Even in so short an interval as that between the first and second editions of Pictet's great work on Palaeontology, published in 1844-46 and in 1853-57, the conclusions on the first appearance and disappearance of several groups of animals have been considerably modified;
1844-46 eta 1853-57ean argitaraturiko Pictet-en Palentologiako liburu ederraren lehen eta bigarren edizioen artean izaniko tarte hain motxean ere, zenbait animali talderen lehen agerpenari eta desagerpenari buruzko ondorioak nahiko aldatu dira;