Kirchner viscacha rat
| Kirchner viscacha rat | ||||||||||||
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| Scientific name | ||||||||||||
| Tympanoctomys kirchnerorum | ||||||||||||
| Teta , Pardiñas , Sauthier & Gallardo , 2014 |
The Kirchner viscacha rat ( Tympanoctomys kirchnerorum ) is a species of rodent from the family of the turtle rats (Octodontidae) living in South America . It is only known from the type locality in the Gastre department in the southern Argentine province of Chubut and from Holocene fossils from four locations on the middle and lower Río Chubut . The species was only described in 2014 and is the second recent representative of the genus Tympanoctomys . Like its sister species, it inhabits dry landscapes, but little is known about its way of life. The stock is seen as threatened.
features
Habitus
The Kirchner Viscacha rat has an outwardly rat-like shape, the total length of the animals is around 22.2 to 25.6 cm, the tail is around 11.1 to 11.4 cm long, and the weight is 50 to 74 g. This makes them slightly smaller than their sister species , the red viscacha rat ( Tympanoctomys barrerae ), their tail is shorter in relation to the length of the head and torso . The fur shows a yellowish-brown color on the back, most of the hair here is about 13 mm long and has a gray hair base and yellowish-brown tips. In between there are blackish hairs about 20 mm long. The sides of the body are lighter. On the belly, on the throat and on the front and rear legs, a cream-colored to whitish tint dominates, the hair is only around 10 mm long and is partly gray at the base, but cream-colored at the tip. The upper head profile is curved, the ears are relatively short with a length of 14 to 15 mm. A tuft of coarse, whitish hair appears at the base of the ears. The Kirchner viscacha rat has about 30 whisker hairs on each side of its snout , including about 35 mm long, which are blackish in color, and about 60 mm long, which are thicker and blackish or whitish or blackish at the base and whitish at the tip. Two or three whiskers appear above the eyes on each side, one of which reaches the outer edge of the ears. In addition, there are four whiskers on each of the cheeks, each of which extends to the base of the ear. The bristles on the palate, typical of Tympanoctomys, are well developed and consist of thick, whitish hairs. The tail is designed in two colors, darker on the top and lighter on the underside, it has a less dense coat than that of the red viscacha rat. The last 2.5 cm are completely blackish, the brush-like, dark tuft of hair at the end is not quite as pronounced as in the red visca rat. The front and rear feet show a whitish colored, short-haired fur on the back, while longer hairs cover the well-developed claws in the front. The length of the rear foot varies between 29 and 33 mm.
Skull and dentition features
The skull is broad and almost pear-shaped when viewed from above. The length is 27.2 to 34.2 mm, the width between the zygomatic arches 16.7 to 18.5 mm. As with the red viscacha rat, the largest width of the skull is at the back of the head, here it measures between 17.3 and 20.8 mm. The wide cranium is mainly caused by the inflated tympanic bladders , a typical characteristic of species that are adapted to desert climates. With a length of 13.3 to 17.6 mm each, the tympanic membranes also take up a good half of the total length of the skull. Here the skull reaches its greatest height with up to 16.4 mm. The nasal bone is short and smooth on the surface, it tapers towards the back. The frontal bone increases in width at the back. The dentition consists of 20 teeth with the following dental formula together: . The incisors are built wide, each over 1.5 mm, in the upper jaw they point backwards ( orthodontically ). The tooth enamel has an orange color. A long diastema separates the posterior teeth from the incisor. The molars are high crowned and 8-shaped in outline. This also applies to the third molar in the lower jaw, while it is comma-shaped in the red viscacha rat and the extinct species Tympanoctomys cordubensis . The entire upper row of teeth is between 5.0 and 5.7 mm long, the lower one is only slightly shorter.
Genetics and miscellaneous
Like the red and golden viscacha rats ( Pipanacoctomys aureus ), the Kirchner viscacha rat probably also has a tetraploid set of chromosomes , i.e. the animal has four sets of chromosomes instead of the usual two. This also means that the sperm cells are on average larger than in other diploid mammals. They have a paddle-like, somewhat cut-off head 11.8 μm in length and 9.6 μm in width, the tail reaches 55.5 μm in length. In Tympanoctomys kirchnerorum , the rib that separates the acrosome from the rest of the head is 18 to 22% of the head length, measured from the base of the head, and thus noticeably deeper than in the red viscacha rat.
Way of life
Little is known about the way of life of the Kirchner Viscacha rat. The range of the species is limited to the central Patagonia , where it inhabits steppe landscapes with sandy subsoil and badlands . The average annual temperature is 8 to 9 ° C, the annual rainfall is 150 mm. The vegetation is sparse, the type locality is Chuquiraga inventories directly from the group of daisy family covered in which also Prosopis - Prosopidastrum and - Schinus occur -Gewächse. The Kirchner Viscacha rat lives partly underground, the buildings have characteristic, semicircular entrances averaging 10 cm high with a curved top and flat bottom. They are often found under bushes, primarily from reports that occur in depressions in the region. Single individuals of the species have been found in the crusts of owls .
Systematics
The Kirchner Viscacha rat is a species from the genus Tympanoctomys . Two other species are assigned to this, of which only the red viscacha rat ( Tympanoctomys barrerae ) occurs recently in central-western Argentina around 550 km north of the occurrence of Tympanoctomys kirchnerorum . Tympanoctomys belongs to the family of the turtle rats (Octodontidae), their closest relatives are the golden viscacha rat Pipanacoctomys and the viscacha rat ( Octomys ). With the help of molecular genetic studies, three lines could be identified within Tympanoctomys . One of them includes the species Tympanoctomys kirchnerorum , which split off in the Lower Pleistocene about 1.47 million years ago. The other two lines are assigned to the red viscacha rat, which evidently formed around 1.02 million years ago.
Discovery story
First indications of an addition to the Red viscacha rat further, in the Holocene occurring members of the genus Tympanoctomys in Patagonia provided early 21st century excavations of rock shelters and caves near the Rio Chubut. Numerous fragments of the lower jaw came to light, the age of which radiometrically dated from 5400 years ago to the early modern period and which are interpreted as the remains of owls. The findings were assigned to the red viscacha rat, the results were published in 2009. A year earlier, in March 2008, a first free-living population could also be observed on the Río Chubut near Estancia La Porfía around 20 km north-northeast of Los Adobes in the Gastre department of the Argentine province of Chubut . Three individuals, one female and two males were caught and prepared. The publication on this was also published in 2009 and brought the animals into connection with the red viscacha rat. Further on-site investigations led to the first description of the new species by Pablo Teta and fellow researchers in 2014 . The holotype is one of the captured males from March 2008 (copy number CNP 1862). The species name kirchnerorum honors Néstor Kirchner , who was President of Argentina and General Secretary of the Union of South American Nations in 2010 , and his wife Cristina Fernández de Kirchner , who succeeded her husband in the presidency. The honor came because, during the Kirchner's tenure, the sciences were actively promoted through budget increases, the return of scientists from abroad and the creation of the Ministerio de Ciencia, Tecnología e Innovación Productiva .
Danger
The known distribution area of the Kirchner-Viscacha rat is very small, so far there has only been evidence of living animals within a radius of 3 km around the type locality of the first observation. In the middle and lower valley of the Río Chubut, the species has most likely become extinct, possibly due to the introduction of sheep breeding in the transition from the 19th to the 20th century in this region and the associated overgrazing and compaction of the soil. Since uranium mining is also planned in the distribution area , the stock of Tympanoctomys kirchnerorum is considered to be threatened.
literature
- M. Monica Díaz, Rubén M. Barquez and Diego H. Verzi: Genus Tympanoctomys Yepes, 1942. In: James L. Patton, Ulyses FJ Pardiñas and Guillermo D'Elía (eds.): Mammals of South America, Volume 2: Rodents . University of Chicago Press, 2015, pp. 1047-1048
- Pablo Teta, Ulyses FJ Pardiñas, Daniel E. Udrizar Sauthier and Milton H. Gallardo: A new species of the tetraploid vizcacha rat Tympanoctomys (Caviomorpha, Octodontidae) from central Patagonia, Argentina. Journal of Mammalogy 95 (1), 2014, pp. 60-71 doi: 10.1644 / 13-MAMM-A-160
Individual evidence
- ↑ a b c d e f g Pablo Teta, Ulyses FJ Pardiñas, Daniel E. Udrizar Sauthier and Milton H. Gallardo: A new species of the tetraploid vizcacha rat Tympanoctomys (Caviomorpha, Octodontidae) from central Patagonia, Argentina. Journal of Mammalogy 95 (1), 2014, pp. 60-71
- ↑ a b c M. Monica Díaz, Rubén M. Barquez and Diego H. Verzi: Genus Tympanoctomys Yepes, 1942. In: James L. Patton, Ulyses FJ Pardiñas and Guillermo D'Elía (eds.): Mammals of South America, Volume 2: Rodents. University of Chicago Press, 2015, pp. 1043-1048
- ↑ a b c Milton H. Gallardo, Daniel E. Udrizar Sauthier, Agustina A. Ojeda and Ulyses FJ Pardiñas: Discovery of desert-adapted Tympanoctomys barrerae in Central Patagonia, Argentina. Mammalia 73, 2009, pp. 158-161
- ↑ Milton H. Gallardo, Elkin Y. Suárez-Villota, José J. Nuñez, Rodrigo A. Vargas, Ronie Haro and Nélida Köhler: Phylogenetic analysis and phylogeography of the tetraploid rodent Tympanoctomys barrerae (Octodontidae): insights on its origin and the impact of Quaternary climate changes on population dynamics. Biological Journal of the Linnean Society 108, 2013, pp. 453-469, doi : 10.1111 / j.1095-8312.2012.02016.x
- ↑ Daniel E. Udrizar Sauthier, Ulyses FJ Pardiñas and Eduardo P. Tonni: Tympanoctomys (Mammalia: Rodentia) en el Holoceno de Patagonia, Argentina. Ameghiniana 46, 2009, pp. 203-207
- ↑ Ulyses FJ Pardiñas, Daniel E. Udrizar Sauthier and Pablo Teta: Micromammal diversity loss in central-eastern Patagonia over the last 400 years. Journal of Arid Environments 85, 2012, pp. 71-75