Research Article |
Corresponding author: Zhipeng Zhao ( zhaozhipeng@cafs.ac.cn ) Academic editor: Eliana Cancello
© 2024 Yurong Jiang, Xinru Deng, Chungkun Shih, Yunyun Zhao, Dong Ren, Zhipeng Zhao.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Jiang Y, Deng X, Shih C, Zhao Y, Ren D, Zhao Z (2024) Primitive new termites (Blattodea, Termitoidae) in Cretaceous amber from Myanmar. ZooKeys 1197: 115-126. https://doi.org/10.3897/zookeys.1197.114452
|
Mastotermitidae, the first-diverging extant family of termites, has only one relic extant species; however, this family had greater richness during the Mesozoic and Cenozoic eras. Fossil termites from the Cretaceous provide information on the early evolution of termites and the transition between extinct families. Herein, two new Mastotermitidae species found in upper Cretaceous (Cenomanian) Kachin amber are reported. One is a female imago described as Angustitermes reflexus gen. et sp. nov. and assigned to the subfamily Mastotermitinae. The other is Mastotermes reticulatus sp. nov., which is described from an isolated forewing. With the comparison especially of the antenna and venation, these new mastotermitids further increase our knowledge of the diversity and morphology of Mastotermitidae during the Mesozoic.
Fossil termites, Isoptera, Mastotermitidae, social insects, taxonomy
Termites are social insects with the support of mutualistic protists or cellulose-digesting bacteria (
As the first-diverging extant family in Termitoidae (
Besides the sole relic species, Mastotermes darwiniensis Froggatt, 1897, living in northern Australia and southern New Guinea (
The two specimens studied here were collected from amber mines located in the Hukawng Valley in Kachin State of northern Myanmar. Determined by U-Pb dating of Zircon, the deposit age of the amber mine was 98.79 ± 0.62 Ma which means it comes from early Cenomanian of the upper Cretaceous (
The amber is cut and polished. The specimens are examined, measured, and photographed with a Nikon SMZ25 microscope system. To help reduce picture distortion caused by refraction and internal cracks, the amber was placed in a properly sized crystallizing dish, with a proper amount of water, and the capture angle and area of interest was adjusted when viewing; the amber was affixed with plasticine when measurements and photographs were taken.
All images are stacked using the software Helicon Focus v. 8 for better depth of field. Simplified drawings were prepared using Adobe Illustrator CC and further modified using Adobe Photoshop CC.
Subfamily Mastotermitinae Engel, 2021
Angustitermes reflexus Jiang, Z. Zhao & Ren, gen. et sp. nov. (Figs
Angusti- is a Latin adjective, reflecting the fact that the medial field of this genus is narrow, and termes is the usual noun for the generic name in Termitoidae. The gender is masculine.
Imago: ocelli oval; fontanelle absent; Y-suture absent; mandibles not exceeding labrum; antenna moniliform with 22 articles; compound eyes lying in middle position on head; pronotum saddle-shaped. Wings heavily reticulated, with “cross-veins” present. Forewing: scale large, overlapping hind wing base, humeral suture convex; all major veins origin in scale; veins Sc, R1, R2, Rs, and M more pigmented than CuA; Sc simple; Rs with about three main branches, terminating on costal margin anterior to wing apex; radial field narrow, parallel to costal margin; M closer to Rs than CuA, lying more or less parallel to Rs as a simple vein for the greater part of its length, first branching in apical 1/5 of wing length, medial field narrow, encompassing wing apex; CuA branched, lying above the mid-longitudinal line of wing; CuP (claval suture) arched, meeting basal suture before posterior margin. Hind wing: basal suture not visible, large anal lobe present. Legs: tibial spines of all legs present; tibial spur formula 3–4–4; tarsi pentamerous; arolium present. Abdomen: cerci short, trimerous; abdominal styli absent.
Based on the sclerotized vein M, presence of the anal lobe, saddle-shaped pronotum, pentamerous tarsi, etc., Angustitermes gen. nov. is considered to belong to the Mastotermitidae and is assigned to the subfamily Mastotermitinae because of the ocelli (Fig.
Photographs and drawing of Angustitermes reflexus gen. et sp. nov., holotype specimen CNU-TER-BU-2017005 (female imago) A habitus (dorsal view) B drawing of habitus (dorsal view) C head in dorsal view D head in ventral view E cerci in dorsal view. Scale bars: 4.0 mm (A, B); 1.0 mm (C); 0.5 mm (D); 0.2 mm (E).
The major feature of Angustitermes gen. nov. is that the M vein is a simple vein for the greater part of its length, first branch branching in the apical 1/5 of wing length, and the medial field is narrow (Fig.
Holotype. Myanmar • Imago♀; Kachin State, Hukawng Valley; one imago (abdomen fragmentary); Kachin amber; CNU-TER-BU-2017005 (Figs
The specific name, reflexus, means “fold”, which is in reference to the fact that the right forewing and right hindwing of the holotype are folded. The gender is masculine to match gender of the genus.
The specimen was collected from the upper Cretaceous (Cenomanian) deposits of the Hukawng Valley, Kachin State, northern Myanmar.
As for the genus.
Imago: head length 3.38 mm, width 2.99 mm (excluding sizes of compound eyes), with sparse setae; labrum sclerotized, connecting to anteclypeus, width longer than length, anterior margin with short setae; apical tooth of mandibles not reaching the apex of labrum, first marginal tooth and apical tooth of left mandible divided in acute angle, other marginal teeth not visible; width of anteclypeus and postclypeus much longer than length; antenna with 22 articles; compound eyes hemispheric, slightly flat, diameter about 0.67 mm, lying on the middle position of the head, ommatidia diameter about 0.02 mm. Pronotum pilous, width about 3.35 mm, centraxonial length 1.97 mm, almost breaking away from the head. Wings long and broad with apex rounded, length 13.91 mm (excluding forewing scale), scale length 2.17 mm, wing width 5.02 mm; reticulated veins obviously pigmented among radial field and medial field, basal 5/8 of right hind wing hidden under right forewing. Forewing: scales with sparse setae, humeral margin convex, with weakly arched lobe present, basal suture curved; Sc simple, terminating on basal quarter of wing length; R with two branches in scale, terminating along anterior wing margin at half wing length; Radial field occupying about 1/8 wing area, left forewing with four branches, first branching at basal 1/3 of wing length, right forewing with three branches, first branching at basal 1/4 of wing length; M with two branches, branching at apical 1/5 of forewing; right CuA first branching in scale, occupying about 3/4 right forewing with three main branches, the branch near M vein branching at 1/2 of the wing length, the next branch branching near the middle of the wing to the base, and the branch near posterior margin branching in scale. Hind wing: basal suture not visible; large anal lobe present; left Rs with two branches branching from M at base; M with three branches. Legs: different degrees of damages to the legs, the left protarsus not preserved and the distal part of protibia not visible, the right mesotrochanter expanded and ruptured, and the large area of the left metacoxa broken; tibial spurs and spines not serrated. Abdomen: abdomen fragmentary, some of the detached abdominal segments can be observed, including the distal abdominal segments with a pair of cerci. Cerci trimerous; abdominal styli absent.
Drawings of Angustitermes reflexus gen. et sp. nov., holotype specimen CNU-TER-BU-2017005 (female imago) A drawing of habitus (ventral view) B–D drawings of femur, tibia, tarsi, arolium and claw of left hind leg, mid-leg and foreleg, respectively E drawing of head in dorsal view. Scale bars: 4.0 mm (A); 0.5 mm (B, C, D); 2.0 mm in (E).
Holotype. Myanmar • Kachin State, Hukawng Valley; forewing (margin partly missing) only; Kachin amber; CNU-TER-BU-2017006 (Fig.
Latin, reticulatus, meaning “reticulate”, which is in reference to the well-developed and clearly recognizable reticulated veins of holotype.
The specimen was collected from the upper Cretaceous (Cenomanian) deposits of the Hukawng Valley, Kachin State, northern Myanmar.
Forewing: wing length (excluding forewing scale) about three times as long as wide; forewing scale large; heavily reticulated, irregular bilayer structure in M and CuA, cross veins between Rs and M obvious; Sc, R, Rs, and M thickened, strongly sclerotized and obviously pigmented; Sc and R1 simple and short; Rs with seven or eight branches, with secondary branches, running parallel to costal margin; M with six branches, first branch of M arising at forewing mid-length, secondary branches present, medial field encompassing wing apex, angle of branches and main vein gradually increasing.
Forewing: forewing length (excluding forewing scale) 13.2 mm, width about 4.7 mm; suture length about 2.3 mm, strongly arched, making a sharp angle with posterior margin; distal costal margin slightly missing, posterior margin partially missing because of abrasion of the amber; base of costal margin rolled up, making the Sc and R poorly visible; Sc length 1.0 mm; R1 length 2.0 mm, Rs with eight branches; M slightly closer to Rs than to CuA, encompassing wing apex, six branches visible, angle of branches and main vein gradually increasing, so that branches terminate closely on margin, first branch of M arising at forewing mid-length, second branch arising at about distal third of forewing length, and base of third branch close to fourth branch with secondary branch.
The forewing of Mastotermes reticulatus sp. nov. is similar to that of Mastotermes monostichus Zhao, Eggleton & Ren, 2019, but there are some differences; the Sc, R, and Rs of Mastotermes reticulatus sp. nov. are closer, and there are fewer secondary branches, which makes the Rs veins parallel to the costal margin, instead of gradually narrowing as in M. monostichus. Compared with M. monostichus, the M vein of M. reticulatus sp. nov. is even more irregular and with fewer branches (Fig.
The number of antennal articles in Angustitermes reflexus gen. et sp. nov. is only 22 (Fig.
The sclerotized vein M of the forewings in Angustitermes reflexus gen. et sp. nov. are relatively simple, with only two branches and the medial fields, located in the anterior third, compressed. Concurrently, the distal-most branches of CuA, which end at the wing apex, are also thick and sclerotized, similar to M, and stronger than the other branches of CuA (Figs
We thank the editorial board of ZooKeys and express our gratitude to Prof. Scheffrahn and an anonymous reviewer for their critical and valuable reviews of the manuscript. We thank Xiaomin Yang for her kind help in the preparation of this study. We also thank Guoyi Zhang, Wei Gao, and Dawei Guo for the technical support and some useful comments.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This work was supported by grants from the National Natural Science Foundation of China [nos. 32101239, 42288201, 32020103006]; Support Project of High-level Teachers in Beijing Municipal Universities in the Period of 14th Five-year Plan [no. BPHR20220114]; and Central Public-interest Scientific Institution Basal Research Fund, CAFS [no. 2023TD12].
Yurong Jiang: data curation, formal analysis, methodology, writing-original draft; Xinru Deng: data curation, formal analysis, methodology; Chungkun Shih: formal analysis, writing-review and editing; Yunyun Zhao: formal analysis, writing-review and editing; Dong Ren: data curation, writing-review, supervision; Zhipeng Zhao: writing-review and editing, project administration, supervision.
Yurong Jiang https://orcid.org/0000-0002-7249-1377
Chungkun Shih https://orcid.org/0000-0002-3434-2477
Dong Ren https://orcid.org/0000-0001-8660-0901
Zhipeng Zhao https://orcid.org/0000-0002-6665-8943
All of the data that support the findings of this study are available in the main text.