Abstract
Two new species of the southern African genus Xiphoscelis Burmeister, 1842 are recognised and described, X. braunsisp. nov. from the Eastern and Western Cape Karoo (South Africa) and X. namibicasp. nov. from the Huns Mountains of southern Namibia and adjacent ranges in South Africa. These were previously overlooked and grouped together with X. schuckardi Burmeister, 1842, but further material and more in-depth analyses have now revealed their clear separation on the basis of key diagnostic features, including clypeal structure, metatibial spur development and aedeagal shape. The densely and coarsely costate elytral structure and the black to brown colour of these species are symplesiomorphies shared with a number of the most primitive genera among the African Cetoniinae. However, these characters also reflect the convergent adaptation to hot and arid conditions they share with several other species occurring in this region. Phylogenetic relationships of the genus with other Cetoniinae are explored using the larval characters highlighted in the description of the 3rd instar larva of X. braunsisp. nov. The extraordinary hypertrophy observed in the male metatibial spur of species in this genus, and particularly in X. schuckardi, appears to represent a defence mechanism against potential predators on the ground, apart from playing a role during mating.
Highlights
The genus Xiphoscelis has been recognised since its first description as characterised by unique features, such as a narrow mesometasternal process, enlarged metafemur, low subhumeral elytral arch, round pronotum and regularly costate elytra
Apart from a number of characters that have led to believe that the genus Xiphoscelis may occupy a very primitive position in the phylogenesis of the Cetoniinae, species of the genus exhibit a most unusual feature, represented by the extreme hypertrophy of structures in their metalegs
This is very prominent in males but less so in females and includes the femora, spurs and especially the inner spines, which are truly extraordinary in their thickness, length and sharpness in virtually all the species of the genus, possibly with the exception of X. namibica sp. nov. (Fig. 2 A–C)
Summary
The genus Xiphoscelis has been recognised since its first description as characterised by unique features, such as a narrow mesometasternal process, enlarged metafemur, low subhumeral elytral arch, round pronotum and regularly costate elytra. Recent molecular analyses indicate that the phylogeny of Cetoniinae in general needs a substantial revision, as large incongruences with the traditional concepts are emerging (Šípek et al 2016) This applies to all the major classification systems proposed to date, namely those of Schenkling (1921), Krikken (1984) and Holm and Marais (1992). Further analyses of type specimens and availability of new material and data have revealed that another two species need to be erected in order to account for the differences observed in the populations that were collectively grouped under X. schuckardi by Perissinotto et al (2003) These are described here, along with an update of the biology of the genus and the first detailed description of the 3rd instar larval stage of a species These are described here, along with an update of the biology of the genus and the first detailed description of the 3rd instar larval stage of a species (X. braunsi sp. nov.) within the genus
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