Fig. 1

Geographical and geological location. A Location map of the fossiliferous localities of the San Gregorio Formation. Stratigraphic section polygonal: Northward Chiguaje Hill “NCH” (see Additional file 1) and San Gregorio Río Seco “SGRS” (see Additional file 2). B Generalized geological map near the town of Urumaco showing the outcropping geological units in the area (modified after Quiroz and Jaramillo 2010). Fm. Formation, Mb. Member