Middle Ordovician (Chazyan) Sea-Level Changes and the Evolution of the Ordovician Conodont Genus Cahabagnathus Bergström, 1983

Leslie, Stephen A.; Lehnert, Oliver

doi:10.1666/0022-3360(2005)079[1131:mocsca]2.0.co;2

Cited by 12 publications

(4 citation statements)

References 11 publications

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“…Prior to the early 2000s many wide spread North American lithostratigraphic units such as the Trenton Group, Martinsburg Formation, Decorah Shale, Ottossee Formation were correlated globally with the Middle Ordovician (e.g., Twenhofel, 1938;Ross, 1963Ross, , 1984Karklins, 1983a). Based on chemostratigraphy of bentonites and revised biostratigraphic correlation (Bergström et al, 2004), many of these units are now correlated globally with Late Ordovician (Sandbian, or even Katian) or straddle the Middle-Upper Ordovician boundary (Leslie and Lehnert, 2005).…”

Section: North American "Middle Ordovician" Correlation Issuesmentioning

confidence: 99%

The last phylum: Occupation of Bryozoa morpho-ecospace (colony growth habits) during the early phase of the Great Ordovician Biodiversification Event

Hageman

Ernst

2019

Palaeogeography, Palaeoclimatology, Palaeoecology

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Section: North American "Middle Ordovician" Correlation Issuesmentioning

confidence: 99%

The last phylum: Occupation of Bryozoa morpho-ecospace (colony growth habits) during the early phase of the Great Ordovician Biodiversification Event

Hageman

Ernst

2019

Palaeogeography, Palaeoclimatology, Palaeoecology

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“…Conodonts were distributed into two biogeographic realms in the Ordovician, known as the North American Midcontinent realm and the North Atlantic realm, which provide parallel zonations for use in biostratigraphy Bergström, 1976, 1984;Webby et al, 2004). Conodonts assigned to the North American Midcontinent realm are generally associated with low-latitude, warm-water environments (Leslie and Lehnert, 2005), whereas North Atlantic realm conodonts occurred in higher lati tudes or deeper-water regions with cooler water temperature. In some sections where both shallow-and deeper-water facies are present, both the North American Midcontinent and North Atlantic faunas are found (Harris et al, 1979).…”

Section: Conodont Biostratigraphymentioning

confidence: 99%

Calibration of a conodont apatite-based Ordovician⁸⁷Sr/⁸⁶Sr curve to biostratigraphy and geochronology: Implications for stratigraphic resolution

Saltzman

Edwards

Leslie

et al. 2014

Geological Society of America Bulletin

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The Ordovician 87 Sr/ 86 Sr isotope seawater curve is well established and shows a decreasing trend until the mid-Katian. However, uncertainties in calibration of this curve to biostratigraphy and geochronology have made it diffi cult to determine how the rates of 87 Sr/ 86 Sr decrease may have varied, which has implications for both the stratigraphic resolution possible using Sr isotope stratigraphy and efforts to model the effects of Ordovician geologic events. We measured 87 Sr/ 86 Sr in conodont apatite in North American Ordovician sections that are well studied for conodont biostratigraphy, primarily in Nevada, Oklahoma, the Appalachian region, and Ohio Valley. Our results indicate that conodont apatite may provide an accurate medium for Sr isotope stratigraphy and strengthen previous reports that point toward a signifi cant increase in the rate of fall in seawater 87 Sr/ 86 Sr during the Middle Ordovician Darriwilian Stage. Our 87 Sr/ 86 Sr results suggest that Sr isotope stratigraphy will be most useful as a high-resolution tool for global correlation in the mid-Darriwilian to mid-Sandbian, when the maximum rate of fall in 87 Sr/ 86 Sr is estimated at ~5.0-10.0 × 10 -5 per m.y. Variable preservation of conodont elements limits the precision for individual stratigraphic horizons. Replicate conodont analyses from the same sample differ by an average of ~4.0 × 10 -5 (the 2σ standard deviation is 6.2 × 10 -5 ), which in the best case scenario allows for subdivision of Ordovician time intervals characterized by the highest rates of fall in 87 Sr/ 86 Sr at a maximum resolution of ~0.5-1.0 m.y. Links between the increased rate of fall in 87 Sr/ 86 Sr beginning in the mid-late Darriwilian (Phragmodus polonicus to Pygodus serra conodont zones) and geologic events continue to be investigated, but the coincidence with a long-term rise in sea level (Sauk-Tippecanoe megasequence boundary) and tectonic events (Taconic orogeny) in North America provides a plausible explanation for the changing magnitude and 87 Sr/ 86 Sr of the riverine Sr fl ux to the oceans.

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“…Unavoidably, most of the phylogeny appears thus as represented by ‘ghost lineages.’ This is a false presentation of evolutionary reality. The extensive literature on conodont evolution shows many continuous series of populations, each subdivided into several chronospecies, or even genera (reviewed by Dzik 1999, 2006; also Leslie & Lehnert 1999, 2005).…”

Section: Methods Of Inferencementioning

confidence: 99%

Evolutionary roots of the conodonts with increased number of elements in the apparatus

Dzik¹

2015

Earth and Environmental Science Transactions of the Royal Socie

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Four kinds of robust elements have been recognised in Amorphognathus quinquiradiatus Moskalenko, 1977 (in Kanygin et al. 1977) from the early Late Ordovician of Siberia, indicating that at least 17 elements were present in the apparatus, one of them similar to the P1 element of the Early Silurian Distomodus. The new generic name Moskalenkodus is proposed for these conodonts with a pterospathodontid-like S series element morphology. This implies that the related Distomodus, Pterospathodus and Gamachignathus lineages had a long cryptic evolutionary history, probably ranging back to the early Ordovician, when they split from the lineage of Icriodella, having a duplicated M location in common. The balognathid Promissum, with a 19-element apparatus, may have shared ancestry with Icriodella in Ordovician high latitudes, with Sagittodontina, Lenodus, Trapezognathus and Phragmodus as possible connecting links. The pattern of the unbalanced contribution of Baltoniodus element types to samples suggests that duplication of M and P2 series elements may have been an early event in the evolution of balognathids. The proposed scenario implies a profound transformation of the mouth region in the evolution of conodonts. The probable original state was a chaetognath-like arrangement of coniform elements; all paired and of relatively uniform morphology. This was modified at the origin of protopanderodontids by the introduction of a medial S0 element, which resulted in the separation of the exposed unit of M and S series elements from the P series elements hidden in the throat. A rotation of the S series elements to an almost horizontal position in early prioniodontids may have promoted duplication of the M element pair. In Gamachignathus, Icriodella and Pterospathodus lineages, these elements are differentiated morphologically. Subsequent anteriorward bending of the P element series caused duplication of the balognathid P2 element pair, but they remained undifferentiated, even in the otherwise elaborate Promissum. The whole clade of conodonts with supernumerary element pairs in the apparatus has its roots in high latitudes of the Ordovician.

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Middle Ordovician (Chazyan) Sea-Level Changes and the Evolution of the Ordovician Conodont Genus Cahabagnathus Bergström, 1983

Cited by 12 publications

References 11 publications

The last phylum: Occupation of Bryozoa morpho-ecospace (colony growth habits) during the early phase of the Great Ordovician Biodiversification Event

The last phylum: Occupation of Bryozoa morpho-ecospace (colony growth habits) during the early phase of the Great Ordovician Biodiversification Event

Calibration of a conodont apatite-based Ordovician⁸⁷Sr/⁸⁶Sr curve to biostratigraphy and geochronology: Implications for stratigraphic resolution

Evolutionary roots of the conodonts with increased number of elements in the apparatus

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Middle Ordovician (Chazyan) Sea-Level Changes and the Evolution of the Ordovician Conodont Genus Cahabagnathus Bergström, 1983

Cited by 12 publications

References 11 publications

The last phylum: Occupation of Bryozoa morpho-ecospace (colony growth habits) during the early phase of the Great Ordovician Biodiversification Event

The last phylum: Occupation of Bryozoa morpho-ecospace (colony growth habits) during the early phase of the Great Ordovician Biodiversification Event

Calibration of a conodont apatite-based Ordovician87Sr/86Sr curve to biostratigraphy and geochronology: Implications for stratigraphic resolution

Evolutionary roots of the conodonts with increased number of elements in the apparatus

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Calibration of a conodont apatite-based Ordovician⁸⁷Sr/⁸⁶Sr curve to biostratigraphy and geochronology: Implications for stratigraphic resolution