On the systematic position of the genus Notomicrus Sharp (Hydradephaga, Coleoptera)

Abstract

The systematic position of Notomicrus is clarified by a study of 13 skeletal characters of adults. Shape of antennomere I, profemoral excavation, paramedian angle of anterior metacoxal wall, "noterid platform," and the peculiar condition of the intercoxal wall are synapomorphies of Noteridae (excluding Phreatodytes) and Notomicrus. Therefore Notomicrus is a member of Noteridae. The broadened prosternal process, cranial extension of the noterid platform, metafurcal–metacoxal fusion, and swimming adaptations of the hind legs are regarded as synapomorphies of Noteridae excluding Notomicrus and Phreatodytes. Notomicrus is therefore the sister group of the remainder of Noteridae excluding Phreatodytes. Characters of the foreleg demonstrate that the noterid genera Pronoterus, Synchortus, Mesonoterus, Renotus, Noterus, Siolius, Hydrocanthus, Canthydrus, Suphisellus, and Suphis form a monophyletic unit and that Pronoterus is the sister group of the remainder of these genera. The following characters are assigned to the ground plan of Noteridae excluding Phreatodytes: antennomere I short and pseudo-two-segmented, midgular apodeme present, slender prosternal process with acuminate apex, profemoral excavation, protibia without burrowing spur, short protarsomere I, metacoxal–metasternal fusion absent, paramedian angle of the anterior metacoxal wall present, intercoxal wall forming a platform that overrides the furcal origin, noterid platform present but not extended to the metasternum, metafurcal–metacoxal fusion absent, hind legs without swimming adaptations.