The structure of the posterior abdominal and anterior caudal region in three elongate fishes showing the ‘ambush predator’ body shape. A, Esox lucius (Esocidae); B, Lepisosteus osseus; C, Saurichthys cf. paucitrichus (PIMUZ T 534). The region around the abdominal-caudal transition is indicated in the insets, and the following morphological landmarks are indicated: 1, first vertebra bearing a haemal arch (i.e., first caudal vertebra); 2, end of the body cavity, 3, first pterygiophore of the anal fin; 4, last rib-bearing vertebra; 5, morphological transition between the anterior and posterior caudal regions as indicated by the reduced haemal arches and transition to T-shaped neural arches. Photo in panel B copyright PIMUZ, courtesy of T. Scheyer.