Comparison of the femora of hesperornithiforms in cranial view (left-to-right: Fumicollis hoffmani UNSM 20030; Hesperornis regalis YPM 1200; Baptornis advenus AMNH 5101).

1, arrow indicates the profile of the trochanter, which is rounded in F. hoffmani and B. advenus but more angled in H. regalis. 2, arrow indicates the patellar sulcus, which is pocketed in H. regalis but not in F. hoffmani and B. advenus. Insets: 3, arrow indicates the flattened surface of the lateral condyle; 4, arrow highlights the difference in distal extents of the medial and lateral condyles. In F. hoffmani and B. advenus the lateral condyle extends further distally, while in H. regalis the condyles have a similar extent, with the medial very slightly further than the distal. Insets are shown scaled to be of similar size to F. hoffmani. Abbreviations: h, head; lc, lateral condyle; mc, medial condyle; ps, patellar sulcus; tr, trochanter.