Rostricampa Sánchez-García, Sendra and Grimaldi

Sánchez-García, Alba, Sendra, Alberto, Davis, Steven R. & Grimaldi, David A., 2024, ‘ Dawn’ hexapods in Cenozoic ambers (Diplura: Campodeoidea), Zoological Journal of the Linnean Society 201 (1), pp. 136-158 : 149-154

Rostricampa Sánchez-García, Sendra and Grimaldi gen nov.

LSID: urn:lsid:zoobank.org:act:A4331BAB-13E2-494A-AF61-1226546147A1

Etymology: The generic name is a combination of the Latin rostrum (bill, beak, snout, muzzle) and the typical suffix for campodeids, campa. Gender of the name is feminine.

Type species: Rostricampa engeli Sánchez-García, Sendra and Grimaldi sp. nov. by monotypy.

Diagnosis: Male. Frontal process, clypeus and labium forming a sclerotized ‘beak’ protruding from head. Antenna with at least 20 antennomeres, moniliform. Distribution of thoracic macrosetae: pronotum with 1 + 1 la, 1 + 1 lp; mesonotum with 1 + 1 ma, 1 + 1 la 1 + 1 lp; metanotum with 1 + 1 lp; marginal setae thin. Metathoracic leg reaching abdominal segment IV; femur without dorsal macrosetae and with one ventral macroseta; tibia with one ventral macroseta; claws subequal, with small lateral crests; pretarsal lateral processes laminar and curved, smooth. Styli with a ventromedial macroseta bi- or trifurcate. Cerci slightly shorter than body, with 25 articles, with whorls of setae and macrosetae both barbed and smooth. Male urosternite I with enlarged subtrapezoidal subcoxal appendages with glandular setae in a large distal area.

Rostricampa engeli Sánchez-García, Sendra and Grimaldi sp. nov.

( Figs 11–14 )

LSID: urn:lsid:zoobank.org:act:C9561FC1-BAC2-44F4-8FAA-7D7E2CD53F06

Etymology: The specific epithet is a patronym in honour of a great mentor, colleague and entomologist, Dr Michael S. Engel.

Material: Holotype AMNH DR-KLCa002, male, adult; donated by K. Luzzi and held in the AMNH; specimen virtually complete, with tips of both antennae cut off at the amber surface; a reddish halo is around most of the specimen; there are bubbles in the anterior and posterior part of the body, and all abdominal vesicles are extruded, probably as a stress behaviour attributable to being trapped in resin; observable laterally (both sides) and dorsally; the piece is very transparent, orange in colour, embedded in a small block of EpoTek resin trimmed to 1.0 cm × 1.0 cm × 0.4 cm; syninclusions include one acari.

Occurrence: Miocene, Dominican Republic.

Diagnosis: As for genus, by monotypy.

Description: Male, adult.

Body: Length 4.66 mm ( Fig. 11A ). Cuticle very irregular and webby, probably owing to slightly pyritized nature of the specimen (there is a reddish halo around most of the specimen), with no distinct microstructures, probably smooth; body with short, thin, clothing setae, smooth or with few thin distal barbs.

Head: Length 0.73 mm, 0.16 × length of body. Frontal process well developed, together with an elongated clypeus and probably the labium that form a tapered, apparently sclerotized ‘beak’ protruding from head ( Fig. 11B ); on the lateral side is a group of ~20 very fine setae, three of these close to the base of the antenna raised into low tubercles, which might be membranous ( Fig. 11C ); apical part of head showing a higher grade of sclerotization. Labial palp suboval and small, setose. Both antennae incomplete, maximum length as preserved 2.10 mm, with ≥ 20 antennomeres; base of the antenna with a rather large recessed area, the margins of which form a steep edge; antennomeres I and II subrectangular; antennomere III onwards moniliform, twice as long as wide (length 0.12 mm, width 0.06 mm); trichobothria visible in antennomeres III– VI ( Fig. 13A ); medial and distal antennomeres with whorls of barbed setae combined with whorls of smooth setae ( Fig. 13A ).

Thorax: Length 1.43 mm, 0.31 × length of body. Distribution of macrosetae: pronotum with 1 + 1 la, 1 + 1 lp, ma not visible; mesonotum with 1 + 1 ma, 1 + 1 la, 1 + 1 lp; metanotum with 1 + 1 lp, ma not visible; macrosetae very long and thin, barbed on one side along distal half or third; marginal setae longer than clothing setae and thin, with a few thin distal barbs. Legs slightly elongated; metathoracic leg reaching abdominal segment IV; length of metathoracic leg segments: femur 0.36 mm, tibia 0.37 mm, tarsus including pretarsus 0.29 mm; femur with one long, thin ventral macroseta, with short barbs along distal half or third ( Fig. 13B ); tibia with one long ventral macroseta, and two thin calcars with short barbs distally; femur and tibia without dorsal macrosetae; tarsus with typical setae along ventral side; subapical tarsal setae longer than other tarsal setae; pretarsus with subequal claws, with small lateral crests; pretarsal lateral processes laminar and curved ( Fig. 13C ).

Abdomen: Length 2.50 mm, 0.54 × length of body. Visible macrosetae on tergites: V–VII with 2 macrosetae; VIII–IX with 3 + 3 lp; X with 2 macrosetae; macrosetae very long and thin, barbed along distal half or third. Pairs of styli and eversible vesicles present from sternites II to VII ( Fig. 13E, F ); stylus length 0.07 mm, width 0.02 mm, with fine transverse wrinkling; stylus with smooth apical and subapical macrosetae plus a ventromedial macroseta always bifurcate (in one it is trifurcate); overall, there are six to seven setae on the stylus. On the side of the stylus opposite the eversible vesicle is a pair of long macrosetae, barbedalongdistalhalforthird, visiblefromsternites I to VII; the macroseta closest to the stylus is shortest; all eversible vesicles extruded, ovoid, of variable dimensions. Both cerci complete (non-regenerated), length 4.26 mm, 0.91 × length of body; with 25 articles, length of basal articles 0.10 mm, length of medial and distal articles 0.25 mm; with two medial whorls of long, thin macrosetae with thin barbs along distal half, accompanied by two whorls of long, thin, smooth setae, plus a distal whorl of thin, short, smooth setae.

Secondary sexual characters: Male urosternite I with thick, large, subtrapezoidal subcoxal appendages ( Fig. 13D ), length 0.13 mm, basal width 0.04 mm, distal width 0.09 mm, with glandular setae in a large distal area.

Remarks: Rostricampa engeli fits within the subfamily Campodeinae owing to the presence of a maximum of 3 + 3 macrosetae on the pronotum ( Condé 1956, Paclt 1957). However, the morphology of the new taxon is remarkably different from any other Diplura. The excellent preservation of the fossil and the use of various techniques for its examination has allowed us to describe the extraordinary morphology of the head (uniquely modified among all Diplura), which is characterized by a sclerotized ‘beak’ protruding from head. Among Campodeinae , Ro. engeli resembles the genus Campodea by the presence of 3 + 3 M (ma, la, lp) on the pro- and mesonotum, the metanotum with lp macrosetae, and the presence of non-setose lateral processes of the pretarsus ( Condé 1956, Paclt 1957). The specimen is identified as an adult male owing to the presence of the enlarged subcoxal appendages of the urosternite I.

Figures

Figure 11. Dorsal photomicrograph of holotype of Rostricampa engeli, AMNH DR-KLCa002, in Miocene Dominican amber.A, dorsolateral habitus. B, detail of head in lateral view.C, detail of anterior part of the head.

Figure 12. Camera lucida drawings of holotype of Rostricampa engeli, AMNH DR-KLCa002, in Miocene Dominican amber. A, detail of head. B, dorsolateral habitus. C, detail of stylus and eversible vesicle of urosternite II. D, detail of stylus and eversible vesicle of urosternite V. E, detail of stylus and eversible vesicle of urosternite VI.

Figure 13. Photomicrographs of holotype of Rostricampa engeli, AMNH DR-KLCa002, in Miocene Dominican amber. A, detail of left antennomeres IV–VI.B, detail of ventral femoral macroseta of right leg I. C, detail of pretarsus; asterisks indicate the lateral processes. D, detail of subcoxal appendage of urosternite I. E, detail of stylus and eversible vesicle of urosternite V.F, detail of stylus and eversible vesicle of urosternite VI. Abbreviations: T, trichobothria.

Figure 14. Computed tomography scan images of holotype of Rostricampa engeli, AMNH DR-KLCa002, in Miocene Dominican amber. A, lateral habitus of anterior part of body. B, dorsal habitus of anterior part of body. C, head in dorsal view. D, head in ventral view. E, head in lateral view.A–B and C–E are to the same scale.