Seed Plant and Its Implications for the Origin of Angiospermy. Acta Geologica Sinica [English Edition] 84:47-55.

Abstract: The origin of angiosperms has been tantalizing botanists for centuries. Despite the efforts of palaeobotanists, most of the pre-Cretaceous angiosperms are regarded either non convincing or misdated. The applications of SEM and LM (light microscope) enable us to recognize a coalified fossil plant, Xingxueanthus sinensis gen. et sp. nov., from the Haifanggou Formation (Middle Jurassic, >160 Ma) in western Liaoning, China. Xingxueanthus is an ''inflorescence'' with more than 20 female units spirally arranged. Each female unit is situated in the axil of a bract. The female unit is composed of an ovule-container and a style-like projection at the top. There is a vertical column bearing several ovules in the ovule-container. The general morphology and the internal structure of Xingxueanthus distinguish itself from any known fossil and extant gymnosperms, and its structures are more comparable to those of angiosperms. Xingxueanthus, if taken as a gymnosperm, would represent a new class, demonstrate an evolutionarily advanced status of ovule-protection in gymnosperms never seen before, and provide new insights into the origin of angiospermy. Alternatively, if taken as an angiosperm, together with Schmeissneria, it would increase the diversity of Jurassic angiosperms, which has been underestimated for a long time, and suggest a much earlier origin of angiospermy than currently accepted.

New Juvenile Specimen of Lufengosaurus huenei from the Lower Jurassic of China

Sekiya, T., and Dong, Z. 2010. A New Juvenile Specimen of Lufengosaurus huenei Young, 1941(Dinosauria: Prosauropoda) from the Lower Jurassic Lower Lufeng Formation of Yunnan, Southwest China. Acta Geologica Sinica (English Version) 84:11-21.

Abstract - A skull and a series of associated cervical vertebrae (ZLJ0112)discovered from the Lower Lufeng Formation (Lower Jurassic) are determined as a juvenile specimen of Lufengosaurus huenei Young 1941 based on amended autapomorphies. Differences between ZLJ0112 and the holotype (subadult specimen) are considered as ontogenetic characteristic changes of L. huenei. Since some of these differences are present in other prosauropod dinosaurs (i.e., forms of the maxillary vascular foramen are irregular; the frontal contribution to the dorsal margin of the orbit is substantial; the frontal contribution to the supratemporal fossa is absent; the supratemporal fenestra is visible in lateral view; the supraoccipital inclined at 75 degrees; the parasphenoid rostrum lies level with the occipital condyle; the retroarticular process is short; the axial postzygapophysis project caudally beyond the end of the centrum) they may be common ontogenetic changes in prosauropod dinosaurs.