Erycites aff. sphaeroconicus Buckman, 1922

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 : 255-256

Erycites aff. sphaeroconicus Buckman, 1922

Fig. 6L.

1922 aff. Erycites sphaeroconicus ; Buckman 1922: pl. 315.

Material.—A specimen preserved on one−side from Kuhe Bashm (050511−7/1).

Dimensions (in mm)

Specimen D U H W

050511−7/1 62 27 38 ~65

Description.—Fairly involute and highly depressed Erycites , with a deep umbilicus, a broad and cadicone whorl cross−section and a flat keel. The ribbing is relatively strong and nearly rectiradiate.The straight primary ribs usually trifurcate ventrolaterally, without any tubercles. The secondary ribs continue straight onto the broad venter and end nearly vertically oriented with respect to the flat keel. About 11 primaries and 33 secondaries have been counted on the last preserved half−whorl (ratio 1:3).

Discussion.—The described specimen is most probably a new species, being characterized by its highly depressed and cadicone whorl cross−section. Concerning the narrow umbilicus and the depressed whorls, it can be somehow compared to the inner whorls of the group of Erycites fallax ( Benecke, 1865) , which has been considered a synonym of E. fallifax Arkell, 1950 by Callomon and Chandler (1994: 21). Compared to the latter our specimen is clearly more involute, much more depressed and has a coarser ribbing. Concerning the narrow umbilicus and the broad, cadicone whorls, our specimen can be best compared to Erycites aff. sphaeroconicus Buckman, 1922 of Rulleau et al. (2001: pl. 27: 7a, b). Other similar taxa are E. barodiscus Gemmellaro, 1886 in Cresta (1997: pl. 3: 5) and E. involutus Prinz, 1904 in Prinz (1904: 90, pl. 32, pl. 33: 7) and Géczy (1966: 103, pl. 25: 5). From these, our specimen is distinguished again by more depressed and cadicone whorls.

Stratigraphic and geographic range.— Erycites is a typical Mediterranean taxon, being only known sporadically from the Kerman area of southeastern Central Iran ( Seyed−Emami 1967, 1971). This is the first record of the genus from the Alborz Range. The single specimen was found at Kuhe Bashm (level VII) above the beds with Pleydellia , co−occurring with Leioceras opalinum from the Late Aalenian Leioceras opalinum Zone.