A key feature of all mammal species are the presence of hairs on the epidermis, which act as an insulating layer and play an important role in maintaining body temperature. The structure of the hair may be of taxonomic importance, in fact, many identifications in the field and forensic studies are based on the recovery and determination of tufts of hair torn from the animal. Thanks to these studies, for example it was possible to identify the skins used by "Iceman" as garments, including goat and deer. The distinctive characteristics of mammals have hair.
- The external structure of the hair: the shape and arrangement of the axis of the hair cuticular scales.
- The edge of the individual scales.
- The size and spacing of the edges of individual chips compared to the whole hair.
- The cross-sectional and longitudinal the hair and the shape of the central cavity (medulla)
Fig.1. features to describe the hair of mammals (from Backwell et al. 2009). - provision to the axis of the strands of hair
- form of individual chips
- form the edges of individual chips
- distance of the edges of individual chips ("magnitude scales")
Figure 2. examples of fine structures observed by electron microscopy. a, b) vervet ( Chlorocebus sp.) , c) galago (Galago sp. ), d) human (Homo sapiens ), taken from Backwell et al. 2009. With the advent of genetic techniques, if found in a hair follicle is still intact can also be made by identifying the DNA of cells.
Although Ceratina, they are made of mammalian hair is strong enough to weather the weather, remains or imprints of hair of mammals are quite rare in the geological record. During the fossilization must present special conditions (eg anoxic environment or dry), and scavengers who love Ceratina as a snack (eg beetles dermistidi) should not have access to the exhibit.
From Chinese Paleocene (ca. 59 to 56 million of years) are known fossil imprints of hair, kept in the faeces of carnivorous mammals and birds of prey. The preservation is so perfect that it was possible to observe the individual scales of the hair and give the remains at least four species, possibly including a representative of the genus Lambdopsalis a Multitubercolato relatively large for its time. The discovery confirms that these ancestors of modern mammals possessed an insulating layer made of hair.
from China is also the oldest placental mammal with a lot of hair: Eomaia scansoria . The fossil was found in the Yixian Formation (Liaoning Province), dated to the Cretaceous (125 million years). The complete skeleton preserved in anatomical connection, and is surrounded by the outline of the thick fur.
hairs are known in amber of the Miocene of the Dominican Republic and the Baltic Sea, and from the Cretaceous of France has been described the oldest example so far known. in the permafrost of Siberia and Canada have been preserved intact the nap of mammoths and other animals of the Pleistocene.
The oldest evidence of human hair known until the last year the remains were found on a mummy of the people of Chincorro (Northern Chile), dated to 9,000 years, but a hyena coprolite of more than 200,000 years old was described quello che viene interpretato come l’ impronta di peli delle prime specie di Homo .
BIBLIOGRAFIA:
BACKWELL, L.; PICKERING, R.; BROTHWELL, D.; BERGER, L.; WITCOMB, M.; MARTILL, D.; PENKMAN, K. & WILSON, A. (2009): P robable human hair found in a fossil hyaena coprolite from Gladysvale cave, South Africa. Journal of ARcheological Science 36: 1269-1276
JI, Q.; LUO, Z.-X.; YUAN, C.X.; WIBLE, J.R.; ZHANG, J.-P. & GEORGI, J.A. (2002): The earliest known eutherian mammal. Nature (416): 816-822
MENG, J. & WYSS, A.R. (1997): Multituberculate and other mammal hair recovered from Palaeogene excreta. Nature 385(6618): 712-714
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