100-million-year-old bug had crab-like claws unlike any known insect

Amber from Myanmar's Kachin region continues to reveal extraordinary glimpses into life during the age of dinosaurs. Preserved inside the 100 million-year-old resin are fossils from an ancient forest ecosystem that once supported a remarkable variety of creatures, including species never seen before. Now, researchers at Ludwig Maximilian University of Munich (LMU) have identified a newly discovered true bug (Heteroptera) with one especially unusual feature.

Its front legs ended in large claw-like structures that resemble the pincers of crabs. These appendages, known as chelae, function much like forceps and are extremely uncommon among insects. "Previously, such chelae were known from only three insect groups. This fossil therefore represents the fourth known case of these structures evolving independently in insects," explains Privatdozent Carolin Haug, zoologist at LMU's Faculty of Biology. Haug and her colleagues worked with researchers from the University of Rostock and the University of Oulu in Finland to study the fossil in detail. Using micro-computed tomography, the team created highly detailed 3D images that allowed them to examine the insect's anatomy. Their findings were published in the journal Insects . The scientists also carried out a large morphological comparison involving more than 2,000 chelae and similar grasping appendages from both living and extinct species. Their analysis showed that the claws of this fossil bug were strikingly different from those found in other insects. Instead, the structures more closely resembled those seen in more distant arthropods such as decapods (crabs, lobsters, shrimps, etc.) and tanaids. Because of its highly unusual anatomy, the insect was assigned to an entirely new genus named Carcinonepa . The name combines the Latinized Greek term for "crab" (carcino-) with nepa , referencing the true water bug group Nepomorpha.

Key points

• Its front legs ended in large claw-like structures that resemble the pincers of crabs.
• These appendages, known as chelae, function much like forceps and are extremely uncommon among insects.
• "Previously, such chelae were known from only three insect groups.
• This fossil therefore represents the fourth known case of these structures evolving independently in insects," explains Privatdozent Carolin Haug, zoologist at LMU's Faculty of Biology.
• Haug and her colleagues worked with researchers from the University of Rostock and the University of Oulu in Finland to study the fossil in detail.