Cetaceans form one of the most unique groups in the evolutionary history of mammals. They have returned to the sea and modified their tail as an efficient means of locomotion. As they adapted to the limited visibility in the aquatic environment, the odontocetes developed a system of echolocation that resulted in extensive modifications to the skull bones. This made descriptive comparisons very difficult and early anatomists unwittingly composed new terms for anatomical structures that had already been named in other taxa. This made anatomical comparisons, based on the literature, extremely tenuous. This lexicon is an attempt to remedy that situation in that it provides headwords and definitions for all the terms that have been used in describing the mammal skull and notes the synonymous terms. The lexicon includes the human nomenclature (Nomina Anatomica), the veterinary nomenclature (Nomina Anatomica Veterinaria) and the nomenclature that is used in descriptive comparative anatomy. The lexicon covers not only extant but extinct mammalian groups and is extensively indexed.
