This image from NASA Mars Reconnaissance Orbiter spacecraft shows modified barchan dunes with shapes that resemble raptor claws. The unusual morphology of these dunes suggests a limited supply of windblown sand.
Winds likely blew from the northeast resulting in elongate dunes with an asymmetric downwind point. The transverse crests of the smaller ripples/mega-ripple bed-forms surrounding the dune, echo the dominant downwind direction towards the southwest.
This locality is in the Northern Lowlands directly east of Dokka Crater in Scandia Cavi.
http://photojournal.jpl.nasa.gov/catalog/PIA19962