Ichthyophis youngorum Taylor, 1960

Geissler, Peter, Poyarkov, Nikolay A., Grismer, Lee, Nguyen, Truong Q., An, Hang T., Neang, Thy, Kupfer, Alexander, Ziegler, Thomas, Böhme, Wolfgang & Müller, Hendrik, 2015, New Ichthyophis species from Indochina (Gymnophiona, Ichthyophiidae): 1. The unstriped forms with descriptions of three new species and the redescriptions of I. acuminatus Taylor, 1960, I. youngorum Taylor, 1960 and I. laosensis Taylor, 1969, Organisms Diversity & Evolution (New York, N. Y.) 15 (1), pp. 143-174 : 166-168

Ichthyophis youngorum Taylor, 1960

Holotype A metamorphosed male ( FMNH 189250 , Fig. 14 ) collected 12 July 1957 at Doi Suthep, Chiang Mai Province, Thailand, by E.H. Taylor at approximately 1200 m asl ( Taylor 1960).

Paratypes FMNH 189251 , (adult male collected by E.H. Taylor at the type locality). Taylor (1960, 1967) mentioned eight additional topotypic larval paratypes. The specific identity of these specimens remains unclear (see also distributional remarks below) .

Diagnosis A species of Ichthyophis without a lateral yellow stripe; total length of metamorphosed specimens 208–217 mm, length about 19–21 times of midbody width; snout blunt and rounded (SP/HL=0.01); TN/ ET =2.5; premaxillary and maxillary teeth 28, vomeropalatine teeth 40, dentary teeth more than 28, inner mandibular teeth more than 18; total annuli (dorsal count) 318–328, encircling body by forming an angle pointing towards tail on anterior three quarters of venter, five to six annuli interrupted by cloacal disc, four tail annuli posterior to the cloacal disc; cloacal disc rounded; 108 vertebrae (excluding the larval paratype FMNH 189252 , which has 104 vertebrae); scales in one to two rows per annulus (dosolaterally), present only in the posterior third of body .

The species differs from all other known unstriped congeners in the following characters: from I. acuminatus by one to two instead of four rows of scales per scale pocket and by fewer premaxillary and maxillary teeth (22–28 vs. 35–43); from I. billitonensis in having more inner mandibular teeth (18–19 vs. 2); from I. bombayensis by the absence of scales on the anterior third of body; from I. cardamomensis sp. nov. by fewer vertebrae (108 vs. 120); from I. catlocensis sp. nov. by the tentacle being closer to the to naris ( TN / ET =2.5 vs. 4.5); from I. chaloensis sp. nov. in a shorter snout (SP/HL=0.01 vs. 0.14); from I. dulitensis by the absence of scales on the anterior two third of body; from I. glandulosus by more annuli (318–328 vs. 273–286); from I. javanicus in having fewer annuli (318–328 vs. 348–351); from I. lakimi by more inner mandibular teeth (18 vs. 14); from I. laosensis by the absence of scales on the anterior two thirds of body; from I. larutensis by the the presence of inner mandibular teeth; from I. monochrous by the absence of scales on the anterior two thirds of body and a higher count of annuli (318–328 vs. 247); from I. orthoplicatus by more annuli (318–328 vs. 205–291); from I. sikkimenis by more annuli (318–328 vs. 276–292); from I. singaporensis by the absence of scales on the anterior two thirds of body; from I. sumatranus by the absence of scales on the anterior two thirds of body; and from I. weberi by the presence of inner mandibular teeth.

Description of holotype Selected morphological and meristic data are given in Table 4. Condition of the preserved specimen: jaws deeply cut on right side, with cut extending through collars and first five annuli; gums and tooth rows partially damaged; and ventrolateral incision (12 mm) extends from about 60 mm anterior of vent disc

Head (see Fig. 14 ) flattened dorsoventrally; in dorsal view, head narrows slightly between first collar and corner of mouth, anterior to corner of mouth, outline of head forms a bluntly rounded parabolic curve; snout bluntly rounded; in lateral view, top of head nearly flat, beginning to abruptly curve downwards just anterior of nares; lower jaw more tapering between collar region and tip of lower jaw; nares very close to tip of snout; snout dropping almost vertically anterior to nares; lips straight edged; corner of mouth somewhat closer to bottom of head than to top of head; mouth terminal, snout barely projecting; in ventral view, gular region slightly depressed, with a deep median groove, starting at level of tentacles, continuing halfway onto second collar; eyes visible through unpigmented skin, rounded, lens forming a dark-grey central disc, not elevated above adjacent skin; in lateral view eyes equidistant between top of head and upper lip; tentacular aperture nearly twice as far from naris than from eye, almost same size as naris; distance from upper lip about the diameter of tentacular aperture; tentacular sheaths elevated from adjacent skin, visible only in dorsal view; in preservative, tentacles not protruding from tentacular aperture; nares oval in shape, about equidistant between top of head and upper lip, barely visible in dorsal view, not visible in ventral view; teeth recurved and bicuspid, with relatively widely spaced accessory cusp; 28 premaxillary-maxillary, 33 vomeropalatine, 28 dentary, and 19 inner mandibular teeth (tooth counts for vomeropalatine, dentary, and inner mandibular series incomplete due to damage); both collars wider and deeper than head; second collar gradually narrowing towards trunk; collar grooves only distinct ventrally and laterally, vanishing dorsally; one dorsal transverse groove on second collar; in ventral view, anterior as well as posterior border of collars distinct; second collar slightly longer than first; anteriormost eight annuli ventrally narrowly incomplete; following grooves encircle venter by forming an angle pointing towards tail on anterior three quarters of body; annuli on last quarter cross venter in a straight line; total annuli 318; vertebrae 108; longitudinal cloacal slit situated in a round cloacal disc, interrupting five annuli; cloaca surrounded by irregular denticulations; tail bearing four annuli (including cap), grooves not complete ventrally, terminating in a small terminal cap; scales present in one to two rows per scale pocket (counted dorsolaterally) in the posterior third of the body; and scales oval in shape.

Coloration Presumably somewhat faded in preservative (see Fig. 14 ) and now dark brown on dorsum and somewhat lighter ventrally; cloacal disc and tail cap light colored; and naris and tentacular aperture with narrow light colored margins. Overall color presumably darker in life.

Variation Selected morphological and meristic data are given in Table 4. Paratype FMNH 189251 has a higher number of annuli (328) and slightly different tooth counts (see Table 4). However, it resembles the holotype in several characteristic features: number of vertebrae (both 108); TN/ ET =2.5; SP/HL=0.01; the absence of scales on the anterior two thirds of body .

Differences from the description by Taylor (1960) The following characters measured or counted by us deviate from the data provided by Taylor (1960) (marked with an asterisk): holotype: HW=7.6 vs. 9*; ET =1.1 vs. 1.3*; TN=2.7 vs. 2.6*; EN=3.8 vs. 3.5*; TAL= 208 mm vs. 210 mm *; TAD=318 vs. 324*; PMM=28 vs. 43*; VP=33 vs. 43*; DE=28 vs. 40*; IM =19 vs. 24*. The paratypes resemble Taylor’ s descriptions except the vertebrae counts, 108 vs. 106–107*.

Distribution The species is only known from its type locality in the Doi Suthep (see above) and Doi Ankang mountain located in Chiang Mai Province, northern Thailand (Chan-ard 2003). See Fig. 1. The collections of the Field Museum contain two specimens from the collection of E. H. Taylor that are catalogued as I. youngorum . These were collected by Taylor at “Ronpibon” (Ron Phibun), Nakhon Si Thammarat Province of southern Thailand, far away from the type locality in northern Thailand. Both specimens are small larvae (78 and 83 mm TL) and appear unstriped. Where known, stripe development in larvae of striped Ichthyophis occurs at larger sizes ( Kupfer et al. 2005), and it is therefore impossible to determine with any certainty the specific identity of these specimens (as long as formalin fixation hinders molecular approaches). Taylor collected specimens of I. supachaii at Ron Phibun ( Kupfer and Müller 2004) and the attribution of the two larvae to I. youngorum cannot currently be verified and seems mistaken.

Conservation status The species has not been recorded again since the collection of the type series in 1957. At present, I. youngorum is listed as data deficient by the IUCN ( van Dijk et al. 2004c) and further research is urgently needed to specify the actual distribution area in Thailand as well as the population size of I. youngorum .

Figures

Fig. 14 Holotype (FMNH 189250) of Ichthyophis youngorum in preservative (TL, 208.0 mm). Photographs by Harry Taylor