scholarly journals II - The Acanthodian fishes

1937 ◽  
Vol 228 (549) ◽  
pp. 49-146 ◽  
Keyword(s):  
Lower Devonian ◽  
Good Evidence ◽  
Caudal Fin ◽  
Red Sandstone ◽  
The World ◽  
Upper Silurian ◽  
Devonian Age ◽  
Fin Spines

The Acanthodian fishes form one of the most sharply demarcated and recognizable groups of vertebrate fossils. Their characteristic squamation of square, exceedingly minute ganoid scales, and the fact that all the fins except the caudal fin are supported by large anterior spines, distinguish them sharply from all other fishes, and enable even fragmentary specimens to be recognized without doubt. They are worldwide in distribution, and their range in tim e is thus known with considerable certainty. The first fragments, attributed on very good evidence to the group, are isolated fin spines, found in Upper Silurian rocks perhaps not earlier than the Downtonian, which seem to be identical with those found in complete fishes of Lower Devonian age. The group was more varied in structure and played a larger part in the world in Lower Devonian times than at any other period. Even in the Middle Old Red Sandstone the range in structure had been reduced, and by Carboniferous times very few forms remained.

scholarly journals The Cosheston Group (Lower Old Red Sandstone) in southwest Wales: age, correlation and palaeobotanical significance

1998 ◽  
Vol 135 (3) ◽  
pp. 397-412 ◽  
Author(s):  
C. H. WELLMAN ◽  
R. G. THOMAS ◽  
D. EDWARDS ◽  
P. KENRICK
Keyword(s):  
Lower Devonian ◽  
New Age ◽  
Early Devonian ◽  
Red Sandstone ◽  
South Wales ◽  
Upper Silurian ◽  
Devonian Age ◽  
Sandstone Facies

Upper Silurian–Lower Devonian ‘Lower Old Red Sandstone’ facies deposits cropping out in southwest Wales are poorly age-constrained and difficult to correlate. Spore assemblages have been recovered from sequences of these deposits belonging to the lower part of the Cosheston Group. The spore assemblages are equated with the breconensis–zavallatus and polygonalis–emsiensis Spore Assemblage Biozones and indicate an early Devonian age (late Gedinnian (late Lochkovian)–Siegenian (Pragian)). The new biostratigraphical data enable correlation of the lower part of the Cosheston Group with the Senni Beds from the main outcrop of the Lower Devonian in South Wales and the Welsh Borderland. In addition, the new age data and stratigraphical correlation place important plant megafossil assemblages from the Cosheston Group and Senni Beds in a more secure stratigraphical framework, thus facilitating comparisons with other Lower Devonian plant megafossil assemblages and enhancing palaeobotanical understanding. Evidence from palynofacies analysis supports sedimentological interpretations which suggest that the ‘Lower Old Red Sandstone’ facies deposits belonging to the Cosheston Group accumulated in a continental fluviatile environment.

Synchronology

1985 ◽  
Vol 309 (1138) ◽  
pp. 11-27 ◽  
Keyword(s):  
Sea Level ◽  
Quantitative Methods ◽  
Lower Devonian ◽  
Practical Interest ◽  
Radiometric Dating ◽  
Vertebrate Evolution ◽  
Significant Evidence ◽  
Red Sandstone ◽  
Level Curves ◽  
Upper Silurian

Radiometric dating cannot as yet approach the resolution obtainable in Silurian and Devonian biostratigraphy. Progress towards achievement of a global standard for the Wenlock and Emsian interval (against which evolution and environment must be seen) is reviewed. In biostratigraphical correlation with this standard certain groups are especially useful. Correlation between marine Upper Silurian and Lower Devonian rocks and their equivalents in the Old Red Sandstone magnafacies presents particular problems and yet the latter provides significant evidence of plant and vertebrate evolution at this time. The recognition of widespread physical events such as volcanic episodes may sometimes prove useful. Sea level curves seldom provide a precise synchronology not achievable through biostratigraphy. Quantitative methods of correlation are so far of theoretical rather than practical interest.

Vertebrate remains from Upper Silurian – Lower Devonian beds of Hall Land, North Greenland

1999 ◽  
pp. 1-80 ◽  
Author(s):  
Henning Blom
Keyword(s):  
Lower Devonian ◽  
Age Determination ◽  
Early Devonian ◽  
Marine Strata ◽  
South Of Siberia ◽  
Minor Part ◽  
Upper Silurian ◽  
A Minor ◽  
Devonian Age ◽  
North Greenland

NOTE: This monograph was published in a former series of GEUS Bulletin. Please use the original series name when citing this monograph, for example: Blom, H. (1999). Vertebrate remains from Upper Silurian – Lower Devonian beds of Hall Land, North Greenland. Geology of Greenland Survey Bulletin, 182, 1-80. https://doi.org/10.34194/ggub.v182.5126 _______________ Vertebrate microscopic remains of twenty-six taxa of thelodonts, heterostracans, osteostracans, anaspids, acanthodians and chondrichthyans are described from limestone beds in two localities of Late Silurian - Early Devonian age of the Chester Bjerg Formation, Hall Land, North Greenland. The limestone beds form a minor part of a monotonous calcareous sandstone-siltstone-mudstone sequence at the top of the Franklinian Basin succession.Stratigraphical recognition using several thelodont and acanthodian taxa, supported by regional geological and structural trends, suggests a Silurian-Devonian boundary interval between beds of the Halls Grav and Monument localities. This possible resolution of the previous problematic correlation between the two distant sections of monotonous nature demonstrates the potential biostratigraphic utility of thelodonts in Silurian -Devonian marine successions.The Chester Bjerg Formation thelodont assemblage is unique with several new endemic taxa, but Loganellia cf. L. tuvaensis is very similar to the type material of the Tuva region south of Siberia, Russia and indicates a Late Silurian age for the beds of the Halls Grav locality. Canonia cf. C. grossi suggests an Early Devonian age for the Monument locality, since Canonia is so far only found in Lower Devonian marine strata of Arctic Canada and Russia. Fragments of cosmopolitan acanthodian genera such as Poracanthodes, Gomphonchus and Nostolepis are found together with heterostracans, osteostracans, anaspids and chondrichthyans at both localities but do not give a more exact age determination than Late Silurian - Early Devonian. New thelodont taxa are Loganellia almgreeni sp. nov., Paralogania foliala sp. nov., Praetrilogania grabion gen. et sp. nov. and Thulolepis striaspina gen. et sp. nov. Nostolepis halli sp. nov. is a new acanthodian species.

scholarly journals Spines of the stem chondrichthyan Doliodus latispinosus (Whiteaves) comb. nov. from the Lower Devonian of eastern Canada

2017 ◽  
Vol 54 (12) ◽  
pp. 1248-1262 ◽  
Author(s):  
Carole J. Burrow ◽  
Susan Turner ◽  
John G. Maisey ◽  
Sylvain Desbiens ◽  
Randall F. Miller
Keyword(s):  
New Brunswick ◽  
Lower Devonian ◽  
Phylogenetic Position ◽  
Eastern Canada ◽  
Late 19Th Century ◽  
Spine Morphology ◽  
Red Sandstone ◽  
Gaspe Peninsula ◽  
Gaspé Peninsula ◽  
Fin Spines

The higher taxonomic affinities of fin spines from the Lower Devonian (Emsian) Atholville beds, Campbellton Formation, near Campbellton, New Brunswick, Canada, originally identified as Ctenacanthus latispinosus, have been uncertain since they were first described by Whiteaves in the late 19th century. Woodward subsequently referred the species to Climatius, because the isolated Canadian fin spines were similar to those preserved in articulated specimens of Climatius reticulatus from the Lower Old Red Sandstone (Lochkovian) of Scotland. Spines of the same form as the Atholville beds specimens are also found in Emsian mudstones on the Gaspé Peninsula, Québec. One of the fin spine forms appears identical to the pectoral fin spines on an articulated specimen from the Campbellton Formation that has been assigned to the stem chondrichthyan Doliodus problematicus, a taxon erected for isolated diplodont teeth. By comparison with median and paired fin spine morphology on the climatiiform Climatius reticulatus from the Scottish Lower Old Red Sandstone and the spines preserved on the articulated Doliodus, isolated fin spines from Campbellton and several localities on the Gaspé Peninsula are now identified as belonging to Doliodus latispinosus comb. nov. The variety of spine morphotypes recognized—pectoral, prepelvic, prepectoral, and median—support a phylogenetic position within the “acanthodians” rather than “conventionally defined chondrichthyans”.

scholarly journals The lower Devonian flora of the Senni Beds of Monmouthshire and Breconshire

1942 ◽  
Vol 231 (579) ◽  
pp. 131-163 ◽  
Keyword(s):  
Lower Devonian ◽  
Terrestrial Habitat ◽  
Red Sandstone ◽  
Incertae Sedis ◽  
Branch System ◽  
System A ◽  
Large Size ◽  
Devonian Age ◽  
First Time ◽  
A New Species

New fossil localities, of which the most important is Llanover Quarry, are recorded from the Senni Beds of the Lower Old Red Sandstone of Monmouthshire and Breconshire. All the plants so far known from the Senni Beds occur at Llanover and a number are at present only known in Britain from this locality. The plants distinguished and described, in addition to some remains incertae sedis , are: Drepanophycus spinaeformis , cf. Psilophyton princeps, Dawsonites arcuatus, Gosslingia breconensis, Zosterophyllum cf. australianum, Z. llanoveranum n.sp., Zosterophyllum sp., Cooksonia sp., Sporogonites exuberans , Sciadophyton Taeniocrada sp., Prototaxites sp., Nematothallus sp., Pachytheca sp. The remains of Drepanophycus include shoots bearing sporangia and have H-shaped branching in what was probably the lower region of the plant. The remains of a spiny plant of Psilophyton princeps type have a hitherto undescribed fructification in organic connexion with the vegetative shoots. This fructification is quite unlike Dawsonites , of which typical examples also occur. The numerous specimens of Gosslingia have shown that the sporangia were not borne on special fertile branches, as was originally supposed, but on the margins of the regular dorsiventral branch system. A distinction of two subgenera within the genus Zosterophyllum is suggested. Z. cf. australianum belongs to Eu-zosterophyllum with radial spikes. A new species, Z. llanoveranum , has dorsiventral secund spikes of sporangia of the Zosterophyllum type and is placed in the subgenus Platy-zosterophyllum . A second smaller species belonging to this subgenus is also present. Instructive remains of Cooksonia continue this type of plant from the Downtonian to the Senni Beds. Sporogonites , Sciadophyton and Taeniocrada are recorded for the first time from British rocks. Prototaxites and Nematothallus occur along with the vascular land plants, some of the pieces of the former being of large size. Pachytheca is represented in several exposures. The interesting composition of the flora, which is of non-marine and probably terrestrial habitat, is discussed. The flora is of late Lower Devonian age, probably corresponding to the Siegenian of the continental succession. Comparisons are made with similar floras from Scotland and elsewhere.

XV.—On Rhamphodopsis, a Ptyctodont from the Middle Old Red Sandstone of Scotland

1938 ◽  
Vol 59 (2) ◽  
pp. 397-410 ◽  
Author(s):  
D. M. S. Watson
Keyword(s):  
Upper Devonian ◽  
Red Sandstone ◽  
Number Of Teeth ◽  
Devonian Age

In 1858 C. H. Pander described as Ptydodus a number of teeth from Upper Devonian limestones in Russia. His admirable figures of complete teeth and of sections through them established the very chimæroid structure of these bodies. Since that time similar teeth have been repeatedly described, and have served for the establishment of three genera and many species from rocks of Middle and Upper Devonian age.

Notes of a Geologist in Ireland During August and September, 1857

The Geologist ◽  
1858 ◽  
Vol 1 (8) ◽  
pp. 330-335
Author(s):  
W. S. Symonds
Keyword(s):  
Lower Cambrian ◽  
Red Sandstone ◽  
Upper Silurian ◽  
Cover Up

On leaving Dublin, we travelled northwards, for the purpose of examining the carboniferous rocks, and visiting the magnificent collection of fossil-fishes in the museum of the Earl of Enniskillen; we then journeyed south for Killarney and the Dingle district, but as it may be more convenient to the reader to travel geologically, we will reverse the order of our journey, and visit the Upper Silurian and Old Red Sandstone districts before we examine the carboniferous deposits.The lower Cambrian rocks of Wales, of which the Oldhamia-schists of Ireland are believed to be the equivalents, pass upwards by insensible gradations into the Lingula-flags, to which they are altogether conformable. The Lingula-flags are reckoned to be four or five thousand feet thick, and the Llandeilo or Builth-beds, which cover up these, are probably as thick; but geologists are, as yet, uncertain whether they possess in Ireland any true equivalents either of the Lingula-flags or of the Llandeilo and Builth deposits. There are, however, fossiliferous rocks of the Bala and Caradoc age in Ireland similar to those which, in Wales, succeed conformably to the Llandeilo and Builth beds, and they may be examined at Courtown, in the county of Wicklow, and again at Tramore, south of Waterford. They are unconformable to the rocks below, which are undoubtedly Cambrian, and thence, we imagine, has arisen the suspicion that the Lingula-beds and Llandeilo-flags have never been deposited in Ireland, or that if they were, they have been denuded and swept away before the deposition of the Bala or Caradoc strata.

The Plain Inquirer’s Plain Evidence against the Global Skeptical Scenarios

2018 ◽  
Vol 8 (3) ◽  
pp. 208-222 ◽  
Author(s):  
Adam Leite
Keyword(s):  
Good Reason ◽  
Good Evidence ◽  
Epistemic Circularity ◽  
Evil Demon ◽  
The World ◽  
Treatment Considerations ◽  
Limited Demand ◽  
Epistemic Asymmetry ◽  
Background Context ◽  
Rule Out

Penelope Maddy claims that we can have no evidence that we are not being globally deceived by an evil demon. However, Maddy’s Plain Inquirer holds that she has good evidence for a wide variety of claims about the world and her relation to it. She rejects the broadly Cartesian idea that she can’t be entitled to these claims, or have good evidence for them, or know them, unless she can provide a defense of them that starts from nowhere. She likewise rejects the more limited demand for a defense that makes use only of considerations that do not concern the world outside of her mind. She allows that some considerations about the world can be appealed to perfectly appropriately as fully adequate evidence in favor of other considerations about the world. So why can’t the Plain Inquirer rule out global skeptical hypotheses by producing evidence against them that depends upon other considerations about the world? Is there good reason for singling out global skeptical hypotheses such as I am not being deceived by an evil demon as requiring a different kind of treatment? Considerations about epistemic asymmetry and epistemic circularity, as well as Wittgensteinian considerations about the relation between evidence and the real-world and human background context, all lead to the conclusion that there is not.

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