Austroplebeia (Anteplebeina), Engel & Herhold & Davis & Wang & Thomas, 2021

Engel, Michael S., Herhold, Hollister W., Davis, Steven R., Wang, Bo & Thomas, Jennifer C., 2021, Stingless bees in Miocene amber of southeastern China (Hymenoptera: Apidae), Journal of Melittology 2021 (105), pp. 1-83 : 35-40

Anteplebeina Engel , new subgenus

ZooBank: urn:lsid:zoobank.org:act:C096F1FD-68A8-45F6-8518-41BD855A88A4

TYPE SPECIES: Austroplebeia (Anteplebeina) fujianica Engel, new species .

DIAGNOSIS: The new subgenus can be most easily distinguished from Austroplebeia s.str. in the more developed malar space ( Fig. 54 ), with a length approximately that of the flagellar diameter (or approximately 0.75–0.80× the basal mandibular width) (versus 0.4–0.5× the flagellar diameter or 0.2–0.3× the basal mandibular width in Austroplebeia s.str.). Additionally, 1M is confluent with 1cu-a rather than the slightly distad position in Austroplebeia s.str., and M is straight but extends slightly beyond 1m-cu as a tubular vein and therefore the proximal half of 3M is tubular, versus M straight and terminating at or slightly before 1m-cu as a tubular vein (i.e., 2M tubular but 3M wholly nebulous) ( Fig. 62 ). Lastly, while 2Rs and 1rs-m are not evident in Austroplebeia s.str., these veins are weakly nebulous in Anteplebeina .

DESCRIPTION: Workers small, total length ca. 4.4 mm, forewing length ca. 3.6 mm; integument faintly tessellate, some places with widely-scatered minute punctures on head and mesosoma, with distinct pale yellow maculation on face ( Fig. 54 ), particularly below tangent of antennal toruli, mesoscutum, mesoscutellum, and metepisternum ( Figs. 50 , 52, 53 , 55 , 61 ). Setae on body mostly fine, short, and simple; mesoscutum with abundant erect, fine, short, simple setae; disc of mesoscutellum with similar setae to those of mesoscutum except nearly twice as long, particularly along posterior margin; setation pale to white.

Head as broad as mesosoma, broader than long, with face broader than compound eye length; vertex gently rounded, not produced or ridged; preoccipital area round- ed; ocelloccipital distance slightly more than one ocellar diameter; interocellar distance about 3× median ocellar diameter, greater than ocellocular distance (interocellar distance 1.3× ocellocular distance); ocellocular distance about 2.25× ocellar diameter; scape shorter than antennal-ocellar distance, not reaching median ocellus; ocelli near top of vertex; flagellomeres about as long as or slightly longer than wide; flagellomere I trapezoidal, shorter than flagellomere II; flagellomere II about as long as flagellomere III ( Fig. 54 ); intertorular distance slightly shorter than torulocular distance; upper torular tangent slightly below facial midlength ( Fig. 54 ); gena rounded, slightly narrower than compound eye in profile; supraäntennal area with triangular medial elevation; frontal carina absent; malar area produced, moderate length, as long as flagellar diameter ( Fig. 54 ); labrum transverse, simple, apical margin rounded; mandible bidentate, teeth well defined, acute, and incised, interdental spaces distinct but not broadly incised, instead narrowly V-shaped, first preapical tooth (P 1) distinctly forward of P 2; labial palpomeres I and II with a few, scatered, long (slightly to much longer than width of palpomeres), straight to slightly wavy setae.

Mesoscutum with median sulcus faintly impressed, extending to slightly beyond mesoscutal midlength; notauli scarcely evident, not impressed; mesoscutellum short, acutely rounded in lateral aspect ( Figs. 44 , 51–53 ), slightly overhanging metanotum in dorsal view, shining transverse depression on mesoscuto-mesoscutellar sulcus simple; propodeum gently sloping; basal area slightly longer than mesoscutellum, glabrous, shining, faintly reticulate ( Figs. 52, 53 ); propodeal spiracle elongate.

Forewing extending beyond apex of metasoma, with 2Rs, 1rs-m, 1m-cu, apical half 3M, 4M, apical half 1Cu, 2Cu, 3Cu, and 2cu-a indicated by brownish or pale nebulous traces and fenestrae demarcated by faint white spectral lines on wing membrane; membrane with light brown microtrichia; prestigma short, scarcely longer than anterior width of 1Rs; pterostigma slender; marginal cell slightly more than 4× as long as maximum breadth, separated from wing apex by slightly more than its maximum width, apex narrowly open, opening about one-quarter maximum marginal cell width, 4Rs with nebulous, angled apex (i.e., appendiculate), without nebulous stub of 2r-rs ( Fig. 62 ); 1M confluent with 1cu-a ( Fig. 62 ); submarginal angle nearly orthogonal; M straight, not angled at 1m-cu (i.e., angle between 2M and 3M linear or at most faintly less than 180°); 3M tubular in basal half, then nebulous; 2Rs straight; 1rs-m straight; r-rs slightly longer than 3Rs; 1m-cu short, only weakly bent apically near M. Hind wing with 5 distal hamuli; radial and cubital cells closed by nebulous veins.

Metatibia approximately triangular ( Figs. 56, 57 , 59 ), approximately 2.4× as long as greatest width; retromargin gently curved with subangulate distal superior angle ( Figs. 56, 57 ), retromarginal setae and superior prolateral surface simple ( Figs. 59, 60 ); prolateral surface shallowly concave apically, with corbicula occupying slightly less than apical half; retrolateral surface with broad weakly elevated keirotrichiate zone and narrow superior subglabrous zone ( Figs. 57 , 59, 60 ), with shallowly sloping clivulus ( Fig. 58 ); keirotrichiate zone 2.5–3× as broad as superior glabrate zone ( Figs. 59, 60 ), keirotrichiate zone extending to apical margin ( Fig. 59 ), with keirotrichiate zone narrowing and superior glabrate zone broadening in apicalmost portion of metatibia; penicillum and rastellar comb present, each composed of fine stiff setae. Metabasitarsus with proventral margin straight, retrodorsal margin gently sloping posteriorly to about midlength, then paralleling proventral margin to apex ( Fig. 60 ), proventral margin comparatively straight, distal superior angle not projecting; retrolateral surface without basal sericeous area ( Figs. 59, 60 ).

Metasoma broad, almost as wide as mesosoma, with first metasomal tergum smooth and shining, laterally finely and faintly tessellate, remaining terga finely and faintly tessellate, all terga impunctate, terga with sparse, short to minute, erect, simple setae intermingled with exceedingly sparse appressed to subappressed, minute, simple setae; tergum VI with sparse erect setae distinctly longer, up to twice length of erect setae on preceding terga; sterna finely imbricate, with numerous elongate, fine, erect, simple setae and intermingled with more scatered, short, erect, simple setae.

ETYMOLOGY: The new subgeneric name is a combination of the Latin words ante (“before”), plēbēia (“plebeian”, “commoner”, “plebe”), and the feminine diminutive suffix – īna (“wife of,” feminine suffix with diminutive implication). The gender of the name is considered feminine.

COMMENTS: It is interesting to note that Anteplebeina has 5 distal hamuli, the putatively plesiomorphic condition for the clade containing Austroplebeia s.l. and relat- ed genera (i.e., Hypotrigona , Liotrigona , Lisotrigona , Pariotrigona ), and relative to the condition of 6 distal hamuli in Austroplebeia s.str. Based on current understanding, Lisotrigona is the extant sister group to Austroplebeia s.l. ( Rasmussen & Cameron, 2010), although Pariotrigona was not included in the analysis and certainly belongs to the broader clade containing these genera. If Pariotrigona is more closely related to Austroplebeia than Lisotrigona , then the elongate malar space of the former and Anteplebeina could be a shared plesiomorphy of the combined clade, with a reversal to shorter malar spaces in Austroplebeia s.str. Alternatively, both Hypotrigona and Pariotrigona have largely tuberculiform worker gonostyli that, because of their reduction, lack gonotrichia and this could be a shared reduction or plesiomorphic for the clade, in which case Lisotrigona would be more closely related to Austroplebeia s.l., and the malar spaces would be independently derived. Regardless, the biogeographic implications (vide Discussion, infra) would not change except in relation to the stem lineage of Pariotrigona .

Figures

Figures 54–58. Worker (holotype, NIGP 176057) of Austroplebeia (Anteplebeina) fujianica, new species, µCT scans (yellow highlights indicate areas of yellow maculation; green indicates area of keirotrichiate zone). 54. Facial view (note malar space in relation to diameter of flagellomeres II + III). 55. Dorsal habitus. 56. Prolateral view of metatibia and metatarsus. 57. Retrolateral view of metatibia and metatarsus. 58. Cross-section of metatibia showing gently sloping clivulus.

Figures 59–62. Details of workers of Austroplebeia (Anteplebeina) fujianica, new species. 59. Ret- rolateral view of metatibia and metatarsus of SEMC F002513. 60. Retrolateral view of metatibia and metatarsus of NIGP 176057. 61. Left view of head and mesoscutal dorsum of NIGP 176057. 62. Forewing of NIGP 176057.

Figures 50–51. Workers of Austroplebeia (Anteplebeina) fujianica, new species. 50. Facial view of holotype (NIGP 176057). 51. Right lateral habitus of SEMC F002513.

Figures 52–53. Mesosomal details of workers of Austroplebeia (Anteplebeina) fujianica, new species (note also finely polished reticulate propodeal sculpturing in both specimens). 52. Posterior-dorsal-oblique view of NIGP 176057 (holotype). 53. Posterior-dorsal-oblique view of SEMC F002513.

Figures 43–44. Lateral habitus µCT scans of workers of Zhangpu stingless bees. 43. Tetragonula (Tetragonula) florilega, new species (NIGP 176093). 44. Austroplebeia (Anteplebeina) fujianica, new subgenus and species (holotype, NIGP 176057). Note differences in malar spaces, metatibiae, and mesoscutella + propodea.