Bioacoustics of Duappendactylus melanocephalus

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.