[ref. ID; 6578 (Pietro Omodeo, 1987)]
Family Haplotaxidae
Syn; Phreoryctidae, Michaelsen, 1928
R.O. Brinkhurst in an excellent monograph (1966) has proposed a new diagnosis of this family. This diagnosis, however, needs some retouches, to include Pelodrilus africanus Cenosvitov, 1939, Pelodrilus falcifer Omodeo, 1958, and Lycodrilus kraepelini Michaelsen, 1914, considered by Brinkhurst incertae sedis, and the two new genera Tiguassu and Metataxis described afterward by Righi and coworkers (1978) and by Righi (1985). Brinkhurst (1966) merged all the genera known until then into the single genus Haplotaxis because he felt there was insufficient knowledge to define genera in the family. The arguments that endorse my views are discussed under the heading of the genera Villiersia and Metataxis.
Diagnosis
Setae are usually sigmoid, and single-pointed (but single and double-pointed in Hetechaetella, pectinate in Adenodrilus), two to eight per segment; the setae of each row often differ in form and size from those of other rows; when the setae are eight per segment they show the lumbricine arrangement; genital setae present in some species. Cuticle thick to very thick. Clitellum formed by a single layer of glandular cells in the region of the genital pores. Holonephridia in adult begin after the gonadial segments; in some species these are pairs of holonephridia in a few pregonadial segments. Dorsal and ventral vessels connected in some anterior segments by a pair of long sinuous commisural vessels: cutaneous capillaries lacking. Gut devoid of typhlosole and calciferous glands, sometimes with a single esophageal gizzard. Testes in segment X and XI (or IX and X) or X. Ovaries in XII or XII and XIII (rarely XI and XII) or XI. Eggs are mesolecithic. Male efferent ducts short, sometimes coiled; they open one (rarely two) segments caudad to the corresponding gonadial segment. Female pores in, or posterior to the posterior furrow of the ovarian segment. Ovisacs large, containing the sperm sacs; in some genera ovisacs and sperm sacs are unpaired, in other genera they are paired. Atria absent. Spermathecae lateral or dorsal, in pregonadial segments. The taxon has been recorded for the world, India and Madagascar excepted. In fresh or brackish water, in mud, seldom in wet mould; most species prefer phreatic subterranean waters.