Mesohedenstroemia Chao, 1959

Zakharov, Yuri D. & Abnavi, Nasrin Moussavi, 2013, The ammonoid recovery after the end-Permian mass extinction: Evidence from the Iran-Transcaucasia area, Siberia, Primorye, and Kazakhstan, Acta Palaeontologica Polonica 58 (1), pp. 127-147 : 137

Genus Mesohedenstroemia Chao, 1959

Type species: Mesohedenstoemia kwansiana Chao, 1959 ; Flemingites beds, Lower Olenekian, Lower Triassic, South China.

Species included: Five species from South China and South Primorye: Mesohedenstroemia kwansiana Chao, 1959 , M. inflata Chao, 1959 , M. planata Chao 1959 , M. bosphorensis ( Zakharov, 1968) , and M. olgae sp. nov.

Brayard and Bucher (2008) have described two forms from northwestern Guangxi, determined as Mesohedenstroemia kwansiana Chao, 1959 and M. planata Chao, 1959 . Based on these fossils they believe that Mesohedenstroemia additionally differs from Hedenstroemia by a simple suture line without adventious elements. However, the forms reported by Brayard and Bucher (2008) are rather reminiscent of some representatives of Ussuridiscus Shigeta and Zakharov in Shigeta et al. 2009.

Emended diagnosis.—Laterally compressed Hedenstroemiidae with involute coiling and broad, distinctive tabulate venter. Suture like in Hedenstroemia but with significantly simpler auxiliary series.

Remarks.—From Hedenstroemia Waagen, 1895 (e.g., Waagen 1895; Popov 1961; Zakharov 1988; Dagys and Ermakova 1990) and Pseudohedenstroemia Kummel, 1957 (e.g., Arkell et al. 1957) it differs by a distinctively wider tabulate venter with angular ventral shoulders and simpler auxiliary series ( Fig. 8 ).

Geographic and stratrigraphic range.—South China, Primorye; lower Olenekian (lower Smithian).

Figures

Fig. 8. Suture lines of some Prolecanitida. A. Mesohedenstroemia olgae sp. nov., DVGI 2/851 (holotype), height 18.4 mm; Lower Olenekian, Mesohedenstroemia bosphorensis Zone; SMID quarry at the Artyom environs, south Primorye. B, C. Hedenstroemia tscherskii (Popov, 1961). Lower Olenekian, Lepiskites kolymensis Zone; Kenyelichi River, Kolyma River basin. B. DVGI 256−3b, height 60.0 mm (B1) and 73.0 mm (B2). C. DVGI 255−19c, height 73.0 mm. Abbreviations: D, dorsal lobe; I, inner lateral lobe; L, lateral lobe; U, umbilical lobe; V, ventral lobe.