Named by Dumitrica & Matsuoka.
Diagnosis: A species of Ares with apical horn much shorter than ventral spine; dorsal spine straight running along thorax, and thorax campanulate with thick, undulate distal end.
Original description: Test conical with a slight constriction at the middle of thorax resulting in a campanulate shape. Cephalis small, poreless, displaced on the dorsal side of the apical part of shell. Ventral spine long, curved, and bladed. Apical horn much shorter than ventral spine; obliquely upward directed and slightly curved when longer. Dorsal spine straight, thin, circular in cross section beyond thorax; it is longer than the thorax and tangential to it. Pores of thorax quincuncially arranged, pore frames usually hexagonal, increasing in size distally. Distal end of thorax expanded, thick, and undulate.
Original remarks: Ares avirostrum n. sp. differs from all the other species of the genus so far known in that the distal part of thorax is clearly delineated. It is morphologically intermediate between A. cuniculiformis n. sp. and A. cylindricus Takemura. From the former it differs in having a much shorter apical horn; from the latter it differs in having a rather long apical horn and a straight dorsal spine, which is adjacent to the wall of thorax. A. avirostrum is very close to Ares takemurai n. sp. but differs in being slightly more slender and the distal part of thorax is constricted and built of intervening bars that become thinner and thinner. Ares sp. A of Baumgartner et al. (1995a) differs from Ares avirostrum n. sp. in having a more robust and curved dorsal spine and a narrower thorax.
Etymology: From the Latin avis bird and rostrum beak; noun.