Toothed whale whales do not have wax ester deposits nor branched fatty chain acids in their blubber. Thus, more recent evolution of these complex blubber traits occurred after baleen whales and toothed whales split, and only in the toothed whale lineage. Toothed whales have torpedo-shaped bodies with inflexible necks, limbs modified into flippers, nonexistent external ear flaps, a large tail fin, and bulbous heads (with the exception of sperm whales). Their skulls have small eye orbits, long beaks (with the exception sperm whales), and eyes placed on the sides of their heads. Toothed whales range in size from the and vaquita to
Divided differences "ƒ" on the nodes "x", ..., "x" are used: etc. Divided differences for formula_12 and the first few values of formula_13: To make the recursive process more clear, the divided differences can be put in a tabular form: The divided difference scheme can be put into an upper triangular matrix. Let formula_24. Then it holds formula_44 With the help of a polynomial function formula_45 with formula_46 this can be written as Alternatively, we can allow counting backwards from the start of the sequence by defining formula_48 whenever formula_49 or formula_50. This definition allows formula_51 to be interpreted as formula_52, formula_53