Amblyrhynchus cristatus, BELL, 1825

CRISTATUS BELL, 1825 View in CoL

( FIGS 5G–N, 7)

Iguana (A[mblyrhynchus]) Ater Gray, 1831 . Holotype. Type locality: ‘From the Galápagos’. Specimen not located (according Frost & Etheridge, 2012) and here considered to be lost. Synonymy by Boulenger, Cat. Liz. Brit. Mus. Nat. Hist., 2: 185.

Amblyrhynchus cristatus albemarlensis EiblEibesfeldt, 1962 . Holotype: SMF 64179 About SMF . Type locality: ‘ Insel Albemarle’ [= Isla Isabela]. No paratypes.

Holotype: OUMNH 6176. Type locality: allegedly Mexico: ‘Habitat in Mexico (…) Sent from mexico by Mr. Bullock’ ( Bell, 1825: 204). Eibl-Eibesfeldt (1956: 88) designated as new ‘Terra typica’ the island of ‘Narborough’ [= Isla Fernandina ]. No paratypes.

Specimens examined (N = 30): Isabela: SFM 64179, coll. by I. Eibl-Eibesfeldt in 1957, Elisabeth Bay (holotype of A. c. albemarlensis and neotype of Iguana ater , stuffed specimen; see nomenclatural acts below). CAS 11253–11260, coll. by R.H. Beck in 1906, Iguana Cove. CAS 11311, 11313, 11314, coll. by J.R. Slevin and E.S. King in 1906, vicinity of Tagus Cove. CAS 65996– 65998, coll. by H. Moffitt in 1905, Tagus Cove. Tortuga (off Isabela): CAS 10284–10289, coll. by J.R. Slevin in 1905, no exact locality. Fernandina : HLMD-RA-3067, coll. by G. Scheer in 1954. CAS 11510–11514, coll. by J.R. Slevin and E.S. King in 1906, no exact locality. SFM 57401, 57402, coll. by I. Eibl-Eibesfeldt in 1957, NE coast of the island, Punta Espinosa. Unknown island: OUMNH 6176 (holotype of A. c. cristatus ).

Comment on type locality of A. cristatus Bell, 1825 : Ascertaining the plausibility of the designation (emendation) of the type locality of this nomen by Eibl-Eibesfeldt (1956) is complex. Before 1825, few expeditions took place to the Galápagos, such as the 1789– 1794 Malaspina expedition and the 1793 expedition by James Colnett. However, whaling ships regularly visited the archipelago, and one of these, the Thames, visited Fernandina in 1806 ( Langdon, 1984). For the sake of economy in classificatory change, we therefore here follow the type locality emendation of Eibl-Eibesfeldt (1956), given that the provenance of the type specimen of A. cristatus from Fernandina is a definite possibility.

Designation of a neotype for I. ater Gray, 1831 : In A synopsis of the species of Class Reptilia, Gray (1831) gave only very rudimentary details about the material he examined to describe this new species. He nevertheless mentioned in the introduction, the specimens he personally examined: ‘In forming this list, the collection of reptiles of the British Museum, the College of Surgeons, and of Mr. Bell, in London, of the Gardens of Plants and Ecole de Medecine at Paris, of the Royal Museum of Leyden and Berlin, and the Free Town of Francfort, have been studied with attention (…)’. Later, Duméril & Bibron (1837: 197) will likely be the only other scientists having had the opportunity to study the type material examined by Gray, stating that ‘Amblyrhincus ater. Gray’ [sic]: ‘C’est encore une espèce qui n’est connue des naturalistes que part un seul sujet qui fait partie des richesses erpétologiques que renferme le musée britannique’ [this is also a species which is known to naturalists only by a single subject, part of the herpetological treasures held at the British museum]. Such a statement clearly confirms that (1) only a single specimen has been examined by Gray and that (2) it was at that time deposited in the collection of the British Museum (now NHM). To our knowledge, this specimen has never been examined by subsequent authors. Examination of the type catalogue at the NHM did not yield any explicit mentions of this type specimen, and we did not find any specimen in the collection that could be regarded as type of ater . Apparently, all the catalogued marine iguanas in the NHM were collected at least several decades after the original description, in accordance with the statement made by Frost & Etheridge in 2012 who cautiously considered the original type material as ‘not located’.

Two specimens at the Museum of Comparative Zoology at Cambridge (Harvard), MCZ R-6369 and R-6370, are catalogued as ‘syntypes’ of A. ater (whereas additional annotations mention the contrary ‘not a type?’). Both specimens were collected on Duncan (= Pinzón) during the Albatross expedition in 1891, and therefore cannot represent the original type material.

The nomen I. ater would have priority over the majority of subspecific names available for island populations of marine iguanas. We here suggest defining a neotype for this nomen, with the express purpose of stabilizing the subspecies-level taxa defined in the following accounts. As further qualifying conditions for a neotype designation according to §75.3 of the Code, we have above elaborated why we consider the holotype of I. ater to be lost, and it is also clear that the neotype selected in the following is morphologically consistent with the very rudimentary information available on the former name-bearing type (from the original description; see above).

The Code also requires that the neotype comes as near as practicable from the original type locality. We selected as neotype the specimen SMF 64179 About SMF from Isabela (deposited in a recognized scientific or educational institution and here documented morphologically in Fig. 5 as required by the Code). Isabela was visited by at least three whaling ships before 1831 ( Langdon, 1984) and therefore this island has a high likelihood to have been the source of the lost holotype .

Finally, the Code requires a statement of the characters differentiating the nominal taxon for which a neotype is designated from other taxa. In this study, we summarize the characters distinguishing A. c. cristatus (and thus its synonym ater ) from all other subspecies of marine iguanas (e.g. Table 1). As we consider ater to be a synonym of the nominal subspecies A. c. cristatus , it cannot be distinguished from this taxon at present. Yet, we feel that the designation of a neotype is justified in this case as it contributes to resolving taxonomic uncertainty, stabilizing all other subspecies names in a species where subspecific units are at the core of intensive conservation efforts (see Discussion).

The selected neotype specimen (SMF 64179) is at the same time also the holotype of A. cristatus albemarlensis Eibl-Eibesfeldt, 1962 and this latter nomen therefore becomes an objective junior synonym of I. ater Gray, 1831 .

Geographic distribution: Isabela, Tortuga, Fernandina and very likely their satellite islets ( Fig. 8).

Diagnostic description: A. cristatus cristatus is a large-sized marina iguana subspecies (mean SVL 342 mm, up to a maximum of 480 mm). Mature males are characterized by a remarkably well-developed crest of spines and pronounced prominent conical supracephalic scales. In preservative, males have a yellowish dorsal background, marbled or speckled with small black dots, frequently aligning and merging to each other to form five to ten spindle-shaped transversal stripes along the body. This subspecies does not seem to present particularly remarkable pholidotic features (see also Figs 4, 5G–N, Table 1).

Redescription of the holotype: OUMNH 6176 ( Fig. 5G), adult unsexed stuffed specimen very poorly preserved, presenting a long sutured slit running from the throat to the cloaca, missing eyes (replaced by glass marbles) and toes II to IV of the left foot. Skin apparently varnished and/or painted, and coated in some parts, preventing detailed examination of several characteristics of scalation. SVL (345 mm) shorter than tail length (483 mm). Details of the cephalic scalation barely visible. Subdigital lamellae 25 under the right third toe, 32 under the right fourth toe. Approximately 280 visible transversal rows of minute scales at midbody. Dorsal crest moderately developed, 15 spiny scales running along the dorsal side of the neck (Cnc), followed by a postnuchal gap of approximately 10 very reduced scales (Cng), 82 spiny scales running along the dorsal side of the trunk (Cdc), then at least 136 visible scales on the dorsal side of the tail.

Skin very likely painted or varnished, uniformly dark grey, ventral side and lateral sides of the throat slightly lighter.