Haeckel developed his tree over almost 1,000 pages, basing it on palaeontological, embryological and systemic data — a precursor to modern biology's phylogenetic trees.

Fragments of ostrich eggshells are abundant in Africa, and often found at archaeological and palaeontological sites.

Reproducing palaeontological results depends on unrestricted access to fossils described in the literature, allowing others to re-examine or reinterpret them.