It’s not often that you can see the exquisitely preserved body of a creature that actually walked (or in this case, crawled) with the dinosaurs. But such is the case with the fossil of a two millimeter long beetle found in 99-million-year-old Cretaceous Burmese amber.

Fig. 2 from Caterino et al. 2015.

You can see the stripes on its carapace, the lenses of its eyes, the joints of its legs, the knobby projections on its head, and its club-like, jointed antennae carefully tucked into a special pocket on the side of its head.

Fig. 4 from Caterino et al. 2015.

Its tiny, saber-like mouthparts are also visible, and they indicate the beetle was a predator like its relatives today.

Here’s the lead author explaining why this fossil is so special and exciting to him:

So much is so well preserved that scientists can even identify it: it is a hister beetle, of which there are 4,000 modern species. Scientists had previously had to make educated guesses about what the ancestors of hister beetles looked like. This fossil proves that many of the features scientists had hypothesized to exist indeed existed. The fossil's antennae lie in pockets that are uncovered, but modern beetles either tuck their antennae into covered pockets or only have slight indentations and hide their antennae with other parts of their body. The fossil represents an intermediate form.

The beetle also helps biologists construct more accurate evolutionary trees, since every tree contains inferences about what the common ancestor of two groups looked like. With an actual ancestral beetle in hand, biologists no longer have to guess -- they know.

Reference

Caterino, Michael S., Karin Wolf-Schwenninger, and GÜNTER BECHLY. "Cretonthophilus tuberculatus, a remarkable new genus and species of hister beetle (Coleoptera: Histeridae) from Cretaceous Burmese amber." Zootaxa 4052, no. 2 (2015): 241-245.