Glyptograptus aff. latus (Packham, 1962)

Glyptograptus aff. latus (Packham, 1962)

Figures 8F View FIGURE 8 ; 9D–E View FIGURE 9 aff. 1962 Glyptograptus enodis latus subsp. nov.; Packham, p. 518, pl. 71, fig. 20, text-fig. 4e.

aff. 2015 Glyptograptus latus Packham ; Loydell, Frýda, and Gutiérrez-Marco, figs. 16H, 18R.

Holotype. Specimen no. SM A24969 from the lower Aeronian gregarius Biozone [horizon O after Sudbury (1958)], Rheidol Gorge, Wales figured by Packham (1962, pl. 71, fig. 20; text-fig. 4e).

Material. 16 flattened tubaria

Description. The relatively narrow, though markedly gradually widening, tubarium is usually 6–8 mm long. The longest measured specimens attain a length of 10–11 mm. The sicula is 1.9–1.0 mm long, 0.21–0.27 mm wide at the aperture. The virgella is very thin and 0.27–0.29 mm long. The tubarium width increases from 0.5–0.6 mm at th1, to 0.7–0.85 mm at th3, and 0.95–1.0 mm at th5. Specimens with more than 10 thecal pairs attain a maximum width of 1.1 mm. The length of th 11 varies between 0.8 and 0.95 mm. Thecae markedly alternating, overlap for one-quarter to one-third of their length. Supragenicular walls are slightly inclined to the tubarium axis in the proximal thecae. Towards the distal part of the tubarium, they become gently convex and inclined at about 15– 25 ° (values measured at th5). Thecal apertures are 0.2–0.25 mm wide and slightly everted. Apertural excavations are relatively prominent in the proximal part of the tubarium and occupy approximately one-third of the tubarium width. In distal thecae, genicula become less pronounced and excavations become shallower. The 2TRD ranges from 1.5–1.7 mm at th2 and 1.7–1.9 mm at th5. A slen- der nema is rarely projected beyond the thecate part of the tubarium.

Remarks. Packham (1962) described the new species in detail, based on a single specimen. Present specimens have almost identical parameter values with the original description (tubarium width, th1 length, thecal overlap, etc.). Nevertheless, the species G. latus is based on a specimen preserved in relief, found in the gregarius Biozone of Rheidol Gorge, UK, which corresponds to Demirastrites triangulatus – Demirastrites simulans biozones of the Prague Synform. Loydell et al. (2015) recorded G. latus in the halli Biozone (Upper Aeronian) in the El Pintado section in Spain. If all specimens referred to this species in Rheidol Gorge, El Pintado and here (in Želkovice) belong to the same species, then Glyptograptus latus has a rather large stratigraphic range – from the lower Aeronian to the lower Telychian. The overall morphology, and the fact that other species of the genus Glyptograptus also have long stratigraphic ranges, (e.g., Glyptograptus elegans ) allow for the tentative assignment of the Czech specimens to G. latus .