Type species.

Taxon classification

Animalia

Ephemeroptera

Vietnamellidae

Godunko

Roman J.

Martynov

Alexander V.

Staniczek

Arnold H.

First fossil record of the mayfly family

Vietnamellidae

(

Insecta

Ephemeroptera

) from Burmese Amber confirms its Oriental origin and gives new insights into its evolution

Zookeys1052021103699120

10.3897/zookeys.1036.66435

Genus

3526B888-D327-5CC2-B5D1-DB7E34C24AB3

Burmella

http://zoobank.org/0A29850B-F977-47E1-948E-37B5C617BD95

gen. nov.

Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, Table 1

Type species.

Burmella paucivenosa sp. nov.

Derivation of name.

The generic name of female gender is a composition of “Burmar” as an ancient term for Myanmar, combined with “ella”, a common ending of generic names in mayflies, and especially so within Ephemerelloidea.

Diagnosis.

Adults of Burmella gen. nov. differ from other mayfly genera by the following combination of features: forewings (a) with small number of cross veins; (b) pterostigma with simple veins, not anastomosed; (c) CuP smoothly curved towards wing base; (d) two secondary bifurcate veins in cubital field; (e) at least several free marginal intercalaries along ventral margin; hind wings (f) strongly rounded, small, as long as 0.08–0.14 of forewing length; (g) small number of cross veins; (h) triad RS present or absent; no MA and MP triads; (i) no secondary branches of cubital veins; (j) costal process developed, rounded apically, situated centrally; abdomen (k) with vestigial gill sockets recognizable at least on segments II–VI; genitalia (l) with large median projection of styliger plate, widely rounded apically; (m) three distal segments of forceps strongly elongated and slender; segment II longest, 5× as long as segment III; segments III and IV approximately of equal length; segment IV expanding apically; (n) penis lobes widely separated by V-shaped cleft; (o) no trace of paracercus. Additionally, in female (p) anterior part of eyes covered by anterolaterally expanded clypeal shield.

Subimago and larva unknown.

Species composition.

Burmella paucivenosa sp. nov. (SMNS; BU-179); Burmella clypeata sp. nov. (SMNS; BU-321).

Locality and horizon.

Hukawng Valley, Kachin State, Myanmar (Burma); Cenomanian, mid-Cretaceous.

Table 1.

Measurements of fossil representatives of the genus Burmella gen. nov.

Adult characters	Burmella paucivenosa sp. nov. [SMNS, BU-179, male imago] (mm)	Burmella clypeata sp. nov. [SMNS, BU-321, female imago] (mm)
Length of body	5.75	7.00
Length of right foreleg	2.51*	1.14*
Length of femur	0.83	0.42
Length of tibia	1.68	0.72*
Length of tarsus	–	–
Segment I	–	–
Segment II	–	–
Segment III	–	–
Segment IV	–	–
Segment V	–	–
Length of left foreleg	2.52*	1.64*
Length of femur	0.85	0.46
Length of tibia	1.67	1.18*
Length of tarsus	–	–
Segment I	–	–
Segment II	–	–
Segment III	–	–
Segment IV	–	–
Segment V	–	–
Length of right middle leg	2.78	–
Length of femur	1.45	–
Length of tibia	1.03	–
Length of tarsus	0.30	–
Segment I	0.08	–
Segment II	0.10	–
Segment III	0.10	–
Segment IV	0.11	–
Segment V	0.14	–
Length of left middle leg	2.70*	2.36
Length of femur	1.20	0.60
Length of tibia	1.02	1.34
Length of tarsus	0.48*	0.42
Segment I	–	0.08
Segment II	–	0.07
Segment III	–	0.07
Segment IV	–	0.08
Segment V	–	0.12
Length of right hind leg	2.47	1.71
Length of femur	1.02	0.71
Length of tibia	0.93	0.56
Length of tarsus	0.52	0.44
Segment I	0.07	0.09
Segment II	0.09	0.08
Segment III	0.10	0.07
Segment IV	0.12	0.08
Segment V	0.14	0.12
Length of left hind leg	2.07	2.60
Length of femur	1.00	0.98
Length of tibia	0.66	1.06
Length of tarsus	0.41	0.56
Segment I	0.05	0.11
Segment II	0.07	0.11
Segment III	0.07	0.10
Segment IV	0.10	0.10
Segment V	0.11	0.14
Length of right forewing	4.64	1.80
Length of left forewing	4.68	5.12
Length of right hind wing	0.66	0.45
Length of left hind wing	0.64	–
Hind/Fore wings length ratio	0.14	0.08
Length of cerci [right/left]	2.35/1.24	8.12/–

* preserved part.

10.3897/zookeys.1036.66435.figure1

1C5F3530-58D4-5F8E-B7E1-C9EFE0AEEC4D

Figure 1.

Burmella paucivenosa sp. nov., male imago, holotype, general lateral view A left side of body B right side of body. Scale bars: 2 mm.

https://binary.pensoft.net/fig/541121

10.3897/zookeys.1036.66435.figure2

EA07275E-684B-594E-887A-A0A1207A2595

Figure 2.

Burmella paucivenosa sp. nov., male imago, holotype A head, right lateral view B compound eye, left lateral view C head and thorax, left lateral view D mesothorax, left lateral view. Blue line – border between portions of compound eye, da – damaged area, lp – lower portion, LPs and red line – lateroparapsidal suture, MNs and green line – mesonotal suture, MPs and yellow line – medioparapsidal suture, up – upper portion. Scale bars: 0.5 mm (A, C); 0.2 mm (B, D).

https://binary.pensoft.net/fig/541122

10.3897/zookeys.1036.66435.figure3

71379CE7-C79D-5638-B994-3D1D45093854

Figure 3.

Burmella paucivenosa sp. nov., male imago, holotype A, B tarsus of right middle leg C right middle leg D left hind leg. I–V – tarsal segments, pts – patellotibial suture. Scale bars: 0.1 mm (A, B); 0.5 mm (C); 0.2 mm (D).

https://binary.pensoft.net/fig/541123

10.3897/zookeys.1036.66435.figure4

F4A6A03D-60F4-58F1-9938-0BE1870F9EBE

Figure 4.

Burmella paucivenosa sp. nov., male imago, holotype A right and left wings position in amber B right forewing venation and size ratio of fore and hind wings. Scale bars: 1 mm.

https://binary.pensoft.net/fig/541124

10.3897/zookeys.1036.66435.figure5

4AF78616-B8E4-5E1D-BF82-5CB445A74AA5

Figure 5.

Burmella paucivenosa sp. nov., male imago, holotype A right hind wing in amber B right hind wing venation. Scale bars: 0.2 mm.

https://binary.pensoft.net/fig/541125

10.3897/zookeys.1036.66435.figure6

A7E1EAF5-1FE3-5244-A217-77D221857963

Figure 6.

Burmella paucivenosa sp. nov., male imago, holotype A abdomen, left lateral view B abdominal segments III–VII, lateral view C, D genitalia, ventrolateral view. III–VII – numbers of segments, white arrows mark remnants of gill sockets, pink area – penis lobes, light blue area – gonobasis (styliger plate), brown area styliger segment I, yellow area –styliger segment II, light green area – styliger segment III, purple area – styliger segment IV. Scale bars: 1 mm (A); 0.5 mm (B); 0.2 mm (C, D).

https://binary.pensoft.net/fig/541126

10.3897/zookeys.1036.66435.figure7

00B321D7-F655-5E73-9A53-530C36ED1810

Figure 7.

Burmella clypeata sp. nov., female imago, holotype A general dorsal view B general ventral view C, D head, dorsal view E head and thorax, dorsal view. BA – basal sclerite (basalare), LPs and red line – lateroparapsidal suture, MNs and green line – mesonotal suture, MPs and yellow line – medioparapsidal suture, rc – right cercus. Scale bars: 2 mm (A, B); 0.2 mm (C, D); 0.5 mm (E).

https://binary.pensoft.net/fig/541127

10.3897/zookeys.1036.66435.figure8

B2FE7F2D-BB45-505C-8642-FD460F877FCA

Figure 8.

Burmella clypeata sp. nov., female imago, holotype A tarsus of left hind leg B tarsus of right hind leg C left forewing in amber D left forewing venation and size ratio of left fore- and right hind wings E distal part of left forewing F preserved basal part of right forewing. I–V – tarsal segments, ci – basally connected intercalary vein, fi – basally free intercalary vein. Scale bars: 0.1 mm (A, B); 1 mm (C, D); 0.5 mm (E, F).

https://binary.pensoft.net/fig/541128

10.3897/zookeys.1036.66435.figure9

7ED58F7C-3E2C-5925-B8CA-9BDAA1E6029F

Figure 9.

Burmella clypeata sp. nov., female imago, holotype A right hind wing, dorsal view B right hind wing, ventral view C right hind wing venation. Scale bars: 0.2 mm (A, B); 0.5 mm (C).

https://binary.pensoft.net/fig/541129

10.3897/zookeys.1036.66435.figure10

91E1F439-7424-5251-8FB3-EBA045A1BE80

Figure 10.

Burmella clypeata sp. nov., female imago, holotype A body, ventral view B, C apical part of abdomen, ventral view D basal segments of abdomen, dorsal view. I–III and V–IX – numbers of abdominal segments, gsr – remnant of gill socket, pp – paraproct plate. Scale bars: 1 mm (A); 0.5 mm (B–D).

https://binary.pensoft.net/fig/541130