The so-called 'Atholville Beds' (Dineley and Williams 1968), exposed at Campbellton and Atholville, have been examined by paleontologists since 1881 and have yielded ostracoderms, arthrodires, acanthodians
and chondrichthyans (Whiteaves 1881, 1889; Woodward 1889, 1892; Traquair 1890, 1893).
Meanwhile, some acanthodian
species turned out to be primitive sharks, while others were relatives of the common ancestor of sharks and bony fishes.
Unfortunately, identifying the specific taxa that produced them is not possible, but their association with various fossils from acanthodian
, actinopterygian, sarcopterygian, and rhipidistian (crossopterygian) fish suggests that any of these are potential sources of the coprolites and nonspiraled cololites.
biostratigraphy and interregional correlations of the Devonian of the Baltic States, Belarus, Ukraine and Russia // Palaeozoic Vertebrate Biochronology and Global marine/Non-Marine Correlations / A.
The excretions contain material from two types of fish: acanthodians
, which had several long, protruding spines; and palaeoniscoids, which lack external spines.
Joined by Romer in the second week, they found an amazing quantity of fossil vertebrate remains --significant material of acanthodians
, arthrodirans, chondrichthyans, dipnoans, and tetrapodomorph fishes --but it was marine in origin and did not include any tetrapod fossils.
Apart from the dipnoan tooth plates, small acanthodian
scales with deep bases and rhomboid smooth crowns were found in etched limestone residues from the Voskresenskoye quarry.
The other braincase, from a species called Acanthodes, dates to a hundred million years after the Acanthodian
group came into existence, casting most of this period of the group's evolution into shadow.
These remains characterize regional stratigraphic units, with several psammosteid and acanthodian
species being used as index fossils (e.
and an acanthodian
of Gomphonchus sandelensis-type.
assemblages of the Burtnieki Regional Stage (RS) (Fig.
Graptolite biozones are usually the most trusted ones, but we will also analyse the behaviour of biozones based on conodonts and chitinozoans, and also on less 'authoritative' groups of fossils such as ostracodes and 'microvertebrates' (mostly thelodont and acanthodian