It also contains over three dozen preserved gizzard stones, suggesting an
herbivorous diet.
_Lourinhanosaurus_ and _Poekilopleuron_ also had gastroliths, so I'm not
sure the presence of gastroliths is a reliable indicator of a herbivorous
diet. The authors compare _Archaeorhynchus_'s spatulate beak to that of
ducks, but note that the beak of _Archaeorhynchus_ lacks the "horny
lamellae" of a duck's bill. However, the more obvious comparison might be
to spoonbills, which feed on small water creatures (arthropods, little fish,
amphibians, etc).
The phylogenetic analysis of Zhou and Zhang (2006) puts both
_Confuciusornis_ and _Vorona_ in the Enantiornithes (sensu Sereno, 2005),
with _Confuciusornis_ as the sister taxon to (other) enantiornitheans. I'm
not sure how well-supported this _Confuciusornis_+Enantiornithes clade is,
but we could be heading toward some kind of Sauriurae clade.