Animals with four, six and eight legs are widespread while the concept of seven legs (fictitious Heptapods) are the makings of amazing scifi short stories and blockbuster movies.
Are starfish the only types of animals currently (or ever) with five mostly equal sized appendages and substantial five-fold symmetry? Are there theories why five is unusual on land but common in the sea?
update: There is an interesting subtlety here. This answer points out that a sea star's legs are the little things under the five appendages, so I've adjusted the question to address instead five-fold symmetry and five appendages.
below: "Ophiopetra lithographica from the Lower Hienheim Beds (Lower Tithonian,Upper Jurassic) near Regensburg, Germany" from here.
below: "A green brittle star - Ophiarachna incrassata" from here.
below: "Une ophiure superbe (Ophiolepis superba) à la Réunion." from here.