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Cape Verde giant skink

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Cape Verde giant skink
Illustration, 1885

Extinct (1940)  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Scincidae
Genus: Chioninia
Species:
†C. coctei
Binomial name
†Chioninia coctei
Synonyms[2]
  • Euprepes coctei
    A.M.C. Duméril & Bibron, 1839
  • Macroscincus coctei
    — Bocage, 1873
  • Gongylus coctei
    — Frank & Ramus, 1995
  • Chioninia coctei
    — Miralles et al., 2010

The Cape Verde giant skink (Chioninia coctei), also called Bibron's skink, Cocteau's skink, and lagarto in Cape Verdean Portuguese, is a recently extinct species of large lizard (skink) that was endemic to some of the Barlavento Islands of Cape Verde before disappearing in the 20th century.

Taxonomy

Two preserved specimens at Museo delle Scienze, Trento

The Cape Verde giant skink was first given the specific name Euprepes coctei by French zoologists André Marie Constant Duméril and Gabriel Bibron in 1839. The holotype was a specimen at the National Museum of Natural History in Paris, one of five collected in 1784 by João da Silva Feijó in Ilhéu Branco, taken to Lisbon, and later looted by the Napoleonic Army in 1808.[3] The name coctei honors French physician and zoologist Jean-Théodore Cocteau (1798–1838).[4] Since Duméril and Bibron ignored the history of the specimen, they listed its origin as "the coast of Africa" and the species remained in obscurity until it was rediscovered in 1873 by Cape Verdean doctor Frederico Hopffer.[3] Portuguese zoologist José Vicente Barbosa du Bocage assigned the species to its own monotypic genus, Macroscincus (lit. "large skink").[5]

In 2001, a Mitochondrial DNA study nested Macroscincus within a group of several Cape Verdean skink species assigned to the wastebasket genus Mabuya, suggesting a common origin in West Africa during the Late Miocene or Early Pliocene, dispersal to Cape Verde and subsequent adaptive radiation.[6] The phylogeny of Mabuya was resolved in 2016, placing Cape Verdean skinks in the genus Chioninia, establishing Trachylepis of Africa and Madagascar as its sister genus, and limiting Mabuya to the Neotropics.[7]

Description

The Cape Verde giant skink was very large and robust. Adults could attain a snout-to-vent length (SVL) of 32 cm (13 in).[8] The tail was less than half the length of the body.[9] It was described as prehensile and powerful, well adapted to climb trees, which surprised 19th century scientists who only knew Cape Verde giant skinks from denuded, arid islets.[3] However, other authors noted that the species was capable of autotomy, which would be contradictory for a prehensile tail. The long digits, equivalent to a SENI (Scincidae Ecological Niche Index) value of 0.13, are consistent with a low canopy arboreal niche.[9]

The teeth were located labiolingually, compressed, multicuspate,[8] pleurodontid and pterygoid.[9]

There were three color morphs: grey, yellow, and intermediate. There was no banding but the body had dark stippled blotches and freckles with a yellow green-grey standard background. The underside was largely devoid of freckles, with a solid color lighter than the back. Dorsal scales were small and keeled in more than one hundred rows at the midsection but the osteodermal covering was less developed than in other skinks. The lower eyelid had a unique transparent "window" below.[9]

Males reached their maximum size quicker than females, had a larger head, more robust jaws, and longer hindlegs. Older males had thick, hanging dewlaps that are unusual for skinks.[9]

Distribution

Subfossil remains of Cape Verde giant skink were found in the northwestern islands of São Vicente and Santa Luzia, and the islets Branco and Raso, which along with the smaller islet Pássaros were united into the paleoisland "Mindelo" during the colder stages of the Pleistocene.[3] Testimonies of local fishermen also place giant skinks in São Nicolau island, but this remains unproven.[1] São Nicolau was not connected by land to other islands during the Pleistocene.[3]

Behaviour and ecology

Restoration of a Cape Verde giant skink on a rock of Branco or Raso, with other species native to the islands like giant wall gecko, Raso lark, and a shearwater.

The behavior of the Cape Verde giant skink is largely unknown due to the lack of ethology studies before its extinction, though convergent evolution has been noted with two extant species: the African striped skink (Trachylepis striata) from southern and eastern Africa, adapted to a low canopy arboreal niche, and Vaillant's mabuya (Chioninia vaillanti), another large, herbivorous skink that is endemic to the southern Sotavento Islands of Cape Verde.[8]

The transparent lower eyelid may have been an adaptation to spot predators below while giant skinks slept on the lower canopy with their eyes closed. In that case the predator's extinction would have long preceded the Cape Verde giant skink's own. The need of light for this strategy would indicate that the giant skink was crepuscular and slept during the day.[9] The barn owl is known to have eaten skinks before and after human arrival.[3] The unusual dewlap of old males could have played some role in territoriality.[9]

The Cape Verde giant skink's long digestive track, abundant and varied helminthic community, and specialized dentition were well suited for a vegetarian diet.[3] Although most animals died early in captivity, some survived for years on a diet of fruit and vegetation. One was noted as eating a bird.[9] In Branco and Raso which are largely denuded of vegetation, the giant skinks adapted to live among large shearwater and petrel colonies and survived eating their regurgitations, feces, carrion, eggs, and hatchlings. Bones of skinks and seabirds are commonly mixed together.[3]

Preserved giant skinks have belly-button slits indicative of viviparous matrotrophy, yet a captive female was documented as laying a clutch of seven eggs over fifteen days in 1891, purely white colored and 1 1/2 inches in diameter. Other eggs are preserved at the Regional Museum of Turin. It is possible that the species used both modes of reproduction, like the sheen skink (Eugongylus albofasciolatus), where a female was documented alternating between them.[9]

Extinction

The "Mindelo" island broke up when sea levels rose at the end of the Pleistocene, fragmenting the Cape Verde giant skink's population. The local climate also became more arid, replacing the primitive forest with shrub savanna. This increased after the Portuguese arrived in 1461, cut down the remaining tamarisk trees for firewood and construction, and introduced goats that ate the other vegetation. They also introduced mice, cats, and dogs, that ravaged the seabird colonies. Historical landfills show that settlers also ate skinks themselves, but only occasionally and more rarely than seabirds. Studies of owl pellets show that Santa Luzia owls went from commonly hunting skinks before settlement to not hunting any after 1673, evidencing that they had become very rare in the island by then.[3]

References

  1. ^ a b Vasconcelos, R. (2013). "Chioninia coctei ". IUCN Red List of Threatened Species. 2013: e.T13152363A13152374. doi:10.2305/IUCN.UK.2013-1.RLTS.T13152363A13152374.en. Retrieved 12 November 2021.
  2. ^ Species Chioninia coctei at The Reptile Database www.reptile-database.org.
  3. ^ a b c d e f g h i Mateo, J. A., Barone, R., Hernández-Acosta, C. N., & López-Jurado, L. F. (2020) La muerte anunciada de dos gigantes macaronésicos: el gran escinco caboverdiano, Chioninia coctei (Duméril & Bibron, 1839) y el lagarto de Salmor, Gallotia simonyi (Steindachner, 1889). Bol. Asoc. Herpetol. Esp. Vol. 31 (2), pgs. 3-30.
  4. ^ Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. ISBN 978-1-4214-0135-5. (Macroscincus coctei, p.56).
  5. ^ Bocage, J.V.B. (1873) Sur l' habitat et les caractères zoologiques du "Macroscincus coctei" ("Euprepes coctei " Dum. et Bibr.). Jornal de Sciencias Mathemáticas, Physicas e Naturais, 4: 295–306.
  6. ^ Carranza, S.; Arnold, E.N.; Mateo, J.A.; López-Jurado, L.F. (2001). "Parallel gigantism and complex colonization patterns in the Cape Verde scincid lizards Mabuya and Macroscincus (Reptilia: Scincidae) revealed by mitochondrial DNA sequences". Proceedings of the Royal Society B: Biological Sciences. 268 (1476): 1595–603. doi:10.1098/rspb.2001.1699. PMC 1088783. PMID 11487407.
  7. ^ Karin, B. R., Metallinou, M., Weinell, J. L., Jackman, T. R., & Bauer, A. M. (2016). Resolving the higher-order phylogenetic relationships of the circumtropical Mabuya group (Squamata: Scincidae): An out-of-Asia diversification. Molecular phylogenetics and evolution, 102, 220-232.
  8. ^ a b c Greer AE (1976). "On the evolution of the giant Cape Verde scincid lizard Macroscincus coctei ". Journal of Natural History. 10 (6): 691–712. doi:10.1080/00222937600770551.
  9. ^ a b c d e f g h i Schnirel, Brian L. (May 2004). "SENI biometric analysis on the extinct Scincidae species: Macroscincus coctei ". Polyphemos (Florence, South Carolina) 1 (2): 12–22.

Bibliography

  • Adler GH, Austin CC, Dudley R (1995). "Dispersal and speciation of skinks among archipelagos in the tropical Pacific ocean". Evolutionary Ecology 9: 529–541.
  • Austin CC (1995). "Molecular and morphological evolution in south Pacific scincid lizards: morphological conservatism and phylogenetic relationships of Papuan Lipinia (Scincidae)". Herpetologica 51: 291–300.
  • Day, David (1979). Vanished Species. London: Gallery Books. pp. 254–255.
  • Duméril AMC, Bibron G (1839). Erpétologie générale ou Histoire naturelle complète des Reptiles. Tome cinquième. [= General Herpetology or Complete Natural History of the Reptiles. Volume 5]. Paris: Roret. viii + 854 pp. (Euprepes coctei, new species, pp. 666–668). (in French).
  • Grzimek, Bernhard (1975). Grzimek's Animal Life Encyclopedia. Volume 6, Reptiles. New York: Van Nostrand- Reinhold Company. pp. 178–179 .
  • Hartdegen, Ruston W. (September 2003). "The green tree skink". Reptiles Magazine (Boulder, Colorado) 11 (9): 42–50.
  • Honda M, Ota H, Kobayashi M, Nabhitabhata J, Yong H-S, Hikida T (1999). "Evolution of Asian and African Lygosomine Skinks of the Mabuya Group (Reptilia: Scincidae): A Molecular Perspective". Zoological Science 16 (6): 979–984.
  • Love, Bill (January 2003). "Mystery skink. Herpetological quiries". Reptiles Magazine 11 (1): 12.
  • Pether, Jim (April 2003). "In search of Macroscincus coctei ". Reptiles Magazine 11 (4): 70–81.
  • de Vosjoli, Phillippe; Fast, Frank (1995). "Account from the Daily journals of Phillippe de Vosjoli". The Vivarium (Escondido, California) 6 (5): 4–7, 12–17, 36–38, 40–44.
  • de Vosjoli, Phillippe; Fast, Frank (1995). "Notes from a herpetological field trip to New Caledonia (Part II) – Notes on three species of New Caledonian geckos of the Genus Rhactodactylus ". The Vivarium 6 (6): 26–29, 53–54.
  • Walls, Jerry G. (1994). Skinks: identification, care, and breeding. Neptune City, New Jersey: T.F.H. Publications. pp. 52–58.
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