Synophis plectovertebralis Sheil & Grant, 2001

Pyron, R. Alexander, Arteaga, Alejandro, Echevarría, Lourdes Y. & Torres-Carvajal, Omar, 2016, A revision and key for the tribe Diaphorolepidini (Serpentes: Dipsadidae) and checklist for the genus Synophis, Zootaxa 4171 (2), pp. 293-320 : 308-309

9. Synophis plectovertebralis Sheil & Grant, 2001

Range. Pacific Andean slopes of Valle del Cauca, Colombia, ~ 1800m.

Description. Adult size ~ 200–210mm SVL and ~ 80–100mm TL, smooth nuchal scales; nuchal collar; intranasals in contact; 1 postocular; 7–8 infralabials; 7–8 supralabials; 144–147 ventrals; 79–91 subcaudals; and 19-19-19 dorsal scale-rows at midbody, with single, weak keel.

Notes. Known only from the holotype and paratype. Not included in our phylogenetic analyses ( Fig. 1 ); its placement is thus unknown.

With this re-assessment of species boundaries and taxonomic reassignment of nearly all known specimens of Synophis ( Figs. 1–4 , Tables 1,2), the morphological limits and geographic ranges of the known, extant species are tentatively stabilized. There are likely additional cryptic species in some taxa (e.g., S. lasallei ), and there are almost certainly additional new species to be discovered. Our results here should clarify lingering confusion over most species limits, and provide a robust basis for future work.

The known species can be informally grouped into at least three species groups. The first is the S. bicolor group ( S. bicolor , S. niceforomariae ), distributed in the northern Andes, with higher ventral and subcaudal counts (174–193 and 127–143), weak keels, more slender bodies and lighter colorations ( Figs. 2 , 3 ; see Fig. 4 in Pyron et al. 2015). The second is the S. calamitus group ( S. zaheri , S. calamitus ), distributed on the Pacific Andean slopes of Ecuador, with intermediate counts (157–169 and 96–125), stronger keels, more robust bodies, and both lighter ( S. zaheri ) and darker ( S. calamitus ) colorations (see Figs. 3 , 8, & 9 from Pyron et al. 2015 and Fig. 5 from Torres- Carvajal et al. 2015). The third is the S. lasallei group ( S. lasallei , S. insulomontanus , S. zamora , and S. bogerti ), with lower to intermediate counts (144–168 and 88–126), heavy keels, and darker colorations (see Figs. 3 & 9 from Pyron et al. 2015 and Fig. 5 from Torres-Carvajal et al. 2015). The placement of S. plectovertebralis is uncertain, and we suggest it may form a fourth group with small body sizes (~ 200mm SVL), low counts (144–147 and 79– 91), nuchal collars, and weak keels. The phylogenetic placement of this group is not known, and it could potentially include Emmochliophis ( E. miops was originally described in Synophis ), which also have low counts and nuchal collars, but lack a loreal.

The first three groups are also at least partially distinguishable by hemipenial morphology. In all known diaphorolepidine species, the hemipenis is bilobed, semicalyculate, and semicapitate, relatively stout and bulbous, and covered in large spines or hooks near the base. The organ is not markedly different between Diaphorolepis wagneri , Synophis bogerti and S. lasallei ( Bogert 1964; Zaher 1999), and thus does not appear to strongly differentiate individual species, though no quantitative analysis sampling multiple individuals per species has been performed. The organ has also not been described in detail or illustrated for any species in the S. bicolor or S. plectovertebralis groups.

In the S. calamitus group ( S. calamitus QCAZ452; S. zaheri MZUTI3353, 3355), the lobes are stout and blunt, approximately one-half the length of the hemipenial body, which is ornamented with numerous spines, none of which are noticeably enlarged. In contrast, the S. lasallei group is diagnosed by lobes which are more slender than the hemipenial body, and approximately equal to its length. All species have a significantly enlarged spine near the base of the hemipenial body, either on the right side in sulcate view ( S. lasallei USN233062; S. insulomontanus CORBIDI13940) or the left side ( S. zamora QCAZ9174; S. bogerti QCAZ12791). An extensive comparison of more hemipenial material may reveal more significant differences that are useful for diagnosing species.

Similarly, the vertebral condition of many of the newer species is not known. Diaphorolepidine species are generally characterized by heavy modification of the pre- and post-zygapophyses ( Bogert 1964; Fritts & Smith 1969; Savitzky 1974; Hillis 1990; Sheil & Grant 2001). Examining this condition requires either destructive dissection, or expensive microCT scanning. A comparative analysis of material using the latter technique will likely prove invaluable for diagnosing species and determining species boundaries, as well as perhaps understanding the function of this unique adaptation.

Finally, snakes in the genus Synophis have recently been referred to as "fishing snakes" by various sources, such as the Reptile Database (http://www.reptile-database.org/), the IUCN Red List (http://www.iucnredlist.org/), Torres-Carvajal et al. (2015), and various news outlets covering the discoveries of Pyron et al. (2015) and Torres- Carvajal et al. (2015). However, the origin of this name is unclear, as no known species are ichthyophagous. The name appears to originate from The Elsevier Dictionary of Reptiles ( Wrobel 2004), but no etymology is given. The only known diet items are gymnophthalmid lizards in Emmochliophis miops and Synophis plectovertebralis ( Sheil 1998; Sheil & Grant 2001).

Thus, we suggest the Standard English Name Andean Shadow Snakes and Standard Spanish Name Culebras Andinas de la Sombra for the genus Synophis , based on their dark color, nocturnal habits, and secretive nature. For the species, the Standard English Names would be Nicéforo María's Shadow Snakes ( S. niceforomariae ), Bicolored Shadow Snakes ( S. bicolor ), Zaher's Shadow Snakes ( S. zaheri ), Calamitous Shadow Snakes ( S. calamitus ), La Salle's Shadow Snakes ( S. lasallei ), Mountain Shadow Snakes ( S. insulomontanus ), Zamoran Shadow Snakes ( S. zamora ), Bogert's Shadow Snakes ( S. bogerti ), and Braided Shadow Snakes ( S. plectovertebralis ). Suggested Standard Names in Spanish are, respectively, Culebras Andinas de la Sombra de Nicéforo María, Culebras Andinas de la Sombra bicolores, Culebras Andinas de la Sombra de Zaher, Culebras Andinas de la Sombra calamitosas, Culebras Andinas de la Sombra de La Salle, Culebras Andinas de la Sombra monteses, Culebras Andinas de la Sombra de Zamora , Culebras Andinas de la Sombra de Bogert, and Culebras Andinas de la Sombra trenzadas.

Figures

FIGURE 1. Bayesian maximum clade credibility phylogeny for Diaphorolepidini, summarized from 15 million post-burnin generations in MrBayes 3.2. 5. Support values> 50 % are shown. Clades of primarily North American (NA), Central American (CA), and South American (SA) species other than Diaphorolepidini are collapsed.

FIGURE 2. Holotype (MHUA 14577) of Synophis niceforomariae in life.

FIGURE 3. Paratype (MHUA 14133) of Synophis niceforomariae in preservative.

FIGURE 4. Map of verified localities for the 9 known, extant species of Synophis. Circles are colored by species: S. niceforomariae (purple), S. lasallei (yellow), S. plectovertebralis (black), S. bicolor (green), S. calamitus (teal), S. bogerti (orange), S. zamora (pink), S. zaheri (red), and S. insulomontanus (blue).