At first, alvarezsauroids were thought to have been originated in
South America. However, the discovery of
Haplocheirus, and its basal phylogenetic position, as well as its early temporal position, suggests they derived in
Asia rather than
South America. Xu
et al. (2011) suggested that at least three dispersal events of alvarezsauroids took place; one from Asia to
Gondwana, one from
Gondwana to Asia, and one from Asia to
North America. This hypothesis is consistent with faunal interchanges. Their results showed an absence of statistical support for previous biogeographic hypotheses that favour pure vicariance or pure dispersal scenarios as explanations for the distributions of alvarezsauroids across South America, North America and Asia. They instead found that statistically significant biogeographic reconstructions suggest a dominant role for sympatric events ("within area" ones), combined with a mix of vicariance, dispersal and regional extinction. The Asian origin of alvarezsauroids is also bolstered by the discovery of alvarezsaurid specimens from the Turonian-age
Bissekty Formation (some of which were named
Dzharaonyx in 2022) of Uzbekistan and
Bannykus,
Tugulusaurus, and
Xiyunykus from the Early Cretaceous of China. However, Makovicky
et al came to a different conclusion based on the description of a new specimen of
Alnashetri, finding support for the group having a
Pangaean ancestral distribution shaped by a combination of vicariance and regional extinctions of basal lineages, leading the disjunction distribution of various divergent clades across landmasses. ==References==