In 1961 Fell, in his monograph on the Ross Sea Ophiuroidea, drew attention to the development of skeletal excrecence in Antarctic ophiuroids from Euvondrea and Ophiosteira genera. Fell found no explaination for these outgrowths.
These expansions, especially in the dorsal arm plates, can also be seen in other Antarctic species such as Ophiura (Ophiuroglypha) carinifera, Anophiura banzarei, Ophiomages cristatus, Ophiomastus bispinosus and some species of Ophioplinthus genus.
Ignoring the mere evolutionary whim, there could be various interpretations. For example, passive defense: the protrusive elements could dissuade the predators which would prefer something easier to chew and swallow. Or, acting as peaked roofs somewhere in Siberia or Pirinei Mountains – little flat surface on aboral part protects them from heavy “snowfalls” and, so, doesn’t let them be buried in funds with a high degree of sedimentation. Or, the explanation could be the possible presence of amplifier lenses for photoreception (see symmetrical structures as honeycomb cells of Ophiosteira).
At any rate, nature manifests its spectacularity through the tiniest details of organisms which did not evolve to amaze us, nonetheless, we can’t help being marvelled at them.