Ezcurra, M. D. 2010. A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny. Journal of Systematic Palaeontology 8: 371-425.
Abstract - It was traditionally thought that the oldest known dinosaur assemblages were not diverse, and that their early diversification and numerical dominance over other tetrapods occurred during the latest Triassic. However, new evidence gathered from the lower levels of the Ischigualasto Fm. of Argentina challenges this view. New dinosaur remains are described from this stratigraphical unit, including the new species Chromogisaurus novasi. This taxon is distinguished from other basal dinosauriforms by the presence of proximal caudals without median notch separating the postzygapophyses, femoral lateral surface with deep and large fossa immediately below the trochanteric shelf, and metatarsal II with strongly dorsoventrally asymmetric distal condyles. A phylogenetic analysis found Chromogisaurus to lie at the base of Sauropodomorpha, as a member of Guaibasauridae, an early branch of basal sauropodomorphs composed of Guaibasaurus, Agnosphitys, Panphagia, Saturnalia and Chromogisaurus. Such an affinity is for the first time suggested for Guaibasaurus, whereas Panphagia is not recovered as the most basal sauropodomorph. Furthermore, Chromogisaurus is consistently located as more closely related to Saturnalia than to any other dinosaur. Thus, the Saturnalia + Chromogisaurus clade is named here as the new subfamily Saturnaliinae. In addition, Eoraptor is found to be the sister-taxon of Neotheropoda, and herrerasaurids to be non-eusaurischian saurischians. The new evidence presented here demonstrates that dinosaurs first appeared in the fossil record as a diverse group, although they were a numerically minor component of faunas in which they occur. Accordingly, the early increase of dinosaur diversity and their numerical dominance over other terrestrial tetrapods were diachronous processes, with the latter preceded by a period of low abundance but high diversity.
Besides the information provided in the abstract here are a couple of other tidbits:
1) Diagnosis: the holotype material is very fragmentary, but Chromogisaurus novasi is diagnosed by "the following combination of characteristics (autapomorphies∗): proximal caudals without median notch separating the postzygapophyses; ilium with strongly posteriorly developed postacetabular process; incipiently perforated acetabulum; a femoral lateral surface with deep and large fossa immediately below the trochanteric shelf;∗ and a metatarsal II with strongly dorsoventrally asymmetric distal condyles" (Ezcurra, 2010:374).
2) Etymology: The generic name is a combination of the Greek "chroma" (color) and "gi" (ground or land) for the Painted Valley where the specimen was collected.
3) Clades: This paper provides definitions for the newly recovered clades Guaibasauridae and Saturnaliinae.
4) Chindesaurus: The paper contains discussion on the phylogenetic position of Chindesaurus bryansmalli from the Chinle Formation. This study (378 characters) finds Chindesaurus as eithr a basal theropod or as a non-eusaurischian saurischian.
5) Photos: There is a nice comparative figure (photos) of the skulls of Herrerasaurus, Eoraptor, and Zupaysaurus.
I'm looking forward to reading the rest of this....
Pterosauria from the Late Triassic of Southern Brazil
This is an article in a recent book titled New Aspects of Mesozoic Biodiversity, part of SpringerLinks Lecture Notes in Earth Sciences book series.
Bonaparte, J. F., Schultz, C. L., and M. B. Soares. 2010. Pterosauria from the Late Triassic of Southern Brazil, pp. 63-71 in Bandyopadhyay, S. (ed.), New Aspects of Mesozoic Biodiversity, Lecture Notes in Earth Sciences 132, Springer-Verlag Berlin/ Heidelberg, DOI: 10.1007/978-3-642-10311-7
Abstract - A few postcranial remains of a Late Triassic pterosaur from the early Coloradian Caturrita Formation of Rio Grande do Sul are communicated. The general morphology of the coracoid, proximal portion of the humerus, femur, tibia and fibula suggests that it is more primitive than the pterosaurs from the Norian of northern Italy. The morphology and proportions of the different bones support their assignment to a primitive pterosaur. An almost complete maxilla with three teeth is tentatively referred to the same taxon because it was collected at some distance from the postcrania cited above. This pterosaur is possibly older than other Triassic pterosaurs and was recorded from a typical terrestrial environment. It suggests that the earliest pterosaurs evolved in continental and littoral marine environments.
Bonaparte, J. F., Schultz, C. L., and M. B. Soares. 2010. Pterosauria from the Late Triassic of Southern Brazil, pp. 63-71 in Bandyopadhyay, S. (ed.), New Aspects of Mesozoic Biodiversity, Lecture Notes in Earth Sciences 132, Springer-Verlag Berlin/ Heidelberg, DOI: 10.1007/978-3-642-10311-7
Abstract - A few postcranial remains of a Late Triassic pterosaur from the early Coloradian Caturrita Formation of Rio Grande do Sul are communicated. The general morphology of the coracoid, proximal portion of the humerus, femur, tibia and fibula suggests that it is more primitive than the pterosaurs from the Norian of northern Italy. The morphology and proportions of the different bones support their assignment to a primitive pterosaur. An almost complete maxilla with three teeth is tentatively referred to the same taxon because it was collected at some distance from the postcrania cited above. This pterosaur is possibly older than other Triassic pterosaurs and was recorded from a typical terrestrial environment. It suggests that the earliest pterosaurs evolved in continental and littoral marine environments.
New in Palaeotologia Electronica: The Digital Plateosaurus.
The new issue of Palaeontologia Electronica is now available online including this article:
Mallison, H. 2010. The digital Plateosaurus I: body mass, mass distribution and posture assessed using CAD and CAE on a digitally mounted complete skeleton. Palaeontologia Electronica Vol. 13, Issue 2; 8A: 26p; http://palaeo-electronica.org/2010_2/198/index.html
Abstract - Plateosaurus from the late Triassic of Central Europe is one of the best known dinosaurs. Despite the large number of finds, including complete and articulated skeletons, its posture and locomotion capabilities are still being debated. While recent assessments of the range of motion of the forelimb indicate that Plateosaurus was incapable of manus pronation, and thus an obligate biped, practically all other possible alternatives have been suggested in the literature. Here, I present evidence, derived from a detailed mounting of a 3D digital skeleton and a computer-aided engineering assessment of a digital 3D model of the living animal, that Plateosaurus was indeed an obligate biped. The position of the center of mass is assessed in several variations of the basic model to account for differing interpretations of soft tissue amounts. All models allow a stable bipedal pose with a subhorizontal back that is consistent with the requirements of both slow and rapid locomotion. Quadrupedal models, in contrast, suffer from locomotion restrictions due to highly uneven limb lengths and a limited motion range in the forelimb, and result in a smaller feeding envelope.
Mallison, H. 2010. The digital Plateosaurus I: body mass, mass distribution and posture assessed using CAD and CAE on a digitally mounted complete skeleton. Palaeontologia Electronica Vol. 13, Issue 2; 8A: 26p; http://palaeo-electronica.org/2010_2/198/index.html
Abstract - Plateosaurus from the late Triassic of Central Europe is one of the best known dinosaurs. Despite the large number of finds, including complete and articulated skeletons, its posture and locomotion capabilities are still being debated. While recent assessments of the range of motion of the forelimb indicate that Plateosaurus was incapable of manus pronation, and thus an obligate biped, practically all other possible alternatives have been suggested in the literature. Here, I present evidence, derived from a detailed mounting of a 3D digital skeleton and a computer-aided engineering assessment of a digital 3D model of the living animal, that Plateosaurus was indeed an obligate biped. The position of the center of mass is assessed in several variations of the basic model to account for differing interpretations of soft tissue amounts. All models allow a stable bipedal pose with a subhorizontal back that is consistent with the requirements of both slow and rapid locomotion. Quadrupedal models, in contrast, suffer from locomotion restrictions due to highly uneven limb lengths and a limited motion range in the forelimb, and result in a smaller feeding envelope.
Feeding-Related Characters in Basal Pterosaurs
Osi, A. 2010: Feeding-related characters in basal pterosaurs: implications for jaw mechanism, dental function and diet. Lethaia, DOI: 10.1111/j.1502-3931.2010.00230.x.
Abstract - A comparative study of various feeding-related features in basal pterosaurs reveals a significant change in feeding strategies during the early evolutionary history of the group. These features are related to the skull architecture (e.g. quadrate morphology and orientation, jaw joint), dentition (e.g. crown morphology, wear patterns), reconstructed adductor musculature and post-cranium. The most basal pterosaurs (Preondactylus, dimorphodontids and anurognathids) were small-bodied animals with a wingspan no greater than 1.5 m, a relatively short, lightly constructed skull, straight mandibles with a large gape, sharply pointed teeth and well-developed external adductors. The absence of extended tooth wear excludes complex oral food processing and indicates that jaw closure was simply orthal. Features of these basal-most forms indicate a predominantly insectivorous diet. Among stratigraphically older but more derived forms (Eudimorphodon, Carniadactylus, Caviramus) complex, multicuspid teeth allowed the consumption of a wider variety of prey via a more effective form of food processing. This is supported by heavy dental wear in all forms with multicuspid teeth. Typical piscivorous forms occurred no earlier than the Early Jurassic, and are characterized by widely spaced, enlarged procumbent teeth forming a fish grab and an anteriorly inclined quadrate that permitted only a relatively small gape. In addition, the skull became more elongate and body size increased. Besides the dominance of piscivory, dental morphology and the scarcity of tooth wear reflect accidental dental occlusion that could have been caused by the capturing or seasonal consumption of harder food items.
Abstract - A comparative study of various feeding-related features in basal pterosaurs reveals a significant change in feeding strategies during the early evolutionary history of the group. These features are related to the skull architecture (e.g. quadrate morphology and orientation, jaw joint), dentition (e.g. crown morphology, wear patterns), reconstructed adductor musculature and post-cranium. The most basal pterosaurs (Preondactylus, dimorphodontids and anurognathids) were small-bodied animals with a wingspan no greater than 1.5 m, a relatively short, lightly constructed skull, straight mandibles with a large gape, sharply pointed teeth and well-developed external adductors. The absence of extended tooth wear excludes complex oral food processing and indicates that jaw closure was simply orthal. Features of these basal-most forms indicate a predominantly insectivorous diet. Among stratigraphically older but more derived forms (Eudimorphodon, Carniadactylus, Caviramus) complex, multicuspid teeth allowed the consumption of a wider variety of prey via a more effective form of food processing. This is supported by heavy dental wear in all forms with multicuspid teeth. Typical piscivorous forms occurred no earlier than the Early Jurassic, and are characterized by widely spaced, enlarged procumbent teeth forming a fish grab and an anteriorly inclined quadrate that permitted only a relatively small gape. In addition, the skull became more elongate and body size increased. Besides the dominance of piscivory, dental morphology and the scarcity of tooth wear reflect accidental dental occlusion that could have been caused by the capturing or seasonal consumption of harder food items.
Why Were Dicynodonts so Successful Before and After the End-Permian Extinction?
Botha-Brink, J., and K. Angielczyk. 2010. Do extraordinarily high growth rates in Permo-Triassic dicynodonts (Therapsida, Anomodontia) explain their success before and after the end-Permian extinction? Zoological Journal of the Linnean Society, early online, doi: 10.1111/j.1096-3642.2009.00601.x
Abstract - Dicynodonts were the most diverse and abundant herbivorous therapsids of the Permo-Triassic. They include Lystrosaurus, one of the few taxa known to survive the end-Permian extinction and the most abundant tetrapod during the Early Triassic postextinction recovery. Explanations for the success of Lystrosaurus and other dicynodonts remain controversial. This study presents an assessment of dicynodont growth patterns using bone histology, with special focus on taxa associated with the end-Permian extinction event. Bone histological analysis reveals a high cortical thickness throughout the clade, perhaps reflecting a phylogenetic constraint. Growth rings are absent early in ontogeny, and combined with high vascular density, indicate rapid, sustained growth up to the subadult stage. Extraordinarily enlarged vascular channels are present in the midcortex of many dicynodonts, including adults, and may have facilitated a more efficient assimilation of nutrients and rapid bone growth compared to other therapsids. Both increased channel density and enlarged vascular channels evolved at or near the base of major radiations of dicynodonts, implying that the changes in growth and life history they represent may have been key to the success of dicynodonts. Furthermore, this exceptionally rapid growth to adulthood may have contributed to the survival of Lystrosaurus during the end-Permian extinction and its dominance during the postextinction recovery period.
Abstract - Dicynodonts were the most diverse and abundant herbivorous therapsids of the Permo-Triassic. They include Lystrosaurus, one of the few taxa known to survive the end-Permian extinction and the most abundant tetrapod during the Early Triassic postextinction recovery. Explanations for the success of Lystrosaurus and other dicynodonts remain controversial. This study presents an assessment of dicynodont growth patterns using bone histology, with special focus on taxa associated with the end-Permian extinction event. Bone histological analysis reveals a high cortical thickness throughout the clade, perhaps reflecting a phylogenetic constraint. Growth rings are absent early in ontogeny, and combined with high vascular density, indicate rapid, sustained growth up to the subadult stage. Extraordinarily enlarged vascular channels are present in the midcortex of many dicynodonts, including adults, and may have facilitated a more efficient assimilation of nutrients and rapid bone growth compared to other therapsids. Both increased channel density and enlarged vascular channels evolved at or near the base of major radiations of dicynodonts, implying that the changes in growth and life history they represent may have been key to the success of dicynodonts. Furthermore, this exceptionally rapid growth to adulthood may have contributed to the survival of Lystrosaurus during the end-Permian extinction and its dominance during the postextinction recovery period.
Functional Implications of Dermal Bone Ornamentation in Basal Tetrapods
Metoposaurs are a very common component of the Chinle Formation fauna, especially the lower portions. I often get questions on the function of the ornament of metoposaur dermal bones (skull, clavicles, interclavicle) and finally some of those questions can be answered.
Witzmann, F., Scholz, H., Mueller, J., and N. Kardjilov. 2010. Sculpture and vascularization of dermal bones, and the implications for the physiology of basal tetrapods. Zoological Journal of the Linnean Society, early online. doi: 10.1111/j.1096-3642.2009.00599.x
Abstract - Sculpture of dermal bones and their vascularization in basal tetrapods are closely connected. Ontogenetic data suggest that the large vessels that coursed to the superficial bone surface induced the formation of sculptural ridges and tubercles around their openings. Imprints show that the vessels continued on the bone surface and coursed within furrows or pits, where they were protected by the sculpture from mechanical damage. Dermal bone histology indicates a consolidation of the integument in basal tetrapods by strong, mineralized Sharpey’s fibres in the sculptural ridges and tubercles, and by the presence of metaplastic tissue in several taxa. Because of the tight integration of bone and dermis, the large vessels were not able to spread over the sculptural elements, but instead had to pass interosseously. The diverse sculptural morphologies depend on the variation in height and width of the ‘nodal points’ and their connecting ridges, and in the size and shape of the enclosed cells and furrows. A principal component analysis (PCA) and discriminant function analysis (DFA) of 47 basal tetrapod taxa with 12 discrete characters shows that dermal sculpture is suited for distinguishing some main basal tetrapod lineages. Taxa that are interpreted as being largely aquatic have generally a more regular sculpture than presumably terrestrial ones.
Witzmann, F., Scholz, H., Mueller, J., and N. Kardjilov. 2010. Sculpture and vascularization of dermal bones, and the implications for the physiology of basal tetrapods. Zoological Journal of the Linnean Society, early online. doi: 10.1111/j.1096-3642.2009.00599.x
Abstract - Sculpture of dermal bones and their vascularization in basal tetrapods are closely connected. Ontogenetic data suggest that the large vessels that coursed to the superficial bone surface induced the formation of sculptural ridges and tubercles around their openings. Imprints show that the vessels continued on the bone surface and coursed within furrows or pits, where they were protected by the sculpture from mechanical damage. Dermal bone histology indicates a consolidation of the integument in basal tetrapods by strong, mineralized Sharpey’s fibres in the sculptural ridges and tubercles, and by the presence of metaplastic tissue in several taxa. Because of the tight integration of bone and dermis, the large vessels were not able to spread over the sculptural elements, but instead had to pass interosseously. The diverse sculptural morphologies depend on the variation in height and width of the ‘nodal points’ and their connecting ridges, and in the size and shape of the enclosed cells and furrows. A principal component analysis (PCA) and discriminant function analysis (DFA) of 47 basal tetrapod taxa with 12 discrete characters shows that dermal sculpture is suited for distinguishing some main basal tetrapod lineages. Taxa that are interpreted as being largely aquatic have generally a more regular sculpture than presumably terrestrial ones.
Two New Triassic Papers in Palaeo 3
Algeo, T. J., Kuwahara, K., Sano, H., Bates, S., Lyons, T., Elswick, E., Hinnov, L., Ellwood, B., Moser, J., and J. B. Maynard. 2010. Spatial variation in sediment fluxes, redox conditions, and productivity in the Permian-Triassic Panthalassic Ocean, Palaeogeography, Palaeoclimatology, Palaeoecology (2010), doi: 10.1016/j.palaeo.2010.07.007
Abstract - Two Permian/Triassic boundary sections in central Japan provide a rare window into environmental conditions within the Panthalassic Ocean, which encompassed more than half the Earth’s surface at 252 Ma. Integration of petrographic, geochemical, and time-series data provides new insights regarding the fluxes of major and trace components to the sediment as well as environmental conditions in both the deep and intermediate water masses at each study site. The Ubara section was located in a high-productivity peri-equatorial location, whereas the Gujo-Hachiman section was located in a moderate-productivity location at some distance from the paleoequator. An upward transition from gray organic-poor cherts to black siliceous mudstones at both sites occurred in conjunction with increased primary productivity, intensified euxinia within the oxygen-minimum zone (OMZ), and decimation of the radiolarian zooplankton community. Euxinia in the OMZ of the equatorial Panthalassic Ocean developed episodically for a ~200-250 kyr interval during the Late Permian, followed by an abrupt intensification and lateral expansion of the OMZ around the Permian-Triassic boundary. Throughout the study interval, bottom waters at both sites remained mostly suboxic, a finding that counters hypotheses of development of a “superanoxic” Permo-Triassic deep ocean as a consequence of stagnation of oceanic overturning circulation.
Shukla, U. K., Bachmann, G. H., and I. B. Singh. 2010. Facies architecture of the Stuttgart Formation (Schilfsandstein, Upper Triassic), central Germany, and its comparison with modern Ganga system, India, Palaeogeography Palaeoclimatology, Palaeoecology (2010), doi: 10.1016/j.palaeo.2010.07.019
Abstract - The Stuttgart Formation (Schilfsandstein) is approximately 50 m thick in Thuringia, representing deposition during the “Mid-Carnian Wet Intermezzo”. Stratigraphically it occurs between the Grabfeld and Weser formations, which formed under arid conditions. It comprises NNE-SSW-trending elongate, anastomosing channelised sand-rich bodies with erosional bases (channel belts) that are several kilometres wide and pass laterally into predominantly mudstones deposited in interfluve areas. The source area of these clastics was the uplifted Norwegian Caledonides. Muddy interfluve facies is dominant in exposures in Thuringia, Central Germany. The Lower Stuttgart Formation has an unconformable base that is locally overlain by meter-thick “Basal Beds”. These consist of grey mudstones and thin sandstones deposited under humid conditions in predominantly shallow brackish water environments after a marine ingression via the Eastern Carpathian/Upper Silesian Gate. The following 30–40 m- grey, finegrained sandstones, siltstones and mudstones were deposited in fluvial environments in channel belts and interfluve areas under humid conditions. These are followed by predominantly reddish mudstones and sandstones of mainly fluvial origin, deposited under somewhat drier conditions with seasonal droughts. The Upper Stuttgart Formation may be more than 16 mthick; it comprises reddish and grey sandstones and mudstones that were mostly deposited in lake-delta settings by recurring flash floods. During the deposition of this unit climate was weakly humid with less prominent seasonal draughts. The modern Ganga Plain of India is an analogue for the depositional setting of the Stuttgart Formation. Climatic conditions in Ganga Plain are humid monsoonal with seasonal droughts and roughly comparable with those interpreted for Mid-Carnian times in Germany. The sandy deposits of incised channel belts and channels and muddy deposits of interfluve areas in the Ganga Plain are comparable with the sandstone-dominated channelized facies and mudstone-dominated interfluve facies of the Stuttgart Formation, respectively.
Abstract - Two Permian/Triassic boundary sections in central Japan provide a rare window into environmental conditions within the Panthalassic Ocean, which encompassed more than half the Earth’s surface at 252 Ma. Integration of petrographic, geochemical, and time-series data provides new insights regarding the fluxes of major and trace components to the sediment as well as environmental conditions in both the deep and intermediate water masses at each study site. The Ubara section was located in a high-productivity peri-equatorial location, whereas the Gujo-Hachiman section was located in a moderate-productivity location at some distance from the paleoequator. An upward transition from gray organic-poor cherts to black siliceous mudstones at both sites occurred in conjunction with increased primary productivity, intensified euxinia within the oxygen-minimum zone (OMZ), and decimation of the radiolarian zooplankton community. Euxinia in the OMZ of the equatorial Panthalassic Ocean developed episodically for a ~200-250 kyr interval during the Late Permian, followed by an abrupt intensification and lateral expansion of the OMZ around the Permian-Triassic boundary. Throughout the study interval, bottom waters at both sites remained mostly suboxic, a finding that counters hypotheses of development of a “superanoxic” Permo-Triassic deep ocean as a consequence of stagnation of oceanic overturning circulation.
Shukla, U. K., Bachmann, G. H., and I. B. Singh. 2010. Facies architecture of the Stuttgart Formation (Schilfsandstein, Upper Triassic), central Germany, and its comparison with modern Ganga system, India, Palaeogeography Palaeoclimatology, Palaeoecology (2010), doi: 10.1016/j.palaeo.2010.07.019
Abstract - The Stuttgart Formation (Schilfsandstein) is approximately 50 m thick in Thuringia, representing deposition during the “Mid-Carnian Wet Intermezzo”. Stratigraphically it occurs between the Grabfeld and Weser formations, which formed under arid conditions. It comprises NNE-SSW-trending elongate, anastomosing channelised sand-rich bodies with erosional bases (channel belts) that are several kilometres wide and pass laterally into predominantly mudstones deposited in interfluve areas. The source area of these clastics was the uplifted Norwegian Caledonides. Muddy interfluve facies is dominant in exposures in Thuringia, Central Germany. The Lower Stuttgart Formation has an unconformable base that is locally overlain by meter-thick “Basal Beds”. These consist of grey mudstones and thin sandstones deposited under humid conditions in predominantly shallow brackish water environments after a marine ingression via the Eastern Carpathian/Upper Silesian Gate. The following 30–40 m- grey, finegrained sandstones, siltstones and mudstones were deposited in fluvial environments in channel belts and interfluve areas under humid conditions. These are followed by predominantly reddish mudstones and sandstones of mainly fluvial origin, deposited under somewhat drier conditions with seasonal droughts. The Upper Stuttgart Formation may be more than 16 mthick; it comprises reddish and grey sandstones and mudstones that were mostly deposited in lake-delta settings by recurring flash floods. During the deposition of this unit climate was weakly humid with less prominent seasonal draughts. The modern Ganga Plain of India is an analogue for the depositional setting of the Stuttgart Formation. Climatic conditions in Ganga Plain are humid monsoonal with seasonal droughts and roughly comparable with those interpreted for Mid-Carnian times in Germany. The sandy deposits of incised channel belts and channels and muddy deposits of interfluve areas in the Ganga Plain are comparable with the sandstone-dominated channelized facies and mudstone-dominated interfluve facies of the Stuttgart Formation, respectively.
Deposition and Preservation in the Upper Triassic Solite Quarry Lagerstätte in Virginia
Liutkus, C.M., Beard, J.S., Fraser, N.C., and P. C. Ragland. 2010. Use of fine-scale stratigraphy and chemostratigraphy to evaluate conditions of deposition and preservation of a Triassic Lagerstätte, south-central Virginia. Journal of Paleolimnology 44(2):645-666. doi: 10.1007/s10933-010-9445-1.
Abstract - The rich, fossiliferous Triassic sediments exposed in the Virginia Solite Quarry include a 34-mm-thick “insect layer” that is notable for detailed preservation of soft-bodied invertebrate and vertebrate remains. We describe this unique Konservat-Lagerstätte and use sedimentologic and geochemical analyses to interpret the environmental conditions necessary to preserve such delicate fossils. This work is among the first attempts to apply detailed geochemical/stratigraphic analysis to the study of Lagerstätten and we report on a 332-mm-thick section that includes the insect layer and the rocks immediately below and above it. Our analysis successfully constrains various aspects of the depositional and diagenetic history of the Lagerstätte and permits a detailed analysis of changing conditions prior to, during, and after deposition. Geochemical and sedimentologic analyses of the insect layer and surrounding lithologies reveal a change from siliciclastic-dominated layers (Unit 1) to dolomite-siliciclastic laminites above (Unit 2 and the insect layer), separated by a boundary dolostone layer that is traceable for over 200 m. We interpret this sedimentary shift as the initial stages in the transgression of a shallow, saline, alkaline rift-basin lake over lake margin deposits. The absence of bioturbation by plants and benthic organisms, as well as a lack of predation on the insects, is not explained by significant water depth, but is instead more reasonably considered a result of the chemistry of the water at the lake margin, affected by groundwater seeps, which provided F-, Mg-, and Ca-rich fluids. Although the initial conditions of preservation are remarkable, it is equally impressive that the fossils survived extensive diagenesis, e.g. dissolution of quartz and coarsening of dolomite.
Abstract - The rich, fossiliferous Triassic sediments exposed in the Virginia Solite Quarry include a 34-mm-thick “insect layer” that is notable for detailed preservation of soft-bodied invertebrate and vertebrate remains. We describe this unique Konservat-Lagerstätte and use sedimentologic and geochemical analyses to interpret the environmental conditions necessary to preserve such delicate fossils. This work is among the first attempts to apply detailed geochemical/stratigraphic analysis to the study of Lagerstätten and we report on a 332-mm-thick section that includes the insect layer and the rocks immediately below and above it. Our analysis successfully constrains various aspects of the depositional and diagenetic history of the Lagerstätte and permits a detailed analysis of changing conditions prior to, during, and after deposition. Geochemical and sedimentologic analyses of the insect layer and surrounding lithologies reveal a change from siliciclastic-dominated layers (Unit 1) to dolomite-siliciclastic laminites above (Unit 2 and the insect layer), separated by a boundary dolostone layer that is traceable for over 200 m. We interpret this sedimentary shift as the initial stages in the transgression of a shallow, saline, alkaline rift-basin lake over lake margin deposits. The absence of bioturbation by plants and benthic organisms, as well as a lack of predation on the insects, is not explained by significant water depth, but is instead more reasonably considered a result of the chemistry of the water at the lake margin, affected by groundwater seeps, which provided F-, Mg-, and Ca-rich fluids. Although the initial conditions of preservation are remarkable, it is equally impressive that the fossils survived extensive diagenesis, e.g. dissolution of quartz and coarsening of dolomite.
Two New Biology/Paleontology Blogs
By some strange cosmic cooincidence both the Witmer Lab and the Holliday Lab launched new blogs at nearly the same microsecond. Check them out.
http://witmerlab.wordpress.com/
http://hollidaylab.wordpress.com/
I see that Paleo Errata, but not Chinleana, made the Blogroll at Pick & Scapel, Guess I need to make my posts a little more ....um...how do you say it? Martzified? ;)
http://witmerlab.wordpress.com/
http://hollidaylab.wordpress.com/
I see that Paleo Errata, but not Chinleana, made the Blogroll at Pick & Scapel, Guess I need to make my posts a little more ....um...how do you say it? Martzified? ;)
New Triassic Paper in PloS ONE
Klein, N. 2010. Long Bone Histology of Sauropterygia from the Lower Muschelkalk of the Germanic Basin Provides Unexpected Implications for Phylogeny. PLoS ONE 5(7): e11613. doi:10.1371/journal.pone.0011613
Abstract
Background
Sauropterygia is an abundant and successful group of Triassic marine reptiles. Phylogenetic relationships of Triassic Sauropterygia have always been unstable and recently questioned. Although specimens occur in high numbers, the main problems are rareness of diagnostic material from the Germanic Basin and uniformity of postcranial morphology of eosauropterygians. In the current paper, morphotypes of humeri along with their corresponding bone histologies for Lower to Middle Muschelkalk sauropterygians are described and interpreted for the first time in a phylogenetic context.
Methodology/Principal Findings
Nothosaurus shows a typical plesiomorphic lamellar-zonal bone type, but varying growth patterns and the occurrence of a new humerus morphotype point to a higher taxonomic diversity than was known. In contrast to the enormous morphological variability of eosauropterygian humeri not assigned to Nothosaurus, their long bone histology is relatively uniform and can be divided into two histotypes. Unexpectedly, both of these histotypes reveal abundant fibrolamellar bone throughout the cortex. This pushes the origin of fibrolamellar bone in Sauropterygia back from the Cretaceous to the early Middle Triassic (early Anisian). Histotype A is assigned to Cymatosaurus, a basal member of the Pistosauroidea, which includes the plesiosaurs as derived members. Histotype B is related to the pachypleurosaur Anarosaurus. Contrary to these new finds, the stratigraphically younger pachypleurosaur Neusticosaurus shows the plesiomorphic lamellar-zonal bone type and an incomplete endochondral ossification, like Nothosaurus.
Conclusions/Significance
Histological results hypothetically discussed in a phylogenetical context have a large impact on the current phylogenetic hypothesis of Sauropterygia, leaving the pachypleurosaurs polyphyletic. On the basis of histological data, Neusticosaurus would be related to Nothosaurus, whereas Anarosaurus would follow the pistosaur clade. Furthermore, the presence of fibrolamellar bone, which is accompanied with increased growth rates and presumably even with increased metabolic rates, already in Anarosaurus and Cymatosaurus can explain the success of the Pistosauroidea, the only sauropterygian group to survive into the Jurassic and give rise to the pelagic plesiosaur radiation.
Abstract
Background
Sauropterygia is an abundant and successful group of Triassic marine reptiles. Phylogenetic relationships of Triassic Sauropterygia have always been unstable and recently questioned. Although specimens occur in high numbers, the main problems are rareness of diagnostic material from the Germanic Basin and uniformity of postcranial morphology of eosauropterygians. In the current paper, morphotypes of humeri along with their corresponding bone histologies for Lower to Middle Muschelkalk sauropterygians are described and interpreted for the first time in a phylogenetic context.
Methodology/Principal Findings
Nothosaurus shows a typical plesiomorphic lamellar-zonal bone type, but varying growth patterns and the occurrence of a new humerus morphotype point to a higher taxonomic diversity than was known. In contrast to the enormous morphological variability of eosauropterygian humeri not assigned to Nothosaurus, their long bone histology is relatively uniform and can be divided into two histotypes. Unexpectedly, both of these histotypes reveal abundant fibrolamellar bone throughout the cortex. This pushes the origin of fibrolamellar bone in Sauropterygia back from the Cretaceous to the early Middle Triassic (early Anisian). Histotype A is assigned to Cymatosaurus, a basal member of the Pistosauroidea, which includes the plesiosaurs as derived members. Histotype B is related to the pachypleurosaur Anarosaurus. Contrary to these new finds, the stratigraphically younger pachypleurosaur Neusticosaurus shows the plesiomorphic lamellar-zonal bone type and an incomplete endochondral ossification, like Nothosaurus.
Conclusions/Significance
Histological results hypothetically discussed in a phylogenetical context have a large impact on the current phylogenetic hypothesis of Sauropterygia, leaving the pachypleurosaurs polyphyletic. On the basis of histological data, Neusticosaurus would be related to Nothosaurus, whereas Anarosaurus would follow the pistosaur clade. Furthermore, the presence of fibrolamellar bone, which is accompanied with increased growth rates and presumably even with increased metabolic rates, already in Anarosaurus and Cymatosaurus can explain the success of the Pistosauroidea, the only sauropterygian group to survive into the Jurassic and give rise to the pelagic plesiosaur radiation.
Upper Triassic Sedimentology of Botswana
Bordy, E. M., Segwabe, T., and B. Makuke. 2010. Sedimentology of the Upper Triassic–Lower Jurassic (?) Mosolotsane Formation (Karoo Supergroup), Kalahari Karoo Basin, Botswana. Journal of African Earth Sciences 58:127–140.
Abstract - The Mosolotsane Formation (Lebung Group, Karoo Supergroup) in the Kalahari Karoo Basin of Botswana is a scantly exposed, terrestrial red bed succession which is lithologically correlated with the Late Triassic to Early Jurassic Molteno and Elliot Formations (Karoo Supergroup) in South Africa. New evidence derived from field observations and borehole data via sedimentary facies analysis allowed the assessment of the facies characteristics, distribution and thickness variation as well as palaeo-current directions and sediment composition, and resulted in the palaeo-environmental reconstruction of this poorly known unit. Our results show that the Mosolotsane Formation was deposited in a relatively low-sinuosity meandering river system that drained in a possibly semi-arid environment. Sandstone petrography revealed mainly quartz-rich arenites that were derived from a continental block provenance dominated by metamorphic and/or igneous rocks. Palaeo-flow measurements indicate reasonably strong, unidirectional current patterns with mean flow directions from southeast and east–southeast to northwest and west–northwest. Regional thickness and facies distributions as well as palaeo drainage indicators suggest that the main depocenter of the Mosolotsane Formation was in the central part of the Kalahari Karoo Basin. Separated from this main depocenter by a west northwest – east–southeast trending elevated area, an additional depocenter was situated in the north–northeast part of the basin and probably formed part of the Mid-Zambezi Karoo Basin. In addition, data also suggests that further northeast–southwest trending uplands probably existed in the northwest and east, the latter separating the main Kalahari Karoo depocenter from the Tuli Basin.
Abstract - The Mosolotsane Formation (Lebung Group, Karoo Supergroup) in the Kalahari Karoo Basin of Botswana is a scantly exposed, terrestrial red bed succession which is lithologically correlated with the Late Triassic to Early Jurassic Molteno and Elliot Formations (Karoo Supergroup) in South Africa. New evidence derived from field observations and borehole data via sedimentary facies analysis allowed the assessment of the facies characteristics, distribution and thickness variation as well as palaeo-current directions and sediment composition, and resulted in the palaeo-environmental reconstruction of this poorly known unit. Our results show that the Mosolotsane Formation was deposited in a relatively low-sinuosity meandering river system that drained in a possibly semi-arid environment. Sandstone petrography revealed mainly quartz-rich arenites that were derived from a continental block provenance dominated by metamorphic and/or igneous rocks. Palaeo-flow measurements indicate reasonably strong, unidirectional current patterns with mean flow directions from southeast and east–southeast to northwest and west–northwest. Regional thickness and facies distributions as well as palaeo drainage indicators suggest that the main depocenter of the Mosolotsane Formation was in the central part of the Kalahari Karoo Basin. Separated from this main depocenter by a west northwest – east–southeast trending elevated area, an additional depocenter was situated in the north–northeast part of the basin and probably formed part of the Mid-Zambezi Karoo Basin. In addition, data also suggests that further northeast–southwest trending uplands probably existed in the northwest and east, the latter separating the main Kalahari Karoo depocenter from the Tuli Basin.
New Information on the Triassic Dinosauriform Silesaurus opolensis
Piechowski, R., and J. Dzik. 2010. The axial skeleton of Silesaurus opolensis. Journal of Vertebrate Paleontology 30:1127 – 1141. DOI: 10.1080/02724634.2010.483547
Abstract - A recent find of an articulated skeleton of Silesaurus opolensis at its early Late Triassic type locality Krasiejów (Poland), with skull, neck, pectoral girdle, and thorax, supplemented by additional preparation of previously collected articulated specimens, enables complete restoration of the vertebral column and associated skeletal parts. Cervical ribs of Silesaurus, well preserved in their original disposition, are parallel to the neck and extend backward for a few vertebral lengths. There is a sudden change in their morphology behind the seventh vertebra, although otherwise the transition from the cervical to the dorsal vertebrae is very gradual. Parapophyses slowly migrate upward along the anterior margin of the centrum and leave the centrum at the sixth or seventh dorsal vertebra. Narrowing of the dorsal extremities of the neural spines of the fourth and neighboring vertebrae suggests the ability of this region of the vertebral column to bent upward. There is thus a disparity between the structural and functional neck-thorax transition. The presence of three sacrals firmly connected by their ribs with the ilia and the long tail of Silesaurus, providing a counterbalance to the weight of the body in front of the pelvis, suggests the ability for fast bipedal running. However, unusually long but gracile forelimbs of Silesaurus suggest that it represents a transition towards secondarily quadrupedal locomotion, characterizing most of the later herbivorous dinosaurs.
Abstract - A recent find of an articulated skeleton of Silesaurus opolensis at its early Late Triassic type locality Krasiejów (Poland), with skull, neck, pectoral girdle, and thorax, supplemented by additional preparation of previously collected articulated specimens, enables complete restoration of the vertebral column and associated skeletal parts. Cervical ribs of Silesaurus, well preserved in their original disposition, are parallel to the neck and extend backward for a few vertebral lengths. There is a sudden change in their morphology behind the seventh vertebra, although otherwise the transition from the cervical to the dorsal vertebrae is very gradual. Parapophyses slowly migrate upward along the anterior margin of the centrum and leave the centrum at the sixth or seventh dorsal vertebra. Narrowing of the dorsal extremities of the neural spines of the fourth and neighboring vertebrae suggests the ability of this region of the vertebral column to bent upward. There is thus a disparity between the structural and functional neck-thorax transition. The presence of three sacrals firmly connected by their ribs with the ilia and the long tail of Silesaurus, providing a counterbalance to the weight of the body in front of the pelvis, suggests the ability for fast bipedal running. However, unusually long but gracile forelimbs of Silesaurus suggest that it represents a transition towards secondarily quadrupedal locomotion, characterizing most of the later herbivorous dinosaurs.
New Information of the Cynodont Boreogomphodon jeffersoni from the Newark Supergroup
One of the bigger Triassic mysteries is why cynodonts are so common in the Newark Supergroup, while completely lacking in the presumably contemporaneous Chinle Formation (despite what you saw on 'Walking With Dinosaurs').
Sues, H.-D., and J. A. Hopson. 2010. Anatomy and phylogenetic relationships of Boreogomphodon jeffersoni (Cynodontia: Gomphodontia) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 30:1202 – 1220. DOI: 10.1080/02724634.2010.483545
Abstract - We present a detailed account on the skeletal structure of the traversodont cynodont Boreogomphodon jeffersoni on the basis of a considerable quantity of excellently preserved craniodental remains and several referred postcranial bones from the Tomahawk Creek Member of the Vinita Formation (Upper Triassic: Carnian) of the Richmond basin (Newark Supergroup) in eastern Virginia. The small size, proportionately short snout and mandible, low number of molariform postcanine teeth, and presence of up to three sectorial postcanines all indicate that most of the specimens recovered to date represent immature individuals. The superbly preserved dental material permits detailed inferences regarding tooth replacement and dental function during ontogeny. Boreogomphodon differs from other known traversodont cynodonts primarily in the possession of lower molariform postcanine teeth with three rather than two anterior cusps in all but the smallest specimens, zygomatic arches that are bowed laterally at about mid-length, and pronounced, irregular sculpturing on the dorsal surface of the snout. Plesiomorphic features of traversodont cynodonts retained by Boreogomphodon include the position of the paracanine fossa anterolingual to the upper canine as well as the presence of a distinct central cusp and a posterior cingulum on the upper molariform postcanines. Phylogenetic analysis suggests the existence of a clade comprising Boreogomphodon plus two other taxa (Arctotraversodon and Nanogomphodon) in the Northern Hemisphere that is the sister group to most other known Middle and Late Triassic traversodonts from Gondwana.
Sues, H.-D., and J. A. Hopson. 2010. Anatomy and phylogenetic relationships of Boreogomphodon jeffersoni (Cynodontia: Gomphodontia) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 30:1202 – 1220. DOI: 10.1080/02724634.2010.483545
Abstract - We present a detailed account on the skeletal structure of the traversodont cynodont Boreogomphodon jeffersoni on the basis of a considerable quantity of excellently preserved craniodental remains and several referred postcranial bones from the Tomahawk Creek Member of the Vinita Formation (Upper Triassic: Carnian) of the Richmond basin (Newark Supergroup) in eastern Virginia. The small size, proportionately short snout and mandible, low number of molariform postcanine teeth, and presence of up to three sectorial postcanines all indicate that most of the specimens recovered to date represent immature individuals. The superbly preserved dental material permits detailed inferences regarding tooth replacement and dental function during ontogeny. Boreogomphodon differs from other known traversodont cynodonts primarily in the possession of lower molariform postcanine teeth with three rather than two anterior cusps in all but the smallest specimens, zygomatic arches that are bowed laterally at about mid-length, and pronounced, irregular sculpturing on the dorsal surface of the snout. Plesiomorphic features of traversodont cynodonts retained by Boreogomphodon include the position of the paracanine fossa anterolingual to the upper canine as well as the presence of a distinct central cusp and a posterior cingulum on the upper molariform postcanines. Phylogenetic analysis suggests the existence of a clade comprising Boreogomphodon plus two other taxa (Arctotraversodon and Nanogomphodon) in the Northern Hemisphere that is the sister group to most other known Middle and Late Triassic traversodonts from Gondwana.
First Adult Record of Tanystropheus from China
Rieppel, O., Jiang, D.-Y., Fraser, N. C., Hao, W.-C., Motani, R., Sun, Y.-L., and Z.-Y., Sun. 2010. Tanystropheus cf. T. longobardicus from the early Late Triassic of Guizhou Province, southwestern China. Journal of Vertebrate Paleontology 30:1082 - 1089. DOI: 10.1080/02724634.2010.483548
Abstract - The protorosaur Tanystropheus longobardicus is well known from the Middle Triassic of alpine Europe. It has been described on the basis of a number of specimens that apparently range from juvenile to adult. The largest specimens have a total body length of approximately 3 m. Here we report on the first occurrence of a large tanystropheid from the Middle or early Late Triassic of southwestern China. The new specimen is indistinguishable from the largest specimens of T. longobardicus from Europe, although it lacks a skull. Both the Chinese specimen here described and the European specimens of T. longobardicus are characterized by 13 cervical vertebrae (not 12 as had previously been assumed). The new find, together with a recent specimen of Macrocnemus from Yunnan Province, highlight shared elements of the vertebrate fauna around the coastline of western and eastern Tethys during Middle to Late Triassic times.
Abstract - The protorosaur Tanystropheus longobardicus is well known from the Middle Triassic of alpine Europe. It has been described on the basis of a number of specimens that apparently range from juvenile to adult. The largest specimens have a total body length of approximately 3 m. Here we report on the first occurrence of a large tanystropheid from the Middle or early Late Triassic of southwestern China. The new specimen is indistinguishable from the largest specimens of T. longobardicus from Europe, although it lacks a skull. Both the Chinese specimen here described and the European specimens of T. longobardicus are characterized by 13 cervical vertebrae (not 12 as had previously been assumed). The new find, together with a recent specimen of Macrocnemus from Yunnan Province, highlight shared elements of the vertebrate fauna around the coastline of western and eastern Tethys during Middle to Late Triassic times.
Vacation and a New Issue of JVP
Things have been a little slow around here because I am at the end of a two week vacation. While I was away the latest issue of the Journal of Vertebrate Paleontology was released early online. This new issue contains a few new Triassic-relevant papers, some of which are listed here.
Hopefully I'll be back in the regular swing in a couple of days, after all there is another new aetosaur paper out.
Hopefully I'll be back in the regular swing in a couple of days, after all there is another new aetosaur paper out.
Early Triassic Age for the Base of the Timezgadiwine Formation of Morocco
Tourania, A., Benaouissa, N.,Gand, G., Bourquinc, S., Jalil, N.-E., Broutind,J., Battail, B., Germaine, D., Khaldounea, F., Soumaya, S., Steyere, J. S., and R. . 2010. Evidence of an Early Triassic age (Olenekian) in Argana Basin (High Atlas, Morocco)based on new chirotherioidtraces. Comptes Rendus Palevol, early online.
Abstract - New chirotherioid traces (Synaptichnium, Chirotherium, Brachychirotherium, Isochirotherium), are described in the Argana Basin (High Atlas of Morocco). Seeing that these ichnotaxa are frequent in the Triassic, their occurrence in outcrops formerly mapped as Permian (T2Member) has required detailed sedimentological and paleontological studies of the fossiliferous site.These studies clearly show that theichnite-bearing strata belong actually to the T3 Member of the “regional Triassic”, i.e. lower member of the Timezgadiwine Formation, the age of which was, in fact, unknown up to now.The description of these ichnospecies and their statistical comparison with those of other Early and Middle Triassic areas, suggestan Olenekian age for this footprint site, and consequently for the T3. The trackmakers were Archosauriformes, some of which had autopodia less evolved than those of Anisian age. With Lepidosauria,they lived in a flood plain close to alluvial-fans.
Abstract - New chirotherioid traces (Synaptichnium, Chirotherium, Brachychirotherium, Isochirotherium), are described in the Argana Basin (High Atlas of Morocco). Seeing that these ichnotaxa are frequent in the Triassic, their occurrence in outcrops formerly mapped as Permian (T2Member) has required detailed sedimentological and paleontological studies of the fossiliferous site.These studies clearly show that theichnite-bearing strata belong actually to the T3 Member of the “regional Triassic”, i.e. lower member of the Timezgadiwine Formation, the age of which was, in fact, unknown up to now.The description of these ichnospecies and their statistical comparison with those of other Early and Middle Triassic areas, suggestan Olenekian age for this footprint site, and consequently for the T3. The trackmakers were Archosauriformes, some of which had autopodia less evolved than those of Anisian age. With Lepidosauria,they lived in a flood plain close to alluvial-fans.
New Triassic Papers in Rivista Italiana di Palaeontolgia e Stratigrafia.
There are a trio of Triassic papers in the new issue of Rivista Italiana di Paleontologia e Stratigrafia.
Renesto, S. 2010. A new specimen of Nothosaurus from the latest Anisian (Middle Triassic) Besano Formation (Grenzbitumenzone) of Italy. Rivista Italiana di Paleontologia e Stratigrafia 116(2).
Abstract - A nearly complete but disarticulated skeleton of a small sized nothosaur is described. The specimen was collected in 2003 from an outcrop of the Besano Formation (Grenzbitumenzone of Swiss authors) of latest Anisian (Middle Triassic) age, in the Monte San Giorgio Area, northern Italy. The osteology of the postcranial skeleton supports the assignment to the genus Nothosaurus, and also excludes its belonging to Nothosaurus giganteus/Paranothosaurus amsleri already known from coeval localities of the Besano Formation in the Swiss part of the Monte San Giorgio area. Despite the lack of most of the skull, which contains diagnostic characters at the species level for Nothosaurus, the few preserved cranial elements suggest similarities with N. juvenilis which skull, and only known part, is also of comparable size. This specimen is particularly significant because it improves the knowledge of the osteology of N. juvenilis and because the second Nothosaurus species, smaller than N. giganteus/P. amsleri, suggests coexistence of sympatric species characterized by size and, probably, trophic differentiation within the genus Nothosaurus in the Monte San Giorgio area as occurred in the coeval Germanic Basin.
Tintori, A., Sun, Z.-Y., Lombardo, C., Jiang, D.-Y., Sun, Y.-L., and Hao, W.-C., 2010. A new basal neopterygian from the Middle Triassic of Luoping County (South China). Rivista Italiana di Paleontologia e Stratigrafia 116 (2).
Abstract - A new taxon belonging to Neopterygians is described, based on very nicely preserved specimens from the rich vertebrate levels recently discovered in Luoping County, Yunnan Province, South China. This new assemblage dates to Pelsonian (Anisian, Middle Triassic), about the same age of the Panxian Fauna from the nearby Guizhou Province. The Luoping Fauna, yielding this new taxon, is turning out to be one of the most important fish faunas of the whole Middle Triassic and the oldest evidence of the fish radiation of this time span. This new genus of basal neopterygian shows unique derived characters, especially for the almost naked body, with a single row of urodermals covering the body lobe in the tail and a row of very small and thin scales bearing the lateral line canal along the flank. Also in the axial skeleton the new taxon shows peculiar characters such as the neural spines perfectly aligned to each paired neural arches and abdominal ribs well developed. Concerning skull bones, no suborbitals have been detected.
Stockar, R., and Kustatscher, E. 2010. The Ladinian flora from the Cassina Beds (Meride Limestone, Monte San Giorgio, Switzerland): preliminary results. Rivista Italiana di Paleontologia e Stratigrafia 116 (2).
Abstract - A newly opened excavation in the Cassina beds of the Lower Meride Limestone (Monte San Giorgio UNESCO WHL, Canton Ticino, Southern Alps) has yielded a small collection of Ladinian plant fossils, together with vertebrate (mostly fish) and invertebrate remains. The flora contains at least five species; conifer remains assignable to the genera Elatocladus, Voltzia and ?Pelourdea are the most common elements. A new species, Elatocladus cassinae n. sp., is formally described. Co-occurring with the conifers are seed ferns (Ptilozamites) and a few putative cycadalean remains (?Taeniopteris). Among the identified genera, only Voltzia has previously been reported from Monte San Giorgio. The fossils presented in this paper indicate that a diversified flora thrived in the region during the Ladinian. Floral composition and preservation patterns are suggestive of a taphonomically-biased record and a relatively far-away source area.
Renesto, S. 2010. A new specimen of Nothosaurus from the latest Anisian (Middle Triassic) Besano Formation (Grenzbitumenzone) of Italy. Rivista Italiana di Paleontologia e Stratigrafia 116(2).
Abstract - A nearly complete but disarticulated skeleton of a small sized nothosaur is described. The specimen was collected in 2003 from an outcrop of the Besano Formation (Grenzbitumenzone of Swiss authors) of latest Anisian (Middle Triassic) age, in the Monte San Giorgio Area, northern Italy. The osteology of the postcranial skeleton supports the assignment to the genus Nothosaurus, and also excludes its belonging to Nothosaurus giganteus/Paranothosaurus amsleri already known from coeval localities of the Besano Formation in the Swiss part of the Monte San Giorgio area. Despite the lack of most of the skull, which contains diagnostic characters at the species level for Nothosaurus, the few preserved cranial elements suggest similarities with N. juvenilis which skull, and only known part, is also of comparable size. This specimen is particularly significant because it improves the knowledge of the osteology of N. juvenilis and because the second Nothosaurus species, smaller than N. giganteus/P. amsleri, suggests coexistence of sympatric species characterized by size and, probably, trophic differentiation within the genus Nothosaurus in the Monte San Giorgio area as occurred in the coeval Germanic Basin.
Tintori, A., Sun, Z.-Y., Lombardo, C., Jiang, D.-Y., Sun, Y.-L., and Hao, W.-C., 2010. A new basal neopterygian from the Middle Triassic of Luoping County (South China). Rivista Italiana di Paleontologia e Stratigrafia 116 (2).
Abstract - A new taxon belonging to Neopterygians is described, based on very nicely preserved specimens from the rich vertebrate levels recently discovered in Luoping County, Yunnan Province, South China. This new assemblage dates to Pelsonian (Anisian, Middle Triassic), about the same age of the Panxian Fauna from the nearby Guizhou Province. The Luoping Fauna, yielding this new taxon, is turning out to be one of the most important fish faunas of the whole Middle Triassic and the oldest evidence of the fish radiation of this time span. This new genus of basal neopterygian shows unique derived characters, especially for the almost naked body, with a single row of urodermals covering the body lobe in the tail and a row of very small and thin scales bearing the lateral line canal along the flank. Also in the axial skeleton the new taxon shows peculiar characters such as the neural spines perfectly aligned to each paired neural arches and abdominal ribs well developed. Concerning skull bones, no suborbitals have been detected.
Stockar, R., and Kustatscher, E. 2010. The Ladinian flora from the Cassina Beds (Meride Limestone, Monte San Giorgio, Switzerland): preliminary results. Rivista Italiana di Paleontologia e Stratigrafia 116 (2).
Abstract - A newly opened excavation in the Cassina beds of the Lower Meride Limestone (Monte San Giorgio UNESCO WHL, Canton Ticino, Southern Alps) has yielded a small collection of Ladinian plant fossils, together with vertebrate (mostly fish) and invertebrate remains. The flora contains at least five species; conifer remains assignable to the genera Elatocladus, Voltzia and ?Pelourdea are the most common elements. A new species, Elatocladus cassinae n. sp., is formally described. Co-occurring with the conifers are seed ferns (Ptilozamites) and a few putative cycadalean remains (?Taeniopteris). Among the identified genera, only Voltzia has previously been reported from Monte San Giorgio. The fossils presented in this paper indicate that a diversified flora thrived in the region during the Ladinian. Floral composition and preservation patterns are suggestive of a taphonomically-biased record and a relatively far-away source area.
The Basal Chinle Formation in Canyon DeChelly National Monument
The base of the Chinle Formation is well exposed in Canyon DeChelly National Monument just outside of Chinle, Arizona. Here the Chinle fills paleovalleys incised into Permian-age rocks, in this case the aeolian DeChelly Sandstone. The only trail accessible in the monument is the White House Trail, which leads down to abandoned ancient puebloan indian sites on the valley floor and in the canyon walls. Thus, this trail is very popular with visitors to the monument; however, I'll bet that the majority of them miss this feature, a 'u'-shaped valey carved in the DeChelly Sandstone and filled with gravels of the Shinarump Member of the Chinle Formation.
Something looks very wrong with the photo above. This is the contact between the Triassic Shinarump (on the left and the Permian DeChelly (on the right). The contact between the two is vertical along the sides of the paleovalley. This is relatively flat lying strata. Pretty rare to see this.
One very cool aspect of a vertical contact (and unconformity) like this is that it is pretty obvious that the older unit (in this case the cross bedded sandstone) must have been fully lithified before the younger unit was deposited. In this case the was a slot canyon in the DeChelly that was filled in in the Late Triassic. Actually Triassic topography is visible here. You can stand on the end and look inot where the canyon would have been about 220 million years ago.
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| The capping darker sandstone is the Triassic Shinarump Member of the Chinle Formation, and the buff sandstone is the Permian DeChelly. In the direct center of the photo is a dark patch in the buff. This is a 50 foot deep gravel filled paleovalley cut into the DeChelly. You can also trace it to the left and right in the photo. Note the figure on the trail just to the left of the valley, and a figure under the tree just to the right. |
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One very cool aspect of a vertical contact (and unconformity) like this is that it is pretty obvious that the older unit (in this case the cross bedded sandstone) must have been fully lithified before the younger unit was deposited. In this case the was a slot canyon in the DeChelly that was filled in in the Late Triassic. Actually Triassic topography is visible here. You can stand on the end and look inot where the canyon would have been about 220 million years ago.
The Rock Point Member of the Chinle Formation in the Chinle Valley
On of the great things about this weekend was seeing the entire Chinle Formation type section. H. E. Gregory divided the Chinle into four divisions A, B, C, D; which since that time have been given formal names. A = Rock Point Member, B = Owl Rock Member, C = Petrified Forest Member (which in our modern usage also includes the Blue Mesa and Sonsela Members), and D = the lower red member (or Bluewater Creek). We were able to see all of these divisions as well as the underlying Shinarump Member (which Gregory did not include in hs Chinle). We spent 4th of July evening looking at the Rock Point Member:
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| The type section of the Rock Point Member is the slope forming base of Little Round Rock. |
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| Rock Point Member on the side of Round Rock. |
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| Close-up of Rock Point strata on Round Rock. |
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| Jeff Martz examining the Rock Point Member at Round Rock. |
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| Photo from a little more than half way up the Rock Point section on Round Rock. Valley below is the Owl Rock Member. Note our vehicle to the bottom left of the photo. These exposures are really high up. |
The Owl Rock Member of the Chinle Formation in the Chinle Valley
The Owl Rock Member of the Chinle Formation is widely exposed in the Four Corners area of the western United States. The unit is characterized by its variegated color scheme and prominent carbonate lenses. In the Chinle Valley the Owl Rock overlies the Petrified Forest Member and is overlain by the Rock Point Member.
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| Owl Rock Member (top) and the Petrified Forest Member (bottom) at Round Top Ridge. |
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| Prominent carbonate lenses in the Owl Rock Member at Round Top Ridge. |
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| Thick beds of carbonate in the very top of the Owl Rock Member at Round Rock. |
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| Close-up of fallen blocks of the upper carbonate beds at Round Rock. |
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| Contact between the top of the Owl Rock Member and the overlying Rock Point Member at Round Rock. |
The Sonsela Member of the Chinle Formation in the Chinle Valley
This is how I spent my fourth of July, checking out Sonsela Member outcrops throughout the Chinle Valley:
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| Sonsela Member outcrops. The Chuska Mountains in the background. |
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| In-situ petrified log in the upper portion of the member. |
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| Another log at the same horizon. Round Top Ridge (left) and Round Rock (right) in background, the Petrified Forest, Owl Rock, and Rock Point Members of the Chinle, and the Wingate Sandstone. |
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| The Sonsela Member is predominantly a sandstone interval. |
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| In-situ petrified log on cliff top. |
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| View of a portion of the Chinle Valley from ledge south of Round Rock at the end of the day. The Sonsela Member is the grey swath across the upper center of the photo, the red is the Petrified Forest Member. |
The Many Farms Desmatosuchus Quarry
As part of our weekend in the Chinle Valley, Jeff, Steve, and I revisted the quarry near Many Farms Lake where the Museum of Northern Arizona collected a fairly complete skeleton of the aetosaur Desmatosuchus spurensis in 1999. This specimen was the basis for my Masters thesis (Parker, 2003) and a subsequent paper describing this specimen and revising the genus (Parker, 2008). I spent a lot of time in this place but had not visited since 2003. The excavation pit is still visible, but is reclaiming nicely. I took a few photos of the site and the surrounding area:
REFERENCES
Parker, W. G. 2003. Description of a new specimen of Desmatosuchus haplocerus from the Late Triassic of Northern Arizona. Unpublished M. S. thesis, Northern Arizona University, Flagstaff, 315 p.
Parker, W. G. 2008. Description of new material of the aetosaur Desmatosuchus spurensis (Archosauria: Suchia) from the Chinle Formation of Arizona and a revision of the genus Desmatosuchus. PaleoBios 281–40.
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| Jeff Martz examining ripple laminated sandstone near the quarry |
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| Many Farms Desmatosuchus Quarry |
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| Slightly different view of the quarry outcrop |
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| Looking north from the quarry at the local Chinle units. Blue Mesa Member in foreground, ridge is distance capped by Sonsela Member. |
REFERENCES
Parker, W. G. 2003. Description of a new specimen of Desmatosuchus haplocerus from the Late Triassic of Northern Arizona. Unpublished M. S. thesis, Northern Arizona University, Flagstaff, 315 p.
Parker, W. G. 2008. Description of new material of the aetosaur Desmatosuchus spurensis (Archosauria: Suchia) from the Chinle Formation of Arizona and a revision of the genus Desmatosuchus. PaleoBios 281–40.
The Shinarump Member (Chinle Formation) Near Many Farms Arizona
The are some pretty spectacular exposures of the base of the Chinle Formation in the Chinle Valley in Northeastern Arizona. Jeff Martz, our friend Steve Clarke, and I spent the day yesterday exploring these outcrops and as Jeff often puts it "figuring shit out". Here are a few photos from yesterdays work:
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| Shinarump Sandstone forming slot canyon east of Many Farms Lake |
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| Close-up of canyon walls |
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| South rim of Tezinie Canyon, east of Many Farms. |
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| Close-up view of North rim of Tezinie Canyon |
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.
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| (From Gregory 1917) |
REFERENCE
Gregory, H. E. 1917. Geology of Navajo Country. United States Geological Survey Professional Paper 93, p. 161.
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