What is the contents of fossil nests?

Answer 1

The above mentioned deposits are, however, absent from most of the area studied. The Carboniferous is covered by the Hipparion Clay, sometimes directly. Most often, however, there is a conglomerate bed of varying thickness (sometimes up to 4 m thick). The cobbles and the matrix are of calcium carbonate. The stratification is horizontal. Nonetheless, the conglomerate formed before the Hipparion Clay. Fossils cannot be found in it. Topographically the conglomerate can be recognised because it forms a layer between the highest slate-like members of the Carboniferous unit and the red clay. Being harder than either of these, it forms a frequently undercut projecting cliff in the ravines. It is noteworthy that its calcareous matrix is grey, while the carbonate layers in the Hipparion Clay are cemented by the red clay.

Above this lies the Hipparion Clay, red clay similar to that of Pikermi in every respect. The maximal observed thickness is about 65 m. A subdivision into different horizons cannot a priori be carried out because the commonly occurring shingle beds are not sufficiently continuous. However, they demonstrate that a horizontal stratification is present. Layers of carbonate concretions occur sparsely. A fossil-rich horizon appears in this clay about 1150 m (cf. the map). It is mined by the local population. The fossils of the fauna characterized by Hipparion Richthofeni Schl. appear in "nests," in which usually a great number of bones of the most different forms occur together in a restricted space, typically from 0.5 to 2.0 cubic meters in volume. Complete skeletons were not found, but more or less complete limb bones and parts of vertebral columns are present. Also, carnivore skulls appear with their mandibles attached, and this is also the case with the rhinocerids. These fossils are quite heavily mineralised, the marrow cavities are usually filled with crystals of calcite , and the surface appears pure white. The clay is infiltrated and hardened by calcite in the immediate vicinity of the fossil "nests." At times small sand lenses are embedded in the clay. They usually contain small fragments of bone. Often a certain stratification can also be recognised within the fossil "nests." In addition to the shingle layer, the clay also contains isolated cobbles of small size.

As already mentioned, the fossil "nests" all lay at one level, although there can be vertical variation of about 5 m, and, indeed, two fossil nests may lay one directly above the other, separated by a 1 m gap. Of the total thickness of Hipparion Clay, 25 m thus lie under and 35 m above the fossil level (see Figure 5). As for the fossil content of the nests, it is everywhere the same, i.e., no forms are limited to certain localities only. However, it must be noted that especially locality 30 at Tai-Chia-Kou [Daijiagou] contains almost exclusively larger ruminants and carnivores, in addition to rhinocerids, which are common everywhere. In Yang-Mu-Kou [Yang-Mu-Gou], locality 49, a fossil nest unusually rich in carnivore fossils was found. On another occasion, the remains of at least four pigs, which are otherwise quite rare, were found together in the smallest of spaces. The west-east extent of the region is 5.5 km, and the north-south extent is 5.0 km. The clay is covered by loess, which can reach a very considerable thickness. Once it covered the whole region, but in the course of time, the post-Tertiary streams have carved themselves in, so that the topography has by-and-large remained unchanged (see profile A-B, Figure 5). In support of this argument, it can be stated that in the side valleys, which are naturally younger, the contact between the Hipparion Clay and loess is always parallel to the modern surface. Fossils are not known from the loess in this region. Finally, the hilltops are mostly covered with eolian sand, a circumstance explained by the proximity of the Ordos Desert.

Answer 2

Fossil nests may contain preserved organic materials such as eggs, shells, bones, and plant materials. They can provide valuable information about the behavior and ecology of ancient organisms that built and used them. The contents of fossil nests can help paleontologists understand aspects of reproduction, nesting habits, and interactions between species in prehistoric environments.