A SYNOPSIS OF CAIMAN TAXONOMY Brian R. Warren INTRODUCTION: As an introduction to this discussion, I would like to outline present caiman taxonomy with reference to King and Burke (1997) as a standard. To simplify this task, I have summarized the current classification in a table (Figure 1, below). I will discuss Figure 1 in the context of ongoing research and modern concepts of systematic classification after a brief discussion of the history of caiman taxonomy. Figure 1. Current caiman classification, after King and Burke (1997) Genus species subspecies Caiman crocodilus (sclerops) crocodilus fuscus apaporiensis chiapasius latirostris yacare Paleosuchus trigonatus palpebrosus Melanosuchus niger Caiman crocodilus: The genus Caiman was first described by Spix in 1825, who designated two species, fissipes and niger, but, like many early authors, provided no type. Over a century later, Schmidt (1928) designated fissipes (=latirostris) as the type of the genus. The common caiman (Caiman crocodilus or sclerops) is still controversial, mostly because its original name was part of Linnaeus' blanket name for crocodilians, Lacerta crocodilus (1758). Medem (1981, 1983) and others have argued that because the name crocodilus was misapplied to all crocodilians, Schneider's original specific epithet, sclerops (1801), should be applied to this taxon. However, Lönnberg (1896) and Andersson (1900) showed that Linnaeus' type specimens for L. crocodilus were members of the taxon theretofore identified as Caiman sclerops (Schneider). Andersson proposed the use of the name Caiman crocodilus (L.), but the use of this name has remained contentious, largely due to the profound influence of Medem's work on caimans. It is worth noting that Hoogmoed and Gruber (1983:379) declared Medem's treatment of Caiman crocodilus as a nomen oblitum is invalid under Articles 23a-b of the Code. Caiman latirostris: The broad-snouted caiman, Caiman latirostris, like its possible close relative (see Poe 1996), the black caiman, Melanosuchus niger, has long been recognized as a unique taxon. Unfortunately, that doesn't mean the synonymy is any less chaotic. Daudin (1802) described several crocodilians as belonging to the genus Crocodilus. Among these were the yacare and latirostris taxa. Schmidt (1928) argued that Daudin's use of Crocodilus was a homonym of the senior Crocodylus Laurenti, according to Article 53 of the Code; however, I disagree with Schmidt's interpretation. Article 56 on genus-group homonyms clearly states that one-letter differences do not constitute homonymy. However, the recommendations in Appendix D, Section I.3 state that namers of taxa should avoid potentially-confusing names, such as those differing only by one letter. On this basis, I support Schmidt's conclusions, if not his arguments. The relevance of this point to C. latirostris is this: although the name Crocodilus is invalid, Daudin's description takes priority over Spix's. Therefore, the combination Caiman latirostris is more appropriate, according to the Rules, than is Caiman fissipes. Freiberg and Carvalho (1965) described two subspecies of C. latirostris, but these were collapsed by the work of Crea et al. (1989). Caiman yacare: The combination Caiman yacare (Daudin) first appears in Schmidt (1928), who points out that, although many early authors did not recognize this caiman as distinct from sclerops (=crocodilus), it is clearly the taxon referred to by Daudin in his description of Crocodilus yacare. Some authors still contend that the yacare caiman is a subspecies of the common caiman (e.g., Caiman crocodilus yacare). Caiman crocodilus subspecies: There are a few other putative subspecies of Caiman crocodilus worth mentioning. The apaporiensis caiman was described by Medem in 1955. He referred to its type locality as being in the upper Rio Apaporis, between the falls of Jirijimo and Puerto Yaviya. There is no synonymy beyond Medem's consistent use of Caiman sclerops to refer to spectacled caimans. The brown caiman (C. crocodilus fuscus) was first described by Cope (1868) as Perosuchus fuscus. Subsequent authors did not deem it sufficiently different from other spectacled caimans to warrant its own generic epithet. It is worth noting that, although Cope described his Perosuchus as lacking a supraorbital ridge, his description was based on a single juvenile obtained by the Academy of Natural Sciences of Philadelphia, and therefore he could easily have been mistaken on this point. Boulenger (1889) and Vaillant (1898) both considered this taxon to be part of sclerops. It is typically distinguished from other forms of Caiman crocodilus by a tan to olive brown coloration, hence its common name. This caiman has a range that extends through parts of Mexico, Central America, Colombia and Venezuela. Some authors refer to the caiman of Mexico and Central America as a separate subspecies (Caiman crocodilus chiapasius); the chiapasius name originated with Bocourt in 1876 and is in the synonymy of fuscus. A final note about subspecies: My master's thesis work involves examining the phylogenetic relationships among caimans, including the putative subspecies of C. crocodilus. As a proponent of a species concept based on the idea that evolution is important and that species are real, evolving entities (see Cracraft 1989, Frost and Kluge 1994, Hull 1976, et cetera), I reject the reality of subspecies. As a result, if I find distinct genetic differences among the caimans referred to as subspecies, I will consider this sufficient evidence to elevate these taxa to species rank; I will make the appropriate recommendations in my thesis and publications resulting from it. I hope, therefore, that my work will help to clarify some of the present murkiness surrounding caiman taxonomy. Melanosuchus niger: As I alluded to earlier, the black caiman has had a confusing nomenclatural history despite the fact that it has been recognized since it was first described as a unique crocodilian. Spix described the black caiman as Caiman niger in 1825 along with several other caimans. It has also been historically associated with many other generic names, including Alligator. Perhaps the most bizarre of these taxonomic decisions was that of Vaillant to transfer niger to his Jacaretinga, making it congeneric with the dwarf caimans. In his review, Schmidt (1928) retained Spix's name, although he believed that there were sufficient differences between the black caiman and other caimans placed in Spix's genus to warrant placing it in another genus. It is interesting that Schmidt refrained from doing so because it would ignore the uniqueness of the broad-snouted caiman, which he also retained in Spix's Caiman; recent analyses by Poe (1996) indicate that these two taxa may be sisters, and implies that Melanosuchus should be returned to the genus Caiman. Paleosuchus: The dwarf or smooth-fronted caimans were reviewed by Medem (1958). The specific epithets of the caimans, palpebrosus and trigonatus, follow the first descriptions by Cuvier and Schneider, respectively. Both were originally described as members of the now-defunct genus Crocodilus. Paleosuchus was first proposed by Gray (1862) as a subgenus of Caiman and included only Schneider's trigonatus. Müller (1924) pointed out that Laurenti's (1768) figure of Crocodylus niloticus (the Nile crocodile) is in fact a smooth-fronted caiman, specifically Schneider's smooth-fronted caiman (cf., P. trigonatus). This revealed a problem. Later, Mller published a revision, assigning C. niloticus to the taxon formerly known as Caiman trigonatus (subgenus Paleosuchus) Gray and thereby, as noted by Schmidt (1928), wreaking havoc on crocodilian nomenclature. While Müller was certainly justified under the auspices of the Code in making the name change, Schmidt (1928) correctly (in my opinion) argued that to follow Müller would result in such chaos that the ICZN should invoke its plenary powers (as per Article 79) to rectify the situation. In the interim, Schmidt opted to follow Gray (1862), except that he considered the smooth-fronted caimans "generically-distinct," and for this reason, used Paleosuchus as their generic name. It is worth noting that Schmidt was the first worker to use the combination of generic and specific epithets in common use today. In his review, Medem agreed that Müller's recommendations would be disastrous and "should under no circumstances be followed (1958: 228)." CONCLUSION: In conclusion, therefore, what can we say about caiman taxonomy? I have illustrated some of the circuitous routes we have taken to arrive at our present caiman nomenclature. According to a recent analysis by Poe (1996), the generic distinctness of Melanosuchus may be questionable. The black and broad-snouted caimans were found to be sister taxa in a combined analysis of available phylogenetic data on caiman relationships. The black caiman was Spix's "other Caiman," Caiman niger. This name has priority over Werner's Melanosuchus, and, as Poe suggested, should be applied to this taxon. Beyond this change, and my current investigation into the nature of the Caiman crocodilus subspecies, caiman taxonomy has achieved some degree of stability, as most crocodilian biologists accept the names of the dwarf caimans and the common caiman. On the other hand, in the absence of a universally-accepted phylogenetic-based taxonomic system (and a pragmatic viewpoint dictates that such an absence will always exist), stability in terms of the number of caimans recognized by specific or subspecific nomenclature will remain elusive. As more and more systematists come to accept the relatively new ideas about evolutionary unit-based species concepts, I anticipate that more people will be publishing traditional taxonomic revisions side-by-side with revisions in accordance with a phylogenetic taxonomy system akin to that proposed by de Queiroz and Gauthier in several papers (1990, 1992, 1994). For example, under such a system taxa like Gavialis gangeticus and Tomistoma schlegelii, whose suprageneric affinities are uncertain, would simply be placed under the family Crocodylidae [including all crocodilians] until such time as their relationships are resolved in a more lucid fashion. Recent papers (Bryant 1994, 1996; Bryant et al. 1993; Cantino et al. 1997) have revealed the utility of such a system, and I anticipate that nomenclatural bodies like the ICZN will eventually adopt this new taxonomy. LITERATURE CITED Andersson, L.G. 1900. Catalogue of the Linnean Type-Specimens of Linnaeus' Reptilia. Bihang K. Vet.-Akad. Handl., XXVI, Afd. IV, No. 1, pp. 1-29. [cited in Mook and Mook 1940] Bocourt, F. 1876. Note sur qulques reptiles de l'Isthme de Tehuantepec (Mexique) donnes par M. Sumichrast au museum. Journal de Zoologie. Paris. 5(5-6): 386-411. [cited in Mook and Mook 1940, King and Burke 1997] Boulenger, G. A. 1889. Catalogue of the Tortoises, Crocodiles, and Amphisbaenians in the Collection of the British Museum. British Museum, London. [cited in Mook and Mook 1940] Bryant, H.L. 1994. Comments on the phylogenetic definition of taxon names and conventions regarding the naming of crown clades. Syst. Biol. 43: 124-130. Bryant, H.L. 1996. Explicitness, Stability, and Universality in the Phylogenetic Definition and Usage of Taxon Names: A Case Study of the Phylogenetic Taxonomy of the Carnivora (Mammalia). Syst. Biol. 45: 174-189. Bryant, H.L., A.P. Russell, and W.D. Fitch. 1993. Phylogenetic relationships within the extant Mustelidae (Carnivora): Appraisal of the cladistic status of the Simpsonian subfamilies. Zool. J. Linn. Soc. 108: 301-334. Cantino, P.D., R.G. Olmstead, and S.J. Wagstaff. 1997. A Comparison of Phylogenetic Nomenclature with the Current System: A Botanical Case Study. Syst. Biol. 46: 313-331. Cope, E. D. 1868. On the Crocodilian Genus Perosuchus. Proceedings of the Academy of Natural Sciences of Pennsylvania 1868: 203. Cracraft, J. 1989. Speciation and its ontology: The empirical consequences of alternative species concepts for understanding patterns and process of differentiation. Pages 28-59 in D. Otte and J. A. Endler,eds. Speciation and Its Consequences. Sinauer Associates, Sunderland, MA. Crea, M., J. Merler, and R. Quintana. 1989. Contribucion a la sistematica de Caiman latirostris (Daudin, 1802) (Crocodylia, Alligatoridae). An. Mus. Hist. Nat. Valparaiso. 20: 75-80. Daudin, F.M. 1802. Histoire Naturelle, Generale et Particuliere des Reptiles. Paris. [cited in Mook and Mook 1940] De Queiroz, K. and J. Gauthier. 1990. Phylogeny as a central principle in taxonomy: Phylogenetic definitions of taxon names. Syst. Zool. 39: 307-322. De Queiroz, K. and J. Gauthier. 1992. Phylogenetic taxonomy. Ann. Rev. Ecol. Syst. 23: 449-480. De Queiroz, K. and J. Gauthier. 1994. Toward a phylogenetic system of biological nomenclature. Trends. Ecol. Evol. 9: 27-31. Freiberg, M.A. and A.L. Carvalho. 1965. El yacare sudamericano Caiman latirostris (Daudin). Physis 25: 351-360. Frost, D. R. and A.G. Kluge. 1994. A Consideration of Epistemology in Systematic Biology, With Special Reference to Species. Cladistics 10: 259-294. Gray, J. E. 1862. A synopsis of the species of alligators. Annals and Magazine of Natural History 3: 327-331. Hoogmoed, M.S. and U. Gruber. 1983. Spix and Wagler type specimens of amphibians and reptile sin the Natural History Musea in Munich (Germany) and Leiden (The Netherlands). Spixiana Suppl. 9: 319-415. Hull, D. L. 1976. Are Species Really Individuals? Systematic Zoology 25: 174-191. International Commission on Zoological Nomenclature. 1985. International Code of Zoological Nomenclature. 3rd ed. University of California Press, Berkeley. King, F. W., and R.L. Burke. 1997. Checklist of the Crocodilians, Tuatara, and Turtles of the World (Crocodilians + References). UF Web, Gainesville, FL. Laurenti, J. N. 1768 (reprint 1966). Genus XV: Crocodylus. Pages 53-55. Synopsin Reptilium. A. Asher and Co., Amsterdam. Linnaeus, C. 1758. Systema Naturae. 10th ed. [cited in Mook and Mook 1940] Lönnberg, E. 1896. Linnean Type-Specimens. Bihang K.Vet.-Akad. Handl., XXII., Afd. IV, No. 1, pp. 1-45. [cited in Mook and Mook 1940] Medem, F. 1955. A New Subspecies of Caiman sclerops from Colombia. Fieldiana Zoology 37: 339-344. Medem, F. 1958. The Crocodilian Genus Paleosuchus. Fieldiana Zoology 39: 227-247. Medem, F. 1981. Nomenclatura. Pages 53-64. Los Crocodylia de Sur America Vol. I: Colombia. Ministerio de Educacion Nacional, Bogota. Medem, F. 1983. Nomenclatura. Pages 23-29. Los Crocodylia de Sur America Vol. II. Ministerio de Educacion Nacional, Bogota. Mook, C. C. and G. E. Mook. 1940. Some Problems in Crocodilian Nomenclature. American Museum Novitates 1098: 1-10. Müller, L. 1924. Zur Nomenklatur der sudamerikanischen Kaiman-Arten. Zoologischer Anzeiger 58: 314-319. Poe, S. 1996. Data Set Incongruence and the Phylogeny of Crocodilians. Systematic Biology 45: 393-414. Schmidt, K. P. 1928. Notes on South American Caimans. Field Museum of Natural History Zoological Series 12: 205-231. Schneider, J.G. 1801. Historiae Amphibiorum naturalis et literariae. Fasc. 2, pp. 1-364, pl. 1-2. [cited in Schmidt 1928] Spix, J.W. de. 1825. Animalia nova sive species novae lacertarum, quad in itenere per Braziliam annis MDCCCXVII-MDCCCXX jussu et aspiciis Maximiliani Josephi I. Bavariae Regis suscepto collegit et descripsit. Monachii: Typa Frac. Seraph. Hubaschmanni. 4to. pp. 1-26, pl. 1-28. [cited in Schmidt 1928] Vaillant, L. 1898. Contribution a l'etude des Emydosauriens. Nouv. Arch. Mus. Hist. Nat., (Ser 3.) X, pp. 143-212. [cited in Mook and Mook 1940] Glossary of Arcane Terminology genus - group of species sharing a common evolutionary history; pl. genera; also generic name/epithet homonymy - relationship between or among homonyms (two or more names of the same rank of the same or very similar spellings which denote different taxa) nomen oblitum - forgotten name, as applied by earlier editions of the Code between 1961 and 1973 priority - nomenclatural principle stating that the valid name of a taxon is the name originally applied (in its original description), unless that name is considered invalid under any article of the Code species - a cohesive group of organisms on its own evolutionary trajectory, usually distinguished by one or more fixed character traits; also referred to herein as a taxon (pl. taxa) subspecies - a distinctive group of organisms within a species; an invalid concept in phylogenetics synonymy - a list of synonyms (two or more names of the same rank used to denote the same taxon) taxon - see species Intrigued? 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