NEWLY DISCOVERED MILLIPEDES (ARTHROPODA: DIPLOPODA) FROM NEOGENE DEPOSITS IN PANAMA AND THE SOUTHEASTERN USA (FLORIDA)

Today, millipedes (Class Diplopoda) are one of the most abundant air-breathing groups of arthropods with approximately 12,000 described species and an estimated 80,000 total species. However, fossil diplopod occurrences are uncommon because they typically inhabit moist environments where exoskeletal preservation is unlikely. Thus, each new fossil discovery has the potential to provide important information about their evolution and paleobiogeography. Here, we report two new fossil millipedes, both in the eugnathan superorder Juliformia, which contains long, cylindrical millipedes that are rounded in cross-section. The first from the lower Miocene Las Cascadas Formation and exposed during recent excavations along the Panama Canal, is calcified, at least 13.5 cm long and, based on its size, most likely belongs to either the Order Spirostreptida or Spirobolida. It co-occurs with leaf impressions of tropical dicot trees and palms in a greenish-gray mudstone. The other from a Holocene cave deposit in Alachua County, Florida, USA, was preserved on popcorn calcite, is under 5 cm long, and probably represents the family Parajulidea (Order Julida). These new discoveries broaden knowledge of Neotropical diplopod fossils and suggest that calcification may be an important mode of millipede fossilization.