Diposthidae ( Woodworth, 1898 )

Diposthidae ( Woodworth, 1898) View in CoL , amended

A third, well-supported cotylean clade is formed by representatives of all currently known Pericelis species plus Diposthus popeae . Earlier studies reported that the genus Diposthus lacks a cotyl ( Hyman, 1959b; Woodworth, 1898). Our examination of the type material is equivocal owing to the poor quality of fixation and sectioning. However, we collected 14 specimens of Diposthus from locations in Panama, Curaçao, Honduras and the US Virgin Islands, and all of them had a cotyl ( Fig. 7B). Furthermore, Faubel (1984: 201) claimed that Diposthidae lack cement pouches (what he calls mucous gland chambers). Histological sections of our newly collected material unambiguously revealed the presence of cement pouches ( Fig. 7B). The genus (and most probably the family) clearly belongs to Cotylea. Diposthus is unique in possessing an accessory prostatoid organ that empties independently of the penis papilla into the male atrium ( Fig. 7B).

Pericelidae View in CoL is a monogeneric family with four species. Their cotylean classification is warranted because of a cotyl, cement pouches and uterine vesicles. However, like Cestoplanidae View in CoL and Boniniidae View in CoL , pericelids also exhibit acotylean affinities, such as a centrally located ruffled pharynx, anteriorly directed uteri and marginal eyes encircling the entire body. Furthermore, the brain of Pericelis cata Marcus & Marcus, 1968 View in CoL connects to four conspicuous globuli cell masses (an acotylean trait), forming mushroom bodies ( Quiroga et al., 2015).

Given that our results reveal a well-supported relationship between Pericelis spp. and Diposthus popeae View in CoL , we here formally subsume all pericelids in Diposthidae View in CoL and abolish the family Pericelidae View in CoL . Because Pericelidae View in CoL is currently monogeneric, we argue that amending Diposthidae View in CoL to include Pericelis View in CoL is more appropriate than to create a new superfamily. Thus, Diposthidae View in CoL now contains a monospecific Asthenoceros View in CoL , two species of Diposthus View in CoL and four species of Pericelis View in CoL . The type genus continues to be Diposthus View in CoL due to chronological precedence and the genera remain distinct by the absence of an accessory prostatoid organ and the presence of a true seminal vesicle in Pericelis View in CoL . We here formally amend Diposthidae View in CoL to include cotyleans of an oval to slightly elongate body shape, with short, well-separated marginal pseudotentacles and uterine vesicles. Additionally, the prostatic vesicle of Diposthus View in CoL and Pericelis View in CoL is atypical, because it consists of prostatic tissue lining the ejaculatory duct within a thick, well-developed penis papilla ( Fig. 8). Possible similarities with respect to the nervous system (e.g. globuli cell masses, mushroom bodies) await an examination in Diposthus View in CoL .

Recently, Bahia et al. (2017) created Periceloidea based solely on two species of Pericelis . With our addition of Diposthus to the phylogeny, we showed that Periceloidea (sensu Bahia et al., 2017) is not supported, and therefore, we abolish this superfamily.