Museum of Northern Arizona geologist and Distinguished Fellow William J. Breed passed away in Flagstaff Arizona on January 22, 2013 after a long and accomplished career predominantly studying the geology and paleontology of the southwestern U.S. He is also well known for his work with Edwin (Ned) Colbert and Jim Jensen in Antarctica in 1969 when they discovered fossil evidencesupporting the idea of Continental Drift. Among many honors Breed was also a Fellow of the Geological Society of America.
http://azdailysun.com/news/local/obituaries/william-breed-renowned-mna-geologist-dies-in-flagstaff/article_41857e06-1387-53d0-bf6f-f3c469222f65.html
New Spider from the Upper Triassic of Italy
Regardless of the higher taxonomic uncertainty, the Triassic record for spiders is poor and just got a little bit better.
Dalla Vecchia, F. M., and P. A. Selden. 2013. A Triassic spider from Italy. Acta Palaeontologica Polonica forthcoming paper. http://dx.doi.org/10.4202/app.2011.0132
Abstract - A new fossil spider from the Triassic (Norian) Dolomia di Forni Formation of Friuli, Italy, is described as Friularachne rigoi gen. et sp. nov. This find brings the number of known Triassic spider species to four. The specimen is an adult male, and consideration of various features, including enlarged, porrect chelicerae, subequal leg length, and presence of a dorsal scutum, point to its identity as a possible member of the mygalomorph superfamily Atypoidea. If correct, this would extend the geological record of the superfamily some 98–115 Ma from the late Early Cretaceous (?Albian, c. 100–112 Ma) to the late middle–early late Norian (c. 210–215Ma).
Dalla Vecchia, F. M., and P. A. Selden. 2013. A Triassic spider from Italy. Acta Palaeontologica Polonica forthcoming paper. http://dx.doi.org/10.4202/app.2011.0132
Abstract - A new fossil spider from the Triassic (Norian) Dolomia di Forni Formation of Friuli, Italy, is described as Friularachne rigoi gen. et sp. nov. This find brings the number of known Triassic spider species to four. The specimen is an adult male, and consideration of various features, including enlarged, porrect chelicerae, subequal leg length, and presence of a dorsal scutum, point to its identity as a possible member of the mygalomorph superfamily Atypoidea. If correct, this would extend the geological record of the superfamily some 98–115 Ma from the late Early Cretaceous (?Albian, c. 100–112 Ma) to the late middle–early late Norian (c. 210–215Ma).
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| Left: Drawing of the fossil of Friularachne rigoi (from Dalla Vecchia & Selden, 2013). Right: Reconstruction of Friularachne rigoi; Credits Lukas Panzarin. |
The First Published Geological Map of Petrified Forest National Park
Today marks a momentious day in the geological research history of Petrified Forest National Park in Arizona. 35 years ago work began on a draft geological map of the park. Unfortunately the draft, completed in the early 1980s, was never finalized although it served as the basic guide for work through the early 2000s. Around this time the need to update the map was considered and some minor revisions were accomplished. In 2005 the National Park Service contracted with Northern Arizona University to finally complete the map; however, the work was stalled when it was realized that the current stratigraphic schemes used by the park (proposed in 2002 and 2003) could not recreated by the mapping and therefore something was wrong.
In 2008, Jeff Martz and I decided to tackle both the stratigraphic problems as well as revising the park map in the progress. As we discussed in our 2010 stratigraphic revision paper (available for free here), mapping is a crucial part of solving stratigraphic problems, because it involves detailed walking out of beds and really tests your proposed correlations. We walked kilometer after kilometer that first summer, arguing the whole time, but really working out the correlations. Subsequently Jeff took the lead on completing the mapping and after literally wearing his boots down to 'sandals' (they proudly hang in my office today) completed this work in 2010. His map was then painstakingly digitized and finalized by Lisa Skinner at NAU. The report includes some of Jeff's amazing artwork that he is developing a reputation for in the scientific realm. I especially find the cross-section to be particularly telling and useful for individuals to place themselves in the stratigraphy as they progress through the park.
The finished product is now available on-line courtesy of our partners at the Arizona Geological Survey as part of their Contributed Map series, and the map and associated report is available as a free download from here. I'd like to thank Arizona State Geologist Lee Allison for allowing the map to be distributed as part of their publication series and to Mike Conway for putting up with all of our edits through the whole process. I think that Jeff and Lisa in particular did an amazing job finalizing the product and finally after 35 years there is an official map of the park. Now we just need to add the park expansion areas added in 2007 to the present.....
In 2008, Jeff Martz and I decided to tackle both the stratigraphic problems as well as revising the park map in the progress. As we discussed in our 2010 stratigraphic revision paper (available for free here), mapping is a crucial part of solving stratigraphic problems, because it involves detailed walking out of beds and really tests your proposed correlations. We walked kilometer after kilometer that first summer, arguing the whole time, but really working out the correlations. Subsequently Jeff took the lead on completing the mapping and after literally wearing his boots down to 'sandals' (they proudly hang in my office today) completed this work in 2010. His map was then painstakingly digitized and finalized by Lisa Skinner at NAU. The report includes some of Jeff's amazing artwork that he is developing a reputation for in the scientific realm. I especially find the cross-section to be particularly telling and useful for individuals to place themselves in the stratigraphy as they progress through the park.
The finished product is now available on-line courtesy of our partners at the Arizona Geological Survey as part of their Contributed Map series, and the map and associated report is available as a free download from here. I'd like to thank Arizona State Geologist Lee Allison for allowing the map to be distributed as part of their publication series and to Mike Conway for putting up with all of our edits through the whole process. I think that Jeff and Lisa in particular did an amazing job finalizing the product and finally after 35 years there is an official map of the park. Now we just need to add the park expansion areas added in 2007 to the present.....
Two New Temnospondyl Papers - Phylogeny of Major Clades and Suction Feeding in Gerrothorax
Schoch, R. R. 2013. The evolution of major temnospondyl clades: an inclusive phylogenetic analysis. Journal of Systematic Palaeontology DOI:10.1080/14772019.2012.699006http://www.tandfonline.com/doi/full/10.1080/14772019.2012.699006
Abstract - Phylogenetic analysis of a large dataset (72 taxa, 212 characters) focuses on the in-group relationships of temnospondyls, the largest lower tetrapod clade. Representatives of all clades and grades were considered, spanning the entire stratigraphical range of temnospondyls from the Early Carboniferous through to the Early Cretaceous. Several major groups are defined phylogenetically (node or branch-based) rather than by apomorphies. The following groups were unequivocally found to be monophyletic: Edopoidea (node), Dvinosauria (stem, excl. Brachyopidae), Dissorophoidea (node), Eryopidae (stem), and Stereospondyli (node). The latter encompass three well-defined, branch-based taxa: Rhinesuchidae, Trematosauria and Capitosauria. Trematosauria (stem) contain Trematosauroidea (node), which includes the classic trematosaurids, metoposaurids, and possibly part of the rhytidosteids (Peltostega) but their in-group relationships remain unsettled; most other short-snouted stereospondyls (chigutisaurids, brachyopids, Laidleria and the plagiosaurids) are probably monophyletic and likely nest in some form with trematosauroids. Capitosauria (stem) include the Capitosauroidea (node) spanned by Parotosuchus and Mastodonsaurus, with the successive stem taxa Edingerella, Benthosuchus, Wetlugasaurus and Watsonisuchus. In all variant analyses, edopoids form the basalmost temnospondyl clade, followed by a potential clade (or grade) of small terrestrial taxa containing Balanerpeton and Dendrerpeton (‘Dendrerpetontidae’). All taxa higher than Edopoidea are suggested to form the monophyletic stem taxon Eutemnospondyli, tax. nov. The remainder of Temnospondyli fall into four robust and undisputed clades: (1) Dvinosauria; (2) Zatracheidae plus Dissorophoidea; (3) Eryopidae; and (4) Stereospondyli. These taxa are together referred to as Rhachitomi (node). Eryopidae and Stereospondylomorpha are probably monophyletic, here referred to as Eryopiformes (tax. nov.). The position of Dissorophoidea + Zatracheidae is still ambiguous; it may either form the sister taxon of Dvinosauria, or nest between Dvinosauria and Eryopiformes, whereas there is no support for Euskelia (Dissorophoidea + Eryopidae) after basal taxa of each clade are better understood.
Witzmann, F. and R. R. Schoch. 2012. Reconstruction of cranial and hyobranchial muscles in the Triassic temnospondyl Gerrothorax provides evidence for akinetic suction feeding. Journal of Morphology DOI: 10.1002/jmor.20113 http://onlinelibrary.wiley.com/doi/10.1002/jmor.20113/abstract
Abstract - The cranial and hyobranchial muscles of the Triassic temnospondyl Gerrothorax have been reconstructed based on direct evidence (spatial limitations, ossified muscle insertion sites on skull, mandible, and hyobranchium) and on phylogenetic reasoning (with extant basal actinopterygians and caudates as bracketing taxa). The skeletal and soft-anatomical data allow the reconstruction of the feeding strike of this bottom-dwelling, aquatic temnospondyl. The orientation of the muscle scars on the postglenoid area of the mandible indicates that the depressor mandibulae was indeed used for lowering the mandible and not to raise the skull as supposed previously and implies that the skull including the mandible must have been lifted off the ground during prey capture. It can thus be assumed that Gerrothorax raised the head toward the prey with the jaws still closed. Analogous to the bracketing taxa, subsequent mouth opening was caused by action of the strong epaxial muscles (further elevation of the head) and the depressor mandibulae and rectus cervicis (lowering of the mandible). During mouth opening, the action of the rectus cervicis muscle also rotated the hyobranchial apparatus ventrally and caudally, thus expanding the buccal cavity and causing the inflow of water with the prey through the mouth opening. The strongly developed depressor mandibulae and rectus cervicis, and the well ossified, large quadrate-articular joint suggest that this action occurred rapidly and that powerful suction was generated. Also, the jaw adductors were well developed and enabled a rapid mouth closure. In contrast to extant caudate larvae and most extant actinopterygians (teleosts), no cranial kinesis was possible in the Gerrothorax skull, and therefore suction feeding was not as elaborate as in these extant forms. This reconstruction may guide future studies of feeding in extinct aquatic tetrapods with ossified hyobranchial apparatus.
Abstract - Phylogenetic analysis of a large dataset (72 taxa, 212 characters) focuses on the in-group relationships of temnospondyls, the largest lower tetrapod clade. Representatives of all clades and grades were considered, spanning the entire stratigraphical range of temnospondyls from the Early Carboniferous through to the Early Cretaceous. Several major groups are defined phylogenetically (node or branch-based) rather than by apomorphies. The following groups were unequivocally found to be monophyletic: Edopoidea (node), Dvinosauria (stem, excl. Brachyopidae), Dissorophoidea (node), Eryopidae (stem), and Stereospondyli (node). The latter encompass three well-defined, branch-based taxa: Rhinesuchidae, Trematosauria and Capitosauria. Trematosauria (stem) contain Trematosauroidea (node), which includes the classic trematosaurids, metoposaurids, and possibly part of the rhytidosteids (Peltostega) but their in-group relationships remain unsettled; most other short-snouted stereospondyls (chigutisaurids, brachyopids, Laidleria and the plagiosaurids) are probably monophyletic and likely nest in some form with trematosauroids. Capitosauria (stem) include the Capitosauroidea (node) spanned by Parotosuchus and Mastodonsaurus, with the successive stem taxa Edingerella, Benthosuchus, Wetlugasaurus and Watsonisuchus. In all variant analyses, edopoids form the basalmost temnospondyl clade, followed by a potential clade (or grade) of small terrestrial taxa containing Balanerpeton and Dendrerpeton (‘Dendrerpetontidae’). All taxa higher than Edopoidea are suggested to form the monophyletic stem taxon Eutemnospondyli, tax. nov. The remainder of Temnospondyli fall into four robust and undisputed clades: (1) Dvinosauria; (2) Zatracheidae plus Dissorophoidea; (3) Eryopidae; and (4) Stereospondyli. These taxa are together referred to as Rhachitomi (node). Eryopidae and Stereospondylomorpha are probably monophyletic, here referred to as Eryopiformes (tax. nov.). The position of Dissorophoidea + Zatracheidae is still ambiguous; it may either form the sister taxon of Dvinosauria, or nest between Dvinosauria and Eryopiformes, whereas there is no support for Euskelia (Dissorophoidea + Eryopidae) after basal taxa of each clade are better understood.
Witzmann, F. and R. R. Schoch. 2012. Reconstruction of cranial and hyobranchial muscles in the Triassic temnospondyl Gerrothorax provides evidence for akinetic suction feeding. Journal of Morphology DOI: 10.1002/jmor.20113 http://onlinelibrary.wiley.com/doi/10.1002/jmor.20113/abstract
Abstract - The cranial and hyobranchial muscles of the Triassic temnospondyl Gerrothorax have been reconstructed based on direct evidence (spatial limitations, ossified muscle insertion sites on skull, mandible, and hyobranchium) and on phylogenetic reasoning (with extant basal actinopterygians and caudates as bracketing taxa). The skeletal and soft-anatomical data allow the reconstruction of the feeding strike of this bottom-dwelling, aquatic temnospondyl. The orientation of the muscle scars on the postglenoid area of the mandible indicates that the depressor mandibulae was indeed used for lowering the mandible and not to raise the skull as supposed previously and implies that the skull including the mandible must have been lifted off the ground during prey capture. It can thus be assumed that Gerrothorax raised the head toward the prey with the jaws still closed. Analogous to the bracketing taxa, subsequent mouth opening was caused by action of the strong epaxial muscles (further elevation of the head) and the depressor mandibulae and rectus cervicis (lowering of the mandible). During mouth opening, the action of the rectus cervicis muscle also rotated the hyobranchial apparatus ventrally and caudally, thus expanding the buccal cavity and causing the inflow of water with the prey through the mouth opening. The strongly developed depressor mandibulae and rectus cervicis, and the well ossified, large quadrate-articular joint suggest that this action occurred rapidly and that powerful suction was generated. Also, the jaw adductors were well developed and enabled a rapid mouth closure. In contrast to extant caudate larvae and most extant actinopterygians (teleosts), no cranial kinesis was possible in the Gerrothorax skull, and therefore suction feeding was not as elaborate as in these extant forms. This reconstruction may guide future studies of feeding in extinct aquatic tetrapods with ossified hyobranchial apparatus.
Comparing the Tooth Enamel Microstructure of the Pseudosuchian Revueltosaurus and the Proposed Triassic Ornithischian Krzyzanowskisaurus
This is a new paper testing the relationships between the pseudosuchian Revueltosaurus callenderi and the hypothesized ornithischian Krzyzanowskisaurus hunti (originally Revueltosaurus hunti) utilizing tooth enamel microstructure. The study finds that the tooth enamel structure of these two taxa share many characters not found in other taxa and thus they are probably closely related. The authors advocate that generic distinction should be maintained until the skeletal remains of K. hunti are discovered. However, the teeth of K. hunti were recovered from a microvertebrate deposit in the Blue Mesa Member of the Chinle Formation near St. Johns Arizona. As mentioned by Parker et al (2005) and Irmis et al. (2007) the same deposit included an autapomorphic squamosal of Revueltosaurus as well as numerous osteoderms also referable to the taxon. Thus the assemblage possibly contains Revueltosaurus hunti or Revueltosaurus as well as a second taxon with Revueltosaurus-like teeth called Krzyzanowskisaurus. Heckert and Miller-Camp argue that this could be circumstantial given the purported lack of element association; however, no evidence exists either that they weren't originally found in association. There is simply just drawers of microvertebrate material from the same quarry. I and my colleagues have just maintained that the former is more parsimonious (Revueltosaurus hunti) and the shared characteristics of the teeth revealed by this study seem to support that hypothesis. In any case there still is no strong evidence for an ornithischian dinosaur affinity for K. hunti.
Heckert, A. B., and J. A. Miller-Camp. 2013. Tooth enamel microstructure of Revueltosaurus and Krzyzanowskisaurus (Reptilia:Archosauria) from the Upper Triassic Chinle Group, USA: Implications for function, growth, and phylogeny. Palaeontologia Electronica Vol. 16, Issue 1; 1A,23p; palaeo-electronica.org/content/2013/344-revueltosaurus-tooth-enamel
Abstract - Tooth enamel microstructure can carry significant phylogenetic, ontogenetic, and functional information within amniotes. Here we provide the first descriptions of the tooth enamel microstructure of two Late Triassic taxa, the crurotarsan Revueltosaurus callenderi Hunt and the putative ornithischian Krzyzanowskisaurus hunti (Heckert), which some consider closely related. To test the hypotheses that enamel thickness corresponds to function and/or phylogeny we analyzed the enamel of each at various scales, measuring enamel thickness and examining microstructural features throughout both longitudinal and cross-sectional thickness using previously established techniques to facilitate comparisons. Both taxa possess thick (up to ~150 µm) enamel for their size (< 20 mm crown height). Enamel in R. callenderi ranged from ~5-152 µm across a premaxillary tooth in longitudinal section, and ~42-92 µm in a maxillary/dentary tooth transverse section. K. hunti enamel thickness was ~18-155 µm longitudinally and ~29-75 µm transversely. Both also had well-developed basal unit layers (BUL) and weakly developed columnar microstructure. Well-developed lines of incremental growth (LIG) are present in both taxa, through which the columnar enamel grades into parallel crystallite enamel. Their enamel microstructure is therefore grossly similar to that of several ornithischian taxa, especially ankylosaurs, with which they are strongly convergent, and also compares well to rauisuchids and tyrannosaurids. The relatively unique combination of microstructural characteristics in the schmelzmuster of R. callenderi and K. hunti supports the hypothesis that they are closely related, but does not conclusively preclude a different taxonomic placement for K. hunti so we retain its separate generic designation.
Heckert, A. B., and J. A. Miller-Camp. 2013. Tooth enamel microstructure of Revueltosaurus and Krzyzanowskisaurus (Reptilia:Archosauria) from the Upper Triassic Chinle Group, USA: Implications for function, growth, and phylogeny. Palaeontologia Electronica Vol. 16, Issue 1; 1A,23p; palaeo-electronica.org/content/2013/344-revueltosaurus-tooth-enamel
Abstract - Tooth enamel microstructure can carry significant phylogenetic, ontogenetic, and functional information within amniotes. Here we provide the first descriptions of the tooth enamel microstructure of two Late Triassic taxa, the crurotarsan Revueltosaurus callenderi Hunt and the putative ornithischian Krzyzanowskisaurus hunti (Heckert), which some consider closely related. To test the hypotheses that enamel thickness corresponds to function and/or phylogeny we analyzed the enamel of each at various scales, measuring enamel thickness and examining microstructural features throughout both longitudinal and cross-sectional thickness using previously established techniques to facilitate comparisons. Both taxa possess thick (up to ~150 µm) enamel for their size (< 20 mm crown height). Enamel in R. callenderi ranged from ~5-152 µm across a premaxillary tooth in longitudinal section, and ~42-92 µm in a maxillary/dentary tooth transverse section. K. hunti enamel thickness was ~18-155 µm longitudinally and ~29-75 µm transversely. Both also had well-developed basal unit layers (BUL) and weakly developed columnar microstructure. Well-developed lines of incremental growth (LIG) are present in both taxa, through which the columnar enamel grades into parallel crystallite enamel. Their enamel microstructure is therefore grossly similar to that of several ornithischian taxa, especially ankylosaurs, with which they are strongly convergent, and also compares well to rauisuchids and tyrannosaurids. The relatively unique combination of microstructural characteristics in the schmelzmuster of R. callenderi and K. hunti supports the hypothesis that they are closely related, but does not conclusively preclude a different taxonomic placement for K. hunti so we retain its separate generic designation.
Macropredatory ichthyosaur, Thalattoarchon saurophagis, from the Middle Triassic of Nevada
New in PNAS. I assume by terrestrial apex predators in the Carnian they are thinking about phytosaurs and/or large rauisuchids as they (p. 3) state that "Although large predators such as the rauisuchians Erythrosuchus and Ticinosuchus appear in the terrestrial rock record in the Anisian (Nesbitt, 2011), it has been suggested that full recovery on land was not reached until the Late Triassic, 30 My after the P/T extinction (Sahney & Benton, 2008)" [full references and edit added]. Unfortunately this ignores a good bit of new evidence published since 2008 that has changed our understanding of the timing of recovery on land (Xilousuchus, Nyassasaurus). However, I still think the existance of giant (almost 9 meter long) ichthyosaurs is incredible. More than a decade ago I got to see the 21 meter long holotype specimen of Shastasaurus sikanniensis (Late Triassic, British Columbia) when it was being prepared at the Royal Tyrell Museum. To get a photograph of just the rear portion of the skull I had to stand at the top of a fully extended ladder. I used a meter stick for the scale bar! This new specimen is not quite 9 meters in length, but is still huge as the average is 2-4 meters, and it has 12 cm long teeth.
Fröbisch, N. B., Fröbisch, J., Sander, P. M., Schmitz, L., and O. Rieppel. 2013. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks. PNAS Early Edition, January 7, 2013. doi:10.1073/pnas.1216750110
Abstract - The biotic recovery from Earth’s most severe extinction event at the Permian-Triassic boundary largely reestablished the preextinction structure of marine trophic networks, with marine reptiles assuming the predator roles. However, the highest trophic level of today's marine ecosystems, i.e., macropredatory tetrapods that forage on prey of similar size to their own, was thus far lacking in the Paleozoic and early Mesozoic. Here we report a top-tier tetrapod predator, a very large (>8.6 m) ichthyosaur from the early Middle Triassic (244 Ma), of Nevada. This ichthyosaur had a massive skull and large labiolingually flattened teeth with two cutting edges indicative of a macropredatory feeding style. Its presence documents the rapid evolution of modern marine ecosystems in the Triassic where the same level of complexity as observed in today’s marine ecosystems is reached within 8 My after the Permian-Triassic mass extinction and within 4 My of the time reptiles first invaded the sea. This find also indicates that the biotic recovery in the marine realm may have occurred faster compared with terrestrial ecosystems, where the first apex predators may not have evolved before the Carnian.
Fröbisch, N. B., Fröbisch, J., Sander, P. M., Schmitz, L., and O. Rieppel. 2013. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks. PNAS Early Edition, January 7, 2013. doi:10.1073/pnas.1216750110
Abstract - The biotic recovery from Earth’s most severe extinction event at the Permian-Triassic boundary largely reestablished the preextinction structure of marine trophic networks, with marine reptiles assuming the predator roles. However, the highest trophic level of today's marine ecosystems, i.e., macropredatory tetrapods that forage on prey of similar size to their own, was thus far lacking in the Paleozoic and early Mesozoic. Here we report a top-tier tetrapod predator, a very large (>8.6 m) ichthyosaur from the early Middle Triassic (244 Ma), of Nevada. This ichthyosaur had a massive skull and large labiolingually flattened teeth with two cutting edges indicative of a macropredatory feeding style. Its presence documents the rapid evolution of modern marine ecosystems in the Triassic where the same level of complexity as observed in today’s marine ecosystems is reached within 8 My after the Permian-Triassic mass extinction and within 4 My of the time reptiles first invaded the sea. This find also indicates that the biotic recovery in the marine realm may have occurred faster compared with terrestrial ecosystems, where the first apex predators may not have evolved before the Carnian.
New Study on the Late Triassic Pollen Record at the Petrified Forest National Park, Arizona, USA
This is a new study of the palynology of the Chinle Formation of Petrified Forest National Park that fills in a previous sampling gap caused by reevaluation of the local stratigraphy. The study finds three pollen assembalge biozones that correspond to the two zones previously recovered by Litwin et al. (1991). Two main points of the paper are: 1) these faunal zones no longer pertain to the Carnian/Norian boundary as recent dating of the Chinle Formation in conjunction with a recalibration of the Late Triassic timescale demonstrates that the Chinle Formation is Norian-Rhaetian in age (Irmis et al., 2011; Ramezani et al., 2011); 2) the floral turnover roughly corresponds stratigraphically with the faunal turnover precisely located in the park by Parker and Martz (2011). Potential causal mechanisms remain under investigation.
Abstract - Recent paleontological investigations and lithostratigraphic revisions reveal a marked biotic turnover zone within the continental deposits of the Sonsela member of the Chinle Formation (Late Triassic, Norian) at Petrified Forest National Park, USA. Within the Sonsela member we found three pollen assemblage biozones: Zone II (90.5–94 m above the Mesa Redondo member) contains a relatively diverse palynological assemblage, with a mix of pteridosperms, voltzialean and some Mesozoic conifers. Following a 2.3 m hiatus, Zone IIIa (96–97.5 m) is characterized by a decrease in pteridosperms and Mesozoic conifers and a drop in voltzialean conifer diversity. The alleged voltzialean conifer pollen Klausipollenites gouldii was dominant in this part of the assemblage and a significant rise in spores and cycad pollen was also evident. In Zone IIIb (97.5–98.5 m) diversity increases and several taxa, which were absent in Zone IIIa reappear, although K. gouldii remained the most abundant taxon. The transition between the palynological assemblages Zones II and IIIa coincide approximately (within a ~2.5 m interval) with a documented faunal turnover. The floristic assemblages suggest that the climate of the south-western United States during the Norian was most likely semi-arid and highly seasonal, despite being located at tropical latitudes, with aridification occurring towards the end-Triassic as the continent drifted northwards and global volcanism increased. The gymnosperm dominated palynofloral assemblage as opposed to the fern- and horsetail-dominated macrofossil record of the Sonsela member of the Chinle Formation, conforms to a semi-arid upland environment alternated by riparian, swampy lowland.
REFERENCES:
Irmis, R. B., Mundil, R., Martz, J. W., and W.
G. Parker. 2011. High-precision U-Pb zircon ages from the Chinle Formation of
New Mexico, USA: Implications for Late Triassic vertebrate biostratigraphy and
the rise of dinosaurs. Earth and Planetary Science Letters 309:258-267.
Litwin, R. J., Traverse, A., and S.R. Ash. 1991. Preliminary palynological zonation of the
Chinle Formation, southwestern U.S.A. U.S.A.
Parker, W. G., and J. W. Martz. 2011. Constraining
the stratigraphic position of the Late Triassic (Norian) Adamanian Revueltian
faunal transition in the Chinle Formation of Petrified Forest National Park,
Arizona. Earth and Environmental Transactions of the Royal Society of Edinburgh
101:231-260.
Ramezani, J., Hoke, G. D., Fastovsky, D.E.,
Bowring, S. A., Therrien, F., Dworkin, S. I., Atchley, S. C. and L. C. Nordt.
2011. High precision U-Pb zircon geochronology of the Late Triassic Chinle
Formation, Petrified Forest National Park (Arizona): Temporal constraints on
the early evolution of dinosaurs. Geological Society of America Bulletin
123:2142-2159.
Diverse Tetrapod Track Assemblages from the Late Triassic of Morocco
Lagnaoui, A. Klein, H., Voigt, S., Hminna, A., Saber, H., Schneider, J. W., and R. Werneburg. 2012. Late Triassic Tetrapod-Dominated Ichnoassemblages from the Argana Basin (Western High Atlas, Morocco). Ichnos 19:238-253.
DOI:
10.1080/10420940.2012.718014
Abstract - Diverse tetrapod track assemblages with Scoyenia invertebrate traces were discovered in the Triassic Timezgadiouine and Bigoudine formations of the Argana Basin (Western High Atlas, Morocco). The ichnofossils occur in alluvial plain sandstones and mudstones of the Irohalène Member (T5) and Tadart Ouadou Member (T6) considered Carnian-Norian in age by vertebrate remains and palynomorphs. Tetrapod footprints are assigned to Apatopus, Atreipus-Grallator,Eubrontes isp., Parachirotherium, cf. Parachirotherium postchirotherioides, Rhynchosauroides ispp., and Synaptichnium isp. They can be referred to lepidosauromorph/ archosauromorph, basal archosaur, and dinosauromorph trackmakers. Apatopus represented by 11 tracks of a more than 4 m long trackway, is recorded for the first time outside of North America and Europe. The assemblage concurs with the proposed Late Triassic age of the track-bearing beds by the occurrence of Apatopus, Atreipus-Grallator, and Eubrontes. If this is accepted, the stratigraphic range of Synaptichnium and Parachirotherium, hitherto known only from Early or Middle Triassic deposits, has to be extended to the Carnian-Norian. The occurrence of Eubrontes in the Irohalene Member (T5) provides further evidence for large theropods in pre-Jurassic strata. All assemblages are referred to the Scoyenia ichnofacies indicating continental environments with alternating wet and dry conditions.
Abstract - Diverse tetrapod track assemblages with Scoyenia invertebrate traces were discovered in the Triassic Timezgadiouine and Bigoudine formations of the Argana Basin (Western High Atlas, Morocco). The ichnofossils occur in alluvial plain sandstones and mudstones of the Irohalène Member (T5) and Tadart Ouadou Member (T6) considered Carnian-Norian in age by vertebrate remains and palynomorphs. Tetrapod footprints are assigned to Apatopus, Atreipus-Grallator,Eubrontes isp., Parachirotherium, cf. Parachirotherium postchirotherioides, Rhynchosauroides ispp., and Synaptichnium isp. They can be referred to lepidosauromorph/ archosauromorph, basal archosaur, and dinosauromorph trackmakers. Apatopus represented by 11 tracks of a more than 4 m long trackway, is recorded for the first time outside of North America and Europe. The assemblage concurs with the proposed Late Triassic age of the track-bearing beds by the occurrence of Apatopus, Atreipus-Grallator, and Eubrontes. If this is accepted, the stratigraphic range of Synaptichnium and Parachirotherium, hitherto known only from Early or Middle Triassic deposits, has to be extended to the Carnian-Norian. The occurrence of Eubrontes in the Irohalene Member (T5) provides further evidence for large theropods in pre-Jurassic strata. All assemblages are referred to the Scoyenia ichnofacies indicating continental environments with alternating wet and dry conditions.
Finally a Dinosaur Textbook with a Section on Dinosaur Origins! Dinosaurs: A Concise Natural History
In 2010 when I reviewed the first edition of Fastovsky and Weishampel "Dinosaurs: a Concise Natural History" for the Journal of Vertebrate Paleontology I gave it a good review, recommending it for classroom use. However, one complaint I had was that as a book on dinosaurs it had almost no coverage of dinosaur origins. David Fastovsky took note and assured me that the next edition would remedy this.
Well I'm happy to say that the second edition is out and does indeed have a much expanded section on dinosaur origins. Thanks to David and David for not taking my constructive criticism too hard and adding this section. In my opinion this makes what I think is the best dinosaur textbook available even better.
Well I'm happy to say that the second edition is out and does indeed have a much expanded section on dinosaur origins. Thanks to David and David for not taking my constructive criticism too hard and adding this section. In my opinion this makes what I think is the best dinosaur textbook available even better.
Rediscovered Specimen Draws Dinosaur Origins Down Into the Middle Triassic
I've been peripherally involved in the recent renaissance regarding dinosaur origins since my discovery of the skeleton of Revueltosaurus callenderi in 2004 and the subsequent recognition that it was not a dinosaur. With my good friends and colleagues Sterling Nesbitt and Randall Irmis, I proceeded to reexamine much of the Late Triassic dinosaur record using an apomorphy-based approach emphasized by UT Austin professor Chris Bell and his colleagues for Neogene vertebrates. Our findings were that Triassic dinosaurs were actually rarer than previously believed, especially in North America. In addition, extensive fieldwork by Sterling and Randy led to the discoveries of Dromomeron romeri, Tawa hallae, and Asilisaurus kongwe, filling in some key gaps in our understanding of the early diversification of the Ornithodira. Nonetheless it has become readily apparent that many important specimens crucial to this issue were not weathering out of outcrops in the field, but rather were sitting un- or misidentified in museum collections around the globe. Our new understanding of character states and polarities for early diverging dinosauriforms provided us with specific search criteria leading to the discoveries and/or reinterpretations of taxa such as Eucoelophysis baldwini, Dromomeron gregorii, Technosaurus smalli, Daemonosaurus chauliodus, and of course Effigia okeeffae, all from previously collected material including fossils collected for Edward Cope in the 1800s. Furthermore, Randy's work found that the rise of dinosaurs was diachronous, although the timing is still poorly understood.
Known from a partial humerus and several vertebrate (three cervical, five presacral and three sacral), reanalysis places Nyasasaurus as either a dinosaur or as the sister taxon to Dinosauria. The humerus bears a ventrally elongated deltopectoral crest with a deflected apex, both synapomorphies of Dinosauria. The cervical vertebrae are elongate and possess deep lateral fossae, consistent with character states found in dinosaurs. The presence of three sacral vertebrae, although not restricted to Dinosauria, also supports this placement. This interpretation is supported not only by a phylogenetic analysis but also by bone histology, which shows high, continuous growth rates similar to that of early diverging dinosaurs.
This material suggests that dinosaurs probably appeared in the fossil record 10 to 15 million years earlier than we expected. Furthermore, Nesbitt et al. argue that this strongly supports the hypothesis that dinosaurs were not a dominant group during their early history. Finally, Nyasasaurus also provides more support for a Gondwanan origin of dinosaurs.
The discovery of the silesaurid Asilisaurus kongwe (published in 2010) pulled the split between Silesauridae and Dinosauria into the Middle Triassic creating a significant ghost lineage for Dinosauria as the earliest known bona fide dinosaurs do not appear until the end of the Carnian stage of the Late Triassic. Amazingly it appears that we did not need to wait very long for this ghost lineage to be filled.
Today's issue of Biology Letters has a paper by Sterling Nesbitt, Paul Barrett, Sarah Werning, Christian Sidor, and the late Alan Charig on a probable new dinosaur from the Middle Triassic of Tanzania. Even more amazing is that this is not a new specimen, but was actually collected in the 1930s, and never described, except in Charig's 1950s dissertation, until today. Charig named the new specimen Nyasasaurus parringtoni and until now this name has been a nomen nudum.
Today's issue of Biology Letters has a paper by Sterling Nesbitt, Paul Barrett, Sarah Werning, Christian Sidor, and the late Alan Charig on a probable new dinosaur from the Middle Triassic of Tanzania. Even more amazing is that this is not a new specimen, but was actually collected in the 1930s, and never described, except in Charig's 1950s dissertation, until today. Charig named the new specimen Nyasasaurus parringtoni and until now this name has been a nomen nudum.
Known from a partial humerus and several vertebrate (three cervical, five presacral and three sacral), reanalysis places Nyasasaurus as either a dinosaur or as the sister taxon to Dinosauria. The humerus bears a ventrally elongated deltopectoral crest with a deflected apex, both synapomorphies of Dinosauria. The cervical vertebrae are elongate and possess deep lateral fossae, consistent with character states found in dinosaurs. The presence of three sacral vertebrae, although not restricted to Dinosauria, also supports this placement. This interpretation is supported not only by a phylogenetic analysis but also by bone histology, which shows high, continuous growth rates similar to that of early diverging dinosaurs.
This material suggests that dinosaurs probably appeared in the fossil record 10 to 15 million years earlier than we expected. Furthermore, Nesbitt et al. argue that this strongly supports the hypothesis that dinosaurs were not a dominant group during their early history. Finally, Nyasasaurus also provides more support for a Gondwanan origin of dinosaurs.
One thing that is now definitely clear is that workers interested in dinosaur origins will need to spend more time in Middle Triassic terrestrial units. Back in 2004 I don't think any of us fathomed what discoveries and interpretations the next decade would bring. As I often state, it is not necessarily what we already know that dirves our work, but what is still out there for us to learn.
Nesbitt, S. J., Barrett, P. M., Werning, S., Sidor, C.
A., and A. J. Charig. 2012. The oldest dinosaur? A Middle Triassic
dinosauriform from Tanzania. Biology Letters.
Abstract - The rise of dinosaurs was a major event in vertebrate
history, but the timing of the origin and early diversification of the group
remain poorly constrained. Here, we describe Nyasasaurus parringtoni gen. et sp. nov., which is
identified as either the earliest known member of, or the sister-taxon to,
Dinosauria. Nyasasaurus
possesses
a unique combination of dinosaur character states and an elevated growth rate similar
to that of definitive early dinosaurs. It demonstrates that the initial
dinosaur radiation occurred over a longer timescale than previously thought
(possibly 15 My earlier), and that dinosaurs and their immediate relatives are
better understood as part of a larger Middle Triassic archosauriform radiation.
The African provenance of Nyasasaurus supports a southern Pangaean origin for Dinosauria.
Dr. Farish Jenkins 1940-2012
Many of you are already aware, but Professor Farish Jenkins of Harvard University passed away earlier this month at the age of 72. A vertebrate paleontologist, Dr. Jenkins was well known for his Triassic work in Greenland and even more so for his work in the Triassic and Jurassic of the Colorado Plateau, especially regarding early mammals.
http://www.nytimes.com/2012/12/01/us/farish-jenkins-fossils-expert-dies-at-72.html
http://www.nytimes.com/2012/12/01/us/farish-jenkins-fossils-expert-dies-at-72.html
Biomechanical Comments about Triassic Dinosaurs from Brazil
Delcourt, R., de Azevedo, S. A. K., Grillo, O. N., and F. O. Deantoni. 2012. Biomechanical comments about Triassic dinosaurs from Brazil. Papáis Avulsos de Zoologia 52:341-347.
Abstract - Triassic dinosaurs of Brazil are found in Santa Maria and Caturrita formations, Rio Grande do Sul state, Brazil. There are three species known from the Santa Maria Formation (Staurikosaurus pricei, Saturnalia tupiniquim and Pampadromaeus barberenai), and two from Caturrita Formation (Guaibasaurus candelariensis and Unaysaurus tolentinoi). These dinosaur materials are, for the most part, well preserved and allow for descriptions of musculature and biomechanical studies. The lateral rotation of the Saturnalia femur is corroborated through calculations of muscle moment arms. The enhanced supracetabular crest of Saturnalia, Guaibasaurus, Staurikosaurus, Herrerasaurus ischigualastensis, Efraasia minor and Chormogisaurus [sic] novasi suggests that basal dinosaurs may have maintained an inclination of the trunk at least 20° on the horizontal axis. The pectoral girdle articulation of basal sauropodomorphs (Saturnalia and Unaysaurus) was established using a new method, the Clavicular Ring, and the scapular blade remains near 60° on the horizontal axis. This is a plesiomorphic condition among sauropodomorphs and is also seen in the articulated plateosauridae Seitaad ruessi. The Brazilian basal dinosaurs were lightweight with a body mass estimated around 18.5 kg for Staurikosaurus, 6.5 kg for Saturnalia, and 17 kg for Guaibasaurus. Pampadromaeus probably weighed 2.5 kg, but measures of its femur are necessary to confirm this hypothesis. The Triassic dinosaurs from Brazil were diversified but shared some functional aspects that were important in an evolutionary context.
Abstract - Triassic dinosaurs of Brazil are found in Santa Maria and Caturrita formations, Rio Grande do Sul state, Brazil. There are three species known from the Santa Maria Formation (Staurikosaurus pricei, Saturnalia tupiniquim and Pampadromaeus barberenai), and two from Caturrita Formation (Guaibasaurus candelariensis and Unaysaurus tolentinoi). These dinosaur materials are, for the most part, well preserved and allow for descriptions of musculature and biomechanical studies. The lateral rotation of the Saturnalia femur is corroborated through calculations of muscle moment arms. The enhanced supracetabular crest of Saturnalia, Guaibasaurus, Staurikosaurus, Herrerasaurus ischigualastensis, Efraasia minor and Chormogisaurus [sic] novasi suggests that basal dinosaurs may have maintained an inclination of the trunk at least 20° on the horizontal axis. The pectoral girdle articulation of basal sauropodomorphs (Saturnalia and Unaysaurus) was established using a new method, the Clavicular Ring, and the scapular blade remains near 60° on the horizontal axis. This is a plesiomorphic condition among sauropodomorphs and is also seen in the articulated plateosauridae Seitaad ruessi. The Brazilian basal dinosaurs were lightweight with a body mass estimated around 18.5 kg for Staurikosaurus, 6.5 kg for Saturnalia, and 17 kg for Guaibasaurus. Pampadromaeus probably weighed 2.5 kg, but measures of its femur are necessary to confirm this hypothesis. The Triassic dinosaurs from Brazil were diversified but shared some functional aspects that were important in an evolutionary context.
Postcranial Anatomy of a Late Triassic Sauropodomorph from Argentina
Apaldetti, C., Diego Pol, D., and A. Yates. 2012. The postcranial anatomy of Coloradisaurus brevis (Dinosauria: Sauropodomorpha) from the Late Triassic of Argentina and its phylogenetic implications. Palaeontology (Early View) DOI: 10.1111/j.1475-4983.2012.
Abstract - Basal sauropodomorphs from the Upper Triassic Los Colorados Formation
of north-western Argentina have been known for several decades but
most of them are only briefly described. New postrcanial remains of
Coloradisaurus brevis, the most gracile sauropodomorph from this unit,
are described here and evaluated within a phylogenetic context. These
materials belong to a single individual and include elements of the
vertebral column, pectoral girdle, incomplete forelimb, pelvis and
hindlimb. These elements share an autapomorphic feature with the type
specimen of Coloradisaurus brevis and provide novel and unique
features that diagnose this taxon, such as pubic apron with
semicircular cross-section and with a depression on its anterior
surface, distal surface of the tibia deflected and facing
posterodistally and well-developed pyramidal dorsal process of the
posteromedial corner of the astragalus. Several postcranial characters
of Coloradisaurus are exclusively shared with Lufengosaurus, from the
Lower Jurassic of China. The inclusion of this information in two
recent phylogenetic data sets depicts Coloradisaurus as closely
related to Lufengosaurus and well nested within Plateosauria. Both
data sets used indicate strong character support for the inclusion of
Coloradisaurus and Lufengosaurus within Massospondylidae.
Abstract - Basal sauropodomorphs from the Upper Triassic Los Colorados Formation
of north-western Argentina have been known for several decades but
most of them are only briefly described. New postrcanial remains of
Coloradisaurus brevis, the most gracile sauropodomorph from this unit,
are described here and evaluated within a phylogenetic context. These
materials belong to a single individual and include elements of the
vertebral column, pectoral girdle, incomplete forelimb, pelvis and
hindlimb. These elements share an autapomorphic feature with the type
specimen of Coloradisaurus brevis and provide novel and unique
features that diagnose this taxon, such as pubic apron with
semicircular cross-section and with a depression on its anterior
surface, distal surface of the tibia deflected and facing
posterodistally and well-developed pyramidal dorsal process of the
posteromedial corner of the astragalus. Several postcranial characters
of Coloradisaurus are exclusively shared with Lufengosaurus, from the
Lower Jurassic of China. The inclusion of this information in two
recent phylogenetic data sets depicts Coloradisaurus as closely
related to Lufengosaurus and well nested within Plateosauria. Both
data sets used indicate strong character support for the inclusion of
Coloradisaurus and Lufengosaurus within Massospondylidae.
New Data on Small Theropod Footprints from Massachusetts
Dalman. S. G. 2012. New Data on Small Theropod Footprints from the Early Jurassic (Hettangian) Hartford Basin of Massachusetts, United States. Bulletin of the Peabody Museum of Natural History 53:333-353. doi:http://www.bioone.org/doi/abs/10.3374/014.053.0201
Abstract - A Portland Formation Lower Jurassic (Hettangian) dinosaur tracksite in Granby, Massachusetts, USA, has yielded a diverse dinosaur footprint assemblage. The tracksite preserves 140 theropod dinosaur footprints, ranging in length from 15 to 35 cm; the ichnofauna includes Anchisauripus, Eubrontes, Grallator and other extremely small theropod dinosaur footprints. The small tracks are compared with similar ichnites from the Lower Jurassic of western North America and central Poland. The small theropod footprints, which are described in detail, show some resemblance to the poorly known ichnogenus Stenonyx (Lull, 1904), which is considered an invalid ichnotaxon by many other workers. The footprints exhibit a distinct morphology of the metatarsophalangeal area, suggesting that these small ichnites are closely related to Kayentapus and Grallator. These small tracks are the first reported from the Hartford Basin of Granby, Massachusetts.
Abstract - A Portland Formation Lower Jurassic (Hettangian) dinosaur tracksite in Granby, Massachusetts, USA, has yielded a diverse dinosaur footprint assemblage. The tracksite preserves 140 theropod dinosaur footprints, ranging in length from 15 to 35 cm; the ichnofauna includes Anchisauripus, Eubrontes, Grallator and other extremely small theropod dinosaur footprints. The small tracks are compared with similar ichnites from the Lower Jurassic of western North America and central Poland. The small theropod footprints, which are described in detail, show some resemblance to the poorly known ichnogenus Stenonyx (Lull, 1904), which is considered an invalid ichnotaxon by many other workers. The footprints exhibit a distinct morphology of the metatarsophalangeal area, suggesting that these small ichnites are closely related to Kayentapus and Grallator. These small tracks are the first reported from the Hartford Basin of Granby, Massachusetts.
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