Qianshanornis: A Strigogyps-like Paleocene Bird From China With a Hyperextensible Second Toe

Qianshanornis rapax, gen. et sp. nov. (holotype, IBCAS QS027), from the middle Paleocene Wanghudun Formation of the Qianshan Basin in China, left foot in dorsal (A), dorsomedial (B), ventrolateral (C), lateral (D), and medial (E) views; F, Strigogyps sapea from the middle Eocene of Messel in Germany (SMF Me 1819), left tarsometatarsus in dorsal view; G–J, Qianshanornis rapax (holotype, IBCAS QS027), distal end of left foot in dorsodistal (G), dorsal (H), ventrolateral (I), and medial (J) views; K–M, first phalanx of left second toe of (K) Qianshanornis rapax, gen. et sp. nov. (holotype, IBCAS QS027, with matrix digitally removed), (L) Cathartes aura (Cathartidae), and (M) Cariama cristata (Cariamidae). In A–E the phalanges are numbered. Abbreviations: blg, dorsal bulge of distal end of first phalanx of second toe; ext, sulcus extensorius; fos, fossa on plantar surface of trochlea metatarsi II; fvd, foramen vasculare distale; phl, fossa parahypotarsalis lateralis. Scale bars equal 10 mm; same scale bar for A–E and G–I, respectively.

A Strigogyps-like bird from the middle Paleocene of China with an unusual grasping foot

Authors:

1. Gerald Mayr (a)
2. Jian Yang (b)
3. Eric De Bast (c)
4. Cheng-Sen Li (b)
5. Thierry Smith (b)

Affiliations:

a. Senckenberg Research Institute and Natural History Museum Frankfurt , Ornithological Section, Senckenberganlage 25, D-60325 , Frankfurt am Main , Germany

b. Institute of Botany, Chinese Academy of Sciences, State Key Laboratory of Systematic and Evolutionary Botany , Xiangshan , Beijing , 100093 , People's Republic of China

c. Royal Belgian Institute of Natural Sciences, Department of Paleontology , Rue Vautier 29, B-1000 , Brussels , Belgium

Abstract:

We describe a new avian species, Qianshanornis rapax, gen. et sp. nov., from the middle Paleocene Wanghudun Formation of the Qianshan Basin in Anhui Province, China. The holotype consists of an incomplete articulated foot and a few associated bones, mainly of the leg, wing, and pectoral girdle. Qianshanornis rapax is characterized by a derived foot morphology and may have had a hyperextendible second toe, which has so far only been reported for some Mesozoic taxa. The new species is markedly different from all other known Cenozoic birds and is here classified in the new taxon Qianshanornithidae. The leg bones, especially the distal end of the tibiotarsus, most closely resemble those of Strigogyps (Ameghinornithidae) from the Eocene, and possibly Oligocene, of Europe, but unlike the latter, the much smaller Q. rapax appears to have had well-developed flight capabilities.