Tursiops erebennus, (COPE, 1865)

Costa, Ana P. B., Mcfee, Wayne, Wilcox, Lynsey A., Archer, Frederick I. & Rosel, Patricia E., 2022, The common bottlenose dolphin (Tursiops truncatus) ecotypes of the western North Atlantic revisited: an integrative taxonomic investigation supports the presence of distinct species, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 196 (4), pp. 1608-1636 : 1629-1630

TURSIOPS EREBENNUS ( COPE, 1865)

Synonymy: Delphinus erebennus Cope, 1865 ;

Tursiops subridens True, 1884 .

Suggested common name: Tamanend’s bottlenose dolphin.

Etymology: The generic name, Tursiops , derived from Latin Tursio (Latin) , a dolphin-like fish in Pliny’s Natural History, originally from thyrsiōn (Greek). The suffix - ops (Greek) is a reference to the face or appearance. For the species epithet, erebennus, Cope did not provide an etymology, but he mentioned an apparently darker coloration ( Cope, 1865: 281). Thus, his use of erebennus might reference Erebus or Erebos, (Ἔρεβος) a Greek mythological primordial deity representing deep darkness or shadow. The English common name references Chief Tamanend (1628– 1701) of the Turtle Clan of the Nanticoke LenniLenape Tribal Nation. Chief Tamanend (‘The Affable’) was known for his wisdom and peaceful nature, and he signed a series of peace treaties with William Penn (founder of the Province of Pennsylvania), starting in 1683. The Nanticoke Lenni-Lenape Tribal Nation is formed by the descendants of the Lenni-Lenape Tribe and the Nanticoke Tribe, the original people to inhabit the lands between south-eastern New York and Delmarva Peninsula, including all of New Jersey, eastern Pennsylvania and Delaware Bay, the region where the holotype of Tursiops erebennus was found. This common name was chosen in consultation with representatives of the Nanticoke Lenni-Lenape Tribal Nation.

Holotype and type locality: Physically mature (incomplete) postcranial skeleton ( Fig. 7 ) of unknown sex (≥ 228.6 cm) in the Academy of Natural Sciences of Drexel University (deposited under the museum number ANSP 3020), collected by S. B. Howell (collector). The specimen was obtained from a fisherman’s seine net at the Red Bank, a community in the West Deptford Township (NJ, USA), along the Delaware River , to the east of Philadelphia (PA, USA). Vertebral formula: C 7 + T 12 + L 14 + Ca 14+. Mitochondrial DNA control region haplotype (354 bp): Ttr2 (GenBank accession number: OM540927 ).

Diagnosis: The skulls of T. erebennus can be differentiated from T. truncatus (offshore ecotype in the western North Atlantic) using the following five morphological features together. As observed from the left lateral view (Supporting Information, Fig. S1C ): (1) cranial vertex elevated (anterior end of the nasals at slightly higher height than the other components of the cranial vertex); (2) shorter lacrimal, with its anterior end more flat (square shaped) and ending before the anterior end of the ascending process of the maxilla (usually, the latter is fully covering the anterior end of the lacrimal, which ends at almost the same height as the preorbital process of the frontal); and (3) straight (non-convex) pharyngeal crest. As observed from the ventral view (Supporting Information, Fig. S1D ): (4) intermediate to narrower vomer when compared with the posterior process of the pterygoids; and (5) the posterior border of the pterygoid hamuli is more in an acute angle to the sagittal plane of the skull. Tursiops erebennus specimens can also be differentiated from T. truncatus specimens based on molecular genetic characters: one fixed difference was found in the mtDNA control region between the species (based on a fragment of

1630 A. P. B. COSTA ET AL.

311 bp and 249 mtDNA control region haplotype sequences).

Redescription: This is a small species of bottlenose dolphin, with a known maximum total body length of 286 cm. When considering only physically mature animals based on the vertebral column (N = 13), we found a known minimum total adult body length of 232 cm and a mean of 256 cm for the species. It can be differentiated from T. truncatus based on skull morphometrics ( Mead & Potter, 1995; Toledo, 2013; present study), vertebral column morphology (present study), several genetic markers ( Hoelzel et al., 1998; Kingston & Rosel, 2004; Rosel et al., 2009; present study), body length ( Mead & Potter, 1995; present study), distribution ( Torres et al., 2003; Rosel et al., 2009; Waring et al., 2009; Hayes et al., 2017), parasite load ( Mead & Potter, 1990), food habits ( Mead & Potter, 1995), haematological profile ( Duffield et al., 1983) and, possibly, colour pattern ( Wells & Scott, 1999). Based on our data set, the condylobasal length in physically mature skulls ranges from 426 to 510 mm, but it is possible that a larger sample size might show individuals outside this range. Physically mature skulls have a relatively short (based on our data set: 226.38–278.74 mm) and narrow (based on our data set: 65.87–86.43 mm) rostrum and narrow internal nares (based on our data set: 56.11–72.77 mm). The vertebral formula, based on 21 individuals, is C 7 + T 12 + L 14–15 + Ca 26–28 = 59–61. It is uncommon to find scars of Crassicauda sp. in the skulls. There are, on average, 23 or 24 alveoli/teeth in each of the tooth rows. There is sexual dimorphism in this lineage based on traditional morphometric analysis of the skulls (with males usually being larger than females based on the skull data set) but not detected with geometric morphometrics.

Distribution: Tursiops erebennus is distributed continuously along the western North Atlantic coast from New York to the east coast of the Florida Peninsula, inhabiting nearshore coastal and estuarine waters ( Rosel et al., 2009; Waring et al., 2009). The extent of the distribution of this species further offshore on the continental shelf of the wNA and in other areas, such as the Gulf of Mexico, Bahamas and the Caribbean, is unknown. However, to date ‘coastal’-form dolphins from the Caribbean Sea have not shared haplotypes with T. erebennus , with a potential exception for only one dolphin from the northern Bahamas. Instead, they are placed in a separate, well-supported clade in the mtDNA control region phylogeny, suggesting some degree of divergence from T. erebennus . Given this apparent genetic divergence between the wNA coastal and Gulf of Mexico and Caribbean coastal animals, we recommend, at this time, that the south-east coast of Florida should be considered the southern limit for the distribution of T. erebennus . Further investigation is needed to resolve the relationship between these two clades, which in turn will clarify the distribution of T. erebennus .

Figures

Figure 1. Map of the western North Atlantic study area showing the sampling locations of samples with only morphological data available (brown), with morphological and genetic data available (cyan) or with only genetic data available (gold). The 200 m isobath line is shown in bold black. Thin black lines represent the 2000 and 4000 m isobaths.

Figure 7. Assembled portions of the postcranial skeleton of the holotype Tursiops erebennus (Cope, 1865) deposited in the Academy of Natural Sciences of Drexel University (museum number ANSP 3020).