H.J. Ruiz – Avian101

Gastornithiformes are an order of prehistoric birds. The birds from this group lived from the Paleocene to the Eocene and were spread out across Asia, Europe, and North America. All the birds were very large birds that were flightless, similar to an ostrich but more heavily built and with a huge beak. They are generally assumed to be predators, but this is conjectural. It is likely though that they included a considerable amount of meat in their diet, although they may have been scavengers rather than active hunters.

Gastornithifomes

There is no agreement on the relationships of the Gastornithiformes. They were long and still are sometimes placed with the Gruiformes as a family Gastornithidae. The Gruiformes seem paraphyletic though, with some lineages that are exclusively Gondwanan but apparently not closely related to cranes, rails and allies which are common in Eurasia and Africa but far less so in the Americas. Some others, probably unrelated to either group, were very diverse in the Americas but prehistorically also occurred in Europe. Nothing is known of the ancestry of the Gastornithiformes; judging from biogeography, a relationship with either the true Gruiformes or the “Americas” lineage (which might include the seriemas and the phorusrhacids) is possible.

However, the early occurrence of the Gastornithiformes in the fossil record poses problems. These animals were highly apomorphic and thus the lineage must have evolved for significant time after diverging from their closest known relatives. Most purported relatives are not known nor suspected to have been so highly distinct at the time when the Gastornithiformes lived.