1991; Lowenstein & Scheuenstuhl 1991; Child & Pollard 1992; Nerlich em et al /em . a variety of these exceptional assemblages, from a spectrum of depositional and diagenetic environments, is an important way of assessing biomolecular preservation, because normal diagenetic processes are both slower and less extensive than those simulated in laboratory experiments. Despite scepticism regarding the premise of long-term molecular survival based on laboratory experiments and predictions of molecular kinetics, many studies have shown that amino acids, short peptides, and amino sugars can persist within fossils over a wide geological age distribution (e.g. Weiner em et al /em . 1976; Westbroek em et al /em . 1979; Armstrong em et al /em . 1983 and references therein; Lowenstein 1981, 1985; Ostrom em et al /em . 1990; Collins em et al /em . 1991; Gurley em et al /em . 1991; Muyzer em et al /em . 1992; Stankiewicz em et al /em . 1997 em a /em , em b /em , 1998; Schweitzer em et al /em . 1997 em a /em , em b /em , 1999 em a /em , em b /em , 2002; Poinar em et al /em . 1998; Collins em et al /em . 1999). Immunological techniques have identified antigenic compounds in fossils of varying ages and from various source taxa (e.g. Rowley em et al /em . 1986; Muyzer & Westbroek 1989; Baird & Rowley 1990; Collins em et al /em . 1991; Lowenstein & Scheuenstuhl 1991; Child & Pollard 1992; Nerlich em et al /em . 1993; Franc em et al /em . 1995; Borja em et al /em . 1997; Schweitzer em et al /em . S49076 S49076 2002) including Cretaceous fossils (Collins em et al /em . 1991; Muyzer em et al /em . S49076 1992; Schweitzer em et al /em . 1997 em b /em , 1999 em a /em , em b /em ). To preserve fossils in an exceptional manner requires early cessation of diagenetic processes, and is attributable to unusual physical and chemical conditions from death through diagenesis, and minimal alteration of fossil material at the macro and microscopic levels. This, in turn, is usually correlated with the preservation of endogenous biomolecules, fragments of molecules, or biomarkers (i.e. altered molecular fragments that can be traced to the original source, e.g. Hagelberg & Clegg 1991; Hedges 2002; Schweitzer em et al /em . 2002). Because molecular preservation has been correlated with morphological and microstructural preservation (e.g. Hagelberg & Clegg 1991; Marota & Rollo 2002), optimizing the search for endogenous organic components within fossil specimens should involve S49076 careful selection of fossil specimens for study. Analyses of such extraordinary samples are a direct test of survivability of biomolecules. However, molecular analyses of fossils present unique challenges. In part, this is because chemical modifications occur during diagenesis (Mycke & Michaelis 1985; Rafalska em et al /em . 1991; Poinar em et al /em . 1998). These modifications include breaking peptide bonds, removal or alteration of original amino acid side chains, and cross-linking of peptide fragments to other organic degradation products, a process that makes organic material insoluble and difficult to separate into constituent compounds (Macko & Engel 1991; Poinar em et al /em . 1998). Condensation reactions along this pathway may result in the formation of hydrocarbons from proteinaceous precursors. Because these products are hydrophobic and because the original organics are contained within a biomineralized matrix (Weiner em et al /em . 1989; Glimcher em et al /em . 1990; Sykes em et al /em . 1995), the chances of retention of organic material that contains remnants, however altered, of the original compounds are greatly increased. The strong petroliferous odour released upon decalcification of the eggshell supports this pathway of degradation in these eggshells. A lipid-containing molecular complex of degraded organics and antigenic material may explain some of the anomalies seen in our data. For example, low reactivity of antibodies with dinosaur antigen by ELISA may be owing to insufficient immobilization of antigen resulting from lipid or hydrocarbon mixing Bnip3 with the antigens. Finally, while the organic material extracted from dinosaur eggshells shows characteristics consistent with extant material similarly derived, it is recognized that this antigenic material may or may not be derived from proteinaceous precursors, and is surely diagenetically altered from its original state. We do not claim here that this material represents complete proteins. Indeed, epitopes are known to be only a few amino acids in length (Child & Pollard 1992); therefore, it is possible that antigenic response may be owing to selective preservation of a few peptides, or even altered, fossilized derivatives of peptides. The antisera that we have prepared may be used to purify the antigenic material through affinity isolation techniques. It may then be possible to.