Speckled spiny tree-rat

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Speckled spiny tree-rat
A brown rodent with its head pointed directly at the viewer sitting on a tree
Sabana de Torres, Santander, Colombia
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Placentalia
Order: Rodentia
Family: Echimyidae
Genus: Pattonomys
Species:
P. semivillosus
Binomial name
Pattonomys semivillosus
(I. Geoffroy, 1838)
Synonyms[2]
  • Nelomys semivillosus I. Geoffroy, 1838
  • Loncheres semivillosus Lesson, 1842
  • Loncheres semivillosa J. A. Wagner, 1843
  • Echimys semivillosus Trouessart, 1904
  • Makalata semivillosus G. E. Iack-Ximenes, de Vivo, & Percequillo, 2005

The speckled spiny tree-rat (Pattonomys semivillosus), also known as the Colombian speckled tree-rat,[3] is a species of rodent in the family Echimyidae. It is found in the swampy ciénegas of northeastern Colombia and northwestern Venezuela. It can be found in gallery forests, dry forests and mangrove forests. Its diet includes fruit and seeds.[1]

Taxonomy and etymology

The speckled spiny tree-rat was first described in 1838 by Isidore Geoffroy Saint-Hilaire, a French zoologist. He placed the species in the genus Nelomys and gave it the species name semivillosus, which pertains to the common name "semivillose nelomys".[4] The word "villose" originates from the Latin villōsus, 'shaggy'.[5] The description was based on three specimens sent by the French consul from the type locality "Carthagène (Nouvelle Grenade)" (present-day Cartagena, Colombia). Of the three specimens Geoffroy Saint-Hillaire examined, the location of only one is still known, that being the syntype placed in the National Museum of Natural History, France. Only a skull without the mandible is remaining from this specimen.[6] The species was clarified as belonging to the genus Pattonomys in 2006.[7]

As part of the genus Pattonomys, it is closely related to the giant tree-rat (Toromys grandis) and other members of the genus Toromys.[8] The recently described species Pattonomys carrikeri and P. punctatus have a disjunct distribution from P. semivillosus and are considered more genetically distant, almost as much as is Toromys.[9] The speckled spiny tree-rat has a notably high number of chromosomes, at 2n=94.[1] It has no subspecies.[3]

Genus-level cladogram of the Echimyini
Echimyini 
         

  Isothrix

  "Eumysopines"  
         
         
         
         

  Pattonomys

  Toromys
  (Giant tree-rat)

         

  Makalata

The cladogram has been reconstructed from mitochondrial and nuclear DNA characters.[10]

Description

The adult speckled spiny tree-rat is of medium size, having a head-body length ranging from 20 to 27 centimeters (7.9 to 11 inches), plus a tail that is 2.1 to 2.6 cm (0.8 to 1 in) long. It weighs between 194 and 407 grams (6.8 and 14 ounces). Its fur is pale gray to brown along the back, mixed to a yellow-buff, ocher, or black color along the middle. Along its sides, the tree-rat is sometimes grayish, though the flanks may carry the same color as the back. Its underside may be grayish, white, or pale orange. The small ears are pale but covered by fine black hairs along the edge. Near the base of the ear, at the antitragus, a tuft of white fur is visible.[3] The muzzle and throat is notably white and contrasts against the rest of the head, which is grizzled gray towards the sides and black overall.[9] Past the head and towards the tail, white-tipped guard hairs cover the tree-rat's body. The tail, which usually measures between 80 and 120% of the tree-rat's body length, is covered in short hairs. The broad hind feet have robust claws and are gray to yellow-gray on top.[3]

The skull of the speckled spiny tree-rat is short and narrow towards the face or rostrum. Narrow bony ledges appear around the eye sockets at the brow ridge above the eyes. The rat's incisors are white, and the openings behind them in the hard palate—the incisive foramina—are narrow. The hollow structures encasing the inner and middle ear, the auditory bullae, are somewhat large. Compared to other members of Pattonomys, the speckled spiny tree-rat has a narrower skull overall.[3]

Habitat and distribution

Speckled spiny tree-rats are found only in the drainage area of the lower Magdalena River of northeastern Columbia. They may also be found in parts of northwestern Venezuela. They occur at elevations of up to 600 meters (2,000 feet).[1]

The species is tree-dwelling and will make dens in tree holes. Preferred habitats of the speckled spiny tree-rat include moist areas of lowland thorn forests and swampy ciénegas. The species is sometimes found in rainforests, and more frequently found in gallery forests and dry forests. In the Llanos of northwestern South America, it may be found in trees.[1] Some speckled spiny tree-rats are found in the mangrove forests of Salamanca Island Road Park.[6]

Ecology and behavior

The speckled spiny tree-rat is nocturnal. It is presumed to be herbivorous, eating fruits and seeds,[1] though specific food items are unknown. Nothing is known of its social structure or reproductive habits.[3]

Conservation

There are no known major threats to the speckled spiny tree-rat. It is common within its range. The International Union for Conservation of Nature lists it as a least-concern species, citing its large population, wide distribution, and lack of evidence that populations are declining at an appreciable rate.[1] In their account of the species written in 2016, authors Pierre-Henri Fabre, Jim Patton, and Yuri Leite noted that additional studies on the speckled spiny tree-rat's ecology, habitat, and potential conservation threats were needed, as next to nothing was known about these subjects.[3]

References

  1. Aguilera, M. (2016). "Pattonomys semivillosus". IUCN Red List of Threatened Species. 2016 e.T90386452A22212633. doi:10.2305/IUCN.UK.2016-2.RLTS.T90386452A22212633.en. Retrieved 7 May 2026.
  2. "Pattonomys semivillosus". ASM Mammal Diversity Database. American Society of Mammalogists. Retrieved 7 May 2026.
  3. Fabre, Pierre-Henri; Patton, Jim; Leite, Yuri (2016). "Family Echimyidae". In Wilson, D.E.; Lacher, T.E.; Mittermeier, R.A. (eds.). Handbook of the Mammals of the World. Vol. 6. Lagomorphs and Rodents I. Lynx Edicions. p. 591. ISBN 978-84-941892-3-4.
  4. Geoffroy Saint-Hilaire, Isidore (2 July 1838). "Notice sur les rongeurs épineux désignés par les auteurs sous les noms d'Échimys, Loncheres, Heteromys et Nelomys". Comptes rendus hebdomadaires des séances de l'Académie des sciences (in French). 6: 884–888 – via Biodiversity Heritage Library.
  5. "villose". Dictionary.com Unabridged (Online). n.d. Retrieved 7 May 2026.
  6. Emmons, Louise H.; Fabre, Pierre-henri (9 March 2018). "A Review of the Pattonomys/Toromys Clade (Rodentia: Echimyidae), with Descriptions of a New Toromys Species and a New Genus". American Museum Novitates (3894): 1–52. doi:10.1206/3894.1. ISSN 0003-0082.
  7. Emmons, Louise H. (2 January 2006). "A revision of the genera of arboreal Echimyidae (Rodentia: Echimyidae, Echimyinae), with descriptions of two new genera". In Lacey, Eileen; Myers, Philip (eds.). Mammalian Diversification: From Chromosomes to Phylogeography. University of California Press. pp. 247–309. doi:10.1525/california/9780520098534.003.0009. ISBN 978-0-520-09853-4. Archived from the original on 22 May 2022. Retrieved 7 May 2026.
  8. Fabre, Pierre-Henri; Upham, Nathan S.; Emmons, Louise H.; Justy, Fabienne; Leite, Yuri L. R.; Loss, Ana Carolina; Orlando, Ludovic; Tilak, Marie-Ka; Patterson, Bruce D.; Douzery, Emmanuel J. P. (1 March 2017). "Mitogenomic Phylogeny, Diversification, and Biogeography of South American Spiny Rats". Molecular Biology and Evolution. 34 (3): 613–633. doi:10.1093/molbev/msw261. ISSN 0737-4038. PMID 28025278.
  9. Emmons, Louise H.; Fabre, Pierre-henri (9 March 2018). "A Review of the Pattonomys/Toromys Clade (Rodentia: Echimyidae), with Descriptions of a New Toromys Species and a New Genus". American Museum Novitates (3894): 1–52. doi:10.1206/3894.1. ISSN 0003-0082.