Noronhomys

Source: Wikipedia, the free encyclopedia.

Noronhomys

Extinct (1503)  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Cricetidae
Subfamily: Sigmodontinae
Genus: †Noronhomys
Carplaton and Olson, 1999
Species:
†N. vespuccii
Binomial name
†Noronhomys vespuccii
Carleton and Olson, 1999
Map of the southern Atlantic Ocean with southwestern Africa and northeastern South America, with an island off northeastern Brazil highlighted.
Location of
endemic
.

Noronhomys vespuccii, also known as Vespucci's rodent,[2] is an extinct rat species from the islands of Fernando de Noronha off northeastern Brazil. Italian explorer Amerigo Vespucci may have seen it on a visit to Fernando de Noronha in 1503, but it subsequently became extinct, perhaps because of the exotic rats and mice introduced by the first explorers of the island. Numerous but fragmentary fossil remains of the animal, of uncertain but probably Holocene age, were discovered in 1973 and described in 1999.

Noronhomys vespuccii was a fairly large rodent, larger than the black rat (Rattus rattus). A member of the family Cricetidae and subfamily Sigmodontinae, it shares several distinctive characters with Holochilus and related genera within the tribe Oryzomyini, including high-crowned molars with simplified crown features and the presence of several ridges on the skull which help anchor the chewing muscles. Although a suite of traits suggest that Holochilus is its closest relative, it is distinctive in many ways and is therefore classified in a separate genus, Noronhomys. Its close relatives, including Holochilus and Lundomys, are adapted to a semiaquatic lifestyle, spending much of their time in the water, but features of the Noronhomys bones suggest that it lost its semiaquatic lifestyle, after arrival at its remote island.

Discovery and taxonomy

Italian explorer

Trachylepis atlantica and the record of snakes most likely refers to Amphisbaena ridleyi, which is actually an amphisbaenian instead of a snake.[7]

During excavations conducted in 1973, American ornithologist

generic name, Noronhomys, combines the name of the island of Fernando de Noronha with the Ancient Greek μῦς mys "mouse"[8] and the specific name, vespuccii, honors Amerigo Vespucci.[9] Noronhomys would have been larger than the black rat (Rattus rattus), which was common on ships and which Vespucci would have been familiar with, consistent with his description of "very large rats".[7]

Pseudoryzomys simplex

Lundomys molitor

Noronhomys vespuccii

Holochilus brasiliensis

Holochilus sciureus

Suggested relationships of Noronhomys.[10]

Noronhomys is a member of the

tribe Oryzomyini, which includes over a hundred species distributed mainly in South America, including nearby islands such as the Galápagos Islands and some of the Antilles. Oryzomyini is one of several tribes recognized within the subfamily Sigmodontinae, which encompasses hundreds of species found across South America and into southern North America. Sigmodontinae itself is the largest subfamily of the family Cricetidae, other members of which include voles, lemmings, hamsters, and deermice, all mainly from Eurasia and North America.[11]

Carleton and Olson performed a detailed comparison of Noronhomys to members of the mainland genera Holochilus and Lundomys on the basis of both general morphology and morphometrical data, concluding that the Fernando de Noronha rat is distinct from both other animals.[12] They used a

Holochilus primigenus, may also be related, but is likely to fall outside the Holochilus–Noronhomys clade.[13]

In 1998, a fragmentary fossil of another species of this group of oryzomyines was found in eastern Argentina. It was initially identified as a possible second species of Noronhomys on the basis of the presence of a crest on the upper first molar, the

mesoloph,[14] but the specimen is different from Noronhomys vespuccii in other respects, and in 2008 it was described as a new genus and species, Carletonomys cailoi, related to Noronhomys and associated genera.[14]

Description

From top to bottom: side view of skull with mandible, missing the upper incisor and much of the posterior part; text "2. Hesperomys molitor"; and views of the same skull from above and below.
The skull of the living Lundomys molitor is similar to that of Noronhomys.[15] (The illustrated mandible is not of a Lundomys.)[16]

Noronhomys vespuccii is known from bone fragments, including five skulls, damaged to various degrees, and many isolated jaws and other bones.[17] This material documents that, with a skull of about 4 cm (1.5 in) (occipitonasal length), Noronhomys was a moderately large oryzomyine, smaller than Lundomys but well within the range of Holochilus.[18] It shares a number of the features that characterize the group of Holochilus and related genera,[19] including a reduction in the complexity of the chewing surface of the molars,[15] simple posterolateral palatal pits (perforations of the palate near the third molar),[20] and a similarly shaped interorbital region of the skull.[21] Noronhomys is distinctive, among other characters, in its lack of a spinous process on the zygomatic plate, the flattened front portion of the zygomatic arch (cheekbone); the short palate, which does not extend behind the third molars; and the presence of an accessory crest, the mesoloph, on the upper molars.[18]

Analysis of morphometrical data from the known material of Noronhomys suggests that growth continued in adults—the older the animal, the larger the depth of the

Holochilus sciureus at about 200 to 250 g (7.1 to 8.8 oz).[7]

Skull

In the foreground, a wavy sea at the right and a yellow beach covered with black stones at the left. In the background, a mountain covered with green vegetation out of which towers a steep black rock.
View of Morro do Pico on Fernando de Noronha.

The skull is flattened in general shape. The front part is short and broad. The broad

jugal bone is small.[20]

The back margin of the zygomatic plate is located close to the front of the upper first molar. The

tegmen tympani, the roof of the tympanic cavity,[15] a defining character of oryzomyines.[31]

The mandible (lower jaw) is robust. The two masseteric ridges, which anchor some of the chewing muscles, are joined together as a single crest for a portion of their length and extend forward to a point below the first molar. The capsular process, a raising of the mandibular bone at the back end of the lower incisor, is well developed.[15]

Teeth

In the upper incisors, the chewing edges are located behind the vertical plane of the incisors; thus, they are

dentine.[34] The microstructure is similar to that of Holochilus brasiliensis[35] and displays several characters seen only in Myomorpha.[36]

Map of an archipelago in the Atlantic Ocean. The main island is rod-shaped, oriented approximately west-southwest to east-northeast, with some irregular features in the coastline. A red label at the northeastern tip. Off the southern coast are nine smaller islands. Off the northeastern tip of the main island are five other smaller islands.
Map of the Fernando de Noronha archipelago, showing the fossil site where remains of Noronhomys have been found (in red).[37]

The molars are high-crowned (

entoflexid on the lower third molar—are closed by a wall, or cingulum, at the inner margin of the tooth. As in most oryzomyines, the upper molars all have one root on the inner (lingual) side and two on the outer (labial) side and the lower molars have a single root at the front and back of each molar; in addition, the first upper molar has another labial root and the first lower molar has a small labial and usually also a small lingual root located between the main roots.[15]

Postcranial skeleton

The entepicondylar foramen is absent,[15] as in all members of the Sigmodontinae; if present, as in some other rodents, this foramen (opening) perforates the distal (far) end of the humerus (upper arm bone).[39] The pelvis and the bones of the hindlimbs are heavily built. The femoral tubercle of the acetabulum (part of the pelvis), which anchors the rectum femoris muscle, is reduced relative to Holochilus and Lundomys.[40]

Distribution and origin

Trachylepis atlantica,[41] which still lives on Fernando de Noronha, is one of the few other animals found on the island.[42]

Noronhomys is known only from Fernando de Noronha, a small archipelago of volcanic origin off northeastern Brazil, consisting of a main island and several associated smaller islands. The formation of the archipelago, which has never been connected to the mainland, began about 11 million years ago; active vulcanism ceased about 2 million years ago.[43] Remains of Noronhomys were found in association with remains of various reptiles, birds, and snails, several of which are also restricted to the archipelago,[18] in sand dunes near the northeastern tip of the main island.[44] The age of the deposits is unknown, but is likely late Holocene, at most a few thousand years old.[3]

The ancestor of Noronhomys may have been a semiaquatic animal, similar to living Holochilus or Lundomys, that arrived on Fernando de Noronha by chance on a floating log.[45] The morphology of the limb bones in Noronhomys suggests that the animal was not semiaquatic like its relatives, but terrestrial, consistent with its occurrence on a small island, where streams and pools are rare or absent.[46]

Extinction

Vespucci's account suggests that Noronhomys was common when the island was first visited, but it was not encountered by the first biological explorers of the island, who conducted their research in the late 19th century. The

endemic species.[47] As early as 1888, Henry Nicholas Ridley suggested that the rat Vespucci had seen had been driven to extinction by the introduced black rat.[48] The International Union for Conservation of Nature lists it as "extinct".[1]

References

  1. ^ a b Weksler, M. & Costa , L.M. 2019. Noronhomys vespuccii. The IUCN Red List of Threatened Species 2019: e.T136692A22333193. https://dx.doi.org/10.2305/IUCN.UK.2019-1.RLTS.T136692A22333193.en. Accessed on 01 May 2023.
  2. ^ Musser and Carleton, 2005, p. 1136
  3. ^ a b c Carleton and Olson, 1999, p. 2
  4. ^ Carleton and Olson, 1999, p. 44
  5. ^ Translation from the Italian by Branner, 1888, p. 869, cited in Carleton and Olson, 1999, p. 2
  6. ^ Carleton and Olson, 1999, p. 46
  7. ^ a b c Carleton and Olson, 1999, p. 48
  8. ^ Carleton and Olson, 1999, p. 10
  9. ^ Carleton and Olson, 1999, p. 12
  10. ^ a b Carleton and Olson, 1999, fig. 22
  11. ^ Musser and Carleton, 2005
  12. ^ Carleton and Olson, 1999, pp. 16–32
  13. ^ Carleton and Olson, 1999, p. 50
  14. ^ a b Pardiñas, 2008, p. 1271
  15. ^ a b c d e f g h Carleton and Olson, 1999, p. 16
  16. ^ Voss and Carleton, 1993, p. 6
  17. ^ Carleton and Olson, 1999, pp. 10–11
  18. ^ a b c Carleton and Olson, 1999, p. 9
  19. ^ Weksler, 2006, p. 131
  20. ^ a b c d e Carleton and Olson, 1999, p. 13
  21. ^ Carleton and Olson, 1999, pp. 12–13
  22. ^ Carleton and Olson, 1999, p. 27; table 5
  23. ^ Carleton and Olson, 1999, p. 28
  24. ^ Carleton and Olson, 1999, pp. 29–32
  25. ^ Carleton and Olson, 1999, table 1
  26. ^ Carleton and Olson, 1999, table 2
  27. ^ Carleton and Olson, 1999, table 3
  28. ^ Carleton and Olson, 1999, p. 14
  29. ^ Weksler, 2006, p. 30
  30. ^ Weksler, 2006, p. 35
  31. ^ Weksler, 2006, p. 40
  32. ^ Weiss and Malabarba, 2005, pp. 153–154
  33. ^ Kalthoff, 2000, p. 16
  34. ^ Weiss and Malabarba, 2005, pp. 153–154; Kalthoff, 2000, p. 17
  35. ^ Kalthoff, 2000, p. 55
  36. ^ Weise and Malabarba, 2005, p. 159
  37. ^ Carleton and Olson, 1999, fig. 2
  38. ^ Weksler, 2006, pp. 43–44; Pardiñas, 2008, table 2
  39. ^ Weksler, 2006, p. 55
  40. ^ Carleton and Olson, 1999, p. 21
  41. ^ Miralles et al., 2009, p. 57
  42. ^ Carleton and Olson, 1999, p. 55
  43. ^ Carleton and Olson, 1999, pp. 5–7
  44. ^ Carleton and Olson, 1999, p. 8
  45. ^ Carleton and Olson, 1999, pp. 55–56
  46. ^ Carleton and Olson, 1999, p. 54
  47. ^ Carleton and Olson, 1999, pp. 48–49
  48. ^ Ridley, 1888, p. 474

Bibliography

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Noronhomys&oldid=1220205778"