Phalotris labiomaculatus Lema, 2002

Hamdan, Breno, Jr, Nelson Jorge Da Silva, Silva, Helder Lucio Rodrigues, Cintra, Carlos Eduardo D. & Lema, Thales De, 2013, Redescription of Phalotris labiomaculatus (Serpentes, Dipsadidae, Elapomorphini), with notes on the taxonomic boundaries within the nasutus group, Zootaxa 3693 (2), pp. 182-188 : 184-185

Phalotris labiomaculatus Lema, 2002

Type-locality. Municipality of Porto Franco, state of Maranhão, Brazil.

Emended diagnosis. Phalotris labiomaculatus is distinguished from all congeners by the combination of the following characters: 15/15/15 smooth dorsal scale rows without apical pits and undifferentiated vertebral row; loreal absent; preocular single and long; two postoculars; temporal formula 1+1 (0+ 1 in one specimen not preserved in scientific collection); six supralabials; second and third contacting orbit; eight infralabials; first four contacting anterior chin-shields; 220–234 (x =225,7; s=3,9; n=14) ventrals in females, 198–211 (x =204,6; s=3,5; n=15) in males; 25–31 subcaudals in females (x =27,5; s=1,6; n=14), 34–42 (x =38,2; s=1,8; n=15) in males; cloacal plate always divided; subcaudals in paired rows (divided) throughout the tail; a very thick head and trunk as the other species of the group; tail slendering gradually towards extremity with a sharp tip; total length of smallest and largest specimen 274.05 mm and 754 mm (both female); snout-vent length; caudal length and head length range from 255–640 mm, 19.05–46.53 mm 9.12–12.64 mm in females (n=14) and from 290–610 mm, 31.96–74.66 mm and 10.16– 14 mm in males (n=15), respectively; orbit diameter ranges from 0.79 to 1.88 mm being smaller than its distance to oral border; head black above; suture region between nasal plate, preocular plate and the first and second supralabials somewhat pale ( Figure 1 F), supralabial plates white and black blotched as well as the outer margins of infralabials, synfisial and mentals (more evident in young); white nuchal ring (n=28) sometimes reddish (n=1; Figure 1 B) extending over 3–4 scale lengths, followed by a narrower black cervical ring with 1–2 scale lengths (rarely 3, n=1); background color bright red, with a linear series of black dots on each side, becoming a stripe on the tail, more evident in young and almost indistinct in the largest specimens; immaculate white venter ( Figure 1 ).

Comparisons between P. labiomaculatus and the other species of the nasutus group: The nasutus group contains the following species: Phalotris concolor Ferrarezzi, 1993 , P. labiomaculatus Lema, 2002 , P. lativittatus Ferrarezzi, 1993 , P. nasutus Gomes, 1915 , and P. nigrilatus Ferrrezzi, 1993 . Among all its congeners of the nasutus group, Phalotris labiomaculatus can be promptly distinguished from all species by the presence of supralabial plates white and black blotched as well as the outer margins of infralabials, synfisial and mentals. Additionally the species differs anatomically from P. nigrilatus in having a dorsal red coloration, an homogeneously white belly, nuchal collar present, lateral dark bands absent and head not homogeneously blackish whereas a dorsal coloration blackish, belly with lateral black spots, nuchal collar absent, lateral dark bands present and blackish head can be found in P. nigrilatus (Ferrarezzi 1993; Cacciali et al. 2007); from P. n a s u t u s in having higher number of ventral scales 220–234 in females and 198–211 in males whereas P. nasutus has 189–198 in females and 175–179 in males (Lema 1999; Lema et al. 2005; Cacciali et al. 2007; Ferrarezzi 1993); from P. lativittatus by the presence of dorsal pattern color red homogeneous and an homogeneously white belly whereas P. lativittatus holds a dorsal pattern color brownish or reddish brown with a wide lateral dark stripe and belly yellowish irregularly in median line (Cacciali et al. 2007; Vasconcelos & Santos 2009; Ferrarezzi 1993). The number of ventral scales can also help distinguish P. labiomaculatus (220– 234 females, 198– 211 males) from P. lativittatus (196– 208 females; 182– 199 males) since they overlap only by about three scales in males. Besides, P. lativittatus can often show a vertebral stripe (Cacciali et al. 2007; Ferrarezzi 1993) whilst no specimen analyzed of P. labiomaculatus had the stripe. Finally P. labiomaculatus can be distinguished from P. concolor in having supralabial plates white and black blotched while the latter holds labial plates cream (Ferrarezzi 1993; Cacciali et al. 2007).

Sexual dimorphism: There are no differences in color pattern between males and female, but Phalotris labiomaculatus showed significant sexual dimorphism in segmental counts and biometric data. Females have a significantly higher number of ventral scales (F1,27= 234,2; p<0,001) and fewer subcaudals than males (F1,27= 287,4; p<0,001). Furthermore, at the same SVL, males have a longer tail with 10–14% of SVL whereas in females is about 7–8% of SVL (U -4,5=0; p<0,001; n=29).

Intraspecific variation. Some individuals can show the dorsolateral dark dots, becoming continuous in a line on the tail, as well as black dots on the synfisial, mentals, and inflalabials, much more evident. Larger specimens do not present evident black blotched infralabials and in general it seems that the dorsolateral line tends to fade as the specimens get older.

Coloration in preservative. In 70% ethanol Phalotris labiomaculatus has a light brown coloration on the dorsum and a darkish white belly. The first ring on the neck is light cream (n=28) or brown (n=1) fallowed by a second narrower blackish ring. Dorsum of the head predominantly black or grey faded; supralabials, infralabials, and gular scales blackish and yellowish blotched; suture region between nasal plate, preocular plate and the first and second supralabials yellowish or cream. Dorsolateral dark dots somewhat faded; less noticeable in old specimens in which sometimes are difficult to see. Some regions dorsally may present interspaces bearing blackish pigmentation in the posterior edge of scales.

Distribution. Phalotris labiomaculatus inhabits savanna environments in altitudes between 100–200m asl and has the northernmost distribution range of the genus Phalotris , known from the Brazilian states of Maranhão and Tocantins, along the Tocantins River ( Figure 2 ).

Figures

FIGURE 1. General view of Phalotris labiomaculatus. A. Adult; B. Adult with reddish nuchal ring; C. Juvenile; D. Young; E. Right lateral view of head; F. Ventral view of head.

FIGURE 2. Geographic distribution map of Phalotris labiomaculatus in Brazil. Triangle corresponds to the Type locality (Lema 2002), square to the other previous record (França et al. 2005) and circles correspond to the new localities reported herein: 1 = Filadelfia; 2 = Carolina; 3 = Darcinópolis; 4 = Estreito; 5 = Palmeiras do Tocantins. States code: MA = Maranhão; TO = Tocantins.