Common name

White, William T, Corrigan, Shannon, Yang, Lei, Henderson, Aaron C, Bazinet, Adam L, Swofford, David L & Naylor, Gavin J P, 2018, Phylogeny of the manta and devilrays (Chondrichthyes: obulidae), with an updated taxonomic arrangement for the family, Zoological Journal of the Linnean Society 182 (1), pp. 50-75 : 58-61

Common name : Pygmy devilray

N o m e n c l a t u r a l d i s c u s s i o n: T h e d e s c r i p t i o n o f M. kuhlii by Müller & Henle (1841) does not provide adequate information to determine the identity of this Mobula species ( Fig. 4), but examination of the lectotype ( Fig. 5 ) and paralectotype enables it to be clearly distinguished from M. japanica , M. tarapacana and M. thurstoni . Mobula eregoodootenkee has a very complicated nomenclatural history, which is still largely unresolved. Russell (1803) provided a basic illustration and limited description of a small mobulid caught off south-eastern India, locally known as ‘ Eregoodoo tenkee ’ ( Fig. 6 ). Although the description of the 4 ft. 5 in. (~ 135 cm) DW specimen was brief, it did include the following diagnostic characters: no spine on tail, spiracles absent behind the eyes (suggesting that they were ventral to plane of disc in the specimen examined), narrow strip of granular teeth in each jaw, and mouth behind front of head (not terminal; see Fig. 6 ). These characters, together with the capture location of India, indicate that the species Russell examined was one of the small Indo- West Pacific species with spiracles below the plane of pectoral disc, that is, M. eregoodootenkee , M. kuhlii or M. thurstoni . However, Russell did not designate a type and did not name it binomially; thus, as with other species described in the same publication, Russell’s ‘Eregoodoo tenkee’ is not an available name. In Cuvier (1829) , ‘ Eregoodoo-tenkee, Russ., I, 9’ is listed in a footnote on page 402 and some authors considered him to be the authority for this species, as Cephaloptera eregoodoo-tenkee Cuvier, 1829 ( Notarbartolo di Sciara, 1987). However, Cuvier (1829) did not allocate this species to Cephaloptera ; so, this combination is not valid. Also, when compared to the style used elsewhere in Cuvier (1829) , it appears to be presented in the vernacular and thus not an available binomial name.

The authority for this species has most recently been considered to be Bleeker (1859) with this authority considered the first proper binomial name attributed to this species. Bleeker lists this species as: ‘ Cephaloptera eregoodoo tenkee Cuv. = Eregoodoo tenkee = Russ., fig. 9, 10 = Cephaloptera Olfeisii J. Mull. = Indian Cephaloptera J. E. Gray = Dicerobatis eregoodoo Cant., Cat. Mal. Fish. p. 438’. From this information, it is clear that Bleeker is referring to Cuvier’s use of Russell’s ‘ Eregoodoo tenkee ’. No descriptive features are provided and thus the identity of this species is still not determinable. Two other binomial names are also presented in Bleeker (1859). The first, Cephaloptera Olfeisii , equals C. olfersii Müller, 1836 , which is a junior synonym of M. hypostoma (Bancroft, 1831) occurring in the Western Atlantic. Müller & Henle (1841) included Russell’s Eregoodoo Tenke in the synonymy of C. olfersii although the only distribution provided was Brazil. The second is D. eregoodoo Cantor, 1849 , which is presented as a new name combination for Cuvier’s species, that is, D. eregoodoo (Cuvier) , from Coromandel in India and Penang in Malaysia. Cantor provided a detailed description of this species, including morphometrics, based on a young male specimen (~ 78 cm DW) from Penang on the west coast of peninsular Malaysia. In this description, Cantor states that it agrees with Russell’s ‘ Eregoodoo Tenke, No. IX. R , (not No. IX, N, from St. Helena)’ in several characters, but clearly states that the only individual examined is the Penang specimen. Unfortunately, the whereabouts of the syntype (s?) is unknown. Although most of the descriptive characters are generic for most Mobula species, several key features are provided. For example, the location of the spiracles beneath the origin of the pectoral fins discounts the two large Indo-Pacific species, M. japanica ( Müller & Henle, 1841) and M. tarapacana (Philippi, 1892) , which have the spiracles located above the pectoral-fin origins. Also, the teeth are described as being twice as wide as long, which is similar to that described and illustrated for this species in Notarbartolo di Sciara (1987). In contrast, M. thurstoni (Lloyd, 1908) was found to have longer teeth, not twice as wide as long. Thus, of the currently known Indo-Pacific species, M. kuhlii ( Müller & Henle, 1841) and M. eregoodootenkee (sensu Notarbartolo di Sciara, 1987) are the only options left for Cantor’s D. eregoodoo . Notarbartolo di Sciara (1987) considered D. eregoodoo Cantor, 1849 , to most likely be M. thurstoni due to the white spot on the apex of the dorsal fin, but this character has been found to be variable in at least one species, that is, M. kuhlii . If considered a valid species, Mobula eregoodoo ( Cantor, 1849) would be the correct name for this taxon, not M. eregoodootenkee ( Cuvier, 1829) or M. eregoodootenkee ( Bleeker, 1859) . The latter two combinations should be considered nomen dubium since they provide no characters to distinguish which taxon they denote.

The distinction between M. kuhlii and M. eregoodootenkee (sensu Notarbartolo di Sciara, 1987) has previously been based almost entirely on the length of the cephalic lobes, with the latter species having very long cephalic lobes (> 16% DW) versus relatively short in M. kuhlii (<15% DW). The neotype of M. eregoodootenkee designated by Notarbartolo di Sciara (CAS 56095) illustrates this feature well (fig. 11 in Notarbartolo di Sciara (1987). Notarbartolo di Sciara et al. (2016) provides a detailed redescription of M. kuhlii , with only some limited remarks on how it differs from M. ereegoodootenke . The key to species provided in that paper lists the following characters as separating these two species: ventral pectoral fin coloration, length of cephalic lobes, dorsal fin tip coloration and branchial filter plates. It is puzzling though that the genetic results presented in Henderson et al. (2016), which failed to detect any differences in structure of the NADH2 marker between these two species, are not referred to in this paper despite being from the same region. Thus, it seems that Notarbartolo di Sciara et al. (2016) did not consider available information regarding the lack of genetic differentiation between M. kuhlii and M. ereegoodootenke from Oman.

Remarks: Mobula kuhlii and M. eregoodootenkee have previously been considered distinct, based primarily on the length of the cephalic lobes. It is proposed herein that the relative length of the cephalic lobes is a variable, intraspecific character, based on individuals possessing very long cephalic lobes being sampled together with those with very short lobes at the same location, for example, off Oman. The reported maximum size for the two species is similar (~100 vs. 119 cm DW). One character that has caused some confusion in these species is the presence or absence of a white tip or extent of a whitish hue on the dorsal fin. Mobula eregoodootenkee is reported to have either a plain dorsal fin (or with a whitish hue), while M. kuhlii has been reported as both with and without a white spot on the dorsal fin apex ( Notarbartolo di Sciara et al. 2016). However, this character is variable. For example, two pregnant female M. kuhlii reported from Indonesia had plain greyish dorsal fins, but they each contained a single, late term embryo that had a distinct white spot on the apex of the dorsal fin. Notarbartolo di Sciara (1987) found that M. kuhlii and M. eregoodootenke shared the following characters which are diagnostic for mobulid species: no caudal spine, base of tail quadrangular in cross-section, spiracles subcircular and located ventral to plane of pectoral fins, tooth bands about three-quarters of mouth width, teeth wider than long and anterior margin of pectoral fin straight. Although some differences were noted in the tooth morphology, this was based on an adult male M. eregoodootenkee and juvenile males of M. kuhlii .

In a number of specimens of devilrays identified as M. eregoodootenkee , the pectoral fins have a blackish anterior margin with a broader blackish marking on central anterior margin ( Fig. 7a ). In contrast, most short-headed forms of M. kuhlii that were examined lacked these, but instead the distal portion of the ventral pectoral fins was dusky ( Fig. 7b ), versus white in the above specimens ( Fig. 7a ). This character was also reported by Notarbartolo di Sciara et al. (2016) as one of the key characters to distinguish between M. kuhlii and M. eregoodootenkee . Since coloration can be highly variable in a number of myliobatoid rays, for example, melanistic forms of M. birostris and M. alfredi , further investigation into the validity of this character is needed with examination of a larger number of specimens. As with the length of the cephalic lobes, we consider this difference to be related to intraspecific variation and not an interspecific character. Paig-Tran et al. (2013) found that the branchial filter plates differed between M. eregoodootenkee and M. kuhlii with the terminal lobe being far more elongate in M. eregoodootenkee . This character was not confirmed with the specimens examined in this study. It should be noted that only a single specimen was available for both species in the Paig-Tran et al. (2013) study, thus intraspecific variation could not be taken into account. Notarbartolo di Sciara et al. (2016) stated that the terminal lobes on the filter plates of M. kuhlii were leaf-shaped to spade-shaped, but it was not stated how many specimens were dissected to view this character. No additional information on the filter plates of M. eregoodootenkee was provided. Therefore, as with the other characters that have previously been used to separate these species, it is poorly understood how these characters vary within species.

The genetic analyses undertaken in this study show that specimens identified morphologically as M. kuhlii and M. eregoodootenkee are consistently very closely related based on analyses of both mitochondrial genomes and nuclear exon data ( Figs 1 , 2 ). The observed divergence between these taxa was within the range of intraspecific divergences observed for other mobulid lineages based on our expanded taxon sampling of mitochondrial NADH2 data (Supporting Information Fig. S1 ), an order of magnitude lower based on the mitochondrial genome data and among the lowest pairwise divergences observed for the nuclear exon data. Strengthening this argument is the presence of both long-head and short-head forms from Oman, which are indistinguishable based on sequencing of the mitochondrial NADH2 locus (Supporting Information Fig. S1 ; Henderson et al., 2016). In this paper, long-head forms are referred to as M. eregoodootenkee (GN9431, GN9437 and GN9438) and short-head forms are referred to as M. kuhlii (GN9426-30, GN9432, GN9678-80, GN9726, GN9729, GN9737-38 and GN9747). Thus, although there is some morphological evidence to support M. eregoodootenkee distinct from M. kuhlii , the combined morphological and detailed molecular data presented herein lead us to conclude that M. eregoodootenke is a junior synonym of M. kuhlii .

Figures

Figure 1. Phylogenetic tree showing the relationships among mobulid species, relative to three outgroups (Aetobatus narinari, Myliobatis aquila and Rhinoptera bonasus). The tree was derived from a Maximum Likelihood analysis of an alignment of the protein coding components of the mitochondrial genomes (11442 sites) under a partitioned model of molecular evolution. Bootstrap support values are displayed on the nodes.

Figure 2. Phylogenetic tree showing the relationships among mobulid species, relative to three outgroups (Aetobatus narinari, Myliobatis aquila and Rhinoptera bonasus). The tree was derived from an ML analysis of a concatenated alignment of 614 ‘clock-like’ exons (144261 sites) under a TIM + I + G model of molecular evolution. Bootstrap support values are displayed on the nodes for concatenated ML and SVD Quartet analyses.

Figure 5. Dorsal view of the alcohol-preserved lectotype of Mobula kuhlii (MNHN 000-1596, juvenile male 71.7 cm DW).

Figure 6. Original illustration (ventral view) of Eregoodoo tenkee in Russell (1803); presented only as a vernacular name thus not an available name.

Figure 7. Ventral coloration of: (A) long-head form of Mobula kuhlii (originally identified as Mobula eregoodootenkee), adult male from Muttrah in Oman; (B) short-head form of Mobula kuhlii, female from Muttrah in Oman.