The padloper’s tortuous path (Chelonia: Testudinidae): Two genera, not one

ABSTRACT

Since 1957, all padlopers were considered Homopus, which was an anomaly, because only two species have four claws on the front and hind limbs. The revival of the genus Chersobius for the five-toed species (signatus, boulengeri and solus) now limits Homopus to the four-toed species (areolatus and femoralis). Molecular data indicate that Homopus is paraphyletic with two well-supported clades: the four-toed Homopus in one clade and the five-toed Chersobius together with Chersina angulata in a second clade. There are numerous distinct morphological and ecological differences between the genera. All Chersobius species have a single, large inguinal scute, whereas the number is variable in Homopus. The midline pectoral scute of Chersobius is consistently longer, and the nuchal scute shorter, than in Homopus. The fourth to fifth vertebral suture is narrow in Homopus and broad in Chersobius. Forelimb scales also differ with 3–4 large rows and 5–6 smaller rows, respectively, in Homopus and Chersobius. Chersobius males have a plastral concavity and Homopus males not. Two Chersobius species (C. signatus and C. boulengeri) are distinguishable from Homopus by having 12 or more marginal scutes, whereas Homopus species have 11 or fewer. The glans penes are respectively V-shaped and heart-shaped in Homopus and Chersobius. Ecological differences include that Chersobius species are rupicolous and inhabit arid regions, whereas Homopus species inhabit more mesic habitats. Homopus females produce multi-egg clutches and tend to be bigger compared to single-egg clutching Chersobius females. Females of all species are larger than conspecific males, and all males have larger shell openings than females have.

ZooBank—urn:lsid:zoobank.org:pub: 18229454-6662-46F3-8B15-836BF2AC38EB

KEYWORDS:

• aridity
• Chersobius
• Homopus
• rock-dwelling
• Southern Africa
• tortoise

Acknowledgements

We thank Melita Vamberger for preparing the ML tree, Alfred Schleicher for access to his captive tortoises and the herpetological curators of the Iziko and Bayworld Museums for access to their tortoise collections. William R. Branch is credited for the photographs in Figures 2 and 3.

Supplemental material

Supplemental data for this article can be accessed at https://doi.org/10.1080/21564574.2018.1398187

ORCID

Margaretha D. Hofmeyr http://orcid.org/0000-0002-4963-6750