''Cryptonanus'' is a
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 ...
of
opossum
Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North ...
s from South America. It includes five
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 ...
found from
Bolivia
, image_flag = Bandera de Bolivia (Estado).svg
, flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center
, flag_alt2 = 7 × 7 square p ...
to
Uruguay
Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...
and eastern
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, one of which is now
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
. Although the first species were discovered in 1931, the genus was not recognized as distinct from ''
Gracilinanus
''Gracilinanus'' is a genus of opossum in the family Didelphidae. It was separated from the genus ''Marmosa
The 27 species in the genus ''Marmosa'' are relatively small Neotropical members of the family Didelphidae. This genus is one of t ...
'' until 2005. It includes small opossums with generally grayish, sometimes reddish, fur that are mainly distinguished from other opossums by characters of the skull.
Taxonomy
Species of ''Cryptonanus'' were first described in 1931 by
George Henry Hamilton Tate
George Henry Hamilton Tate (April 30, 1894 – December 24, 1953) was a British-born United States, American zoologist and botanist, who worked as a mammalogist for the American Museum of Natural History in New York City. In his lifetime he wro ...
,
[Voss et al., 2005, p. 5] who described ''Marmosa microtarsus guahybae'' (now ''
Cryptonanus guahybae'') as a
subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
of ''Marmosa microtarsus'' (now ''
Gracilinanus microtarsus
The Brazilian gracile opossum (''Gracilinanus microtarsus'') is a species of small opossum from Brazil.
Description
Brazilian gracile opossums are relatively small opossums, with males ranging from and females from in head-body length. The tai ...
''), ''Marmosa agilis chacoensis'' (now ''
Cryptonanus chacoensis'') as a subspecies of ''Marmosa agilis'' (now ''
Gracilinanus agilis''),
[Tate, 1931, p. 10] and ''Marmosa unduaviensis'' (now ''
Cryptonanus unduaviensis'') as a separate species.
[Tate, 1931, p. 11] In 1943, another species was described, ''Marmosa agricolai'' (now ''
Cryptonanus agricolai'').
[Gardner, 2009, p. 41] Species of ''Cryptonanus'' were then included in a broadly defined genus ''
Marmosa
The 27 species in the genus ''Marmosa'' are relatively small Neotropical members of the family Didelphidae. This genus is one of three that are known as mouse opossums. The others are '' Thylamys'' (the "fat-tailed mouse opossums") and '' Tlacua ...
'' until the genus ''
Gracilinanus
''Gracilinanus'' is a genus of opossum in the family Didelphidae. It was separated from the genus ''Marmosa
The 27 species in the genus ''Marmosa'' are relatively small Neotropical members of the family Didelphidae. This genus is one of t ...
'' was described in 1989. The fifth currently recognized ''Cryptonanus'' species, ''
C. ignitus'', was described as a species of ''Gracilinanus'' in 2002. At that time, the species of ''Cryptonanus'' were variously regarded as separate species or as
synonyms
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 ...
or subspecies of other species of ''Gracilinanus''.
[Gardner, 2009, p. 40]
Robert Voss
Robert Andrew Voss (born 9 February 1953) is a British businessman in the metals industry. Voss was appointed Lord Lieutenant of Hertfordshire
This is an incomplete list of people who have served as Lord Lieutenant of Hertfordshire. From 1660 t ...
and others noticed that some of the animals then classified in ''Gracilinanus'' had an additional
foramen ovale, an opening in the skull that is formed by an extension of the bone of the alisphenoid tympanic wing towards the middle and front. They looked for other characters that correlated with the presence of the foramen and found them easy to find, defining a group of species distinct from ''Gracilinanus''.
[Voss et al., 2005, p. 2] A
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
analysis corroborated the distinctness of ''Cryptonanus'' and ''Gracilinanus''.
[Voss et al., 2005, fig. 4] Voss and colleagues first noted the discovery in a footnote in their 2004 paper on ''
Chacodelphys
The Chacoan pygmy opossum (''Chacodelphys formosa'') is a recently described genus and species of didelphimorph marsupial. The only species in ''Chacodelphys'', ''C. formosa'', was known until 2004 from only one specimen collected in 1920 in the ...
'' and subsequently described the group of species with the additional foramen as a new genus, ''Cryptonanus''.
[ The generic name, ''Cryptonanus'' is 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 κρυπτος ''kryptos'' (hidden) and νανος ''nanos'' (dwarf) and was chosen because ''Cryptonanus'' species are small and their true identity was long hidden by taxonomic
Taxonomy is the practice and science of categorization or classification.
A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
synonymy
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 ...
.[Voss et al., 2005, p. 11] ''Cryptonanus'' is currently classified in the tribe Thylamyini of subfamily Didelphinae
The Didelphinae are a subfamily of opossums consisting of 15 genera and 123 species. Specimens have been collected throughout the Americas, but are predominant in South and Central America.
Some sources call this subfamily the "American opossu ...
within the opossums.
Voss and colleagues recognized each of the five names they referred to ''Cryptonanus''—''agricolai, chacoensis, guahybae, ignitus'', and ''unduaviensis''—as separate species, although they could find few distinguishing characters between them.[ Further research in this matter is needed.][Voss and Jansa, 2009, p. 128]
Species
Cladogram of living ''Cryptonanus'' species.
The five species currently recognized are:
Description
''Cryptonanus'' species are small opossums even within their family and weigh about . The fur is unpatterned and usually reddish or grayish brown above and is grayish or unpigmented below. Guard hair
Guard hair or overhair is the outer layer of hair of most mammals, which overlay the fur. Guard hairs are long and coarse and protect the rest of the pelage (fur) from abrasion and frequently from moisture. They are visible on the surface of the fu ...
s are poorly developed. A dark ring surrounds the eyes. On the forefeet, the third and fourth digits are longer than the second and fifth. Females lack a pouch and have 9 to 15 mammae
A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in primat ...
. The tail looks naked to the unaided eye, but each scale in fact harbors three short hairs.[ Species of ''Cryptonanus'' and ''Gracilinanus'' are hardly distinguishable on external characters, though ''Cryptonanus'' species may have shorter tails, larger ears, broader eye-rings, and longer whiskers. More secure characters separate the skulls of the two genera.][Voss et al., 2005, p. 6] In addition to the presence of the additional foramen ovale, which exhibits some variation within species, ''Cryptonanus'' usually lacks maxillary fenestrae, perforations of the palate
The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity.
A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sepa ...
near the first and second molars, has the second upper premolar shorter than the third,[Voss et al., 2005, p. 7] lacks a rostral process, which extends the premaxilla
The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...
ry bone further to the front, and usually has additional cusps on the upper canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, or (in the context of the upper jaw) fangs, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth. They can appear more flattened however ...
. The species of ''Cryptonanus'' differ in coloration, size, and some characters of the teeth.
The karyotype
A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is disce ...
of ''C. agricolai'' includes 14 chromosomes with 24 major arms (2n = 14, FN = 24).[Voss et al., 2005, p. 14]
References
Literature cited
*Diaz M. and Barquez, R. 2008. . In IUCN. IUCN Red List of Threatened Species. Version 2009.2.
www.iucnredlist.org
. Downloaded on March 26, 2010.
*Gardner, A.L. 2009. Mammals of South America. Volume 1: Marsupials, xenarthrans, shrews, and bats. University of Chicago Press, 669 pp.
*Tate, G.H.H. 1931
Brief diagnoses of twenty-six apparently new forms of ''Marmosa'' (Marsupialia) from South America
''American Museum Novitates'' 493:1–14.
*Voss, R.S. and Jansa, S.A. 2009
Phylogenetic relationships and classification of didelphid marsupials, an extant radiation of New World metatherian mammals
''Bulletin of the American Museum of Natural History'' 322:1–177.
*Voss, R.S., Lunde, D.P. and Jansa, S.A. 2005
On the contents of ''Gracilinanus'' Gardner & Creighton, 1989, with the description of a previously unrecognized clade of small didelphid marsupials
''American Museum Novitates'' 3482:1–34.
*Voss, R.S., Gardner, A.L. and Jansa, S.A. 2004
On the relationships of ''"Marmosa" formosa'' Shamel, 1930 (Marsupialia, Didelphidae), a phylogenetic puzzle from the Chaco of northern Argentina
''American Museum Novitates'' 3442:1–18.
{{Taxonbar, from=Q311590
Opossums
Marsupial genera