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Abstract

The vertebral morphology of the estuarine dolphin, Sotalia guianensis (Cetacea, Delphinidae). We present a description of the backbone of the marine tucuxi (Sotalia guianensis) vertebrae (n=34), including the variations in the vertebral formula (n=32) (UFSC-Universidade Federal de Santa Catarina): Ce7 , T12 , L10_12, Ca23_25 == 52-56. Species diagnostic characters and intraspecific variations are presented. Cervical ribs occur in 22.5% of the samples. The metapophyses start from the fourth thoracic vertebra, and the zigapophyses start at the cervical level, being observed up to T11 . The inclination of the transverse processes and neurapophyses is most reduced around L5 or L6 . Transverse processes on caudal vertebrae disappear between Ca9 and Can . The neurapophyses, neural arches and metapophyses are observed up to Ca n or Can. Caudal foramina appear between Ca3 and Ca6. The height of the vertebral body increases up to Ca n, then starts to decrease. The maximum width is found around Ca6, where the vertebral body becomes laterally compressed. The length of the vertebral body increases from the last cervical to T7 andthen remains constant up to Ca 13, decreasing from  then on. This is the first study to take into account intraspecifc shape and count variations, representing an improvement over the traditional typologic approach.