Lots of Chinle Formation coverage in this new paper as there are fossiliferous exposures of that unit in many of the National Parks in southern Utah, including Dinosaur National Monument.
Santucci, V. L., and J. I. Kirkland. 2010. An Overview of National Park Service Paleontological Resources from the Parks and Monuments in Utah; pp. 589-623 in D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson (eds.), Geology of Utah’s Parks and Monuments 2010, Utah Geological Association Publication 28.
Abstract - The National Park Service (NPS) administers thirteen park units within the state of Utah. Most of these parks, monuments, and other NPS units have been established and are recognized for their significant geologic features. Fossiliferous
rocks of Paleozoic, Mesozoic, and Cenozoic age have been identified in all of the National Park System units in Utah. In 1998, the first comprehensive inventory of paleontological resources in the national parks and monuments of Utah was initiated. A wide diversity of fossilized plants, invertebrates, vertebrates, and trace fossils has been documented. Paleontological resources identified from within the parks and monuments have been assessed relative to their scientific significance, potential threats, and management as non-renewable resources. Considerable focus has been directed towards the in situ management of the abundant fossil vertebrate tracks identified throughout the Mesozoic formations within at least seven NPS areas in Utah. The baseline paleontological resource data obtained during this inventory will assist park staff with improved management of their paleontological resources and protection of fossils within their park.
Enhanced Technique for Separating Microvertebrates from Matrix
The Journal of Paleontological Techniques is an online, open access journal dedicate to publishing papers on fossil preparation. The latest offering is this paper by Mitchell and Heckert describing the use of sodium polytungstate filtration to separate some Upper Triassic microfossils from collected matrix. Although there are some serious caveats to using these chemicals (such as how the chemicals react with metal and glass...ouch), the results are promising and the set-up looks fairly easy. You can download this article free from here.
Mitchell, J. S. and A. B. Heckert. 2010. The setup, use and efficacy of sodium polytungstate separation methodology with respect to microvertebrate remains. Journal of Paleontological Techniques, 7: 1-12.
Abstract - Concentrated deposits of small remains from vertebrates, termed microvertebrate sites or vertebrate microsites, are a unique and detailed source of information about the history of life. Collecting fossils from these sites, however, presents unique challenges. The most time consuming, and thus most deterring, aspect by far is the separation of the fossils from the sediment. This study attempts to quantify to what extent the use of sodium polytungstate (=sodium metatungstate, Na6H2W12O40, abbr. SPT) filtration increases fossil concentration, how quickly fossils sink in SPT solutions, and what is a good working density for SPT. We do this by generally following the methodology set out by previous authors, although with some substantial modifications, on an Upper Triassic deposit dominated by clay minerals and lithic fragments, as well as on a second, smaller quartz sand dominated microsite. We also provide a revised and detailed guide with our modifications to former practices and our recommendations to other workers interested in creating a SPT laboratory, including the strong advisory to work over thin plastic sheets, as SPT can react with metal and adheres strongly to glass when it crystallizes.
Our experiments have shown a significant improvement in fossil concentration (from ~2% of the clasts being fossils to ~19%) at the main site, with a sample from the other site showing the treated concentrate as 25% fossil. We have also found very few fossils in the float (<0.5%), but noticeable rates of fossil loss in SPT solutions above ~2.80 g/mL (up to 16%). Further, we have found that 2.75 g/mL is a good working density for several lithologies, as it is high enough to float most rock, low enough to sink most fossils, and low enough to be manageably maintained. SPT has, in processing one particularly rich site, saved many person-hours that otherwise would have been spent picking through less concentrated sediment.
Mitchell, J. S. and A. B. Heckert. 2010. The setup, use and efficacy of sodium polytungstate separation methodology with respect to microvertebrate remains. Journal of Paleontological Techniques, 7: 1-12.
Abstract - Concentrated deposits of small remains from vertebrates, termed microvertebrate sites or vertebrate microsites, are a unique and detailed source of information about the history of life. Collecting fossils from these sites, however, presents unique challenges. The most time consuming, and thus most deterring, aspect by far is the separation of the fossils from the sediment. This study attempts to quantify to what extent the use of sodium polytungstate (=sodium metatungstate, Na6H2W12O40, abbr. SPT) filtration increases fossil concentration, how quickly fossils sink in SPT solutions, and what is a good working density for SPT. We do this by generally following the methodology set out by previous authors, although with some substantial modifications, on an Upper Triassic deposit dominated by clay minerals and lithic fragments, as well as on a second, smaller quartz sand dominated microsite. We also provide a revised and detailed guide with our modifications to former practices and our recommendations to other workers interested in creating a SPT laboratory, including the strong advisory to work over thin plastic sheets, as SPT can react with metal and adheres strongly to glass when it crystallizes.
Our experiments have shown a significant improvement in fossil concentration (from ~2% of the clasts being fossils to ~19%) at the main site, with a sample from the other site showing the treated concentrate as 25% fossil. We have also found very few fossils in the float (<0.5%), but noticeable rates of fossil loss in SPT solutions above ~2.80 g/mL (up to 16%). Further, we have found that 2.75 g/mL is a good working density for several lithologies, as it is high enough to float most rock, low enough to sink most fossils, and low enough to be manageably maintained. SPT has, in processing one particularly rich site, saved many person-hours that otherwise would have been spent picking through less concentrated sediment.
Jeff Martz Speaks Out on Publishing as a Paleontologist - the Professional vs. Non-Professional Debate
Over at the Paleo Errata blog Jeff Martz has an excellent discussion on what it means to make scientific contributions to the field of paleontology regardless of the possession of degrees, chosen scientific major, or even if you get paid to do paleontology full-time. As he states pretty clearly, science and scientific publication can be done by anyone who has questions and takes the time to reason out these ideas, support them with carefully collected data, and most importantly realize that the test of their ideas often involves intense scrutiny that can sometimes be uncomfortable. I have also touched upon this recently, but not as clearly as Jeff has. Science is not necessarily about degrees or jobs, it is about presenting the best thought out and supported work that you can to add to current attempt to figure things out. As Jeff states, "In the process of doing this work and fostering an intellectually honest attitude about themselves and what the produce, they earn the respect of the scientific community. These people are SCIENTISTS…regardless of whether they have degrees or not."
Jeff also throws my name out there in a list of persons he considers to do good scientific work (I do try) without have obtaining specific degrees. It is true that my highest attained degree is a Masters of Science, and I just only recently entered into a PhD program (this past Spring at the University of Texas in Austin). Despite this, between 2003 and the present I have published more than 25 peer reviewed papers, edited or co-edited four volumes, organized 3 scientific symposia, have provided my services as a reviewer for many manuscripts, and developed a successful research program at a major paleontological national park. I am proud of these accomplishments and have often tried to use my example to encourage others that one doesn't need an advanced degree to contribute to science (which I hope that I have), you just have to work hard and be willing to face criticism of your ideas. This criticism will actually strengthen your work if you allow.
Likewise, during my time at the Petrified Forest I have been fortunate to have hired personnel whom I would consider to be some of the best fossil preparators in the field. I have never made the possession of a degree a requirement for these positions as I am only concerned in their technical and intellectual abilities, things that do not necessarily require degrees. I've spoken out in the past how it has always amazed me that fossil preparator positions often come with a Geology degree requirement as in my opinion this requirement automatically disqualifies many of the best preparators in the business. Note that this is not meant to criticize or lessen preparators who have taken the time to get science degrees as hopefully the attainment of the degree provided them with much acquired expertise (this is what degree programs are designed to do); however, expertise can also be developed through hard work. In my eyes both paths are acceptable and I have yet to be let down by this approach.
Nonetheless, publishing is still not something to be taken lightly; however, as you need to first develop a strong foundation of the problem that you are interested in. This is done mainly through thorough reading of the literature and detailed first-hand examination of relevant specimens. Another fact I am proud of is that I did not produce my first publications on aetosaurs (the main group of fossils organisms I like to figure out) until around six years after I started really studying them. I've always encouraged my student interns to learn one thing really well to address problems within that discipline, and then branch out afterwards (I'm not sure if they listened ;)). This gives you expertise on a specific scientific subject, and can establish you in the community. There are actually quite a few "amateurs" on the various mailing lists who have always impressed me with the breadth and depth of their scientific knowledge on various subjects that appears to go way beyond a mild interest. I always wonder if these individuals will publish their ideas someday, especially as unfortunately some of their co-listers with only a seemingly mild interest have figured out various ways to put stuff out (and appear quite proud of this). I always wonder if these much more knowledgeable "amatuers" do not publish out of disinterest or because they have no been encouraged to do so by their peers.
Another major point that Jeff makes in his post is the idea that if someone who is considered to be an "amateur" (or even a degreed individual) publishes something in the non-peer-reviewed (or gray literature) then it is seen by some as acceptable to simply ignore that publication, presumably because it is unworthy of publication. I agree with Jeff that in a sense this is the "elitist" attitude that conflagrates the whole "professional vs. non-professional" discussion because it presupposes that an "amateur" cannot make a worthy scientific contribution. Instead, someone who decides to skip the steps of peer-review and self-publish should be prepared to face the intense scrutiny of their ideas that all scientists deal with, and if your self-published ideas are poorly supported, then be prepared for the heavy criticism. Like Jeff said, science doesn't care about your ego, just about the value of your ideas. However, everyones' ideas should be held up to the same scrutiny whether they have a PhD and have published dozens of papers or if they have no degree and this is their first offering. In a nutshell, science is a process of continuous building and it shouldn't matter who is doing the construction as long as the materials are sound. Come and join us.
Post-script: Why am I getting a PhD then if the degree is not necessary to do science? Simple, as I stated earlier the purpose of a degree program is to provide opportunities to acquire expertise from peers (we call them professors in the university setting). Networking is one of the most powerful tools available to us a scientists and the university setting allows for one to be submersed in a think tank constantly around people (students and teachers) with influential great ideas. Collaboration and consultation are remarkable learning tools that can take you very far in your career. Paleontology is a science that is not done well on an "island". We constantly need the input (including criticism) of our peers to see through the loopholes in our thinking and strengthen our ideas and their presentation. I felt that I had reached an intellectual "wall" in my career and returning to the university and exposing myself to a whole new cadre of peers was intellectually stimulating. I hope to continue.
Jeff also throws my name out there in a list of persons he considers to do good scientific work (I do try) without have obtaining specific degrees. It is true that my highest attained degree is a Masters of Science, and I just only recently entered into a PhD program (this past Spring at the University of Texas in Austin). Despite this, between 2003 and the present I have published more than 25 peer reviewed papers, edited or co-edited four volumes, organized 3 scientific symposia, have provided my services as a reviewer for many manuscripts, and developed a successful research program at a major paleontological national park. I am proud of these accomplishments and have often tried to use my example to encourage others that one doesn't need an advanced degree to contribute to science (which I hope that I have), you just have to work hard and be willing to face criticism of your ideas. This criticism will actually strengthen your work if you allow.
Likewise, during my time at the Petrified Forest I have been fortunate to have hired personnel whom I would consider to be some of the best fossil preparators in the field. I have never made the possession of a degree a requirement for these positions as I am only concerned in their technical and intellectual abilities, things that do not necessarily require degrees. I've spoken out in the past how it has always amazed me that fossil preparator positions often come with a Geology degree requirement as in my opinion this requirement automatically disqualifies many of the best preparators in the business. Note that this is not meant to criticize or lessen preparators who have taken the time to get science degrees as hopefully the attainment of the degree provided them with much acquired expertise (this is what degree programs are designed to do); however, expertise can also be developed through hard work. In my eyes both paths are acceptable and I have yet to be let down by this approach.
Nonetheless, publishing is still not something to be taken lightly; however, as you need to first develop a strong foundation of the problem that you are interested in. This is done mainly through thorough reading of the literature and detailed first-hand examination of relevant specimens. Another fact I am proud of is that I did not produce my first publications on aetosaurs (the main group of fossils organisms I like to figure out) until around six years after I started really studying them. I've always encouraged my student interns to learn one thing really well to address problems within that discipline, and then branch out afterwards (I'm not sure if they listened ;)). This gives you expertise on a specific scientific subject, and can establish you in the community. There are actually quite a few "amateurs" on the various mailing lists who have always impressed me with the breadth and depth of their scientific knowledge on various subjects that appears to go way beyond a mild interest. I always wonder if these individuals will publish their ideas someday, especially as unfortunately some of their co-listers with only a seemingly mild interest have figured out various ways to put stuff out (and appear quite proud of this). I always wonder if these much more knowledgeable "amatuers" do not publish out of disinterest or because they have no been encouraged to do so by their peers.
Another major point that Jeff makes in his post is the idea that if someone who is considered to be an "amateur" (or even a degreed individual) publishes something in the non-peer-reviewed (or gray literature) then it is seen by some as acceptable to simply ignore that publication, presumably because it is unworthy of publication. I agree with Jeff that in a sense this is the "elitist" attitude that conflagrates the whole "professional vs. non-professional" discussion because it presupposes that an "amateur" cannot make a worthy scientific contribution. Instead, someone who decides to skip the steps of peer-review and self-publish should be prepared to face the intense scrutiny of their ideas that all scientists deal with, and if your self-published ideas are poorly supported, then be prepared for the heavy criticism. Like Jeff said, science doesn't care about your ego, just about the value of your ideas. However, everyones' ideas should be held up to the same scrutiny whether they have a PhD and have published dozens of papers or if they have no degree and this is their first offering. In a nutshell, science is a process of continuous building and it shouldn't matter who is doing the construction as long as the materials are sound. Come and join us.
Post-script: Why am I getting a PhD then if the degree is not necessary to do science? Simple, as I stated earlier the purpose of a degree program is to provide opportunities to acquire expertise from peers (we call them professors in the university setting). Networking is one of the most powerful tools available to us a scientists and the university setting allows for one to be submersed in a think tank constantly around people (students and teachers) with influential great ideas. Collaboration and consultation are remarkable learning tools that can take you very far in your career. Paleontology is a science that is not done well on an "island". We constantly need the input (including criticism) of our peers to see through the loopholes in our thinking and strengthen our ideas and their presentation. I felt that I had reached an intellectual "wall" in my career and returning to the university and exposing myself to a whole new cadre of peers was intellectually stimulating. I hope to continue.
Phytosaur Skull Preparation IV
My Thoughts on the Peer Review Process (Part 3) - Wait Until the Peer-reviewed Paper (a case study from the ongoing debate surrounding reports of Triassic nests from Arizona).
When I was working on my MS thesis at Northern Arizona University on aetosaurs, I was struck by the announced discovery of fossil "reptile nests" (Hasiotis and Martin, 1999) and the earliest records of many social insect nests including bees (e.g., Hasiotis et al., 1998). It seemed possible that aetosaurs could have been the nest maker, and evidence from the site had also suggested some degree of parental care from whomever the nest maker was. Likewise, I had been tossing around the idea of possible alternative food sources for aetosaurs and insects might just fit the bill, especially if there was evidence for social insect nests during the Late Triassic. This early bee record also suggested that bees evolved before and separately from angiosperms.
When I started working at the park one of the first sites my supervisor took me to was the site of these "reptile nests" as she was curious what another geologist/paleontologist would think of them. Needless to say I was extremely disappointed. Every geologist I have showed them to since agrees with my assessment, they are simply erosional potholes in a sandstone. Visiting the site provides the detailed evidence for this determination. Unfortunately this discovery resulted in much popular press and these "nests" even make into more recent research papers; however, no detailed rebuttal has yet been published. Other nests attributed to aetosaurs have been described from the Triassic of Italy (Avanzini et al., 2007), but I have not been able to see these first hand to evaluate them.
[Note: I had forgotten about the rebuttal on the Petrified Forest 'nests' by Lucas and Hunt (2006)].
The bee's nest record, from a log in the Petrified Forest, was immediately criticized by entomologists (e.g., Grimaldi, 1999; Engel, 2001), arguing that these traces provide no signature evidence of bee activity. Unlike the "reptile nests"; however, these must have been made by some type of organism, and beetles have been the most cited tracemaker. Also unlike the 'reptile nests' there is a detailed rebuttal paper that provides good evidence that these traces are not bee's nests, but rather represent a new form of beetle trace (Lucas et al., 2010 - see abstract below). Like the 'reptile nests' every person with an entomological background that I have shown these to agrees with this assessment and like the 'reptile nests' these story too received much popular press before a paper was published.
The lesson here is that we should avoid oversensationalizing 'amazing' discoveries like these until peer reviewed papers describing them in detail are published in the relevant literature. Failing to do so can cause long term misunderstandings regarding our fossil resources. This also happened in the case of Chindesaurus bryansmalli ("Gertie") which was hailed as the world's "earliest" dinosaur, a claim which still makes it in to occasional brochures and webpages about Petrified Forest National Park.
It can be very tempting to get excited about the finds and want to make a big media splash, but in the end they cannot be considered valid or relevant until they pass the critical test of peer review. As I argued in a previous post, having these papers reviewed by qualified entomologists and geological colleagues can help avoid having your work criticized and/or not accepted by future workers.
Having seen the specimens I believe that the Lucas et al's. interpretation has much merit; as do several other entomologists; however, it would appear that the debate is not entirely closed. I do especially have to agree with the last quote in this news story. I'd like to see more evidence for such a sensational claim.
Lucas, S. G., Minter, N. J., and A. P. Hunt. 2010. Re-evaluation of alleged bees' nests from the Upper Triassic of Arizona. Palaeogeography, Palaeoclimatology, Palaeoecology 286:194–201.
Abstract - Published records of supposed Triassic bees' nests are based on trace fossils in silicified wood and in sandstone in Upper Triassic strata of the Chinle Group in Petrified Forest National Park, Arizona. A critical, firsthand restudy of these trace fossils indicates that they lack diagnostic features of bees' nests, such as cells with smooth linings and spiral closure caps. Indeed, many of the observations claimed to identify these traces as bees' nests cannot be replicated. Instead, the putative Triassic bees' nests can be classified as: 1. Clavate borings in petrified wood, somewhat similar to Teredolites; these borings preferentially penetrate
heart-rot fungus (Polyporites) and are mostly likely larval chambers of wood-boring beetles. 2. Cylindrical,
vertical burrows in sandstone assignable to Skolithos; these are almost certainly arthropod produced. The
recognition that the Chinle Group trace fossils are not bees' nests eliminates them as evidence that decouples
bee origins from the Cretaceous origin of angiosperms. The Triassic trace fossils in silicified wood are also a
new and unique record of likely beetle borings in Triassic wood.
REFERENCES
Avanzini, M., Dalla Vecchia, F.M., Mietto, P., Piubelli, D., Preto, N., Rigo, M., and G. Roghi. 2007. A vertebrate nesting site in northeastern Italy reveals unexpectedly complex behavior for Late Carnian reptiles. Palaios 22:465-475.
Engel, M.S. 2001. A monograph of the Baltic amber bees and the evolution of the Apoidea (Hymenoptera). Bulletin of the American Museum of Natural History 259:1–192.
Grimaldi, D. 1999. The co-radiations of pollinating insects and angiosperms in the Cretaceous. Annals of the Missouri Botanical Garden 86, 373–406.
Hasiotis, S.T., and Martin, A., 1999, Probable reptile nests from the Upper Triassic Chinle Formation, Petrified Forest National Park, Arizona, in Santucci, V., and McClelland, L., eds., National Park Service, Paleontological Research, v. 4, p. 85–90.
Hasiotis, S.T., Dubiel, R.F., Kay, P.T., Demko, T.M., Kowalska, K., and D. McDaniel. 1998. Research update on hymenopteran nests and cocoons, Upper Triassic Chinle Formation, Petrified Forest National Park, Arizona. In: Santucci, V.L., McClelland, L. (Eds.), National Park Service Paleontological Research. Technical Report NPS/NRGRD/GRDTR-98/01, pp. 116–121.
Lucas, S.G., and Hunt, A.P. 2006. Reappraisal of 'reptile nests' from the Upper Triassic Chinle Group, Petrified Forest National Park, Arizona. New Mexico Museum of Natural History and Science Bulletin 37:155-159.
Lucas, S. G., Minter, N. J., and A. P. Hunt. 2010. Re-evaluation of alleged bees' nests from the Upper Triassic of Arizona. Palaeogeography, Palaeoclimatology, Palaeoecology 286:194–201.
 |
| Photograph of purported reptile nests from Petrified Forest National Park. From Hasiotis and Martin, 1999. |
[Note: I had forgotten about the rebuttal on the Petrified Forest 'nests' by Lucas and Hunt (2006)].
 |
| Purported "Bee's Nests" from Petrified Forest National Park. NPS photo. |
The lesson here is that we should avoid oversensationalizing 'amazing' discoveries like these until peer reviewed papers describing them in detail are published in the relevant literature. Failing to do so can cause long term misunderstandings regarding our fossil resources. This also happened in the case of Chindesaurus bryansmalli ("Gertie") which was hailed as the world's "earliest" dinosaur, a claim which still makes it in to occasional brochures and webpages about Petrified Forest National Park.
It can be very tempting to get excited about the finds and want to make a big media splash, but in the end they cannot be considered valid or relevant until they pass the critical test of peer review. As I argued in a previous post, having these papers reviewed by qualified entomologists and geological colleagues can help avoid having your work criticized and/or not accepted by future workers.
Having seen the specimens I believe that the Lucas et al's. interpretation has much merit; as do several other entomologists; however, it would appear that the debate is not entirely closed. I do especially have to agree with the last quote in this news story. I'd like to see more evidence for such a sensational claim.
Lucas, S. G., Minter, N. J., and A. P. Hunt. 2010. Re-evaluation of alleged bees' nests from the Upper Triassic of Arizona. Palaeogeography, Palaeoclimatology, Palaeoecology 286:194–201.
Abstract - Published records of supposed Triassic bees' nests are based on trace fossils in silicified wood and in sandstone in Upper Triassic strata of the Chinle Group in Petrified Forest National Park, Arizona. A critical, firsthand restudy of these trace fossils indicates that they lack diagnostic features of bees' nests, such as cells with smooth linings and spiral closure caps. Indeed, many of the observations claimed to identify these traces as bees' nests cannot be replicated. Instead, the putative Triassic bees' nests can be classified as: 1. Clavate borings in petrified wood, somewhat similar to Teredolites; these borings preferentially penetrate
heart-rot fungus (Polyporites) and are mostly likely larval chambers of wood-boring beetles. 2. Cylindrical,
vertical burrows in sandstone assignable to Skolithos; these are almost certainly arthropod produced. The
recognition that the Chinle Group trace fossils are not bees' nests eliminates them as evidence that decouples
bee origins from the Cretaceous origin of angiosperms. The Triassic trace fossils in silicified wood are also a
new and unique record of likely beetle borings in Triassic wood.
REFERENCES
Avanzini, M., Dalla Vecchia, F.M., Mietto, P., Piubelli, D., Preto, N., Rigo, M., and G. Roghi. 2007. A vertebrate nesting site in northeastern Italy reveals unexpectedly complex behavior for Late Carnian reptiles. Palaios 22:465-475.
Engel, M.S. 2001. A monograph of the Baltic amber bees and the evolution of the Apoidea (Hymenoptera). Bulletin of the American Museum of Natural History 259:1–192.
Grimaldi, D. 1999. The co-radiations of pollinating insects and angiosperms in the Cretaceous. Annals of the Missouri Botanical Garden 86, 373–406.
Hasiotis, S.T., and Martin, A., 1999, Probable reptile nests from the Upper Triassic Chinle Formation, Petrified Forest National Park, Arizona, in Santucci, V., and McClelland, L., eds., National Park Service, Paleontological Research, v. 4, p. 85–90.
Hasiotis, S.T., Dubiel, R.F., Kay, P.T., Demko, T.M., Kowalska, K., and D. McDaniel. 1998. Research update on hymenopteran nests and cocoons, Upper Triassic Chinle Formation, Petrified Forest National Park, Arizona. In: Santucci, V.L., McClelland, L. (Eds.), National Park Service Paleontological Research. Technical Report NPS/NRGRD/GRDTR-98/01, pp. 116–121.
Lucas, S.G., and Hunt, A.P. 2006. Reappraisal of 'reptile nests' from the Upper Triassic Chinle Group, Petrified Forest National Park, Arizona. New Mexico Museum of Natural History and Science Bulletin 37:155-159.
Lucas, S. G., Minter, N. J., and A. P. Hunt. 2010. Re-evaluation of alleged bees' nests from the Upper Triassic of Arizona. Palaeogeography, Palaeoclimatology, Palaeoecology 286:194–201.
More Chinle Formation Fieldwork in the Chama Basin
This is the Aqua Zarca Member of the Chinle Formation, which is the basalmost unit of the Chinle in the Chama Basin. This is a very colorful unit of interbedded sandstone and mudstone intervals, the base of which is highly mottled as is common in the lower units. Jeff Martz for scale. Photo taken by Randall Irmis.
Ghost Ranch and the Chinle Formation of the Chama Basin, New Mexico
I'm spending the weekend with colleagues up at Ghost Ranch New Mexico looking at Chinle Formation outcrops in the Chama Basin and spending some time working at the Hayden Quarry. This is a photo of the Salitral Shale Tongue of the Chinle Formation near Youngsville (photo courtesy of Randall Irmis).
My Thoughts on the Peer Review Process (Part 2) - Including Dissenting Opinions
[see Part 1 here]
The peer review process is time consuming and thus inconvenient, and as stated several times during this debate, doesn’t always work properly. But I would argue that good peer review is absolutely crucial to not only the publication process, but in also ensuring that the author is putting forth the finest written, best supported and documented, piece of work that they can with the data available at that time. To do any less will only open yourself and your work up to criticism and ensure that your work will not have lasting effect on the field of paleontology. I consider one of the most important aspects of peer review is that of seeking how the specialists (i.e., persons actively researching and publishing in a certain aspect of the science) in your field regard your work, after all they will be the persons reading it more in depth and hopefully drawing upon it in future work. Often this may even entail having your work reviewed by a rival. After all isn’t it this person or group’s opinion that you want up front to know how your published paper will be regarded? If you include them in the process and address their concerns, you all may still not agree, but at least you are showing professional courtesy.
Recently on this blog I criticized a recent paper on aetosaurs (the group I study the most), where I expressed disappointment in the work because I felt that it was not well-documented (e.g., description and figures) or supported, and thus would not be of much use to myself or other colleagues conducting work on the Aetosauria. Besides these authors, there are two persons in North America who are actively studying and publishing on this group at this time. Neither was considered as a reviewer for this manuscript. The two reviewers who were utilized are highly competent, respected scientists who have published extensively on the Triassic, however, neither are experts in the taxonomic group, or the genus Typothorax, that is the focus of the paper. I will assume that the reason that the two North American aetosaur workers (including myself) were not asked is because the authors specifically requested that they not be used as reviewers. Presumably this would be because of past history (i. e. “aetogate” ) between these individuals and the authors, and that the authors of the Typothorax paper felt they would not get a fair review. If correct, this is extremely unfortunate, because that assumes that I would not objectively review the manuscript and instead would be petty and vindictive. This would not have been the case at all. In fact, having read the published manuscript (and seen first hand the specimens that were described) I would not have rejected the manuscript. I would have suggested that the description be fleshed out, incorporating details of the skull and providing comparisons with other Typothorax and aetosaur specimens; I would have asked that the figures be better labeled so that important details would be more clear; I would have asked for new data regarding the taxonomic points being made, and pointed out a few places were relevant literature has not been cited or had been misrepresented. Had all of this been done, I would have had very little criticism of the paper and indeed probably would have found it very useful (and thus positively citable) in my future work. It would have been of little use for me, if requested as a reviewer, to be petty and vindictive as this would have been seen through by the editor and would have done nobody any good [Before anyone says it, I’ll admit that my blog post review of the paper was a bit harsh in spots, but this was based mainly on frustration with what could have been, and of course my comments were made on a personal blog (everyone should understand that by their nature blog posts are prone to outbursts) and does not constitute a professional review for the purposes of journal peer review].
Interestingly, I have a paper in press (also on aetosaurs) where I did specifically request a “rival” as a reviewer. Of course I knew based on past circumstances that the person might be highly critical, proclaim the work unworthy of such a prominent journal, and reject it outright; and sure enough (and sadly as I was hoping to be wrong) a multiple page, scathing (and often very snarky) review came back completely rejecting the paper (the other two reviews were positive). In the end, however, the paper was accepted. Why? I’m presuming because of the other two positive reviews, and because I warned the editor ahead of time that I was requesting a potentially hostile reviewer and that a scathing rejection (but with useful comments) could be expected. This was seriously risky; however, in between the scathing, snarky comments, and the unsupported criticisms, were very useful comments that positively increased the quality of the final paper. These types of comments can often only be received from someone who does not like or agree with your work, and often allows you to see what their concerns are and to help identify the holes in your own argument in contrast to theirs. This resulted in a much better paper, containing portions that would have been lacking if I had not made this reviewer selection.
Thus, this will hopefully alleviate some of the future criticism of this paper from this reviewer as I was professionally courteous in including them in the process (instead of the paper being a surprise) and did cover many of their concerns. Overall this will hopefully result in a much more useful paper for all involved. Of course, this reviewer requested to remain anonymous and they would probably be stunned to know that I am clearly aware of their identity simply because I am the one who requested them as a reviewer. They may even be stunned that I even made such a request. Peer review is not about simply arranging for a close colleague to read through your work, nod approvingly, and then hand it back. You want someone who will critically, but fairly, tear the paper apart, and seeking out weaknesses in reasoning or support. Proper review, although inconvenient, almost always results in a much superior final product.
I think that we owe it to ourselves to make sure that our published work as paleontologists is of the highest standard methodologically, thus well thought out, well supported, and repeatable. Of course we will all never agree with the various hypotheses and conclusions, but we can all agree when a study is well done regardless of its results. Peer review is a crucial step in this process. We need the comments of our peers, including those who disagree with us, to ensure that we are meeting these scientific criteria and to improve our work. To do any less may be easier, and more convenient, but in the end it only lessens the influence of our work in the eyes of the scientific community.
One final note. E-mailing a peer who does not personally know you well and asking them to look something over for you does not constitute proper peer review. Often you will get back a reply that is simply based on pleasant correspondence etiquette, and the same detail will not go into the review as when the paper is presented by an editor for the person to judge if worthy of publication.
The peer review process is time consuming and thus inconvenient, and as stated several times during this debate, doesn’t always work properly. But I would argue that good peer review is absolutely crucial to not only the publication process, but in also ensuring that the author is putting forth the finest written, best supported and documented, piece of work that they can with the data available at that time. To do any less will only open yourself and your work up to criticism and ensure that your work will not have lasting effect on the field of paleontology. I consider one of the most important aspects of peer review is that of seeking how the specialists (i.e., persons actively researching and publishing in a certain aspect of the science) in your field regard your work, after all they will be the persons reading it more in depth and hopefully drawing upon it in future work. Often this may even entail having your work reviewed by a rival. After all isn’t it this person or group’s opinion that you want up front to know how your published paper will be regarded? If you include them in the process and address their concerns, you all may still not agree, but at least you are showing professional courtesy.
Recently on this blog I criticized a recent paper on aetosaurs (the group I study the most), where I expressed disappointment in the work because I felt that it was not well-documented (e.g., description and figures) or supported, and thus would not be of much use to myself or other colleagues conducting work on the Aetosauria. Besides these authors, there are two persons in North America who are actively studying and publishing on this group at this time. Neither was considered as a reviewer for this manuscript. The two reviewers who were utilized are highly competent, respected scientists who have published extensively on the Triassic, however, neither are experts in the taxonomic group, or the genus Typothorax, that is the focus of the paper. I will assume that the reason that the two North American aetosaur workers (including myself) were not asked is because the authors specifically requested that they not be used as reviewers. Presumably this would be because of past history (i. e. “aetogate” ) between these individuals and the authors, and that the authors of the Typothorax paper felt they would not get a fair review. If correct, this is extremely unfortunate, because that assumes that I would not objectively review the manuscript and instead would be petty and vindictive. This would not have been the case at all. In fact, having read the published manuscript (and seen first hand the specimens that were described) I would not have rejected the manuscript. I would have suggested that the description be fleshed out, incorporating details of the skull and providing comparisons with other Typothorax and aetosaur specimens; I would have asked that the figures be better labeled so that important details would be more clear; I would have asked for new data regarding the taxonomic points being made, and pointed out a few places were relevant literature has not been cited or had been misrepresented. Had all of this been done, I would have had very little criticism of the paper and indeed probably would have found it very useful (and thus positively citable) in my future work. It would have been of little use for me, if requested as a reviewer, to be petty and vindictive as this would have been seen through by the editor and would have done nobody any good [Before anyone says it, I’ll admit that my blog post review of the paper was a bit harsh in spots, but this was based mainly on frustration with what could have been, and of course my comments were made on a personal blog (everyone should understand that by their nature blog posts are prone to outbursts) and does not constitute a professional review for the purposes of journal peer review].
Interestingly, I have a paper in press (also on aetosaurs) where I did specifically request a “rival” as a reviewer. Of course I knew based on past circumstances that the person might be highly critical, proclaim the work unworthy of such a prominent journal, and reject it outright; and sure enough (and sadly as I was hoping to be wrong) a multiple page, scathing (and often very snarky) review came back completely rejecting the paper (the other two reviews were positive). In the end, however, the paper was accepted. Why? I’m presuming because of the other two positive reviews, and because I warned the editor ahead of time that I was requesting a potentially hostile reviewer and that a scathing rejection (but with useful comments) could be expected. This was seriously risky; however, in between the scathing, snarky comments, and the unsupported criticisms, were very useful comments that positively increased the quality of the final paper. These types of comments can often only be received from someone who does not like or agree with your work, and often allows you to see what their concerns are and to help identify the holes in your own argument in contrast to theirs. This resulted in a much better paper, containing portions that would have been lacking if I had not made this reviewer selection.
Thus, this will hopefully alleviate some of the future criticism of this paper from this reviewer as I was professionally courteous in including them in the process (instead of the paper being a surprise) and did cover many of their concerns. Overall this will hopefully result in a much more useful paper for all involved. Of course, this reviewer requested to remain anonymous and they would probably be stunned to know that I am clearly aware of their identity simply because I am the one who requested them as a reviewer. They may even be stunned that I even made such a request. Peer review is not about simply arranging for a close colleague to read through your work, nod approvingly, and then hand it back. You want someone who will critically, but fairly, tear the paper apart, and seeking out weaknesses in reasoning or support. Proper review, although inconvenient, almost always results in a much superior final product.
I think that we owe it to ourselves to make sure that our published work as paleontologists is of the highest standard methodologically, thus well thought out, well supported, and repeatable. Of course we will all never agree with the various hypotheses and conclusions, but we can all agree when a study is well done regardless of its results. Peer review is a crucial step in this process. We need the comments of our peers, including those who disagree with us, to ensure that we are meeting these scientific criteria and to improve our work. To do any less may be easier, and more convenient, but in the end it only lessens the influence of our work in the eyes of the scientific community.
One final note. E-mailing a peer who does not personally know you well and asking them to look something over for you does not constitute proper peer review. Often you will get back a reply that is simply based on pleasant correspondence etiquette, and the same detail will not go into the review as when the paper is presented by an editor for the person to judge if worthy of publication.
My Thoughts on the Peer Review Process (Part 1) - Self-Publication
The recent publication by Robert Gay of a self-printed set of theropod dinosaur papers using the printing service lulu.com has caused a rash of debate on blogs, the Dinosaur Mailing List, and even Facebook. Much of this debate regards whether the new taxonomic name, Kayentavenator elysiae, is valid under the ICZN. From what I can tell it is, furthermore the booklet has an ISSN number making it an official book or publication and thus the name is valid.
My issue with these papers (and I did purchase and read them) has been more regarding the issue of how they were peer reviewed. Robert claims they were both originally submitted to journals, accepted, but never actually published, thus he simply addressed the concerns of the reviewers and published them together in his own publically available booklet. I have discussed this with several of the reviewers listed and they vaguely remember reading the manuscripts, one even thought that the ms he read had been rejected. Nonetheless, my point (and one on currently concerned with regarding other potential publications discussed at the SVPOW blog) is that regardless of the outcome of the peer-review process conducted back in 2004, given numerous additional studies published in the six years since, these reviews are technically out of date and I argue no longer valid. Robert Gay should have rewritten his manuscripts, incorporating all pertinent recent literature, and then sent them back out for review. This surely would have lessened some of the firestorm.
Another concern would be editing. As Gay, through his actions, acted as both author and editor, where is the quality control to ensure he had incorporated the concerns of his reviewers accurately? Maybe he should have enlisted the aid of an outside editor? This is especially relevant as he introduced a new taxonomic name and thus would want to whole process to be as unambiguous as possible. A careful update, a few more reviews, and invited some editorial help may have lessened the controversy surrounding these papers and the new taxonomic name.
Why do I care? Primarily I am concerned with people who misrepresent themselves to the scientific community. All the time we see reference made to professionals vs. amateurs in regards to paleontological study and publishing, but what does this really mean? Does having a job (or a degree) where you get paid to do paleontology make you a better scientist than someone who does it as a side interest? Certainly not, and I think the history of the science will clearly support this. What matters is if good science is being done by the “professional” or “advocational” paleontologist. Is there a clear question being addressed, what is the quality of the data collected, are the hypotheses well thought out, supported, and testable? Does the paleontologist have a firm understanding of pertinent literature and is it properly cited? Has the study undergone an unambiguous peer review process to ensure that they have covered all of their bases and the work is considered sound? I've argued in the past that everyne has great hypotheses worthy of publication. Thus, it does not matter what your title is, all that matters is that if you want to publish your ideas, make sure you are producing good well-supported and repeatable science. That is what makes you a scientist, not a job or a degree. To do any less, yet still demand respect from peers, is misrepresenting yourself.
Second, I think that lulu.com can be a very valuable tool when used properly as a printing service. The SVP abstract books are now being offered in print through this venue, and it is an excellent choice for other types of publications including museum bulletin series, proceedings volumes, etc… As long as what is being printed has undergone proper peer review and editing. I’d hate to see this resource smeared in the scientific community because of mis-use by others in the field. As I stated elsewhere, lulu.com is a printing service, NOT a scientific journal.
Some have claimed that it is unfair to single out Robert Gay in these debates, as this type of publishing actually is more common than it should be, sometimes masquerading under the guise of a legitimate institution publication series, but his case is the most recent and the first to use lulu.com, thus certainly worthy of discussion. As scientists we should expect that any publishing we do will be scrutinized by the rest of the community.
[Part 2, will be posted Tuesday morning]
My issue with these papers (and I did purchase and read them) has been more regarding the issue of how they were peer reviewed. Robert claims they were both originally submitted to journals, accepted, but never actually published, thus he simply addressed the concerns of the reviewers and published them together in his own publically available booklet. I have discussed this with several of the reviewers listed and they vaguely remember reading the manuscripts, one even thought that the ms he read had been rejected. Nonetheless, my point (and one on currently concerned with regarding other potential publications discussed at the SVPOW blog) is that regardless of the outcome of the peer-review process conducted back in 2004, given numerous additional studies published in the six years since, these reviews are technically out of date and I argue no longer valid. Robert Gay should have rewritten his manuscripts, incorporating all pertinent recent literature, and then sent them back out for review. This surely would have lessened some of the firestorm.
Another concern would be editing. As Gay, through his actions, acted as both author and editor, where is the quality control to ensure he had incorporated the concerns of his reviewers accurately? Maybe he should have enlisted the aid of an outside editor? This is especially relevant as he introduced a new taxonomic name and thus would want to whole process to be as unambiguous as possible. A careful update, a few more reviews, and invited some editorial help may have lessened the controversy surrounding these papers and the new taxonomic name.
Why do I care? Primarily I am concerned with people who misrepresent themselves to the scientific community. All the time we see reference made to professionals vs. amateurs in regards to paleontological study and publishing, but what does this really mean? Does having a job (or a degree) where you get paid to do paleontology make you a better scientist than someone who does it as a side interest? Certainly not, and I think the history of the science will clearly support this. What matters is if good science is being done by the “professional” or “advocational” paleontologist. Is there a clear question being addressed, what is the quality of the data collected, are the hypotheses well thought out, supported, and testable? Does the paleontologist have a firm understanding of pertinent literature and is it properly cited? Has the study undergone an unambiguous peer review process to ensure that they have covered all of their bases and the work is considered sound? I've argued in the past that everyne has great hypotheses worthy of publication. Thus, it does not matter what your title is, all that matters is that if you want to publish your ideas, make sure you are producing good well-supported and repeatable science. That is what makes you a scientist, not a job or a degree. To do any less, yet still demand respect from peers, is misrepresenting yourself.
Second, I think that lulu.com can be a very valuable tool when used properly as a printing service. The SVP abstract books are now being offered in print through this venue, and it is an excellent choice for other types of publications including museum bulletin series, proceedings volumes, etc… As long as what is being printed has undergone proper peer review and editing. I’d hate to see this resource smeared in the scientific community because of mis-use by others in the field. As I stated elsewhere, lulu.com is a printing service, NOT a scientific journal.
Some have claimed that it is unfair to single out Robert Gay in these debates, as this type of publishing actually is more common than it should be, sometimes masquerading under the guise of a legitimate institution publication series, but his case is the most recent and the first to use lulu.com, thus certainly worthy of discussion. As scientists we should expect that any publishing we do will be scrutinized by the rest of the community.
[Part 2, will be posted Tuesday morning]
Recent Triassic Posts at Other Blogs
First, Dr. Hans Sues covers the conclusions of two recent papers on the rise of the dinosaurs in the Triassic:
http://blogs.nationalgeographic.com/blogs/news/chiefeditor/2010/06/rise-of-dinosaurs.html
Next up, Mickey Mortimer suggests that the indeterminate archosauriform Arctosaurus, known from a single incomplete vertebra from the Late Triassic of Nunavut, Canada may actually be a poposaurid:
http://theropoddatabase.blogspot.com/2010/06/arctosaurus-poposaurid.html
http://blogs.nationalgeographic.com/blogs/news/chiefeditor/2010/06/rise-of-dinosaurs.html
Next up, Mickey Mortimer suggests that the indeterminate archosauriform Arctosaurus, known from a single incomplete vertebra from the Late Triassic of Nunavut, Canada may actually be a poposaurid:
http://theropoddatabase.blogspot.com/2010/06/arctosaurus-poposaurid.html
New Study Suggests that Turtles are not Diapsids
Lyson, T. R., G. S. Bever, B. S. Bhullar, W. G. Joyce and J. A. Gauthier. In press. Transitional fossils and the origin of turtles. Biology Letters published online before print June 9, 2010, doi:10.1098/rsbl.2010.0371
Abstract - The origin of turtles is one of the most contentious issues in systematics with three currently viable hypotheses: turtles as the extant sister to (i) the crocodile-bird clade, (ii) the lizard-tuatara clade, or (iii) Diapsida (a clade composed of (i) and (ii)). We reanalysed a recent dataset that allied turtles with the lizard-tuatara clade and found that the inclusion of the stem turtle Proganochelys quenstedti and the 'parareptile' Eunotosaurus africanus results in a single overriding morphological signal, with turtles outside Diapsida. This result reflects the importance of transitional fossils when long branches separate crown clades, and highlights unexplored issues such as the role of topological congruence when using fossils to calibrate molecular clocks.
Abstract - The origin of turtles is one of the most contentious issues in systematics with three currently viable hypotheses: turtles as the extant sister to (i) the crocodile-bird clade, (ii) the lizard-tuatara clade, or (iii) Diapsida (a clade composed of (i) and (ii)). We reanalysed a recent dataset that allied turtles with the lizard-tuatara clade and found that the inclusion of the stem turtle Proganochelys quenstedti and the 'parareptile' Eunotosaurus africanus results in a single overriding morphological signal, with turtles outside Diapsida. This result reflects the importance of transitional fossils when long branches separate crown clades, and highlights unexplored issues such as the role of topological congruence when using fossils to calibrate molecular clocks.
Chindesaurus bryansmalli = "Gertie" the Dinosaur
In 1985 the holotype specimen of the basal theropod Chindesaurus bryansmalli was excavated in Petrified Forest National Park. At the time it was (erroneously) billed in the media as the world's "earliest dinosaur". The excavation was widely covered in the press with dozens of media passes distributed. The block was ceremoniously lifted out of the Painted Desert by helicopter, with noted paleontologists such as Samuel Welles and Edwin Colbert aboard the "historic" flight. A party was held in honor of this event at the nearby Painted Desert Inn, complete with food and dinosaur ice sculptures from the Fred Harvey Company and of course a far too common summer power outage. Park Rangers circled the building will vehicles, turned on their headlights, and the party continued.
At the time Chindesaurus was thought to represent a "prosauropod" based on it's primitive looking astragalus, but is now considered a herrerasaurid. The specimen was affectionately given the nickname "Gertie" by the excavators and even today this is how the specimen is often referred to by many park staff. In fact, when I first tried to find the specimen's catalogue record in 2001, it had been catalogued using this nickname rather than under Chindesaurus! Unfortunately, this name was far overused in 1980s and 90s park interpretive products and thus has been immortalized on the internet, as is readily apparent if one does an internet search for "Gertie" and "Petrified Forest". Nonetheless, this specimen was very popular when first recovered, and casts of the skeleton are still on exhibit at the Rainbow Forest Museum. For those of you who are not familiar, the name stems from one of the earliest animated films ever made (1914), which featured a dinosaur named "Gertie" who would respond to commands by the animator and perform for audiences. This short is still considered to be one of the most important animated films ever made.
At the time Chindesaurus was thought to represent a "prosauropod" based on it's primitive looking astragalus, but is now considered a herrerasaurid. The specimen was affectionately given the nickname "Gertie" by the excavators and even today this is how the specimen is often referred to by many park staff. In fact, when I first tried to find the specimen's catalogue record in 2001, it had been catalogued using this nickname rather than under Chindesaurus! Unfortunately, this name was far overused in 1980s and 90s park interpretive products and thus has been immortalized on the internet, as is readily apparent if one does an internet search for "Gertie" and "Petrified Forest". Nonetheless, this specimen was very popular when first recovered, and casts of the skeleton are still on exhibit at the Rainbow Forest Museum. For those of you who are not familiar, the name stems from one of the earliest animated films ever made (1914), which featured a dinosaur named "Gertie" who would respond to commands by the animator and perform for audiences. This short is still considered to be one of the most important animated films ever made.
New Book Available - The Triassic Timescale
Available now, Geological Society of London Special Publication 334, The Triassic Timescale, edited by S. G. Lucas. The table of contents is listed below and you can find out more about the book and order it here. The PDF of the introductory article is also available as a free download. Note that in this introductory article Lucas rejects the recent long Norian hypothesis basing this rejection on vertebrate, pollen, and conchostracan biochronology. For a detailed discussion of this I'll refer interested parties again to the recent paper by Irmis et al. (2010).
LUCAS, S. G. The Triassic timescale: an introduction.
LUCAS, S. G. The Triassic chronostratigraphic scale: history and status.
MUNDIL, R., PÁLFY, J., RENNE, P. R. & BRACK, P. The Triassic timescale: new constraints and a review of geochronological data.
HOUNSLOW, M. W. &MUTTONI, G. The geomagnetic polarity timescale for the Triassic: linkage to stage boundary definitions.
TANNER, L. H. The Triassic isotope record.
TANNER, L. H. Cyclostratigraphic record of the Triassic: a critical examination.
ORCHARD, M. J. Triassic conodonts and their role in stage boundary definition.
O’DOGHERTY, L., CARTER, E. S., GORIČAN, Š., & DUMITRICA, P. Triassic radiolarian biostratigraphy.
MCROBERTS, C. A. Biochronology of Triassic bivalves.
BALINI, M., LUCAS, S. G., JENKS, J. F. & SPIELMANN, J. A. Triassic ammonoid biostratigraphy: an overview.
KÜRSCHNER, W. M. & WALDEMAAR HERNGREEN, G. F. Triassic palynology of central and northwestern Europe: a review of palynofloral diversity patterns and biostratigraphic subdivisions.
CIRILLI, S. Upper Triassic–lowermost Jurassic palynology and palynostratigraphy: a review.
KOZUR, H. W. & WEEMS, R. E. The biostratigraphic importance of conchostracans in the continental Triassic of the northern hemisphere.
KLEIN, H. & LUCAS, S. G. Tetrapod footprints – their use in biostratigraphy and biochronology of the Triassic.
LUCAS, S. G. The Triassic timescale based on nonmarine tetrapod biostratigraphy and biochronology.
LUCAS, S. G. The Triassic timescale: an introduction.
LUCAS, S. G. The Triassic chronostratigraphic scale: history and status.
MUNDIL, R., PÁLFY, J., RENNE, P. R. & BRACK, P. The Triassic timescale: new constraints and a review of geochronological data.
HOUNSLOW, M. W. &MUTTONI, G. The geomagnetic polarity timescale for the Triassic: linkage to stage boundary definitions.
TANNER, L. H. The Triassic isotope record.
TANNER, L. H. Cyclostratigraphic record of the Triassic: a critical examination.
ORCHARD, M. J. Triassic conodonts and their role in stage boundary definition.
O’DOGHERTY, L., CARTER, E. S., GORIČAN, Š., & DUMITRICA, P. Triassic radiolarian biostratigraphy.
MCROBERTS, C. A. Biochronology of Triassic bivalves.
BALINI, M., LUCAS, S. G., JENKS, J. F. & SPIELMANN, J. A. Triassic ammonoid biostratigraphy: an overview.
KÜRSCHNER, W. M. & WALDEMAAR HERNGREEN, G. F. Triassic palynology of central and northwestern Europe: a review of palynofloral diversity patterns and biostratigraphic subdivisions.
CIRILLI, S. Upper Triassic–lowermost Jurassic palynology and palynostratigraphy: a review.
KOZUR, H. W. & WEEMS, R. E. The biostratigraphic importance of conchostracans in the continental Triassic of the northern hemisphere.
KLEIN, H. & LUCAS, S. G. Tetrapod footprints – their use in biostratigraphy and biochronology of the Triassic.
LUCAS, S. G. The Triassic timescale based on nonmarine tetrapod biostratigraphy and biochronology.
New Data on Rising Carbon Dioxide Levels Through the Triassic-Jurassic Transistion
Bonis, N. R., Van Konijnenburg-Van Cittert, J. H. A., and W. M. Kürschner. in press. Changing CO2 conditions during the end-Triassic inferred from stomatal frequency analysis on Lepidopteris ottonis (Goeppert) Schimper and Ginkgoites taeniatus (Braun) Harris, Palaeogeography, Palaeoclimatology, Palaeoecology (2010), doi:10.1016/j.palaeo.2010.05.034
End-Triassic fluctuations in atmospheric carbon dioxide (CO2) concentration were reconstructed by the use of stomatal frequency analysis on a single plant species: the seedfern Lepidopteris ottonis (Goeppert) Schimper. Stomatal index showed no distinct intra- and interpinnule variation which makes it a suitable proxy for past relative CO2 changes. Records of decreasing stomatal index and density from the bottom to the top of the Rhaetian– Hettangian Wüstenwelsberg section (Bavaria, Germany) indicate rising CO2 levels during the Triassic–Jurassic transition. Additionally, stomatal frequency data of fossil ginkgoalean leaves (Ginkgoites taeniatus (Braun) Harris) suggest a maximum palaeoatmospheric CO2 concentration of 2750 ppmv for the latest Triassic.
End-Triassic fluctuations in atmospheric carbon dioxide (CO2) concentration were reconstructed by the use of stomatal frequency analysis on a single plant species: the seedfern Lepidopteris ottonis (Goeppert) Schimper. Stomatal index showed no distinct intra- and interpinnule variation which makes it a suitable proxy for past relative CO2 changes. Records of decreasing stomatal index and density from the bottom to the top of the Rhaetian– Hettangian Wüstenwelsberg section (Bavaria, Germany) indicate rising CO2 levels during the Triassic–Jurassic transition. Additionally, stomatal frequency data of fossil ginkgoalean leaves (Ginkgoites taeniatus (Braun) Harris) suggest a maximum palaeoatmospheric CO2 concentration of 2750 ppmv for the latest Triassic.
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