( ( ( a ( basal polytomy ) ) ( of ( ( clades , ) ( ( ( ( all but ) one ) ( of which ) ) ( have ( ( ( ( ( circular valves ) ( -LRB- ( ( very ( rare exceptions ) ) -RRB- ) ) ) ( with ( a ( centric ( valve pattern ) ) ) ) ) and ) ( ( ( ( monopolar or ) ( radial symmetry ) ) ; ) ( ( the clades ) ( with ( ( ( circular valves ) and ) ( centric organization ) ) ) ) ) ) ) ) ) ) ) ( ( ( are often ) ( ( referred to ) ( as ( the ( ` ( radial ( centrics ' ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT a) (JJ basal) (NN polytomy)) (PP (IN of) (NP (NP (NNS clades)) (, ,) (SBAR (WHNP (WHNP (QP (DT all) (CC but) (CD one))) (WHPP (IN of) (WHNP (WDT which)))) (S (VP (VBP have) (NP (NP (NP (NP (JJ circular) (NNS valves)) (PRN (-LRB- -LRB-) (NP (JJ very) (JJ rare) (NNS exceptions)) (-RRB- -RRB-))) (PP (IN with) (NP (DT a) (JJ centric) (NN valve) (NN pattern)))) (CC and) (NP (NP (NP (NN monopolar)) (CC or) (NP (JJ radial) (NN symmetry))) (: ;) (NP (NP (DT the) (NNS clades)) (PP (IN with) (NP (NP (JJ circular) (NNS valves)) (CC and) (NP (JJ centric) (NN organization))))))))))))) (VP (VBP are) (ADVP (RB often)) (VP (VBN referred) (S (VP (TO to))) (PP (IN as) (NP (DT the) (`` `) (JJ radial) (NN centrics) ('' '))))) (. .)))
a basal polytomy of clades, all but one of which have circular valves (very rare exceptions) with a centric valve pattern and monopolar or radial symmetry; the clades with circular valves and centric organization are often referred to as the 'radial centrics'.
(ROOT (S (NP (DT A) (NN clade)) (VP (VBZ is) (NP (NP (CD one) (NN way)) (PP (IN of) (NP (VBG classifying) (NNS organisms))))) (. .)))