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We investigated the thermoregulatory abilities and behavior of Pseudocordylus melanotus melanotus (Drakensberg crag lizard) in terms of the relationship between the operative temperature (Te), selected temperature (Tsel), set-point range (Tset) and field active body temperature (field Tsel), exposure to low temperature, body posture and activity. The Te range for P. m. melanotus was about 58 C (23.20 C in winter to 54.94 C in summer). In a laboratory thermal gradient, in a setting that is independent of ecological costs or thermal constraints, lizards maintained Tset (defined as the interquartile range of Tsel, after Hertz et al., 1993) between 29.00 6 0.36 C and 31.78 6 0.16 C in winter and 29.61 6 0.28 C and 32.47 6 0.18 C in summer. The mean Tsel was 30.08 6 0.14 C in winter and 30.99 6 0.11 C in summer. In the field, however, lizards achieved significantly lower Tb, which suggests that the thermal environment limited the Tb that lizards were able to achieve. Lizards were active for significantly longer and selected significantly higher Tb in summer than in winter. During winter, lizards spent a significant amount of time at Tb below their lower critical limiting temperature (defined by loss of righting). The most frequently assumed body postures in summer were those where the head or body were raised, whereas, in winter, lizards usually lay with head and body flat on the rock substrate. We suggest that these differences reflect the physiological requirements of the lizards: Head-up postures in sit-and-wait foragers are consistent with scanning for prey while head-down postures are likely motivated by thermoregulatory needs. It is clear that P. m. melanotus can thermoregulate efficiently, but the Tb maintained may be constrained by the range of Te available to the lizards in their natural environment. Pseudocordylus m. melanotus currently appears to be geographically constrained by low environmental temperatures at the edge of its range. Should global warming become a reality in southern Africa, this species could inadvertently benefit by occupying new habitat that was previously unavailable because of thermal constraints.

1. An organism's thermal tolerance to the environment may indicate a thermal limit to its geographical distribution. 2. We measured the lower critical minimum (CTMin) and lower lethal temperature in the lizard Pseudocordylus melanotus melanotus . 3. CTMin was 10.17±0.48 °C and the lower lethal temperature was −5.15±0.31 °C. 4. All lizards that froze did not survive. This suggests that these lizards are restricted to areas where the microclimate allows them to avoid freezing. 5. Pseudocordylus m. melanotus can allow their body temperatures to drop well below CTMin without any ill effect.

Abstract A new crag lizard of the genus Pseudocordylus is described from the Western Cape Province, South Africa. It is an archaic melanistic form, occurring in sympatry with other archaic melanistic lizard and mollusc taxa within the mistbelt of the Hottentotsholland Mountains, part of the Cape Folded Mountains. With a maximum snout-vent length of less than 80 mm, it has an exceptionally small body size for a crag lizard. It has a conservative morphology which bridges the morphological gap that exists between Pseudocordylus and Cordylus. It is suspected that this species has a very restricted range in the Hottentotsholland Mountains, and that indiscriminate burning of the veld and collecting of the species may pose a serious threat to its survival.

EXTENDED ABSTRACT Reproduction in the viviparous lizard, Pseudocordylus m. melanotus, is distinctly seasonal. Females exhibit autumn/winter vitellogenic activity, with ovulation occurring during July-September. Females are gravid during the late winter-spring period and parturition follows in early summer (December), with 1–6 young being produced. Males exhibit a basic pre-nuptial spermatogenic cycle. Testicular recrudescence begins in summer, followed by peak size and spermiogenesis in late summer/early autumn, and testicular regression during winter and spring. Males become reproductively active during a period of increasing ambient temperature and photoperiod, whereas these environmental parameters declined during the onset of vitellogenesis in females.