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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138<br />
ADVANCES IN PALAEOICHTHYOLOGY<br />
Fig. 7. Poracanthodes sulcatus sp. nov. SEM micrographs of scales (A-B), crown views, anterior<br />
upwards, <strong>and</strong> thin section photos (C-J). A, holotype, LIGG 25-A-2613; B, LIGG 25-A-<br />
2614; C-F, vertical longitudinal section of scale. Thin section 3776. C, general view; D, detail<br />
of the anterior crown part <strong>and</strong> base apex at higher magnification; E, magnified detail of the<br />
posterior crown part <strong>and</strong> base; F, detail of scale primordium at higher magnification; G-J, vertical<br />
transverse section of scale. Thin section 3790. G, general view; H, the right part of crown at<br />
higher magnification; I, the left part of crown <strong>and</strong> the adjacent base portion; J, detail of the base<br />
apex at higher magnification. Lūžņi-4 borehole, depth 176.5 m. Přidoli, Jūra Regional Stage,<br />
Lūžņi Beds of the Targale Formation. Abbreviations: arcpc, arcade pore canal, avc, ascending<br />
vascular canal, b, bone, d, dentine, oc, osteocyte cavity, pc, superficial pore canal, rpc, radial<br />
pore canal, rvc, radial vascular canal, sf, Sharpey’s fibre traces. Scale bars: 0.1 mm.<br />
to open on the surface. The arcade pore canals (Fig. 7 H-I) are just as wide as the radial<br />
canals <strong>and</strong> connect the latter <strong>and</strong> superficial ones to form the complicated net piercing<br />
the crown tissue. The high-pyramidal base is composed of densely lamellar cellular<br />
bone incorporating varying numbers of osteocytes <strong>and</strong> pierced by long traces of Shapey’s<br />
fibres. The osteocytes are densest in the apex of the pyramid, where they are largest <strong>and</strong>