Microfossils and Geochemistry of the Late Devonian Extinction Events in the Appalachian Basin

Numerous silicified and calcareous sclerites of various sizes, recovered from the latest Famennian of Thuringia (Germany), allow the description of the first complete growth series of a blind proetoid trilobite: Drevermannia richteri. In addition, the partial ontogenetic development of Drevermannia antecurvata sp. nov. and undetermined species, Drevermannia sp. 1, are described. The proetoid anaprotaspides, associated with D. richteri, illustrate that a marked increase in larval size occurred prior to the terminal Devonian extinction event. Considering the homogeneity of larval size in older Devonian proetoids, it is interpreted as evidence that the developmental strategy of these trilobites was significantly modified. Though largely speculative, two alternative hypotheses are proposed to explain this modification. Finally, all three ontogenetic sequences show that ocular structures never develop externally in Drevermannia, but also illustrate that the development of optical nerves is not completely lost in this group. This suggests that blindness in the Drevermannia lineage followed a centripetal mode of eye reduction.

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A new species of Hyattechinus (Echinoidea) from the type Devonian of the United Kingdom and implications for the distribution of Devonian proterocidarid echinoids

Geological Magazine ◽

10.1017/s0016756818000109 ◽

2018 ◽

Vol 156 (5) ◽

pp. 801-810 ◽

Cited By ~ 3

Author(s):

JEFFREY R. THOMPSON ◽

TIMOTHY A. M. EWIN

Keyword(s):

New Species ◽

Sea Urchins ◽

Appalachian Basin ◽

Upper Devonian ◽

Late Devonian ◽

New Taxon ◽

The North ◽

Late Palaeozoic ◽

Diversity Dynamics ◽

A New Species

AbstractMany of the most diverse clades of Late Palaeozoic echinoids (sea urchins) originated in the Devonian period. Our understanding of diversity dynamics of these Late Palaeozoic clades are thus informed by new systematic descriptions of some of their earliest members. The Proterocidaridae are a diverse and morphologically distinct clade of stem group echinoids with flattened tests and enlarged adoral pore pairs, which are first known from the Upper Devonian. We herein report on a new species of Hyattechinus, Hyattechinus anglicus n. sp., from the Upper Devonian of the North Devon Basin, Devon, UK. This is the first Devonian Hyattechinus known from outside of the Appalachian Basin, USA, and provides novel information regarding the palaeogeographic and stratigraphic distribution of proterocidarids in Late Devonian times. We additionally update the stratigraphic distribution of Devonian Hyattechinus from the Appalachian Basin, following recent biostratigraphic resolution of their occurrences. Hyattechinus appears to have been present in the Rheic echinoderm fauna during Late Devonian times, and comparison of the palaeoenvironmental setting of Hyattechinus anglicus with that of other Hyattechinus from the Famennian of the Appalachian Basin suggests that the genus may have preferred siliciclastic settings. Furthermore, this new taxon increases the diversity of echinoids from the Upper Devonian of Devon to three species.

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Evidence of wildfires and elevated atmospheric oxygen at the Frasnian–Famennian boundary in New York (USA): Implications for the Late Devonian mass extinction

Geological Society of America Bulletin ◽

10.1130/b35457.1 ◽

2020 ◽

Vol 132 (9-10) ◽

pp. 2043-2054 ◽

Cited By ~ 1

Author(s):

Zeyang Liu ◽

David Selby ◽

Paul C. Hackley ◽

D. Jeffrey Over

Keyword(s):

New York ◽

Mass Extinction ◽

Atmospheric Oxygen ◽

Terrestrial Ecosystems ◽

Atmospheric Composition ◽

Late Devonian ◽

Driving Mechanism ◽

Volcanic Event ◽

Extinction Events ◽

Climate Cooling

Abstract The Devonian Period experienced significant fluctuations of atmospheric oxygen (O2) levels (∼25–13%), for which the extent and timing are debated. Also characteristic of the Devonian Period, at the Frasnian–Famennian (F–F) boundary, is one of the “big five” mass extinction events of the Phanerozoic. Fossilized charcoal (inertinite) provides a record of wildfire events, which in turn can provide insight into the evolution of terrestrial ecosystems and the atmospheric composition. Here, we report organic petrology, programmed pyrolysis analysis, major and trace element analyses, and initial osmium isotope (Osi) stratigraphy from five sections of Upper Devonian (F–F interval) from western New York, USA. These data are discussed to infer evidence of a wildfire event at the F–F boundary. Based on the evidence for a wildfire at the F–F boundary we also provide an estimate of atmospheric O2 levels of ∼23–25% at this interval, which is in agreement with the models that predict elevated pO2 levels during the Late Devonian. This, coupled with our Os isotope records, support the currently published Osi data that lacks any evidence for an extra-terrestrial impact or volcanic event at the F–F interval, and therefore to act as a trigger for the F–F mass extinction. The elevated O2 level at the F–F interval inferred from this study supports the hypothesis that pCO2 drawdown and associated climate cooling may have acted as a driving mechanism of the F–F mass extinction.

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Oceanic δ13C, environmental changes and Carboniferous coral reef development: Records from Tianlin and Ziyun (southern China)

10.5194/egusphere-egu2020-5054 ◽

2020 ◽

Author(s):

Marine Maillet ◽

Elias Samankassou

Keyword(s):

Coral Reef ◽

Coral Reefs ◽

Environmental Conditions ◽

Environmental Changes ◽

Southern China ◽

Ocean Current ◽

Late Devonian ◽

Equatorial Position ◽

Eastern Australia ◽

Devonian Extinction

Metazoan reef builders receded globally during the Carboniferous, after the Late Devonian extinction event, with only few exceptions of coral-bearing bioconstructions reported worldwide. Among the latter, two exceptional extended coral reefs, dated as Late Vis&#233;an&#8211;Serpukhovian and Kasimovian-Gzhelian in age, respectively, were recently reported from southern China. The scarcity of coral buildups worldwide suggests global unfavorable conditions, with specific settings considered to represent refugia. To constrain these environmental conditions, seawater composition is reconstructed using carbon and oxygen isotopes originating from five measured sections located in southern China.The resulting &#948;13C data reveals several environmental changes throughout the Carboniferous attributed to climate changes, ocean current variations, and proliferation of terrestrial plants. During the Late Vis&#233;an-earliest Serpukhovian, the high &#948;13C values (&#732;3&#8240;) are interpreted as recording short-lived glacial events, with the expansion of ice-sheets in South America and eastern Australia. The scarcity of coral reef growth suggests that the cooling acted as an inhibiting factor during this period. Conversely, the development of the exceptional coral reefs in southern China could be explained by the persistence of warm oceanic currents in the epicontinental sea, located in equatorial position. During the Kasimovian-Gzhelian, the gradual &#948;13C positive shift from -0.7 to +4.7&#8240; coincides with a short-lived warming, which should be suitable for the recovery of coral communities. However, in spite of the mild climate, the scarcity of Pennsylvanian coral reef leads to consider other inhibiting factors (e.g. biological competition and aragonite seas). Interestingly, the disappearance of coral reefs in southern China correlates with negative &#948;13C shifts (e.g. Mid-Vis&#233;an, Late Gzhelian), interpreted as related to intensified upwellings.The reconstitution of the Carboniferous environmental conditions documents several factors contributing to the metazoan reef demise and recovery subsequent to the Late Devonian extinction events, and adds to our current knowledge of the longest reef recovery in the Phanerozoic.&#160;&#160;

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