| Here is a Mexican ammonite of the species Idoceras densicostatum which is sits nicely on its matrix. | |||
| Location: | Canon de San Matias, near Casa Sotelo, Sierra de Santa Rosa, Zacatecas, Mexico | ||
| Size Ammonite: | about 59 mm | ||
| Age: | Upper Jurassic, Kimmeridgian (About 152 Ma) | ||