Sandracottus bakewellii guttatus Sharp, 1882 stat. nov. Figs 23, 33, 47 Sandracottus guttatus Sharp, 1882: 688 (type locality: Adelaide (?) [most probably mislabelled], South Australia, Australia); Régimbart 1899: 337 (descr.); Zimmermann 1920: 234 (cat.); Watts 1978: 148 (syn.); Hájek and Nilsson 2024: 91 (cat.). Sandracottus rotundus ab. reductus Zimmermann, 1926: 97 (misidentification, infrasubspecific name). Type material. Lectotype: Male, “ Australia? Adelaide 984 guttatus ”, “ Lectotype ”, “ Sharp Coll. 1905-313. ”, “ Sandracottus guttatus Sharp Det. C. Watts 1979 ” (NHMUK). Paralectotype: Female, “ Carpentaria 984 ”, “ Paralectotype ”, “ Sharp Coll. 1905-313. ”, “ Sandracottus guttatus Sharp Det. C. Watts 1979 ” (NHMUK). Examined. Sandracottus rotundus ab. reductus Zimmermann, 1926: 1 female, “ Burg Station I 10. II. - 16. III. 1921, L. J. Toxopeus ”, “ Type ”, “ ab. reductus Zimmerm ” [handwritten by Zimmermann] (ZSM). This specimen clearly belongs to S. bakewellii guttatus. Toxopeus has collected it at a cattle station [Burg Station], somewhere in Central Australia. Examined. Additional material. (63 specimens): Australia. • Northern Territory: 1 ex., “ N. Territory, S. Aust. ”, “ Coll. Kraatz ” “ Zimmermann det. ” (DEI); 2 exs., “ Moreton Bay ” [doubtful record] (NHMUK); 1 exs., “ Moreton Bay ”, “ guttatus Shp ” [handwritten label by Régimbart but doubtful record] (MNHN); 2 exs., “ Ormiston Gorge, X. 1972, M. Baehr leg. ” (ZSM, CLH); 6 exs., “ Tallipatta Gorge, 20. VII. 1947, C. W. Brazenov leg. ” (VIC); 2 exs., “ Hart Range C. Barrett leg., F. E. Wilson coll. ” (VIC); 3 exs., “ Central Australia Collection Horn Expedition, VII. 1897 ” (VIC); 3 exs., “ Illamurta Springs Conservation Reserve, small temporary rock pool, sandy bottom, S 24.19 E 132.41, 16. III. 1995, T. Weir leg. ” (ANIC); 1 ex., “ Finke Gorge NP, temporary pools above old Ranger Station, 12. III. 1995, T. Weir leg. ” (ANIC); 2 exs., “ Finke Gorge NP, gorge W of Finke River, permanent and temporary rock pools, algal growth and detritus, S 24.08 E 132.51, 15. III. 1995, T. Weir leg. ” (ANIC); 2 exs., “ Finke Gorge NP, Palm Valley, small temp. pools, rocky, some sandy base, algal growth, detritus, S 24.03 E 132.43, 14. III. 1995, T. Weir leg. ” (ANIC); 3 exs., “ 45 km W of Alice Springs, Standley Chasm S 23.43 E 133.28 5. XI. 1979, T. Weir leg. ” (ANIC); 6 exs., “ 38 km SSE of Alice Springs S 24.01 E 134.01 7. XI. 1979, T. Weir leg. ” (ANIC); 1 ex., “ 60 km S of Alice Springs Ooraminna rockhole S 24.05 E 134.00 9. IV. 1981 M. Malipatil & J. Hawkins leg. ” (NTM); 1 ex., “ 60 km S of Alice Springs, Ooraminna rockhole, 24.05 S 134.00 E, 25. VII. 1976, G. Griffin leg. ” (NTM); 2 exs., “ 80 E of Alice Springs, Standley Chasm 26. III. 1979 G. Griffin leg. ” (NTM); 5 exs., “ Alice Springs Old Huckitta Homestead, 20. VII. 1970, D. Nelson leg. ” (NTM); 2 exs., “ Alice Springs, Valley of the Eagles, 14. II. 1971 N. T. M. B. D. Nelson leg. ” (NTM); 1 ex., “ Tallaputta Gorge, 7. IX. 1958 ” (NTM); 1 ex., “ Kings Canyon George Gill Range 25. - 26. III. 1983 at light I. Archibald leg. ” (NTM); 3 exs., “ Kings Canyon, George Gill Range 24. V. 2006 C. H. S. Watts leg. ” (ZSM, SAMA); 2 exs., “ Northern Territory, nr. Reedy Rockhole Amadeus Basin 12. IX. 1962 25-018565, - 24.33333, 131.5833, P. Ranford leg. ” (ANIC); 5 exs., “ Northern Territory Standley Chasm 43 km W by S of Alice Springs, 11. X. 1972, 25-018569, - 23.71667, 133.4667 M. S. Upton leg. ” (ANIC). • Western Australia: 12 exs., “ Rawlinson Range 22. VII. 1967 K. J. Richards leg. ” (WADA). Comments on classification. Specimens with reduced yellow basal, subbasal and apical elytral markings or almost completely black elytra and pronotum (Fig. 47) have been described as Sandracottus guttatus Sharp, 1882 but were later synonymised with S. bakewellii by Watts (1978). Despite the fact that they are genetically (cox 1) and morphologically identical with specimens from coastal northern and eastern Australia, they have a very restricted distribution in the ranges and gorges of Central Australia, and no intermediate forms are known so far. We propose subspecific rank for the population from Central Australia. The form described by Zimmermann as “ ab. reductus ” also refers to such a dark specimen with reduced yellow elytral markings. Distribution. Central Australia (e. g., Macdonnell Ranges, Finke Gorge, Rawlinson Range) (Fig. 23). Differential diagnosis. The subspecies S. bakewellii guttatus can be separated from S. bakewellii bakewellii by less expanded and interrupted yellowish antemedian, postmedian and preapical yellow markings on elytra (Figs 46, 47). Habitat. Sandracottus bakewellii guttatus inhabit more or less permanent pools of seasonal streams and creeks, and spring fed pools. The adults are generally found in places where the water is shaded. Habitats are often enriched with dead leaves and twigs (Fig. 33). Conservation. An isolated subspecies with a very small range which needs special conservation attention as surface water in this area is very limited.

Published as part of Hendrich, Lars & Brancucci, Michel, 2025, Revision of the Oriental and Australasian diving beetle genus Sandracottus Sharp, 1882 (Coleoptera, Dytiscidae, Dytiscinae), pp. 87-147 in ZooKeys 1223 on pages 87-147, DOI: 10.3897/zookeys.1223.138220