Abstract : The comparative study, didactic and historical, of problems in the field of palaeontology leads to a convergence in three levels about relations between problems and obstacles : the problem of the fossil origin linked to the artificialist obstacle, the problem of the fossil nature linked to the animist obstacle by spontaneous vegetation, the problem of fossil fauna identity in comparison with present-day fauna linked to “analogist” obstacle which is proposed. The collective construction of paleontological knowledge is analysed within the theoretical and methodological framework of questioning coming from three science debates in-class and four historical controversies among which two are original. The heuristic, argumentative and theoritical fonctions of these discussions are compared. We can end up in several levels of constructions of problems in didactic and in history of sciences ; and we can notice different process of paleontological knowledge, marked by the possibilities and the requirements mobilized by two communities under discussion. The interaction between construction of problem and obstacle is discussed as a brake or a mainspring of paleontological concepts –petrifaction, analogous or extinct fossil species, transformation by species'lineage, geological times. The notions of knowledge questioning and much debated as well as the polymorphic and recurrent obstacle are re-examined ; the notion of conditional necessity is suggested. They constitute three points of epistemological reference which can favour scientific teaching and learning with quality at primary school and at secondary school.