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54 ADVANCES IN PALAEOICHTHYOLOGY Fig. 4. Drawings of thin sections given in Fig. 2. Scale bars 0.2 mm. A, C, Trimpleylepis juncta gen. et sp. nov. A, GIT 384-10, Man Brook, upper part of Prídolí Series, Upper Silurian; C, GIT 384-11, Man Brook. B, D. Family Rhyncholepididae Kiær, 1924 gen. et sp. indet., scale, Gardner’s Bank, c. 7 m below Psammosteus Limestone, U. Downton Group, Prídolí, Silurian; B, GIT 385- 13; D, GIT 384-14. E, Trimpleylepis concatenata gen et. sp. nov. GIT 384-12, Ohesaare Borehole, depth 94.32-94.40 m, Saaremaa, Estonia, Upper Ludlow, Upper Silurian. A , C and D are drawings of corresponding scales in external and visceral views which were 1 1 1 thin sectioned. The line across the scale shows approximate position of the section. Abbreviations: d.f.f., diverging of fine fibres; g.l., growth lines; m.v.r., medial visceral rib; ost., osteon; o.v.c., opening of vascular canal; r., sculpture ridge; Sh.f., Sharpey’s fibres; v.c., vascular canal.
C.G.Miller, T. Marss, H. Blom. New anaspid material from Britain and Estonia 55 follows the previous ridge; ridges slightly oblique (Fig. 3J) to perpendicular to the long axis of the scale (Fig. 3I). One specimen with main scale area of chevron-like, continuous ridges crossing whole of preserved part of scale (Fig 3K). Articulation facet visible on most complete scale (Fig. 3I). Single, well-developed, central visceral rib occurs on the smooth lower surface of the scale (Fig. 3L). On two scales, vascular canals exposed where sculpture of the main scale area has been worn away (Figs 3J, K). Histology. Well developed vascular canal system present just below level of the main scale area (Figs 2B, D; 4B, D). Distinct parallel growth lines of compact structure in the visceral rib of one specimen (Figs 2D, 4D). Fine fibres present both in the sculpture ridges and visceral rib. Sharpey’s fibres found in one scale (Figs 2B, 4B). Remarks. Less material was available from Gardner’s Bank than at Man Brook. The Gardner’s Bank scales were also broken but it was easier to make thin sections of them. The broken external surface on one specimen that has now been sectioned (Figs 2D, 3K, 4D) suggests that there were a series of closely spaced fine elements forming each major ridge on the main scale area. These could have been similar to the ridges on Rhyncholepis parvula Kiær, 1924 (Blom et al. fig. 26m) or Schidiosteus mustelensis Pander, 1856 (Blom et al. 2002, fig. 30m). Histological sections (Figs 2B, D; 4B,D) show a well developed vascular canal system that suggest more of a similarity with the rhyncholepidids Rhyncholepis, Silmalepis, Vesikulepis, Schidiosteus or Rytidolepis. One specimen (Fig. 3J) also shows traces of vascular canals in a worn area below the sculpture on the main scale area. Well developed vascular canal systems are consistent with members of the Family Rhyncholepididae, which at present is confined to the late Wenlock to middle Ludlow (Blom et al. 2002). Identification of this material under the Family Rhyncholepididae extends the range of the family to the late Prídolí. More material from Gardner’s Bank is certainly needed before the genus can be decided with any certainty. Conclusions 1. Trimpleylepis gen. nov. is an anaspid that shows similarities to those from the Family Septentrionidae. However, there is some doubt that vascular canals are developed, so at present Trimpleylepis can only tentatively be assigned to this family. 2. Two species have been described; Trimpleylepis juncta gen. et sp. nov. from the Prídolí of the Welsh Borderland at Man Brook and Trimpleylepis concatenata gen. et sp. nov. from the Ludlow of Estonia. 3. Material described from Man Brook extends the range of the genus Silmalepis to Ludlow-latest Prídolí. 4. New material from Gardner’s Bank, Welsh Borderland significantly expands the range of the Family Rhyncholepididae to mid Wenlock-late Prídolí. Acknowledgements. - Illustrations of NHM material figured within remain copyright of the NHM. Sally Young, Natural History Museum, provided useful information about sculptures of Siluro-Devonian vertebrate microremains. Some SEM images were taken in the Centre of Material Research at Tallinn Technical University by Dr. Valdek Mikli. T.M. acknowledges the receipt of an Estonian Science Foundation Grant No. 5726.
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LATVIJAS UNIVERSITĀTES RAKSTI 679.
Page 3 and 4: LATVIJAS UNIVERSITĀTES RAKSTI 679.
Page 5 and 6: Contents Ervīns Lukševičs and Ģ
Page 7 and 8: ACTA UNIVERSITATIS LATVIENSIS, 2004
Page 9 and 10: Ervīns Lukševičs, Ģirts Stinkul
Page 15 and 16: Olga Afanassieva. Microrelief on th
Page 23 and 24: D.K. Elliott, E. Mark-Kurik, E.B. D
Page 47 and 48: C.G.Miller, T. Marss, H. Blom. New
Page 53: C.G.Miller, T. Marss, H. Blom. New
Page 59 and 60: H.-P. Schultze, T. Marss. Revisitin
Page 81 and 82: O.A. Lebedev. A new tetrapod from R
Page 101 and 102: E. Lukševičs, I. Zupiņš. Sedime
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J. Valiukevičius. Silurian acantho
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Ž. Žigaite. New telodont from Tuv
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