Berriasian-Maastrichtian dinosaur remains from South Mongolia (Gobi desert) are characterized by both excellent external appearance and good interior, textural and chemical preservation. Bone remains are carbonate-phosphate in composition with the texture of the Haversian canals preserved. Such preservation resulted from dinosaur burial in subaridic or aridic conditions as a result of mudflow action. All dinosaur remains are enriched in some volatile and trace elements (F, S, REE, Y, Sr, U, etc.), but, at the same time, are chemically heterogeneous. Considerable anisotropy is noted in trace element distribution between bones, egg-shell and coprolite. The bones and coprolite have similar carbonate-phosphate composition, but differ in trace element composition, with Y and HREE selectively accumulated in the bones. Different skeletal parts (vertebrae, extremities, ribs, skull, pelvis) are also heterogeneous with the maximum of trace element accumulation in the vertebrae. Epigenesis and sedimentation are not responsible for chemical heterogeneity of the dinosaur remains from Mongolia. Their observed composition formed no later than earliest diagenesis, that is, enrichment in trace elements can be attributed to vital processes and the earliest stage of diagenesis when original organic matter was still present in faunal remains. However, the considerable anisotropy in the distribution of some elements between different parts of the dinosaur skeleton cannot be explained completely by the processes of the earliest stage of diagenesis. Accordingly, it is assumed that dinosaur remains preserve some aspects of vital effects and original biochemistry of dinosaur bone tissues. Consistent changes in bone composition are observed during the course of the Late Cretaceous. Maastrichtian remains are characterized by maximum contents of fluorine and some trace elements. These data may be taken to indicate significant environmental changes in South Mongolia during the Late Cretaceous, especially in the Maastrichtian.