Glaridoglanis ramosa, Ng & Kottelat, 2022

Ng, Heok Hee & Kottelat, Maurice, 2022, A New Glyptosternine Catfish from Myanmar (Actinopterygii: Siluriformes: Sisoridae), Ichthyology & Herpetology 110 (2), pp. 262-267 : 262-266

Glaridoglanis ramosa , new species

urn:lsid:zoobank.org:act:03C1B59A-D586-45A9-9117- 0726DE94F8F7

Figure 1

Holotype.— MHNG 2786.064 , 104.3 mm SL, Myanmar, Shan State , Ywangan Township ( Danu Autonomous Zone ), Sin Lal Chaung , small stream in limestone area about 14 km E of Ywangan, 21811 0 23 00 N, 96833 0 18 00 E, about 1190 masl, Nyein Chan and Aung Lin, 5 March 2019.

Paratypes.— CMK 28568 , 3, 36.4–60.6 mm SL, ZRC 62092, 1, 41.1 mm SL, data as for holotype.

Diagnosis.— Glaridoglanis ramosa is distinguished from G. andersonii in having fewer vertebrae (39–40 vs. 42–44), more branched pectoral-fin rays (13–14 vs. 8–10), a longer maxillary barbel (reaching beyond proximal half vs. not more than proximal third of first pectoral-fin element; 87–101% HL vs. 75–79), a shorter pelvic fin (10.8–16.3% SL vs. 18.0–22.4) and dorsal-to-adipose distance (7.1–11.7% SL vs. 17.5–20.0), absence (vs. presence) of a thin, pale midlateral stripe, and an adipose fin that is strongly incised (vs. without incision or with a weak incision) at the posterior extremity of its base.

Description.— Morphometric data as in Table 1 . Head and body very strongly depressed, with paired fins greatly enlarged to form elongate ovoid adhesive disc with body. Rostral margin rounded in dorsal view, moderately curved in lateral view. Dorsal profile rising gently and evenly from anterior orbital margin to origin of dorsal fin, then sloping gently ventrally to end of caudal peduncle. Ventral profile flat to anal-fin base, then sloping gently dorsally to end of caudal peduncle. Anus and urogenital openings located just before posterior margin of adpressed pelvic fin.

Head broad, approximately as wide as long. Mouth inferior, with gape width approximately half that of head and densely papillate lips. Premaxillary tooth patch with

1 c/o Lee Kong Chian Natural History Museum, 2 Conservatory Drive, Singapore 117377; Email: (HHN) [e-mail]. Send reprint requests to HHN. 2 Rue des Rauraques 6, 2800 Delémont, Switzerland; Email: [e-mail]. Submitted: 13 May 2021. Accepted: 6 October 2021. Associate Editor: R. E. Reis. 2022 by the American Society of Ichthyologists and Herpetologists DOI: 10.1643/i2021056 Published online: 10 May 2022

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anterior margin exposed when mouth is closed. Lower lip with prominent labial fold joined to base of maxillary barbel. Postlabial groove on lower jaw interrupted, ending at base of inner mandibular barbel. Jaw teeth embedded in skin, distally flattened, and oar-shaped. Teeth in single crescentic band on upper jaw and in two well-separated, roughly triangular patches on lower jaw. Palate edentulous. Eye small, dorsolaterally situated, subcutaneous. Gill opening narrow, extending from base of first pectoral-fin ray to level immediately dorsal to base of posteriormost pectoral-fin ray.

Barbels in four pairs. Nasal barbel long, reaching beyond posterior orbital margin. Maxillary barbel flattened, with flap of skin fringing posterior margin of distal half; its tip pointed; ventral surface with numerous striae; extending beyond base of first pectoral-fin ray. Inner mandibular barbel slightly flattened, short. Outer mandibular barbel situated lateral to inner mandibular barbel; slightly flattened, reaching to base of first pectoral-fin ray.

Dorsal fin without spine, with i,5 (5) rays; surfaces of fin rays covered with small tubercles. Adipose fin with long base;

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anterior extremity at approximately midway between bases of pelvic and anal fins, posterior extremity separate from upper procurrent caudal-fin rays and distinctly incised. Anal fin with ii,4 (5) rays, surfaces of fin rays covered with small tubercles. Caudal fin truncate or gently rounded, with i,7,6,i* (1) or i,7,7,i (4) rays; surfaces of fin rays covered with small tubercles. Pelvic fin greatly enlarged, with convex distal margin and i,5 (5) rays; first ray greatly flattened, with numerous striae on ventral surface; dorsal surfaces of fin rays covered with small tubercles. Pectoral fin greatly enlarged, without spine and with i,13,i (1) or i,14,i* (4) rays; first ray greatly flattened, with numerous striae on ventral surface. Dorsal surface of pectoral-fin rays covered with small tubercles. Vertebrae 26þ13¼39* (1), 27þ12¼39 (1), 27þ13¼40 (2), or 29þ11¼40 (1).

Coloration.— In 70% ethanol: medium brown on dorsal and lateral surfaces of head and dorsal surface of body, dark yellow on ventral region. Dorsal, anal, and caudal fins brown; dorsal surfaces of pectoral and pelvic fins brown, with ventral surfaces of pectoral and pelvic fins dark yellow. Dorsal surface of nasal and maxillary barbels brown, ventral surface dark yellow. Mandibular barbels dark yellow.

Distribution and habitat.— Glaridoglanis ramosa is known from a single locality in a cryptorheic basin in Shan State in Myanmar ( Fig. 2 ). It was collected in Sin Lal Chaung (21811 0 23 00 N, 96833 0 18 00 E; Fig. 3A ), a small stream that disappears in Yae Win cave (21811 0 27 00 N, 96833 0 12 00 E; Fig. 3B ). The outflow of the Sin Lal Chaung from the cave is not known, although it is locally believed that it flows to Zawgyi Chaung, but no precise area could be suggested. The Zawgyi

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Chaung occupies the watershed north of the karst massive; it is a tributary of Myitnge Chaung, which enters the Ayeyarwaddy (Irrawaddy) River near Mandalay.

At the collecting site and time (dry season), the Sin Lal Chaung was a clear water stream, about 5 m wide and 0.3–1.0 m deep, flowing over a substrate of sand, gravel, and stones, and occasional stretches with quieter water and silty sand. The vegetation of the surrounding area comprises scattered forest and home gardens. The fish were observed upstream of the entrance of Yae Win cave and inside the cave including in total darkness. Lepidocephalichthys berdmorei and Devario sp. were the only other fish species collected at this locality.

Etymology.— The specific epithet comes from the Latin adjective ramosus, -a, -um, which means having many branches. This is used in allusion to the higher number of branched pectoral-fin rays in this species compared to its sole congener ( G. andersonii ). As Glaridoglanis is feminine (fide Kottelat, 2013), the specific epithet is declined accordingly.

DISCUSSION

Day (1870) described Exostoma andersonii from four specimens collected from Yunnan, China: two from Hotham (¼Husaxiang, 24828 0 09 00 N, 97853 0 54 00 E) and two from Ponsee (approx. 24828 0 N, 97842 0 E). Both localities are in the Irrawaddy drainage; see Anderson (1876) for travel itinerary and maps. Anderson (1879: 866) explicitly mentioned that he collected only four specimens, on which Day based his description. The four syntypes were deposited in the Zoological Survey of India in Kolkata, India (ZSI), where Hora (1923: 37) examined them. He reported that ‘‘two of them are desiccated and have fallen into pieces; the remaining two are in a better condition.’’ In a revision of ‘‘glyptosternoid fishes,’’ Hora and Silas (1952: 22) mention ZSI F9173/1 (1) and 9174/1 (1), both desiccated and one with head separated from body, and comment that the two remaining specimens (ZSI 596) have been lost, apparently in the 1943 flood that destroyed part of the museum’s collection ( Chopra, 1946).

In a catalog of fish type-specimens in ZSI, Menon and Yazdani (1968: 127) mention two specimens and give three catalog numbers ‘‘F 9173/1; F 9174/1 & A.S.B. Cat. No. 596’’ (ASB refers to the Asiatic Society of Bengal, whose collection formed the nucleus of ZSI collection). In a catalog of the Day fish collections, Whitehead and Talwar (1976: 157) mention that two specimens (A.595) were present in ZSI and two specimens (A.596) were lost or destroyed. Some of the specimens in the Day collection had been given to AMS (Australian Museum, Sydney) in 1884 by Day himself; among them, AMS B.8081, 127 mm SL, labeled from

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‘‘Bhamo, China’’ was treated as a possible syntype by Ferraris et al. (2000: 294). However, since there were only four syntypes and Hora had examined all in 1923 in ZSI, the AMS specimen cannot be a syntype.

We were unable to examine the ZSI syntypes, but were able to examine photographs and radiographs of the AMS specimen. A comparison with the data given in Day (1870) and Hora (1923) indicates that the syntypes of G. andersonii , the AMS specimen, and specimens from northern Myanmar (all collected within 200 km of both type localities of G. andersonii ) we have examined all share 9–10 branched pectoral-fin rays and an adipose fin with at most a weak incision at the posterior extremity of its base. Based on this information, we conclude that all of these specimens are conspecific.

Glyptosternon malaisei has been considered a valid species of Glyptosternon in recent checklists ( Ferraris, 2007; Kottelat, 2013), and its taxonomic status has not been discussed in recent studies on Glyptosternon (e.g., Thoni et al., 2017). We have examined the holotype and reidentify it as a species of Glaridoglanis , on the basis of the spatulate, homodont dentition (vs. conical, homodont dentition in Glyptosternon ) on both jaws and the premaxillary tooth patch not extending (vs. extending in Glyptosternon ) posterolaterally. Rendahl and Vestergren (1941) only compared G. malaisei with G. maculatum and G. reticulatum , distinguishing G. malaisei from them by the morphology of the adipose fin, coloration, and differences in the relative sizes of the eye and pectoral fin. Our studies fail to find any significant differences in morphology and morphometry between the holotype of G. malaisei ( Fig. 4A ) and fresh material identified as Glaridoglanis andersonii collected from northern Myanmar (CMK 26593; Fig. 4B ). We therefore consider Glyptosternon malaisei to be a junior subjective synonym of Glaridoglanis andersonii .

One of the characters previously used to diagnose Glaridoglanis from other glyptosternines is the presence of 8–10 branched pectoral-fin rays ( Ng, 2015), which is lower than that reported in many other genera (11–16 in Chimarrichthys , 14–16 in Creteuchiloglanis , 17–20 in Oreoglanis , 16–17 in Parachiloglanis , 13–16 in Pareuchiloglanis , and 16–18 in Pseudexostoma ). The discovery of G. ramosa renders the number of branched pectoral-fin rays (now 8–14) less useful as a diagnostic character for the genus, now distinguishing Glaridoglanis only from Oreoglanis , Parachiloglanis , and Pseudexostoma in this regard.

Figures

FIG. 1. Glaridoglanis ramosa, holotype, MHNG 2786.064, 104.3 mm SL. Dorsal, lateral, and ventral views (first pectoral-fin element on left damaged).

FIG. 2. Irrawaddy River basin showing type locality of Glaridoglanis ramosa.

FIG. 3. Type locality of Glaridoglanis ramosa: (A) Sin Lal Chaung, about 300 m upstream of cave entrance; (B) Sin Lal Chaung at entrance of Yae Win cave. Photographs courtesy of Nyein Chan.

FIG. 4. Lateral views of Glaridoglanis andersonii: (A) NRM 10721, holotype of Glyptosternon malaisei, 70.4 mm SL; (B) CMK 26593, 127.6 mm SL. Images not to scale. Figure 4A courtesy of NRM.

Tables

Table 1. Morphometric data for Glaridoglanis ramosa (n ¼ 5).

	Holotype	Range	Mean 6 SD
Standard length (mm)	104.3	36.1–104.3
Percent of standard length
Predorsal length	30.2	30.2–34.8	32.962.42
Preanal length	72.0	70.0–74.0	73.361.13
Prepelvic length	37.9	37.9–43.1	40.562.60
Prepectoral length	13.8	13.8–16.1	15.061.16
Length of dorsal-fin base	10.0	10.0–12.7	11.561.39
Length of anal-fin base	7.3	7.3–9.2	8.360.95
Pelvic-fin length	10.8	10.8–16.3	13.362.78
Pectoral-fin length	20.1	20.1–22.4	21.561.21
Caudal-fin length	13.6	13.6–16.3	14.561.53
Length of adipose-fin base	40.2	38.4–40.2	39.661.01
Dorsal-to-adipose distance	11.7	7.1–11.7	9.062.30
Post-adipose distance	11.0	9.9–11.0	10.460.57
Length of caudal peduncle	17.4	16.0–17.4	16.760.70
Depth of caudal peduncle	7.9	7.9–8.9	8.460.50
Body depth at anus	9.9	9.9–13.1	11.561.60
Pectoral–pelvic distance	26.7	26.7–27.0	26.860.17
Head length	21.0	21.0–25.6	23.562.33
Head width	18.2	18.2–19.8	19.160.81
Head depth	8.5	8.5–10.9	9.761.20
Percent of head length
Snout length	48	48–57	5165.2
Interorbital distance	23	23–31	2864.2
Eye diameter	7	7–11	962.1
Nasal barbel length	52	36–52	4568.3
Maxillary barbel length	101	87–101	9367.1
Inner mandibular barbel	26	21–26	2362.5
length
Outer mandibular barbel	49	32–49	4068.5
length

Table 1. Morphometric data for Glaridoglanis ramosa (n ¼ 5).