An impressive Diplomystus fossil fish from the celebrated Green River Formation of Wyoming, dating to the Eocene epoch (approximately 50 million years ago). This substantial specimen is preserved on a limestone slab measuring 41 × 24 × 1.8 cm, with the fish itself reaching an impressive 30 cm in length. The total weight of the piece is 2.955 kg.

Diplomystus dentatus, an extinct relative of modern herrings, is distinguished by its gently upturned jaw—an adaptation for surface feeding. Fossils from the Green River Formation are renowned for their extraordinary preservation, capturing fine anatomical detail from an ancient freshwater lake ecosystem.

This large and visually striking slab showcases the fish in exceptional articulation, with the vertebral column, fin rays, and cranial features clearly defined. The generous size of the specimen gives it strong display presence, making it an outstanding centerpiece for a fossil collection, gallery, or educational setting.