The picture on the right was taken in the late afternoon. The leaves are more horizontal and almost unfolded. They rise to a vertical position, similar to what happens at midday. Well, Calathea is a monocot, a grass-like plant. Since all the leaf petiole cluster around a single basal region of the plant, if all the leaves tipped downward, they would get rather tangled up and sit on top of one another.
Maranta is another genus in the Marantaceae.
The picture on the left below is of a specimen of Maranta in diffuse daylight, during the late afternoon. The picture on the right shows another Maranta at night. Plants which are not heliotropic often show more vertical leaves at the top of the plant and more horizontal leaves near the bottom. Not all members of these families are heliotropic, however. Most of the legumes are heliotropic but a few are not.