Sonora taylori ( Boulenger 1894 )

Cox, Christian L., Davis Rabosky, Alison R., Holmes, Iris A., Reyes-Velasco, Jacobo, Roelke, Corey E., Smith, Eric N., Flores-Villela, Oscar, McGuire, Jimmy A. & Campbell, Jonathan A., 2018, Synopsis and taxonomic revision of three genera in the snake tribe Sonorini, Journal of Natural History 52 (13 - 16), pp. 945-988 : 970-971

Sonora taylori ( Boulenger 1894)

Contia taylori Boulenger 1894:265 . Holotype: Syntypes are in the Natural History Museum of

London (1946.1.5.57–1946.1.5.5). Type locality: Duval County, Texas . Stickel (1943) notes

that the original description reports both Duval County, Texas and the Mexican state of

Nuevo Leon as collection localities, but restricts the type to Duval County, Texas. Chionactis taylorii Cope 1900:936 Sonora taylori Stejneger and Barbour 1917:92 Sonora episcopa taylori Stickel 1943:122 Sonora semiannulata taylori Frost and VanDevender 1979:6 Sonora semiannulata Frost 1983b :333.1

Diagnosis

This species is distinct from Sonora cincta , S. fasciata , S. straminea , S. aemula , S. annulata , S. occipitalis and S. palarostris by the lack of rostral or caudal adaptations. Sonora taylori can be potentially confused only with S. episcopa , with which it is either sympatric or narrowly allopatric. The S. semiannulata species group has been historically difficult to define using morphological characteristics, and in fact it was this lack of clear colour pattern or meristic characters delimiting species that led Frost and VanDevender (1979) to synonymize many different species and subspecies into S. semiannulata . However, our genetic data show clear reciprocal monophyly of S. episcopa and S. taylori . Perhaps the best way to distinguish S. episcopa from S. taylori is by geographic range (see below). Besides geographic range, Dixon and Werler (2005) suggest that S. taylori can be distinguished from S. episcopa based upon the presence of 13 midbody scale rows (compared to 14 or 15 in S. episcopa ).

Variation

Sonora taylori is one of only three species in the genus that do not have bands or stripes, and so lack polymorphism and coral snake mimicry. This uniformly brown snake has some slight variation in ground colour from grey to tan, buff or brown, and Dixon and Werler (2005) have noted that the maculated scales often give the impression of light longitudinal lines. In addition, this species does have polymorphism for the black cap on the head ( Figure 3 ).

Distribution

Sonora taylori is found south and west of the Edwards Plateau and Balcones Escarpment of south Texas ( Figure 3 ) . Stickel (1943) suggested that specimens from Tamaulipas and Nuevo Leon could be considered S. taylori , but we did not have any samples from northeastern Mexico and this should be tested with additional samples.

Remarks

This species is in the subgenus Sonora with S. episcopa and S. semiannulata .

Figures

Figure 3. Map of the geographic distribution from IUCN and georeferenced occurrence records from GBIF (grey crosses) for the subgenus Sonora, including S. episcopa, S. semiannulata and S. taylori. The top of the map has images of the uniform (a), banded (b), striped (c), and mimetic (d) morphs of Sonora episcopa. The side panel depicts S. taylori without (e) and with (f) a black cap on the head. The bottom panel depicts the uniform (a), banded (b), striped (c), and mimetic (d) morphs of S. semiannulata. Photos by C. L Cox (a–f, h) and A. R. Davis Rabosky (g, i, j). Colours of circular points on the map correspond to the phylogenetic tree in Figures 1 and 2.