An isolated pterygoid tooth plate of a lungfish from the Lower Devonian (Lochkovian–Pragian) of V... more An isolated pterygoid tooth plate of a lungfish from the Lower Devonian (Lochkovian–Pragian) of Vietnam is described. The material is negatively preserved and lacks associated jawbones to assign a reliable taxonomic status and phylogenetic position. The tooth plate is composed of five main tooth rows radially arranged, separated by several interrow denticles and flanked medially and laterally by smaller accessory rows and by a denticulated posterolateral field. The general structure of the tooth plate displays predominantly primitive traits similar to those known in the contemporaneous Diabolepis from China. However, as opposed to Diabolepis, the tooth plate possesses fewer and more organized rows of teeth, a condition typical of more derived dipnoans. Comparisons with other primitive forms indicate that the arrangement of teeth into distinct rows with a lack of interrow denticles is typical of juvenile specimens of Diabolepis, which may imply that the presence of discrete tooth rows in more derived lungfish taxa is a product of paedomorphosis. Given its puzzling mix of primitive and derived features, this new pterygoid tooth plate can be tentatively assigned to a previously known lungfish prearticular from northern Vietnam, although with caution. Pending the finding of more complete remains, the condition shown by this new form might indicate that the establishment of the modern lungfish tooth plate organization occurred no later than the Pragian.
On Cat Ba Island in northeastern Vietnam, the Devonian to Carboniferous (D-C) transition consists... more On Cat Ba Island in northeastern Vietnam, the Devonian to Carboniferous (D-C) transition consists mainly of ramp carbonates intercalated with black shale beds (Beds 1 to 176) in the Pho Han Formation and is one of the few records of the D-C transition of the eastern Paleotethys. The three main facies of the sequence are Facies 1 (alternations of whitish gray to gray limestone and marl), Facies 2 (calcirudite, Bed 115b), and Facies 3 (alternations of dark gray limestone and organic-carbon-rich black shale, Beds 115c-120 and 126-129). The latest Famennian (Siphonodella praesulcata Subzone) conodont assemblage of S. praesulcata, Palmatolepis gracilis, Palmatolepis sigmoidalis, and Rhodalepis polylophodontiformis was recognized in Beds 113-115c. Beds 105-112 commonly contain Palmatolepis expansa, P. gracilis, and P. sigmoidalis. Bed 119 yielded a basal Carboniferous index conodont Siphonodella sulcata. In Beds 116-118, solenoporids such as Pseudochaetetes elliotti and Parachaetetes sp. were characteristic species in organic-carbon-rich dark gray limestone. Facies 1 is characterized by bioclastic, peloidal, and intraclastic grainstone and packstone containing massive normal grading and cross-laminations, and is interpreted to represent deep ramp carbonates above storm wave base. Facies 2 is represented by typical lag deposits overlying a transgressive surface. Facies 3 comprises organiccarbon-rich black shale and minor scour-filling bioclastic, peloidal, and intraclastic packstone, and may represent a marginal basin plain environment surrounding a carbonate ramp. The alternations of organic-carbon-rich black shale and dark gray packstone (Facies 3) show no evidence of bioturbation and have high TOC contents (0.18-5.73 wt.%). A minor succession within the transgressive lag deposits (from Bed 115b of Facies 2 to Beds 115c-120 in the lower part of Facies 3) is equivalent to the Hangenberg Black Shale (s. l.) in the middle part of the Siphonodella praesulcata to Siphonodella sulcata zones, because Beds 115b-120 characterized by no evidence of bioturbation and high TOC contents are interpreted to be accumulated in anoxic to dysoxic conditions.
Upper Devonian carbonates deposited through the Frasnian/Famennian (F/F) stage boundary in the Xo... more Upper Devonian carbonates deposited through the Frasnian/Famennian (F/F) stage boundary in the Xom Nha Formation, Central Vietnam, were studied. The section is mainly composed of fossiliferous, brecciated, and laminated limestone beds, while shale beds occur in a subordinate number. Microfacies generally suggests a hemipelagic setting on an outer shelf environment with low sedimentation rates. A sediment accumulation rate of 0.217 cm/kyrs for this section is calculated. The Xom Nha section does not exhibit characteristic black shales or black limestones through the F/F boundary, but instead shows a similar lithology in comparison to other F/F sections in Southeast Asia. The carbonates yielded abundant conodonts, which represent mainly cosmopolitan species but the section differs from most sections in Europe in showing relatively high numbers of Palmatolepis linguiformis species. Deposition through the F/F boundary interval reported here for the Xom Nha section appears to have occurr...
The new synchrotron-radiation circular-dichroism (SRCD) endstation on the UV-visible synchrotron ... more The new synchrotron-radiation circular-dichroism (SRCD) endstation on the UV-visible synchrotron beamline DISCO has been commissioned at the SOLEIL synchrotron. The design has been focused on preservation of a high degree of linear polarization at high flux and moderate resolving power covering the vacuum ultraviolet to visible spectral range (125-600 nm). The beam dimensions have been set to 4 mm  4 mm at 1 nm bandwidth for lower sample degradation. The nitrogen-purged sample chamber fits three types of sample holders accommodating conventional round cell mounting, automated rotation of the samples, as well as a microfluidic setup. Automated temperaturecontrolled data collection on microvolumes is now available to the biology and chemistry communities. Macromolecules including membrane proteins, soluble proteins, bio-nanotubes, sugars, DNA and RNAs are now routinely investigated.
An isolated pterygoid tooth plate of a lungfish from the Lower Devonian (Lochkovian–Pragian) of V... more An isolated pterygoid tooth plate of a lungfish from the Lower Devonian (Lochkovian–Pragian) of Vietnam is described. The material is negatively preserved and lacks associated jawbones to assign a reliable taxonomic status and phylogenetic position. The tooth plate is composed of five main tooth rows radially arranged, separated by several interrow denticles and flanked medially and laterally by smaller accessory rows and by a denticulated posterolateral field. The general structure of the tooth plate displays predominantly primitive traits similar to those known in the contemporaneous Diabolepis from China. However, as opposed to Diabolepis, the tooth plate possesses fewer and more organized rows of teeth, a condition typical of more derived dipnoans. Comparisons with other primitive forms indicate that the arrangement of teeth into distinct rows with a lack of interrow denticles is typical of juvenile specimens of Diabolepis, which may imply that the presence of discrete tooth rows in more derived lungfish taxa is a product of paedomorphosis. Given its puzzling mix of primitive and derived features, this new pterygoid tooth plate can be tentatively assigned to a previously known lungfish prearticular from northern Vietnam, although with caution. Pending the finding of more complete remains, the condition shown by this new form might indicate that the establishment of the modern lungfish tooth plate organization occurred no later than the Pragian.
On Cat Ba Island in northeastern Vietnam, the Devonian to Carboniferous (D-C) transition consists... more On Cat Ba Island in northeastern Vietnam, the Devonian to Carboniferous (D-C) transition consists mainly of ramp carbonates intercalated with black shale beds (Beds 1 to 176) in the Pho Han Formation and is one of the few records of the D-C transition of the eastern Paleotethys. The three main facies of the sequence are Facies 1 (alternations of whitish gray to gray limestone and marl), Facies 2 (calcirudite, Bed 115b), and Facies 3 (alternations of dark gray limestone and organic-carbon-rich black shale, Beds 115c-120 and 126-129). The latest Famennian (Siphonodella praesulcata Subzone) conodont assemblage of S. praesulcata, Palmatolepis gracilis, Palmatolepis sigmoidalis, and Rhodalepis polylophodontiformis was recognized in Beds 113-115c. Beds 105-112 commonly contain Palmatolepis expansa, P. gracilis, and P. sigmoidalis. Bed 119 yielded a basal Carboniferous index conodont Siphonodella sulcata. In Beds 116-118, solenoporids such as Pseudochaetetes elliotti and Parachaetetes sp. were characteristic species in organic-carbon-rich dark gray limestone. Facies 1 is characterized by bioclastic, peloidal, and intraclastic grainstone and packstone containing massive normal grading and cross-laminations, and is interpreted to represent deep ramp carbonates above storm wave base. Facies 2 is represented by typical lag deposits overlying a transgressive surface. Facies 3 comprises organiccarbon-rich black shale and minor scour-filling bioclastic, peloidal, and intraclastic packstone, and may represent a marginal basin plain environment surrounding a carbonate ramp. The alternations of organic-carbon-rich black shale and dark gray packstone (Facies 3) show no evidence of bioturbation and have high TOC contents (0.18-5.73 wt.%). A minor succession within the transgressive lag deposits (from Bed 115b of Facies 2 to Beds 115c-120 in the lower part of Facies 3) is equivalent to the Hangenberg Black Shale (s. l.) in the middle part of the Siphonodella praesulcata to Siphonodella sulcata zones, because Beds 115b-120 characterized by no evidence of bioturbation and high TOC contents are interpreted to be accumulated in anoxic to dysoxic conditions.
Upper Devonian carbonates deposited through the Frasnian/Famennian (F/F) stage boundary in the Xo... more Upper Devonian carbonates deposited through the Frasnian/Famennian (F/F) stage boundary in the Xom Nha Formation, Central Vietnam, were studied. The section is mainly composed of fossiliferous, brecciated, and laminated limestone beds, while shale beds occur in a subordinate number. Microfacies generally suggests a hemipelagic setting on an outer shelf environment with low sedimentation rates. A sediment accumulation rate of 0.217 cm/kyrs for this section is calculated. The Xom Nha section does not exhibit characteristic black shales or black limestones through the F/F boundary, but instead shows a similar lithology in comparison to other F/F sections in Southeast Asia. The carbonates yielded abundant conodonts, which represent mainly cosmopolitan species but the section differs from most sections in Europe in showing relatively high numbers of Palmatolepis linguiformis species. Deposition through the F/F boundary interval reported here for the Xom Nha section appears to have occurr...
The new synchrotron-radiation circular-dichroism (SRCD) endstation on the UV-visible synchrotron ... more The new synchrotron-radiation circular-dichroism (SRCD) endstation on the UV-visible synchrotron beamline DISCO has been commissioned at the SOLEIL synchrotron. The design has been focused on preservation of a high degree of linear polarization at high flux and moderate resolving power covering the vacuum ultraviolet to visible spectral range (125-600 nm). The beam dimensions have been set to 4 mm  4 mm at 1 nm bandwidth for lower sample degradation. The nitrogen-purged sample chamber fits three types of sample holders accommodating conventional round cell mounting, automated rotation of the samples, as well as a microfluidic setup. Automated temperaturecontrolled data collection on microvolumes is now available to the biology and chemistry communities. Macromolecules including membrane proteins, soluble proteins, bio-nanotubes, sugars, DNA and RNAs are now routinely investigated.
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