Abstract
The entire Mesozoic Era is rather poor in millipede (class Diplopoda) fossils, with less than a dozen species being taxonomically described. Here, we describe the first fossil millipede of the order Callipodida, Burmanopetaluminexpectatumgen. nov. et sp. nov., found in early Cenomanian amber of Burma, 98.79±0.62 Mya. The species possesses a number of morphological traits that exclude it from all extant suborders, and Burmanopetalidea suborder nov. and Burmanopetalidae fam. nov. are here erected to accommodate it. The new suborder can be recognized by the following unique characters: pleurotergal setae absent; telson with a specific spatulate shape twice the size of the penultimate body ring; hypoproct devoid of setae; and eyes composed of five well-separated ommatidia. While the callipodidan habitus seems to have remained generally unchanged for at least 99 million years, pleurotergal and hypoproctal setation, as well as the complexity of eyes in ground-dwelling forms may have evolved recently in the order. As B.inexpectatumgen. nov. et sp. nov. is the first true callipodidan in the fossil record, the minimum age of Callipodida is thus at least 99 Mya.
Highlights
Millipedes (Diplopoda) are a highly diverse and a largely understudied group of arthropods with >11,000 described species (Enghoff et al 2015)
The presence of 35 body rings, free sternites, pleurotergites with subparallel crests, well-separated from one another, a dorsal midline suture, a telson bearing spinnerets, a tripartite hypoproct and a pair of long retractable vulvae, allow the species to be unequivocally assigned to the order Callipodida
Fossil Callipodida could be confused with the nowadays much more common Cambalidea (Spirostreptida), which are known from 20 specimens in Burmese amber (Wesener and Moritz 2018), but cambalideans have neither a middorsal tergal suture nor spinnerets, both of which are clearly visible in Burmanopetalum inexpectatum gen. nov. et sp. nov
Summary
Millipedes (Diplopoda) are a highly diverse and a largely understudied group of arthropods with >11,000 described species (Enghoff et al 2015). The earliest fossil records of millipedes come from the Middle Silurian or Lower Devonian of Scotland about 420 Mya, where three archipolypod species were found (Wilson and Anderson 2004; Shear and Edgecombe 2010; Wolfe et al 2016; Suarez et al 2017). Callipodida is a small order of spinneret-carrying millipedes of the superorder Nematophora (Blanke and Wesener 2014; Enghoff et al 2015). Callipodida are considered a sister-group either to Stemmiulida (Blanke and Wesener 2014) or to Chordeumatida (Brewer and Bond 2013). Several species of Callipodida are unusually fetid due to their defense secretions containing pcresol (Makarov et al 2011), and can be smelled several meters away (author observations)
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