The sizes are small. Body length 8-12.6 cm. Tail length 9.5-13.4 cm. Outwardly similar to earthen bunny, however they differ from it by a somewhat shortened foot, a thickening of the middle part of the tail (due to fatty tissue) and the absence of a “banner” on tail. Fat is deposited in the tail, and in autumn it becomes very thick. The front and hind limbs are five-fingered. The color of the hair is sandy brown on the dorsal side of the body and white on the abdominal.
The structure of the skull is similar to that of earthen bunnies.
Chromosomes in the diploid set in all three species of the genus 48 each.
Distributed from the lower reaches of the river. Urals to southern Ustyurt and East Kazakhstan.
They inhabit semi-deserts and deserts, preferring clay-gravelly deserts and salt marshes. Ecology is poorly studied. Zhitkova jerboa digs short and shallow temporary and also shallow, permanent burrows up to 5-6 m long. They feed mainly on the green parts of plants. The breeding season is extended. Litter during the year, apparently, at least two, 2-4 cubs each. Hibernate for the winter.
There are currently 3 species in the genus:
Jerboa Zhitkova- P. zhitkovi Kuznetzov, 1930 (East Kazakhstan),
Thick-tailed jerboa- P. platyurus Lichtenstein, 1823 (deserts along the lower reaches of the Ural River and along the Emba, Ustyurt, the northern and north-eastern coast of the Aral Sea, steppes along the Irgiz and Turgay rivers)
Vinogradov jerboa - P. (= Allactaga) vinogradovi Vorontzov, 1958 (Zaysan depression in the East Kazakhstan region).
GENUS THICKNANDED TUSHANKA PYGERETMUS Gloger, 1844
Sizes from small to medium (body length from 80 to 120 mm). Close to jerboas of the genus Alactagulus Nehr., From which they are distinguished by shorter feet and extreme fingers. The "banner" is developed no stronger than that of representatives of the latter, or absent, and only at the end of the tail there is a small tuft of hair. The middle part of the tail is fusiform thickened due to subcutaneous fat deposits, especially abundant in the summer and autumn. Spines of the penis on the sides of the dorsal hollow are located in a row and are not separated by a bare area from the spines that cover its end section. The outlines of the skull and the main signs of its structure are similar to those of the tarbaganchik. Differences: higher-crowned cheek teeth, a higher and vertically positioned coronoid process of the mandibular bone, more hollowly curved upper incisors, forming a sharper angle with the lower ones. The tubercle on the anteroposterior margin of the mandibular fossa is larger; it also protrudes more strongly forward.
Especially significant differences in the bones of the postcranial skeleton. Here, the relatively longest femur and tibia, compared to other five-fingered jerboas, are characteristic here. By the considerable length of the part of the tibia that has grown, they are second only to the three-fingered dwarf jerbo. Both the forearm and middle finger are shorter than other three- and five-fingered jerboas, with the middle finger shorter than half the length of the foregut. Pubic symphysis is significantly shortened.
A probable ancestral genus is the Early Pleistocene Pliopygeretmus Topach. et Scorik. The remains of Pygeretmus representatives are known from the Early Pleistocene much northeast (West Siberia), west (Volga-Don watershed) and north (southern Urals) the borders of the modern range.
Distributed in deserts and semi-deserts from the lower Urals and Ustyurt to the Aral Sea and the large bend of the river. Ishim, an isolated part of the range, covers the western parts of Betpak-Dala, Balkhash, Alakol and Zaysan hollows. Northwest China, in Mongolia there are no reliable finds yet.
The economic significance is not clarified. One species is involved in plague epizootics occurring on gerbils.
The genus includes no more than 3 species. In the territory of the former USSR, only 2 reliably differ.
TABLE FOR DETERMINATION OF TYPES OF TARGENT TUSCHANCHIK (PYGERETMUS GENUS) OF RUSSIAN FAUNA AND NEARBY TERRITORIES
12). The tail has a well-developed round brush, its end is white (Fig. 100, 1). The coronary length of the upper row of buccal teeth is 4.9-5.4-6.0 mm.
Zhitkov jerboa - P. shitkovi Kuzn.
2 (1). The tail is without a brush, at its end there is a small bundle of elongated black hair (Fig. 100, 2). Coronary length of the upper row of buccal teeth 4.0–4.6–5.0 mm
Aral jerboa - P. platyurus Licht.
Aral Sea thick-tailed jerboa - Pygerethmus platyurus
Small jerboa. Body length 70-95 mm, rear foot 30-35 mm. Muzzle shortened, flattened in front. The ears are short. The relatively short tail is very thickened, especially in the fall. There is no tail “banner” at all. The color of the top is pale-grayish-brown, sometimes with a slight pinkish tint, the belly is whitish, with a fawn bloom, the very end of the tail is blackish.
Distributed in the Aral Sea and Caspian littoral.
The inhabitant of deserts and semi-deserts, where he adheres to places with dense soils and sparse sparse vegetation.