Epidexipteryx hui Zhang &amp; Zhou &amp; Xu &amp; Wang &amp; Sullivan 2008, gen. et sp. nov.
Creators: name: Zhang, Fucheng
name: Zhou, Zhonghe
name: Xu, Xing
name: Wang, Xiaolin
name: Sullivan, Corwin
Publisher: name: Zenodo
Year: 2008
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Dinosauria
Scansoriopterygidae
Epidexipteryx

description: <i>Epidexipteryx hui</i> gen. et sp. nov. <b>Etymology.</b> <i>Epidexi</i> (Greek): display; <i>pteryx</i> (Greek): wing, feather; <i>hui</i>, in honour of the late young palaeontologist Yaoming Hu, who 1 Laboratory of Evolutionary Systematics of Vertebrates̡ Institute of Vertebrate Paleontology and Paleoanthropology̡ Chinese Academy of Sciences̡ PO Box 643̡ Beijing 100044̡ China. contributed significantly to the study of Mesozoic mammals from China. Generic name pronounced ‘ep-id-ecks-IP-ter-icks’. <b>Holotype.</b> A feathered pigeon-sized skeleton, preserved on part and counterpart slabs, and housed at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, collection number IVPP V15471 (Fig. 1; see Supplementary Information). <b>Locality and horizon.</b> Daohugou, Ningcheng County, Inner Mongolia, north China. The age of the Daohugou sediments is contentious, with possible dates ranging from Middle Jurassic 7 to Early Cretaceous. However, published radioisotopic dating results span a narrower range from 152 to 168 Myr (Middle to Late Jurassic) 8 – 10. <b>Diagnosis.</b> Medium-sized avialan with four elongate ribbon-like tail feathers (ETFs), highly procumbent and significantly enlarged anterior teeth, and a distally tapering pygostyle-like structure formed by ten unfused caudals at the end of the tail (Figs 1 and 2; see Supplementary Information). Differs significantly from <i>Epidendrosaurus</i>, the only other known scansoriopterygid, in caudal morphology (tail 70% of trunk length in <i>Epidexipteryx</i>, compared with more than 300% in <i>Epidendrosaurus</i>; 16 caudal vertebrae in <i>Epidexipteryx</i>, compared with more than 40 in <i>Epidendrosaurus</i>; caudal prezygapophyses reduced in <i>Epidexipteryx</i> but significantly elongated in <i>Epidendrosaurus</i>). <b>Description and comparisons.</b> <i>Epidexipteryx</i> is estimated to be 164 g in body mass (see Supplementary Information), smaller than most other basal avialans 3,11. The holotype probably represents a subadult individual, because the ends of some of the long bones seem imperfectly ossified. As in oviraptorosaurs 12, the skull is high in lateral view (height about 60% of length), the external naris is positioned high on the snout, and the parietal is proportionally long. The teeth of both the upper and lower jaws are highly procumbent, a feature previously known only in the ceratosaurian <i>Masiakasaurus</i> among theropods 13. Furthermore, the anterior teeth are much larger than the posterior ones, as in basal oviraptorosaurs 12, basal therizinosaurs 14 and probably <i>Epidendrosaurus</i> 4,5. There are probably 9 cervicals and 14 thoracic vertebrae, and the synsacrum is composed of 7 vertebrae. The caudal series is much shorter than in non-avian theropods or in other basal avialans. The anterior six caudal vertebrae are proportionally short and wide. The posterior ten caudals bear no transverse processes. They form a structure similar to the elongated, incipient pygostyle in some basal birds 15,16 but are not fused to each other (Figs 1a and 2a; see Supplementary Information). The partly preserved sternum is small and convex anteriorly, and seems to comprise two incompletely fused sternal plates, as in the primitive bird <i>Jeholornis</i> 17. The scapula is significantly shorter than the humerus, as in some derived maniraptorans, and the coracoid is sub-rectangular. The pelvis has an unexpected combination of features among theropods, as in <i>Epidendrosaurus</i> 4,5. The ilium is bird-like in having a long preacetabular process with a strongly convex anterior margin, but differs from the ilia of most non-avian theropods in having a small pubic peduncle. Unusually among theropods, the straight pubis is shorter than the ischium and is significantly shorter than the femur. It is anteroventrally oriented and lacks a pubic boot. The posteriorly curved ischium is laterally compressed, gradually widens towards the distal end, and lacks an obturator process. The humerus is about same length as the femur, proportionally longer than in most other basal avialans. The ulna is posteriorly bowed and the manus is significantly elongated (see Supplementary Information) as in birds and other derived theropods 18 – 22. The curvature of the manual claws falls within the range known for the pedal claws of ground-based foraging birds (see Supplementary Information). The femur is about 160% the length of the metatarsus, and 80% the length of the tibia (Figs 1a and 2a; see Supplementary Information). <b>Phylogeny and affinity.</b> Phylogenetic analysis indicates that <i>Epidexipteryx</i> and <i>Epidendrosaurus</i> form a monophyletic Scansoriopterygidae (see Supplementary Information), representing a bizarre lineage at the base of the Avialae 6 (Fig. 3; see Supplementary Information). Although possessing many derived features seen in birds, including a humerus as long as the femur, a long preacetabular process of the ilium with a strongly convex margin, and many other features, <i>Epidexipteryx</i> and <i>Epidendrosaurus</i> also show some striking similarities to oviraptorosaurs 12 and to a lesser degree therizinosauroids 14,21, including a short and high skull, an external naris positioned high on the snout, an anteriorly downturned and strongly dorsally convex mandible, a large external mandibular fenestra, and enlarged anterior teeth. Furthermore, some pelvic features, such as a proportionally very short pubis and a distally widening ischium, are not known in any other theropod. The bizarre appearance of scansoriopterygids indicates that morphological disparity among maniraptorans close to the origin of birds is higher than has previously been assumed, and underscores the importance of Jurassic theropods for understanding avian origins. <b>Integument.</b> The integument bears feather-like structures of two types, ETFs and non-ETFs, which are roughly comparable to shafted and non-shafted feathers, respectively 23. The distal part of each non- ETF is composed of filamentous parallel barbs (Fig. 2e, e 9, f), similar to the condition seen in the non-shafted feathers of other feathered dinosaurs and primitive birds 18,22–25. However, the free distal barbs of <i>Epidexipteryx</i> arise from the edge of a membranous structure (Fig. 2b, c, d, d 9), an arrangement that has never previously been reported. The four ETFs are tightly attached to the last ten caudal segments (Figs 1a and 2a). These feathers are incomplete distally, but the preserved part of each ETF is identical to the corresponding structure in some primitive birds 16,26–28, for example in having a similar central rachis and unbranched vanes (Fig. 1a, d and 2a, a 9; see Supplementary Information). Elongate tail feathers are a normal component of the ornamental plumage in extant birds. In contrast to other feather types, ornamental plumage is used to send visual signals that are essential to a wide range of avian behaviour patterns, particularly relating to courtship 29. For example, experiments have shown that, in some species, males with long tail plumage attract more mates than their short-tailed counterparts 30. It is highly probable that the ETFs of <i>Epidexipteryx</i> similarly had display as their primary function, rather than serving other purposes such as flight or insulation 29. Indeed, pennaceous feathers suitable for flight are not present in <i>Epidexipteryx</i>, even though the bones and integument are well preserved. Because pennaceous feathers are commonly encountered in other feathered maniraptorans 2,21,22,25, their absence constitutes another highly unusual feature of <i>Epidexipteryx</i>, as well as strongly implying that this taxon was non-volant. <i>Epidexipteryx</i> is the oldest and most phylogenetically basal theropod known to possess display feathers, indicating that basal avialans experimented with integumentary ornament as early as the Middle to Late Jurassic. Unless <i>Epidexipteryx</i> is interpreted as secondarily flightless, the absence of pennaceous limb feathers in this taxon suggests that display feathers appeared before airfoil feathers and flight ability in basal avialan evolution.
description: Published as part of <i>Zhang, Fucheng, Zhou, Zhonghe, Xu, Xing, Wang, Xiaolin &amp; Sullivan, Corwin, 2008, A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers, pp. 1105-1108 in Nature 455</i> on pages 1105-1107, DOI: 10.1038/nature07447, http://zenodo.org/record/2688152
description: {"references": ["7. Gao \u0321 K. - Q. &amp; Ren \u0321 D. Radiometric dating of ignimbrite from Inner Mongolia provides no indication of a post-Middle Jurassic age for the Daohugou Beds. Acta Geol. Sin. 80. 42 - 45 (2006).", "8. Chen \u0321 W. et al. Isotope geochronology of the fossil-bearing beds in the Daohugou area \u0321 Ningcheng \u0321 Inner Mongolia. Geol. Bull. Chin. 23. 1165 - 1169 (2004).", "10. Liu \u0321 Y. - X. \u0321 Liu \u0321 Y. - Q. &amp; Zhang \u0321 H. LA-ICPMS zircon U-Pb dating in the Jurassic Daohugou Beds and correlative strata in Ningcheng of Inner Mongolia. Acta Geol. Sin. 80. 733 - 742 (2006).", "12. Xu \u0321 X. et al. An unusual oviraptorosaurian dinosaur from China. Nature 419. 291 - 293 (2002).", "13. Sampson \u0321 S. D. \u0321 Carrano \u0321 M. T. &amp; Forster \u0321 C. A. A bizarre predatory dinosaur from Madagascar: implications for the evolution of Gondwanan theropods. Nature 409. 504 - 505 (2001).", "14. Kirkland \u0321 J. I. et al. A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah. Nature 435. 84 - 87 (2005).", "17. Zhou \u0321 Z. &amp; Zhang \u0321 F. A long-tailed \u0321 seed-eating bird from the Early Cretaceous of China. Nature 418. 405 - 409 (2002).", "18. Zhang \u0321 F. - C. \u0321 Zhou \u0321 Z. - H. &amp; Hou \u0321 L. - H. in The Jehol Biota (eds Chang \u0321 M. - M. \u0321 Chen \u0321 P. - J. \u0321 Wang \u0321 Y. - Q. &amp; Wang \u0321 Y.) 129 - 149 (Shanghai Sci. Technol. Publ. \u0321 2003).", "22. Xu \u0321 X. in Originationsi Radiations and Biodiversity Changes (eds Rong \u0321 J. - Y. et al.) 627 - 642; 927 - 930 (Sci. Press \u0321 Beijing \u0321 2006).", "6. Padian \u0321 K. in The Dinosauria 2 nd edn (eds Weishampel \u0321 D. B. \u0321 Dodson \u0321 P. \u0321 Osmolska \u0321 H.) 210 - 231 (Univ. of California Press \u0321 Berkeley \u0321 2004).", "23. Zhang \u0321 F. - C. &amp; Zhou \u0321 Z. - H. in Originationsi Radiations and Biodiversity Changes (eds Rong \u0321 J. - Y. e t al.) 611 - 625; 923 - 925 (Sci. Press \u0321 Beijing \u0321 2006).", "29. Gill \u0321 F. B. Ornithology 2 nd edn (Freeman \u0321 1995)."]}