|Scientific Name:||Cyclura onchiopsis|
|Species Authority:||Cope, 1885|
Cyclura cornuta subspecies onchiopsis Cope, 1885
|Taxonomic Notes:||Cope (1885) used both Cyclura onchiopsis and Cyclura nigerrima; but only the former was diagnosed. Consequently, the latter must was a nomen nudum. Nearly a year later, Cope (1885 ) provided a diagnosis for C. nigerrima. Barbour (1937) relegated C. nigerrima to a subspecies of C. cornuta. Schwartz and Carey (1977) formally placed C. nigerrima in the synonymy of C. onchiopsis.
Originally described as a full species, the Navassa Rhinoceros Iguana was relegated to subspecific status within the Rhinoceros Iguanas (Cyclura cornuta) first by Cope (1885 ), without presenting any evidence other than superficial physical similarity. That status was contradicted by Barbour and Noble (1916), although Barbour (1937) later reverted to the subspecific designation. Carey (1977) recognized Cyclura onchiopsis as a full species, but most subsequent authorities followed Schwartz and Thomas (1975) in recognizing it as a subspecies. Powell (1999) re-elevated the taxon to full species status.
|Red List Category & Criteria:||Extinct ver 3.1|
|Reviewer(s):||Grant, T.D. & Hoffmann, M.|
No individuals of this iguana have been collected or observed since the middle of the 19th century, despite a number of visits to the island and its occupation during the early 20th century by a resident lighthouse keeper. Schwatrz and Carey (1977) suggested that the introduction of goats and/or cats by the lighthouse keepers might have been responsible for its extinction, but Powell (1999) indicated that exploitation by mine workers on the island during the latter half of the 19th century is a more probable explanation.
|Range Description:||The Navassa Rhinoceros Iguana was known only from Navassa Island, West Indies, a 5.2 km² island owned by the United States. The iguana presumably occurred island-wide before its extinction.|
Regionally extinct:Puerto Rico (Navassa I.)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||No individuals have been collected or observed since the middle of the 19th century. The last specimen collection date was July 1878.|
|Habitat and Ecology:||
Surrounded by cliffs, the portions of Navassa Island presumably capable of supporting iguanas prior to their extinction was characterized by Ekman (1929), Proctor (1959), and paraphrased in Powell (1999). The island is a relatively flat shelf of pot-holed, karstic dolomite covered by sparse, shrubby vegetation (largely the result of 19th century mining operations) with a second, higher plateau with apparently natural savannas as well as areas cleared during the mining operations, interspersed with dense but stunted woodland dominated by four tree species: Short Leaf Fig (Ficus populnea var. brevifolia), False Mastic (Sideroxylon foetidissimum), Pigeon Plum (Coccoloba diversifolia), and Poisonwood (Metopium brownei). Although iguanas probably occurred island-wide prior to their extinction, preferred habitat almost certainly consisted of rocky areas and savannas instead of the densely forested portions of the island. Because Navassa lacks beaches, nesting presumably occurred in pockets of mineralized phosphate that accumulated in potholes. The phosphate (which was commercially extracted during the period when the iguanas presumably became extinct) might have been either of marine or terrestrial origin: precipitates of seawater during periods of submergence or from fish digested by birds and deposited as guano, respectively.
Among the five specimens known for this iguana, the maximum snout-vent length is 42 cm for the largest male and 37.8 cm snout-vent length for the largest female (Powell 2000). Based on the morphology of similar species, this is probably far less than the maximum for this iguana.
|Major Threat(s):||Like other rock iguanas, the Navassa Rhinoceros Iguana was probably threatened by non-native predators, hunting for human consumption, and non-native competitors which destroyed the vegetation. Schwartz and Carey (1977) suggested that the introduction of goats and/or cats by the lighthouse keepers might have been responsible for its extinction, but Powell (1999) indicated that exploitation by mine workers on the island during the latter half of the 19th century was a more probable explanation.|
|Citation:||Powell, R. 2013. Cyclura onchiopsis. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 23 August 2014.|
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