Complex sentence: In 1857 he acquired curatorial duties formerly held by Johann Jakob Heckel (1790-1857), and subsequently became in charge of the bird (1857) and mammal (1869) collections.
Split into simpler sentences: In 1857 he acquired curatorial duties formerly held by Johann Jakob Heckel (1790-1857). Subsequently, he became in charge of the bird (1857) and mammal (1869) collections.