Benton, M. J. 2010. Archosaur remains from the Otter Sandstone Formation(MiddleTriassic, late Anisian) of Devon, southern UK. Proceedings of the Geologists' Association (early online), doi:10.1016/j.pgeola.2010.08.004
Abstract - A new jaw from the Middle Triassic (Anisian) Otter Sandstone Formation of Devon confirms the existence of a derived archosaur(avesuchian). Numerous isolated teeth and vertebrae had already suggested the presence of archosaurs in the Otter Sandstone Formation, presumed predators on the fauna of temnospondyls, procolophonids, and rhynchosaurs, but the new fossil is the first to show some diagnostic characters. Other elements in the same block as the jaw, but not necessarily from the same animal, include a possible skull or pelvic bone, a slender long bone, a small tooth (perhaps prolacertiform), and two presumed archosaur dermal scutes. An additional scute is present, as well as the probable distal end of a pubis, perhaps from a large poposauroid archosaur like the Anisian-age Bromsgroveia or Arizonasaurus. The jaw and pubis represent animals of very different sizes, some 0.8m and 3m long in estimated body length respectively.
A Recent Mention of Two Possibly New Archosauriforms from the Middle Triassic of Germany
This very interesting article was recently brought to my attention. It mentions several possibly new archosauriforms from the Middle Triassic of Germany, including a proterochampsid and a small bipedal form that could be a basal ornithodiran.
http://www.swp.de/crailsheim/lokales/land/art5509,632515
http://www.swp.de/crailsheim/lokales/land/art5509,632515
Pravusuchus hortus the Wicked Phytosaur from the Petrified Forest
Stocker, M. R. 2010. A new taxon of phytosaur (Archosauria: Pseudosuchia) from the Late Triassic (Norian) Sonsela Member (Chinle Formation) in Arizona, and a critical re-evaluation of Leptosuchus Case 1922. Palaeontology 53:997-1022. doi: 10.1111/j.1475-4983.2010.00983.x
Abstract - Leptosuchus Case, 1922 (Reptilia: Phytosauria) from the Late Triassic of the American West is represented by many specimens. Here, I present complete morphological descriptions of the skull material of a new taxon from the Sonsela Member (Chinle Formation) of Petrified Forest National Park, Arizona, with the first rigorous phylogenetic analysis focused on the interrelationships of Leptosuchus. The new taxon is recovered as the sister taxon to Pseudopalatinae. It possesses one unambiguous synapomorphy (the ‘septomaxillae’ form part of the lateral borders of the nares) and shares the presence of a subsidiary opisthotic process with Pseudopalatinae. The new taxon does not fall within the restricted clade Leptosuchus. In my analysis, the previously proposed, but undemonstrated, sister taxon relationship between Angistorhinus and Rutiodon is not supported, Paleorhinus is recovered as paraphyletic, and a subset of taxa traditionally included within Leptosuchus are found to be more closely related to Pseudopalatinae, rendering Leptosuchus paraphyletic. ‘Leptosuchus’ adamanensis emerges as sister taxon to Smilosuchus gregorii and is here referred to as Smilosuchus adamanensis nov. comb., and ‘Machaeroprosopus’ lithodendrorum is also transferred to Smilosuchus lithodendrorum nov. comb. Documentation of the variation present within Phytosauria, and specifically within Leptosuchus sensu lato, demonstrates higher diversity within Phytosauria than previously appreciated and places the character states previously proposed for Pseudopalatinae into a broader context of shared characters.
One specific subject that even the heartiest of Triassic workers will often go out of their way to avoid is the issue of phytosaur taxonomy, and for good reason, it is a mess. I previously supplied a flowchart I created in 2001 that demonstrates how much of a mess I’m talking about. Recent revisions (e.g., Hungerbühler 2002) have dealt almost exclusively with the pseudopalatine phytosaurs and the rest of the group has been relatively neglected since Long and Murry’s (1995) treatment. The genus Leptosuchus (still assigned to Rutiodon by some) has been poorly understood, and most new specimens assigned to this genus have been lumped into existing species without clear discussion of the characters used to support these assignments (I’m am guilty of this myself).
In the Spring of 2003 Daniel Woody and I discovered a large phytosaur skull in the Devil’s Playground portion of Petrified Forest National Park during a geological reconnaissance. That summer a crew consisting of Randall Irmis, Michelle Stocker, Jeff Shuman, and I collected the skull (now PEFO 31218) and our group initiated preparation. A couple of months later Jeff, Randy, and I discovered a second skull very close by; however, this skull appeared to only consist of a set of badly eroded lower jaws and was not collected. Interestingly we made the discovery while we were relocating and rephotographing a photo taken by Edwin Colbert of a phytosaur skull excavation conducted by the AMNH in 1946. Amazingly both skull sites are in this historic photo.
In 2006 Michelle and I reinvestigated the lower jaws and discovered that much of the skull was indeed present. This skull (PEFO 34239) was collected and Michelle began the preparation. About this time Michelle was looking for a good project for her Master’s thesis at the University of Iowa and despite knowing the potential pitfalls in the morass of phytosaur taxonomy, I suggested that maybe she should describe the two PEFO skulls (she had helped excavate and prep both of them) and determine their taxonomic affinities. Fast forwarding to the present it would seem that this was indeed a very good project and Michelle produced a very fine thesis (Stocker 2008), a portion of which is presented in this paper. She has since become quite the expert in the phytosaurs of the American Southwest and I look forward to more of her work on this subject (it is badly needed).
Some important points from this paper and details on the specimens:
1) Erects a new phytosaur taxon, Pravusuchus hortus, from the Sonsela Member of the Chinle Formation of Petrified Forest National Park. Existing specimens of Pravusuchus were originally assigned to the genus Leptosuchus, but detailed analysis shows that the taxon is distinct, possessing skull characters found in both ‘leptosuchines’ and pseudopalatines.
2) The holotype (AMNH FR 30646) was originally collected from the Petrified Forest in 1946 by Edwin Colbert of the American Museum of Natural History. The referred specimens are from the same geographical area and stratigraphic horizon and were collected by park staff (including Michelle Stocker) in 2003 and 2006.
3) Stratigraphically the specimens were found between the highest specimens of “Leptosuchus” and the lowest specimens of Pseudopalatus (Parker and Martz in press).
4) The genus Leptosuchus (sensu Long and Murry 1995) is paraphyletic and specimens referred to the genus are now only found in the Dockum Group. Arizona specimens of “Leptosuchus” are reassigned to Pravusuchus and Smilosuchus.
5) Stocker considers there to be three valid species of Smilosuchus; S. gregorii (the type species), S. adamanensis, and S. lithodendrorum. These last two are new combinations and this study resurrects the species S. lithodendrorum, which was considered a junior sysnonym of Leptosuchus crosbiensis by Long and Murry (1995).
This paper contains the most inclusive phylogenetic analysis of the Phytosauria since Ballew (1989). Some results:
1) The genus Paleorhinus is paraphyletic. Although this idea has been floating around for awhile (e.g., Fara and Hungerbuehler 2000) this is the first time it has been supported with a phylogenetic analysis.
2) The genera Anghistorhinus and Rutiodon are distinct. This synonymy was first put forth in an abstract by Hungerbuehler and Sues in 2001, but is not recovered in this study.
3) The name Rutiodon is restricted to specimens from the eastern United States. The name Rutiodon is often used for phytosaur specimens from the western United States stemming back to work by Gregory (1962) and Ballew (1989); however, this paper clearly shows that these referrals are erroneous and Rutiodon should be restricted to material from the eastern U.S.
This analysis should form the basis of future studies on the lower part of the phytosaur tree for a long time to come.
REFERENCES
Ballew, K. L. 1989. A phylogenetic analysis of Phytosauria from the Late Triassic of the western United States. 309–339. In LUCAS, S. G. and HUNT, A. P. (eds). Dawn of the age of dinosaurs in the American Southwest. New Mexico Museum of Natural History, Albuquerque, 414 pp.
Fara, E., and Hungerbühler, A. 2000. Paleorhinus magnoculus from the Upper Triassic of Morocco: a juvenile primitive phytosaur (Archosauria). Comptes Rendus de l’Académie des Sciences, Paris, Sciences de la Terre et des planétes, 331, 831–836.
Gregory, J. T. 1962. The genera of the phytosaurs. American Journal of Science, 260, 652–690.
Hungerbühler, A. 2002. The Late Triassic phytosaur Mystriosuchus westphali, with a revision of the genus. Palaeontology, 45, 377–418.
Hungerbühler, A., and Sues, H.-D. 2001. Status and phylogenetic relationships of the Late Triassic phytosaur Rutiodon carolinensis. Journal of Vertebrate Paleontology, 21(3-Suppl.), 64A.
Long, R. A. and Murry, P. A. 1995. Late Triassic (Carnian and Norian) tetrapods from the southwestern United States. Bulletin of the New Mexico Museum of Natural History and Science, 4, 1–254.
Stocker, M. R. 2008. Relationships of the phytosaur Leptosuchus Case 1922 with descriptions of new material from Petrified Forest National Park, Arizona. Unpublished MS thesis, University of Iowa, Iowa City, 220 pp.
Abstract - Leptosuchus Case, 1922 (Reptilia: Phytosauria) from the Late Triassic of the American West is represented by many specimens. Here, I present complete morphological descriptions of the skull material of a new taxon from the Sonsela Member (Chinle Formation) of Petrified Forest National Park, Arizona, with the first rigorous phylogenetic analysis focused on the interrelationships of Leptosuchus. The new taxon is recovered as the sister taxon to Pseudopalatinae. It possesses one unambiguous synapomorphy (the ‘septomaxillae’ form part of the lateral borders of the nares) and shares the presence of a subsidiary opisthotic process with Pseudopalatinae. The new taxon does not fall within the restricted clade Leptosuchus. In my analysis, the previously proposed, but undemonstrated, sister taxon relationship between Angistorhinus and Rutiodon is not supported, Paleorhinus is recovered as paraphyletic, and a subset of taxa traditionally included within Leptosuchus are found to be more closely related to Pseudopalatinae, rendering Leptosuchus paraphyletic. ‘Leptosuchus’ adamanensis emerges as sister taxon to Smilosuchus gregorii and is here referred to as Smilosuchus adamanensis nov. comb., and ‘Machaeroprosopus’ lithodendrorum is also transferred to Smilosuchus lithodendrorum nov. comb. Documentation of the variation present within Phytosauria, and specifically within Leptosuchus sensu lato, demonstrates higher diversity within Phytosauria than previously appreciated and places the character states previously proposed for Pseudopalatinae into a broader context of shared characters.
One specific subject that even the heartiest of Triassic workers will often go out of their way to avoid is the issue of phytosaur taxonomy, and for good reason, it is a mess. I previously supplied a flowchart I created in 2001 that demonstrates how much of a mess I’m talking about. Recent revisions (e.g., Hungerbühler 2002) have dealt almost exclusively with the pseudopalatine phytosaurs and the rest of the group has been relatively neglected since Long and Murry’s (1995) treatment. The genus Leptosuchus (still assigned to Rutiodon by some) has been poorly understood, and most new specimens assigned to this genus have been lumped into existing species without clear discussion of the characters used to support these assignments (I’m am guilty of this myself).
In the Spring of 2003 Daniel Woody and I discovered a large phytosaur skull in the Devil’s Playground portion of Petrified Forest National Park during a geological reconnaissance. That summer a crew consisting of Randall Irmis, Michelle Stocker, Jeff Shuman, and I collected the skull (now PEFO 31218) and our group initiated preparation. A couple of months later Jeff, Randy, and I discovered a second skull very close by; however, this skull appeared to only consist of a set of badly eroded lower jaws and was not collected. Interestingly we made the discovery while we were relocating and rephotographing a photo taken by Edwin Colbert of a phytosaur skull excavation conducted by the AMNH in 1946. Amazingly both skull sites are in this historic photo.
In 2006 Michelle and I reinvestigated the lower jaws and discovered that much of the skull was indeed present. This skull (PEFO 34239) was collected and Michelle began the preparation. About this time Michelle was looking for a good project for her Master’s thesis at the University of Iowa and despite knowing the potential pitfalls in the morass of phytosaur taxonomy, I suggested that maybe she should describe the two PEFO skulls (she had helped excavate and prep both of them) and determine their taxonomic affinities. Fast forwarding to the present it would seem that this was indeed a very good project and Michelle produced a very fine thesis (Stocker 2008), a portion of which is presented in this paper. She has since become quite the expert in the phytosaurs of the American Southwest and I look forward to more of her work on this subject (it is badly needed).
Some important points from this paper and details on the specimens:
1) Erects a new phytosaur taxon, Pravusuchus hortus, from the Sonsela Member of the Chinle Formation of Petrified Forest National Park. Existing specimens of Pravusuchus were originally assigned to the genus Leptosuchus, but detailed analysis shows that the taxon is distinct, possessing skull characters found in both ‘leptosuchines’ and pseudopalatines.
2) The holotype (AMNH FR 30646) was originally collected from the Petrified Forest in 1946 by Edwin Colbert of the American Museum of Natural History. The referred specimens are from the same geographical area and stratigraphic horizon and were collected by park staff (including Michelle Stocker) in 2003 and 2006.
3) Stratigraphically the specimens were found between the highest specimens of “Leptosuchus” and the lowest specimens of Pseudopalatus (Parker and Martz in press).
4) The genus Leptosuchus (sensu Long and Murry 1995) is paraphyletic and specimens referred to the genus are now only found in the Dockum Group. Arizona specimens of “Leptosuchus” are reassigned to Pravusuchus and Smilosuchus.
5) Stocker considers there to be three valid species of Smilosuchus; S. gregorii (the type species), S. adamanensis, and S. lithodendrorum. These last two are new combinations and this study resurrects the species S. lithodendrorum, which was considered a junior sysnonym of Leptosuchus crosbiensis by Long and Murry (1995).
This paper contains the most inclusive phylogenetic analysis of the Phytosauria since Ballew (1989). Some results:
1) The genus Paleorhinus is paraphyletic. Although this idea has been floating around for awhile (e.g., Fara and Hungerbuehler 2000) this is the first time it has been supported with a phylogenetic analysis.
2) The genera Anghistorhinus and Rutiodon are distinct. This synonymy was first put forth in an abstract by Hungerbuehler and Sues in 2001, but is not recovered in this study.
3) The name Rutiodon is restricted to specimens from the eastern United States. The name Rutiodon is often used for phytosaur specimens from the western United States stemming back to work by Gregory (1962) and Ballew (1989); however, this paper clearly shows that these referrals are erroneous and Rutiodon should be restricted to material from the eastern U.S.
This analysis should form the basis of future studies on the lower part of the phytosaur tree for a long time to come.
REFERENCES
Ballew, K. L. 1989. A phylogenetic analysis of Phytosauria from the Late Triassic of the western United States. 309–339. In LUCAS, S. G. and HUNT, A. P. (eds). Dawn of the age of dinosaurs in the American Southwest. New Mexico Museum of Natural History, Albuquerque, 414 pp.
Fara, E., and Hungerbühler, A. 2000. Paleorhinus magnoculus from the Upper Triassic of Morocco: a juvenile primitive phytosaur (Archosauria). Comptes Rendus de l’Académie des Sciences, Paris, Sciences de la Terre et des planétes, 331, 831–836.
Gregory, J. T. 1962. The genera of the phytosaurs. American Journal of Science, 260, 652–690.
Hungerbühler, A. 2002. The Late Triassic phytosaur Mystriosuchus westphali, with a revision of the genus. Palaeontology, 45, 377–418.
Hungerbühler, A., and Sues, H.-D. 2001. Status and phylogenetic relationships of the Late Triassic phytosaur Rutiodon carolinensis. Journal of Vertebrate Paleontology, 21(3-Suppl.), 64A.
Long, R. A. and Murry, P. A. 1995. Late Triassic (Carnian and Norian) tetrapods from the southwestern United States. Bulletin of the New Mexico Museum of Natural History and Science, 4, 1–254.
Stocker, M. R. 2008. Relationships of the phytosaur Leptosuchus Case 1922 with descriptions of new material from Petrified Forest National Park, Arizona. Unpublished MS thesis, University of Iowa, Iowa City, 220 pp.
Koilamasuchus gonzalezdiazi, a New Basal Archosauriform from the Lower Triassic of Argentina
Ezcurra, M. D. , Lecuona, A., and A. Martinelii. 2010. A new basal archosauriform diapsid from the Lower Triassic of Argentina, Journal of Vertebrate Paleontology 30:1433-1450, doi: 10.1080/02724634.2010.501446
Abstract - The best-known South American Early Triassic archosauriform belongs to a putative proterosuchid briefly reported by Jose Bonaparte in 1981, collected from the Quebrada de los Fosiles Formation (Puesto Viejo Group, Argentina). This specimen consists of well-preserved natural external molds of a partial postcranium that preserve dorsal vertebrae, osteoderms, a dorsal rib, a possible gastralium, a chevron, a humerus, an ilium, two metapodials, and an ungual. We re-describe this specimen and identify autapomorphies that allow us to recognize Koilamasuchus gonzalezdiazi, gen. et sp. nov. The presence of an iliac blade with a slightly convex dorsal margin and with a maximum length more than 3 times its maximum height places Koilamasuchus within Archosauriformes. A cladistic analysis of basal Archosauriformes positions Koilamasuchus more crownwards than Proterosuchus, Sarmatosuchus, Fugusuchus, and Osmolskina, as the sister taxon of the clade that includes Erythrosuchidae and Archosauria. Proterosuchidae is found to be paraphyletic. The presence of an iliac preacetabular process, a pubic peduncle that forms an angle lower than 45◦ to the longitudinal axis of the ilium, and dorsal body osteoderms positions Koilamasuchus in Archosauriformes more crownwards than proterosuchids. Koilamasuchus is more basal than erythrosuchids within Archosauriformes because of the presence of dorsal ribs with a poorly developed proximal end. Koilamasuchus importantly increases the diversity of Archosauriformes during the biotic recovery following the Permo-Triassic mass extinction.
This is an interesting paper from the new issue of the Journal of Vertebrate Paleontology describing a new archosauriform from the Early Triassic of South America. Along with recent descriptions of the enigmatic form Vancleavea (Parker and Barton 2008; Nesbitt et al. 2009) as well as a modern description of Doswellia (Dilkes and Sues 2009), this new taxon helps flesh out relationships in this part of the tree. I've only briefly skimmed the paper so far, but noticed some interesting conclusions from the study:
1) Proterosuchidae is paraphyletic - the monophyly of the group is rarely tested as most recent studies just use Proterosuchus as a terminal taxon in phylogenetic analyses.
2) Vancleavea and Doswellia form a clade which is closer to Archosauria than Euparkeria and Chanaresuchus are - as stated in the paper this is closer to the results that I obtained in my 2008 paper on Vancleavea (Parker and Barton 2008); however, the results of our phylogenetic analysis weren't very robust.
3) Turfanosuchus is a pseudosuchian - I've always hypothesized this as the calcaneum of Turfanosuchus is extremely similar to that of aetosaurs and the femur is almost identical to that of Revueltosaurus in overall morphology and in possessing a massive fourth trochanter (Parker et al. 2005).
One unfortunate preservational aspect of this material is the lack of the femur, which I feel is a key element in determining whether the taxon would be closer to Proterosuchus and Erythrosuchus with their primitive morphology, or to the more derived forms Vancleavea and Euparkeria (see the discussion in Parker and Barton 2008). Another key aspect that could affect the phylogenetic analysis (and possibly did in this paper) is the coding of osteoderms as present in Erythrosuchus, which could potentially place erythrosuchids in a more crownward position. Despite the recovery of a couple of possible osteoderms with material of Erythrosuchus (Gower 2003) their actual presence in this taxon is ambiguous and should not be coded as present (Parker and Barton 2008; Nesbitt et al. 2009). This coding may explain why Koilamasuchus is recovered as more basal to erythrosuchids in this analysis.
REFERENCES
Dilkes, D.W., and H.-D. Sues. 2009. Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 29:58–79.
Gower, D. J. 2003. Osteology of the early archosaurian reptile Erythrosuchus africanus Broom. Annals of the South African Museum 110:1–84.
Nesbitt, S. J., Stocker, M. R., Small, B. J., and Downs, A. 2009. The osteology and relationships of Vancleavea campi (Reptilia: Archosauriformes). Zoological Journal of the Linnean Society 157:814–864.
Parker, W. G., and B. J. Barton. 2008. New information on the Upper Triassic archosauriform Vancleavea campi based on new material from the Chinle Formation of Arizona. Paleontologia Electronica 11.3.14A:1–20.
Parker, W. G., R. B. Irmis, S. J. Nesbitt, J. W. Martz, and L. S. Browne. 2005. The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. Proceedings of the Royal Society of London, Series B: Biological Sciences 272:963–969.
Abstract - The best-known South American Early Triassic archosauriform belongs to a putative proterosuchid briefly reported by Jose Bonaparte in 1981, collected from the Quebrada de los Fosiles Formation (Puesto Viejo Group, Argentina). This specimen consists of well-preserved natural external molds of a partial postcranium that preserve dorsal vertebrae, osteoderms, a dorsal rib, a possible gastralium, a chevron, a humerus, an ilium, two metapodials, and an ungual. We re-describe this specimen and identify autapomorphies that allow us to recognize Koilamasuchus gonzalezdiazi, gen. et sp. nov. The presence of an iliac blade with a slightly convex dorsal margin and with a maximum length more than 3 times its maximum height places Koilamasuchus within Archosauriformes. A cladistic analysis of basal Archosauriformes positions Koilamasuchus more crownwards than Proterosuchus, Sarmatosuchus, Fugusuchus, and Osmolskina, as the sister taxon of the clade that includes Erythrosuchidae and Archosauria. Proterosuchidae is found to be paraphyletic. The presence of an iliac preacetabular process, a pubic peduncle that forms an angle lower than 45◦ to the longitudinal axis of the ilium, and dorsal body osteoderms positions Koilamasuchus in Archosauriformes more crownwards than proterosuchids. Koilamasuchus is more basal than erythrosuchids within Archosauriformes because of the presence of dorsal ribs with a poorly developed proximal end. Koilamasuchus importantly increases the diversity of Archosauriformes during the biotic recovery following the Permo-Triassic mass extinction.
This is an interesting paper from the new issue of the Journal of Vertebrate Paleontology describing a new archosauriform from the Early Triassic of South America. Along with recent descriptions of the enigmatic form Vancleavea (Parker and Barton 2008; Nesbitt et al. 2009) as well as a modern description of Doswellia (Dilkes and Sues 2009), this new taxon helps flesh out relationships in this part of the tree. I've only briefly skimmed the paper so far, but noticed some interesting conclusions from the study:
1) Proterosuchidae is paraphyletic - the monophyly of the group is rarely tested as most recent studies just use Proterosuchus as a terminal taxon in phylogenetic analyses.
2) Vancleavea and Doswellia form a clade which is closer to Archosauria than Euparkeria and Chanaresuchus are - as stated in the paper this is closer to the results that I obtained in my 2008 paper on Vancleavea (Parker and Barton 2008); however, the results of our phylogenetic analysis weren't very robust.
3) Turfanosuchus is a pseudosuchian - I've always hypothesized this as the calcaneum of Turfanosuchus is extremely similar to that of aetosaurs and the femur is almost identical to that of Revueltosaurus in overall morphology and in possessing a massive fourth trochanter (Parker et al. 2005).
One unfortunate preservational aspect of this material is the lack of the femur, which I feel is a key element in determining whether the taxon would be closer to Proterosuchus and Erythrosuchus with their primitive morphology, or to the more derived forms Vancleavea and Euparkeria (see the discussion in Parker and Barton 2008). Another key aspect that could affect the phylogenetic analysis (and possibly did in this paper) is the coding of osteoderms as present in Erythrosuchus, which could potentially place erythrosuchids in a more crownward position. Despite the recovery of a couple of possible osteoderms with material of Erythrosuchus (Gower 2003) their actual presence in this taxon is ambiguous and should not be coded as present (Parker and Barton 2008; Nesbitt et al. 2009). This coding may explain why Koilamasuchus is recovered as more basal to erythrosuchids in this analysis.
REFERENCES
Dilkes, D.W., and H.-D. Sues. 2009. Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 29:58–79.
Gower, D. J. 2003. Osteology of the early archosaurian reptile Erythrosuchus africanus Broom. Annals of the South African Museum 110:1–84.
Nesbitt, S. J., Stocker, M. R., Small, B. J., and Downs, A. 2009. The osteology and relationships of Vancleavea campi (Reptilia: Archosauriformes). Zoological Journal of the Linnean Society 157:814–864.
Parker, W. G., and B. J. Barton. 2008. New information on the Upper Triassic archosauriform Vancleavea campi based on new material from the Chinle Formation of Arizona. Paleontologia Electronica 11.3.14A:1–20.
Parker, W. G., R. B. Irmis, S. J. Nesbitt, J. W. Martz, and L. S. Browne. 2005. The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. Proceedings of the Royal Society of London, Series B: Biological Sciences 272:963–969.
Temnospondyl Paleoenvironmental Adaptations: Evidence from Bone Histology
Sanchez, S., Germain, D., De Ricqles, A., Abourachid, A., Goussard, F. and Tafforeau, P. 2010. Limb-bone histology of temnospondyls: implications for understanding the diversification of palaeoecologies and patterns of locomotion of Permo-Triassic tetrapods. Journal of Evolutionary Biology, early online. doi:10.1111/j.1420-9101.2010.02081.x
Abstract - The locomotion of early tetrapods has long been a subject of great interest in the evolutionary history of vertebrates. However, we still do not have a precise understanding of the evolutionary radiation of their locomotory strategies. We present here the first palaeohistological study based on theoretical biomechanical considerations among a highly diversified group of early tetrapods, the temnospondyls. Based on the quantification of microanatomical and histological parameters in the humerus and femur of nine genera, this multivariate analysis provides new insights concerning the adaptations of temnospondyls to their palaeoenvironments during the Early Permian, and clearly after the Permo-Triassic crisis. This study therefore presents a methodology that, if based on a bigger sample, could contribute towards a characterization of the behaviour of species during great evolutionary events.
Abstract - The locomotion of early tetrapods has long been a subject of great interest in the evolutionary history of vertebrates. However, we still do not have a precise understanding of the evolutionary radiation of their locomotory strategies. We present here the first palaeohistological study based on theoretical biomechanical considerations among a highly diversified group of early tetrapods, the temnospondyls. Based on the quantification of microanatomical and histological parameters in the humerus and femur of nine genera, this multivariate analysis provides new insights concerning the adaptations of temnospondyls to their palaeoenvironments during the Early Permian, and clearly after the Permo-Triassic crisis. This study therefore presents a methodology that, if based on a bigger sample, could contribute towards a characterization of the behaviour of species during great evolutionary events.
Tracking Charles L. Camp in the Blue Hills of Arizona
As my longtime readers know one of my favorite aspects of paleontological research is redocumenting historic localities. It is important to exactly relocate these sites in order to place them in our modern stratigraphic framework, thus the fossils collected from these sites add more data to our local biostratigraphy. But I also just get the thrill of following in our predecessors footsteps, seeing the terrain as they saw it. It simply makes their data more relevant and in a way much more easier to understand when you take a walk in their shoes (or boots).
Last week it was off to the Blue Hills northeast of St. Johns, Arizona. In 1923 and 1924 Charles Camp of the UCMP made significant vertebrate fossil collections from these localities, including the type specimen of the phytosaur Machaeroprosopus zunii. The stratigraphic position of this specimen was in doubt because Camp had misinterpreted underlying Chinle Formation strata as belonging to the Moenkopi Formation. Jeff Martz and I had been interested in the stratigraphic position of this specimen for awhile so with old field notes and photos in hand, and with one of the main local landowners showing us the best way to access the badlands, we were on our way.
We were successful in relocating the M. zunii quarry almost immediately. The two photos directly below are one taken by Camp in 1923 of the M. zunii excavation (courtesy of the UCMP) and me at the same spot in 2010.
We were successful in relocating the M. zunii quarry almost immediately. The two photos directly below are one taken by Camp in 1923 of the M. zunii excavation (courtesy of the UCMP) and me at the same spot in 2010.
More difficult to find was Camp's "meal pots" locality, a greenish mudstone and fine sandstone horizon that produced numerous microvertebrates including plates of the diminuative aetosaur Acaenasuchus geoffreyi and some of the oldest recovered elements of the pseudosuchian Revueltosaurus. Camp's field notes were a little ambiguous regarding this site, but we were able to finally relocate it (see photo below).
Jurassic Phytosaur??
A new paper by Maisch and Kapitzke (2010) describes a mandibular fragment from a phytosaur from marine shales in England. This is supposedly the first record of a phytosaur from the Jurassic (Hettangian) as the specimen was found in-situ beneath beds that provide the lowest occurrence of the ammonoid Psiloceras. Thus some phytosaurs, in this case a marine one from Europe, purportedly survived the end-Triassic extinction.
However, as Randall Irmis (who also informed me of this paper) reminded me, this is non-sensical regarding this specimen as the base of the Jurassic is presently defined by the first appearance of Psiloceras. Thus the phytosaur bearing strata are latest Triassic in age and not Jurassic.
I'm not adverse to the possibility that some basal pseudosuchians such as phytosaurs, aetosaurs, and rauisuchians may have survived into the Triassic, especially given our poor control on the determination of the Triassic-Jurassic boundary in non-marine strata. Obviously crocodylomorphs make it through and we have no evidence for an abrupt global-wide non-marine extinction event for other pseudosuchians.
The specimen mentioned by Maisch and Kapitzke appears to currently hold the title of the "last phytosaur", but unfortunately it does not provide clear evidence for the survival of this clade past the end-Triassic.
Maisch, M. W. & Kapitzke, M. 2010. A presumably marine phytosaur (Reptilia: Archosauria) from the pre-planorbis beds (Hettangian) of England. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 257: 373–379.
Abstract: A mandibular fragment of a longirostrine archosaur is decribed from the lowermost Jurassic (pre-planorbis beds, lowermost Hettangian) of Watchet, Somerset, England. The specimen is compared to both marine crocodilians (Thalattosuchia) and phytosaurs, groups which are either unknown (Thalattosuchia) or only doubtfully represented (Phytosauria) in lowermost Jurassic strata so far. The specimen shows striking morphological similarity to the Late Triassic phytosaur Mystriosuchus, but differs from known teleosaurid and metriorhynchid thalattosuchians. It is consequently
determined as aff. Mystriosuchus. It supports previous assumptions that phytosaurs crossed the Triassic-Jurassic boundary, at least in Europe. It also provides additional evidence that at least some phytosaurs, particularly the longirostrine forms, may have been facultative marine animals. The persistence of amphibious, piscivorous, longirostrine phytosaurs in the earliest Jurassic of Europe may have hampered the distribution of the ecologically similar teleosaurids, which are not known from strata that are older than the latest Sinemurian to date.
However, as Randall Irmis (who also informed me of this paper) reminded me, this is non-sensical regarding this specimen as the base of the Jurassic is presently defined by the first appearance of Psiloceras. Thus the phytosaur bearing strata are latest Triassic in age and not Jurassic.
I'm not adverse to the possibility that some basal pseudosuchians such as phytosaurs, aetosaurs, and rauisuchians may have survived into the Triassic, especially given our poor control on the determination of the Triassic-Jurassic boundary in non-marine strata. Obviously crocodylomorphs make it through and we have no evidence for an abrupt global-wide non-marine extinction event for other pseudosuchians.
The specimen mentioned by Maisch and Kapitzke appears to currently hold the title of the "last phytosaur", but unfortunately it does not provide clear evidence for the survival of this clade past the end-Triassic.
Maisch, M. W. & Kapitzke, M. 2010. A presumably marine phytosaur (Reptilia: Archosauria) from the pre-planorbis beds (Hettangian) of England. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 257: 373–379.
Abstract: A mandibular fragment of a longirostrine archosaur is decribed from the lowermost Jurassic (pre-planorbis beds, lowermost Hettangian) of Watchet, Somerset, England. The specimen is compared to both marine crocodilians (Thalattosuchia) and phytosaurs, groups which are either unknown (Thalattosuchia) or only doubtfully represented (Phytosauria) in lowermost Jurassic strata so far. The specimen shows striking morphological similarity to the Late Triassic phytosaur Mystriosuchus, but differs from known teleosaurid and metriorhynchid thalattosuchians. It is consequently
determined as aff. Mystriosuchus. It supports previous assumptions that phytosaurs crossed the Triassic-Jurassic boundary, at least in Europe. It also provides additional evidence that at least some phytosaurs, particularly the longirostrine forms, may have been facultative marine animals. The persistence of amphibious, piscivorous, longirostrine phytosaurs in the earliest Jurassic of Europe may have hampered the distribution of the ecologically similar teleosaurids, which are not known from strata that are older than the latest Sinemurian to date.
...and one more from the End-Triassic Event.
Mander, L., Kuerschner, W. M., and J. C. McElwain. 2010. An explanation for conflicting records of Triassic–Jurassic plant diversity. PNAS Early Edition, www.pnas.org/cgi/doi/10.1073/pnas.1004207107. Suppl.files at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1004207107/-/DCSupplemental.
Abstract - Macrofossils (mostly leaves) and sporomorphs (pollen and spores) preserve conflicting records of plant biodiversity during the end-Permian (P-Tr), Triassic–Jurassic (Tr-J), and end-Cretaceous (K-T) mass extinctions. Estimates of diversity loss based on macrofossils are typically much higher than estimates of diversity loss based on sporomorphs. Macrofossils from the Tr-J of East Greenland indicate that standing species richness declined by as much as 85% in the Late Triassic, whereas sporomorph records from the same region, and from elsewhere in Europe, reveal little evidence of such catastrophic diversity loss. To understand this major discrepancy, we have used a new high-resolution dataset of sporomorph assemblages from Astartekløft, East Greenland, to directly compare the macrofossil and sporomorph records of Tr-J plant biodiversity. Our results show that sporomorph assemblages from the Tr-J boundary interval are 10–12% less taxonomically diverse than sporomorph assemblages from the Late Triassic, and that vegetation composition changed rapidly in the boundary interval as a result of emigration and/or extirpation of taxa rather than immigration and/or origination of taxa. An analysis of the representation of different plant groups in the macrofossil and sporomorph records at Astartekløft reveals that reproductively specialized plants, including cycads, bennettites and the seed-fern Lepidopteris are almost absent from the sporomorph record. These results provide a means of reconciling the macrofossil and sporomorph records of Tr-J vegetation change, and may help to understand vegetation change during the P-Tr and K-T mass extinctions and around the Paleocene– Eocene Thermal Maximum.
Abstract - Macrofossils (mostly leaves) and sporomorphs (pollen and spores) preserve conflicting records of plant biodiversity during the end-Permian (P-Tr), Triassic–Jurassic (Tr-J), and end-Cretaceous (K-T) mass extinctions. Estimates of diversity loss based on macrofossils are typically much higher than estimates of diversity loss based on sporomorphs. Macrofossils from the Tr-J of East Greenland indicate that standing species richness declined by as much as 85% in the Late Triassic, whereas sporomorph records from the same region, and from elsewhere in Europe, reveal little evidence of such catastrophic diversity loss. To understand this major discrepancy, we have used a new high-resolution dataset of sporomorph assemblages from Astartekløft, East Greenland, to directly compare the macrofossil and sporomorph records of Tr-J plant biodiversity. Our results show that sporomorph assemblages from the Tr-J boundary interval are 10–12% less taxonomically diverse than sporomorph assemblages from the Late Triassic, and that vegetation composition changed rapidly in the boundary interval as a result of emigration and/or extirpation of taxa rather than immigration and/or origination of taxa. An analysis of the representation of different plant groups in the macrofossil and sporomorph records at Astartekløft reveals that reproductively specialized plants, including cycads, bennettites and the seed-fern Lepidopteris are almost absent from the sporomorph record. These results provide a means of reconciling the macrofossil and sporomorph records of Tr-J vegetation change, and may help to understand vegetation change during the P-Tr and K-T mass extinctions and around the Paleocene– Eocene Thermal Maximum.
The End-Triassic Extinction Event is Really Popular Right Now....
here is another new paper...
Paris, G., V. Beaumont, A. Bartolini, M.-E. Clémence, S. Gardin, and K. Page. 2010. Nitrogen isotope record of a perturbed paleoecosystem in the aftermath of the end-Triassic crisis, Doniford section, SW England, Geochemistry, Geophysics, Geosystems 11, Q08021, doi:10.1029/2010GC003161.
Abstract - The Triassic-Jurassic transition (TJ) is characterized by successive perturbations of the carbon cycle during a time of biotic disruption as recorded by the carbon isotopic composition of organic matter (δ13Corg). The nitrogen isotopic composition of sedimentary organic matter (δ15Norg) constitutes a key parameter to explore the functioning of the ecosystem during carbon cycle perturbations and biological crises, because it provide information on seawater redox conditions and/or nutrient cycling. Here we report the first continuous δ15Norg record across the TJ transition at the Doniford Bay section (Bristol Channel Basin, UK), combined with δ13Corg, kerogen typology and carbon (δ13Cmin) and oxygen (δ18Omin) isotopic composition of bulk carbonates. The end Triassic is characterized by a major negative excursion both in δ13Corg and δ13Cmin, very low TOC (Total Organic Carbon, wt%) and high δ15Norg values, associated with a sea level lowstand. A second δ13Corg negative excursion occurs during the lower Hettangian. This interval is characterized by phases of carbonate production increase alternated with phases of exceptional accumulations of type I organic matter (up to 12%) associated with lower δ15Norg and δ13Corg. This alternation likely reflects a succession of nutrient input increase to the basin leading to enhanced productivity and eutrophication, which promoted a primary production driven by organic-walled prokaryotic organisms. The following OM export increase generates anaerobic conditions within the basin. These events occur between periods of relatively good seawater column ventilation and nutrient recycling boosting the carbonate producer recovery. Ecosystems remain perturbed in the Bristol Channel Basin during the aftermath of the end-Triassic crisis.
Paris, G., V. Beaumont, A. Bartolini, M.-E. Clémence, S. Gardin, and K. Page. 2010. Nitrogen isotope record of a perturbed paleoecosystem in the aftermath of the end-Triassic crisis, Doniford section, SW England, Geochemistry, Geophysics, Geosystems 11, Q08021, doi:10.1029/2010GC003161.
Abstract - The Triassic-Jurassic transition (TJ) is characterized by successive perturbations of the carbon cycle during a time of biotic disruption as recorded by the carbon isotopic composition of organic matter (δ13Corg). The nitrogen isotopic composition of sedimentary organic matter (δ15Norg) constitutes a key parameter to explore the functioning of the ecosystem during carbon cycle perturbations and biological crises, because it provide information on seawater redox conditions and/or nutrient cycling. Here we report the first continuous δ15Norg record across the TJ transition at the Doniford Bay section (Bristol Channel Basin, UK), combined with δ13Corg, kerogen typology and carbon (δ13Cmin) and oxygen (δ18Omin) isotopic composition of bulk carbonates. The end Triassic is characterized by a major negative excursion both in δ13Corg and δ13Cmin, very low TOC (Total Organic Carbon, wt%) and high δ15Norg values, associated with a sea level lowstand. A second δ13Corg negative excursion occurs during the lower Hettangian. This interval is characterized by phases of carbonate production increase alternated with phases of exceptional accumulations of type I organic matter (up to 12%) associated with lower δ15Norg and δ13Corg. This alternation likely reflects a succession of nutrient input increase to the basin leading to enhanced productivity and eutrophication, which promoted a primary production driven by organic-walled prokaryotic organisms. The following OM export increase generates anaerobic conditions within the basin. These events occur between periods of relatively good seawater column ventilation and nutrient recycling boosting the carbonate producer recovery. Ecosystems remain perturbed in the Bristol Channel Basin during the aftermath of the end-Triassic crisis.
No Single Unambiguous Global End-Triassic Spore Spike
Bonis, N. R., Ruhl, M., and W. M. Kuerschner. 2010. Milankovitch-scale palynological turnover across the Triassic–Jurassic transition at St. Audrie’s Bay, SW UK. Journal of the Geological Society, London 167:877–888. doi: 10.1144/0016-76492009-141.
Abstract - A high-resolution palynological study of the Triassic–Jurassic boundary in the St. Audrie’s Bay section revealed a palynofloral transition interval with four pronounced spore peaks in the Lilstock Formation. Regular cyclic increases in palynomorph concentrations can be linked with periods of increased runoff, and correspond to the orbital eccentricity cycle. Spore peaks can be related to precession-induced variations in monsoon strength. An implication is that the initial carbon isotope excursion lasted for at least 20 ka. Emergence during deposition of the Cotham Member had an influence on one of the peaks, which is dominated by spore-producing pioneer plants (e.g. horsetails and liverworts). There is no compelling evidence of a global end-Triassic spore spike that, by analogy with the K–T boundary fern spike, could be related to a catastrophic mass extinction event. Climate change is a more plausible mechanism to explain the increased amount of spores.
Abstract - A high-resolution palynological study of the Triassic–Jurassic boundary in the St. Audrie’s Bay section revealed a palynofloral transition interval with four pronounced spore peaks in the Lilstock Formation. Regular cyclic increases in palynomorph concentrations can be linked with periods of increased runoff, and correspond to the orbital eccentricity cycle. Spore peaks can be related to precession-induced variations in monsoon strength. An implication is that the initial carbon isotope excursion lasted for at least 20 ka. Emergence during deposition of the Cotham Member had an influence on one of the peaks, which is dominated by spore-producing pioneer plants (e.g. horsetails and liverworts). There is no compelling evidence of a global end-Triassic spore spike that, by analogy with the K–T boundary fern spike, could be related to a catastrophic mass extinction event. Climate change is a more plausible mechanism to explain the increased amount of spores.
Insights into North American Mesozoic Paleogeography and Paleotectonics
Dickinson, W. R., and G. E. Gehrels. 2010. Insights into North American Paleogeography and Paleotectonics from U–Pb ages of detrital zircons in Mesozoic strata of the Colorado Plateau, USA. International Journal of Earth Sciences 99:1247–1265.
Abstract - Individual U–Pb ages for 5,655 detrital zircons (DZ) in 61 sandstone samples from Mesozoic strata of the Colorado Plateau and nearby areas provide insights into paleogeographic relations across the interior of North America and the paleotectonic evolution of North American continental margins. Pre-Mesozoic DZ grains derived either directly, or ultimately through sediment recycling, from distant sources in eastern North America are more abundant than DZ grains derived from the nearby Cordilleran magmatic arc of western North America. Sediment dispersal patterns included Triassic fluvial transport of detritus westward from the Ouachita orogen uplifted along the northern flank of rift highlands precursor to the oceanic Gulf of Mexico, Jurassic eolian transport southward into widespread ergs from deflation of floodplains of transcontinental paleorivers with headwaters in pre-Atlantic Appalachian highlands, and Jurassic-Cretaceous recycling of eolianite DZ from retroarc Sevier thrust sheets and from sedimentary cover of the Mogollon paleohighlands flanking the Border rift system.
Abstract - Individual U–Pb ages for 5,655 detrital zircons (DZ) in 61 sandstone samples from Mesozoic strata of the Colorado Plateau and nearby areas provide insights into paleogeographic relations across the interior of North America and the paleotectonic evolution of North American continental margins. Pre-Mesozoic DZ grains derived either directly, or ultimately through sediment recycling, from distant sources in eastern North America are more abundant than DZ grains derived from the nearby Cordilleran magmatic arc of western North America. Sediment dispersal patterns included Triassic fluvial transport of detritus westward from the Ouachita orogen uplifted along the northern flank of rift highlands precursor to the oceanic Gulf of Mexico, Jurassic eolian transport southward into widespread ergs from deflation of floodplains of transcontinental paleorivers with headwaters in pre-Atlantic Appalachian highlands, and Jurassic-Cretaceous recycling of eolianite DZ from retroarc Sevier thrust sheets and from sedimentary cover of the Mogollon paleohighlands flanking the Border rift system.
Increased fire activity at the Triassic/Jurassic Boundary Due to Climate Driven Floral Change
Belcher, C. M, Mander, L., Rein, G., Jervis, F. X., Haworth, M., Hesselbo, S. P., Glasspool, I. J., and J. C. McElwain. 2010. Increased fire activity at the Triassic/Jurassic boundary in Greenland due to climate-driven floral change. Nature Geoscience 3:426-429.
Abstract - One of the largest mass extinctions of the past 600 million years (Myr) occurred 200 Myr ago, at the Triassic/Jurassic boundary. The major floral and faunal turnovers have been linked to a marked increase in atmospheric carbon dioxide levels, probably resulting from massive volcanism in the Central Atlantic Magmatic Province. Future climate change predictions suggest that fire activity may increase, in part because higher global temperatures are thought to increase storminess. Here we use palaeontological reconstructions of the fossil flora from East Greenland to assess forest
flammability along with records of fossil charcoal preserved in the rocks to show that fire activity increased markedly across the Triassic/Jurassic boundary. We find a fivefold increase in the abundance of fossil charcoal in the earliest Jurassic, which we attribute to a climate-driven shift from a prevalence of broad-leaved taxa to a predominantly narrow leaved assemblage. Our fire calorimetry experiments show that narrow leaf morphologies are more flammable than broad leaved morphologies.We suggest that the warming associated with increased atmospheric carbon dioxide levels favoured a dominance of narrow-leaved plants, which, coupled with more frequent lightening strikes, led to an increase in fire activity at the Triassic/Jurassic boundary.
Abstract - One of the largest mass extinctions of the past 600 million years (Myr) occurred 200 Myr ago, at the Triassic/Jurassic boundary. The major floral and faunal turnovers have been linked to a marked increase in atmospheric carbon dioxide levels, probably resulting from massive volcanism in the Central Atlantic Magmatic Province. Future climate change predictions suggest that fire activity may increase, in part because higher global temperatures are thought to increase storminess. Here we use palaeontological reconstructions of the fossil flora from East Greenland to assess forest
flammability along with records of fossil charcoal preserved in the rocks to show that fire activity increased markedly across the Triassic/Jurassic boundary. We find a fivefold increase in the abundance of fossil charcoal in the earliest Jurassic, which we attribute to a climate-driven shift from a prevalence of broad-leaved taxa to a predominantly narrow leaved assemblage. Our fire calorimetry experiments show that narrow leaf morphologies are more flammable than broad leaved morphologies.We suggest that the warming associated with increased atmospheric carbon dioxide levels favoured a dominance of narrow-leaved plants, which, coupled with more frequent lightening strikes, led to an increase in fire activity at the Triassic/Jurassic boundary.
What I am Currently Reading
I appear to be on an late 19th - early 20th century paleontology fieldwork kick right now regarding the books I am reading. I just finished Paul Brinkman's "The Second Jurassic Dinosaur Rush" book, which I found to be an enjoyable history of collecting Jurassic dinosaurs from the western U.S. by several institutions. At times I found it was difficult to follow the chronological order of the work being done, but overall the book is a solid offering of this important time in American vertebrate paleontology. For more see Brian Switek's recent review.
I am now starting "Bone Hunters in Patagonia" following John Bell Hatcher's work collecting fossil vertebrates in South America during the Princeton University expeditions of 1896-1899. This is supposedly an absolutely amazing narrative of an amazing collecting trip and I hope I enjoy it thoroughly because...
the next book in the stack is "Barnum Brown: the man who discovered Tyrannosaurus rex" by Lowell Dingus and Mark Norell. Several colleagues have told me that this is an excellent book. I had actually started reading this book earlier in the summer and was enjoying it immensely, but stopped to read Paul Brinkman's book when it came out. Reading Paul's book got me very interested in John Bell Hatcher and thus I've found myself reading "Bone Hunters in Patagonia" before going back to the Barnum Brown book. I hope I'm not making a mistake here.
Overall, from what I have seen so far these are three great books covering the work of many great American early paleontologists.
I am now starting "Bone Hunters in Patagonia" following John Bell Hatcher's work collecting fossil vertebrates in South America during the Princeton University expeditions of 1896-1899. This is supposedly an absolutely amazing narrative of an amazing collecting trip and I hope I enjoy it thoroughly because...
the next book in the stack is "Barnum Brown: the man who discovered Tyrannosaurus rex" by Lowell Dingus and Mark Norell. Several colleagues have told me that this is an excellent book. I had actually started reading this book earlier in the summer and was enjoying it immensely, but stopped to read Paul Brinkman's book when it came out. Reading Paul's book got me very interested in John Bell Hatcher and thus I've found myself reading "Bone Hunters in Patagonia" before going back to the Barnum Brown book. I hope I'm not making a mistake here.
Overall, from what I have seen so far these are three great books covering the work of many great American early paleontologists.
Early Triassic Archosaur-dominated Footprint Assemblage from Morocco
Klein, H., Voigt, S., Hminna, A., Saber, H., Schneider, J., and D. Hmich. 2010. Early Triassic Archosaur-Dominated Footprint Assemblage from the Argana Basin (Western High Atlas, Morocco). Ichnos 17:1–13. DOI: 10.1080/10420940.2010.510030
Abstract - An assemblage of abundant and well-preserved tetrapod footprints has been discovered in the Tanamert Member (T3) of the Triassic Timezgadiouine Formation (Argana basin, western High Atlas, Morocco). It is the first fossil record from T3. Surfaces from different localities show a uniform tetrapod ichnofauna that consists of chirotherian and small lacertoid forms. The chirotherians are assigned to the plexus Protochirotherium—Synaptichnium, their trackmakers interpreted as basal archosaurs. The lacertoid imprints show close affinities with Rhynchosauroides and may reflect archosauromorphs or lepidosauromorphs. Protochirotherium—Synaptichnium assemblages are characteristic of the Early Triassic and were known previously only from units of this age in central Europe. Biostratigraphically, the European record implies a wide-spread pre-Anisian Protochirotherium—Synaptichnium dominated assemblage preceding the first appearance of Chirotherium barthii near the Olenekian-
Anisian boundary. The stratigraphic position of T3 between Late Permian (uppermost T2) and Middle Triassic (T4) and the European correlatives suggest an Early Triassic age of this unit. It is the first record of Early Triassic continental deposits in Morocco. The surfaces from T3 open up perspectives for further contributions to ecology, biogeography and locomotion of early archosaurs. Furthermore, excellent outcrops and quality of footprint preservation in the Argana basin offer a potential for clarification of ichnotaxonomic and biostratigraphic issues.
Abstract - An assemblage of abundant and well-preserved tetrapod footprints has been discovered in the Tanamert Member (T3) of the Triassic Timezgadiouine Formation (Argana basin, western High Atlas, Morocco). It is the first fossil record from T3. Surfaces from different localities show a uniform tetrapod ichnofauna that consists of chirotherian and small lacertoid forms. The chirotherians are assigned to the plexus Protochirotherium—Synaptichnium, their trackmakers interpreted as basal archosaurs. The lacertoid imprints show close affinities with Rhynchosauroides and may reflect archosauromorphs or lepidosauromorphs. Protochirotherium—Synaptichnium assemblages are characteristic of the Early Triassic and were known previously only from units of this age in central Europe. Biostratigraphically, the European record implies a wide-spread pre-Anisian Protochirotherium—Synaptichnium dominated assemblage preceding the first appearance of Chirotherium barthii near the Olenekian-
Anisian boundary. The stratigraphic position of T3 between Late Permian (uppermost T2) and Middle Triassic (T4) and the European correlatives suggest an Early Triassic age of this unit. It is the first record of Early Triassic continental deposits in Morocco. The surfaces from T3 open up perspectives for further contributions to ecology, biogeography and locomotion of early archosaurs. Furthermore, excellent outcrops and quality of footprint preservation in the Argana basin offer a potential for clarification of ichnotaxonomic and biostratigraphic issues.
Subscribe to:
Posts (Atom)