Double Cockerellites liops and Diplomystus dentatus | 100% Natural | Green River Formation | Wyoming

Cockerellites liops and Diplomystus dentatus
Eocene (51.98 Million Years Ago)
Green River Formation, Wyoming, USA
In Stone Fossils Private Quarry

Family Moronidae

A diverse assemblage of fossil fish species, including C. liops, P. serrata, H. hypsacantha, and undescribed species of Priscacara and Hypsiprisca, have been discovered in the fossil record.

C. liops Specimens

Fossil evidence suggests that C. liops exhibited a gregarious behavior, with specimens found both as isolated individuals and in mass mortality assemblages. This indicates that C. liops likely traveled in schools throughout its life cycle.

Morphological Characteristics

- Maximum size: 6 inches

- Body shape: Similar to that of modern members of the family Centrarchidae (sunfish family), suggesting a possible convergent evolutionary relationship.

Paleoecological Implications

The presence of C. liops and other fossil fish species in the Moronidae family provides valuable insights into the paleoecology of ancient aquatic ecosystems. The discovery of mass mortality assemblages and the inferred schooling behavior of C. liops offer a glimpse into the complex interactions and dynamics of ancient fish populations.

Diplomystus is an extinct genus of freshwater clupeomorph fish distantly related to modern-day extant herrings, alewives, and sardines. The genus was first named and described by Edward Drinker Cope in 1877.

Ray-finned Fish - Diplomystus dentatus

Order Ellimmichthyiformes, Family Paraclupeidae

The last known species of the Ellimmichthyiformes order went extinct sometime in the middle Eocene. D. dentatus is a primitive relative of the modern day herring. The genus Diplomystus is also known from fossil deposits in China.

D. dentatus is the 2nd most common fossil fish found from Fossil Lake. Specimens ranging from embryonic size (about 0.7 inches) to full-grown adults (about 26 inches) are common. Smaller-sized specimens are more commonly found in mid-lake than near-shore deposits. This suggests that D. dentatus spawned in open water.

This species' upturned mouth indicates it fed at the surface of Fossil Lake. D. dentatus specimens are commonly found with other fish stuck in their mouths, including other D. dentatus specimens.