Cerogobius, Kovačić & Bogorodsky & Troyer & Tornabene, 2019

Kovačić, Marcelo, Bogorodsky, Sergey V., Troyer, Emily M. & Tornabene, Luke, 2019, Cerogobius petrophilus (Perciformes: Gobiidae), a new gobiid genus and species from the Red Sea, Zootaxa 4565 (2), pp. 171-189 : 173-177

Cerogobius gen. nov.

Diagnosis. The new genus has the following combination of characters unique among known gobiid genera: 1) unpaired horn-like tentacle at the level of nostrils on the snout midline ( Fig. 1A ); 2) snout with steep profile from lateral view and very short, about 0.4–0.5 of eye diameter; 3) orbit projecting forward and elevated, obviously extending above dorsal profile of the head; 4) posterior angle of jaws extends behind vertical through posterior edge of eye; 5) lower limb of first gill arch joined to gill cover by membrane; 6) caudal peduncle deep and short, 0.8-0.9 of body depth at anal-fin origin, and caudal-peduncle depth slightly to distinctly greater than its length; 7) segmented caudal-fin rays 17; 8) pelvic fins completely separated and without frenum ( Fig. 1C ); 9) head and body completely scaleless; 10) no head canals; 11) preorbital rows r, s, s 3 each reduced to a single papilla; 12) suborbital sensory papillae rows a and b absent; four very short transverse suborbital rows of sensory papillae (1-4) present, row 1 oblique, reaching upper lip, row 2 distant from eye, close to row d, rows 3 and 4 close to posteroventral edge of eye and distant from row d, row d short; 13) oculoscapular rows reduced to rows x 1, x 2, z, as 1 and as 2, with only x 1 having more than 2 papillae ( Fig. 2 ); 14) dorsal-fin pterygiophore insertion pattern 3-22110; 15) 10 precaudal vertebrae + 17 caudal vertebrae; 16) hypurals 1–2 and 3–4 not fused, distinctly separate along entire length; 17) two anal-fin pterygiophores inserted anterior to haemal arch.

Description. Body elongate, laterally compressed posteriorly, caudal peduncle short and deep, its depth 0.8– 0.9 of body depth at anal-fin origin, caudal peduncle 1.04–1.17 times deeper than its length ( Fig. 3 ). Head slightly depressed, head depth 0.9 of width to almost equal to width. Snout with steep profile from lateral view, very short, about 0.4-0.5 of eye diameter. Unpaired horn-like tentacle at the level of nostrils on the snout midline, length of tentacle slightly shorter than diameter of eye when measured from the anterior side. Anterior nostril a tube without process on rim, posterior nostril a short tube ( Fig. 1A ). Orbit projecting forward and upper part of orbit obviously elevated above dorsal profile of the head. Interorbital narrow, about 0.2 of eye diameter. No tentacle above eye. Mouth terminal, oblique. Posterior angle of jaws behind vertical through posterior margin of eye. Upper lip wider than cheek ( Figs. 1B, 1D ), covered with a thin dermal flap, extending upwards over cheek and nearly reaching eye ( Fig. 1B ) (only in paratype SMF 35963 dermal flap shorter, Fig. 1D ). Cheek very narrow. Teeth in both jaws in a single row posteriorly, becoming 3–4 rows anteriorly, with outer row as of enlarged recurved canines, and inner rows of smaller, pointed, and irregularly spaced teeth. Branchiostegal membranes fused to isthmus, gill openings restricted to pectoral-fin base. Lower limb of first gill arch joined to gill cover by membrane. Small mental frenum, at midventral behind lower lip. No spines on preopercle. Two dorsal fins, first fin with VI spines, not elongated or filamentous, second dorsal fin I,12–13. Pectoral-fin rays count low, 13–14 (usually 13). Pectoral girdle without flaps on anterior edge. Uppermost rays of pectoral fin within membrane. Pelvic fins I,5 + 5,I, left and right fin completely separated, lacking both an anterior frenum and membrane connecting innermost rays ( Fig. 1C ); pelvic fins short, the length 0.6–0.8 of distance between origin of fins and anus. Caudal fin rounded, shorter than head length, with 17 segmented rays. Head and body completely scaleless. No head canals. Rows of head sensory papillae greatly reduced, with rows missing or reduced to one or a few papillae, and additional individual papillae present on the position of absent head canal pores. Preorbital rows r, s, s 3 each reduced to single papilla. Suborbital rows of sensory papillae with rows a and b absent; four very short transverse suborbital rows of sensory papillae (1–4) present, row 1 oblique, reaching upper lip, row 2 distant from eye, close to row d, rows 3 and 4 close to posteroventral edge of eye and distant from row d, row d short, above posterior part of upper lip and continuing shortly on cheek. Oculoscapular rows reduced to rows x 1, x 2, z, as 1 and as 2, only x 1 of more than 2 papillae ( Fig. 2 ). Head and body to below origin of the second dorsal fin densely covered with very small, irregular, black spots some within blackish background, body behind the vertical of origin of the second dorsal fin pale with sparsely scattered melanophores; head with oblique, irregular, white band behind orbit. Dorsal-fin pterygiophore insertion pattern 3-22110. Vertebrae (including urostyle) 27 (precaudal + caudal vertebrae: 10 + 17). Hypurals 1–2 and 3–4 not fused, distinctly separate along entire length. Two anal-fin pterygiophores inserted anterior to haemal arch.

Remarks. Our phylogenetic analysis ( Fig. 4 ) shows that Cerogobius is closely related to Hetereleotris , with strong support. The clade is sister to the Gobius -lineage sensu Agorreta et al. (2013). Cerogobius is morphologically clearly distinguished from Hetereleotris species and from genera in the Gobius -lineage by the combination of characters listed in the genus diagnosis. Despite high diversity and morphological variability within the Gobius -lineage, none of Gobius -lineage species have an unpaired, horn-like tentacle at snout midline, at the level of nostrils (character 1 in Cerogobius diagnosis), and none have suborbital transverse rows reduced to four rows (character 12) or lack row b (character 12) ( Miller 1986). The lower limb of first gill arch joined to gill cover by membrane (character 5) has to date not been reported for any Gobius -lineage genera except Coryogalops , which was mentioned without original data or references in Hoese (1986). Some of the diagnostic characters for Cerogobius (e.g. characters 8, 9, 10 but also others) rarely appears among species of the Gobius -lineage, but are never combined in a single species. The combination of 3-22110 dorsal-fin pterygiophore insertion pattern and 10 + 17 vertebral count in Cerogobius differentiate it from many genera in the Gobiidae , although several species of Hetereleotris , several genera in the Gobius -lineage (e.g. Didogobius , Chromogobius ) and a few other gobiid genera also possess this combination ( Hoese 1986; Birdsong et al. 1988, table 11).

Cerogobius shares several external characters with Hetereleotris that occur broadly across the Gobiidae and are less useful in diagnosing Cerogobius , and thus are not included in the present Cerogobius diagnosis, despite some being used to diagnose Hetereleotris by Kovačić & Bogorodsky (2014) and Kovačić et al. (2014a): broad isthmus and gill membrane attached to the base of the pectoral fin, first dorsal fin with VI spines, segmented caudal-fin rays 17; posterior nostril a tube of variable length (among Hetereleotris species only in H. zanzibarensis ( Smith 1958) posterior nostril subtubular). Cerogobius also shares with Hetereleotris characters that are rare in Gobiidae but not exclusive only to Hetereleotris and Cerogobius : pelvic fins completely separated and without frenum (only Hetereleotris zanzibarensis exhibits variability in this character); head and body completely scaleless (some species of Hetereleotris are scaled or partly scaled), no head canals (there are head canals in some species of Hetereleotris ) (characters 7, 8, 9, 10 in Cerogobius diagnosis respectively). At present, without new data of sufficient quality for these characters from many other Gobiidae genera, synapomorphies that are unique for Hetereleotris and Cerogobius are: lower limb of first gill arch joined to gill cover by membrane and the suborbital papillae pattern with four transverse suborbital rows (present in all Hetereleotris species with described or illustrated cephalic sensory systems, except H. georgegilli with six rows) (character 5 and the part of character 12 in Cerogobius diagnosis).

Cerogobius differs from all species presently recognized in Hetereleotris (except H. tentaculata (Smith 1958)) by the following: unpaired horn-like tentacle at the level of nostrils in the middle of snout ( Fig. 1A ) vs. no horn-like tentacle on snout in Hetereleotris ; snout with steep profile in lateral view and very short, about 0.4–0.5 of eye diameter vs. snout moderately steep and always longer than half of eye diameter in Hetereleotris ; orbit projecting forward and elevated above dorsal profile vs. orbit not projecting forward and only slightly elevated above dorsal profile in some species of Hetereleotris ; mouth moderately large, posterior angle of jaws behind vertical at posterior edge of eye vs. posterior angle of jaws below eye; caudal peduncle deep and short, the depth greater than its length vs. caudal peduncle depth clearly less than length in Hetereleotris ; suborbital rows of sensory papillae with row b absent vs. row b present in Hetereleotris ; four very short transverse suborbital rows of sensory papillae, row 2 distant from eye, close to row d, rows 3 and 4 close to posteroventral edge of eye and distant from row d vs. four transverse suborbital rows well developed over cheek, and row 3 always close and perpendicular to row d in Hetereleotris ; oculoscapular rows reduced, with only x 1 of more than 2 papillae ( Fig. 2 ) vs. more than one oculoscapular rows with several papillae in Hetereleotris (characters 1, 2, 3, 4, 6, part of 12, 13 from Cerogobius diagnosis respectively; note that only seven Hetereleotris species had available data or at least rough illustration of lateral line system).

Cerogobius is similar to H. tentaculata in the shape of head (i.e. head with very short snout, orbit far forward, and posterior angle of mouth behind a vertical at posterior edge of eye), having a scaleless head and body, and in having a short and deep caudal peduncle. It differs from H. tentaculata in having an unpaired horn-like tentacle at the level of nostrils on snout midline ( Fig. 1A ) vs. no tentacle on snout in H. tentaculata ; no cirri or tentacles above eye vs. large fleshy tentacle above each eye, 0.8 of eye diameter, with trilobate apex in H. tentaculata ; head canals absent vs. head canals present in H. tentaculata ; posterior nostril a short tube, shorter than anterior nostril vs. posterior tube elongate, much longer than anterior nostril, about half eye diameter in H. tentaculata . The two species also differ in fin meristics, morphometrics, and coloration.

Figures

FIGURE 1. Cerogobius petrophilus sp. nov.: A: head with A—unpaired horn-like tentacle at snout midline in the level of nostrils, B—anterior nostril a short tube without process from rim, C—posterior nostril a short tube (paratype, PMR VP4501, female, 15.36 + 3.21 mm); B: upper lip covered with thin dermal flap, extending upwards over cheek and nearly reaching eye (holotype, SMF 35961, female, 16.32 + 3.54 mm); C: pelvic fins completely separated and without frenum (holotype, SMF 35961, female, 16.32 + 3.54 mm). Material reversibly stained; D: upper lip just broader than cheek depth and dermal flap covering only lip (paratype, SMF 35963, female, 14.81 + 2.97 mm), in B) and D) edge of dermal flap marked with arrow. Photos by M. Kovačić.

FIGURE 2. Cerogobius petrophilus sp. nov. Cephalic sensory papillae, lateral view of paratype PMR VP4501, female, 15.36 + 3.21 mm, and dorsal view of holotype, SMF 35961, female, 16.32 + 3.54 mm. Terminology in text. Drawing by M. Kovačić.

FIGURE 3. Cerogobius petrophilus sp. nov. A: paratype, SMF 35963, female, 14.81 + 2.97 mm, freshly collected specimen, Thuwal, Saudi Arabia. Holotype, SMF 35961, female, 16.32 + 3.54 mm, Thuwal, Saudi Arabia, B: freshly collected specimen; C: preserved specimen. Photos by E.M. Troyer (A & B), M. Kovačić (C).

FIGURE 4. Bayesian inference molecular phylogeny of Gobiidae inferred from 5704 bp of combined nuclear genes and mtDNA. “Priolepis lineage” and “Gobiosomatini” refer to clades from Agorreta et al. (2013). Support values are posterior probabilities.