First larvae of Raphidioptera from Eocene Sakhalinian and Rovno ambers Author Makarkin, Vladimir N. 0000-0002-1304-0461 Federal Scientific Center of the East Asia Terrestrial Biodiversity, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok, 690022, Russia. vnmakarkin @ mail. ru; https: // orcid. org / 0000 - 0002 - 1304 - 046 vnmakarkin@mail.ru Author Perkovsky, Evgeny E. Schmalhausen Institute of Zoology, National Academy of Sciences of Ukraine, ul. Bogdana Khmel’nitskogo 15, Kiev, 01030 Ukraine; Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya 123, Moscow, 117647, Russia Author Anisyutkin, Leonid N. 0000-0002-7587-9078 Zoological Institute of Russian Academy of Sciences, Universitetskaya nab., 1, Saint-Petersburg, 199034, Russia. https: // orcid. org / 0000 - 0002 - 7587 - 9078 Author Dubovikoff, Dmitry A. Saint-Petersburg State University, 16 - liniya, 29, Saint-Petersburg, 199178, Russia. text Zootaxa 2022 2022-12-13 5219 5 456 466 journal article 207550 10.11646/zootaxa.5219.5.4 7391a03c-6a6e-4f02-9e7e-546c391f1a67 1175-5326 7438997 ECC4C9BF-2E15-4C6A-8C69-C3B8E30A400B Raphidioptera fam. gen. sp. indet. A Figs. 1 , 2 Material examined. Specimen PIN 3387 /175, deposited in the Paleontological Institute , Moscow , Russia . An empty exoskeleton of a partly destroyed larva; only its head, prothorax, and one foreleg are preserved. Syninclusions include the head of a first instar cockroach larva, other crumpled insect fragments, and numerous fungal hyphae . Locality and horizon. Russia : Sakhalin Island: Dolinsk District: the village of Starodubskoye; Sakhalinian amber, middle Eocene ( Baranov et al . 2015 ). Description. Head blackish, not narrowed posteriorly, short, ca . 2 mm long including mandibles, 1.4 mm wide ( ca . 1.43 as long as wide). Ecdysial cleavage lines distinct, consisting of frontal and coronal sutures; frontal sutures diverge at obtuse angle. Antennal socket located at swollen, rounded projection (= antennal tubercle of MacLeod 1964 ). Antenna short; first and third antennomeres elongate, narrow; second antennomere not clearly discernible, probably very short; fourth antennomere poorly discernible, probably much shorter than third antennomere. Stemmata poorly discernible, three detected in dorsal view, one or two in ventral view. Mandibles not protruding, close to head capsule. Palpi not discernible. Pronotum destroyed, blackish, apparently short, 1.45 mm wide, ca . 1.7 mm as preserved. FIGURE 1. Raphidioptera fam. gen. sp. indet. A, specimen PIN 3387/175. A, dorsal view; B, ventral view. fl, foreleg; he, head; pn, pronotum. Scale bar = 1 mm (both to same scale). Foreleg crumpled. Coxa, trochanter not clearly discernible. Femur short, stout, covered with scarce setae. Tibia appears narrow, covered with relatively dense setae. Tarsus rather stout, clearly not conical, covered with relatively dense setae. Claw slightly curved, with basal dilation ( Fig. 2C ). FIGURE 2. Raphidioptera fam. gen. sp. indet. A, details of specimen PIN 3387/175. A, line drawing of the head and pronotum (dorsal view); B, foreleg (ventral view); C, tarsus and claws of foreleg; D, head (dorsal view); E, same (ventral view). a1–a4, 1st to 4th antennomeres; at, antennal tubercle; cl, claw; cs, coronal suture; fe, femur; fs, frontal sutures; md, mandible; or, ocular region; pn, pronotum; ta, tarsus; ti, tibia. Scale bars = 1 mm (A, D, E), 0.5 mm (B), 0.1 mm (C). Remarks. Its one-segmented tarsus indicates that this insect fragment is a larva, certainly belonging to Raphidioptera . The micro-CT shows that it is probably represented by an empty exoskeleton lacking internal tissues and air bubbles. The larva somewhat resembles those of some Hydrophilidae and Gyrinidae (Coleoptera) ( e.g ., Michat et al . 2010 ; Minoshima & Hayashi 2012 ), but differs from these by some details, e.g ., these coleopteran larvae possess the anterior margin of the clypeolabrum furnished with projections; or their antennae are relatively long; or their mandibles are long with the inner teeth. It differs from the larvae of Megaloptera in particular by the relatively long head (it is usually short and rounded in Megaloptera) and the very short coxa (relatively long in Megaloptera). The head of larval Raphidioptera usually bears projecting mandibles, but this larva is unusual, similar to that of the extant Phaeostigma notatum ( Fabricius, 1781 ) , in which mandibles do not project (see Beutel & Ge 2008 : Fig. 1C ). We follow the antennal segmentation interpretation of Beutel & Ge (2008) . This approach seems reasonable. Indeed, as in their understanding, the antennal tubercle of this larva is obviously not a part of the antenna. We think that Haug et al . (2022) incorrectly interpreted the antennal segmentation in fossil Raphidioptera larvae. They considered the antennal tubercle as the first antennal antennomere (their ‘element’), and the very short second ‘element’ to be not an antennomere, although it is well discernible as such in some photographs (see e.g ., Haug et al . 2022 : Fig. 11a). According to Aspöck et al . (1991) , the antenna of Raphidioptera larvae is three-segmented; they consider the antennal tubercle as a possible other, basal antennomere, and the second antennomere of Beutel & Ge (2008) as an inconspicuous sclerite between the two long basal antennomeres. According to Tauber (1991) , the antenna is four-segmented, but she did not indicate if the fourth antennomere is the antennal tubercle or the second (shortest) antennomere of Beutel & Ge (2008) .