Graphoceras Buckman, 1898

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 : 254

Subgenus Graphoceras Buckman, 1898 Graphoceras (Graphoceras) concavum

(J. Sowerby, 1815)

Fig. 6J.

1815 Ammonites concavus; J. Sowerby 1815: 274, pl. 94.

1967 Ludwigia (Graphoceras) concava concava (Sowerby) 1815 ; Seyed−Emami 1967: 66, pl. 2: 5; pl. 8: 5.

1969 Graphoceras (Graphceras) concavum (Sowerby) ; Contini 1969: 61, pl. 5: 3–6; pl. 21: 1–9; pl. 22: 1–3; pl. 24: 48–51; text−figs. 16, 17 (with synonymy).

2001 Graphoceras (Graphoceras) concavum (Sowerby) ; Rulleau et al. 2001: pl. 23: 1–3.

2004 Graphoceras concavum (J. Sowerby, 1825) ; Myczyński 2004: 99, fig. 33/1.

Material.—Four fragmentary specimens from Sharif−Abad (050512−11/1–050512−11/4) and three fragmentary specimens from Kuhe Bashm (050511−15/2, 050511−15/4, 050511−15/6).

Description.—The figured specimen ( Fig. 6J) is a crushed member of the Graphoceratinae with parts of the original shell preserved. It is relatively involute, with a high−ovate, compressed whorl cross−section and a sharp keel. The ribbing is strongly anguliform−falcate. The last preserved whorl is probably part of the body chamber. It egresses slightly with a distinct peri−umbilical depression.

Discussion.—The figured specimen falls within the range of variation of G. (G.) concavum as given by Contini (1969)

and Caloo (1971). Stratigraphic and geographic range.—Kuhe Bashm, level

IX; Sharif−Abad, level G. Late Aalenian, Otoceras concavum Zone.

Graphoceras (Graphoceras) decorum Buckman, 1904 Fig. 6H.

1904 Graphoceras decorum ; Buckman 1904: p. 98, pl. 15: 3, 4.

2004 Graphoceras decorum Buckman, 1888 ; Myczyński 2004: 100, fig. 33/4.

2006 Graphoceras (Graphoceras) decorum Buckman, 1902 ; Seyed−Emami et al. 2006: 268, figs. 5/5a, b, 12a, b, 18.

Material.—Eight fragmentary specimens from Sharif−Abad: 050512−11 (11/1–11/8).

Dimensions (in mm)

Specimen D U H W

050512−11/8 35 20 49 –

Description and discussion.—See Seyed−Emami et al. (2006).

Stratigraphic and geographic range.—Sharif−Abad, level G. Late Aalenian, Otoceras concavum Zone.