Gryllobencain patrickmuelleri, Haug, Joachim T., Hörnig, Marie K., Kiesmüller, Christine, Pazinato, Paula G., Baranov, Viktor & Haug, Carolin, 2022

Haug, Joachim T., Hörnig, Marie K., Kiesmüller, Christine, Pazinato, Paula G., Baranov, Viktor & Haug, Carolin, 2022, A 100 - million-year-old ensiferan with unusual mouthparts and comments on the evolution of raptorial appendages within Polyneoptera, Geodiversitas 44 (4), pp. 57-73 : 60-67

Gryllobencain patrickmuelleri n. gen., n. sp.

urn:lsid:zoobank.org:act:80C207C0-1B2E-44F9-90F8-A53E9229461B

HOLOTYPE. — PED 0147 .

PARATYPE. — PED 0178 .

ADDITIONAL MATERIAL. — BUB 3072 , 3073 , from the collection of Patrick Müller.

DERIVATIO NOMINIS. — In honour of Patrick Müller and his effort for research, especially on Myanmar amber.

DIAGNOSIS. — Specimen with prominent maxillae [maxillulae]; medio-proximal part prominent sickle-shaped; palp prominent with long and strong setae; foreleg and mid leg [thorax appendages 1 and 2] with many long and strong setae mostly medially, on femur and tibia. Tibia additionally with strong disto-median spur-like spine. Cerci prominent with numerous very long and strong setae.

DESCRIPTION

General

Body organised into head and trunk, the latter subdivided into thorax and abdomen ( Figs 1A, B ; 4A, C ; 5A, C ; 6A, C ), presumably with 20 segments, ocular segment plus 19 post-ocular segments.

Head

Ocular segment and post-ocular segments1-5forming distinct capsule (head capsule) ( Figs1A ; 4A ; 5A ; 6A ).Head capsule oval in dorsal(or ventral) view; about 1.6× wider than long. Surface of head capsule dorsallywithprominentY-shapedmoultingsuture(epicranialsuture) ( Fig. 5A ). Lateral edges of head capsule rounded with few setae.

Ocular segment recognisable by prominent compound eyes laterally projecting from the head capsule; additionally, three ocelli present [median eyes] ( Fig. 5B ). Compound eyes with numerous facets; difficult to count, at least 40 rows of facets ( Fig. 7A, B ). Ocelli arranged in a triangle; central ocellus dorsal to lateral ones. Appendage derivative of ocular segment (clypeo-labrum complex) [hypostome-labrum complex] well developed ( Fig. 7D ). Clypeus [hypostome] rectangular, about 2× wider than long. Labrum lobe-like, about as large as clypeus, anterior edge gently rounded.

Post-ocular segment 1 recognisable by its appendage, antenna [antennula]. Antenna arising from head capsule antero-dorsally; lateral to the clypeus; very long, longer than main body, with numerous elements (antennomeres), more than 40 ( Figs 1A, B ; 5A, C ); some elements are longer and possess a distinct constriction (indication of future subdivision?); length of elements strongly varying; proximal elements with few, but prominent setae. More distal elements with numerous, but shorter setae. Post-ocular segment 2 (intercalary segment) not recognisable externally.

Post-ocular segment 3 recognisable by its appendage, mandible ( Fig. 7 A-D). Mandibles prominent, curved, bearing teeth on inner surface.

Post-ocular segment 4 recognisable by its appendage, maxilla [maxillula] ( Fig. 7 A-F). Proximal part of maxilla (cardo) [basipod?] medially drawn out; cardo distally carrying palp [endopod]. Drawn out part (cardo? stipes? both?) prominent, sickle-shaped; laterally with at least three setae. Palp with five elements ( Figs 1C ; 6D ; 7F ). Element 1 (most proximal one) short, as long as wide (diameter). Element 2 sub-similar to element 1. Element 3 elongate, at least 4.5× longer than wide (diameter); with at least two strong spine-like setae and numerous smaller setae of varying sizes. Element 4 shorter than preceding element, elongate, at least 2.8× longer than wide (diameter); with at least two strong spine-like setae and numerous smaller setae of varying sizes. Element 5 (most distal one) elongate, about 4× longer than wide (diameter); with at least six strong spine-like setae and numerous smaller setae of varying sizes.

Post-ocular segment 5 recognisable by its appendage, labium [maxilla] ( Fig. 7E, F ); only distal parts, palp [endopod], apparent. Palp mostly concealed, with numerous setae.

Thorax [anterior trunk]

Post-ocular segments 6-8 differentiated from posterior ones, forming a distinct unit, thorax ( Fig. 5A ). Tergite of postocular segment 6 (tergite of thorax segment 1; pronotum) about 0.55× narrower than head; about 1.6× wider than long; rectangular-shaped in dorsal view; with six smaller setae medio-anteriorly. Post-ocular segment 6 (thorax segment 1; prothorax) ventrally with a pair of prominent appendages (foreleg) [thoracopod 1] ( Figs1D ; 2A ; 4B, D ; 5D ); basically cylindrical, composed of five elements.

Element 1 (coxa) [basipod?] about as long (proximal-distal axis) as wide (diameter); with at least three smaller, thin setae posteriorly. Element 2 (trochanter) [endopod element 1?] slightly longer than wide, slightly longer than coxa; with more than nine small, thin setae medially. Element 3 (femur) [endopod element 2?] very elongate; about 10× longer than coxa, similar width at proximal part, tapering towards distally to about 0.48× of maximum width; with more than ten small, thin setae proximo-medially and disto-laterally; also with more than ten strong spine-like setae arranged in two rows ( Fig. 4D ), the majority of which is located proximally, with one exception disto-laterally. Element 4 (tibia) [endopod element 3?] elongate, about 0.75× the length of the femur; about as wide as the femur, though slightly less proximally; covered with smaller setae, more distally than proximally; with three strong spine-like setae disto-medially of varying size and one strong spine-like seta laterally, more towards proximal than distal; with one very strong spine very medio-distally. Element 5 (tarsus) [endopod element 4?] slightly shorter than preceding element, more than 0.8× of the length and about half of the width; with numerous smaller, thin setae throughout its surface; distally with a pair of claws, possible attachment structure between claws not apparent; tarsus subdivided into three sub-elements (tarsomeres) which are of mostly similar length (0.3× of total length) and similar width, most proximal element has three stronger spine-like setae distally.

Post-ocular segment 7 (thorax segment 2; mesothorax) about half as long as prothorax and about as wide as the latter, but slightly tapering posteriorly; trapezoid-shaped; with one small seta on each side respectively (antero-laterally), close to the coxa. Ventrally with a pair of prominent appendages (mid leg) [thoracopod 2] ( Fig. 2B ); basically cylindrical, composed of five elements; as a whole slightly longer than foreleg [thoracopod 1].

Element 1 (coxa) [basipod?] about as long (proximal-distal axis) as wide (diameter); with two smaller setae medially. Element 2 (trochanter) [endopod element 1?] slightly longer than wide, but as wide as the coxa; with one small, thin seta and two stronger, spine-like setae medio-distally. Element 3 (femur) [endopod element 2?] very elongate; about 10× longer than coxa, almost similar width at proximal part, then widening to 1.5× width at about 30 % of total femur length, then tapering towards distally to about 0.67× of maximum width; with more than ten small, thin setae laterally throughout its surface; also with more than ten strong spine-like setae with varying sizes, the majority of which located medially, with one exception laterally. Element 4 (tibia) [endopod element 3?] elongate, slightly shorter than femur; about as wide as femur, though slightly less so proximally; covered with smaller setae, more distally than proximally; with two strong spine-like setae and more than five smaller spine-like setae disto-medially; also with one strong spine-like seta laterally, more towards proximal than distal, and one very strong spine very medio-distally. Element 5 (tarsus) [endopod element 4?] slightly shorter than tibia, more than 0.8× of the length and about half of the width; with numerous smaller, thin setae throughout; distally with a pair of claws, possible attachment structure between claws not apparent; tarsus subdivided into three sub-elements which are of mostly similar length (0.3× of total length) and similar width.

Post-ocular segment 8 (thorax segment 3; metathorax) about 1.4× longer than preceding segment and about as wide as that as well; rectangular shaped. Ventrally with a pair of prominent appendages (hind leg) [thoracopod 3] ( Figs 2C ; 3 ); basically cylindrical, composed of supposedly five elements; slightly longer than mid leg [thoracopod 2].

Element 1 (coxa) [basipod?] not differentiable from next element, i.e. element 2 (trochanter) [endopod element 1?]. Proximal region (coxa + trochanter?) slightly longer than wide. Element 3 (femur) [endopod element 2?] very elongate; about 8× longer than proximal region, similar width as preceding element, but tapering slightly distally; with four strong spine-like setae laterally. Element 4 (tibia) [endopod element 3?] elongate, but about 0.8× shorter than femur; about 0.67× the width of the femur, tapering slightly distally; covered with smaller setae and stronger spine-like setae; no very strong spine very medio-distally, but with one strong spine-like seta on a similar position as on the tibia of fore and mid legs, but shorter than in the latter. Element 5 (tarsus) [endopod element 4?] as long as tibia and slightly less wide than that as well; with numerous smaller, thin setae throughout; distally with a pair of claws, possible attachment structure between claws not apparent; tarsus subdivided into three sub-elements which are of similar width, but with varying length (from proximal to distal: 0.52×, 0.22× and 0.26× of total length).

Abdomen [posterior trunk]

Post-ocular segments 9-19 differentiated from further anterior ones, forming distinct unit (abdomen; not corresponding to abdomen in other crustacean groups) ( Figs 1A, B ; 5A, C ).

Only eight distinct units differentiable, first seven probably corresponding to abdominal segments 1 to 7, rectangularshaped. Last unit most likely corresponding to several abdomen segments (8-11?), triangular-shaped.

Post-ocular segment 9 (abdomen segment 1) about 1.4× longer than metathorax; but less wide, about 0.67× of metathorax width; one spine-like seta postero-laterally on each side.

Post-ocular segment 10 (abdomen segment 2) similar to preceding segment, but very slightly shorter and slightly wider posteriorly (widening posteriorly); one spine-like seta postero-laterally on each side.

Post-ocular segment 11 (abdomen segment 3) about half as long, but as wide as the preceding segment; one spine-like seta postero-laterally respectively.

Post-ocular segment 12 (abdomen segment 4) slightly longer and wider than preceding segment; two spine-like setae postero-laterally respectively, one slightly longer than the other.

Post-ocular segment 13 (abdomen segment 5) similar to preceding segment, but slightly longer and very slightly tapering posteriorly; two spine-like setae postero-laterally on each side, one slightly longer than the other.

Post-ocular segment 14 (abdomen segment 6) slightly shorter and less wide than preceding segment, tapering slightly posteriorly; one spine-like seta postero-laterally on each side.

Post-ocular segment 15 (abdomen segment 7) similar to preceding segment, but less wide and tapering posteriorly; one spine-like seta postero-laterally on each side.

Trunk end (post-ocular segments 16-19?; abdomen segments 8-11?) as long as first abdomen segment; anteriorly as wide as preceding segment, but tapering drastically posteriorly. Ventrally with a pair of prominent appendages (cerci) ( Figs 1A, B ; 3 ; 5A, C ; 6B ); basically cylindrical, not subdivided; about 0.8× the length of the antenna; as wide as the tibia of the hind leg proximally and tapering slightly until about 70 % of its length, then strongly tapering towards tip; bearing numerous spine-like setae of varying sizes, mostly strong and very long (compared to similar structures elsewhere); also with a few smaller, shorter setae throughout.

Size of specimens

While the specimens are very similar in overall appearance, they differ in size. Though it remains difficult to measure, it appears that the four specimens fall into three size classes ( Fig. 8 ). It seems likely that these represent three successive stages. It remains unclear whether the largest size class corresponds to the adult stage.

Figures

FIG. 1. — Holotype of Gryllobencain patrickmuelleri n. gen., n. sp.,PED 0147:A, overview in dorsal view; B, overview in ventral view; C, close-up on maxillary palp, distal part; D, close-up on thorax appendage 1. Abbreviations: an, antenna; ce, cercus; cl1, claw of thorax appendage 1; f1-2, femur of thorax appendage 1-2; hc, head capsule; mp, maxillary palp; sp, spine-like seta; t1-3, thorax segment 1-3; ta1-3, tarsus of thorax appendage 1-3; tcl, tibia claw; ti1-3, tibia of thorax appendage 1-3. Scale bars: A, B, 1 mm; C, 0.25 mm; D, 0.5 mm.

FIG. 4. — Paratype of Gryllobencain patrickmuelleri n. gen., n. sp., PED 0178:A, overview in dorso-lateral view; B, detail of thorax appendage 1 in posterior view; C, overview in ventro-lateral view; D, detail of thorax appendage 1 in anterior view. Abbreviations: an, antenna; c1, coxa of thorax appendage 1; ce, cercus; ey, compound eye; f1-3, femur of thorax appendage 1-3; hc, head capsule; mp, maxillary palp; sp, spine-like seta; ta1, 3, tarsus of thorax appendage 1, 3; tcl, tibia claw; ti1-3, tibia of thorax appendage 1-3; tr1, trochanter of thorax appendage 1. Scale bars: A, C, 1 mm; B, D, 0.5 mm.

FIG. 5. — Gryllobencain patrickmuelleri n. gen., n. sp., BUB 3073: A, overview in dorsal view; B, close-up in anterior head area with ocelli; C, overview in ventral view; D, close-up on distal part of thorax appendage 1. In A and C background was desaturated to enhance contrast. Abbreviations: an, antenna; ce, cercus; cl, claw of thorax appendage; f1-3, femur of thorax appendage 1-3; mp, maxillary palp; oc, ocelli; ta1, tarsus of thorax appendage 1; ti1-3, tibia of thorax appendage 1-3. Scale bars: A, C, 0.5 mm; B, D, 0.1 mm.

FIG. 6. — Gryllobencain patrickmuelleri n. gen., n. sp., BUB 3072: A, overview in dorsal view; B, close-up on cercus; C, overview in ventral view; D, close-up on head. Abbreviations: an, antenna; ce, cercus; f1, 3, femur of thorax appendage 1, 3; hc, head capsule; mp, maxillary palp; ti1, 3, tibia of thorax appendage 1, 3. Scale bars: A, C, 1 mm; B, D, 0.5 mm.

FIG. 7. — Close-ups on head area in different specimens of Gryllobencain patrickmuelleri n. gen., n. sp. as normal versions (A, C, E) and colour-marked (B, D, F): A-D, PED 0178; A, B, latero-posterior view; C, D, mostly anterior view; elements of maxillary palp difficult to differentiate; E, F, BUB 3073, ventral view. Abbreviations: lp, labial palp; lr, labrum; md, mandible; mmx, median part of maxilla; mp, maxillary palp; mx, maxilla; pmx, proximal part of maxilla. Scale bars: A-D, 0.3 mm; E, F, 0.2 mm.

FIG. 2. — Holotype of Gryllobencain patrickmuelleri n. gen., n. sp., PED 0147, close-up on thorax appendages: A, thorax appendage 1; B, thorax appendage 2; C, thorax appendage 3. Abbreviations: c2, coxa of thorax appendage 2; ce, cercus; cl, claw of thorax appendage; f1-3, femur of thorax appendage 1-3; ta1-3, tarsus of thorax appendage 1-3; tcl, tibia claw; ti1-3, tibia of thorax appendage 1-3. Scale bars: 0.5 mm.

FIG. 3. — Holotype of Gryllobencain patrickmuelleri n. gen., n. sp., PED 0147, close-up on posterior end with thorax appendage 3 and cerci. Abbreviations: ce, cercus; ta3, tarsus of thorax appendage 3; ti3, tibia of thorax appendage 3. Scale bar: 0.5 mm.

FIG. 8. — Reconstructed growth series of Gryllobencain patrickmuelleri n. gen., n. sp. based on specimens investigated in this study: A, BUB 3073; B, PED 0147; C, PED 0178 + BUB 3072. Scale bar: 1 mm.