sedimentary
Fish Fossil in Limestone
Lycoptera (likely) in Micritic Limestone
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
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Physical properties
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)
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.
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