Amblyrhynchus nanus, GARMAN, 1892

Miralles, Aurélien, Macleod, Amy, Rodríguez, Ariel, Ibáñez, Alejandro, Jiménez-Uzcategui, Gustavo, Quezada, Galo, Vences, Miguel & Steinfartz, Sebastian, 2017, Shedding light on the Imps of Darkness: an integrative taxonomic revision of the Galápagos marine iguanas (genus Amblyrhynchus), Zoological Journal of the Linnean Society 181, pp. 678-710 : 695-696

NANUS GARMAN, 1892

( FIGS 6H–J, 7)

Holotype: NHM 1946.8.30.20 (formerly numbered BMNH 99.5.4). Type locality: ‘ Tower Island’ [= Isla Genovesa ].

Specimens examined (N = 17): Genovesa : NHM 1946.8.30.20, don. by Dr. Baur (holotype of A. c. nanus ). CAS 12272–12274 , coll. by J .R. Slevin in 1906, N coast of the island. CAS 104674 , 104675 , coll. by I.L. Wiggins in 1967, no exact locality. SFM 57432–57435, SFM 57437–57441, SFM 57444, SFM 57445, coll. by I. Eibl-Eibesfeldt in 1957, Darwin Bay .

Geographic distribution: Genovesa and very likely its satellite islets ( Fig. 8).

Diagnostic description: Amblyrhynchus cristatus nanus is a small-sized subspecies of marine iguana (mean SVL 205 mm, up to a maximum of 247 mm). Mature males have a moderately developed crest of spines and moderately conical supracephalic scales. In preservative, males are almost uniformly dark brown or blackish dorsally, with small light ochre dots, most often aligning and sometimes merging to form five to ten transversal stripes along the body. More specifically, this subspecies is also characterized by a rostral scale always in contact with three or more adjacent supralabials (100%), a low number of lamellae under the third (23.8 ± 0.9) and fourth (28.5 ± 2.1) toe and the highest number of femoral pores (28.6 ± 1.8) (see also Figs 4, 6H–J, Table 1).

Redescriptionoftheholotype: NHM 1946.8.30.20( Fig.6H), juvenile or subadult unsexed specimen preserved in 70% ethanol, in relatively good condition, with exception of a 3 cm long incision running along the ventral side of the body. SVL (155 mm) shorter than tail length (199 mm). Head 25.1 mm long (HL1), 23.4 mm high and 18.9 mm wide. Fourth finger length of 24.7/ 23.9 mm. Rostral scale in contact with two adjacent supra-supralabials (barely in point contact with the third (median) one). Mental separating the anteriormost infralabials. Eight supralabials on the right side, nine on the left side. Ten infralabials on both sides. Internasal and rostral scales separated by a row of five small granular scales. Four large and flat frontonasal scales, posterior to and in contact with the internasal. Subdigital lamellae 23/22 under the third toe, 26/24 under the fourth toe; 280 tranversal row of minute scales at midbody. Dorsal crest weakly developed, 16 spiny scales running along the dorsal side of the neck (Cnc), followed by a postnuchal gap of 11 very reduced scales (Cng), 85 spiny scales running along the dorsal side of the trunk (Cdc), then 141 scales on the dorsal side of the tail.

After more than 124 years of preservation in ethanol, original colour pattern still visible, although likely darker and less contrasted than originally. Background coloration of the dorsal and lateral sides of the whole body dark grey to blackish, with four to five transversal stripes made of aligned small brownish/ochre dots. Dorsal and lateral sides of the tail and of limbs uniformly dark grey. Dorsal and lateral sides of the head as dark as the rest of the body, with the largest scale of the parietal region being lighter. Crest spines as dark as the dorsum, with exception of a series of five consecutive olive/greyish spines of the nuchal crest, and few series of two to four consecutive brownish spines corresponding with the lighter transversal stripes of the dorsum. Ventral side light cream, darker on the anteriormost part and on the extremities; mental region, chest, the ventral sides of limbs and tail greyish; collar, palms and soles almost as dark as the dorsal side.