The first known fossils of the Platydesmida—an extant American genus in Cretaceous amber from Myanmar (Diplopoda: Platydesmida: Andrognathidae)

Millipedes have been inhabiting the earth for more than 400 my and show a great diversity regarding their morphology and ecology. For a better understanding of the timing and pattern of millipede evolution, Burmese amber offers a unique window into the Cretaceous period, ca. 99 Ma. Here, we describe the first known fossil of the colobognathan order Platydesmida, the species Andrognathus burmiticus n. sp. based on 15 specimens from Cretaceous Burmese amber. We combine classical light-microscopy and modern micro-computer tomography (μCT) with computer aided 3D-reconstructions. These non-invasive techniques allow us to describe the fossil millipedes as detailed as is general practice for extant species, and to grant the scientific community open access to the deposited “Cybertypes”. Based on the combination of unique morphological characters such as surface structures, body type, the unique size and shape of tergite 5, the absence of a hypoproct at the anal segment, and detailed gonopod characteristics, the studied fossils can be placed in the family Andrognathidae and the extant genus Andrognathus, which nowadays is restricted to the eastern USA and Mexico with three extant species. Therefore, the minimum age of the genus Andrognathus is pushed to the Cenomanian, 99 Ma. It can be assumed that the genus was much more diverse and wider distributed in the past and migrated between Asia and America via one of the once existing land bridges. These unique fossils prove the unusual relictual distribution of Andrognathus and can serve as key-fossils for the dating of the diplopod phylogeny.