Figure 7.The opercular series of †Chondrosteus,†Peipiaosteus,and representatives of all genera of Acipenseridae: †Chondrosteus(a –
redrawn from Woodward 1889) and †Peipiaosteus(b – redrawn from Zhou 1992) possess serial branchiostegals (bsg) supporting the
operculum beneath the subopercle (sop). Acipenserids (c, d, f) typically possess two branchiostegals (Character7),with a vertical,
rectangular first branchiostegal (bsg1) and small second branchiostegal (bsg2).Scaphirhynchus(e) possesses a short, triangular first
branchiostegal (Character 62).The subopercle of scaphirhynchines is dorsoventrally compressed with an anteroposteriorly elongate
shape (Character 47).
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