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50 ADVANCES IN PALAEOICHTHYOLOGY Fig. 2. Vertical cross-sections of scales with all 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. E, Trimpleylepis concatenata gen et. sp. nov. GIT 384-12, Ohesaare Borehole, Saaremaa, Estonia, depth 94.32-94.40 m, Ludfordian, Upper Silurian. B, D. Family Rhyncholepididae Kiær, 1924 gen. et sp. indet., scale, B, GIT 385-13, Gardner’s Bank, c. 7 m below Psammosteus Limestone, U. Downton Group, Prídolí, Silurian; D, GIT 384-14, Gardner’s Bank, c. 7 m below Psammosteus Limestone, U. Downton Group, Prídolí, Silurian.
C.G.Miller, T. Marss, H. Blom. New anaspid material from Britain and Estonia 51 Märss and Miller, 2002 all have a tuberculated sculpture (M. asperella having star-like tubercles). Trimpleylepis juncta differs from all of them in having tubercles joined by low ridges, which follow the long axis of scales/(?)platelets and because it has a narrower scale anterior overlapped area. For these reasons we consider that the material is different enough from other birkeniid anaspids for a new genus to be established. It is possible that the material referred here as platelets could represent terminations or articulation processes of scales (Fig. 1U) as some scales in articulated specimens of Birkenia Traquair have sculptures that converge and are not so regular towards terminations of scales (Blom et al. 2002, fig. 14g). However, because of their greater width, we prefer to describe them here as possible platelets. The tubercles on both scales and (?)platelets are remarkably regular in size (Fig. 1) which would suggest that they all belong to the same taxon. Some of the Man Brook material including the holotype (Figs 1A-C) appears striated under a light microscope, but these pseudo-striations are the result of microscopic cracks present in much of the material. HCl treatment of thin sections showed only that the etching preferentially dissolved the areas adjacent to cracks. Trimpleylepis concatenata sp. nov. Figs 2E; 3A-F Etymology. The ridges that join the tubercles fade in the gap between tubercles and give the impression of a concatenation. Holotype. Fig. 3C, scale GIT 384-3 from core section from depth 94.32-94.40m, Ohesaare Borehole, Saaremaa, Estonia, Tahula Beds, Kuressaare Regional Stage, Ludfordian Stage, Ludlow Series, Upper Silurian. Material. 6 scales from the Ohesaare Borehole. Diagnosis. Flattened and saddle-like scales with a single row of well developed tubercles of circular outline; ridge that joins tubercles parallel to long axis of scale becomes lower between each tubercle. Microstructure of scales relatively compact with tubules often diverging in a fan-shape; rare ?vascular canal openings on main scale area. Description. Scales flattened to saddle shaped in section with a single row of rounded tubercles. Tubercles mostly arranged in a linear fashion, occasionally line is slightly disrupted (Fig. 3B). Ridge joining tubercles prominent but becomes lower between tubercles leaving either reduced ridge (Fig 3C) or almost flattened area (Fig 3D). Area either side of ridges smooth with occasional openings of vascular canals (Figs 3B, F). Overlapped area absent (Figs 3B, D, E), reduced (Figs 3A, C) or well developed near to articulation processes (Fig. 3F). Histology. The material from the Ohesaare borehole, Saaremaa, Estonia (Figs 3A-F) is not so cracked; its histology (Fig. 2E) is similar to the British material (e.g. Fig. 2C). In thin section, no evidence was found for vascular canals despite the openings visible on the main scale area of some scales (Figs 3B, F). Fine tubules diverge in a fan-shape (Fig. 4E; cf. Gross 1958, fig. 3). Remarks. The tubercles on the Estonian material are identical in diameter to the British specimens but in general are more rounded (Figs 1, 3). A poorly developed overlapped area in some scales is also common to both taxa. For these reasons the Estonian material can certainly be considered to be from the genus Trimpleylepis. T. juncta gen. et sp. nov. from Man Brook shows a wide variation in tubercle outline ranging from spherical
Page 1 and 2: 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 49: 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
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E. Lukševičs, I. Zupiņš. Sedime
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J. Valiukevičius. Silurian acantho
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V. Pernegre, V. Dupret. Biostratigr
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Ž. Žigaite. New telodont from Tuv
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