My recent find

 My recent problematic find. At first I thought it was a theropod footprint. On a second glance it seemed ornithopod. Now I am thinking - ankylosaur. If so, they were really abundant along the ancient coast.

Yes, it fits the shape of a large Polacanthid left pes impression.

Giant ankylosaurs

  Here are the pes footprints of the two giant ankylosaurs (not to scale) with my interpretations on the right:

Pula Albian (mid-Cretaceous) ankylosaur right pes lenght: 85-95 cm (A, B) - I am standing on it's toe #5 of it's four pes toes;

Tumbler Ridge (Canada) late Cretaceous anky has a scale of 10 cm for size comparison (about 44 cm total pes length) (E, F) Photo credit: Rich McCrea. 

 I know it sounds unbelievable, but the Pula ankylosaur, as derived from the size of the largest pes footprints (there are at least 6 of the foot impressions at the Pula site) must have measured some 14-16 meters in length (!)  In a way it wasn't that surprising to me, since all of the super mega fauna members from Pula site were world record holders. Check out my title banner: these are the ultra dinosaurs from Pula in scale (!) They were gregarious, as it seems from the fossil record. Maybe comprising of small family groups. A pair or more adult dinosaurs guarding and taking care of their offspring.
It is interesting that some members of  Thyreophora - a subgroup of the ornithischian dinosaurs
which include well-known suborders Ankylosauria and Stegosauria, had diverse number of toes.
While some of the ankylosaur ichnogenera had three, the others had four toes on their hind feet.
Thus it is possible to miss identify the thyreophoran three-toed pes tracks for iguanodontoid ones and vice versa, especially if the front feet impressions are missing or are poorly preserved. Despite of the enormous record size of the Pula, Istrian tracks it is less likely that these were artifacts.

The Tumbler Ridge site

Ankylosaur tracks

 From 2010-2012 I have also discovered a few ankylosaur tracks near Pula. There were even possible baby ankylosaur prints. However, the most impressive are the giant pes footprints measuring some 75 cm in length. In the pictures below are a couple of nicely preserved ones, left by somewhat smaller individuals. However they were still large by any standards. Compare the tips of my shoes for size. The ankylosaur was probably similar to Polacanthus or Sauropelta. The upper images apparently represent the right pes, while the lower ones feature the left pes.

Compare to some of the footprints from Tumbler Ridge. See the Anky trackway
More tracks.