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Beetle fossil history

BEETLE FOSSIL HISTORY

are pointed apically, and extend beyond the tip

of the abdomen. The extinct Permian families

of Protocoleoptera include Tshecardocoleidae,

Oboricoleidae, and Moravocoleidae, believed to

have been wood feeders as larvae, and considered

to be similar to the extant Archostemata. Even

older fossils, such as Adiphlebia lacoana from the

Carboniferous period of North America, have

been interpreted by some authors as beetles, but

this is not widely accepted.

As they have robust exoskeletons, adult beetles

have a better chance of preservation in the fossil

record than many insects. All four modern

suborders—Archostemata, Myxophaga,

Adephaga, and Polyphaga—are well known in

the fossil record, as are more than 60 percent of

modern families. Those that are missing are often

small families, or associated with habitats where

preservation is unlikely.

The beetle fossil record was given an

enormous boost by the proliferation in the

Cretaceous of amber-producing trees, which

produce a sticky sap in which insects and other

animals and plant fragments become trapped,

and which then hardens into resin and ultimately

fossilizes into amber. Insect fossils in amber, called

“inclusions,” are often perfectly preserved in three

dimensions, and skillful polishing can reveal the

insects from the desired angles. The superior

preservation makes the study of amber fossils

easier and less subjective than the study of stone

fossils. While the most familiar ambers are the

northern European Baltic amber (35 to 48 million

years old) and Caribbean Dominican amber (25

million years old), these are both Cenozoic and

include a fauna not very different at the family,

The oldest undisputed beetle fossils date from

the early Permian, about 290 million years ago.

They belong to the extinct taxon Protocoleoptera,

usually treated as an extinct suborder that is

sister group (closest relative) to all remaining

Coleoptera. Most fossils are between 5 and

20 mm; some are well-preserved impressions of

complete insects, while most are represented only

by elytra. They show that Protocoleoptera are

beetles, although they have unusual features.

The female has an ovipositor (egg-laying tube)

which is unpaired and apically pointed, and

nothing similar exists in any modern beetles.

The elytra have a conspicuous network of veins,