Definition of "penniform"

Even in the palaeolithic periods symbols abound such as cup markings, tectiforms, penniforms, groups of dots, rectangles, lattice designs, symbolic vulvas, and so on.

1970, Stuart Macdonald, The History and Philosophy of Art Education, Lutterworth Press, published 2004, page 335

Startlingly, the much earlier Blombos cave engravings clearly fit neatly into several of Von Petzinger's categories: lines, crosshatching, cruciforms, penniforms, and perhaps others.

2011, Pat Shipman, The Animal Connection: A New Perspective on What Makes Us Human, page 145

The symbols she found ranged from dots, lines, triangles, squares and zigzags to more complex forms like ladder shapes, hand stencils, something called a tectiform that looks a bit like a post with a roof, and feather shapes called penniforms. In some places, the signs were part of bigger paintings. Elsewhere, they were on their own, like the row of bell shapes found in El Castillo in northern Spain (see picture below), or the panel of 15 penniforms in Santian, also in Spain. […] The earliest known penniform is from about 28,000 years ago in the Grande Grotte d’Arcy-sur-Cure in northern France, and later appears a little to the west of there before spreading south. Eventually, it reaches northern Spain and even Portugal.

2016 November 12, “Hidden Symbols”, in New Scientist‎, number 3099, page 36