He found the mantis buried 6.5 feet (2 meters) below the surface in an amber mine in Japan's northeastern Iwate Prefecture. "This part of Japan is famous for producing large amounts of amber, but it was very fortunate for me to find this specimen," said Sasaki. "I found it in a deposit that had lots of other insects-ancient flies, bees, and cockroaches-but this was the only praying mantis," he added.
Although the forelegs, head, and antennae of the creature appear to be well preserved, the wings and abdomen have been badly crushed.
The mantis is the oldest ever found in Japan and one of only seven in the world from the Cretaceous period, according to Kyoichiro Ueda, executive curator of the Kitakyushu Museum of Natural History and Human History.
"Previous mantis specimens have been found in New Jersey, northern Myanmar (Burma), Siberia, and Lebanon," he said.
But Sasaki's discovery appears to be different from any of those mantises.
"Modern mantises have a series of spines-maybe five or six-on their forelegs, to help them catch prey," said Ueda. "The American Museum of Natural History has told us that no mantis from the Cretaceous period has ever been found with spines," he added.
But, the new specimen has two such spines protruding from its femur. "That makes this fossil very unusual and interesting to science," said Ueda.
Another difference is that unlike previous finds, the newfound mantis has tiny hairs on its forelegs.
According to Ueda, the years of the late Cretaceous period were a kind of transition phase between the ancient and modern worlds, and this fossil displays many intermediate elements between the two eras. "It is an excellent example of the transformation of morphological structures," he said.
The block of amber is being polished to give researchers a better view of different parts of the fossil, which may reveal other differences between ancient and modern mantises.