I apologize for the hiatus since the last set of posts but I was very busy finishing up my scholastic career, as well as maintain my full-time job, and we as my private life with home and family. I hope to start posting regularly again and possibly even something more than just new paper updates, but we shall see.
This is an article that came out this week on the Colorado Plateau Coring Project work that was completed earlier at Petrified Forest National Park and what we hope to learn from this core. The core is presently being CT scanned at the UT Austin and after that is will be split and the detailed research started.
https://www.ldeo.columbia.edu/news-events/amid-fossil-bonanza-drilling-deep-pre-dinosaurian-rocks
This summer we will continue work on the layer briefly mentioned in the article and video. An extremely fossiliferous layer we affectionately call the 'poop layer' because it is not only chock full of bones (micro- and macro-) but also a predominance of coprolites. I'll post updates on our work during the summer. In the meantime enjoy the article and video.
Showing posts with label Petrified Forest. Show all posts
Showing posts with label Petrified Forest. Show all posts
New Occurrences of the Controversial Late Triassic Plant Fossil Sanmiguelia
New paper extending the biostratigraphic range of the enigmatic Late Triassic plant Sanmiguelia. These new finds also alter the plant-based biostratigraphic scheme proposed by Ash in 1980.
Ash,
S.R. and S. T. Hasiotis, S.T. 2013. New occurrences of the controversial Late
Triassic plant fossil Sanmiguelia Brown and associated ichnofossils in
the Chinle Formation of Arizona and Utah, USA. Neues Jahrbuch für Geologie und
Paläontologie Abhandlungen 268: 65–82.
Abstract:
Fragments
of the rare and distinctive palm-like leaves of the controversial Late Triassic
plant Sanmiguelia have been discovered recently in both Petrified Forest
National Park, Arizona and Arches National Park, Utah. Although, the new
specimens do not clarify the classification of this intriguing fossil, they do
confirm that it occurs in all members of the Chinle Formation except for the
very lowest units, the Shinarump, Mesa Redondo, and Temple Mountain members.
Furthermore, their discovery in Petrified Forest National Park extends the
known geographical distribution of the fossil into east-central Arizona and
demonstrates that it is a characteristic member of the Late Triassic flora of
the American southwest and requires a revision of the Chinle floral zone scheme
proposed and revised earlier by Ash (1980). In Petrified Forest National Park
the leaves are associated with several types of ichnofossils including Scoyenia,
Arenicolites, Cylindrichum, cf. Scolicia, cf. Beaconites,
Selenchnites, and other trace fossils in open nomenclature. These trace
fossils suggest that Sanmiguelia was preserved in high moisture,
imperfectly drained, water-margin setting inhabited by phytosaurs, snails,
horseshoe crabs, and a variety of arthropods such as beetles and dipteran
larvae and record high water table conditions punctuated by flooding and overbank
deposition. The findings reported here generally support and improve on
previous interpretations of the paleoenvironment inhabited by the Sanmiguelia
plant.
The First Published Geological Map of Petrified Forest National Park
Today marks a momentious day in the geological research history of Petrified Forest National Park in Arizona. 35 years ago work began on a draft geological map of the park. Unfortunately the draft, completed in the early 1980s, was never finalized although it served as the basic guide for work through the early 2000s. Around this time the need to update the map was considered and some minor revisions were accomplished. In 2005 the National Park Service contracted with Northern Arizona University to finally complete the map; however, the work was stalled when it was realized that the current stratigraphic schemes used by the park (proposed in 2002 and 2003) could not recreated by the mapping and therefore something was wrong.
In 2008, Jeff Martz and I decided to tackle both the stratigraphic problems as well as revising the park map in the progress. As we discussed in our 2010 stratigraphic revision paper (available for free here), mapping is a crucial part of solving stratigraphic problems, because it involves detailed walking out of beds and really tests your proposed correlations. We walked kilometer after kilometer that first summer, arguing the whole time, but really working out the correlations. Subsequently Jeff took the lead on completing the mapping and after literally wearing his boots down to 'sandals' (they proudly hang in my office today) completed this work in 2010. His map was then painstakingly digitized and finalized by Lisa Skinner at NAU. The report includes some of Jeff's amazing artwork that he is developing a reputation for in the scientific realm. I especially find the cross-section to be particularly telling and useful for individuals to place themselves in the stratigraphy as they progress through the park.
The finished product is now available on-line courtesy of our partners at the Arizona Geological Survey as part of their Contributed Map series, and the map and associated report is available as a free download from here. I'd like to thank Arizona State Geologist Lee Allison for allowing the map to be distributed as part of their publication series and to Mike Conway for putting up with all of our edits through the whole process. I think that Jeff and Lisa in particular did an amazing job finalizing the product and finally after 35 years there is an official map of the park. Now we just need to add the park expansion areas added in 2007 to the present.....
In 2008, Jeff Martz and I decided to tackle both the stratigraphic problems as well as revising the park map in the progress. As we discussed in our 2010 stratigraphic revision paper (available for free here), mapping is a crucial part of solving stratigraphic problems, because it involves detailed walking out of beds and really tests your proposed correlations. We walked kilometer after kilometer that first summer, arguing the whole time, but really working out the correlations. Subsequently Jeff took the lead on completing the mapping and after literally wearing his boots down to 'sandals' (they proudly hang in my office today) completed this work in 2010. His map was then painstakingly digitized and finalized by Lisa Skinner at NAU. The report includes some of Jeff's amazing artwork that he is developing a reputation for in the scientific realm. I especially find the cross-section to be particularly telling and useful for individuals to place themselves in the stratigraphy as they progress through the park.
The finished product is now available on-line courtesy of our partners at the Arizona Geological Survey as part of their Contributed Map series, and the map and associated report is available as a free download from here. I'd like to thank Arizona State Geologist Lee Allison for allowing the map to be distributed as part of their publication series and to Mike Conway for putting up with all of our edits through the whole process. I think that Jeff and Lisa in particular did an amazing job finalizing the product and finally after 35 years there is an official map of the park. Now we just need to add the park expansion areas added in 2007 to the present.....
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!
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| Phytosaur lower jaw in the Crystal Forest |
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| Phytosaur quadrate bone in the Blue Mesa Member |
Introducing Protome batalaria, a New Phytosaur from the Chinle Formation of Petrified Forest National Park, Arizona
In the Fall of 2004 Michelle Stocker and I were out at the Battleship NW fossil locality in Petrified Forest National Park with several researchers from Northern Arizona University. They were working on completing the geological map of the area and had noted that they could not get the current stratigraphic scheme we were using (introduced in 2002) to work out on the map. The stratigraphic position of this quarry was an important issue behind this work as I had just collected a good skeleton of the aetosaur Calyptosuchus wellesi here just above a prominent sandstone that previous workers had correlated to the "Sonsela Sandstone Bed". If this bed correlation was correct then the specimen would be from the Revueltian biozone. This was problematic because Calyptosuchus is considered an index taxon of the Adamanian. As we hemmed and hawed back and forth and discussed various possible correlations to work out these problems, Michelle noted some scraps of bone in unconsolidated sand at top of this bed and very near to where we were standing. She was very surprised, as was I, when she reached down and pulled up part of the skull roof of a phytosaur.
After the NAU researchers moved on to complete their work, we examined Michelle's new "quarry" much closer. By literally sifting our fingers through the loose sand we easily collected numerous parts of the skull including large portions of the rostrum and skull roof. We also uncovered a ramus of the mandible, but this was actually in-situ in the bedrock just underneath the loose sand. We were able to jacket this element, but it was wintertime and I distinctly remember how frozen our hands were after each application of a plaster bandage. Luckily the truck was very nearby, so after each application we would run to the running truck to stick our hands under the heater.
Back in the lab we were able to piece back together much of the skull and it later became part of the focus of Michelle's Masters Thesis. Prior to this Randall Irmis and I mentioned (and figured) this specimen in a 2005 paper where we referred it to "Leptosuchus" adamanensis based on the overall morphology of the squamosals following work by Long and Murry. However, Michelle's detailed phylogenetic analysis in her thesis suggested something different, specifically the specimen did not form a clade with Smilosuchus adamanensis and instead was something else.
In her new paper in the Journal of Vertebrate Paleontology Michelle has described this specimen as a new taxon, which she names Protome batalaria. The name reflects the condition of the specimen, "face of an animal" and where it was found "warship" (for the Battleship Quarry). It can be diagnosed by a unique combination of characters as well as three autapomorphies of the braincase and lower jaw. Her phylogenetic analysis recovers it as a non-pseudopalatine leptosuchomorph.
Important discussion in her paper revolves around the importance of the use of apomorphies to describe and classify specimens. In this particular case past workers (myself) had focused on the generally morphology of the squamosal and robustness of the specimen to make a taxonomic assignment and ignored other discrete apomorphies of the material, which a phylogenetic analysis later determined to be of significance. Thus the longtime practice of assigning isolated phytosaur squamosals to taxa based on general similarity and utilizing these for Late Triassic biochronology is called into question. This general squamosal morphology used to assign (fragmentary and complete) specimens to Rutiodon or Leptosuchus instead just appears to be a shared character of non-pseudopalatine leptosuchomorphs, a paraphyletic assemblage.
As recommended by Michelle it is now necessary to go back to collections such as those from the Petrified Forest and look carefully at all of the specimens assigned to "Leptosuchus" and sort them out using apomorphies. Hopefully this will provide a clear distribution pattern and biochronological signal for these specimens, testing their importance in phytosaur biochronology and biogeography. Overall this new paper provides a great description and discussion that Michelle should be proud of and will be landmark (along with her 2010 paper) for sorting out the labyrinth that is phytosaur taxonomy.
By the way, the stratigraphic problem mentioned at the beginning of this post was finally figured out by Jeff Martz and I in 2009 when we discovered that the bed in question was definitely not the "Sonsela Sandstone Bed", but rather an isolated sandstone lens in the older Lot's Wife Beds and Adamanian in age.
Stocker, M. R. 2012. A new phytosaur (Archosauriformes, Phytosauria) from the Lot’s Wife beds (Sonsela Member) within the Chinle Formation (Upper Triassic) of Petrified Forest National Park, Arizona. Journal of Vertebrate Paleontology 32(3): 573-586 DOI:10.1080/02724634.2012.649815
Abstract - A new phytosaur taxon from Petrified Forest National Park, Arizona, is here described based on cranial material from a single individual. This specimen previously was included in an extensive phylogenetic analysis, and it was found to possess a combination of character states that differs from all known phytosaur taxa in addition to two autapomorphies within the braincase and an autapomorphy of the mandible. The new taxon adds to the taxonomic diversity recognized from the Sonsela Member of the Chinle Formation. The continued increase in phytosaur diversity emphasizes the need to more accurately characterize and identify taxa within a phylogenetic systematic context in order to produce a more refined signal for biostratigraphic correlations, biochronologic inferences, and faunal dynamics during the Late Triassic.
After the NAU researchers moved on to complete their work, we examined Michelle's new "quarry" much closer. By literally sifting our fingers through the loose sand we easily collected numerous parts of the skull including large portions of the rostrum and skull roof. We also uncovered a ramus of the mandible, but this was actually in-situ in the bedrock just underneath the loose sand. We were able to jacket this element, but it was wintertime and I distinctly remember how frozen our hands were after each application of a plaster bandage. Luckily the truck was very nearby, so after each application we would run to the running truck to stick our hands under the heater.
Back in the lab we were able to piece back together much of the skull and it later became part of the focus of Michelle's Masters Thesis. Prior to this Randall Irmis and I mentioned (and figured) this specimen in a 2005 paper where we referred it to "Leptosuchus" adamanensis based on the overall morphology of the squamosals following work by Long and Murry. However, Michelle's detailed phylogenetic analysis in her thesis suggested something different, specifically the specimen did not form a clade with Smilosuchus adamanensis and instead was something else.
In her new paper in the Journal of Vertebrate Paleontology Michelle has described this specimen as a new taxon, which she names Protome batalaria. The name reflects the condition of the specimen, "face of an animal" and where it was found "warship" (for the Battleship Quarry). It can be diagnosed by a unique combination of characters as well as three autapomorphies of the braincase and lower jaw. Her phylogenetic analysis recovers it as a non-pseudopalatine leptosuchomorph.
Important discussion in her paper revolves around the importance of the use of apomorphies to describe and classify specimens. In this particular case past workers (myself) had focused on the generally morphology of the squamosal and robustness of the specimen to make a taxonomic assignment and ignored other discrete apomorphies of the material, which a phylogenetic analysis later determined to be of significance. Thus the longtime practice of assigning isolated phytosaur squamosals to taxa based on general similarity and utilizing these for Late Triassic biochronology is called into question. This general squamosal morphology used to assign (fragmentary and complete) specimens to Rutiodon or Leptosuchus instead just appears to be a shared character of non-pseudopalatine leptosuchomorphs, a paraphyletic assemblage.
As recommended by Michelle it is now necessary to go back to collections such as those from the Petrified Forest and look carefully at all of the specimens assigned to "Leptosuchus" and sort them out using apomorphies. Hopefully this will provide a clear distribution pattern and biochronological signal for these specimens, testing their importance in phytosaur biochronology and biogeography. Overall this new paper provides a great description and discussion that Michelle should be proud of and will be landmark (along with her 2010 paper) for sorting out the labyrinth that is phytosaur taxonomy.
By the way, the stratigraphic problem mentioned at the beginning of this post was finally figured out by Jeff Martz and I in 2009 when we discovered that the bed in question was definitely not the "Sonsela Sandstone Bed", but rather an isolated sandstone lens in the older Lot's Wife Beds and Adamanian in age.
Stocker, M. R. 2012. A new phytosaur (Archosauriformes, Phytosauria) from the Lot’s Wife beds (Sonsela Member) within the Chinle Formation (Upper Triassic) of Petrified Forest National Park, Arizona. Journal of Vertebrate Paleontology 32(3): 573-586 DOI:10.1080/02724634.2012.649815
Abstract - A new phytosaur taxon from Petrified Forest National Park, Arizona, is here described based on cranial material from a single individual. This specimen previously was included in an extensive phylogenetic analysis, and it was found to possess a combination of character states that differs from all known phytosaur taxa in addition to two autapomorphies within the braincase and an autapomorphy of the mandible. The new taxon adds to the taxonomic diversity recognized from the Sonsela Member of the Chinle Formation. The continued increase in phytosaur diversity emphasizes the need to more accurately characterize and identify taxa within a phylogenetic systematic context in order to produce a more refined signal for biostratigraphic correlations, biochronologic inferences, and faunal dynamics during the Late Triassic.
Taphonomic Effects on the Stratigraphic Ranges of Rare Taxa in the Chinle Formation of Arizona
Loughney, K. M., Fastovsky, D. E., and W. G. Parker. 2011. Vertebrate fossil preservation in blue paleosols from the Petrified Forest National Park, Arizona, with implications for vertebrate biostratigraphy in the Chinle Formation. Palaios 26:700-719.
Abstract - Exposures of the Chinle Formation in Petrified Forest National Park (PEFO), Arizona, preserve one of the most important Upper Triassic terrestrial faunal assemblages in the world: in it are found key elements in the global and regional correlation of continental deposits of Upper Triassic age. Rare components of the Chinle Formation faunal assemblage, including dinosaurs and small-bodied amniotes, appear to be mostly restricted to distinctive blue-colored horizons observed at only a few sites in PEFO. The blue sites represent paleosols formed in fine-grained, abandoned channel fills and contrast markedly with red-colored floodplain deposits and paleosols that characterize most fossil localities in the Chinle Formation. The distinctive blue color is interpreted as a weathered feature of hydromorphically reduced iron. The coincidence of rare taxa and sites bearing the blue-colored paleosols suggests that the stratigraphic positions of the sites and the rare taxa they contain appear to relate to fluvial sequence tracts in PEFO and may not reflect the true stratigraphic ranges of these taxa.
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.
You can read a little more about this here and here.
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.
Revisiting Our Summer of Fieldwork at PEFO
It's been a pretty slow week for Triassic-themed papers and events, and I'm pretty swamped trying to complete a couple of manuscripts as well as getting ready for upcoming meetings in Argentina and Las Vegas.
Luckily Susan Drymala is back up and blogging at the Forgotten Archosaurs and has an excellent new post on the beginning of our 2011 summer fieldwork. Please go check it out.
Luckily Susan Drymala is back up and blogging at the Forgotten Archosaurs and has an excellent new post on the beginning of our 2011 summer fieldwork. Please go check it out.
The Petrified Forest on You Tube
Mark Nelson (Teacher-Ranger-Teacher) accompanied us in the field last summer and recorded us discussing some of the geological and paleontological features of the park. He has edited these into 10 - 15 minute clips for You Tube, which is the first time the park has been officially featured on this site. You can check them out at the links below. I think they are not bad for a first attempt, however, I'd like to do some shorter clips (~ 5 mins. max) on some of the behind the scenes stuff at the park as well as explaining other aspects of the paleontology and geology. Anyone have any requests or ideas for some short and interesting clips? I think next time we'll try to be a little more excited... ;).
Current Clips:
Evident Renewal (A visit to the badlands of the Painted Desert located in the Petrified Forest National Park with Bill Parker: paleontologist and Tammo Reichgelt; Utrecht University researcher as they discuss climate change and impacts on Earth's five mass extinctions. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).
Triassic Waters (Follow Bill Parker: Paleontologist and Jeff Martz: Physical Scientist, into the badlands of the Painted Desert as they explore soil erosion and geological formations dating back to the Late triassic Epoch in the Petrified Forest National Park. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).
Mud to Museum (Visit with fossil preparator Kenneth Bader in the Petrified Forest National Park preparation laboratory. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).
Rats, Bats, and Artifacts (Matt Smith, museum curator and preparator takes us on a "behind the scenes" look at the assorted collection of paleo fossils, treasures, and relics in the vaults of the Petrified Forest National Park center. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).
Current Clips:
Evident Renewal (A visit to the badlands of the Painted Desert located in the Petrified Forest National Park with Bill Parker: paleontologist and Tammo Reichgelt; Utrecht University researcher as they discuss climate change and impacts on Earth's five mass extinctions. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).
Triassic Waters (Follow Bill Parker: Paleontologist and Jeff Martz: Physical Scientist, into the badlands of the Painted Desert as they explore soil erosion and geological formations dating back to the Late triassic Epoch in the Petrified Forest National Park. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).
Mud to Museum (Visit with fossil preparator Kenneth Bader in the Petrified Forest National Park preparation laboratory. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).
Rats, Bats, and Artifacts (Matt Smith, museum curator and preparator takes us on a "behind the scenes" look at the assorted collection of paleo fossils, treasures, and relics in the vaults of the Petrified Forest National Park center. Filmed and edited on location by Mark Nelson TRT and Chicago artist 2010).
New Petrified Forest Superintendent Emphasizes Importance of Scientific Research in the Park Including Paleontology
From the Holbrook (Arizona) Tribune:
'Scientists have been unearthing something on the order of one to two new species a year at Petrified Forest National Park for the past few years, and that has new Park Superintendent Brad Traver excited and focused.
“In the last 10 years, we’ve added several new species to science through discoveries at this park. The things found here are influencing the field of study surrounding the Triassic Period. The work of the scientists here is significant,” said Traver, who officially took the helm at the Petrified Forest on May 22.I am excited to be part of this recent surge in our understanding of the park paleontology and geology and hope that we continue to accomplish this essential mission. From day one in the summer of 2001 one of our goals in properly managing the paleontological resources was to build a successful and professional scientific program at the park as well as encouraging and supporting research by partner institutions. Ten years later, park staff and colleagues have published more than 30 papers on the park geology and paleontology, and currently there are more than a dozen institutions conducting detailed paleontological and geological research in the park providing excellent data that allow us to have insight in the approximately 20 million years of history preserved in Chinle Formation strata in the park. In my opinion it is an important and extremely interesting story currently documented by over 800 papers, abstracts, and theses with many more on the way and the potential for hundreds more.
Traver, who has been with the National Park Service for 30 years, has taken up a permanent post at Petrified Forest, where he served as interim superintendent a few years ago.
“I’m thrilled to be headed back to Petrified Forest where I spent a few months in 2007 that were a highlight of my career,” said Traver.
Speaking of what he thinks is significant about the Petrified Forest, Traver said, “Each national park has its unique characteristics. The Petrified Forest has its own scenic beauty, but it isn’t highly scenic on the order of the Grand Canyon, or highly recreational like some of the other parks in the national system.
“This park has primarily a scientific story to tell, and our mission is to produce good science,” he said.
Traver said that mission is being accomplished through increased study of the park’s archeological and paleontological resources by on-site staff along with research partners from various universities and organizations.
Traver anticipates the park’s expansion to encompass the wider boundaries approved by Congress in 2004 will yield even more significant archeological and paleontological finds, including fossils of plants and animals dating 225 million years into the past.'
2011 Field Season at Petrified Forest National Park Officially Starts on Tuesday
This year I will have two student interns, newcomer Susan Drymala from the University of Maryland who some of you may know from her blog Crurotarsi:The Forgotten Archosaurs, and 2009 alumnus Rachel Guest. I'm hoping we will hit the ground running this year so wish us luck. Our goal this year: try to find a bit more of Chindesaurus bryansmalli. I'm planning on blogging quite a bit on what we are doing so stay tuned. It may be at this site or I may start a new site specifically for PEFO fieldwork. I don't know yet. I hope that Susan and Rachel have a blast and enjoy their time doing some intense paleontology at the park for the next 10 weeks or so.
The Petrified Forest Model T: Evidence for Bootleggers in the Painted Desert?
One of the hiking goals of employees and visitors at the Petrified Forest is to make it out to the Model T in the northern Painted Desert Wilderness area. Although it is only about 4 miles out 'as a crow flies', manupulating through the washes and badlands adds a good amount of distance to your trip, so that the total round trip is more like 10 miles with no shade. Plus you have a good trek up a 100+ foot mesa at the very end of your trip.
I've attached a couple of pictures of the "goal" below. The question we always wonder is how did this vehicle get out here in the middle of nowhere? The main story is that the car actually belonged to bootleggers who were transporting alcohol illegally to the nearby Navajo Reservation. There vehicle was stuck in a small wash and mud and abandoned. It is in pretty good shape still. You can sit in the drivers seat and steer and a park ritual is to have your photo taken driving the Model T. A few years back we recorded the serial numbers from the engine block and sent them to Ford in an attempt to track down any ownership records, but to no avail.
One of the cool things about the Petrified Forest is its long history (established in 1906) and all of the hidden 'gems' scattered throughout the park for the more adventurous to find.
I've attached a couple of pictures of the "goal" below. The question we always wonder is how did this vehicle get out here in the middle of nowhere? The main story is that the car actually belonged to bootleggers who were transporting alcohol illegally to the nearby Navajo Reservation. There vehicle was stuck in a small wash and mud and abandoned. It is in pretty good shape still. You can sit in the drivers seat and steer and a park ritual is to have your photo taken driving the Model T. A few years back we recorded the serial numbers from the engine block and sent them to Ford in an attempt to track down any ownership records, but to no avail.
Agathoxylon, the Wood Morphogenus Previously Known as Araucarioxylon
We've known for a couple of years now that the name Araucarioxylon, used for the majority of the petrified wood from the Chinle Formation is illigitimate. Savidge (2007) reexamined the type specimens of Araucarioxylon arizonicum, and assigned it to a new genus, Pullisilvaxylon arizonicum. Problematic is that the type specimen is from the Black Forest Bed, which is much younger than the main log bearing horizon in Petrified Forest National Park where thousands of colorful logs have been referred to A. arizonicum for over a century.
Complicating this problem is that the majority of this wood has been almost completely agatized, obliterating the cellular structures used to make taxonomic assignments. Furthermore, Savidge (2007) found that there are actually several wood taxa at this horizon, in fact almost every specimen sampled turns out to be new. Thus, park staff are at a loss when asked what the name the main type of fossil wood in the park is, and most just simply still continue to use the invalid name Araucarioxylon.
Philippe, in this new paper, suggests that a better name for the morphogenus is Agathoxylon. However, I would be hesitant to refer the large amounts of currently unnamed wood to this genus as he also suggests that eventually it should be restricted to a single species. Furthermore, because of the restriction of the type of P. arizonicum, the majority of Chinle wood lacks a direct assignment to a species-group name. This is a mess that probably will never be resolved because of the poor preservation of the wood structures, thus the majority of Chinle wood will simply be referrable to Araucariaceae indeterminate (or maybe even a more inclusive clade or rank?).
Philippe, M., in press. How many species of Araucarioxylon? C. R. Palevol (2011), doi:10.1016/j.crpv.2010.10.010
Abstract - Fossil wood, similar to that of modern Araucariaceae, has been known for a long time, and is usually called Araucarioxylon. More than 400 morphospecies have been described, whereas this wood type displays few characteristic features. This taxonomical profusion is compounded by nomenclatural problems, Araucarioxylon being an illegitimate name. The status of the wood morphogenus, the infrageneric structure and the names that apply to the taxa designated for fossil woods of the Araucarioxylon-type are discussed. A database with 428 morphospecies designated for Araucarioxylon-type of wood is analyzed. The name Agathoxylon Hartig seems to be the most appropriate for the corresponding morphogenus. Albeit theoretically several hundred morphospecies could be recognized within this group, it is at least as probable that only one should be retained.
REFERENCES
Savidge, R.A. 2006. Xylotomic evidence for two new conifers and a ginkgo within the Late Triassic Chinle Formation of Petrified Forest National Park, Arizona, USA, 147–149. In Parker, W.G., Ash, S.R. & Irmis, R.B. (eds) A century of research at Petrified Forest National Park: geology and paleontology. Museum of Northern Arizona Bulletin 62.
Savidge, R. A. 2007. Wood anatomy of Late Triassic trees in Petrified Forest National Park, Arizona, USA, in relation to Araucarioxylon arizonicum Knowlton, 1889. Bulletin of Geosciences 82:301–328.
Savidge, R.A. & Ash, S.R. 2006. Arboramosa semicircumtrachea, an unusual Late Triassic tree in Petrified Forest National Park, Arizona, USA, 65–81. In Parker, W.G., Ash, S.R. & Irmis, R.B. (eds) A century of research at Petrified Forest National Park: geology and paleontology. Museum of Northern Arizona Bulletin 62.
Complicating this problem is that the majority of this wood has been almost completely agatized, obliterating the cellular structures used to make taxonomic assignments. Furthermore, Savidge (2007) found that there are actually several wood taxa at this horizon, in fact almost every specimen sampled turns out to be new. Thus, park staff are at a loss when asked what the name the main type of fossil wood in the park is, and most just simply still continue to use the invalid name Araucarioxylon.
Philippe, in this new paper, suggests that a better name for the morphogenus is Agathoxylon. However, I would be hesitant to refer the large amounts of currently unnamed wood to this genus as he also suggests that eventually it should be restricted to a single species. Furthermore, because of the restriction of the type of P. arizonicum, the majority of Chinle wood lacks a direct assignment to a species-group name. This is a mess that probably will never be resolved because of the poor preservation of the wood structures, thus the majority of Chinle wood will simply be referrable to Araucariaceae indeterminate (or maybe even a more inclusive clade or rank?).
Philippe, M., in press. How many species of Araucarioxylon? C. R. Palevol (2011), doi:10.1016/j.crpv.2010.10.010
Abstract - Fossil wood, similar to that of modern Araucariaceae, has been known for a long time, and is usually called Araucarioxylon. More than 400 morphospecies have been described, whereas this wood type displays few characteristic features. This taxonomical profusion is compounded by nomenclatural problems, Araucarioxylon being an illegitimate name. The status of the wood morphogenus, the infrageneric structure and the names that apply to the taxa designated for fossil woods of the Araucarioxylon-type are discussed. A database with 428 morphospecies designated for Araucarioxylon-type of wood is analyzed. The name Agathoxylon Hartig seems to be the most appropriate for the corresponding morphogenus. Albeit theoretically several hundred morphospecies could be recognized within this group, it is at least as probable that only one should be retained.
REFERENCES
Savidge, R.A. 2006. Xylotomic evidence for two new conifers and a ginkgo within the Late Triassic Chinle Formation of Petrified Forest National Park, Arizona, USA, 147–149. In Parker, W.G., Ash, S.R. & Irmis, R.B. (eds) A century of research at Petrified Forest National Park: geology and paleontology. Museum of Northern Arizona Bulletin 62.
Savidge, R. A. 2007. Wood anatomy of Late Triassic trees in Petrified Forest National Park, Arizona, USA, in relation to Araucarioxylon arizonicum Knowlton, 1889. Bulletin of Geosciences 82:301–328.
Savidge, R.A. & Ash, S.R. 2006. Arboramosa semicircumtrachea, an unusual Late Triassic tree in Petrified Forest National Park, Arizona, USA, 65–81. In Parker, W.G., Ash, S.R. & Irmis, R.B. (eds) A century of research at Petrified Forest National Park: geology and paleontology. Museum of Northern Arizona Bulletin 62.
Pravusuchus hortus the Wicked Phytosaur from the Petrified Forest
Stocker, M. R. 2010. A new taxon of phytosaur (Archosauria: Pseudosuchia) from the Late Triassic (Norian) Sonsela Member (Chinle Formation) in Arizona, and a critical re-evaluation of Leptosuchus Case 1922. Palaeontology 53:997-1022. doi: 10.1111/j.1475-4983.2010.00983.x
Abstract - Leptosuchus Case, 1922 (Reptilia: Phytosauria) from the Late Triassic of the American West is represented by many specimens. Here, I present complete morphological descriptions of the skull material of a new taxon from the Sonsela Member (Chinle Formation) of Petrified Forest National Park, Arizona, with the first rigorous phylogenetic analysis focused on the interrelationships of Leptosuchus. The new taxon is recovered as the sister taxon to Pseudopalatinae. It possesses one unambiguous synapomorphy (the ‘septomaxillae’ form part of the lateral borders of the nares) and shares the presence of a subsidiary opisthotic process with Pseudopalatinae. The new taxon does not fall within the restricted clade Leptosuchus. In my analysis, the previously proposed, but undemonstrated, sister taxon relationship between Angistorhinus and Rutiodon is not supported, Paleorhinus is recovered as paraphyletic, and a subset of taxa traditionally included within Leptosuchus are found to be more closely related to Pseudopalatinae, rendering Leptosuchus paraphyletic. ‘Leptosuchus’ adamanensis emerges as sister taxon to Smilosuchus gregorii and is here referred to as Smilosuchus adamanensis nov. comb., and ‘Machaeroprosopus’ lithodendrorum is also transferred to Smilosuchus lithodendrorum nov. comb. Documentation of the variation present within Phytosauria, and specifically within Leptosuchus sensu lato, demonstrates higher diversity within Phytosauria than previously appreciated and places the character states previously proposed for Pseudopalatinae into a broader context of shared characters.
One specific subject that even the heartiest of Triassic workers will often go out of their way to avoid is the issue of phytosaur taxonomy, and for good reason, it is a mess. I previously supplied a flowchart I created in 2001 that demonstrates how much of a mess I’m talking about. Recent revisions (e.g., Hungerbühler 2002) have dealt almost exclusively with the pseudopalatine phytosaurs and the rest of the group has been relatively neglected since Long and Murry’s (1995) treatment. The genus Leptosuchus (still assigned to Rutiodon by some) has been poorly understood, and most new specimens assigned to this genus have been lumped into existing species without clear discussion of the characters used to support these assignments (I’m am guilty of this myself).
In the Spring of 2003 Daniel Woody and I discovered a large phytosaur skull in the Devil’s Playground portion of Petrified Forest National Park during a geological reconnaissance. That summer a crew consisting of Randall Irmis, Michelle Stocker, Jeff Shuman, and I collected the skull (now PEFO 31218) and our group initiated preparation. A couple of months later Jeff, Randy, and I discovered a second skull very close by; however, this skull appeared to only consist of a set of badly eroded lower jaws and was not collected. Interestingly we made the discovery while we were relocating and rephotographing a photo taken by Edwin Colbert of a phytosaur skull excavation conducted by the AMNH in 1946. Amazingly both skull sites are in this historic photo.
In 2006 Michelle and I reinvestigated the lower jaws and discovered that much of the skull was indeed present. This skull (PEFO 34239) was collected and Michelle began the preparation. About this time Michelle was looking for a good project for her Master’s thesis at the University of Iowa and despite knowing the potential pitfalls in the morass of phytosaur taxonomy, I suggested that maybe she should describe the two PEFO skulls (she had helped excavate and prep both of them) and determine their taxonomic affinities. Fast forwarding to the present it would seem that this was indeed a very good project and Michelle produced a very fine thesis (Stocker 2008), a portion of which is presented in this paper. She has since become quite the expert in the phytosaurs of the American Southwest and I look forward to more of her work on this subject (it is badly needed).
Some important points from this paper and details on the specimens:
1) Erects a new phytosaur taxon, Pravusuchus hortus, from the Sonsela Member of the Chinle Formation of Petrified Forest National Park. Existing specimens of Pravusuchus were originally assigned to the genus Leptosuchus, but detailed analysis shows that the taxon is distinct, possessing skull characters found in both ‘leptosuchines’ and pseudopalatines.
2) The holotype (AMNH FR 30646) was originally collected from the Petrified Forest in 1946 by Edwin Colbert of the American Museum of Natural History. The referred specimens are from the same geographical area and stratigraphic horizon and were collected by park staff (including Michelle Stocker) in 2003 and 2006.
3) Stratigraphically the specimens were found between the highest specimens of “Leptosuchus” and the lowest specimens of Pseudopalatus (Parker and Martz in press).
4) The genus Leptosuchus (sensu Long and Murry 1995) is paraphyletic and specimens referred to the genus are now only found in the Dockum Group. Arizona specimens of “Leptosuchus” are reassigned to Pravusuchus and Smilosuchus.
5) Stocker considers there to be three valid species of Smilosuchus; S. gregorii (the type species), S. adamanensis, and S. lithodendrorum. These last two are new combinations and this study resurrects the species S. lithodendrorum, which was considered a junior sysnonym of Leptosuchus crosbiensis by Long and Murry (1995).
This paper contains the most inclusive phylogenetic analysis of the Phytosauria since Ballew (1989). Some results:
1) The genus Paleorhinus is paraphyletic. Although this idea has been floating around for awhile (e.g., Fara and Hungerbuehler 2000) this is the first time it has been supported with a phylogenetic analysis.
2) The genera Anghistorhinus and Rutiodon are distinct. This synonymy was first put forth in an abstract by Hungerbuehler and Sues in 2001, but is not recovered in this study.
3) The name Rutiodon is restricted to specimens from the eastern United States. The name Rutiodon is often used for phytosaur specimens from the western United States stemming back to work by Gregory (1962) and Ballew (1989); however, this paper clearly shows that these referrals are erroneous and Rutiodon should be restricted to material from the eastern U.S.
This analysis should form the basis of future studies on the lower part of the phytosaur tree for a long time to come.
REFERENCES
Ballew, K. L. 1989. A phylogenetic analysis of Phytosauria from the Late Triassic of the western United States. 309–339. In LUCAS, S. G. and HUNT, A. P. (eds). Dawn of the age of dinosaurs in the American Southwest. New Mexico Museum of Natural History, Albuquerque, 414 pp.
Fara, E., and Hungerbühler, A. 2000. Paleorhinus magnoculus from the Upper Triassic of Morocco: a juvenile primitive phytosaur (Archosauria). Comptes Rendus de l’Académie des Sciences, Paris, Sciences de la Terre et des planétes, 331, 831–836.
Gregory, J. T. 1962. The genera of the phytosaurs. American Journal of Science, 260, 652–690.
Hungerbühler, A. 2002. The Late Triassic phytosaur Mystriosuchus westphali, with a revision of the genus. Palaeontology, 45, 377–418.
Hungerbühler, A., and Sues, H.-D. 2001. Status and phylogenetic relationships of the Late Triassic phytosaur Rutiodon carolinensis. Journal of Vertebrate Paleontology, 21(3-Suppl.), 64A.
Long, R. A. and Murry, P. A. 1995. Late Triassic (Carnian and Norian) tetrapods from the southwestern United States. Bulletin of the New Mexico Museum of Natural History and Science, 4, 1–254.
Stocker, M. R. 2008. Relationships of the phytosaur Leptosuchus Case 1922 with descriptions of new material from Petrified Forest National Park, Arizona. Unpublished MS thesis, University of Iowa, Iowa City, 220 pp.
Abstract - Leptosuchus Case, 1922 (Reptilia: Phytosauria) from the Late Triassic of the American West is represented by many specimens. Here, I present complete morphological descriptions of the skull material of a new taxon from the Sonsela Member (Chinle Formation) of Petrified Forest National Park, Arizona, with the first rigorous phylogenetic analysis focused on the interrelationships of Leptosuchus. The new taxon is recovered as the sister taxon to Pseudopalatinae. It possesses one unambiguous synapomorphy (the ‘septomaxillae’ form part of the lateral borders of the nares) and shares the presence of a subsidiary opisthotic process with Pseudopalatinae. The new taxon does not fall within the restricted clade Leptosuchus. In my analysis, the previously proposed, but undemonstrated, sister taxon relationship between Angistorhinus and Rutiodon is not supported, Paleorhinus is recovered as paraphyletic, and a subset of taxa traditionally included within Leptosuchus are found to be more closely related to Pseudopalatinae, rendering Leptosuchus paraphyletic. ‘Leptosuchus’ adamanensis emerges as sister taxon to Smilosuchus gregorii and is here referred to as Smilosuchus adamanensis nov. comb., and ‘Machaeroprosopus’ lithodendrorum is also transferred to Smilosuchus lithodendrorum nov. comb. Documentation of the variation present within Phytosauria, and specifically within Leptosuchus sensu lato, demonstrates higher diversity within Phytosauria than previously appreciated and places the character states previously proposed for Pseudopalatinae into a broader context of shared characters.
One specific subject that even the heartiest of Triassic workers will often go out of their way to avoid is the issue of phytosaur taxonomy, and for good reason, it is a mess. I previously supplied a flowchart I created in 2001 that demonstrates how much of a mess I’m talking about. Recent revisions (e.g., Hungerbühler 2002) have dealt almost exclusively with the pseudopalatine phytosaurs and the rest of the group has been relatively neglected since Long and Murry’s (1995) treatment. The genus Leptosuchus (still assigned to Rutiodon by some) has been poorly understood, and most new specimens assigned to this genus have been lumped into existing species without clear discussion of the characters used to support these assignments (I’m am guilty of this myself).
In the Spring of 2003 Daniel Woody and I discovered a large phytosaur skull in the Devil’s Playground portion of Petrified Forest National Park during a geological reconnaissance. That summer a crew consisting of Randall Irmis, Michelle Stocker, Jeff Shuman, and I collected the skull (now PEFO 31218) and our group initiated preparation. A couple of months later Jeff, Randy, and I discovered a second skull very close by; however, this skull appeared to only consist of a set of badly eroded lower jaws and was not collected. Interestingly we made the discovery while we were relocating and rephotographing a photo taken by Edwin Colbert of a phytosaur skull excavation conducted by the AMNH in 1946. Amazingly both skull sites are in this historic photo.
In 2006 Michelle and I reinvestigated the lower jaws and discovered that much of the skull was indeed present. This skull (PEFO 34239) was collected and Michelle began the preparation. About this time Michelle was looking for a good project for her Master’s thesis at the University of Iowa and despite knowing the potential pitfalls in the morass of phytosaur taxonomy, I suggested that maybe she should describe the two PEFO skulls (she had helped excavate and prep both of them) and determine their taxonomic affinities. Fast forwarding to the present it would seem that this was indeed a very good project and Michelle produced a very fine thesis (Stocker 2008), a portion of which is presented in this paper. She has since become quite the expert in the phytosaurs of the American Southwest and I look forward to more of her work on this subject (it is badly needed).
Some important points from this paper and details on the specimens:
1) Erects a new phytosaur taxon, Pravusuchus hortus, from the Sonsela Member of the Chinle Formation of Petrified Forest National Park. Existing specimens of Pravusuchus were originally assigned to the genus Leptosuchus, but detailed analysis shows that the taxon is distinct, possessing skull characters found in both ‘leptosuchines’ and pseudopalatines.
2) The holotype (AMNH FR 30646) was originally collected from the Petrified Forest in 1946 by Edwin Colbert of the American Museum of Natural History. The referred specimens are from the same geographical area and stratigraphic horizon and were collected by park staff (including Michelle Stocker) in 2003 and 2006.
3) Stratigraphically the specimens were found between the highest specimens of “Leptosuchus” and the lowest specimens of Pseudopalatus (Parker and Martz in press).
4) The genus Leptosuchus (sensu Long and Murry 1995) is paraphyletic and specimens referred to the genus are now only found in the Dockum Group. Arizona specimens of “Leptosuchus” are reassigned to Pravusuchus and Smilosuchus.
5) Stocker considers there to be three valid species of Smilosuchus; S. gregorii (the type species), S. adamanensis, and S. lithodendrorum. These last two are new combinations and this study resurrects the species S. lithodendrorum, which was considered a junior sysnonym of Leptosuchus crosbiensis by Long and Murry (1995).
This paper contains the most inclusive phylogenetic analysis of the Phytosauria since Ballew (1989). Some results:
1) The genus Paleorhinus is paraphyletic. Although this idea has been floating around for awhile (e.g., Fara and Hungerbuehler 2000) this is the first time it has been supported with a phylogenetic analysis.
2) The genera Anghistorhinus and Rutiodon are distinct. This synonymy was first put forth in an abstract by Hungerbuehler and Sues in 2001, but is not recovered in this study.
3) The name Rutiodon is restricted to specimens from the eastern United States. The name Rutiodon is often used for phytosaur specimens from the western United States stemming back to work by Gregory (1962) and Ballew (1989); however, this paper clearly shows that these referrals are erroneous and Rutiodon should be restricted to material from the eastern U.S.
This analysis should form the basis of future studies on the lower part of the phytosaur tree for a long time to come.
REFERENCES
Ballew, K. L. 1989. A phylogenetic analysis of Phytosauria from the Late Triassic of the western United States. 309–339. In LUCAS, S. G. and HUNT, A. P. (eds). Dawn of the age of dinosaurs in the American Southwest. New Mexico Museum of Natural History, Albuquerque, 414 pp.
Fara, E., and Hungerbühler, A. 2000. Paleorhinus magnoculus from the Upper Triassic of Morocco: a juvenile primitive phytosaur (Archosauria). Comptes Rendus de l’Académie des Sciences, Paris, Sciences de la Terre et des planétes, 331, 831–836.
Gregory, J. T. 1962. The genera of the phytosaurs. American Journal of Science, 260, 652–690.
Hungerbühler, A. 2002. The Late Triassic phytosaur Mystriosuchus westphali, with a revision of the genus. Palaeontology, 45, 377–418.
Hungerbühler, A., and Sues, H.-D. 2001. Status and phylogenetic relationships of the Late Triassic phytosaur Rutiodon carolinensis. Journal of Vertebrate Paleontology, 21(3-Suppl.), 64A.
Long, R. A. and Murry, P. A. 1995. Late Triassic (Carnian and Norian) tetrapods from the southwestern United States. Bulletin of the New Mexico Museum of Natural History and Science, 4, 1–254.
Stocker, M. R. 2008. Relationships of the phytosaur Leptosuchus Case 1922 with descriptions of new material from Petrified Forest National Park, Arizona. Unpublished MS thesis, University of Iowa, Iowa City, 220 pp.
Petrified Forest National Park Landmarks - Herbert Gregory's "Stump"
The USGS Geologist Herbert E. Gregory formally named and described the Chinle Formation in detail in a 1917 publication titled "Geology of the Navojo Country". Plate X, figure B of this publication is a photo of a "petrified tree" from Lithodendron Wash, an area which in 1931 would become part of the then Petrified Forest National Monument. Although later determined by park naturalists not to represent a true standing tree, it was deposited in this position after some transport distance, this specimen looks exactly the same today. It is in the Black Forest Bed, a prominent tuffaceous sandstone in the Petrified Forest Member of the Chinle Formation and located in a large accumulation of logs called the Black Forest in the Painted Desert portion of the park. Below is a scan Gregory's published photo as well as a photo of the same specimen taken in 2010. It is fortunate that Gregory recorded much of his work and travels with photographs. They provide an excellent account of the geology and people of the Colorado Plateau in the early 20th century.
REFERENCE
Gregory, H. E. 1917. Geology of Navajo Country. United States Geological Survey Professional Paper 93, p. 161.
 |
| (From Gregory 1917) |
REFERENCE
Gregory, H. E. 1917. Geology of Navajo Country. United States Geological Survey Professional Paper 93, p. 161.
First Record of Hybodont Shark Egg Cases From the Chinle Formation
Lots of new Triassic papers out now...here is one documenting the first unambigous hybodont shark egg capsules from the Chinle Formation and the Triassic of North America! These are from the leaf shale facies of the Newspaper Rock Bed, a significant plant bearing horizon in the Blue Mesa Member of Petrified Forest National Park.
Fischer, J., Axsmith, B. J. and S. R. Ash. 2010. First unequivocal record of the hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America. Neues Jahrbuch fur Geologie und Paläontologie Abh. 255: 327–344.
Abstract - The hybodont shark egg capsule Palaeoxyris humblei n. sp. is described here from four specimens collected from flood plain deposits in the Blue Mesa Member of the Chinle Formation of Late Triassic (Norian) age in Petrified Forest National Park, Arizona. This find is the first unequivocal record of Palaeoxyris in the Mesozoic of North America. The species differs from previously known taxa, especially other Triassic forms in size and banding. It also is one of the smallest species assigned to the genus. This find offers the rare opportunity of plausibly assigning these egg capsules to the hybodont nonmarine shark Lonchidion humblei as the most probable source since its disarticulated remains (teeth, fin spines) have been found at a closely adjacent locality. Originally, these eggs were deposited in special spawning grounds in the river that deposited the Newspaper Sandstone Bed. There they became attached by tendrils to a piece of drift wood or perhaps the stem or branches of a horsetail such as Neocalamites or Equisetites that grew in the shallow waters of the stream. However, the stream overflowed its banks and the egg capsules together with masses of plant debris and various invertebrates were washed onto the adjacent floodplain where they were buried and eventually fossilized.
Fischer, J., Axsmith, B. J. and S. R. Ash. 2010. First unequivocal record of the hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America. Neues Jahrbuch fur Geologie und Paläontologie Abh. 255: 327–344.
Abstract - The hybodont shark egg capsule Palaeoxyris humblei n. sp. is described here from four specimens collected from flood plain deposits in the Blue Mesa Member of the Chinle Formation of Late Triassic (Norian) age in Petrified Forest National Park, Arizona. This find is the first unequivocal record of Palaeoxyris in the Mesozoic of North America. The species differs from previously known taxa, especially other Triassic forms in size and banding. It also is one of the smallest species assigned to the genus. This find offers the rare opportunity of plausibly assigning these egg capsules to the hybodont nonmarine shark Lonchidion humblei as the most probable source since its disarticulated remains (teeth, fin spines) have been found at a closely adjacent locality. Originally, these eggs were deposited in special spawning grounds in the river that deposited the Newspaper Sandstone Bed. There they became attached by tendrils to a piece of drift wood or perhaps the stem or branches of a horsetail such as Neocalamites or Equisetites that grew in the shallow waters of the stream. However, the stream overflowed its banks and the egg capsules together with masses of plant debris and various invertebrates were washed onto the adjacent floodplain where they were buried and eventually fossilized.
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.
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.
Petrified Forest Landmarks - Eagle Nest Rock
For the first 35 years of its existence as a National Monument, one of the major attractions of the Petrified Forest was Eagle Nest Rock in Jasper Forest. As seen below in an undated National Park Service photo. Eagle Nest Rock was a erosional pillar of sandstone in the Jasper Forest bed of the Sonsela Member (Chinle Formation).
The photo [NPS] below is a closer view, showing how remarkable (and delicate) this feature was. It stood about 15 feet (5 meters) tall.
A gravel road detoured off of the main park road and wound its way through the Jasper Forest (numerous petrified logs) turned to the southwest and at its terminus curved around Eagle Nest Rock.
This was a very popular attraction and visitors (and park rangers) would climb up and have their photo taken next to the pillar. The photo [courtesy of the UCMP]. below was taken of Clyde Polacca (of the Hopi Reservation) in 1923 by Charles L. Camp during his paleontological research of the Petrified Forest area
Sadly Eagle Nest Rock "landmark in the First Forest, fell January 25 and 26 [1941] following a month of considerable rain and some high winds.” - Howard R. Stagner, monthly naturalist report.
The old Jasper Forest road was closed afterwards to protect fossil resources (petrified wood) and now only an overlook exists from which you cannot see the Eagle Nest Rock site. The old road was never removed and you can still follow it today. Below is a reshoot of Camp's photo from 2006.
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