THE EVOLUTION OF THE GRASPING HAND IN ANURANS ANO LIZARDS

Abstract

The way in which tetrapods use their limbs is closely related to the substrate on which they move and often involves specialisations in their muscular-skeletal system (Gans & Parsons, 1966; Lutz & Rome, 1994; Shubin & Jenkins, 1995). In the majority of tetrapods, the limbs  have the  double  function  of  support and propulsion.

Especially in tetrapods, conventionally considered inferiors  (anurans  and  lizards),  the  hind  limbs  are dominant when propulsion is generated while the fore limbs have always been considered important for the supportive function.   However, along the phylogeny of tetrapods, different specialisations of the fore limbs have been observed, such as movements that imply the ability to reach for an object, sustain it and manipulate it with the fingers or claws (lwaniuk & Whitshaw, 2000). This ability to manipulate  an object was thought exclusive to the lineage of primates. Even though they execute a bigger force with their hand when grasp, they possess a fine ability in the use of the fingers (Napier 1956); manipulation is common enough in tetrapods. In fact,  sorne  authors  sustain  that  manipulation  or grasping  has  a  common  origin  in  basal  tetrapods, considering the ability to develop these independent movements with the hand, homologous all along the phylogeny of tetrapods (lwaniuk & Whitshaw, 2000).