Two Flat-Backed Polydesmidan Millipedes from the Miocene Chiapas-Amber Lagerstätte, Mexico

Abstract

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.

The millipedes and centipedes of Chiapas amber

“…The latter includes the fossil species Scolopocryptops simojovelensis Edgecombe et al 2012 (Scolopendromorpha) from Chiapas Amber. Recently, the fossil millipedes Parastemmiulus elektron Riquelme, 2013 (Stemmiulida), Anbarrhacus adamantis Riquelme & Hernández-Patricio, 2014 (Polydesmida), and Maatidesmus paachtun Riquelme & Hernández-Patricio, 2014 (Polydesmida) from Chiapas amber (Riquelme et al 2014a) were included in a new revision of Diplopoda fossil record worldwide (Edgecombe 2015). Two other centipedes have been reported in Ross et al (2016).…”

“…These sites are part of the Chiapas amber Lagerstätte with remarkable fossil preservation of terrestrial arthropods, including myriapods (Riquelme et al , 2014a.…”

New Fossil Scorpion from the Chiapas Amber Lagerstätte

“…The fossil studied here was collected in a hand-made pit at the Guadalupe Victoria site near Simojovel, Chiapas, south of Mexico ( Fig 1 ), which comprises two indigenous settlements: The Guadalupe Victoria I and II [ 24 ][ 25 ]. The crude amber piece was found by a native local farmer, who informed Director B. Luna of the Museo del Ámbar in San Cristobal de Las Casas, Chiapas, of his discovery.…”

“…According to geographical references provided by the collector, a provenance analysis has been carried out in amber with infrared and X-ray spectroscopies. This analysis has been complemented with field geology tracking the outcrop at the amber site commonly known as the Guadalupe Victoria site [ 24 ][ 25 ]. The present amber section consists of organic-rich lignite embedded in non-fissile, coarse to fine grained sandstone with variable thickness.…”

“…23–15 Ma. [ 24 ][ 25 ][ 29 – 32 ]. Another outcrop near Simojovel assigned to the La Quinta strata dated as late Oligocene has been mentioned as containing amber [ 29 ][ 30 ].…”