There is interest in assembling a robust hypothesis of animal relation
ships based on molecular and other character-based evidence, but even
if a high degree of phylogenetic resolution is available, there remain
challenging problems for postulating ancestral larval traits. This di
stinction between hypotheses of genealogies and our knowledge of speci
fic traits is illustrated with specific examples of the portion of var
iable larval traits that are homoplastic (i.e., they require convergen
ces, parallelisms, or character reversals) with respect to specific mo
lecular-based genealogical hypotheses. Corresponding molecular studies
suggest (1) maximal incongruity in larval form and metamorphosis for
extant echinoderm classes, (2) convergences in larval size and form as
sociated with coloniality in ascidians, (3) multiple losses of the loc
omotory larval tail in molgulid ascidians, (4) multiple losses of larv
al feeding and gain of apomictic parthenogenesis within a genus of biv
alves, (5) multiple losses of larval feeding in echinoids, (6) alterna
tive explanations of the distribution of feeding and non-feeding larva
e among gastropods, and (7) recent modifications in embryonic and larv
al development of echinoids following prolonged stasis. These examples
show that inferences from phylogenetic studies will ultimately be lim
ited by the extent to which homoplasy and polarity can be unambiguousl
y assessed for larval traits. These limitations are illustrated by alt
ernative hypotheses for larval trait synapomorphies among phyla, evolu
tion of feeding with opposed prototrochal and metatrochal ciliary band
s, and the retention or reacquisition of the locomotory nauplius of th
e Euphausiacea and Dendrobranchiata. inferences on the evolution of la
rval traits require other sorts of evidence, perhaps including informa
tion on the evolution of genes that play important roles in morphogene
sis and their sites of expression.