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C.G.Miller, T. Marss, H. Blom. New anaspid material from Britain and Estonia
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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