Florissant is better than amber: When it comes to the preservation of fossil beetles.

Research by Dr. Dena Smith, Curator of Invertebrate Paleontology, CU Museum

Collection of Roy Johnson (~200 years old), Colombian Amber. Family Elateridae, Common Name: Click Beetle, 7mm length.

When one mentions fossil insects, most think of amber deposits. Amber is widely noted for exceptional preservation, clarity of anatomical details, and for its ability to capture high levels of diversity, but is amber really the pinnacle of insect preservation that many consider it to be?

Florissant is often cited as one of the world's great fossil insect deposits. Over 1,500 insect species have been described from the 34 million year old deposit. To compare Florissant to amber deposits, I created and used a database that compiled the world wide fossil beetle literature. Beetles in the database represent localities from around the world, including all beetle species described from Florissant and from all fourteen of the beetle-bearing ambers.

	UCM 18618, Holotype (34.1 million years old), Family Cerambycidae: Saperda submerse, Common Name: Long-Horned Beetle. Collected by: T.D.A. Cockerell. 23mm length.

I found that there are more beetle species found at Florissant than any single amber locality. In fact, I discovered that there are more beetle species found at Florissant than at all the amber localities combined. There are 566 beetle species described from Florissant and between one and 183 species described from any single amber locality. When all the amber sites are combined, there are 507 beetle species, 12% lower than found in Florissant alone.

Additional research indicates that Florissant and the amber deposits differ greatly in the size classes they preserve and in the ecology of the beetles that are captured. Florissant captures a wider range of size classes (1-24mm) and beetles average 6.7mm. Amber preserves fewer size classes (1-12.8mm) and the average size is 3.45mm. There are also differences in the ecology of the taxa captured at Florissant and in the amber deposits. Florissant has a good representation of aquatic groups, which are mostly absent from amber deposits. The ambers tend to capture wood-inhabiting groups, which are much less common in Florissant.

UCM 4510, Holotype (34.1 million years old), Family Buprestidae: Chrysobothris gahani, Common Name: Metallic Wood-Boring Beetle. Collected by: T.D.A.Cockerell. 11mm length.

Amber is often thought of as the ideal mode of preservation for fossil insects. However, the rich deposits of the Florissant Fossil Beds show greater levels of diversity, a wider range of size classes preserved and an ecological representation that differs from the amber deposits. For fossil beetle diversity, Florissant truly is better than amber.

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