Australian Journal of
Taxonomy
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Type species: Eburnocauda saxatilis Beasley-Hall & Iannello sp. nov.
Diagnosis. Eburnocauda can be distinguished from other rhaphidophorids by the extremely robust and long styli projecting from the male subgenital plate, reaching over half the length of the cerci. Eburnocauda also bears, on average, two ventral linear spines on either side of the fore and mid tibiae (prolaterally and retrolaterally); except for Parvotettix Richards, 1968 (which lacks these spines), all other Australian genera have at least three.
Description. Fore coxae armed with an anterolateral spine, all other coxae unarmed. Apical spination of femora variable, but all lack ventral linear spines. Fore femora unarmed apically, mid femora with a retrolateral apical spine only, hind femora unarmed prolaterally but variably bearing a retrolateral apical spine. All tibiae with both apical and linear spines. Fore and mid tibiae with two pairs of apical spines, one prolateral and the other retrolateral, with each pair containing one spine facing dorsally and the other ventrally; two rows of linear spines on the ventral surface, one prolateral and the other retrolateral, each row containing an average of 2 spines (range 2–3) (Fig. 3 i). Hind tibiae with apical spines as on the fore and mid tibiae, but also bearing a pair of subapical spines between each primary pair; linear spines on the dorsal surface variable. Fore and mid tarsi unarmed. Hind tarsi with a pair of apical spines on the first and second segments; third and fourth segments unarmed. Dorsal linear spines on first and second hind tarsal segments variable. Male styli robust, dramatically elongate, measuring more than double length of the suranal plate (Fig. 3 b, c). Female subgenital plate trilobed.
Remarks. Additional sampling was performed at BCC and surrounds following the placement of a single specimen of Eburnocauda as sister to Micropathus by Beasley-Hall et al. (2024). However, microscopy subsequently revealed two morphologically divergent populations separated by differences in leg spination and terminalia. One of these we describe here as Eburnocauda saxatilis sp. nov., the other being a new species of Cavernotettix. The latter also occurs at Sherbrooke Forest approximately 30 km to the southwest of BCC. The generic placement of Cavernotettix sp. at Sherbrooke has been confirmed using both morphological and molecular data and will form the basis of an upcoming taxonomic paper. In contrast, Eburnocauda saxatilis sp. nov. is only known from BCC, suggesting the two species may have divergent microhabitat requirements; it remains unknown as to whether they occupy different cave zones.
Eburnocauda can be considered unusual in its possession of dramatically elongate male styli, which are thought to assist in positioning the abdomen during copulation; these sensory structures have been shortened or lost in other Rhaphidophoridae, potentially a result of the development of other terminal structures which prevent displacement of males in mating pairs (Gorochov, 2001, 2014). Eburnocauda also has a notable arrangement of apical spines on the fore and middle femora. These segments are typically armed on both the prolateral and retrolateral surfaces—i.e., on either side of the “knee”—in other Australian Rhaphidophoridae, with the exception of Tasmanoplectron Richards, 1971 (variably present) and Parvotettix (always absent) (Richards, 1968, 1971a). In Eburnocauda, the fore femur is unarmed and the middle only armed on the retrolateral side. However, given the small number of individuals examined, we cannot rule out the absence of these structures owing to breakage in life.
Etymology. From the Latin eburno (ivory) and cauda (tail), alluding to the tusk-like styli found on the posterior of males. It is a feminine noun in the nominative singular case.