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Psammophylax

 

Keates e.a. 2019:
Psammophylax (Fitzinger 1843; subfamily Psammophiinae) is a widespread African snake genus, commonly referred to as skaapste‐kers (“sheep‐stabbers”) for the erroneous belief that they commonly bite and kill sheep. The last systematic review of the genus documented only three species, viz. Psammophylax rhombeatus, P. variabilis, and P. tritaeniatus, with four subspecies (P. r. rhombeatus, P. r. ocellatus, P. v. multisquamis, and P. v. vanoyei) (Broadley, 1977). Spawls et al. (2018), Spawls et al. (2002) informally, based on correspondence with the late Donald Broadley, treated P. v. multisquamis as a valid species (S. Spawls personal communication). This treatment was followed by subsequent authors, but without a formal species elevation. Largen and Spawls (2010) argued that the taxon should be retained as a subspecies of P. variablis pending the results of a molecular analysis. Kelly et al. (2008) transferred Rhamphiophis acutus and R. togoensis (Figure 1a‐c) to Psammophylax based on genetic similarity and the collective monophyly of the group. New mo‐lecular and morphological analyses by Branch, Baptista, Keates, and Edwards (2019) suggested that P. ocellatus (Bocage 1873) (previously P. rhombeatus ocellatus) is a full species alongside P. acutus, P. multisquamis, P. rhombeatus, P. tritaeniatus, P. togoensis, and P. variabilis, bringing the updated number of Psammophylax species to seven.

Keates e.a. 2019 describe the genus as follows (I omitted again all references, and refer to the paper for these details).
African grass snakes are small‐ to medium‐sized lamprophiids that are found in the moist Savanna and Grassland Biomes, and are often characterized as being terrestrial, diurnal, and active foragers. Several species of Psammophylax display death‐feigning and clutch guarding, with the latter behavior being closely associated with P. rhombeatus. Body striping is evident in all species, and coloration and pattern differences are the most prominent distinguishing characteristics between the species as they are currently defined. The sharply pointed snouts of P. acutus and P. togoensis distinguish them from all other members of the genus, and this feature was responsible for their former inclusion in the genus Rhamphiophis (beaked snakes).
Cryptic species pose a particular challenge for systematics and taxonomy, and may result from recently evolved sister species having ambiguous species boundaries because salient morphological differences have not yet accumulated . Several key instances of cryptic speciation have been highlighted in the Lamprophiidae. For example, Mimophis occultus (occultus — Latin for “concealed in plain sight”) was recently described from northern Madagascar (Ruane et al., 2018), indicating that widespread habitat generalists may be incorrectly described when taking only morphology into account. The taxonomic history of Psammophylax suggests that cryptic speciation might be concealing diversity within this genus. The use of genetic methods, especially with widespread and generalist species that live in close proximity to forests, may uncover diversity previously missed by morphologically orientated taxonomy.Although widespread and abundant, Psammophylax remains an understudied genus. Past studies focused on the subfamily and family levels, respectively. Kelly et al. (2008) utilized only one representative from each species of Psammophylax, as their study focused on the Psammophiinae subfamily. Irrespective of the small sample size, they found enough genetic resolution to transfer Rhamphiophis acutus to the genus Psammophylax. The lack of rigorous genus‐specific research, coupled with the possibility of cryptic speciation, makes this genus a viable candidate for a phylogenetic study.

Keates e.a. 2019 investigated the phylogenetic relationships between individuals of Psammophylax, including the morphologically disparate Psammophylax acutus group. They sampled from several regions within each species’ range and produced a phylogenetic tree with multiple algorithms. They then investigated the level of divergence of each clade within the tree to test for species‐level divergences. They also investigated the morphological differences between genera in the subfamily Psammophiinae, and differences between species of Psammophylax, using both traditional morphological and geometric morphometric techniques.

Due to copyright, we cannot publish the paper by Keates e.a. 2019 here, but the results are used in the information on this site.

The results of the phylogenetic analyses is:

As for traditional morphology: on the basis of skull morphology, dentition, and genetics, the authors found that Psammophylax can be divided into two main groups:
(a) the “acutus”group — shorter skull with the rostral bones in the anterior skull weakly braced by the nasals (with only a single contact between nasal and frontal), high number of dentary teeth (21–24), and acutely pointed snout; and
(b) the “Psammophylax” group — longer skull that lacks the reinforced nasal/frontal bones, lower number of dentary teeth (15–18), and rounded snout.

Given the phylogenetic results and the morphological distinction between Psammophylax acutus and the remaining Psammophylax species, Keatess e.a. 2019 recognize two genera and describe a new genus for the “acutus” group: Kladirostratus gen. nov. In addition, although not well supported by traditional morphology or geometric morphometric analyses, they address the polyphyly of P. multisquamis and describe one group of P. multisquamis as a new species.