Three new species are described in the extinct Cretaceous histerid genera Phasmister Caterino (Phasmister hkamticus Caterino and Yamamoto, new species and Phasmister parallelus Caterino and Yamamoto, new species) and Carinumerus Caterino (Carinumerus intricatus Caterino and Yamamoto, new species). Phasmister hkamticus represents the first histerid and the first formally described coleopteran taxon from the slightly older (ca. 110-Ma) Hkamti amber, of a different geographical and geological background from that of Kachin amber (ca. 100 Ma) also from northern Myanmar. Although we report only a single species from Hkamti amber, similarities between these two amber deposits' faunas may be implied by similarities to histerid taxa otherwise described from Kachin amber. These genera now comprise three species each, from a relatively small region, suggesting a considerable diversity in these genera and underscoring the amazing diversity of Onthophilinae in the Mesozoic.