Showing posts with label faunal assemblages. Show all posts
Showing posts with label faunal assemblages. Show all posts
Diverse New Microvertebrate Assemblage from the Late Triassic of North Carolina
Heckert, A. B., Mitchell, J. S., Schneider, V. P., and P. E. Olsen. 2012. Diverse New Microvertebrate Assemblage from the Upper Triassic Cumnock Formation, Sanford Subbasin, North Carolina, USA. Journal of Paleontology 86(2): 368-390 doi: http://dx.doi.org/10.1666/11-098.1
Abstract - The Moncure microvertebrate locality in the Cumnock Formation, Sanford sub-basin, North Carolina, dramatically increases the known Late Triassic age vertebrate assemblage from the Deep River Basin. The 50,000 recovered microvertebrate fossils include osteichthyans, amphibians, and numerous lepidosauromorph, archosauriform, and synapsid amniotes. Actinopterygian fossils consist of thousands of scales, teeth, skull, and lower jaw fragments, principally of redfieldiids and semionotids. Non-tetrapod sarcopterygians include the dipnoan Arganodus sp., the first record of lungfish in the Newark Supergroup. Temnospondyls are comparatively rare but the preserved centra, teeth, and skull fragments probably represent small (juvenile) metoposaurids. Two fragmentary teeth are assigned to the unusual reptile Colognathus obscurus (Case). Poorly preserved but intriguing records include acrodont and pleurodont jaw fragments tentatively assigned to lepidosaurs. Among the archosauriform teeth is a taxon distinct from R. callenderi that we assign to Revueltosaurus olseni new combination, a morphotype best assigned to cf. Galtonia, the first Newark Supergroup record of Crosbysaurus sp., and several other archosauriform tooth morphotypes, as well as grooved teeth assigned to the recently named species Uatchitodon schneideri. Synapsids represented by molariform teeth include both “traversodontids” assigned to aff. Boreogomphodon and the “dromatheriid” Microconodon. These records are biogeographically important, with many new records for the Cumnock Formation and/or the Newark Supergroup. In particular, Colognathus, Crosbysaurus, and Uatchitodon are known from basins of Adamanian age in the southwestern U.S.A. These new records include microvertebrate taxa more typical of non-Newark basins (abundant archosauriforms, temnospondyls, lungfish) as well as more typical Newark osteichthyans and synapsid-rich faunal elements.
Why We Don't Find Cynodonts in the Chinle Formation
Whiteside, J. H., Grogan, D. S., Olsen, P. E., and D. V. Kent. 2011. Climatically driven biogeographic provinces of Late Triassic tropical Pangea. PNAS Published online before print May 13, 2011,
doi: 10.1073/pnas.1102473108 [supplemental info]
Abstract - Although continents were coalesced into the single landmass Pangea, Late Triassic terrestrial tetrapod assemblages are surprisingly provincial. In eastern North America, we show that assemblages dominated by traversodont cynodonts are restricted to a humid 6° equatorial swath that persisted for over 20 million years characterized by “semiprecessional” (approximately 10,000-y) climatic fluctuations reflected in stable carbon isotopes and sedimentary facies in lacustrine strata. More arid regions from 5–20°N preserve procolophonid-dominated faunal assemblages associated with a much stronger expression of approximately 20,000-y climatic cycles. In the absence of geographic barriers, we hypothesize that these variations in the climatic expression of astronomical forcing produced latitudinal climatic zones that sorted terrestrial vertebrate taxa, perhaps by excretory physiology, into distinct biogeographic provinces tracking latitude, not geographic position, as the proto-North American plate translated northward. Although the early Mesozoic is usually assumed to be characterized by globally distributed land animal communities due to of a lack of geographic barriers, strong provinciality was actually the norm, and nearly global communities were present only after times of massive ecological disruptions.
doi: 10.1073/pnas.1102473108 [supplemental info]
Abstract - Although continents were coalesced into the single landmass Pangea, Late Triassic terrestrial tetrapod assemblages are surprisingly provincial. In eastern North America, we show that assemblages dominated by traversodont cynodonts are restricted to a humid 6° equatorial swath that persisted for over 20 million years characterized by “semiprecessional” (approximately 10,000-y) climatic fluctuations reflected in stable carbon isotopes and sedimentary facies in lacustrine strata. More arid regions from 5–20°N preserve procolophonid-dominated faunal assemblages associated with a much stronger expression of approximately 20,000-y climatic cycles. In the absence of geographic barriers, we hypothesize that these variations in the climatic expression of astronomical forcing produced latitudinal climatic zones that sorted terrestrial vertebrate taxa, perhaps by excretory physiology, into distinct biogeographic provinces tracking latitude, not geographic position, as the proto-North American plate translated northward. Although the early Mesozoic is usually assumed to be characterized by globally distributed land animal communities due to of a lack of geographic barriers, strong provinciality was actually the norm, and nearly global communities were present only after times of massive ecological disruptions.
No Permian-Triassic Boundary Tetrapod Fauna Preserved in South America
Modesto, S. P. and J. Botha-Brink. 2010. Problems of correlation of South African and South American tetrapod faunas across the Permian–Triassic boundary. Journal of South African Earth Sciences 57:242-248. doi:10.1016/j.jafrearsci.2009.08.004
Abstract - The best record of continental tetrapod faunas crossing the Permo–Triassic boundary (PTB) is found in the Karoo Basin of South Africa. Similar records are not known elsewhere among the former Gondwanan land masses, but it was recently proposed on the basis of palaeontological evidence that the Buena Vista Formation of Uruguay preserves a South American record of continental PTB tetrapods. The Buena Vista Formation was previously correlated to the Lower Triassic (Olenekian) Sanga do Cabral Formation of Brazil on the basis of lithostratigraphic evidence, but recent collecting in the former unit has produced a tetrapod fauna that is distinct to that documented for the latter. The unequivocal tetrapod fossils that have been described thus far from the Buena Vista Formation include indeterminate mastodonsaurid temnospondyls, a plagiosauroid temnospondyl, and a procolophonid reptile. The temnospondyls belong to Triassic groups, whereas the procolophonid is allied most closely with Early Triassic taxa from the Karoo Basin. We conclude that there is no compelling palaeontological evidence for placing any part of the Buena Vista Formation in the Permian. A precise placement of the Buena Vista Formation in the Triassic on the basis of its tetrapod fauna is not possible at this time. Accordingly, the Karoo Basin of South Africa remains the only Gondwanan basin that records a PTB tetrapod fauna.
Abstract - The best record of continental tetrapod faunas crossing the Permo–Triassic boundary (PTB) is found in the Karoo Basin of South Africa. Similar records are not known elsewhere among the former Gondwanan land masses, but it was recently proposed on the basis of palaeontological evidence that the Buena Vista Formation of Uruguay preserves a South American record of continental PTB tetrapods. The Buena Vista Formation was previously correlated to the Lower Triassic (Olenekian) Sanga do Cabral Formation of Brazil on the basis of lithostratigraphic evidence, but recent collecting in the former unit has produced a tetrapod fauna that is distinct to that documented for the latter. The unequivocal tetrapod fossils that have been described thus far from the Buena Vista Formation include indeterminate mastodonsaurid temnospondyls, a plagiosauroid temnospondyl, and a procolophonid reptile. The temnospondyls belong to Triassic groups, whereas the procolophonid is allied most closely with Early Triassic taxa from the Karoo Basin. We conclude that there is no compelling palaeontological evidence for placing any part of the Buena Vista Formation in the Permian. A precise placement of the Buena Vista Formation in the Triassic on the basis of its tetrapod fauna is not possible at this time. Accordingly, the Karoo Basin of South Africa remains the only Gondwanan basin that records a PTB tetrapod fauna.
Latest Literature
Klembara, J., and J. Welman. 2009. The anatomy of the palatoquadrate in the Lower Triassic Proterosuchus fergusi (Reptilia, Archosauromorpha) and its morphological transformation within the archosauriform clade. Acta Zoologica 90(3):275-284. doi: 10.1111/j.1463-6395.2008.00358.x.
ABSTRACT- The anatomy of the palatoquadrate ossifications of the Lower Triassic archosauromorph Proterosuchus fergusi from South Africa is described. It consists of two ossifications, the epipterygoid and the quadrate, which were joined by cartilage in life. The margins of the cartilage are clearly indicated by ridges and grooves on the dorsal surface of the pterygoid. The epipterygoid ossification consists of two structures: the anteroposteriorly expanded basal portion and, dorsally from it, an extending, slender, ascending process. From the anterior margin of the basal portion of the epipterygoid, a plate-like structure, herein called the lamina epipterygoidea anteromedialis, extends anteromedially to form the anterolateral wall of the cavum epiptericum. Comparisons with the similarly constructed embryonal and adult epipterygoid components of Sphenodon punctatus show that the anteromedial lamina of the epipterygoid of P. fergusi is an additional component of the epipterygoid of this species and that this lamina is absent in the former species. However, a structure in a topologically similar position to the anteromedial lamina of the epipterygoid of P. fergusi is present in the palatoquadrate of Alligator mississippiensis. In the latter species, the structure is called the lamina palatoquadrati anterior; it ossifies in membrane and forms the dorsolateral cover of the huge trigeminal ganglion. It is hypothesized here that the anteromedial lamina of the epipterygoid of P. fergusi and the anterior lamina of the palatoquadrate of A. mississippiensis are most probably homologous structures and are present in both the basal and one of the crown taxa of the archosauromorph clade, respectively.
Renesto, S., Spielmann, J.A., and S.G. Lucas. 2009. The oldest record of drepanosaurids (Reptilia, Diapsida) from the Late Triassic (Adamanian Placerias Quarry, Arizona, USA) and the stratigraphic range of the Drepanosauridae. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 252(3):315-325. doi: 10.1127/0077-7749/2009/0252-0315.
ABSTRACT- Previous detailed descriptions of relatively complete drepanosaurid material make it possible to recognize isolated drepanosaurid elements from other localities. The identification of isolated elements from the USA and Great Britain extended the geographical distribution of the group and encouraged a review of Triassic collections for characteristic elements of this family. In this paper, isolated vertebrae previously described as problematic reptiles from the famous Placerias Quarry, near St. Johns, Arizona, USA are re-identified as drepanosaurids. These specimens represent the oldest occurrence of this family, which is earliest Adamanian.
This last paper is interesting as it again demonstates the homogeneous nature of the Chinle Formation faunal assemblages through the lowest to highest fossiliferous exposures. Thus with the exception of dicynodonts the Placerias Quarry, which is stratigraphically low, and contains dicynodonts, possesses pretty much the same faunal elements as the much higher quarries around Ghost Ranch New Mexico (Canjilon, Snyder, Hayden, Coelophysis), which lack dicynodonts. Thus you get phytosaurs, aetosaurs, rauisuchians, poposaurs, Vancleavea, crocodylomorphs, coelophysoids, lagerpetids, and now drepanosaurids throughout the Chinle section. Taxa and abundances in some groups (e.g., metoposaurs) change but the general faunal composition does not. Still, given that the Chinle Formation is now mostly restricted to the Middle and Late Norian (and possibly some of the Rhaetian) this is not too surprising.
ABSTRACT- The anatomy of the palatoquadrate ossifications of the Lower Triassic archosauromorph Proterosuchus fergusi from South Africa is described. It consists of two ossifications, the epipterygoid and the quadrate, which were joined by cartilage in life. The margins of the cartilage are clearly indicated by ridges and grooves on the dorsal surface of the pterygoid. The epipterygoid ossification consists of two structures: the anteroposteriorly expanded basal portion and, dorsally from it, an extending, slender, ascending process. From the anterior margin of the basal portion of the epipterygoid, a plate-like structure, herein called the lamina epipterygoidea anteromedialis, extends anteromedially to form the anterolateral wall of the cavum epiptericum. Comparisons with the similarly constructed embryonal and adult epipterygoid components of Sphenodon punctatus show that the anteromedial lamina of the epipterygoid of P. fergusi is an additional component of the epipterygoid of this species and that this lamina is absent in the former species. However, a structure in a topologically similar position to the anteromedial lamina of the epipterygoid of P. fergusi is present in the palatoquadrate of Alligator mississippiensis. In the latter species, the structure is called the lamina palatoquadrati anterior; it ossifies in membrane and forms the dorsolateral cover of the huge trigeminal ganglion. It is hypothesized here that the anteromedial lamina of the epipterygoid of P. fergusi and the anterior lamina of the palatoquadrate of A. mississippiensis are most probably homologous structures and are present in both the basal and one of the crown taxa of the archosauromorph clade, respectively.
Renesto, S., Spielmann, J.A., and S.G. Lucas. 2009. The oldest record of drepanosaurids (Reptilia, Diapsida) from the Late Triassic (Adamanian Placerias Quarry, Arizona, USA) and the stratigraphic range of the Drepanosauridae. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 252(3):315-325. doi: 10.1127/0077-7749/2009/0252-0315.
ABSTRACT- Previous detailed descriptions of relatively complete drepanosaurid material make it possible to recognize isolated drepanosaurid elements from other localities. The identification of isolated elements from the USA and Great Britain extended the geographical distribution of the group and encouraged a review of Triassic collections for characteristic elements of this family. In this paper, isolated vertebrae previously described as problematic reptiles from the famous Placerias Quarry, near St. Johns, Arizona, USA are re-identified as drepanosaurids. These specimens represent the oldest occurrence of this family, which is earliest Adamanian.
This last paper is interesting as it again demonstates the homogeneous nature of the Chinle Formation faunal assemblages through the lowest to highest fossiliferous exposures. Thus with the exception of dicynodonts the Placerias Quarry, which is stratigraphically low, and contains dicynodonts, possesses pretty much the same faunal elements as the much higher quarries around Ghost Ranch New Mexico (Canjilon, Snyder, Hayden, Coelophysis), which lack dicynodonts. Thus you get phytosaurs, aetosaurs, rauisuchians, poposaurs, Vancleavea, crocodylomorphs, coelophysoids, lagerpetids, and now drepanosaurids throughout the Chinle section. Taxa and abundances in some groups (e.g., metoposaurs) change but the general faunal composition does not. Still, given that the Chinle Formation is now mostly restricted to the Middle and Late Norian (and possibly some of the Rhaetian) this is not too surprising.
The vertebrate assemblage of the Late Triassic Canjilon Quarry and the importance of apomorphy based assemblage comparisons
Nesbitt, S.J., and M.R. Stocker. 2008. The vertebrate assemblage of the Late Triassic Canjilon Quarry (Northern New Mexico, USA) and the importance of apomorphy based assemblage comparisons. Journal of Vertebrate Paleontology 28:1063-1072.
ABSTRACT—The Upper Triassic Canjilon Quarry in northern New Mexico preserves a vertebrate assemblage typical of the Norian Stage of North America. Although dominated in relative abundance by the phytosaur Pseudopalatus and the aetosaur Typothorax, a more diverse assemblage of smaller forms was previously reported. Additions to the Canjilon
Quarry vertebrate assemblage are critically reviewed and described using an apomorphy-based method for assigning taxa. An apomorphy-based approach for compiling and comparing assemblages allows each taxonomic assignment to be a testable hypothesis. Fragmentary yet diagnostic elements that may not be assignable to a species-level taxon can be assigned to a larger clade and thus provide useful information. Additionally, each taxon listed in the assemblage must be tied to a diagnostic specimen listed with a museum specimen number. Using this method for the Canjilon Quarry, we establish the presence of an assemblage that is more similar to other vertebrate quarries near Ghost Ranch than previously thought. The Canjilon Quarry assemblage is restricted to vertebrates from UCMP locality V2816. Vertebrate material housed at the Museum of Comparative Zoology, Harvard, which was reported from the Canjilon Quarry, was not collected from UCMP V2816 but from a nearby locality.
The Canjilon Quarry from the Petrified Forest Member (Chinle Formation) of New Mexico was mainly worked by Charles Camp and crew (University of California, Berkeley) in 1933 and produced a wealth of fossil vertebrate material, most notably numerous skeletons (including a suite of skulls) of the phytosaur Pseudopalatus. You can get more information on the Canjilon Quarry, including an extremely detailed reconstruction of the 1933 excavation from field notes, here and here. Of course the main point and overall importance of this paper is the discussion on using apomorphy based identifications when creating faunal lists.
ABSTRACT—The Upper Triassic Canjilon Quarry in northern New Mexico preserves a vertebrate assemblage typical of the Norian Stage of North America. Although dominated in relative abundance by the phytosaur Pseudopalatus and the aetosaur Typothorax, a more diverse assemblage of smaller forms was previously reported. Additions to the Canjilon
Quarry vertebrate assemblage are critically reviewed and described using an apomorphy-based method for assigning taxa. An apomorphy-based approach for compiling and comparing assemblages allows each taxonomic assignment to be a testable hypothesis. Fragmentary yet diagnostic elements that may not be assignable to a species-level taxon can be assigned to a larger clade and thus provide useful information. Additionally, each taxon listed in the assemblage must be tied to a diagnostic specimen listed with a museum specimen number. Using this method for the Canjilon Quarry, we establish the presence of an assemblage that is more similar to other vertebrate quarries near Ghost Ranch than previously thought. The Canjilon Quarry assemblage is restricted to vertebrates from UCMP locality V2816. Vertebrate material housed at the Museum of Comparative Zoology, Harvard, which was reported from the Canjilon Quarry, was not collected from UCMP V2816 but from a nearby locality.
The Canjilon Quarry from the Petrified Forest Member (Chinle Formation) of New Mexico was mainly worked by Charles Camp and crew (University of California, Berkeley) in 1933 and produced a wealth of fossil vertebrate material, most notably numerous skeletons (including a suite of skulls) of the phytosaur Pseudopalatus. You can get more information on the Canjilon Quarry, including an extremely detailed reconstruction of the 1933 excavation from field notes, here and here. Of course the main point and overall importance of this paper is the discussion on using apomorphy based identifications when creating faunal lists.
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