Years ago I cut pages out of a calendar planner that was illustrated with lovely British watercolors. I chose this one for my dinosaurs, but could not remember who the artist was (or the title for that matter). So I used a website I learned about from a gallery owner I used to work for. TinEye Reverse Image Search:
You upload an image and it will identify the image, IF the image is "out there". And this was! It is by Charles Ginner (1878-1952) and is in the collection of The Victoria & Albert Museum.