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Sagmatias obscurus

Mammalia - Cetacea - Delphinidae

Delphinus (Grampus) obscurus was named by Gray (1828). It is extant. Its type specimen is BMNH 41.1733.

It was recombined as Delphinus obscurus by Gray (1828), Gray (1846), Nilsson (1847) and Gray (1850); it was recombined as Clymene obscurua by Gray (1866); it was recombined as Tursio obscurus by Gray (1866); it was recombined as Clymenia obscura by Gray (1868); it was recombined as Tursiops obscurus by Ameghino (1889); it was recombined as Lagenorhynchus obscurus by Trouessart (1904), Oliver (1922), Fraser and Purves (1960), Rice (1998) and Mead and Brownell (2005); it was synonymized subjectively with Lagenorhynchus cruciger by Scheffer and Rice (1963) and Hershkovitz (1966); it was considered an invalid subgroup of Lissodelphinae by Agnarsson and May-Collado (2008); it was recombined as Sagmatias obscurus by LeDuc et al. (1999), Perrin et al. (2013) and Vollmer et al. (2019).

Synonymy list
YearName and author
1826Delphinus superciliosus Lesson and Garnot
1828Delphinus obscurus Gray
1828Phocaena homei Smith
1829Delphinus superciliosus Fischer p. 510
1838Delphinus fitzroyi Waterhouse
1846Delphinus obscurus Gray p. 37 figs. Plate 16
1847Delphinus obscurus Nilsson p. 597
1850Delphinus obscurus Gray p. 107
1866Clymene obscurua Gray p. 215
1866Tursio obscurus Gray p. 264
1868Lagenorhynchus similis Gray
1868Clymenia obscura Gray p. 6
1868Clymenia similis Gray p. 6
1889Tursiops obscurus Ameghino p. 885
1896Tursio panope Canto
1904Lissodelphis panope Trouessart p. 766
1904Lagenorhynchus fitzroyi Trouessart p. 767
1904Lagenorhynchus obscurus Trouessart p. 767
1904Lagenorhynchus supercilliosus Trouessart p. 767
1922Lagenorhynchus obscurus Oliver p. 581
1960Lagenorhynchus obscurus Fraser and Purves p. 112 figs. Figure 26
1998Lagenorhynchus obscurus Rice p. 115
1999Sagmatias obscurus LeDuc et al. p. 639 figs. Figure 2
2005Lagenorhynchus obscurus Mead and Brownell p. 730
2013Sagmatias obscurus Perrin et al. p. 571 figs. Table 1
2019Sagmatias obscurus Vollmer et al.

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phylumChordataHaeckel 1874
subclassDipnotetrapodomorpha(Nelson 2006)
speciesobscurus(Gray 1828)

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

N. L. Vollmer et al. 2019Among Sagmatias, Lagenorhynchus, and Leucopleurus species, the pigmentation of S. obscurus is most similar to that of S. obliquidens and S. australis, however only S. obscurus and S. australis overlap in distri- bution (i.e., off southern South America; Fig 1A). In contrast to S. obliquidens, the dorsal flank blaze of S. obscurus does not extend further anteriorly than mid-body (Van Waerebeek and Würsig 2018). Sagmatias obscurus can be distinguished from S. australis by the former having an extension of the light-colored thoracic patch over the eye (Reeves et al. 2002). In the southern portion of its range, S. obscurus may be confused with S. cruciger; however, the two can be differenti- ated based on the sharply defined light and dark areas, broad dorsal fin shape, and dark pigmentation behind the flipper that is characteristic of S. cruciger (Reeves et al. 2002). Additional features of S. obscurus pig- mentation are given under Coloration.
In general, the skull morphology of all four species of Sagmatias is similar, however S. obscurus and S. obliquidens can be distinguished from other Sagmatias species by having a longer rostrum, shorter brain- case, and lower ramus (Miyazaki and Shikano 1997b). Furthermore, S. obscurus is differentiated from S. obliquidens by having a narrower preorbital width and narrower width of the rostrum at midlength (Miyazaki and Shikano 1997b). Sagmatias obscurus also has fewer ver- tebrae than S. obliquidens (Miyazaki and Shikano 1997b).
The distinction between S. obscurus and the other species of Sagmatias as well as all of the species in the genera Leucopleurus, Lagenorhynchus, Lissodelphis, and Cephalorhynchus is also supported by genetic data from both nuclear and mitochondrial DNA markers (Fig. 2, 3). Phylogenetic stud- ies consistently recover a close sister-species relationship between S. obscurus and S. obliquidens, but the relationship between S. obscurus and S. australis/S. cruciger is less clear and these studies often have included little to no data from the latter two species (Table 2; Harlin- Cognato and Honeycutt 2006, May-Collado and Agnarsson 2006, Agnarsson and May-Collado 2008, McGowen 2011, Banguera-Hinestroza et al. 2014a). Further genus-level taxonomic revision may be necessary for S. obscurus; however, any changes are contingent on additional data and analysis. If S. obscurus and S. obliquidens are determined to be significantly differenti- ated at the genus level from S. australis and S. cruciger, a new genus name will be needed for the former two species as no other synonyms are avail- able for S. obscurus and S. obliquidens and S. amblodon Cope, 1866 (= australis) is the type species of Sagmatias.