The Yanliao Biota of northeastern China outcrops across much of western Liaoning, northern Hebei, and southeastern Inner Mongolia provinces, providing a series of deposits with exceptional preservation laid down over a period of about 10 million years in terrestrial settings. These deposits include the Daohugou phase (about 168–164 million years ago) and the Oxfordian Linglongta phase (164–159 million years ago). These fossils provide a valuable insight into a variety of emerging taxa in across the boundary between the Middle and Late Jurassic, including Insects, Mammals and Paravian Dinosaurs, the group which includes Dromaeosaurs, Troodontids and Birds.
In a paper published in the journal Nature Communications on 15 January 2018, Dongyu Hu of the Paleontological Museum of Liaoning at Shenyang Normal University, Julia Clarke of the Department of Geological Sciences and Integrated Bioscience at the University of Texas at Austin, Chad Eliason, also of the Department of Geological Sciences and Integrated Bioscience at the University of Texas at Austin, and of the Integrative Research Center at the Field Museum of Natural History, Rui Qiu, also of the Paleontological Museum of Liaoning at Shenyang Normal University, Quanguo Li of the State Key Laboratory of Biogeology and Environmental Geology at the China University of Geosciences, Matthew Shawkey of the Evolution and Optics of Nanostructures Group at the University of Ghent, Cuilin Zhao, again of the Paleontological Museum of Liaoning at Shenyang Normal University, Liliana D’Alba also of the Evolution and Optics of Nanostructures Group at the University of Ghent, Jinkai Jiang, once again of the Paleontological Museum of Liaoning at Shenyang Normal University, and Xing Xu of the Key Laboratory of Vertebrate Evolution and Human Origins at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, describe a new species of Paravian Dinosaur from the Late Jurassic Tiaojishan Formation of northern Hebei.
The new species is named Caihong juji, where 'Caihong' means 'rainbow' and 'juji' means 'big crest'. It is described from a single, almost complete skeleton and associated plumage preserved as part and counterpart on a split slab. The specimen is estimated to have been about 400 mm in length, and to have weighed about 475 g when it was alive, and is thought to have been an adult. It had a pair of prominent crests on its lacrimal bones (the bone that joins the nose to the eye-socket in Humans, and the hind-part of the snout in Theropod Dinosaurs), something very unusual in Paravians. Caihong juji is assessed to have been a Deinonychosaur on the basis of its anatomy (i.e. the sub-group of Paravians that includes Dromaeosaurs ans Troodontids, but not Birds.
Caihong juji. Photographs of the slab (a) and counter slab (b) and line drawing (c) of the specimen based on both slabs. Photograph (d) and line drawing (e) of a composite of the rostrum of the skull and mandible exposed on the counter slab and the post-rostrum cranium exposed on the slab. Arrows indicate lacrimal crests. Question mark indicates uncertain identification. Scale bars: 10 cm in (a)–(c), 1 cm in (d) and (e). Abreviations aof, antorbital fenestra; cav, caudal vertebra; cev, cervical vertebra; dr, dorsal rib; dv, dorsal vertebra; ect, ectopterygoid; emf, external mandibular fenestra; en, external naris; f, feather; fu, furcula; ga, gastralia; hy, hyoid; il, ilium; is, ischium; la, left angular; lar, left articular; lc, left coracoid; lcr, lacrimal crest; ld, left dentary; lf, left frontal; lfe, left femur; lh, left humerus; lj, left jugal; ll, left lacrimal; lma, left maxilla; lm, left manus; ln, left nasal; lp, left pes; lpa, left palatine; lpo, left postorbital; lq, left quadrate; lqj, left quadratojugal; lr, left radius; ls, left scapula; lsp, left splenial; lsa, left surangular; lsq, left squamosal; lt, left tibiotarsus; lu, left ulna; ma, mandible; mf, maxillary fenestra; o, orbit; p, parietal; pm, premaxilla; pt, pterygoid; pu, pubis; rar, right articular; rc, right coracoid; rd, right dentary; rfe, right femur; rh, right humerus; rm, right manus; rp, right pes; rpra, right prearticular; rq, right quadrate; rr, right radius; rs, right scapula; rt, right tibiotarsus; ru, right ulna; scl, sclerotic bones; sk, skull; sy, synsacrum. Hu et al. (2018).
Much of the plumage of Caihong juji is exceptionally well preserved, retaining the microstructure of the melanosomes (pigment cells). Comparison of these cells to those of modern Birds leads Hu et al. to conclude that this Jurassic Dinosaur had brightly coloured iridescent plumage.
Platelet-like nanostructures in Caihong juji and melanosomes in iridescent extant feathers. (a)–(d) Fossilized nanostructures from Caihong feathers preserved as molds in a neck feather (a) and three-dimensional preservation in a neck feather, with SEM stage rotated 45° to show 3D platelet morphology; (b) a back feather with SEM stage at 0° (c) and a neck feather showing nanostructure packing; (d), (e) Anna’s Hummingbird, Calypte anna, showing overlapping melanosomes within a feather barbule; (f) White-tailed Starfrontlet, Coeligena phalerata, showing stacking and interior morphology (air bubbles) of melanosomes in a feather barbule; (g) Black-tailed Trainbearer, Lesbia victoriae, showing exterior surface and morphology of isolated melanosomes in a feather barb; (h) Moustached Treeswift, Hemiprocne mystacea, showing densely packed melanosomes in the barbule of a crown feather. Inset in (d) illustrates 3D stacking of platelet-shaped nanostructures. All scale bars are 1000 nm. Hu et al. (2018).
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