Rathkeidae Russell, 1953 emend. Schuchert, 2007

Wang, Chunguang, Xu, Zhenzu, Huang, Jiaqi, Guo, Donghui, Lin, Mao & Xia, Zhen, 2016, Taxonomic notes on Hydroidomedusae (Cnidaria) from South China Sea III: Family Rathkeidae and Zancleopsidae, Zoological Systematics 41 (4), pp. 392-403 : 393-394

Family Rathkeidae Russell, 1953 emend. Schuchert, 2007

Rathkeidae Russell, 1953b: 137 ; Kramp, 1961: 71; Bouillon et al., 2006: 155; Schuchert, 2007: 282–283.

Lizziinae Russell, 1953b: 144 .

Type genus: Rathkea Brandt, 1838 .

Diagnosis. Medusa bell-shaped, manubrium either with four elongated lips forming simple or branched oral arms with terminal knobs, or perradial unbranched oral tentacles inserted vertically or very oblique at level of mouth margin; immature ones with or without interradial medusa buds; with four or eight radial canals and a circular canal; usually eight marginal bulbs, interradial ones with more than one tentacle, rarely only four bulbs and four tentacles; ocelli absent; gonads encircle manubrium completely.

Remarks. Family Rathkeidae medusa includes two genera: Allorathkea Schmidt, 1972 and Rathkea Brandt, 1838 (Bouillon & Boero, 2000; Bouillon et al., 2006; Xu et al., 2014). Based on results of 16S sequence data, Schuchert (2007) suggested that the genus Lizzia Forbes, 1846 should be removed from the Bougainvilliidae Lutken, 1850 and transferred to the Rathkeidae Russell, 1953 . Reexamination shows that the position and attachment of oral tentacles of Lizzia blondina Forbes, 1848 are distinct from those in Bougainvilliidae . The oral tentacles of Lizzia are free at the level of the lips and not above the mouth rim. They are also attached very obliquely and remain adnate to the manubrium for quite some distance, being continued as ridges along the manubrium accompanied by underlying vacuolated gastrodermal cells ( Fig. 1). The same character is also found in Rathkea species ( Fig. 2). Because its oral tentacles do not originate above the mouth just like in Bougainvillia , Lizzia blondina Forbes, 1848 is closer related to the Rathkeidae than the Bougainvilliidae ( Schuchert, 2007) . According to Schuchert’s view, Hydractinia minuta ( Mayer, 1900) and H. minima ( Trinci, 1903) should be removed from the Hydractiniidae L. Agassiz, 1862 . Hydractinia minuta is regarded as a conspecific with Lizzia blondina and the genus Podocorynoides was proposed by Schuchert (2007) to accommodate Hydractinia minima ( Trinci, 1903) (= Cytaeis minima Trinci, 1903 ).

As mentioned above, the family Rathkeidae (medusa) thus comprises four genera: Allorathkea Schmidt, 1972 , Lizzia

Forbes, 1846, Podocorynoides Schuchert, 2007 and Rathkea Brandt, 1838 .

Key to medusae of all Rathkeidae genera.

1. Four radial canals .................................................................................................................................................................................2

Eight radial canals...................................................................................................................................... Allorathkea Schmidt, 1972 2. Obliquely or vertically inserted oral tentacles with a distinct, round pedicel ....................................................................................... 3

Oral arms elongated corners of the mouth ........................................................................................................ Rathkea Brandt, 1838 3. Eight marginal bulbs, perradial ones sometimes with more than one tentacle ..................................................... Lizzia Forbes, 1846 *

Four bulbs, each with one tentacle only .......................................................................................... Podocorynoides Schuchert, 2007 * * Present in South China Sea.