Chacoan pygmy opossum
The Chacoan pygmy opossum is the smallest known species of opossum. The head-body length is 68 mm, the tail is 55 mm long and the hind foot is 11 mm. It differs from other "marmosine" or mouse opossums in having a long third manual digit, no distinctly tricolored pelage, a long fourth pedal digit, and a tail shorter than the head-body length. No other marmosine genera have this combination of characters.
Until 2004, it was only known from one specimen collected in the Chaco of Formosa Province, Argentina in 1920. It is classed as Vulnerable.
It was originally described as Marmosa muscula Shamel (1930a); as this name is preoccupied, Shamel (1930b) renamed it M. formosa. George Tate (1933) considered it a member of his "Elegans group" (=Thylamys) of Marmosa. It was treated as a species of Marmosa or Thylamys until 1989, when Gardner & Creighton (1989) listed it as a synonym of Gracilinanus agilis and later separated it from this species as G. formosus. Voss et al. (2004) erected the new genus Chacodelphys for the species.
Catalog Number: USNM 236330
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Male; Adult
Preparation: Skin; Skull
Collector(s): A. Wetmore
Year Collected: 1920
Locality: Riacho Pilago, 10 mi NW, Kilometro 182, Formosa, Argentina, South America
- Type: Shamel, H. H. 1930 Mar 04. Journal of the Washington Academy of Sciences. 20: 83.; Renamed: Shamel, H. H. 1930 Aug 09. Journal of Mammalogy. 11: 311.
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Chacoan pygmy opossum
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 Chaco of Formosa Province, Argentina.
The Chacoan pygmy opossum is the smallest known species of didelphid. It has a head-body length of 68 mm, a tail of 55 mm and a hind foot of 11. It differs from the other "marmosine" genera (Marmosa, Monodelphis, Thylamys, Tlacuatzin, Gracilinanus, Marmosops, Lestodelphys) in having a long third manual digit, no distinctly tricolored pelage, a long fourth pedal digit, and a tail shorter than head-body. No other marmosine genera has this combination of characters.
C. formosa was originally described as Marmosa muscula Shamel (1930a); however, this name is preoccupied, so Shamel (1930b) renamed it M. formosa. Afterwards, George Tate (1933) considered it a valid member of his "Elegans group" (=Thylamys) of Marmosa, whereafter it has been variously synonymized or treated as a distinct species of Marmosa or Thylamys until 1989, when Gardner & Creighton (1989) listed it as a synonym of Gracilinanus agilis, and then later separated from this species as G. formosus. Finally, Voss et al. (2004) erected the new genus Chacodelphys for the species.
- Teta, P. & de la Sancha, N. (2008). Chacodelphys formosa. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 28 December 2008. Database entry includes justification for why this species is listed as vulnerable
- Gardner, A. L. (2005). "Order Didelphimorphia". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 7. ISBN 978-0-8018-8221-0. OCLC 62265494. http://www.bucknell.edu/msw3/browse.asp?id=10400056.
- Gardner, A.L. & Creighton, G.K. 1989. A new generic name for Tate's microtarsus group of South American mouse opossums (Marsupialia: Didelphidae). Proceedings of the Biological Society of Washington 102:3–7.
- Shamel, H.H. 1930a. A new murine opossum from Argentina. Journal of the Washington Academy of Sciences 20:83-84.
- Shamel, H.H. 1930b. A new name for Marmosa muscula Shamel. Journal of Mammalogy 11:311.
- Tate, G.H.H. 1933. A systematic revision of the marsupial genus Marmosa with a discussion of the adaptive radiation of the murine opossums (Marmosa). Bulletin of the American Museum of Natural History 66:1–250.
- Voss, R.S., Gardner, A.L. & 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, 2 June 2004.
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