БЪЛГАРСКО ГЕОЛОГИЧЕСКО ДРУЖЕСТВО, Национална конференция с международно участие „ГЕОНАУКИ 2017“ BULGARIAN GEOLOGICAL SOCIETY, National Conference with international participation “GEOSCIENCES 2017” Ammonites of the family Sphaeroceratidae from the Bajocian in Bulgaria Амонити от семейство Sphaeroceratidae от Байоския етаж в България To the memory of Andrew (Walrus) England (May 26, 1954 – September 8, 2017) Lubomir Metodiev Любомир Методиев Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 24; 1113 Sofia; E-mail:
[email protected] Keywords: ammonites, Sphaeroceratidae, Bajocian, Bulgaria. The ammonite family Sphaeroceratidae consists of continuous nature of the exposures and the difficulty in small- to medium-sized ammonites, with characteris- following them both vertically and laterally. Only a few tic sphaeroconic to eccentric coiling, contracted body- taxo nomically and biostratigraphically aimed studies chamber, deep and narrow to occluded umbilicus and have been published to date (Tzankov, Bončev, 1934; fine wiry ribbing that occur in the Bajocian (Middle Kamenov, 1936; Sapunov, 1961; Metodiev et al., 2014). Jurassic). The number of specimens collected from Thus, this family remains little known in Bulgaria. The Bajocian strata in Bulgaria is small. The geographi- taxonomic re-evaluations of older collections, as well cal occurrence of Bulgarian sphaeroceratids, in terms as the study of some newly excavated localities, have of both localities and regions, is associated mainly recently revealed the presence of several species of the with the Etropole Formation of the Western Balkan genera Labyrinthoceras, Frogdenites, Sphaeroceras Mts. Several fields, associated with the Ozirovo, Bov and Chondroceras. As stated by Parsons (1980), the and Polaten Formations (W Balkan and the East Fore- morphological divergence that separates these genera is Balkan Mts.), have also yielded ammonites from this slight.