The New World rove beetle genus Dacnochilus LeConte, 1861, is revised. Cladistic analysis of 29 characters of adult morphology and male genitalia indicates that Acalophaena Sharp, 1884, is paraphyletic in relation to Dacnochilus. The monophyly of Acalophaena Dacnochilus is supported by five synapomorphies: 1) labrum with broad, deep emargination; 2) three or more rows of punctures on elytral disk; 3) epipleural carina present; 4) lateral macrosetae on head, pronotum, and elytron of medium size, and 5) the lateral sclerites of tergum IX large, narrow, and sharp ended.

A revised concept of Dacnochilus, inclusive of Acalophaena, treats Acalophaena Sharp, 1884, as a new synonym of DacnochilusLeConte, 1861, with twelve new combinations for species formerly placed in Acalophaena: Dacnochilus angularis (Erichson, 1840), Dacnochilus argentina (Bernhauer, 1912), Dacnochilus basalis (Lynch, 1884), Dacnochilus bruchi (Bernhauer, 1927), Dacnochilus bruchiana (Bernhauer, 1933), Dacnochilus compacta (Casey, 1905), Dacnochilus germana (Sharp, 1876), Dacnochilus horridula (Casey, 1905), Dacnochilus macularis (Erichson, 1840), Dacnochilus obscurior (Bernhauer, 1933), Dacnochilus pagana (Sharp, 1876), and Dacnochilus polita (Sharp, 1876). Twelve new species of Dachnochilus are described: D. atrus, D. bilobatus, D. ecuatoriensis, D. grandioculus, D. huautlae, D. megistothorax, D. nahuiollinae, D. newtoni, D. nigrapicalis, D. rociae, D. xilonenae, and D. zaragozae. Five new synonyms are established: Acalophaena laevipennis Bernhauer, 1908, and Acalophaena longipenms Bernhauer, 1933, are new junior synonyms of Dacnochilus basalis (Lynch, 1885); Acalophaena daguerrei Bernhauer, 1933, is a new synonym of Dacnochilus bruchi (Bernhauer, 1927); Lithocharis picta Sharp, 1876, is a new junior synonym of Dacnochilus pagana (Sharp, 1876); Dacnochilus fresnoensis Leech, 1939, is a new junior synonym of Dacnochilus laetus LeConte, 1863. A neotype is designated for Lithocharis macularis Erichson, 1840. Lectotypes are designated for seven species: Lithocharis angularis Erichson, 1840; Acalophaena argentina Bernhauer, 1912; Acalophaena bruchi Bernhauer, 1927; Lithocharis germana Sharp, 1876; Dacnochilus laetus LeConte, 1863; Lithocharis pagana Sharp, 1876; Lithocharis polita Sharp, 1876.

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