Presence of double spines on the second preural centrum of the turbot (Scophthalmus maximus L., Pleuronectiformes : Scophthalmidae)

The literature concerning the presence of double spines on the second preural centrum in flatfishes is being reviewed and the different hypotheses proposed to account for this phenomenon are presented. A study using laboratory-reared specimens of the development of the caudal endoskeleton of the turbot on gives new data to explain the presence of this feature. Such double spines seem to be the result of a fusion during the ontogeny between the third preural centrum and the second preural centrum.