The word petrosomatoglyph comes from the Greek petros ("stone"), soma ("body"), and glyphein ("to carve"). So petrosomatoglyph is an image of parts of a human or animal body incised in rock. Feet are the most common; however, knees, elbows, hands, head and fingers, etc. are also found.
The term "petrosomatoglyph" should not be confused with "petroglyph", which covers all incised representations of living or non-living things, or with "pictograph" , which is an image drawn or painted on a rock face, and both of which contribute to the wider and more general category of rock art. Petroforms, or patterns and shapes such as labyrinths and mazes made by many large rocks and boulders in rows over the ground, are also quite different.
Earliest petrosomatoglyphs are on rockbeds around the world. For example dinosaurs, other ancient animals and even early homidis footprints are found. In picture [1] 1.5-million-year-old prints found in Kenya.
In early middle ages petrosomatoglyps were created for example by the ancient Celtics peoples. Like carved footprint im Dunadd, Scotland [2].
They were an important form of symbolism, used in religious and secular ceremonies, such as the crowning of kings.
Modern petrosomatoglyphs are seen for example on concrete buildings, bridges and pavements on streets or like in forecourt of Grauman's Chinese Theatre [3]. Making footprints in stone of family members is part of New Age beliefs. Some of petrosomatoglyps are done in artistic way. They are found on museums, parks and even some reststop areas can have these to amuse their visitors.
Yet some are formed just by accident when human or animal have walked on wet concrete or asphalt pavement like in picture taken from bridge in Porvoo, Finland.
Link to wikipedia for more information