The first species to be included,
Ambiortus dementjevi, lived sometime during the
Barremian age between 136.4 and 125 million years ago in today's
Mongolia.
A. dementjevi belongs to the
Ornithuromorpha (the group containing modern birds but not
enantiornithes), according to all published
cladistic analyses. However, the exact position of the species within this group has been controversial. Most analyses have found it to be either an unresolved member of the
Ornithurae, or a more primitive member of
Ornithuromorpha. One 2006 study, for example, found it to be more primitive than
Yanornis but more advanced than
Hongshanornis, or even a member of the specific group containing both
Yanornis and
Yixianornis. ==Inclusions==