Trypanites weisei Mägdefrau, 1932

Diagnosis (revised). More or less straight and perpendicular to the substrate Trypanites penetrating hardened sediment and skeletal hard substrate, with a relatively high length/diameter ratio (c. 20–50) (after Mägdefrau 1932 and Bromley 1972).

Description and discussion T. weisei from the Bajocian/Dinantian unconformity of the Mendips range in diameter from 0.7-2.3mm (n=442) and display a normal distribution, interpreted as natural intraspecific variation, within this range. They have an average diameter of 1.4mm. Lengths are difficult to determine, as short individuals are merely the ends of borings from early colonization phases that have been truncated by erosion. However, they extend a maximum of 130 mm into the Carboniferous Limestone.

Measurement s of the type material of T. weisei have recently been made by Dr M. Bertling. Mean diameter is 0.92 mm and maximum diameter is 2.0 mm. Mean length is 16.6mm (range 3.0-54.0mm). We do not consider that the Mendip material is sufficiently different to be distinguishable from T. weisei.

Diagnosis.—Simple, vertical, more or less straight borings with a single opening to surface; circular in cross section and isodiametric throughout length.

Description.—Borings narrow, elongate and circular to subcircular in transverse section; in longitudinal section borings parallel to subparallel sided (Figures 1, 2) and generally taper towards base (Figure 2.1); apertural diameters average 1.03 mm but some flare (Figure 3.1). Most borings approximately straight (Figures 1, 2) or gently curved at an angle rarely exceeding 150° (Figures 1, 2.1); if curved, a single inflection is characteristic, commonly near distal end (Figure 2.1); borings are up to 19.83 mm long with a mean observed length of about 4mm (Table 1), latter figure should be treated with caution since it represents length of borings visible in thin sections; such lengths not true because thin section only gives random slices through curved and variably-oriented borings; walls of borings unlined and smooth; although no true branching occurs, interpenetrations common (Figures 1, 2) resulting from different stages of boring discerned in stromatoporoid mounds; orientation of borings highly variable, ranging from vertical to subhorizontal.

Diagnosis– (Emended after Bromley, 1972, p. 95.) More or less straight and vertical Trypanites penetrating hard substrates.

Description– Essentially straight, simple cylindrical borings. The borings are normally inclined at approximately 30° from vertical. Dimensions vary between individual specimens. Lengths vary between 20-75 μm and width between 1-5 μm.

Remarks– In the redefinition of the ichnogenus Trypanites, Bromley (1972) included dimensions as a diagnostic feature; this is considered inappropriate (see Pickerill, 1994; Bertlinget al., 2006) and, as such, is excluded from the diagnoses of both T. solitarius and T. weisei, hence the emendations.