Aberrant Arm Branches in Pennsylvanian Crinoids from the Moscow Region.

Middle–Upper Carboniferous (Pennsylvanian) crinoids with aberrant arm branches from the Moscow region are studied. It is shown that aberrations in the arm branches can be the result of mechanical damage during incorrect (augmentative) regeneration, as previously assumed, or the result of initial phenotype disorders. The latter cases show the evolutionary potential of the group. Consolidation of such aberrations in the phylogenies of certain groups of crinoids led to speciation and formation of new taxa. [ABSTRACT FROM AUTHOR]