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Abstract

Ischnacanthus gracilis (Egerton, 1861), the only ischnacanthiform acanthodian from the Lochkovian Lower

Old Red Sandstone of Scotland, is known from hundreds of specimens in institutional collections worldwide.

Despite this relative abundance, morphology and histology of its skeletal elements have rarely been investigated.

Surface details of spines, dental elements, and scales are often not visible in specimens because they are

usually split through the middle. We have examined a broad size range of fish, from 35 mm to 250 mm long.

Several intact (not split) specimens have been collected in recent years and acid-prepared to show fine details of

the dermal and dental elements. We have also used scanning electron microscopy of scales, jaws and dental elements,

denticles and fin spines, and serial thin sectioning of articulated specimens, to document their structure.

Some of our notable observations include: identification of ventral lateral lines, double-layered subtessellate

calcified cartilage forming the jaws, and the probable occurrence of extraoral tricuspid denticles on the jaws

of most fish. Examination of the size range, body proportions and dentition of institutional specimens gives no

support for recognising more than one species in the Midland Valley localities.

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Authors and Affiliations

Michael Newman
ORCID: ORCID
Carole J. Burrow
den Blaauwen Jan
Jones Roger
Davidson Robert
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Abstract

The Lower Devonian (Emsian) and Middle Devonian of Belarus contain assemblages of biostratigraphically useful faunal and floral microremains. Surface deposits are few, with most material being derived from borehole cores. Acanthodian scales are particularly numerous and comparison with scales from other regions of the Old Red Sandstone continent (Laurussia), specifically the Orcadian Basin of Scotland, the Baltic Region, Spitsbergen, and Severnaya Zemlya have demonstrated a lot of synonymy of acanthodian species between these areas. This is especially the case between Belarus, the Orcadian Basin and the Baltic Region, which has allowed us to produce an interregional biostratigraphic scheme, as well as to postulate marine connection routes between these areas. The acanthodian biostratigraphy of Belarus is particularly important as it is associated with spores and marine invertebrates, so giving the potential of more detailed correlations across not only the Old Red Sandstone continent, but elsewhere in the Devonian world. We also demonstrate that differences in preservation (e.g., wear and how articulated a specimen is) is one of the main reasons for synonymy.
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Authors and Affiliations

Dmitry P. Plax
1
Michael Newman
2
ORCID: ORCID

  1. Belarusian National Technical University (BNTU), Nezavisimosti Avenue 65, 220013 Minsk, Republic of Belarus
  2. Vine Lodge, Vine Road, Johnston, Haverfordwest, SA62 3NZ Pembrokeshire, United Kingdom

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