El Doctor Formation

The El Doctor Formation is a geologic formation in Mexico. It preserves fossils dating back to the Albian and Cenomanian stages of the Cretaceous period.

Description
The light grey micritic limestone sequence with intercalated black chert lenses was deposited in an open marine basin with a hypersaline and/or poorly oxygenated bottom.

Fossil content
The formation has provided the following fossils:
 * Fish
 * Enchodus zipapanensis
 *  Xeneichthys yanesi
 * Crustaceans
 * Aeger hidalguensis
 * Polzia eldoctorensis
 * Victoriacaris muhiensis
 * Palinurus sp.