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PHOTOGRAPHY: REPTILIA: CROCODYLIA
CROCODYLIA CROCODILES & ALLIGATORS
How many crocodilians are there?
The usual answer is 23 species, but is that correct ?
There are certainly 23 long established species in three families: Alligatoridae: Alligator mississippiensis;A.sinensis; Caiman crocodilus; C.latirostris; C.yacare; Melanosuchus niger; Paleosuchus palpebrosus; P.trigonatus = 8 alligators and caiman. Crocodilidae: Crocodylus acutus; C.intermedius; C.johstonei; C.mindorensis; C.moreletii, C.niloticus; C.novaeguineae; C.palustris; C.porosus; C.rhombifer; C.siamensis; Mecistops cataphractus*; Osteolaemus tetraspis = 13 crocodiles. Gavialidae: Gavialis gangeticus; Tomistoma schlegeli** = 1 true gharialand 1 false gharial.
Total = 23, or does it?
* The African slender-snouted crocodile, formerly known as Crocodylus cataphractus, has been shown to belong to neither of the genera Crocodylus or Osteolaemus, resulting in the resurrection of Mecistops (Gray, 1844) fide Schmidt et al 2003. ** Whether Tomistoma belongs in the Gavialidae or the Crocodilidae is a moot point with regards to this species count.
Crocodylus acutus: This widespread crocodile is found from southern Florida, through the Caribbean to the coasts of Venezuela and Colombia. I also occurs on the Caribbean coast of Mexico and even the Pacific coast of Mexico, which means the population in the Pacific must have reached the area before the closure of the Isthmus of Panama (aka Isthmus of Darien) three million years ago. This degree of isolation could have resulted in genetic divergence within the species, especially as some authorities consider the Jamaican population, slam bang in the middle of the range, to be genetically different from other Caribbean populations.
Crocodylus niloticus: Another widely distributed species found throughout Africa and the island of Madagascar, with seven subspecies and the subspecies from the Sahara and northwest Africa being recently elevated to specific status as C.suchus (Schmitz et al 2003).
Crocodylus novaeguineae: The New Guinea freshwater crocodile is found in several separated river systems and these populations may be genetically separate. In addition crocodiles living in freshwater are reported from New Britain and Palau and although these may be populations of Saltwater crocodile (C.porosus) there is the possibility that other freshwater crocodile taxa exist in this understudied region. It is worth noting that the Philippine crocodile (C.mindorensis) was formerly treated as a subspecies of C.novaeguineae.
Crocodylus raninus: This species is frequently missed off lists although it was included by Martin (2008) in his total of 24 species of crocodilians. First described as a subspecies of the Saltwater crocodile (C.pororus, then C.biporcatus) in 1844, the Borneo crocodile was virtually forgotten until Ross (1990, 1992) resurrected the name for two preserved juvenile specimens, and in 1993 Cox, Frazier and Maturbongs reported live specimens from Kalimantan, Borneo, which were clearly not specimens of other Borneo crocodilians (C.porosus, T.schlegelii) nor of mainland Southeast Asian crocodilians (C.palustris, C.siamensis). It is clear a 24th species of crocodilian exists in eastern Borneo, although its conservation status in the wild could give cause for concern since all the live specimens were in villages or crocodile farms.
Osteolaemus tetrapis: Long considered to contain two subspecies: the nominate form from the Ogooué Basin (southern Cameroon, Gabon and Equatorial Guinea) and West Africa, and the subspecies O.t.osborni, from the Congo Basin, a recent paper (Eaton et al 2009) not only elevates the Congo Basin taxa to specific status, but also highlights the presence of a two species in the formly wide-ranging West African O.tetrapis. Since the Ogooué Basin is the type-locality for O.tetraspis, the situation leaves the West African taxa without a name.
Even before any taxonomic consideration of C.acutus and C.novaeguineae, the actions above relating to C.suchus, C.raninus and Osteolaemus already elevate the total crocodilian species count to 27 in nine genera. The photo library contains images of 22 species (25 taxa) from seven of the nine genera.
Cox, J.H., R.S.Frazier and R.A.Maturbongs 1993 Freshwater crocodiles of Kalimantan (Indonesian Borneo). Copeia 1993(2):564-566.
Eaton, M.J., A.Martin, J.Thorbjarnarson and G.Amato 2009 Species-level diversification of African dwarf crocodiles (Genus Osteolaemus) : A geographic and phylogenetic perspective. Molecular Phylogenetics and Evolution. 50:496-506.
Martin, S. 2008 Global diversity of crocodiles (Crocodilia, Reptilia) in freshwater. Hydrobiologia 595:587-591.
Schmitz, A., P.Mausfeld, E.Hekkala, T.Shine, H.Nickel, G.Amato and W.Böhme 2003 Molecular evidence for species level divergence in African Nile Crocodiles Crocodylus niloticus (Laurenti, 1786) C. R. Palevolution 2: 703–712.
Ross, C.A. 1990. Crocodylus raninus S. Müller and Schlegel, a valid species of crocodile (Reptilia: Crocodylidae) from Borneo. Proceedings of the Biological Society of Washington, 103 (4): 955-961.
Ross, Charles A. 1992. Designation of a lectotype for Crocodylus raninus S. Müller & Schlegel, 1844 (Reptilia: Crocodylidae), the Borneo crocodile. Proceedings of the Biological Society of Washington, 105 (2): 400-402.
Photographic locality. Wherever possible precidence is given to wild specimens from known localitions, wherein the 'photographic locality' relates to the origin of the photographed specimens, rather than the taxon's entire range. The only exceptions are indicated by (captive) or (preserved specimen). These are either specimens photographed in captivity, where the locality given is a general distribution for the taxon, or preserved specimens photographed as biological voucher specimens.
Column D1. Digitized images - the bulk of the library consists of 35mm transparencies (mostly Kodachrome or Velvia) which are gradually being digitized [using Nikon CoolScan 4000 or Plustek OpticFilm 7600i] and stored on hard disc. 'X' indicates that digitized images are available, '' indicates that the transparencies of this taxon have yet to be digitized.
Column D2. Digital images - since 2005 digital images have also been taken [using Canon EOS 30D, 40D or 7D]. 'X' indicates that digital images are available in addition to digitized images for this taxon.
ALLIGATORIDAE ALLIGATORS & CAIMAN
The Alligatoridae contains eight species, in four genera, with seven species (eight taxa) represented in the photo library.
Alligatoridae Alligators & caiman
CHINESE ALLIGATOR Alligator sinensis
Yangze River, China
BLACK CAIMAN Melanosuchus niger
Karanambo, Rupununi River, Guyana