The Central African slender-snouted crocodile (''Mecistops leptorhynchus'') is one of two

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...

s in the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Mecistops ''Mecistops'' is a genus of crocodiles, the slender-snouted crocodiles, native to sub-Saharan Africa. Taxonomy and etymology Traditionally placed in ''Crocodylus'', recent studies in DNA and morphology have shown that it is in fact basal to ' ...

''. It was once thought to be a

population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...

of the

West African slender-snouted crocodile The West African slender-snouted crocodile (''Mecistops cataphractus''), or slender-snouted crocodile, is a critically endangered species of African crocodile. It is one of five species of crocodile in Africa, the other four being the Central A ...

(''Mecistops cataphractus'') but was elevated to a species after two detailed studies, one in 2014 and the other in 2018. The species was described in 1835 on the basis of a specimen that had died at the

London Zoo London Zoo, also known as ZSL London Zoo or London Zoological Gardens is the world's oldest scientific zoo. It was opened in London on 27 April 1828, and was originally intended to be used as a collection for science, scientific study. In 1831 o ...

and had been claimed to have been collected in the Fernando Po. Studies of specimens and their molecular sequences established that there were two different species which occurred in distinct hydrological zones. ''M. leptorhynchus'' is easily differentiated morphologically from ''M. cataphractus'' by the absence of a round tubercle or boss on the squamosal scale at the back of the head in the former and present in the latter.

Etymology

The generic name ''Mecistops'' is most probably derived from the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

words μήκιστ (''mēkist'' ) meaning "longest" and ὄψις (ópsis) meaning "aspect" or "appearance". The specific name ''leptorhynchus'' is derived from the Ancient Greek words λεπτός (''leptós'') meaning "slender" and ῥύγχος (''rhýnchos'') meaning "snout".

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(1835) may have named the species so because he found it had a longer head width:head length ratio than ''M. cataphractus'', 3:1 versus 2.5:1. Although an analysis of 93 skulls, mainly belonging to mature individuals, by Shirley et al. (2018) found a head width:head length ratio of 2.25:1 for ''M. cataphractus'' and 2.37:1 for ''M. leptorhynchus''.

Taxonomy

Gray Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...

(1844) listed ''Mecistops leptorhynchus'' as a

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

of ''M. bennettii'' even though the former has temporal priority. ''M. bennettii'' was subsumed as a junior synonym of ''M. leptorhynchus'' in Gray's Synopsis of the Species of Recent Crocodilians as he found that the

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

of ''M. bennettii'' ( NHMUK 1977.444) is actually an adult ''M. leptorhynchus''. The

International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the ...

(ICZN) does not allow the

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

(species name) to be changed upon removal to a new genus unless it already exists in the new genus. Since ''Mecistops'' was a new genus at the time of its description, ''M. bennettii'' is a

nomen novum In biological nomenclature, a ''nomen novum'' (Latin for "new name"), new replacement name (or replacement name, new substitute name, substitute name) is a scientific name that is created specifically to replace another scientific name, but only w ...

(replacement name). Shirley et al. (2018) found that the type specimen of ''M. bennettii'' is morphologically and geographically readily assignable to ''M. cataphractus'' so they synonymized ''M. bennettii'' with ''M. cataphractus''. Shirley et al. (2018) also designated ''M. cataphractus'' as the type species of ''Mecistops'' in accordance with Articles 69 and 70 of the ICZN. Article 67.9 of the ICZN states "If a validly fixed

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

is later found to have been misidentified, the provisions of Article 70.3 apply." Article 70.3 in turn states "If an author discovers that a type species was misidentified, the author may select, and thereby fix as type species, the species that will, in his or her judgment, best serve stability and universality, either." ''M. cataphractus'' best serves stability because it is the most well-studied species of ''Mecistops'' with the most readily recognizable and assignable type material. It also has the widest use in the scientific literature.

Distribution

Central African slender-snouted crocodile occurs widely in

Central Africa Central Africa is a subregion of the African continent comprising various countries according to different definitions. Angola, Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, the Republic of the Congo, ...

(Cameroon, Equatorial Guinea, Gabon, northern Angola, Central African Republic, Republic of the Congo, Democratic Republic of the Congo) and extends into South Sudan in

East Africa East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa: Due to the historical ...

References

{{Taxonbar, from=Q57783121 Crocodylidae Crocodilians of Africa Reptiles of Angola Reptiles of Cameroon Reptiles of the Central African Republic Reptiles of the Democratic Republic of the Congo Reptiles of Equatorial Guinea Reptiles of Gabon Reptiles of the Republic of the Congo Reptiles of South Sudan Reptiles described in 1835 Taxa named by Edward Turner Bennett