Belongs within: Scarabaeinae.
Amphistomus is an Australasian genus of dung beetles with a tuberculate dorsum and the underside of the pronotum deeply excavated to receive the fore legs.
Characters (from Matthews 1974): Oblong, trapezoidal or convex in cross-section, sides often nearly vertical, dorsal surfaces often flat. Small to medium (4-10 mm). Colour rufous to piceous, sometimes with slightly paler markings on elytra, or nitid bronzed spots. Densely clothed with curved setae which hold a layer of soil covering all dorsal surfaces, which are tuberculate and frequently also carinate. Head with clypeal edge with six teeth, of which middle two are a little longer. Edge between two middle teeth grooved. Frons with 0-3 tubercles. Eye canthus incomplete. Dorsal eye surfaces small to nearly absent, separated by at least ten widths. Labial palpi with distal segment minute, second segment a little smaller than basal one or subequal to it. Mentum broader than long, its distal edge distinctly angulately excised. Anterior part of underside of pronotum deeply excavated to receive femora, the excavation bounded posteriorly by a strong carina. Lateral edge present only on anterior half, where it forms a very prominent, subquadrate shelf-like extension of anterior angles. Pronotum strongly convex, with tubercles arranged in a basic pattern with a maximum of 18, some of which may be absent and others, particularly TA1 and TB1, fused to form carinae. Hind edge not beaded. Elytra with discal surface flat or concave, forming very sharp fold at juncture with pseudepipleura in winged species. With ten striae, seven on disc and three on pseudepipleura, striae very shallow, intervals not at all convex. Tubercles present on odd-numbered intervals only, varying in size and number, but always including at least some of series EA, EB, and EC. Lateral edges of elytra with series of teeth, tubercles, or undulations. Hind Wings either fully developed, brachypterous, or entirely absent. Mesosternum 3-5 times as wide as long, sometimes with a median longitudinal ridge. Mesometasternal suture more or less straight, may be indistinct. Middle of metasternum flat or depressed, forming a strong angle with subvertical lateral lobes behind mid coxae. Fore tibia with distal edge straight, at right angle with inner edge. Outer edge with 3 large teeth. Fore spur small, tapering, simple. Middle tibia with 2 transverse carinae on outer face, hind tibia sometimes with trace of 1 or both of these carinae. Mid coxae short, parallel, widely separated, situated on outer edge of ventral surface. Femora with an extra longitudinal carina on ventral face, running entire length of ventral face somewhat behind middle. Tarsi small, length of hind tarsus contained about 3 times in length of tibia. Hind tarsus with basal segment longer than second segment. Claws very small, simple. Sternites foreshortened, crowded together in middle. Propygidium with very strong hind border usually bearing a median tubercle. Pygidium flat to moderately convex, finely bordered, with a maximum number of 7 tubercles on disc. Male genitalia with parameres symmetrical.
<==Amphistomus Lansberge 1874 [=Merodontus Macleay 1871 non Jekel 1854, Platyphymatia Waterhouse 1874] CW92
|–*A. calcaratus (Macleay 1871) (see below for synonymy) CW92
|–A. accidatus Matthews 1974 CW92
|–A. complanatus Matthews 1974 CW92
|–A. cunninghamensis Matthews 1984 CW92
|–A. inermis Matthews 1974 CW92
|–A. macphersonensis Matthews 1974 CW92
|–A. montanus Matthews 1974 CW92
|–A. opacus Matthews 1974 CW92
|–A. palpebratus Matthews 1974 CW92
|–A. pectoralis Matthews 1974 CW92
|–A. primonactus Matthews 1974 CW92
|–A. pygmaeus Matthews 1974 CW92
|–A. speculifer Matthews 1974 CW92
|–A. squalidus (Macleay 1887) [=Merodontus squalidus CW92
|–A. storeyi Matthews 1974 CW92
|–A. trispiculatus Matthews 1974 CW92
|–A. tuberculatus (Lansberge 1885) [=Platyphymatia tuberculata] CW92
`–A. tuberosus Matthews 1974 CW92
*Amphistomus calcaratus (Macleay 1871) [=*Merodontus calcaratus, *Platyphymatia calcarata; incl. P. aeneopicea Waterhouse 1874] CW92
*Type species of generic name indicated
[CW92] Cassis, G., & T. A. Weir. 1992. Scarabaeinae. In: Houston, W. W. K. (ed.) Zoological Catalogue of Australia vol. 9. Coleoptera: Scarabaeoidea pp. 106–173. AGPS Press: Canberra.
Matthews, E. G. 1974. A revision of the scarabaeine dung beetles of Australia. II. Tribe Scarabaeini. Australian Journal of Zoology, Supplementary Series 24: 1–211.