sedimentary

Fish Fossil in Limestone

Lycoptera (likely) in Micritic Limestone

AI-generated identification · may be incorrect

Matrix hardness: 3-4 (Mohs); Color: Tan to buff matrix with reddish-brown organic/mineralized fossil; Luster: Dull/Earthy; Structure: Fine-grained sedimentary layers; Cleavage: None (conchoidal fracture on matrix)

Hardness: 3-4 (Mohs)
Luster: Dull/Earthy

Identified May 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through rapid burial of organisms in fine-grained lacustrine (lake) or marine sediment during the Mesozoic era (Early Cretaceous, approx. 125 million years ago). The high-pressure compaction turned mud into limestone while preserving the organic outline.

Uses & applications

Scientific study, educational display, and private fossil collecting.

Geological facts

Lycoptera is one of the most prolific fossil fish found in the Jehol Biota. These fossils represent an early stage in the evolution of osteoglossomorphs, a group of bony fish that still exists today.

Field identification & locations

Identify in the field by looking for thin, flat layers of sedimentary rock near ancient lake beds; look for symmetrical organic patterns or skeletal features contrast against the lighter rock. Commonly found in the Liaoning Province of China.