Dactylioceras, Hyatt, 1867

Seyed-Emami, Kazem, Fürsich, Franz T., Wilmsen, Markus, Majidifard, Mahmoud R. & Shekarifard, Ali, 2008, Lower and Middle Jurassic ammonoids of the Shemshak Group in Alborz, Iran and their palaeobiogeographical and biostratigraphical importance, Acta Palaeontologica Polonica 53 (2), pp. 237-260 : 246-247

Dactylioceras ( Eodactylites ?) cf. pseudocommune Fucini, 1935

Fig. 4P.

1935 cf. Dactylioceras pseudocommune n. sp.; Fucini 1935: 86, pl. 9: 1–3.

Material.— One specimen, partly covered by matrix, from Sharif−Abad (050512−7/2).

Dimensions (in mm)

Specimen D U H W

050512−7/2 36 50 32 28 Description.—Evolute Dactylioceratidae with flat flanks, a nearly rectangular whorl cross−section and a rounded venter. The ribbing is coarse, with straight and slightly prorsiradiate primaries, bifurcating near the venter, apparently without any tubercles.

Discussion.—The coarse ribbing, flat sides, and rectangular whorl cross−section are very similar to D. (E.) pseudocommune Fucini, 1935 .

Stratigraphic and geographic range.—The specimen was found together with D. (O.) semicelatum from the Early Toarcian Dactylioceras semicelatum Zone (Sharif−Abad, level C).

Subgenus Orthodactylites Buckman, 1926 Dactylioceras (Orthodactylites) aff. semicelatum ( Simpson, 1843)

Fig. 4I, M.

1843 aff. Ammonites semicelatus ; Simpson 1843: 20.

1972 aff. Dactylioceras (Orthodactylites) semicelatum ( Simpson, 1843) ; Schmidt−Effing 1972: 95, pl. 4: 1–4; pl. 19: 13; text−figs. 16, 17.

1980 aff. Dactylioceras (Orthodactylites) semicelatum (Simpson) ; Howarth 1980: 646, pls. 80, 81; pl. 82: 11, 12; text−figs. 2, 3 (with synonymy).

2004 aff. Dactylioceras (Orthodactylites) semicelatum ( Simpson 1843) ; Seyed−Emami et al. 2004: 81, pl. 1: 1.

Material.— Three inner whorls from Sharif−Abad (050512− 7/1, 050512−7/3, 050512−7/4) and two specimens from Kuhe Bashm collected earlier on by K.S. −E. (80−SE−18, H−209 ). Dimensions (in mm)

Specimen D U H W

050512−7/1 36 42 31 29

050512−7/4 40 42 30 31

Description.—Moderately evolute Dactylioceras with an ovate, slightly higher than wide whorl cross−section, which converges a little towards the rounded venter. The ribs are slightly prorsiradiate, sharp, dense, relatively fine, single or bifurcating on the outer part of the flank. Ventrolateral tubercles are not developed at any stage.

Discussion.—Except for the somewhat narrower umbilicus, our specimens fits well within the range of variation of the species given by Howarth (1980: pl. 81: 1, 2).

Stratigraphic and geographic range.—Kuhe Bashm, level III; Sharif−Abad, level C. D. (O.) semicelatus is widely distributed in Europe, occurring in the Dactylioceras tenuicostatum Zone (? Dactylioceras semicelatum Subzone ) of the Early Toarcian.