Complex sentence: Between 1848 and 1853, cases of new material were shipping back to Leidy, but maddeningly only three more "Poebrotherium" tooth samples were among the remains recovered.
Split into simpler sentences: Between 1848 and 1853, cases of new material were shipping back to Leidy. Maddeningly, only three more "Poebrotherium" tooth samples were among the remains recovered.