Xeniamia, Fraser, Thomas H. & Prokofiev, Artem M., 2016

Fraser, Thomas H. & Prokofiev, Artem M., 2016, A new genus and species of cardinalfish (Percomorpha, Apogonidae, Sphaeramiini) from the coastal waters of Vietnam: luminescent or not?, Zootaxa 4144 (2), pp. 227-242 : 231-232

Xeniamia new genus

Type species: Xeniamia atrithorax new species

Diagnosis. A genus of Sphaeramiini with the following unique morphological character combination: two epurals, fused hypurals 1+2, no terminal bony sheath over third and fourth hypurals, lacking uroneurals, one supraneural, two supernumerary dorsal spines, visible eighth dorsal spine (may appear hidden when damaged), fourth dorsal spine longest, smooth vertical edge and smooth unossified ventral edge of preopercle, third infraorbital without suborbital shelf, basisphenoid absent, scattered melanophores on silvery peritoneum, anterior intestine speckled with black spots to past first bend of intestine, two pale pyloric caeca at the anterior end of intestine, stomach black, intestine black from second bend to anus, black lining of the ventral and posterior oral cavity, and black spots on outer isthmus lining from external thoracic area.

Description. See species description.

Color in alcohol. See species description.

Distribution. South China Sea off Khanh Hoa Province, Vietnam.

Etymology. Xenos, Greek meaning stranger and Amia, Greek referring to a type of fish, often used with cardinalfish names, treated as feminine noun.

Remarks. Mabuchi et al. (2014) proposed new subfamilies and tribal classification for the Apogonidae . The subfamily key places Xeniamia in the Apogoninae . Using their generic key, Xeniamia falls out in the couplet segment with Jaydia and Ostorhinchus Lacepède 1802 excepting the reported eight first dorsal spines in Jaydia erythrophthalma Gon, Liao & Shao 2015 . No specimens were preserved for DNA analyses to help provide support for tribal placement.

Tribes we excluded for placement using morphologic characters are: Apogonichthyini (thin supramaxilla, third dorsal spine longest, stomach and intestine pale); Apogonini (large unossified preopercular flap, six first dorsal spines, second dorsal-fin spine longest, pale stomach and intestine except one species); Cheilodipterini (large canine or caninoid teeth, small supramaxilla, six first dorsal spines, second dorsal-fin spine longest, pale stomach and intestine); Glossamiini (large supramaxilla, six first dorsal spines, second dorsal-fin spine longest, pale stomach and intestine); Gymnapogonini (six first dorsal-fin spines, second dorsal-fin spine longest, narrow band of teeth with some caninoid teeth, terminal centrum fused with hypurals 3+4, parhypural fused with hypurals 1+2); Lepidamiini (small body scales, third dorsal-fin spine longest, pale stomach and intestine), Pristiapogonini (preopercular edges and ridge serrate, pale stomach and intestine, third dorsal-fin spine longest); Rhabdamiini (6–7 first dorsal-fin spines, second or third spine longest, anal fin with 11–13 soft rays, 24–31 gill rakers, terminal centrum fused with hypurals 1+2+3+4, pale stomach and intestine); Veruluxini (six first dorsal-fin spines, second spine longest, terminal centrum fused with hypurals 1+2+3+4, modified pyloric caeca) and Zoramiini (six first dorsal-fin spines, second spine longest, five free hypurals, three epurals). Characters of three other tribes are discussed in more detail.

The Ostorhinchini is known to have more than 91 species in at least four unresolved molecular lineages that lack distinctive independent morphologic support ( Mabuchi et al. 2014). Almost all known species have blackish stomachs and intestines. Many species have single stripe to multiple arrangements on the head and or body. All have a serrate edges of the preopercle, a very few species have six first dorsal-fin spines, most have seven first dorsal-fin spines, most have the third first dorsal-fin spine longest, a few have second first dorsal-fin spine longest, preopercle ridge smooth, edges serrate, 2–3 supraneurals, supramaxilla absent, basisphenoid present, shelf present on third infraorbital, one pair of reduced uroneurals or absent, three epurals, five free hypurals or 1+2 fused. Ostorhinchus moluccensis ( Valenciennes 1832) , O. monospilus ( Fraser, Randall & Allen 2002) and O. oxina ( Fraser 1999) variably have the fourth dorsal spine longer, equal or shorter. Ostorhinchus margaritophorus ( Bleeker 1854) is the only known species in the genus with fused hypurals 1+2. The only know species suspected of having luminous activity is Ostorhinchus gularis ( Fraser & Lachner 1984) . Xeniamia differs from all members of Ostorhinchini by the presence of eight first dorsal-fin spines, smooth ridge and edges of preopercle, absence of basisphenoid and suborbital shelf, single supraneural, melanistic patterns and absence of spotted, striped or banded pattern on flanks.

Xeniamia appears similar to species in the monogeneric Siphamiini but lacks the luminous apparatus along the ventral side of the body present in all Siphamia ( Gon & Allen 2012) . Species of Siphamia have six or seven first dorsal-fin spines; third dorsal spine longest; terminal centrum fused with upper hypural plate (3+4 hypurals fused) and free but fused 1+2 hypurals, or terminal centrum fused with hypurals 1+2+3+4 ( Fraser 1972). Xeniamia shares with some species of Siphamia a single supraneural, lacking an ossified basisphenoid, two epurals, no paired uroneurals, no terminal bony sheath over third and fourth hypurals and small size but differs from that genus by the presence of eight first dorsal-fin spines, fourth spine longest; presence of uroneurals, free upper hypurals 3 and 4, lacking a suborbital shelf, and melanistic patterns.

The Sphaeramiini are represented by seven genera and 55 species lacking molecular resolution for several genera ( Mabuchi et al. 2014). This tribe has genera with the following characters: no supramaxilla, three epurals, two or three supraneurals, two supernumerary dorsal spines, seven or eight first dorsal spines, some species with luminous organs, paired uroneurals, stomach and intestine pale, speckled or black, peritoneum pale or with speckled melanophores. All species of Nectamia Jordan 1917 have high gill raker counts (22-30), bars on body, seven first dorsal-fin spines, third dorsal spine longest, and both stomachs and intestine blackish. Sphaeramia Fowler & Bean 1930 and Pterapogon Koumans 1933 are deep bodied, with at least one bar on body, have seven first dorsal-fin spines, third dorsal spine longest and spinous procurrent rays. Quinca Mees 1966 is black and deepbodied ( Vagelli 2014), possibly belonging in Apogonichthyoides (see Fraser & Allen 2010). Apogonichthyoides Smith 1961 has serrated hind edge of preopercle, seven to eight first dorsal-fin spines, with third spine always longest, mostly dark body color with spotted or barred pattern and/or ocellus-like mark in some species, and cheek bars, peritoneum, stomach and intestine pale or spotted. All species of Jaydia are characterized by the fourth dorsal-fin spine longest, truncated or rounded caudal fin, ventral surface of head and/or isthmus bearing some melanophore pigmentation, light organs associated with the intestine present in some species. These characters suggest a likely relationship with our new genus than any other genus in the Sphaeramiini .

Xeniamia differs from known species of Jaydia by having a single supraneural, lacking an ossified basisphenoid, infraorbital without a shelf, two epurals instead of three, fused hypurals 1+2 instead of being free, lacking a bony sheath as part of the terminal centrum that covers the third and fourth hypurals, except present in Jaydia photogaster ( Gon & Allen 1998) and J. argyrogaster ( Weber 1909) , and a short visible eighth first dorsalfin spine (except present in Jaydia erythrophthalma Gon, Liao & Shao 2015 ) instead of a tiny nubbin hidden under the skin or absent. Like all Jaydia . the fourth first dorsal-fin spine in Xeniamia is longer than the third.

We place Xeniamia in the Sphaeramiini pending molecular information.