Bristle-spined Porcupine
Encyclopedia
The Bristle-spined Rat, Chaetomys subspinosus, is an arboreal rodent
from Brazil
. Also known as the Bristle-spined Porcupine or Thin-spined Porcupine, it is the only member
of the genus
Chaetomys and the subfamily Chaetomyinae. It was officially described in 1818, but rarely sighted since, until December 1986 when two specimens - one a pregnant female - were found in the vicinity of Valencia in Bahia
State.
Their skulls are unusual in several ways. The eye socket is almost completely surrounded by a ring of bone. Incisors are distinctly narrow. Overall, the animal displays a mix of New World porcupine cranial characters, spiny rat cranial characters, and characters that set it apart from all other rodents.
The Bristle-spined Rat is restricted to remnant forests and forest edges in the Atlantic coastal forests on the East Coast of Brazil
. Its habitat is dwindling rapidly and the species may be vulnerable to extinction
. It is classified as vulnerable by IUCN and endangered by USDI (Nowak, 1999
n hystricognaths with hairs modified as spines or quills. Chaetomys has more highly developed spines than the spiny rats, but less developed than the porcupines. Characteristics of the premolar
suggest that it belongs with the Echimyidae, but characteristics of the incisor
enamel
suggest that it belongs in the Erethizontidae. This animal is not endangered any more.
Patterson and Pascual (1968), Patterson and Wood (1982), Woods (1982, 1984, 1993) Patton and Reig (1989), Nowak (1999), and Carvalho (2000) support the inclusion of this animal in the Echimyidae whereas Martin (1994), McKenna and Bell (1997), Carvalho and Salles (2004), and Woods and Kilpatrick (2005) argue that it belongs in the Erethizontidae. Emmons (2005) mentions the family Chaetomyidae without much further comment except to exclude it from Echimyidae.
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
from Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. Also known as the Bristle-spined Porcupine or Thin-spined Porcupine, it is the only member
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
of the genus
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...
Chaetomys and the subfamily Chaetomyinae. It was officially described in 1818, but rarely sighted since, until December 1986 when two specimens - one a pregnant female - were found in the vicinity of Valencia in Bahia
Bahia
Bahia is one of the 26 states of Brazil, and is located in the northeastern part of the country on the Atlantic coast. It is the fourth most populous Brazilian state after São Paulo, Minas Gerais and Rio de Janeiro, and the fifth-largest in size...
State.
Characteristics
Bristle-spined Rats are named because the spines on the back are more bristle-like in texture than the spines on the rest of the body. They have long naked tails which are not prehensile. Adult animals weigh around 1.3 kg (2.9 lb).Their skulls are unusual in several ways. The eye socket is almost completely surrounded by a ring of bone. Incisors are distinctly narrow. Overall, the animal displays a mix of New World porcupine cranial characters, spiny rat cranial characters, and characters that set it apart from all other rodents.
The Bristle-spined Rat is restricted to remnant forests and forest edges in the Atlantic coastal forests on the East Coast of Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. Its habitat is dwindling rapidly and the species may be vulnerable to extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally 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 recover may have been lost before this point...
. It is classified as vulnerable by IUCN and endangered by USDI (Nowak, 1999
Taxonomic controversy
No consensus has been reached as to the taxonomic position of Chaetomys. It is commonly placed with the New World porcupines in the family Erethizontidae or with the spiny rats the family Echimyidae. Both are South AmericaSouth America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n hystricognaths with hairs modified as spines or quills. Chaetomys has more highly developed spines than the spiny rats, but less developed than the porcupines. Characteristics of the premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
suggest that it belongs with the Echimyidae, but characteristics of the incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
suggest that it belongs in the Erethizontidae. This animal is not endangered any more.
Patterson and Pascual (1968), Patterson and Wood (1982), Woods (1982, 1984, 1993) Patton and Reig (1989), Nowak (1999), and Carvalho (2000) support the inclusion of this animal in the Echimyidae whereas Martin (1994), McKenna and Bell (1997), Carvalho and Salles (2004), and Woods and Kilpatrick (2005) argue that it belongs in the Erethizontidae. Emmons (2005) mentions the family Chaetomyidae without much further comment except to exclude it from Echimyidae.