Burmanopetalum inexpectatum, Stoev, Pavel, Moritz, Leif & Wesener, Thomas, 2019

Stoev, Pavel, Moritz, Leif & Wesener, Thomas, 2019, Dwarfs under dinosaur legs: a new millipede of the order Callipodida (Diplopoda) from Cretaceous amber of Burma, ZooKeys 841, pp. 79-96 : 82-85

† Burmanopetalum inexpectatum sp. nov. Figures 1 A–H, 2 A–G, 3

Previous records.

Callipodida , family undetermined: Wesener and Moritz 2018: 1135-1136, fig. 2C.

Material examined.

Holotype (ZFMK-MYR07366), from the collection of Mr Patrick Müller (transferred to ZFMK), adult female, Myanmar, Kachin State, Hukawng Valley, Noije Bum amber mine, 26°15'N, 96°34'E.

Diagnosis.

As for the suborder, family and genus. Species further characterized by antennomeres III–V strongly conical (infundibular), VI and VII subrectangular; metazonites with 28 more or less well-developed narrow, subparallel crests, well-separated from one another, poriferous crests missing.

Etymology.

" inexpectatum " in Latin means "unexpected" referring to the stunning discovery of just a single specimen among the 529 millipede specimens so far found in Burmese amber. The species epithet is an adjective.

Locality and horizon.

Burmese amber, early Cenomanian, 98.79 ± 0.62 Mya ( Shi et al. 2012) from the Noije Bum amber mine, Hukawng Valley, Kachin State, northern Myanmar.

Taphonomic features.

Amber : Cut and polished. Piece rectangular, upper surface slightly convex, 14.1 mm × 6.3 mm × 2.5 mm. Colour: light yellow transparent.

Specimen: Close to surface, body coiled in S-shape, vulvae extended.

Syninclusions : Ensifera ( Insecta: Orthoptera ), Stellate hairs, large grayish spherical structure (Sporangia?).

Description.

Body length: 8.2 mm (measured from the CT scan); width of largest body ring 14: 0.4 mm. Body composed of 35 body rings and telson (Figs 1A, 2A, 3).

Head elliptical, longer than wide, covered by long setae (Figs 1B, 2B,C). Labrum with 3 teeth. Eyes composed of 5 ommatidia situated in 2 rows (3+2). Incisura lateralis present, extending from mandible stipes to antennal base. Antennae (Fig. 1C) long and slender reaching to, or slightly extending beyond posterior margin of body ring 4 when folded backwards. Antennae 0.9 mm long, relative antennomere lengths II>V>III>IV>VI>VII=I, antennomere II more than twice the length of VI, antennomeres III–V strongly conical (infundibular), VI and VII subrectangular, ultimate disc with 4 apical cones. Tömösváry organ small, located between antennal base and ommatidia, nearly touching the foremost ommatidium. Mandible cardo small (Fig. 1B), stipes ca 3 × as long as cardo. Gnathochilarium (Fig. 2D) consisting of a larger eumentum and a smaller promentum, lamellae linguales and long stipites; stipites 2 × as long as lamellae linguales and slightly swollen.

Collum not concealing head from above, nearly as wide as head, anteriorly smooth, only posterior third with poorly developed crests (Figs 1B, 2B).

Body cylindrical, with tergites and pleurites fused, sternites free (Fig. 2E). Body rings half as long as wide, 3 penultimate body rings shorter, ca 1/3 as long as wide. Pleurotergites with an inconspicuous median suture, composed of smooth prozonites and carinate metazonites, latter being greater in diameter than prozonites. Prozonites void of crests, with minute scale-like ornamentation (Fig. 1B), metazonites with 28 more or less well-developed longitudinal, narrow, subparallel crests, well-separated from one another, extending over whole body ring, gradually reduced in size laterally and ventrally (Fig. 1D). Crests most pronounced on pleurotergites 3-8. Anterior 4 body rings narrower than following body rings, with less conspicuous crests. Ozopores inconspicuous, an ozopore-like opening visible on body ring 8 (Fig. 1D) and also possibly on body ring 4, situated between the crests, poriferous crests missing. Pleurotergal setae absent.

Telson enlarged, spatulate, 2 × the size of the last body ring, dorsal side slightly concave anteriorly (Figs 1E, 2F). Epiproct with inconspicuous crests and 2 spinnerets. Hypoproct divided into a single median plate and 2 lateral plates, all devoid of macrosetae. Paraprocts (anal valves) projecting posteriorly, divided transversally (Fig. 2G).

Legs Anterior leg of body ring 14 0.35 mm long, legs composed of 8 podomeres, relative lengths coxa = trochanter <tarsus 1 = tarsus 2 <femur <tibia = postfemur = prefemur (Fig. 1F). Tarsus 2 with a short claw. Leg 1 and 2 not visibly modified. Some midbody legs with coxal vesicles.

Male sexual characters unknown.

Female sexual characters a pair of long, tubular, apically club-like vulvae behind leg 2 (Fig. 1G); vulvae 0.9 mm long when extruded, apically with long setae. Basal part of vulvae covered by reddish circles (ca 80 µm in diameter) (Fig. 1H). Third pleurotergite slightly enlarged as is typical for adult female callipodidans.

Taxonomic remarks.

Several important characters used in the current systematics of Callipodida are unknown in the described specimen, such as the distribution of coxal vesicles on legs in both sexes, as well as male-specific traits such as the shape of gonopods, the presence/absence of modifications on the head and the anterior part of legs and sternites.