Euconnus macleayii Jałoszyński 2023
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Euconnus
Euconnus macleayii

description: Euconnus (incertae sedis) macleayii (King)
Heterognathus Macleayii King, 1864: 99.
Scydmaenus (Cholerus) macleayii (King); Csiki, 1919: 72.
Remarks. The holotype of this species, which is the only specimen mentioned by King (1864), was not found in the Australian Museum in Sydney (D. Smith, email to the author dated 15.04.2021), or in any other Australian institutional collection.
Heterognathus macleayii was placed by King (1864) in a genus which he characterized as having the terminal maxillary palpomere ‘globular’, in contrast to ‘conical’ in his ‘ Scydmaenus ’ (which was a misidentified stenichnine genus Euconnus). This suggests that all species of King’s Heterognathus belong in Scydmaenus, which has the terminal maxillary palpomere not elongate conical, as in Stenichnini, but dome-shaped. However, King placed in the same genus Heterognathus armitagei, which is clearly an Euconnus and has a conical maxillary palpomere 4. The description of H. macleayii is extremely short and includes only the following line: “ Piceus politus, thorace transverse fossulato; elytris castaneis humeris plicatis, plicatura longitudinali ad medium extensa ”. The phrase “ thorace transverse fossulato ” helps excluding this species from Scydmaenus. Among Australian (and world) species of Scydmaenus, the pronotum can bear a variable number of antebasal pits or can lack any pits. In nearly all species there is an extremely fine transverse ‘wrinkle’ or a marginal basal carina, but it is barely discernible under stereomicroscopes and it usually requires SEM to be visible. It is highly doubtful that King in 1864, long before stereomicroscopes became invented and made available for scientists (Simon-Stickley 2019), was able to notice this carina and even more doubtful that in this case he would describe the pronotum as “ transverse fossulato ”, which implies a transverse impression, a fossa or sulcus. For species of the true Scydmaenus bearing antebasal pronotal pits, King uses unambiguous phrases “ thorace 4-foveolato ” and “ 2-foveolato ” (for H. geniculatus and H. princeps, respectively; King (1864): 98). King clearly made a distinction between antebasal pits (thorace foveolato) and a transverse groove or impression (thorace transverse fossulato). The misplaced Heterognathus armitagei, which belongs in Euconnus and has a transverse antebasal pronotal groove, was described in a similar way as H. macleayii, with “ thorace fossula transversa basali ”. As no Australian (or any other) species of Scydmaenus has a transverse fossula on the pronotum, H. macleayii must belong in Stenichnini. The maxillary palpomeres in beetles measuring below 2 mm are difficult to examine, so errors in a tribal and generic placement in the 19th century are not unusual. The easier structure to examine, and used by King (1864) in his key to genera, is the distance between the metacoxae. He divides Australian Scydmaeninae genera into two groups: (1) those with “posterior legs contiguous”, and (2) those with “posterior legs distant”. This division is correct in the case of species placed both in the group 1 (Phagonophana King, 1864, which includes species currently classified in Euconnus Thomson, 1859, Horaeomorphus L.W. Schaufuss, 1889, Sciacharis Broun, 1893, Scydmaenozila Jałoszyński, 2014b, and Syndicus Motschulsky, 1851; and Scydmaenilla King, 1864), and the group 2 (Scydmaenus sensu King, which includes species currently placed in Euconnus; Megaladerus Stephens, 1835, which is a junior synonym of Cephennium Müller & Kunze, 1822, but the only Australian species described by King is currently in Cephennomicrus Reitter, 1907; and Heterognathus which includes species currently placed in Scydmaenus and, as it was discovered during the present study, also in Euconnus). Currently known Australian Stenichnini with broadly separated metacoxae and the transverse antebasal pronotal groove can be found only in the extremely rare Kangarooconnus Jałoszyński (in Jałoszyński & Newton 2017) (but this genus has a conspicuous median longitudinal pronotal carina that could hardly pass unnoticed by King), a rare Leascydmus Jałoszyński, 2014b (but this genus has a faint transverse pronotal groove, difficult to notice without a stereomicroscope, and it does not have the humeral folds, which in H. macleayii reach the middle of elytra: “ plicatura longitudinali ad medium extensa ”), and in the common and abundant Euconnus. Other than those, the broadly separated metacoxae can be found in Cephennodes Reitter, 1884, Cephennomicrus, and Paraneseuthia Franz, 1986d, the only genera of Cephenniitae known to occur in Australia, but their body shapes are so different from those in Scydmaenini and Stenichnini that King would not have placed any of them in Heterognathus (he knew Cephennomicrus, which he misplaced in Megaladerus). Unless H. macleayii belongs in a genus unknown to me, the above discussion leads to excluding this species from Scydmaenus, and tentatively placing it in Euconnus, as the most probable choice.
description: Published as part of Jałoszyński, Paweł, 2023, Scydmaenus Latreille of Australia: Revision of species in subgenera Choleropsis Franz, Kingius Franz, Mascarensia Franz, Parallomicrus Franz, Scottiscydmaenus Franz, and description of Ascydmaenus subgen. n. (Coleoptera, Staphylinidae, Scydmaeninae), pp. 1-75 in Zootaxa 5371 (1) on page 71, DOI: 10.11646/zootaxa.5371.1.1, http://zenodo.org/record/10144644