Of course, this point is often raised when people are skeptical of evolution. I recall one article a few years ago in which a few footprints of a previously unknown dinosaur were discovered. Based on less than ten footprints, the scientists declared the height of the animal, the diet of the animal, it's ability to swim as well as to walk, the age in which it lived, and where it fit on a complex evolutionary tree.
Solid? Repeatable? Empirical data? It was all guesswork.
Science used to mean something.
Theres always been guesswork and extropolation. The dino example you used would have been extrapolated from depth of the print,the likely condition of the soil at the time,other better understood or shall i say better known dinos with greater historical records. Its not scientific method with repeatable results but its the best that can be done with the information available.