Ectaetia capdoliensis, Fate, Caitlin, Perrichot, Vincent & Nel, Andre, 2013

Fate, Caitlin, Perrichot, Vincent & Nel, Andre, 2013, A Mid Cretaceous representative of the modern scatopsid genus Ectaetia (Diptera: Scatopsidae: Ectaetiinae), Zootaxa 3686 (3), pp. 396-400 : 397-399

Ectaetia capdoliensis sp. n.

( Fig. 1 )

Holotype. Specimen IGR.CDL-7, in amber from Cadeuil, Charente-Maritime, SW France; deposited in the amber collection of the Geological Department and Museum of the University Rennes 1, France.

Diagnosis. Hind tibia swollen; no apical comb of short setae on hind tibia.

Age and outcrop. Mid-Cretaceous, latest Albian or earliest Cenomanian, lithological subunit A1sl-A sensu Perrichot et al. (2010) = A1a/b sensu Néraudeau et al. (2008); Cadeuil, Charente, France.

Etymology. Named after Capdolium, the Latin name of the type locality Cadeuil.

Description. Head 0.17 mm long, 0.25 mm wide, 0.29 mm depth; maxillary palpus small; 12 antennomeres ( Fig. 1 A, 1B); antennal flagellum short, equal to or shorter than depth of head, 0.29 mm long, all antennomeres with setae, short and wider than long, 0.07 mm long; no ocelli visible due to very small bubbles around the head (?); eyes widely separated dorsally and below antennae.

Thorax longer than wide, 0.42 mm long, 0.29 mm wide; no sign of U-shaped ridge though scutum not clearly visible; moderate pilosity of thorax.

Legs. All tibiae without apical spurs; protibia slightly swollen apically; profemur 0.36 mm long, protibia 0.29 mm long, protarsus 0.26 mm long; metafemur 0.37 mm long, metatibia 0.34 mm long, 0.09 mm wide at apex, 0.04 mm at base; metatibia narrow, moderately swollen in distal third, but without any comb of short bristles on inner side ( Fig. 1 D).

Wing with reduced venation ( Fig. 1 C), 0.97 mm long, 0.50 mm wide, veins with setae; membrane without any clear microtrichia or macrotrichia; anal lobe present; anal vein A1 present; veins C, R and Rs darkly pigmented, posterior veins weak; Costa ending at apex of Rs, well before wing apex, 0.71 mm from wing base and 0.59 mm from wing apex, C very slightly swollen at junction with Rs; Rs simple, extending to approximate middle of wing, distance between wing base and apex of Rs 0.71 mm, between apex of Rs and wing apex 0.59 mm; distance between the apices of R1 and Rs 0.29 mm; no cell ‘d’; Rs and M fused and slightly swollen for a short but distinct distance (0.05 mm), stem of M arising from Rs; M distinctly two-branched; length of M1+2 basal of its fork 0.12 mm, length of M1 ca. 0.6 mm, of M2 ca. 0.6 mm; no false, phantom-like vein in area between M2 and CuA1; CuA2 not sharply bent along its course and with no setae; no distinct setae on halter.

Abdomen apparently bare or with very short microtrichia, broad (maybe female specimen), 1.1 mm long; genital structures poorly visible.

Discussion. After Amorim & Grimaldi (2006), Ectaetia capdoliensis sp. n. has the character states “maxillary palpomeres short, stout, reduced in length”, maybe one-segmented (?), “tibial spurs lost”, “Sc incomplete, not reaching C at wing margin”, “R2+3 lost”, “basal cell completely lost”, “R4+5 ending at least about one-third the distance between wing apex and R1”, “R4+5 simple, R4 lost”, “A1 faint, not reaching the wing margin (but as developed as in recent Ectaetia ”, all synapomorphies of the clade ( Axymyiidae , Canthyloscelidae , Scatopsidae , Valeseguyidae ) or (Cantyloscelidae, Scatopsidae , Valeseguyidae ). It has also the character states “medial and cubital wing veins very lightly sclerotized, significantly less than radial veins” and “antennal flagellum short, compact, length shorter or equal to head depth; flagellomeres with stems nestled in concave surface of proximal flagellomere”, synapomorphies of the clade ( Canthyloscelidae + Scatopsidae ), and the character state “flagellum with at most 10 flagellomeres” as a synapomorphy of the Scatopsidae . The simple R4+5 is a character absent in the Canthyloscelidae , the sister group of Scatopsidae .

Following the keys to subfamilies and genera of Cook (1981) or Haenni (1997), Ectaetia capdoliensis falls in the Ectaetiinae because of the following characters: scutum without a U-shaped ridge, fore tibia not produced apically, C not swollen at junction with R4+5; wing with false vein absent; wing membrane without setae, R4+5 and M1+2 fused for a distance, cross-vein R-M obliterated, stem of M1+2 arising distal to base of R4+5. The anterior thoracic spiracle is on a dorsal extension of epimeron I as in the scatopsid subfamilies Aspistinae and Ectaetiinae (Amorim 2000: 1071) .

Amorim (1994) proposed a classification of the Scatopsidae , based on a phylogenetic analysis in which the subfamily Ectaetiinae is respected and includes only the genus Ectaetia . The wing venation of Ectaetia capdoliensis is identical to that of modern Ectaetia species.

Nel & Prokop (2004) described the Paleocene-Eocene genus Paraectaetia, currently considered as a putative Ectaetiinae . This taxon differs from all Ectaetia , including Ectaetia capdoliensis , in its hind tibia not swollen. Ectaetia capdoliensis differs from the modern Ectaetia in the absence of an apical comb of short setae on hind tibia ( Freeman, 1985). The only fossil representative of the genus, Ectaetia fasciola ( Meunier, 1907) from Baltic amber, has wing 1.75 mm long, distinctly longer than in Ectaetia capdoliensis ( Meunier 1907; Amorim 1998). After the direct study of the type of Scatopse fasciola Meunier, 1907 , Haenni (pers. comm.) indicated that this fossil is clearly an Ectaetia for its wing venation, hind tibia swollen in apical third, and presence of the apical comb of short setae on hind tibia.

The larvae of the modern representatives of the genus Ectaetia live in decaying wood, under bark of decaying stumps, or tree trunks lying on the ground, under wet environments ( Rotheray & Horsfield 1997; Krivosheina 2002). A similar ecology can be assumed with a good accuracy for Ectaetia capdoliensis ( Nel 1997) , thus complementing the paleoenvironment already suggested by previous studies for the mid-Cretaceous amber forest of Cadeuil ( Néraudeau et al. 2008; Girard et al. 2009; Perrichot et al. 2010).

Figures

FIGURE 1. Microphotographs of Ectaetia capdoliensis sp. n., holotype IGR. CDL- 7, in Cretaceous French amber. A. Habitus (PL: prothoracic leg; mL: mesothoracic leg; ML: metathoracic leg); B. Detail of head; C. Wing with venation nomenclature; D. Inner side of right metatibia and metatarsi. Scale bars represent 0.25 mm.