Ferriantenna excalibur gen. et, 2021

Cumming, Royce T. & Tirant, Ste ́ phane Le, 2021, Drawing the Excalibur bug from the stone: adding credibility to the double-edged sword hypothesis of coreid evolution (Hemiptera, Coreidae), ZooKeys 1043, pp. 117-131 : 117

Ferriantenna excalibur gen. et sp. nov. Figures 2A , 3 , 4

Material examined.

Holotype: Amber specimen #BHM10200800678. Flat and round rectangular piece of amber, approximately 1.0 cm by 1.1 cm with high clarity and small debris throughout that does not black visibility of the specimen (Fig. 3C ). Specimen partially complete yet well-preserved, likely fourth instar. Missing the terminal two or three segments of the abdomen. Deposited in the Montreal Insectarium (IMQC). Unknown sex.

Type locality and horizon.

Kachin State, Myanmar; Upper Cretaceous ~98.79 ± 0.62 million years old ( Shi et al. 2012). At present we are only aware of this genus and species being found in northern Myanmar from this stratum.

Differentiation.

At present this is the only formally described species within this new genus. Refer to the differentiation within the above genus section for discussion on the closely related Magnusantenna wuae . We are aware of a second, undescribed Ferriantenna gen. nov. species (Fig. 2B ) which differs by having the second and third antennomeres which are heavily armored with tubercles, not flattened with each segment narrow at the base and widening gradually to the sharply pointed anterior like is seen in Ferriantenna excalibur gen. et sp. nov. (Fig. 2A ). The elaborate antennae differentiate these extinct species from all known extant coreids which at most have a single slightly expanded antennal segment.

Description.

Mostly complete nymph which appears to be fourth instar. Sex unknown due to the instar stage and missing terminalia of the abdomen. Specimen complete except for the terminal two or three abdominal segments (Fig. 3A ). Overall length (including antennae) 6.87 mm (measured to the end of the abdomen which is missing the terminal segments, so the actual length of the insect is slightly longer).

Head. Antennal socket protruding from the front of the head (Fig. 4B ), approximately 0.11 long by 0.20 mm wide, about as wide as the first antennomere. Head subquadrate, 0.50 mm long by 0.46 mm wide (without including compound eyes), including compound eyes head is 0.76 mm wide. Vertex relatively smooth, no notable textures or structures (Fig. 4B ). Clypeus protruding slightly, labrum stout, not prominent. Labium tetramerous, fully extended reaches beyond the apex of the second antennomere, labiomeres one, two, and three similar in length, four approximately half as long as any of the others (Fig. 4A ). Apex of the fourth labiomere sharply tapering to a fine point (Fig. 4A ). Lengths: first labiomere 0.41 mm, second labiomere 0.51 mm, third labiomere 0.39 mm, fourth labiomere 0.26 mm. Compound eyes prominently protruding but not overly large, located in the center and taking up approximately one third of the lateral head margins (Fig. 4B ).

Antennae. Antennae tetramerous (Fig. 3B ), length 3.22 mm, approximately equal in length to the damaged holotype body length (if the abdomen were complete the antennae would be slightly shorter in length than the body). First antennomere tubular, with sparse and short setae, 0.28 mm long and 0.14 mm wide. Antennomeres two through four appear to be laterally flattened due to the way the antennae are held in the amber. Second antennomere approximately right triangular in shape, with the anterior wide and the posterior narrow and the triangular expansion raised dorsally. Margins finely granular, with the dorsal margin marked with few fine setae, the ventral margin is marked with slightly longer and more prominent setae. Antennomere surfaces are relatively smooth, with minimal setae and only prominent granulation along the margins. Second antennomere length 1.08 mm and maximum width (on the anterior end) 0.39 mm. Third antennomere similar in shape and texture to the second antennomere but slightly wider throughout the length and on the anterior than the second antennomere; approximately right triangular in shape, with the anterior wide and the posterior narrow with the triangular expansion raised dorsally. Margins finely granular, with the dorsal margin with only fine setae, the ventral margin with slightly longer and more prominent setae. Antennomere surfaces relatively smooth, with minimal setae and fine granulation along the margins. Third antennomere 1.15 mm long and maximum width (on the anterior end) 0.52 mm. Fourth antennomere paddle-shaped and notably smaller than the previous two, with a narrow base expanding into a rounded segment; 0.71 mm long and 0.40 mm at the widest point (in the center). Fourth antennomere surfaces are more setose than the previous two antennomeres, marked throughout by moderate fine granulation. Margins with smaller and finer granulation and setae than on the previous two antennomeres.

Thorax. Pronotum approximately an isosceles trapezium, anterior three fifths gradually expanding to the widest point, then the posterior two fifths converge slightly to the posterior (Fig. 4B ). Dorsal surface of pronotum smooth, lacking prominent features. Overall pronotum length 0.73 mm, minimum width (on the anterior) 0.48 mm, width of the posterior 0.66 mm, maximum width on the posterior two fifths 0.72 mm. Mesonotum broader than long, with lateral margins expanding slightly on the anterior half and then contract slightly to the posterior (Fig. 4B ). Overall mesonotum length 0.55 mm and greatest width 0.67 mm. Metanotum with anterior and posterior margins the same width, 0.60 mm, overall metanotum length 0.55 mm and maximum width (in the center) 0.65 mm.

Legs. All legs of a similar morphology, only slight differences in length differentiate them (Fig. 4D ). All femora of a uniform width, and all tibiae of a uniform width. Femora tubular, with a surface texture that is mostly smooth, but with a slight granular texture in places but not throughout. At the femora and tibiae joint the femora have a single spine-like projection on each side projecting outward and slightly towards the tibiae (Fig. 4D ). Tibiae are half as wide as the femoral widths. Tibiae on the proximal end start out smooth but gradually become heavily setose along the ventral and lateral surfaces. At the apex of the tibiae the setae are rather prominent, and the setae continue on under the tarsomeres, albeit slightly more sparse, not as dense as the apex of the tibiae (Fig. 4C ). Tarsi with two tarsomeres, apex with two distinct claws, each with a prominent pulvillus (Fig. 4C ). Leg segment lengths: profemora 0.66 mm, mesofemora 0.60 mm, metafemora 0.77 mm, protibiae 0.62 mm, mesotibae 0.58 mm, metatibiae 0.94 mm.

Abdomen. Abdomen notably damaged in the holotype. Disconnected from the body following the second segment, the remainder is mostly crushed, and the terminal two or three segments are missing (Fig. 3A ). Greatest width approximately 0.55 mm. Abdomen without notable structures, margins parallel sided with rather smooth transitions from one segment to the next.

Etymology.

Noun in apposition, given for Excalibur, the mythical "sword in the stone" which was first described in the epic poem Merlin (about the mythical advisor to King Arthur), written by the French poet Robert de Boron sometime between 1195-1210 ( Reeve and Wright 2007) which was a reworking of Geoffrey of Monmouth’s "Historia Regum Britanniae", completed c. 1138 ( Wright 1985). Within this poem is the first mention of Excalibur being the sword in the stone, which could only be removed by the true king of England. We felt that this specific epithet was fitting as this group of insects with exaggerated antennae were first described as a possible "double edged sword in evolution" as these elaborate antennae went extinct ( Du et al. 2021). We felt this witty description, coupled with the insect being trapped in stone (amber) was fitting for such a long lost, and therefore mythical species.

Figures

Figure 2. Artist recreation of the presently known three Cretaceous coreids with elaborate antennae. Illustrations by Liz Sisk (USA). Dorsal habitus scaled to same uniform length to highlight the antennae to body ratios. Colorations are artistic recreations based upon extant coreids rather than the actual specimen, whose color was not preserved in the amber A Ferriantenna excalibur gen. et sp. nov. B Ferriantenna " club-like antennae " C Magnusantenna wuae.

Figure 3. Ferriantenna excalibur gen. et sp. nov. holotype A dorsolateral habitus B left antennae lateral and head dorsal C amber specimen BHM 10200800678 showing the inclusion.

Figure 4. Ferriantenna excalibur gen. et sp. nov. holotype A extended labium with stylet exposed to the right B head, pronotum, and mesonotum, dorsal C left tarsi and distal ends of the tibiae D legs on the left side, dorsolateral.