Dornschwanzbilch ( Zenkerella insignis )
The thorn tail squirrel ( Anomaluridae ) are a poor family of rodents of the rainforests of West and Central Africa.
The shape of a thorn tail squirrel has striking similarities to that of a flying squirrel. Despite this superficial similarity include thorn tail squirrel neither to the squirrels nor are they related to these. With the exception of differing Dornschwanzbilchs all species have a flight skin. On closer inspection, this is different from the flying squirrel follows: While this is a crescent-shaped bone at the wrist tightens the sliding skin, have thorn tail squirrel a broadened Elle, on which a cartilaginous rod sits, takes over this function. From this it can be seen already that when flying squirrel and squirrel tail spike the Gleitmembran has developed independently of each other, so that it is an example of convergent evolution.
The name derives from the thorn tail Squirrel, is a series of hairless shed at the tail base. Each of these scales is sitting on a horny spine. The scales occupy the anterior third of tail, their number, depending on the kind of between twelve and eighteen. The function of this device is obviously a better grip, the animals found in the branches when they anchor themselves with thorns on the bark. The size varies considerably: The Gleitbilche have a body length of only 6 cm, on the other hand can reach some of the biggest thorn tail squirrel dimensions of 45 cm, for which again added the same tail length.
Way of life
Thorn tail squirrel are inhabitants of the rain forests, where they are well adapted to the sharp claws, the aforementioned horny scales and the Gleitmembran to life in the top region of the trees. On the forest floor such animals are probably only accidentally, and there they then move quite awkward. A vertical tree trunk they climb almost like a looper: you hit the claws of the front legs in the bark and then pull the rear body after.
The sliding behavior resembles that of the flying squirrel. From an elevated road to spine tail squirrel repel and open their sliding skin, which they then up to 100 m, according to unconfirmed reports even carries up to 250 m wide. Often, however, a substantially shorter flight is sufficient to reach a neighboring tree.
All thorn tail ends are nocturnal. The day she slept in tree hollows. The food are nuts, fruits and leaves. Occasionally they also eat insects.
The classification of spike tail squirrel into the system of rodents has long been quite enigmatic and is still far from being resolved. A classification for the Squirrel, as the group's name seems to suggest, was excluded early, as there is on the sliding skin also nothing in common, and this is from the Flying Squirrel on closer inspection, very different. Especially the skull shape is unique among rodents. In the search for similarities with other rodents finally found the perfect one different from the outer Formspring rabbits, which showed in the anatomical details of the middle ear and the carotid artery matches with the thorn tail squirrel. This hypothesis was first proposed in 1985 for the first time questioned due to lack of fossil evidence, is now regarded but thanks to the molecular genetic analysis of Montgelard & al. as backed up. Thorn tail squirrel and spring hares are therefore considered as sister groups and are combined in a common taxon thorn tail squirrel relatives ( Anomaluromorpha ). Both groups have, however, very early, probably separated during the Eocene.
The question of what relationships now again have the Anomaluromorpha to other rodents, move currently still in the realm of pure speculation. Currently, the taxon within the rodents is largely isolated.
Known are three genera of stem-tail squirrel:
- True mandrel tail squirrel ( Anomalurus )
- Gleitbilche ( Idiurus )
- Dornschwanzbilche ( Zenkerella )
The latter genus with only one species is very notwithstanding the absence of a flight skin, but there is no doubt as to the membership of the mandrel tail squirrel because of the characteristic horn scales of the tail base. Sliding and Dornschwanzbilche are sometimes united in a common subfamily Zenkerellinae (or Idiurinae ), which are the Anomalurinae with the single genus Anomalurus opposite.
While there is no evidence for common ancestry of spring hares and squirrels tail spike as mentioned, are fossil stem-tail squirrel since the early Eocene is what makes it one of the oldest known Nagetiertaxa. Also from the Eocene knows the fossils of Zegdoumyidae that are located in the immediate family, the spike tail squirrel. From the spike tail squirrel itself is from the Eocene genus Nementchamys and from the Oligocene and Miocene the genus Paranomalurus known. The extant genera are handed down since the Miocene. While all of these fossils were found in Africa, where even today's thorn tail ends are located, remains of a rodent Pondaungimys mentioned in Southeast Asia have been found in recent times. Other previously unassigned with absolute certainty findings suggest that stem-tail squirrels were once located in Asia.