Locomotion and biomechanics in Eocene mammals from Messel

Eocene mammals from Grube Messel are divided into those that lived terrestrially on the ground (2D-mammals) or arboreally (3D-mammals). Their biomechanics and locomotion are discussed on the basis of equids (Eurohippus, Propalaeotherium) and Leptictidium as examples of 2D-mammals and primates (Europolemur, Darwinius) of 3D-mammals. The determining factor for lifestyle is the autopodia: 2D-mammals need nothing more than compression-transmitting balls with reinforced anterior margins (hooves). These autopodia do not require much energy, but metapodia and even phalanges can elongate the functional length of the free limbs. Primates as 3D-animals need prehensile hands and feet, which can transmit tensile forces and even torques. Their metapodials are part of the prehensile organ. Their strong and energy-requiring musculature increases the masses on the distal limb segments and so influences the locomotor modes.