Early Jurassic (Late Sinemurian–Early Pliensbachian) Ammonites from the Limestone Boulders of Bodrak River Basin, Southwest Crimea

Ammonites from two separate limestone blocks in the Bodrak River basin (Southwest Crimea) are described. The assemblage from the first boulder (on Tatyana’s Hill) is represented by the Echioceratidae ammonites (genera Orthechioceras and Echioceras ). The ammonite complex from the second boulder (in the Ammonite Ravine) is represented by one species of Calliphylloceras (family Phylloceratidae), one species of Uptonia (family Polymorphitidae), and three species of the genus Tropidoceras (family Tropidoceratidae). A new species Tropidoceras komarovi is described. For the first time for the Lower Jurassic of Crimea, a sequence of biostratigraphic units is proposed within each of the studied boulders. These units are correlated with biostratigraphic units (zones, subzones, and biohorizons) of the Sub-Mediterranean scale. Within the first boulder, the following units (bottom to top) are established: (1) Biohorizon Orthechioceras edmundi; (2) Biohorizon Echioceras rhodanicum; (3) Biohorizon Echioceras raricostatoides and (4) Biohorizon Echioceras crassicostatum, which correspond to the Raricostatum Zone and Densinodulum and Raricostatum subzones of the upper Sinemurian of Europe. Within the second block, the following units are established (from bottom to top): (1) Biohorizon Uptonia cf. jamesoni and (2) Biohorizon Tropidoceras erythraeum, corresponding to Jamesoni Zone (Jamesoni Subzone) and the bottom of the Ibex Zone (Masseanum Subzone) of the lower Pliensbachian of Europe. It is shown that the studied blocks in Bodrak River basin are composed of limestones of different ages, which, in turn, are different from the age of enclosing rocks.