Thursday, April 30, 2015

[Paleontology • 2015] Yi qi • A Bizarre Jurassic Maniraptoran Theropod with preserved Evidence of Membranous Wings

Yi qi | ‘ee chee’
Xu, Zheng, Sullivan, Wang, Xing, Wang, Zhang, O’Connor, Zhang & Pan, 2015

A farmer first spotted the dinosaur fossil in the Tiaojishan Formation of Hebei Province, China, dating to the Middle–Upper Jurassic period, or about 160 million years ago. The dinosaur is a member of a group of theropods (mostly carnivorous dinosaurs) called Scansoriopterygidae.
photo: Zang Hailong

The wings of birds and their closest theropod relatives share a uniform fundamental architecture, with pinnate flight feathers as the key component. Here we report a new scansoriopterygid theropod, Yi qi gen. et sp. nov., based on a new specimen from the Middle–Upper Jurassic period Tiaojishan Formation of Hebei Province, China. Yi is nested phylogenetically among winged theropods but has large stiff filamentous feathers of an unusual type on both the forelimb and hindlimb. However, the filamentous feathers of Yi resemble pinnate feathers in bearing morphologically diverse melanosomes. Most surprisingly, Yi has a long rod-like bone extending from each wrist, and patches of membranous tissue preserved between the rod-like bones and the manual digits. Analogous features are unknown in any dinosaur but occur in various flying and gliding tetrapods, suggesting the intriguing possibility that Yi had membranous aerodynamic surfaces totally different from the archetypal feathered wings of birds and their closest relatives. Documentation of the unique forelimbs of Yi greatly increases the morphological disparity known to exist among dinosaurs, and highlights the extraordinary breadth and richness of the evolutionary experimentation that took place close to the origin of birds.

The dinosaur would have sported a robust skull with a short snout
photo: Zang Hailong

Figure 1: Yi qi holotype (STM 31-2).
a, b, Photograph (a) and line drawing (b) of specimen; c, skull and mandible in lateral view; d, premaxillary tooth in lateral view; e, left manus; f, styliform elements (the distally unexposed left styliform element articulates with the wrist, and the orientation of the right styliform element implies a similar relationship to the carpus even though its proximal part is missing). Light and dark grey shading indicates feathers and membranous tissues, respectively. an, angular; cv, cervical vertebrae; d, dentary; dr, dorsal ribs; emf, external mandibular fenestra; en, external naris; f, frontal; lf, left femur; lh, left humerus; lmd2–4, left manual digits 2–„4; lmt, left metatarsals; lr, left radius; ls, left scapula; lse, left styliform element; lu, left ulna; mb, mandible; mcII–IV, metacarpals II–IV; n, nasal; or, orbit; p, parietal; phII1 to IV4, phalanges II‐1 to IV‐4; pma, premaxilla; rmd2–4, right manual digits 2–„4; rf, right femur; rfi, right fibula; rh, right humerus; rmc, right metacarpals; rmt, right metatarsals; rr, right radius; rse, right styliform element; rt, right tibiotarsus; ru, right ulna; sk, skull. Scale bar, 2 cm.

Figure 3: Simplified coelurosaurian phylogeny showing the recovered position of Yi.
The skeletal silhouette and two possible alternative planform reconstructions of Yi highlight the proportionally long and robust forelimbs and large leg feathers that Yi shares with other basal paravian theropods, indicating the presence of aerial capability, and the inferred membranous wings, a feature unique among known paravians but seen in most other gliding or flying tetrapods. Various uncertainties, such as how the styliform element is oriented and whether membranous tissue is present lateral to the trunk as in most volant tetrapods, imply that a variety of reconstructions of the aerodynamic apparatus of Yi are currently plausible (see Supplementary Information for additional possible reconstructions).

Theropoda Marsh, 1881

Maniraptora Gauthier, 1986

Scansoriopterygidae Czerkas et Yuan, 2002

Yi qi gen. et sp. nov.

Etymology. The generic and specific names are derived from Mandarin Yi (wing) and qi (strange), respectively, referring to the bizarre wings of this animal. The intended pronunciation of the name is roughly “ee chee”.

Holotype. STM 31-2 (housed at the Shandong Tianyu Museum of Nature), an articulated partial skeleton with associated soft tissue preserved on a slab and counter slab. The specimen was collected by a local farmer, but its provenance and authenticity have been confirmed by multiple lines of evidence including sedimentology, taphonomy and computed tomography (CT) data.

Locality and horizon. Mutoudeng, Qinglong County, Hebei Province, China. Tiaojishan Formation, Callovian–Oxfordian stage. On the basis of the provenance of the specimen, Yi qi is a member of the Daohugou (or Yanliao) Biota.

Preserved features of the "winged" dinosaur fossil reveal feathers over the neck (not shown), along the humerus (b) and along the humerus and ulna (c). The fossil also showed soft tissue and feathers along the right forelimb and hindlimb.
photo: Zang Hailong | doi: 10.1038/nature14423

Xing Xu, Xiaoting Zheng, Corwin Sullivan, Xiaoli Wang, Lida Xing, Yan Wang, Xiaomei Zhang, Jingmai K. O’Connor, Fucheng Zhang and Yanhong Pan. 2015. A Bizarre Jurassic Maniraptoran Theropod with preserved Evidence of Membranous Wings.
Nature. doi: 10.1038/nature14423

In Photos: Bizarre 'Bat Dinosaur' Discovered in China  @LiveScience
Chinese Dinosaur Had Bat-Like Wings and Feathers via @ngphenomena
Is it a bird? Is it a bat? Meet Yi qi, the dinosaur that is sort of both
Yi qi by Sheather888