A new genus of dance fly (Diptera: Empidoidea: Hybotidae) from Cretaceous Spanish ambers and introduction to the fossiliferous amber outcrop of La Hoya (Castellón Province, Spain)

Abstract

Hybotidae fly species, also known as dance flies, in Cretaceous ambers have been described from Lebanon, France, Myanmar, Russia, and Canada. Here we describe Grimaldipeza coelica gen. et sp. n., and recognize another two un-named species, in Spanish amber from the middle Albian El Soplao and lower Cenomanian La Hoya outcrops. The fore tibial gland is present in the new genus, which is characteristic of the family Hybotidae. We compare Grimaldipeza coelica gen. et sp. n. with the holotypes of Trichinites cretaceus Hennig, 1970 and Ecommocydromia difficilis Schlüter, 1978, and clarify some morphological details present in the latter two species. Further taxonomic placement beyond family of the here described new genus was not possible and remains incertae sedis within Hybotidae until extant subfamilies are better defined. We provide new paleoecological data of the hybotids, together with paleogeographical and life paleoenvironmental notes. A table with the known Cretaceous Hybotidae is provided. Furthermore, the La Hoya amber-bearing outcrop is described in detail, filling the information gap for this deposit.

Keywords: Amber; Amber-bearing outcrop; Ecommocydromia; New genus; New species; Trichinites.

Figure 1. The lower Cenomanian (Upper Cretaceous) amber-bearing outcrop of La Hoya (Maestrazgo Basin, Castellón Province, Spain).

(A) Geographical location within the Iberian Peninsula of the El Soplao (middle Albian) and La Hoya amber outcrops, and geological location of the La Hoya outcrop; Cortes de Arenoso village and the fossiliferous Arroyo de la Pascueta amber outcrop (late Albian) are also indicated in the geological map. (B) Amber-bearing level of the La Hoya outcrop, constituted by grey-black mudstone rich in organic matter, at the top of the Cortes de Arenoso section (E. Barrón, 2022, personal communication). (C) An amber piece in the rock of the La Hoya outcrop. Geological map in A modified and simplified from Almera, Anadón & Godoy (1977).

Figure 2. Grimaldipeza coelica n. gen. et sp. (Diptera: Hybotidae) , holotype male CES.404.1 and paratype male CES.404.2, from El Soplao outcrop, Cantabria, Spain (middle Albian in age).

(A) Piece showing two specimens (holotype, left; paratype, right). (B) Habitus of holotype CES.404.1, lateral view. (C) Habitus of holotype CES.404.1, dorsal view. Scale bars 0.5 mm.

Figure 3. Important characters of Grimaldipeza coelica n. gen. et sp. (Diptera: Hybotidae), holotype male CES.404.1 and paratype male CES.404.2, from El Soplao outcrop, Cantabria, Spain (middle Albian in age).

(A) Head of holotype CES.404.1, ventral view. (B) Head of paratype male, dorsal view. (C) Antennae of holotype. (D) Thorax of holotype, dorsal view. (F) Drawing of thorax of holotype, dorsal view. (G) Hindlegs of holotype. (H) Male terminalia of holotype, lateral view. (I) Male terminalia of holotype, Ia laterodorsal right, Ib lateroventral left. (J) Male terminalia of paratype male. Scale bars (A–C) and (H–J), 0.1 mm, (D–G) 0.5 mm. Abbreviations: cerc, cercus; dc s, dorsocentral setae; hypd, hypandrium; hyprct, hypoproct; lbr, labrum; ph, phallus; spal s, supra-alar seta; styl, stylus; sur, surstylus.

Figure 4. Grimaldipeza coelica n. gen. et sp. (Diptera: Hybotidae), paratype male CES.439, from El Soplao outcrop, Cantabria, Spain (middle Albian in age).

(A) Habitus, lateral view. (B) Drawing of habitus, lateral view. (C) Head, ventrolateral view. (D) Mouthparts. (E) Male terminalia, laterodorsal view. (F) Photo of male terminalia, laterodorsal view and hindleg. Black arrows show the longitudinal furrow on hind femur and tibia. (G) Reconstruction of wing. Scale bars (A, B and G) 0.5 mm, (C–F) 0.1 mm. Abbreviations: bm, basal medial cell; cua, anterior cubital cell; CuA+CuP, anterior branch of cubital vein + posterior branch of cubital vein; dm, discal medial cell; M, medial vein; R, radial vein; Sc, subcostal.

Figure 5. Fore tibial gland in Grimaldipeza coelica n. gen. et sp. (Diptera: Hybotidae), from El Soplao outcrop, Cantabria, Spain (middle Albian in age).

(A) Holotype CES.404.1, with close-up of gland. (B) Paratype CES.439, with close-up of gland. (C) Paratype CES.404.1. (D) Female, CES.372. Scale bars (A–C) 0.5 mm, (a, b and D) 0.1 mm. Abbreviation: gl, gland.

Figure 6. Female Grimaldipeza sp. 1. (Diptera: Hybotidae), female CES.372, from El Soplao outcrop, Cantabria, Spain (middle Albian in age).

(A) Habitus. (B) Drawing of habitus with photo showing thoracic setae with apparent seriated rings (scale bar 0.1 mm). (C) Mouthparts. (D) Antennae. (E) Anterior part of wing. (F) Terminalia. Scale bars (A, B, and E) 0.5 mm; (C, D and F) 0.1 mm. Abbreviations: cerc, cercus; lbl, labrum; psdtrch, pseudotrachea; R, radial vein; Sc, subcostal; tg, tergite.

Figure 7. Grimaldipeza sp. 2. (Diptera: Hybotidae), MGUV-16348 (sex unknown), from La Hoya outcrop, Castellón, Spain (early Cenomanian in age).

(A) Habitus, lateral view right. (B) Habitus, lateral view left. (C) Drawing of habitus, lateral view. (D) Head, laterofrontal view. (E) Wing reconstruction. (F) Antenna. Scale bars (A–E) 0.5 mm; (F) 0.1 mm. Abbreviations: CuA+CuP, anterior branch of cubital vein + posterior branch of cubital vein; dm, discal medial cell; M, medial vein; R, radial vein; Sc, subcostal.

Figure 8. Trichinites cretaceus Hennig, 1970, holotype Number LB-617, from Jezzine outcrop, Lebanon (Barremian in age).

(A) Scutum and wing, dorsal view. (B) Thorax, oblique lateral view. (C) Antenna with one basal article. (D) Holotype with labels. Scale bars (A–C) 0.5 mm, (D) 10 mm. Abbreviation: styl, stylus.

Figure 9. Ecommocydromia difficilis Schlüter, 1978, from Écommoy, France (Cenomanian in age).

(A) Habitus in left lateral view. (B) Habitus in right lateral view. (C) Terminalia in left lateral view. (D) Drawing of terminalia in left lateral view. (E) Antenna. (F) Drawing of antenna. (G) Foreleg. (H) Forelegs photographed with infrared camera, red arrow indicates possible posteroventral gland, however it could also be an artifact. (I) Holotype with labels. Scale bars (A and B) 0.5 mm, (C–H) 0.1 mm, (I) 5 mm. Abbreviations: cerc, cercus; hypd, hypandrium; pgt, postgonite; ph process, phallic process; sur, surstylus.

Figure 10. Infrared spectroscopy spectrum (FTIR) from an aerial amber piece of La Hoya outcrop (Castellón Province, Spain).

Resolution = 4 cm⁻¹.