Sonora occipitalis

Cox et al. (2018) proposed synonymizing Chionactis and Chilomeniscus with Sonora, which has taxonomic priority over both genera. This species is in the subgenus Chionactis with S. annulata and S. palarostris.

Based on genetic and phenotypic evidence, Wood et al. (2014) proposed that two species be recognized, Chionactis occipitalis and C. annulata. This was accepted by Crother (2017).

There is some question as to the validity of the name C. saxatilis (Funk 1967), the Gila Mountains Shovel-nosed Snake, which is generally considered to be a synonym of C. o. annulata (see Cross 1979). Mahrdt et al. (2001) considered C. saxatilis a synonym of C. o. annulata. Wood et al. (2008) demonstrated, using mtDNA and morphological data, that population structure was not concordant with the traditional subspecific taxonomy. They also revealed two potentially independent evolutionary lineages. A phylogeographic study from Wood et al. (2014) using mtDNA and microsatellites indicates that C. o. annulata should be elevated to species status, while retaining two subspecies C. a. annulata and C. a. klauberi, that conform to patterns of genetic structure. The authors find no support for C. o. talpina and place it in synonomy with C. occipitalis (Crother 2017).

This species is widespread and common within a limited range in the southwestern U.S. and northwestern México. It faces threats from habitat destruction due to development and agriculture. The population appears to be stable with no reports of recent declines.

This species occurs in the interior deserts of the southewestern United States and northwestern México. It is found in southern California, northwestern Arizona, southern Nevada, Baja California Norte, and northwestern Sonora (Mahrdt et al. 2001, Wood et al. 2014, Holycross and Mitchell 2020). Using Global Biodiversity Information Facility (GBIF) (2025) records from 1990-2025, range extent is estimated to be 307,273 km² (RARECAT 2025).

There are many occurrences throughout the range.

No major rangewide threats are known at this time. At the eastern end of the range in Arizona, habitat destruction in the form of development and conversion to agriculture is an ongoing threat (Bradley and Rosen 2020). This threat likely also applies to the western edge of its range where there are large population centers. Drastic increases in road traffic has likely increased mortality in this species as it has in other desert snakes (Jones et al. 2011).