Cryptonanus
Encyclopedia
Cryptonanus is a genus
of opossums from South America. It includes five species found from Bolivia to Uruguay and eastern Brazil, one of which is now extinct. Although the first species were discovered in 1931, the genus was not recognized as distinct from Gracilinanus
until 2005. It includes small opossums with generally grayish, sometimes reddish, fur that are mainly distinguished from other opossums by characters of the skull.
, who described Marmosa microtarsus guahybae (now Cryptonanus guahybae) as a subspecies
of Marmosa microtarsus (now Gracilinanus microtarsus), Marmosa agilis chacoensis (now Cryptonanus chacoensis) as a subspecies of Marmosa agilis (now Gracilinanus agilis), and Marmosa unduaviensis (now Cryptonanus unduaviensis) as a separate species. In 1943, another species was described, Marmosa agricolai (now Cryptonanus agricolai). Species of Cryptonanus were then included in a broadly defined genus Marmosa
until the genus Gracilinanus
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
or subspecies of other species of Gracilinanus.
Robert Voss 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. A phylogenetic
analysis corroborated the distinctness of Cryptonanus and Gracilinanus. Voss and colleagues first noted the discovery in a footnote in their 2004 paper on Chacodelphys 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
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
synonymy. Cryptonanus is currently classified in the tribe Thylamyini of subfamily Didelphinae
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. The five species currently recognized are:
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. 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. 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
near the first and second molars, has the second upper premolar shorter than the third, lacks a rostral process, which extends the premaxilla
ry bone further to the front, and usually has additional cusps on the upper canine tooth
. The species of Cryptonanus differ in coloration, size, and some characters of the teeth.
The karyotype
of C. agricolai includes 14 chomosomes with 24 major arms (2n = 14, FN = 24).
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of opossums from South America. It includes five species found from Bolivia to Uruguay and eastern Brazil, one of which is now extinct. Although the first species were discovered in 1931, the genus was not recognized as distinct from Gracilinanus
Gracilinanus
Gracilinanus is a genus of opossum in the family Didelphidae. It was separated from the genus Marmosa in 1989, and has since had the genus Cryptonanus removed from it...
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 TateGeorge Henry Hamilton Tate
George Henry Hamilton Tate was an English-born American zoologist, who worked as a mammalogist for the American Museum of Natural History in New York....
, who described Marmosa microtarsus guahybae (now Cryptonanus guahybae) as a subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of Marmosa microtarsus (now Gracilinanus microtarsus), Marmosa agilis chacoensis (now Cryptonanus chacoensis) as a subspecies of Marmosa agilis (now Gracilinanus agilis), and Marmosa unduaviensis (now Cryptonanus unduaviensis) as a separate species. In 1943, another species was described, Marmosa agricolai (now Cryptonanus agricolai). Species of Cryptonanus were then included in a broadly defined genus Marmosa
Marmosa
The nine species in the genus Marmosa are relatively small Neotropic members of the order Didelphimorphia. This genus is one of four that are known as mouse opossums. The others are Micoureus , Thylamys and Tlacuatzin, the grayish mouse opossum...
until the genus Gracilinanus
Gracilinanus
Gracilinanus is a genus of opossum in the family Didelphidae. It was separated from the genus Marmosa in 1989, and has since had the genus Cryptonanus removed from it...
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
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
or subspecies of other species of Gracilinanus.
Robert Voss and others noticed that some of the animals then classified in Gracilinanus had an additional foramen ovale
Foramen ovale (skull)
At the base of the skull the foramen ovale is one of the larger of the several holes that transmit nerves through the skull. The foramen ovale is situated in the posterior part of the sphenoid bone, posterolateral to the foramen rotundum.-Contents:Several nerves, arteries and veins pass through...
, 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. A phylogenetic
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
analysis corroborated the distinctness of Cryptonanus and Gracilinanus. Voss and colleagues first noted the discovery in a footnote in their 2004 paper on Chacodelphys 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
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
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
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
synonymy. Cryptonanus is currently classified in the tribe Thylamyini of subfamily Didelphinae
Didelphinae
Didelphinae is a subfamily of opossums. Specimens have been collected throughout the Americas but are predominant in South and Central America....
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. The five species currently recognized are:
- Cryptonanus agricolai (states of CearáCearáCeará is one of the 27 states of Brazil, located in the northeastern part of the country, on the Atlantic coast. It is currently the 8th largest Brazilian State by population and the 17th by area. It is also one of the main touristic destinations in Brazil. The state capital is the city of...
, GoiásGoiásGoiás is a state of Brazil, located in the central part of the country. The name Goiás comes from the name of an indigenous community...
, and Minas GeraisMinas GeraisMinas Gerais is one of the 26 states of Brazil, of which it is the second most populous, the third richest, and the fourth largest in area. Minas Gerais is the Brazilian state with the largest number of Presidents of Brazil, the current one, Dilma Rousseff, being one of them. The capital is the...
in eastern Brazil) - Cryptonanus chacoensis (southeastern Bolivia, Paraguay, northeastern Argentina, and Uruguay)
- Cryptonanus guahybae (coastal Rio Grande do SulRio Grande do SulRio Grande do Sul is the southernmost state in Brazil, and the state with the fifth highest Human Development Index in the country. In this state is located the southernmost city in the country, Chuí, on the border with Uruguay. In the region of Bento Gonçalves and Caxias do Sul, the largest wine...
, Brazil) - Cryptonanus ignitus (single locality in Jujuy, northwestern Argentina; extinct)
- Cryptonanus unduaviensis (northern and eastern Bolivia)
Description
Cryptonanus species are small opossums, weighing about 15 to 40 g (0.529109431576679 to 1.4 ). The fur is unpatterned and usually reddish or grayish brown above and is grayish or unpigmented below. Guard hairGuard hair
Guard hairs are the longest, coarsest hairs in a mammal's coat, forming the topcoat . They taper to a point and protect the undercoat from the elements. They are often water repellent and stick out above the rest of the coat...
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
Pouch (marsupial)
The pouch is a distinguishing feature of female marsupials ; the name marsupial is derived from the Latin marsupium, meaning "pouch". Marsupials give birth to a live but relatively undeveloped fetus called a joey. When the joey is born it crawls from inside the mother to the pouch...
and have 9 to 15 mammae. 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. 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
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 separate. The palate is divided into two parts, the anterior...
near the first and second molars, has the second upper premolar shorter than the third, lacks a rostral process, which extends the premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
ry bone further to the front, and usually has additional cusps on the upper canine tooth
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
. The species of Cryptonanus differ in coloration, size, and some characters of the teeth.
The karyotype
Karyotype
A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
of C. agricolai includes 14 chomosomes with 24 major arms (2n = 14, FN = 24).
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. ISBN 9780226282404
- 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.