Geometrid caterpillar in Eocene Baltic amber (Lepidoptera, Geometridae)

Area of Science:

• Paleontology
• Entomology
• Evolutionary Biology

Background:

• Lepidoptera fossils are rare due to delicate structures, making amber preservation crucial for study.
• Eocene Baltic amber, the largest deposit, has lacked reliable Macrolepidoptera (moths and butterflies) fossil reports.
• Understanding Eocene lepidopteran evolution is vital, occurring after the major radiation of flowering plants.

Purpose of the Study:

• To report the discovery of the first geometrid caterpillar fossil from Baltic amber.
• To establish this fossil as the oldest evidence for the Ennominae subfamily, specifically the tribe Boarmiini.
• To provide a critical calibration point for molecular clock analyses within the Geometridae family.

Main Methods:

• Paleontological excavation and analysis of fossilized insect remains within Baltic amber specimens.
• Morphological examination of the caterpillar's delicate structures to determine its taxonomic placement.
• Comparative analysis with extant and fossil geometrid caterpillars to establish evolutionary relationships.

Main Results:

• Discovery of a well-preserved geometrid caterpillar in Eocene Baltic amber.
• Identification of the fossil as the oldest known representative of the Ennominae subfamily (tribe Boarmiini).
• The finding pushes back the estimated divergence of Boarmiini from 32-38 million years ago to 44 million years ago.

Conclusions:

• This fossil represents a significant new calibration point for understanding Geometridae family evolution.
• It provides the earliest evidence for the specialized caterpillar locomotion observed in this group.
• The discovery highlights the importance of amber deposits for preserving exceptionally rare insect fossils and understanding past ecosystems.