Fossils or what?(1)

This is a photograph was taken on the beach near Pula a few years ago. The rocks are of the early Cretaceous age (late Albian), I really can't figure out what has happened here around 100 million years ago. You can see some strange long groove-like traces (?) and five circles in a row in the centre of the photograph. Tip of my shoe is at the bottom of the photo for scale.
There are also some rudist fragments, some large ripple marks and possibly theropod footprints near by (not shown in this photograph).