Proechimys is a genus of South American spiny rats of the family Echimyidae. All species of the genus are terrestrial. In the lowland Neotropical forests, Proechimys rodents are often the most abundant non-volant mammals. They are recognizable by reason of their elongated heads and long rostra, large and erect ears, narrow and long hind feet, and tails always shorter than head-and-body lengths. The dorsal pelage comprises a mixture of expanded, varyingly stiffened spines (or aristiforms) — hence the vernacular name of spiny rats — and soft hairs (or setiforms).

Proechimys is the most speciose genus of the rodent family Echimyidae, with 25 species recognized, followed by Phyllomys with 13 species, and Trinomys with 11 species.

Phylogeny

Genus level

The genus Proechimys is the sister group to the genus Hoplomys (the armored rat). In turn, these two taxa share evolutionary affinities with other Myocastorini genera: Callistomys (the painted tree-rat) and Myocastor (the coypu or nutria) on the one hand, and Thrichomys on the other hand.

|title=Genus-level cladogram of the Myocastorini. |caption=The cladogram has been reconstructed from mitochondrial and nuclear DNA characters. |align=center |clades=

Species level

Reconstructing the systematics and phylogeny of Proechimys species have been greatly hampered by extreme levels of within- and among-population character variability. This difficulty has been emphasized by Pine et al.:

To infer the phylogeny of Proechimys at the species level, morphological characters and mitochondrial DNA sequences have been used, and allowed to group species into major clades but whose interrelationships remain unresolved. Six species groups were identified (group semispinosus, group longicaudatus, group guyannensis, group trinitatus, group goeldii, and group gardneri), and 4 species (Proechimys simonsi, P. echinothrix, P. canicollis, and P. decumanus) remained unaffiliated to any of these groups.

|title=Species-level cladogram of the genus Proechimys. |caption=The cladogram has been reconstructed from morphological characters and mitochondrial DNA (cytochrome b) sequences. |align=center |clades= The different groups of species can be diagnosed as follows.

Group semispinosus: it contains two species, Proechimys semispinosus, — with its widespread range, from Central America south from Honduras along the west coast of Colombia and Ecuador — and P. oconnelli, with a more limited range, east of the Cordillera Oriental in the north-western Amazon.
Group longicaudatus: it contains the three species Proechimys longicaudatus, P. brevicauda, and P. cuvieri, united by lyrate and strongly fanged incisive foramina, and deep groves extending onto the anterior palate. They range from the lowland rainforest of the Guianan region and Amazon basin to dry forests of eastern Bolivia, northern Paraguay, and central Brazil.
Group guyannensis: it contains the two species Proechimys guyannensis, and P. roberti, showing a plantar surface of hindfeet with six pads, and distributed mostly in the Guianan region, eastern Amazonia, and extending south into central Brazil.
Group trinitatus: it contains the eight species Proechimys trinitatus, P. mincae, P. guairae, P. poliopus, P. magdalenae, P. chrysaeolus, P. urichi, and P. hoplomyoides. These taxa possess large and open incisive foramina, and simplified cheek teeth.
Group goeldii: it contains the three species Proechimys steerei, P. quadruplicatus, and P. goeldii, united by a uniformly large body size. Members of this group most commonly inhabit the seasonally inundated várzea or igapó lowland forests of the Amazon basin.
Group gardneri: it contains the three species Proechimys gardneri, P. pattoni, and P. kulinae, characterized by short head and body length — less than 185 mm. They are distributed in western Amazonia, but with non-overlapping ranges as all three species replace one another along the length of the Juruá River or on its opposite banks.

Distribution

Proechimys species presently occur mainly in South America, in all countries except Argentina, Uruguay, and Chile. One member of the genus (P. semispinosus) also ranges into Central America.

::data[format=table title="style="text-align: center;" | Geographical distribution of ''Proechimys '' species in Brazil, Bolivia, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname, Trinidad and Tobago, Venezuela, and Central America (+ : presence in the corresponding country ; — : not observed).
Groups of species are numbered according to the species-level phylogeny."]

Groups	Species
03	Proechimys brevicauda	+	+	+	+	—	—	—	+	—	—	—	—
07	Proechimys canicollis	—	—	+	—	—	—	—	—	—	—	+	—
06	Proechimys chrysaeolus	—	—	+	—	—	—	—	—	—	—	—	—
03	Proechimys cuvieri	+	—	—	—	+	+	—	+	+	—	—	—
08	Proechimys decumanus	—	—	—	+	—	—	—	+	—	—	—	—
05	Proechimys echinothrix	+	—	?	—	—	—	—	—	—	—	—	—
10	Proechimys gardneri	+	+	—	—	—	—	—	—	—	—	—	—
09	Proechimys goeldii	+	—	—	—	—	—	—	—	—	—	—	—
06	Proechimys guairae	—	—	—	—	—	—	—	—	—	—	+	—
04	Proechimys guyannensis	+	—	—	—	+	+	—	—	+	—	+	—
06	Proechimys hoplomyoides	+	—	—	—	—	+	—	—	—	—	+	—
10	Proechimys kulinae	+	—	—	—	—	—	—	+	—	—	—	—
03	Proechimys longicaudatus	+	+	—	—	—	—	+	—	—	—	—	—
06	Proechimys magdalenae	—	—	+	—	—	—	—	—	—	—	—	—
06	Proechimys mincae	—	—	+	—	—	—	—	—	—	—	—	—
02	Proechimys oconnelli	—	—	+	—	—	—	—	—	—	—	—	—
10	Proechimys pattoni	+	—	—	—	—	—	—	+	—	—	—	—
06	Proechimys poliopus	—	—	+	—	—	—	—	—	—	—	+	—
09	Proechimys quadruplicatus	+	—	+	+	—	—	—	+	—	—	+	—
04	Proechimys roberti	+	—	—	—	—	—	—	—	—	—	—	—
02	Proechimys semispinosus	—	—	+	+	—	—	—	—	—	—	—	+
01	Proechimys simonsi	+	+	+	+	—	—	—	+	—	—	—	—
09	Proechimys steerei	+	+	—	—	—	—	—	+	—	—	—	—
06	Proechimys trinitatus	—	—	—	—	—	—	—	—	—	+	—	—
06	Proechimys urichi	—	—	—	—	—	—	—	—	—	—	+	—
::

References

{{MSW3 Hystricognathi
(2000-01-01). "Mammals of the Rio Juruá and the evolutionary and ecological diversification of Amazonia". Bulletin of the American Museum of Natural History.
(2005). "Ecomorphological diversification among South American spiny rats (Rodentia; Echimyidae): a phylogenetic and chronological approach". Molecular Phylogenetics and Evolution.
(2012). "Diversification and biogeography of the Neotropical caviomorph lineage Octodontoidea (Rodentia: Hystricognathi)". Molecular Phylogenetics and Evolution.
(2013-03-01). "Diversification of South American spiny rats (Echimyidae): a multigene phylogenetic approach". Zoologica Scripta.
(2014). "Unexpected phylogenetic relationships of the painted tree rat ''Callistomys pictus'' (Rodentia: Echimyidae)". Natureza on Line.
(2014-07-01). "Rodents of the Caribbean: origin and diversification of hutias unravelled by next-generation museomics". Biology Letters.
(2015). "Biology of caviomorph rodents: diversity and evolution". SAREM Series A, Mammalogical Research — Sociedad Argentina para el Estudio de los Mamíferos.
(2017-03-01). "Mitogenomic Phylogeny, Diversification, and Biogeography of South American Spiny Rats". Molecular Biology and Evolution.
(1981). "Aquatic biota of tropical South America: being a compilation of taxonomic bibliographies for the fauna and flora of inland waters of the tropical portion of South America". San Diego State University.
Patton, James L.. (1987). "Species groups of spiny rats, genus ''Proechimys'' (Rodentia: Echimyidae)". Fieldiana: Zoology, Studies in Neotropical Mammalogy: Essays in Honor of Philip Hershkovitz.
Da Silva, Maria Nazareth F.. (1998). "Four New species of spiny rats of the genus ''Proechimys'' (Rodentia: Echimyidae) from the Western Amazon of Brazil". Proceedings of the Biological Society of Washington.
(2015-03-09). "Mammals of South America, Volume 2: Rodents". University of Chicago Press.
Lord, Rexford D.. (2007-01-30). "Mammals of South America". Johns Hopkins University Press.

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