A new species of Polydesmidae (Myriapoda, Diplopoda, Polydesmida) from the mid-Cretaceous Burmese amber Author Su, Yi-Tong Author Cai, Chen-Yang Author Huang, Di-Ying text Zootaxa 2023 2023-12-29 5396 1 112 123 https://www.mapress.com/zt/article/download/zootaxa.5396.1.16/52609 journal article 10.11646/zootaxa.5396.1.16 1175-5326 10441247 A614B0EF-D584-4055-B119-978CFAD08024 Propolydesmus cretaceus sp. nov. Material. Holotype : NIGP175097 , a well-preserved adult male ( Figs 1–3 ) . Paratypes : NIGP175098 – NIGP175103 , one well-preserved adult male ( Figs 4–5 ), one well-preserved adult female ( Figs 6–7 ), one moderately preserved adult females, two moderately preserved sub-adult females. Additionally, 14 female or sex-undetermined specimens are studied. Etymology. Name after the age of the fossils, as the species is the first formally described Polydesmidae from the Cretaceous. FIGURE 1. Adult male of Propolydesmus cretaceus sp. nov. , holotype (NIGP175097). A , Dorsal overall view. B , Ventral overall view. C , Dorsal view of body rings 12–16. D , Ventral view of head. E , Ventral view of gonopods. F , 3D reconstruction of anterior body part, ventral view. G , 3D reconstruction of of head, collum and metatergite 2, dorsal view. Abbreviations: go, gonopods. Scale bars: 1 mm in A , B ; 0.5 mm in C , D , F , G ; 0.2 mm in E . FIGURE 2. Adult male of Propolydesmus cretaceus , holotype (NIGP175097), detail structures under CLSM. A , Ventral view of head. B , Polygonal texture on metatergite surface. C , Detail structures of the right antenna. D , Detail structures of the 13 th , 14 th body-rings. E , Detail structures of gonopods, ventrolateral view. F , Dorsal view of body rings 17–19 and telson. Abbreviations: a, acropodite; ex1, main branch of exomerite; ex2, twisted bipartite branch of exomerite; f, femoral part of telopodite; pf, prefermoral part of telopodite; s, sulcus between femoral part and exomerite. Scale bars: 200 μm in A , D , F ; 100 μm in others. FIGURE 3. Adult male of Propolydesmus cretaceus , holotype (NIGP175097), gonopod structures using µCT reconstruction. A , Ventrolateral overall view. B , Lateral overall view. C , Right gonopod, mesal view. D , Left gonopod, mesal view. E , Femoral part, acropodite and exomerite of right gonopod. F , Femoral part, acropodite and exomerite of right gonopod. Abbreviations: a, acropodite; ca, cannula; ex, exomerite; ex1, main branch of exomerite; ex2, twisted bipartite branch of exomerite; f, femoral part of telopodite; gx, gonocoxa; or?, questionable orifice; pf, prefermoral part of telopodite; sg?, questionable seminal groove. Scale bars: 200 μm in A , D , F ; 100 μm in others. FIGURE 4. Adult male of Propolydesmus cretaceus , paratype (NIGP175098), overall structures under bright field. A , B , Lateral overall view. C , D , Lateral view of head. E , F , Lateral view of telson. Scale bars: 1 mm in A , B ; 0.2 mm in others. Diagnosis. Differs from other Propolydesmus species by: prefemoral part of gonopod telopodite large, slightly elongate; acropodite strongly developed and falcate; exomerite relatively short, smooth, with a twisted bipartite branch. FIGURE 5. Adult male of Propolydesmus cretaceus , paratype (NIGP175098), detail structures under CLSM and µCT. A , B , Lateral view of head. C , Lateral view of body rings 5–7. D , Lateral view of telson. E , 3D reconstruction of anterior body part, ventral view. F , 3D reconstruction of anterior body part, dorsal view. Scale bars: 0.5 mm in E ; 0.2 mm in A , B , D , F ; 0.1 mm in C . FIGURE 6. Adult female of Propolydesmus cretaceus , paratype (NIGP175099), overall structures under bright field. A , Dorsal overall view. B , Ventral overall view. C , Dorsal view of body rings 8–11. D , Dorsal view of head, collum and metaterga 2–5. E , Ventral view of head, body rings 2–5. F , Dorsal view of body rings 16–19 and telson. G , Ventral view of body rings 16–19 and telson. Scale bars: 1 mm in A , B ; 0.5 mm in D , E , F ; 0.2 mm in others. Locality and horizon. Noije Bum near Tanai, Hukawng Valley, Kachin State of northern Myanmar ; upper Albian to lower Cenomanian (mid-Cretaceous). FIGURE 7. Adult female of Propolydesmus cretaceus , paratype (NIGP175099), detail structures under CLSM. A , Ventral view of head. B , Detail features of terga 9–11. C , surface structures on terga 10–11. D , Detail structures of ozopore. E , Dorsal view of body rings 16–19 and telson. F , Ventral view of telson. Scale bars: 200 μm in A , B , D , F ; 100 μm in C , 50 μm in D . Description. Body length 6.0– 7.8 mm , maximum width of mid-body metazonites 0.9–1.1 mm , 20 body rings in adult (18+1+T). No distinct body size difference between male and female ( Figs 1A, B , 4A, B , 6A, B ). Head moderately to densely setose, fron wide and flatten ( Figs 1D , 2A , 4C, D , 5A, B , 6 D, E , 7A ). Ommatidia absent. Antennae slender and slightly clavate, moderately to densely setose, in situ reaching the posterior part of metatergite 3 if stretched dorsally; length of antennomeres 2≈3>6≈5≈4>1>7, antennomere 5, 6 wider than others ( Figs 1D , 2A, C , 4C, D , 5B , 6 D, E , 7A ); antennomeres 5 and 6 each with a distodorsal group of bacilliform sensilla, numbers and details of the sensilla unclear. Gnathochilarium of typical polydesmid form, detailed structures not acquirable. Collum small, slightly convex, suboval shaped, narrower than head and following metaterga, without obvious sculpture; with 3 rows of elongate acicular seta: 5+5 along anterior margin, 3+3 on medial area, 3+3 along posterior margin; lateral corners weakly angular, each side with one laterally pointed setae ( Figs 1G , 5F ). Body parallelsided from ring 3 to 14. Metaterga broad, with shallow polygonal texture ( Figs 2B , 7C, D ); metatergal sculpture typical and moderately developed: setiferous polygonal bosses arranged in 3 transverse rows, with 3+3 on each row; metatergal seta elongate and acicular, similar to seta on collum ( Figs 2D , 5F , 7B ). Paraterga well-developed, slightly wing-shaped, with 3 (metaterga without ozopore) or 4 (with ozopore) setiferous notches ( Fig. 7B ). Ozopores located much closer to lateral than to caudal margin of paraterga, pore formula normal. Pleurites and sterna with dense small projections ( Fig. 5C ). Legs elongate, moderately setose; tarsus long and slender, sphaerotrichomes absent or not visible; claw simple, slightly curved. Epiproct short, conical, directed caudoventrally, with a group of 4 setiform spinnerets on tip; paraprocts suboval and slightly elongate ( Figs 2F , 4E, F , 5D , 6F, G , 7E ); hypoproct large, subtrapeziform to sub-oval, caudal 1+1 setiferous papillae well-developed and moderately separated ( Fig. 7F ). Gonopods modified from leg pair 7 only ( Figs 1F , 5E ). Coxae of typical polydesmoid form: large, medial fused, deeply excavated ( Fig. 3A, B ). Telopodites well exposed, suberect; prefemoral part large, moderately in length, sparsely to moderately setose ( Fig. 2E ); femoral part short, stout, depressed along main body axis on distal part ( Figs 2E , 3C, D ); acropodite strongly developed, falcate in shape ( Fig. 3E, F ); exomerite relatively short, smooth, subfalcate, set off from femorite by a sulcus and bend dorsal-caudally, with a twisted bipartite branch on basalmedial part, without other seta, spines or projections ( Figs 2E , 3C–F ). The groove or strip on inner side of telopodite might refer to seminal groove ( Fig. 3C, D ), however its accurate features are not available, the opening near the base of acropodite ( Fig. 3E, F ) might be orifice of seminal groove or accessory seminal chamber.