Homalopterula Fowler 1940

Randall, Zachary S. & Page, Lawrence M., 2015, On the paraphyly of Homaloptera (Teleostei: Balitoridae) and description of a new genus of hillstream loaches from the Western Ghats of India, Zootaxa 3926 (1), pp. 57-86 : 71-72

Homalopterula Fowler 1940

( Figures 3 C, 4E, 5C, 9)

Homalopterula Fowler, 1940:379 (type species: Homaloptera ripleyi Fowler 1940:379 ) by original designation. Gender feminine.

Remarks. Homalopterula was created for the new species Homalopterula ripleyi Fowler 1940 and distinguished from other balitorids by the “peculiar shape of its jaws, in combination with its truncated caudal and entirely naked medial under surface of the abdomen” ( Fowler 1940:379). Homalopterula was treated as a junior synonym of Homaloptera based on the illustration provided in Fowler’s type description and the variation that “exists regarding the nature of the caudal and presence or absence of scales on the ventral surface of the abdomen in species of Homaloptera ” by Silas (1953). This decision was followed by Roberts (1989).

Kottelat (1998) recognized Homaloptera gymnogaster Bleeker 1853 , H. heterolepis Weber & de Beaufort 1916, H. ripleyi ( Fowler 1940) , and H. vanderbilti Fowler 1940 as possibly forming a clade ( Homalopterula ) based on having “a more cylindrical body, a relatively wide mouth, short paired fins, and a truncated or slightly emarginated caudal fin.” Based on this description, Tan & Ng (2005) and Ott (2009) treated Homalopterula as a subgenus of Homaloptera . Randall & Page (2012) recognized Homalopterula as a subgenus based on “mouth morphology, dorsal-fin origin over pelvic fin, ≥ 60 lateral-line scales, and ≥ 30 predorsal scales.” They did not include H. modiglianii , then recognized as a junior synonym of H. gymnogaster ( Kottelat 1993) . Including it in this study following Kottelat (2012, 2013) changes the lateral-line and predorsal scale count range found in Homalopterula to 57–75 and 28–56, respectively.

Diagnosis. Distinguishing characters are given in Table 4 and shown in Figures 3 C, 4E, 5C and 9. Homalopterula is distinguished by the following combination of characters: without reddish tints on fins in life ( Fig. 3 C); dorsal-fin origin posterior to pelvic-fin origin; 5½ and 7½, 7½ (M) branched dorsal-fin rays; 7 pelvic-fin rays; truncated or emarginated caudal fin; smooth scales ( Fig. 4 E), 57–75 total lateral-line scales, 28–56 predorsal scales; anus closer to anal-fin origin than to pelvic-fin base; adipose keel on caudal peduncle; small rostral cap; 2 thick and widely separated rostral barbels; thick crescentic upper lip; 2 fleshy lobes between lateral portions of lower lip ( Fig. 5 C); and presence of a central furrow at the isthmus.

Species included. Homalopterula gymnogaster (Bleeker 1853) , H. modiglianii (Perugia 1893) , H. amphisquamata (Weber & Beaufort 1916) , H. heterolepis (Weber & de Beaufort 1916), H. ripleyi Fowler 1940 , and H. vanderbilti ( Fowler 1940) . The type localities for species of Homalopterula are shown in Figure 10 .

Comparison. Homalopterula is distinguished from Homaloptera by absence vs. presence of reddish tints on fins in life; dorsal-fin origin posterior vs. anterior to pelvic-fin origin; 5½ and 7½, 7½ (M) vs. 7–8½, 8½ (M) branched dorsal-fin rays; 28–56 vs. 20–27 predorsal scales; smooth vs. keeled scales; truncated or emarginated vs. forked caudal fin; presence vs. absence of adipose keel on caudal peduncle; small vs. large rostral cap; medial- and lateral-rostral barbels widely separated from one another at base vs. barbels in close proximity to one another; crescentic rather than triangular upper lip; presence vs. absence of a central furrow at the isthmus; fleshy lobes vs. pad between lateral portions of lower lip.

Homalopterula is distinguished from Homalopteroides by having truncated or emarginated vs. forked caudal fin; smooth vs. wart-like/keeled scales; 28–56 vs. 14–25 predorsal scales; 57–75 vs. 33–52 total lateral-line scales; presence vs. absence of adipose keel on caudal peduncle; thick vs. thin lips; presence vs. absence of fleshy lobes between lateral portions of lower lip.

Homalopterula is distinguished from Balitoropsis and Pseudohomaloptera by having dorsal-fin origin posterior vs. anterior to or above pelvic-fin origin; 5½ and 7½, 7½ (M) vs. 8½ branched dorsal-fin rays; 7 vs. 7–9, 8 (M) branched pelvic-fin rays; truncated or emarginated vs. forked caudal fin; smooth vs. keeled scales; 28–56 vs. 13–15 and 13–19 predorsal scales, respectively; presence vs. absence of adipose keel on caudal peduncle; small vs. large rostral cap; medial- and lateral-rostral barbels widely separated from one another at the base vs. barbels in close proximity to one another; presence of fleshy lobes vs. pad between lateral portions of lower lip. It is further distinguished from Balitoropsis by having the anus closer to anal-fin origin than to pelvic-fin insertion and 57–75 vs. 42–55 lateral-line scales.

Material examined. Homalopterula gymnogaster : Sumatra: BMNH 1866.5.2.49 (holotype of Homaloptera gymnogaster ); ZMA 100256 (syntypes of Homaloptera lepidogaster ) (3); UF 185031 (1). H. modiglianii : Sumatra: BMNH 1931.10.29.1-2 (syntypes of Homaloptera modiglianii ) (2). H. amphisquamata : Sumatra: ZMA. 100.998 (syntype of Homaloptera amphisquamata ), 100.994 (syntypes of Homaloptera amphisquamata ) (2). H. heterolepis : ZMA 100.999 (syntypes of Homaloptera heterolepis ) (3). H. ripleyi : Sumatra: ANSP 68713 (holotype), 187003 (2), 187004 (1), 188907 (1), 188908 (4). H. vanderbilti : Sumatra: ANSP 68688 (holotype of Homaloptera vanderbilti ), 68700 (Holotype of Homaloptera ulmeri ).

Figures

FIGURE 3. Lateral views of living (A) Homaloptera orthogoniata, not cataloged, Kalimantan, Borneo, Indonesia. Strong reddish tints on body likely breeding colors; (B) Homalopteroides smithi, UF 235740, 45.0 mm SL, Khlong Tasae, Salui Subdistrict, Chumphon, Thailand; (C) Homalopterula cf. ripleyi, not cataloged, Sumatra, Indonesia; (D) Balitoropsis zollingeri, not cataloged, Kalimantan, Borneo, Indonesia; (E) Pseudohomaloptera leonardi, UF 235735, 34.2 mm SL, Ta Pi River, Nakhon Si Thammarat, Thailand. Photos (A) & (D) by Renny Hadiaty. Photo (C) by Daniel Lumbantobing. Specimens not to scale.

FIGURE 4. Scale sizes and keel patterns of predorsal region: Large, and keeled scales, (A) Balitoropsis zollingeri, UF 166094, 52.1 mm SL; (B) Pseudohomaloptera tatereganii, RMNH 7632 (holotype), 64.6 mm SL. Large, and wart-like / keeled scales (C) Homalopteroides wassinkii, UF 183330, 43.6 mm SL. Medium, and keeled scales, (D) Homaloptera cf. ocellata, UF 161718, 64.1 mm SL. Small, and smooth scales, (E) Homalopterula ripleyi, ANSP 188908, 43.1 mm SL; (F) Ghatsa montana, CAS-SU 39871 (holotype), 46.6 mm SL. Scale bar represents 1 mm. Left side of photo is anterior.

FIGURE 5. Oral morphology of (A) Homaloptera cf. ocellata, UF 161718, 64.1 mm SL; (B) Homalopteroides wassinkii, UMMZ 155660, 46.2 mm SL; (C) Homalopterula ripleyi, ANSP 188908, 43.1 mm SL; (D) Balitoropsis zollingeri, UF 166094, 52.1 mm SL; (E) Pseudohomaloptera tatereganii, RMNH 7632 (holotype), 64.6 mm SL; (F) Ghatsa montana, (holotype) CAS- SU 39871, 46.4 mm SL. Abbreviations: CF, central furrow; FL, fleshy lobe; FP, fleshy pad; LJ, lower jaw; LL, lower lip; LRB, lateral-rostral barbel; MB, maxillary barbel; MRB, medial-rostral barbel; RC, rostral cap; UJ, upper jaw; UL, upper lip.

FIGURE 10. Type localities for species of Homalopterula. Asterisk represents the type species of the genus.