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In delphinid species skull shape evolution may have been indirectly influenced by several evolutionary changes (Amaral et al. 2009). The two currently recognized species of the genus Globicephala provide an interesting example of a recent and complex evolutionary history (Oremus et al. 2009). The long-finned pilot whale (Globicephala melas, Traill 1809) and the short-finned pilot whale (Globicephala macrorhynchus, Gray 1846) are large delphinid species, widely distributed, that can be found in both nearshore and pelagic environments (Olson 2009). Size, shape, and color pattern distinctions between the two species are too variable to consider them as reliable characters for discrimination. Morphological differences between the two species based on flipper length are clear: on average pectoral fins of G. melas are one-fifth the body length, whereas on G. macrorhynchus they are one-sixth the body length (Olson 2009). Efforts for identifying free-ranging pilot whales in the northwest Atlantic. region have been made using a simple photograph-based approach,based on relative morphological features and pigmentation patterns (Rone and Pace 2012). Overall, apart from pectoral fin length, the only distinctive aspect between the species is reflected in the skull (van Bree 1971). On one hand, the longfinned pilot whale has a narrower skull, with the premaxillae leaving uncovered 1 cm of the lateral borders of the maxillae, and 9?12 teeth in each row. On the other hand, the short-finned pilot whale has a shorter and broader skull, with the premaxillae covering the maxillae, and 7?9 teeth in each row (Olson 2009). Phylogenetic analyses of mitochondrial DNA (mtDNA) also support their species status (May-Collado and Agnarsson 2006, Oremus et al. 2009).

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