Hercynian high-altitude phenomena in the French Massif Central: tectonic implications

Becq-Giraudon, Jean-François; Christian, Michel; Driessche, Jean Van Den

doi:10.1016/0031-0182(95)00081-x

Cited by 83 publications

(49 citation statements)

References 12 publications

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“…Branchiosaurids are found in central European fossil lakes, which during the Late Carboniferous and Early Permian were located in the Variscian Mountains at an altitude of up to 2000 meters (Becq-Giraudon et al 1996;Boy & Schindler 2000). Most of the lakes that yielded branchiosaurids were very large and deep lakes with up to tens of kilometers in diameter.…”

Section: Discussionmentioning

confidence: 99%

The largest specimen of Apateon and the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae

Fröbisch¹,

Schoch²

2009

Foss. Rec.

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Two distinct developmental trajectories, metamorphosis and neoteny (the retention of larval somatic features in adult animals), have been reported for the small gill-bearing branchiosaurids of the Late Carboniferous and Early Permian of central Europe. Based on a very large specimen of the species Apateon caducus (Ammon, 1889), anatomical features characteristic for the neotenic phenotype of branchiosaurids are described. Large neotenes lack changes that occur during a short phase of transformation into terrestrial adults (metamorphosis), such as ossification of the braincase and palatoquadrate and intercentra, further ossification of the girdles and formation of muscle attachment scars and processes on the limb bones. They also lack a distinct sculpturing of the dermal skull roofing elements with deep polygonal ridges and grooves. Instead, larval somatic features are retained including ossified branchial denticles indicative of open gill slits and accentuated larval-type sculpturing of the dermal skull roof. Large size, high degree of ossification as compared to the larvae, and the presence of uncinate processes on the ribs clearly demonstrate an adult ontogenetic stage. Neotenes remained in the aquatic environment throughout their life and were most likely not capable of effective terrestrial locomotion. The frequency distribution of the two phenotypes in modern salamander populations and the environmental cues that influence the development of them provide a comparative framework for the discussion of the evolution of the two life history pathways in branchiosaurids. doi:<a href="http://dx.doi.org/10.1002/mmng.200800012" target="_blank">10.1002/mmng.200800012</a>

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Section: Discussionmentioning

confidence: 99%

The largest specimen of Apateon and the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae

Fröbisch¹,

Schoch²

2009

Foss. Rec.

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“…Although located in a tropical environment, it has been estimated that the lakes may have been as high as 2000 m above sea level (Becq-Giraudon et al 1996) and were exposed to monsoon weather conditions with pronounced differences in precipitation throughout the year (Patzowsky et al 1991). The high elevation of the lakes may explain why neoteny apparently was the dominant pathway in most of the studied lakes.…”

Section: Neotenymentioning

confidence: 99%

Metamorphosis and Neoteny: Alternative Pathways in an Extinct Amphibian Clade

Schoch¹,

Fröbisch²

2006

Evolution

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Abstract. The Branchiosauridae was a clade of small amphibians from the Permo-Carboniferous with an overall salamander-like appearance. The clade is distinguished by an extraordinary fossil record that comprises hundreds of well-preserved specimens, representing a wide range of ontogenetic stages. Branchiosaurids had external gills and weakly ossified skeletons, and due to this larval appearance their status as neotenic (perennibranchiate) forms has long been accepted. Despite their extensive fossil record large specimens with an adult morphology appeared to be lacking altogether, but recently two adult specimens were identified in a rich sample of Apateon gracilis collected in the 19th century from a locality near Dresden, Saxony. These specimens are unique among branchiosaurids in showing a high level of ossification, including bones that have never been reported in a branchiosaur. These highlight the successive formation of features believed to indicate terrestrial locomotion, as well as feeding on larger prey items. Moreover, these transformations occurred in a small time window (whereas the degree of size increase is used as a proxy of time) and the degree of concentration of developmental events in branchiosaurids is unique among tetrapods outside the lissamphibians. These specimens are compared with large adults of the neotenic branchiosaurid Apateon caducus from the Saar-Nahe Basin, which despite their larger body size lack the features found in the adult A. gracilis specimens. These specimens give new insight into patterns of metamorphosis (morphological transformation) in branchiosaurids that are believed to be correlated to a change of habitat, and clearly show that different life-history pathways comparable to those of modern salamanders were already established in this Paleozoic clade.Key words. Amphibians, Branchiosauridae, development, developmental pathways, evolution, metamorphosis, neoteny, Temnospondyli. The evolutionary origin of metamorphosis in amphibians is still very poorly understood. The three extant clades, salamanders, frogs, and caecilians, reveal widely divergent patterns and processes usually referred to as metamorphosis, and the homology of metamorphosis-related features across these clades is far from clear. During metamorphosis, the remodeling of the skeleton as well as changes in the crucial organ systems have been found to be quite different in the three extant clades (Fox

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“…These molecules would then derive into medium-and heavy-paraffins during pyrolysis. As, the Autun Permian lake was a freshwater one (Becq-Giraudon et al, 1996;Marteau, 1983), it is likely that Pila bibractensis colonies did not had to produce long chain molecules to protect themselves from brackish environmental conditions.…”

Section: The Particular Case Of the Autun Bogheadmentioning

confidence: 99%

Palaeoenvironmental control on primary fluids characteristics of lacustrine source rocks in the Autun Permian Basin (France)

Garel¹,

Béhar²,

Schnyder³

et al. 2017

Bull. Soc. géol. Fr.

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-The Autunian (Late Gzhelian-Sakmarian, ∼295 Ma) of the Autun Basin (Saône-et-Loire, France) is well known for its lacustrine oil-shales and boghead that were exploited during the 19th and 20th centuries. A study of the kerogen geochemistry, palynofacies, hydrocarbon (HC) distribution of pyrolysates and kinetics on these organic-rich sediments gave indications on the control of lacustrine primary fluid characteristics by palaeoenvironmental settings. Palynofacies results have shown a Botryococcus algae dominance in the boghead, whereas the oil-shales were dominated either by a mixing of terrestrial particles and lacustrine phytoplanktonic/bacterial organic matter (OM), or by a lacustrine OM that suffered biodegradation within the water column. During the Autunian, an increasing trend of degraded lacustrine OM concentration is observed in the successive oil-shales. Geochemical and kinetics analyses showed that, except for the boghead, hydrogen index values were < 700 mg/g TOC and activation energies diagram showed multi-energetic profiles, unexpected for such a lacustrine OM. Along with pyrolysates primary fluids ones, these results unraveled two groups of oil-shale samples. On the one hand, samples dominated by well-preserved lacustrine and terrestrial OM produced primary fluids dominated by n-alkanes with (n-C 6 -n-C 14 ) /n-C 14þ n-alkanes ratio depending on the proportion of terrestrial OM. They were only encountered in the three oldest oil-shales. On the other hand, the HC profile of fluids originating from samples dominated by degraded lacustrine OM, which was obtained for the first time in this study, show low n-alkanes concentrations and a relatively prominent hump. These samples were only present in the three youngest oilshale levels. Finally, the boghead showed a link between strong concentration of the Pila genus of Botryococcus algae and a primary fluid dominated by n-C 6 -n-C 14 n-alkanes. By comparing these data with published palaeoenvironmental studies, it appears that the kind of dominant OM, and thus the HC distribution of primary fluids, is controlled by the lake level: a lower depth preventing the settlement of anoxic conditions in the bottom waters, and the subsequent good preservation of the OM. During the Autunian, the lake level decreased, consequence of a reduced tectonic activity and of the beginning of a dryer period. Finally, these changes will have caused a strong decrease of the nutrient influx to the lake, favoring the bloom of Botryococcus algae that accumulated to form the boghead. cinétiques ont montré que, excepté pour le boghead, les valeurs d'index d'hydrogène étaient < 700 mg/g COT et les énergies d'activation montraient des profils pluri-énergétiques, inhabituels pour une MO lacustre. Ajoutés à ceux des fluides primaires de pyrolysats, ces résultats ont mis en évidence deux groupes d'échantillons de schistes-bitumineux. Le premier est marqué par une dominance de la MO lacustre et terrestre bien préservée et produit des fluides primaires dominés par les n-alcanes ave...

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Hercynian high-altitude phenomena in the French Massif Central: tectonic implications

Cited by 83 publications

References 12 publications

The largest specimen of <i>Apateon</i> and the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae

The largest specimen of <i>Apateon</i> and the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae

Metamorphosis and Neoteny: Alternative Pathways in an Extinct Amphibian Clade

Palaeoenvironmental control on primary fluids characteristics of lacustrine source rocks in the Autun Permian Basin (France)

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