RESUMO
A new fossil species of pyrgodesmid millipede (Polydesmida: Pyrgodesmidae) placed in the genus Myrmecodesmus Silvestri, 1910 is described. The type materials are two amber inclusions, male and female specimens that come from Miocene strata in Chiapas, Mexico. Myrmecodesmus antiquus sp. nov. has collum with 10 dorsal tubercles; without porosteles or ozopores; legs of the rings 2-9 with a short projection on the prefemur in both the female and male. Myrmecodesmus antiquus sp. nov is the first fossil record of the genus Myrmecodesmus. This is a New World taxon that belongs to the pantropical family Pyrgodesmidae. Thus, Myrmecodesmus antiquus sp. nov expands the range of the genus to the Miocene tropics in Middle America.
RESUMO
Two species of fossil polydesmidan millipedes (Diplopoda: Polydesmida) embedded in amber are described from Miocene strata near Simojovel, in the Chiapas Highlands, Mexico. Maatidesmus paachtun gen. et sp. nov., placed into Chelodesmidae Cook, 1895, and Anbarrhacus adamantis gen. et sp. nov., assigned in the family Platyrhacidae Pocock, 1895. Morphological data from fossil specimens have been recovered using 3D X-ray micro-computed tomography and regular to infrared-reflected microscopy. Both fossil species are recognizable as new primarily but not exclusively, by collum margin modification and remarkable paranotal and metatergite dorsal sculpture.