3. "the distal head of the femur has a lateral crest;" Absent in
Archaeopteryx (Chiappe, 2002).
Distal head? What does that mean?
Some enantiornithines (e.g. Neuquenornis, Concornis) have a crest continuous
with the lateral condyle, extending along the posterolateral margin of the
distal shaft. Halimornis lacks it.