‘ Dawn’ hexapods in Cenozoic ambers (Diplura: Campodeoidea) Author Sánchez-García, Alba Instituto Geológico y Minero de España (IGME), CSIC, València, Spain alba.sanchez@csic.es Author Sendra, Alberto Coleccions Torres-Sala i Siro de Fez, Servei de Patrimoni Històric, Ajuntament de València, València, Spain & Departament de Didàctica de les Ciències Experimentals i Socials, Facultat de Magisteri, Universitat de València, València, Spain Author Davis, Steven R. Division of Invertebrate Zoology, American Museum of Natural History, New York, NY, USA Author Grimaldi, David A. Division of Invertebrate Zoology, American Museum of Natural History, New York, NY, USA text Zoological Journal of the Linnean Society 2024 2023-09-30 201 1 136 158 http://dx.doi.org/10.1093/zoolinnean/zlad118 journal article 10.1093/zoolinnean/zlad118 0024-4082 11241048 Genus Lepidocampa Oudemans, 1890 Type species: Lepidocampa weberii Oudemans, 1890 . Lepidocampa glaesi Sánchez-García, Sendra and Grimaldi sp. nov. ( Figs 1–6 ) LSID: urn:lsid:zoobank.org:act: 097BDB05-DBC5-42A5-A010- 566BD0EC0CDD Etymology: The specific epithet is from the Latin glaesum , meaning ‘of amber’. Material: Holotype AMNH DR-KLCa001 ( Figs 1–3 ), sex unknown, adult; donated by K. Luzzi in 2015 and held in the AMNH ; specimen virtually complete and observable dorsally and ventrally; preserved in a rectangular chip of transparent orange amber trimmed to 5 mm × 4 mm × 1 mm (not included in epoxy); syninclusions include a larval head of an unidentified insect. The specimen shows indirect evidence of the digestive tract from fossilized contents (termed ‘cololite’). Other material examined: M-982 ( Figs 4–6 ), female, adult; Ettore Morone collection, Turin, Italy (available through the AMNH); specimen virtually complete and observable dorsally and ventrally; the piece is a very transparent orange colour, rounded in shape (not included in epoxy). Occurrence: Miocene, Dominican Republic . Diagnosis: Cuticle smooth, with thoracic and abdominal sclerites covered by scales instead of clothing setae. Frontal process not protruding. Antenna two-fifth length of body, with 25 antennomeres, dolioform; cupuliform organ with sensilla. Macrosetae ma present on metanotum; marginal setae robust. Metathoracic leg reaching abdominal segment V; femur without dorsal macrosetae and with two ventral macrosetae; tibia with one ventral macroseta; tarsus abruptly ended; claws subequal and well curved, with a long unguiculus between them; pretarsal lateral processes laminar and setose. Cerci half the length of the body, with whorls of setae and macrosetae both barbed and smooth. Female urosternite I with small subcylindrical subcoxal appendages with glandular setae. Figure 1. Ventral photomicrograph of holotype of Lepidocampa glaesi , AMNH DR-KLCa001 , in Miocene Dominican amber. Figure 2. Camera lucida drawings of holotype of Lepidocampa glaesi , AMNH DR-KLCa001 , in Miocene Dominican amber. A, detail of pretarsus of left leg III. B, detail of pretarsus of left leg II. C, detail of stylus. D, ventral habitus. E, detail of cupuliform organ of left antenna. Figure 3. Photomicrographs of holotype of Lepidocampa glaesi , AMNH DR-KLCa001 , in Miocene Dominican amber. A, detail of pretarsus of left leg III, showing the laminar lateral process. B, same pretarsus as in A, showing the claw. C, detail of pretarsus of left leg II. D, detail of scales. E, detail of femora of left leg III, showing the two ventral macrosetae. F, detail of cupuliform organ. G, detail of an abdominal stylus and post macrosetae of abdominal segment VIII. Figure 4. Photomicrographs of Lepidocampa glaesi , M-982, in Miocene Dominican amber. A, ventral habitus. B, dorsal habitus. Both to the same scale. Figure 5. Photomicrographs of Lepidocampa glaesi , M-982, in Miocene Dominican amber. A, detail of head and thorax in dorsal view. B, detail of abdomen. Figure 6. Computed tomography scan images of Lepidocampa glaesi , M-982, in Miocene Dominican amber. A, ventral habitus. B, dorsal habitus. Both to the same scale. Description (based on holotype ): Sex unknown, adult. Body: Length 1.72 mm (excluding antennae and cerci). Cuticle smooth under compound microscope; clothing setae replaced by scales on thoracic and abdominal sclerites ( Figs 3D , 5 ). Head: Length 0.33 mm , 0.19 × length of body. Frontal process not protruding. Labial palp not visible in holotype . Antenna (non-regenerated) length 0.67 mm , 0.39 × length of body, with 25 antennomeres; antennomeres dolioform,telescoped, nearly as long as wide (length 0.04 mm , width 0.05 mm ); apical antennomere length 0.05 mm , width 0.03 mm , with a cupuliform organ occupying one-ninth of its length, containing some apparently simple sensilla ( Figs 2E , 3F ); trichobothria visible in antennomeres III– VI ; medial and distal antennomeres with one or two whorls of short, thin and smooth setae, the distal-most antennomere with an additional whorl of setae around the cupuliform organ . Thorax: Length 0.42 mm , 0.24 × length of body. Visible macrosetae on tergites (distribution impossible to assess owing to preservation): mesonotum with one la , metanotum with one lp ; macrosetae barbed on one side along distal half or two-thirds. Legs slightly elongated, metathoracic leg reaching abdominal segment V; length of metathoracic leg segments: femur 0.20 mm , tibia 0.24 mm , tarsus including pretarsus 0.17 mm ; femur with two long, thin, barbed ventral macrosetae ( Fig. 3E ); tibia with one long, thin smooth ventral macroseta and two regular calcars distally; femur and tibia without dorsal macrosetae; tarsus abruptly ended, with typical setae along ventral side; pretarsus with subequal and well-curved claws, with a long unguiculus between them ( Figs 2B , 3C ); pretarsal lateral processes laminar, covered by long setae ( Figs 2A, B , 3A–C ). Abdomen: Length 0.97 mm , 0.56 × length of body. Distribution of abdominal macrosetae on tergites: at least 1 + 1 post on IV– V , 2 + 2 post on VI – VIII , 3 + 3 post on IX and 6 + 6 on X; macrosetae long and barbed on one side along distal half or two-thirds. Urosternite details mostly obscured in holotype (only one stylus visible on segment VIII ); stylus with one long, strong, smooth apical seta, and less conspicuous subapical and ventromedial setae ( Figs 2C , 3G ). Both cerci complete (regenerated), length 0.86 mm , 0.50 × length of body, with articles not discernible, bearing whorls of long barbed macrosetae accompanied by whorls of smooth setae . Descriptive notes on specimen M-982: Female, adult. General description is as for the holotype , with the following measurements: body length 2.47 mm ; head length 0.4 mm , 0.16 × length of body. Labial palp suboval and small, setose. Antenna length 1.32 mm , 0.53 × length of body, with 25 antennomeres; trichobothria visible in antennomeres III– VI ; cupuliform organ not visible, although the surrounding whorl of setae is distinguishable. Thorax length 0.69 mm , 0.28 × length of body. Distribution of macrosetae: pronotum with 1 + 1 ma , mesonotum with 1 + 1 la and 1 + 1 lp , metanotum 1 + 1 ma and 1 + 1 lp; marginal setae longer than clothing setae and robust, with barbs as for macrosetae. Legs normal, femur 0.28 mm , tibia 0.27 mm , tarsus 0.21 mm ; unguiculus and telotarsal processes not visible. Abdomen length 1.38 mm , 0.56 × length of body. Distribution of abdominal macrosetae on tergites: 2 + 2 post on IV–VII, 4 + 4 post on VIII –IX, 6 + 6 post on X. Pairs of styli and eversible vesicles present from sternites II to VII; stylus length 0.08 mm , width 0.02 mm ; all eversible vesicles extruded, ovoid, of variable dimensions. Cerci length 1.41 mm , 0.57 × length of body . Secondary sexual characters: Female urosternite I with a pair of subcylindrical subcoxal appendages not widened distally ( Fig. 6A), length 0.06 mm , width 0.04 mm , with a glandular area distally. Remarks: Among Campodeidae , three of the five subfamilies have scales on the body: Lepidocampinae Condé, 1956 , Syncampinae Paclt, 1957 and Hemicampinae Condé, 1956 . These subfamilies represent only 5% of extant Campodeidae diversity ( Sendra et al. 2021 ). Lepidocampinae and Syncampinae have scales on the thorax and abdomen, whereas Hemicampinae have scales only on the abdomen ( Condé 1956 , Paclt 1957). Lepidocampa glaesi fits in Lepidocampinae owing to the presence of scales on the thorax and abdomen and the morphology of the pretarsus, bearing a long unguiculus between the claws. Assignment in Syncampinae is precluded by the absence of the unguiculus in this subfamily. The subfamily Lepidocampinae includes the genera Sinocampa Chou & Chen, 1981 and Lepidocampa Oudemans, 1890 . Both genera differ only in the morphology of the pretarsus, with Sinocampa bearing slender and plumose lateral processes and Lepidocampa laminar and setose processes. This new species fits into the genus Lepidocampa owing to the morphology of the pretarsus (with laminar and setose lateral processes), regular curved claws, and the tarsus abruptly ended, among other features. The validity of the subgenera described in Lepidocampa ( Paracampa Condé, 1956 and Lepidocampa s.s. Oudemans, 1890) has been questioned with morphological and molecular evidence ( Luan et al. 2004 , Sendra et al. 2017 ); therefore, comparisons are made only for descriptive purposes. Following Condé (1993) , Le. glaesi fits in Lepidocampa s.s. by antennae with 16–46 antennomeres, ma present on metanotum, and cerci with whorls of long, barbed and smooth macrosetae, whereas the subgenus Paracampa has 14–23 antennomeres, ma absent, and cerci with short, smooth macrosetae. It is also worthy of mention that Le. glaesi lacks dorsal macrosetae on femur III, a condition seen in all described Paracampa ( Lepidocampa polettii , Silvestri, 1931 , Lepidocampa takahashii Silvestri, 1931 and Lepidocampa gravelyi Silvestri, 1933 ) but variable in Lepidocampa s.s . To date, only the species described herein, in addition to two species in Lepidocampa s.s . [ Lepidocampa (L.) hypogaea Condé, 1992 and Lepidocampa (L.) beltrani Sendra, 2017 ] have femora without dorsal macrosetae. However, these two species have ma present on the meso- and metanotum ( Condé 1993 ; Sendra et al. 2017 ), whereas ma are present only on the metanotum in the new species. Both specimens are adults based on the development of the vestiture. Direct sexual assignment is not possible because the genital papilla on sternite VIII is not visible in any of the specimens. However, the specimen M-982 is likely to be a female owing to appendages on urosternite I that are not enlarged.