Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...
Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...
Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...
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58 ADVANCES IN PALAEOICHTHYOLOGY<br />
University of Queensl<strong>and</strong>, Brisbane, Queensl<strong>and</strong>, Australia. All previous numbers of<br />
type specimens have been changed in the collections of the Institute of Geology at<br />
Tallinn Technical University during the process of creating the computerised database<br />
(for Lophosteus see Appendix 1).<br />
Systematic description<br />
OSTEICHTHYES Huxley, 1880<br />
LOPHOSTEIFORMES Gross, 1969<br />
LOPHOSTEIDAE Gross, 1969<br />
Diagnosis (after Gross 1969): Osteichthyan fishes with rhombic scales that have a keel<br />
on the inner side, but lacking peg on dorsal margin (sometimes broad based “peg”);<br />
different sculpture on scales (with ridges) <strong>and</strong> head bones (with star-like tubercles);<br />
ridges formed by dentine (orthodentine) on bony base.<br />
Included genera: Lophosteus P<strong>and</strong>er 1856.<br />
Lophosteus P<strong>and</strong>er, 1856<br />
Type species: Lophosteus superbus P<strong>and</strong>er 1856.<br />
Geographic distribution: Arctic Canada, Baltic region, Central Urals, E-Australia,<br />
Timan-Pechora region.<br />
Time: Ludlow-Pridoli, Late Silurian – Lochkovian, Early Devonian.<br />
Diagnosis (after Gross 1969): Rhombic scales with broad based “peg”; free field of<br />
scales covered with elevated, obliquely arranged ridges which are widely separated.<br />
Ridges can be overgrown during size increase, but they rarely form a continuous dentine<br />
layer. They bear ridgelets oblique to the crest. – Long symmetrical spines triangular in<br />
cross-section without cavity <strong>and</strong> proximal with a smooth marginal area; ridges r<strong>un</strong><br />
parallel to its length, <strong>and</strong> are sometimes fused to a median ridge; posterior side furrowlike<br />
proximally whereas arched distally. Some asymmetrical long <strong>and</strong> flattened spines<br />
present. – Bones with ridge-like or star-like tubercles. Sensory lines in the form of open<br />
furrows on the bones.<br />
Included species: Lophosteus superbus P<strong>and</strong>er, 1856; Lophosteus cf. superbus Burrow<br />
<strong>and</strong> Turner, 2000; Lophosteus canadensis n. sp.; Lophosteus connexus Märss, 1986;<br />
Lophosteus incrementus Burrow, 1995; Lophosteus ohesaarensis n. sp.; Lophosteus<br />
uralensis n. sp.; Lophosteus sp. indet. Turner, 2000.<br />
Remarks: Species are distinguished mainly on the arrangement of ridgelets. The<br />
important characters are the angle between crest (= the highest line on the ridge) <strong>and</strong><br />
ridgelets (= small ridges on the sides of the ridges), <strong>and</strong> the posterior extension of the<br />
ridges (= raised structures on the scale).