Thonus Thorne, 1974
Note: Although Thonus is considered a
synonym of Crassolobium and,
based on dates of publication, would be the junior synonym, Pena-Santiago
and Ciobanu (2007) suggest a reversal of the precedence condition because
name Thonus identifies
a highly diversified taxon (more than 40 species are currently named with
this generic substantive while Crassolabium is
a poorly known and seldom used name, with only two species; (ii) Thonus is
a name that identifies a worldwide-distributed taxon, recorded in many (50)
bibliographic references on taxonomical, faunistical and ecological
subjects, whereas by contrast only a few (10) references are available on Crassolabium,
mostly discussing its taxonomy and status; (iii) Thonus
is a name that identifies a rather well-defined morphological pattern among
dorylaimid nematodes, and relevant morphological (and also biogeographical
and ecological information) is associated with it, obviously, that is not at
all the case of Crassolabium;
(iv) the etymology of Crassolabium,
meaning thick or fat lip, refers to a peculiar morphological feature that
does not fit the Thonus pattern
and whose taxonomical value has been demonstrated to be of minor
significance and interest.
However, despite those arguments, Pena-Santiago
and Alvarez-Ortega (2014) listed Thonus as a junior synonym of
Crassolobium! In the same paper, the rounded tail members of the
subfamily Qudsianematinae of the family Qudsianematidae were transferred to
a new subfamily (Labronematinae) of the family Dorylaimidae. In his
recent book, Dorylaimida Mundi (Nematoda) 2021, Pena-Santiago, ever and
appropriately an advocate for the Rules of Zoological Nomenclature, listed
the current species of Thonus under the genus name
Designated omnivore-predator by Yeates et al (1993).
Pena-Santiago, R. and Ciobanu, M. 2007. On the Identity of the Genus Crassolabium Yeates,
1967 (Dorylaimida: Qudsianematidae). J. Nematology 39:231-236.
Pena-Santiago, R. and S. Alvarez-Ortega. 2014. An integrative approach to
assess the phylogeny and the systematics of rounded-tailed genera of the
subfamily Qudsianematinae (Nematoda, Dorylaimida). Zoologica Scripta
Yeates, G.W., T. Bongers, R. G. M. De Goede, D. W. Freckman, and S. S.
Georgieva. 1993. Feeding habits in soil nematode families and genera—An outline
for soil ecologists. Journal of Nematology 25:315-331.