Skip to main content
. 2015 Nov 11;10(11):e0141304. doi: 10.1371/journal.pone.0141304

Fig 12. Posterior migration and enlargement of nasofrontal suture with growth in brachylophosaurins.

Fig 12

In subadult Brachylophosaurus, the nasofrontal suture covers 50–75% of the dorsal frontal surface; in adults, the nasofrontal suture covers the entire dorsal surface. In Brachylophosaurus specimens from the Comrey Sandstone Zone of the middle Oldman Formation and its Judith River Formation equivalent in Malta, Montana (solid black circles; CMN 8893, JRF.65, MOR 940, and MOR 1071 specimens C-3-3, 6-30-98-4, 7-13-99-87-I, and 7-7-98-86), the relative coverage of the nasofrontal suture increases with frontal length until the frontal is entirely covered by the nasofrontal suture. Larger adult Brachylophosaurus braincases from an unknown stratigraphic height in the Oldman Formation of Alberta (open squares; FMNH PR PR 862, TMP 1990.104.001) and the Upper Judith River Formation of central Montana (open triangle; MOR 720; stratigraphic height relative to Oldman Formation of Alberta unknown) also have the frontals entirely covered by the nasofrontal suture. Probrachylophosaurus gen. nov. from the Montana Judith River Formation equivalent of the lower Oldman Formation (black x; MOR 2919) differs from the Brachylophosaurus growth trajectory in having a subadult Brachylophosaurus degree of coverage in an adult sized skull.