The brachiosaurus is a sauropod with a unique and distinctive bump or dome on top of its head.
Current artists most often have chosen to model the brachiosaurus as though the dome was enclosed in skin rather than as a crest.
This Dayak culture depiction (1800’s) depicts the “dome” (if in fact this is a brachiosaurus) as a crest-not enclosed in skin.
It appears to us that the artist has possibly seen a live brachiosaurus and is depicting a slightly stylized version. It strikes us as well that depicting the animal this way indicates a high degree of familarity.
Of course, you’ll have to make up your own mind. The brachiosaurus and man are supposed to have missed each other by tens of millions of years.