AMMONITE CLUSTER

AMMONITE CLUSTER

Sphenodiscus species

Cretaceous

Rosario Formation, Baja California Norte, Mexico

This striking natural assemblage of three rare ammonite specimens are clustered and still attached to some of their original matrix and measures 26 ½ inches in diameter (67.31 cm) and 38 inches tall (96.5 cm) with its natural matrix base.

The genus Sphenodiscus has been found from many continents and is thought to have had a large global distribution during the Maastrichtian stage of the Late Cretaceous. It was one of the last ammonoids to have evolved before the entire subclass became extinct at the end of the Cretaceous–Paleogene extinction event. The shell of Sphenodiscus was streamlined and lateromedially compressed as can be seen here.

The quarries in Northern Mexico that once produced these fabulous specimens have been closed for over 50 years and private collecting is no longer allowed in Mexico making these ammonites irreplaceable. Sphenodiscus were especially prized for their large size and beautiful suture, or growth, lines.