'Cladida'
As you may have noticed, the taxon cladida is in single quotes
('Cladida'). The reason for this is not entirely clear, but a reasonable
guess would be that 'Cladida' is either a zero length branch often refered to
as a metataxon, or it could mean that cladida is also the name used to
identify the clade that includes Articulata, 'Cladida', Flexibilia, and Cyathocrinina.
The cladogram choosen for this exhibit is from Simms (1993:Reinterpretation
of thecal plate homology and phylogeny in the Class Crinoidea. Lethaia,
Vol. 26, pp. 303-312.), and he does specify that "The Cladida, incorporating
the Cyathocrinina, Flexibilia, and Articulata, ..." suggesting that he is
using the name Cladida for that clade, but he does not include the taxon
'Cladida' which, according to his cladagram, also belongs to this clade.
A discussion of 'Cladida' or why the taxon is in single quotes could not be
found. Please have a look at Michael J. Simms' paper for a more detailed
account of the Crinoidea.