A new species of Eogruidae (Aves: Gruiformes) from the Miocene of the Linxia Basin, Gansu, China: Evolutionary and climatic implications

Despite having one of the most robust fossil records within core-gruiform
birds (rails, cranes, and allies), the biogeographic history of Gruidae
(cranes) and key drivers of diversification within this group remain
largely unknown. The Eogruidae of Eurasia represent some of the earliest
known crane-like fossils. Here, we present description of a new species
represented by a well-preserved specimen of a foot from the late Miocene
(7–6.5 mya) Liushu Formation of Linxia Basin, Gansu, China. It is the only
eogruid fossil that has been found in this formation and is the first
eogruid known from northwest China. Linxia Basin is located along the
margin of the northeastern Tibetan Plateau, which allows for new insight
into Miocene dispersal of the Eogruidae and potential climatological and
geological connections. It is also the first specimen with an associated
tarsometatarsus and nearly complete phalanges, including a claw, which
provides further morphological information on this taxon. Referral of the
new specimen to Eogruidae is based on extreme reduction of the trochlea of
metatarsal II, which is most similar to the condition present in the
eogruid subclade traditionally termed Ergilornithidae.