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Keywords:

  • Stenella;
  • dolphins;
  • taxonomy;
  • Delphinus;
  • osteology;
  • geographical Variation

Abstract

The taxonomy of the spotted dolphins has been confused. Two apparent species exist, one endemic to the Atlantic and the other pantropical. They have sharply different color patterns and non-overlapping vertebral counts. However, the holotype specimens for most of the names that have been applied to the spotted dolphins (including S. attenuata, S. frontalis, S. plagiodon and others) are skulls only, with no information on coloration or number of vertebrae. The two species overlap in all skull characters; geographical variation in both is pronounced. We used a discriminant analysis based on tooth counts and three skull measurements (standardized to skull width) to identify the type specimens to the two species. We used other criteria for assignment of nominal species for which holotype specimens do not exist. We propose that Stenella frontalis (G. Cuv., 1829) be used for the Atlantic endemic species and Stenella attenuata (Gray, 1846) for the pantropical species and here redescribe the species. Proposed common names are Atlantic spotted dolphin and pantropical spotted dolphin. S. frontalis now includes Delphinus froenatus F. Cuv., 1829, D. doris Gray, 1846 and D. plagiodon Cope, 1866. S. attenuata (a nomen conservandum) includes D. velox G. Cuv., 1829, D. pseudodelphis Wiegmann, ≤ 1840, D. brevimanus Wagner, 1846, D. microbrachium Gray, 1850, D. albirostratus Peale, 1848, Steno capensis Gray, 1865, Clymene punctatus Gray, 1866, Steno consimilis Malm, 1871 and Prodelphinus graffmani Lönnberg, 1934. Unidentifiable to either of the two valid species are D. dubius G. Cuv., 1812, D. pernettensis de Blainville, 1817 (suppressed), D. malayanus Lesson, 1826 and D. Rappii Reichenbach, 1845; these must remain incertae sedis.