Duappendactylus melanocephalus, Schall & Gu & Husemann, 2025

Schall, Ole-Kristian Odin, Gu, Jun-Jie & Husemann, Martin, 2025, Two new members of Tridactylidae (Orthoptera: Caelifera) from mid-Cretaceous Kachin amber, Zootaxa 5693 (2), pp. 168-178 : 170-171

Duappendactylus melanocephalus sp. nov.

Zoobank-ID: urn:lsid:zoobank.org:act:

Figs. 1–2

Etymology: The species is named after its dark-colored head (ancient Greek “mélas” = black and “kefáli” = head).

Locality and horizon: The specimen was included in amber found in Hkamti , Sagaing Division, Myanmar or Tanai, Kachin State Burma, Myanmar, two nearby amber mining locations. The amber from Hkamti is ca. 110 My and the amber from Tanai ca. 99 My old.

Holotype: Sex unknown. Specimen part of the LIB-Hamburg collection; collection number GPIH07246 (ex collection Martin Husemann MH0108).

Diagnosis of species: As for genus (monotypic).

Description: Preservation of an entire specimen with parts of the head and thorax somewhat obscured by additional matter in the amber.

Measurements (mm): Values given with a “ca.” are partly based on estimation as structures are not clearly or fully visible. Body length 1.41 (head to abdominal apex; not including subgenital plate). Head-height 0.54. Antenna length 0.55. Forewing length 0.47. Mesotibia length 0.45. Metafemur length 0.96. Metafemur width 0.38. Metatibia length ca. 0.89. Paraproct 0.34. Subgenital plate extending beyond paraproct by 0.16. Basal cercus segment length 0.21. Basal cercus segment width 0.06. Distal cercus segment length 0.09. Distal cercus segment width 0.01. Apical setae of subgenital plate length up to ca. 0.15.

Head: Antennae ten-segmented (including pedicel and scape), moniliform and with antennomeres relatively thick. Coloration of both head and antennae dark, close to black.

Thorax: Pronotum smooth, without elevation; of dark color. Forewings present, with reduced venation. Hindwings absent.

Legs: Prothoracic leg: Femur and tibia with setae which are more numerous on the tibia. Tibia apically with three dactyls, the longest of which is 0.04 mm long. Tarsus slender, with two claws.

Mesothoracic leg: Middle of tibia distinctly inflated.

Metathoracic leg: Femur greatly inflated along the entire length. Distal half of dorsal margin with evenly spaced setae of varying length. Tibia with a pair of subapical and apical spurs. Tarsus morphology uncertain due to poor visibility in the amber ( Fig. 2B shows best interpretation of what is visible).

Abdomen: Cerci two-segmented with basal segment longer and wider than distal segment. Distal segment very slender. Both segments with setae. Paraproct prominent, broad-triangularly shaped. Paraproctal processes absent. Subgenital plate prominent, orientated upwards and elongated far beyond paraproct, reaching up to half of the basal cercus segment; apically with long setae.

Remarks: The new specimen can be assigned to Tridactylidae based on the two-segmented cerci and the distinctly inflated mesotibia. Tridactylidae consists of three subfamilies: the Cretaceous to extant Tridactylinae Brullé, 1835 and Dentridactylinae Günther, 1979 and the Cretaceous Mongoloxyinae Gorochov, 1992 . The first two subfamilies are separated by a subapical denticular process which is present in Dentridactylinae , but not in Tridactylinae ( Heads, 2009) . Because the morphology of the metatarsus in Duappendactylus melanocephalus gen. et sp. nov. is obscured, the presence or absence of a subapical denticular process cannot be confirmed. Mongoloxyinae is characterized by a more elaborate forewing venation than in the other subfamilies ( Gorochov et al., 2006). The forewing venation of D. melanocephalus gen. et sp. nov. seems to be reduced (as in Tridactylinae and Dentridactylinae ), but this aspect of morphology is somewhat difficult to see in the fossil. Gorochov (2010) attributed the Burmese amber species Birmitoxya intermedia Gorochov, 2010 to Mongoloxyinae , but this act was solely based on the species not matching known characters of the other two subfamilies and the body morphology of Mongoloxyinae is rather unknown ( Gorochov, 2010). Recently, Schall et al. (2025) have speculated that the Burmecaelidae Uchida, Husemann & Kotthoff, 2024 may be allied to Mongoloxyinae as they share similar venation characters. Because of the above, the subfamily position of D. melanocephalus cannot be determined for now.

Within Tridactylidae , D. melanocephalus differs from all other members of the family except Birmitoxya intermedia by the absence of paraproctal processes.From Birmitoxya , the new taxon is separated by1) a proportionally shorter metatibia. 2) Two-segmented cerci. In Birmitoxya the cerci were one-segmented. It is unlikely that the reason for this is found in the nymphal status of the specimen described by Gorochov (2010) as modern nymphs of the species Ellipes deyrupi Woo, 2021 and Ellipes eisneri Deyrup, 2005 already have two-segmented cerci like the adults ( Woo, 2021). 3) Three strong dactyli on the protibia. Gorochov (2010) mentions “small fossorial denticles” in his description of B. intermedia , but they are not shown in Figure 6A of the species. 4) Smaller body size. In total, the scale of these differences appears to justify generic separation from Birmitoxya despite the shared absence of paraproctal processes.

The absence of paraproctal processes is unusual for Tridactylidae and also the closely related Ripipterygidae Ander, 1939 . However, it is an apomorphy of Cylindrachetidae Giglio-Tos, 1914 , but this family differs from the rest of Tridactyloidea in several other important characters (see introduction). Cylindrachetidae were estimated to have evolved 202.67 Mya, ca. 50 My prior to the other two families of Tridactyloidea ( Song et al., 2015). This would make a relationship between Cylindrachetidae and the Kachin amber Tridactyloidea without paraproctal processes seem unlikely. For now, it seems more conclusive to suggest this character state was once present in Tridactylidae and subsequently lost in their evolutionary history.

Figures

FIGURE 1. Duappendactylus melanocephalus gen. et sp. nov. holotype (sex unknown) GPIH07246. A. and C. Specimen, right lateral view. B. and D. Specimen, left lateral view. Scale bars = 1 mm.

FIGURE 2. Duappendactylus melanocephalus gen. et sp. nov. holotype (sex unknown) GPIH07246. A. and B. Detail of prothoracic leg and metathoracic tibia. Red arrows in A mark dactyli on protibia. Abbreviations: as = apical spurs; sas = subapical spurs; mtta = metatarsus; mtt = metatibia. Scale bars = 0.2 mm. C. and D. Detail of forewing, mesothoracic leg and metafemur. Abbreviations: ce = cerci; fw = forewing; mtf = metafemur; msf = mesofemur; mst = mesotibia. Scale bars = 0.5 mm. E. and F. Detail of abdomen. Abbreviations: pp = paraproct; sgp = subgenital plate; ce = cerci. Scale bars = 0.2 mm.