A key and diagnostic compendium to the species of the genus tylenchorhynchus cobb, 1913 (nematoda: belonolaimidae).

An identification key to 111 species of Tylenchorhynchus is given. Tylenchorhynchus is defined as containing only those species with four incisures in the lateral field. A compendium providing the most important diagnostic characters for use in identification of species is included as a supplement to the key. Some species in a related but unnecessary genus were placed in the genus Tylenchorhynchus, based on morphological structures and logical groupings of the species. Bitylenchus iphilus is transferred to Tylenchorhynchus. The diagnosis of Tylenchorhynchus is emended, and a list of all the valid species of the genus is given. The characters most useful for separating species are the stylet length, shape of lip region, number of lip annules, shape of tail and tail terminus, number of tail annules, and position of vulva (V%). As defined in the paper, the genus currently is composed of 111 valid species.