High incidence of limb skeletal variants in a peripheral population of the red-backed salamander, Plethodon cinereus (Amphibia: Plethodontidae), from Nova Scotia

A single population of Plethodon cinereus from northwestern Nova Scotia shows a high incidence of limb skeletal variants, which is exceptional for this morphologically conservative species. Included are nine carpal patterns and five tarsal patterns, which result from the variable occurrence of 11 different combinations of fused adjacent mesopodial elements, and frequent absence of one or more ossified phalanges; one instance of increased phalangeal number also is noted. Primitive plethodontid carpal and tarsal patterns, which characterize P. cinereus from other parts of its range, occur in 69 and 71% of the carpi and tarsi examined, respectively. Modal phalangeal formulae also are those typical of P. cinereus generally. Several mesopodial variants resemble those seen in other plethodontid genera; they may have appeared independently in P. cinereus. Others are unique to this population. Both the genetic basis and geographical extent of this variation are unknown.