Electroprojapyx alchemicus, Sánchez-García, Sendra, Davis & Grimaldi, 2023

Sánchez-García, Alba, Sendra, Alberto, Davis, Steven & Grimaldi, David A., 2023, Fossil diversity in ‘ dawn’ hexapods (Diplura: Projapygoidea), with direct evidence for being chemically predaceous in the Cretaceous, Zoological Journal of the Linnean Society 198 (3), pp. 847-870 : 850-852

ELECTROPROJAPYX ALCHEMICUS SP. NOV.

( FIG. 2 )

Zoobank registration: urn: lsid: zoobank. org:act: B2A57148-0988-4316-9B09-99264D417E6F

Etymology: The name is derived from the Latin Alchemia, an early, protoscientific practice, and the Latin suffix - icus.

Holotype: AMNH JZCBu-1957 ( Fig.2 ), Zigras collection (in AMNH), sex unknown, adult; specimen entirely preserved and observable laterally; the holotype is at the surface of a corner; the piece is a dark orange colour and turbid, irregular in shape, 28 mm × 14 mm in largest dimensions, with borings of Pholadidae ; syninclusions include one heteropteran nymph, one partial wasp, at least four Collembola (three Symphypleona, one Entomobryomorpha), one acari, plant trichomes and other undetermined organic remains.

Note on preserved behaviour: Specimen AMNH JZCBu-1957 ( Fig. 2 ) preserves an example of predatory behaviour fossilized in Burmese amber. The specimen of E. alchemicus has between its antennae a Collembola Symphypleona (0.5 mm in length), while it is also releasing a glandular substance from the cercal tips. The antennae of E. alchemicus are in close contact with the Collembola ( Fig. 2D ); the elongated abdomen of the dipluran is elevated and curved above the thorax and head with the cerci pointing to the front ( Fig. 2A, C ); there is a line of droplets and short streams of secretion connected by long, fine filaments (presumably, strands of silk) issuing from the tips of both cerci ( Fig. 2B ); several of these strands are nearly the length of the abdomen. The position of the collembolan, posture of the dipluran and presence of cercal secretions can only be explained as an attack movement (cf. San Martín, 1969: 127, fig. 14; San Martín, 1963). Fluid resin probably flowed over the pair of hexapods just as the dipluran was attacking.

Occurrence: Mid-Cretaceous Burmese amber (latest Cenomanian) near Myitkyina, in Kachin Province.

Diagnosis: As for genus, by monotypy.

Description

Sex unknown, adult. Body: Length 2.49 mm, slender. Cuticle altered by preservation, with no visible details. Clothing setae smooth; macrosetae (M) as indicated below.

Head: Length 0.29 mm, 0.12× length of body; dorsum with few smooth setae. A structure that resembles a labial palpus protrudes from the inferior part of the head. Both antennae ( Fig. 2D ) complete (non-regenerated), elongate, reaching second abdominal segment, length 1.23 mm, 0.49× length of body, slightly tapered, with 27 antennomeres; antennomeres I and II subrectangular, distinctly longer than others, together 0.15 mm, antennomere II somewhat swollen distally probably owing to preservation; antennomere III onwards moniliform; medial antennomeres length 0.05 mm, width 0.03 mm; antennomeres II and III without secondary sexual characters, antennomere VII without pyriform sensillum; trichobothria not visible; whorls of setae poorly visible, the few visible setae smooth.

Thorax: 0.29× length of body; pronotum 0.17 mm, mesonotum 0.25 mm, metanotum 0.30 mm. Macrosetae visible in anterior and posterior position in pro-, meso- and metanotum, exact pattern not discernible owing to preservation, all macrosetae long and with thin barbs along distal half or two-thirds of each macroseta. Legs slender and elongate, with metathoracic leg distinctly longer than others, reaching abdominal segment III; some segments of legs difficult to distinguish owing to preservation; femur longest segment; tibia and tarsus equal in length; tibia with two typical large, stout, simple calcar spurs near ventral apex; tarsus with few visible smooth setae on ventral side; pretarsus with subequal claws, empodium lacking.

Abdomen: Length 1.48 mm, 0.59× length of body. Macrosetae anterior (A) and posterior (P) visible at least from tergites I to VI; macrosetae P visible from tergites VIII to X; all macrosetae long and with thin barbs along distal half or two-thirds of each macroseta. Sternite I with subcylindrical lateral subcoxal appendages, slightly tapered toward tip; styli present from sternites I to VII; measurements of styli and subcoxal appendage not possible owing to preservation; genital papilla not visible. Cercus ( Fig. 2B ) short, length 0.33 mm, 0.13× length of body, slender (segments not compacted), with greatest width in visible segment II, with at least seven segments (basal portion not clearly visible) not counting the infundibuliform complex, without tegumentary expansions or modified setae or other secondary sexual characters on inner side; visible segments I–VII with a distal whorl of smooth setae; visible segment VII terminating in a longitudinally striated excretory tube, the infundibuliform complex.

Figures

Figure 2. Holotype of Electroprojapyx alchemicus gen. et sp. nov. (AMNH JZCBu-1957) in Cretaceous Burmese amber. A, photomicrographs of left ventrolateral habitus of the dipluran fossilized in a preying-and-spraying position with its prey. B, detail of cerci with arrows pointing to the secreted substance. C, camera lucida drawing of the specimen with the secreted filaments in red. D, detail of antennae of the dipluran with the Collembola between them. Abbreviations: b, bubble; scA, lateral subcoxal appendage; stII–stVII, stylus II–VII. Scale bars: 0.5 mm in A, C, D; 0.1 mm in B.