The authors have declared that no competing interests exist.
Conceived and designed the experiments: RFW HLY. Analyzed the data: RFW HLY SCX SZW JY LJX YXL LJ. Wrote the paper: HLY. Performed the field work: SCX SZW JY LJX YXL LJ.
The origin of hadrosaurid dinosaurs is far from clear, mainly due to the paucity of their early Late Cretaceous close relatives. Compared to numerous Early Cretaceous basal hadrosauroids, which are mainly from Eastern Asia, only six early Late Cretaceous (pre-Campanian) basal hadrosauroids have been found: three from Asia and three from North America.
Here we describe a new hadrosauroid dinosaur,
The discovery of
Hadrosauroids were facultative bipedal dinosaurs that dominated Cretaceous Laurasian megaherbivorous niches
Definitions of relevant taxa follow Sereno
In 1958, C. C. Young (Z.-J. Yang)
(A)-Shanxi Province in China. (B)-Zuoyun County in Shanxi Province.
More than half a century later, the Department of Land and Resources of Shanxi Province initiated a project to find dinosaurs for the Shanxi Museum of Geology (SXMG) now being constructed. In 2011 and 2012, a number of dinosaur localities were discovered and excavated in Zuoyun County. Preliminary observations indicate the existence of hadrosauroid, ankylosaur, and ceratopsian remains from the early Late Cretaceous Zhumapu Formation, and stegosaur and sauropod remains from the late Early Cretaceous Zuoyun Formation. In this paper, a partial associated hadrosauroid skeleton from 2011 Locality 7 (SXMG V 00001, field number ZY007) is described and diagnosed as a new genus and species.
No permits were required for this study, which complied with all relevant regulations. We obtained permission from the Shanxi Museum of Geological and Mineral Science and Technology to access the collections. The specimens were discovered and excavated by the crew (including co-authors of this study) of the Shanxi Museum of Geological and Mineral Science and Technology.
The electronic edition of this article conforms to the requirements of the amended International Code of Zoological Nomenclature, and hence the new names contained herein are available under that Code from the electronic edition of this article. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix “
Numerous cladistic analyses have been conducted in order to elucidate the phylogenetic relationships among hadrosauroids in recent years; for example, at least four papers were published in 2012
In order to assess the phylogenetic position of the new taxon, we performed a cladistic analysis based on Sues and Averianov
Dinosauria Owen, 1842
Ornithischia Seeley, 1887
Ornithopoda Marsh, 1881
Iguanodontia Dollo, 1888
Ankylopollexia Sereno, 1986
Styracosterna Sereno, 1986
Hadrosauriformes Sereno, 1997
Hadrosauroidea Cope, 1870
urn:lsid:zoobank.org:act:C0BC17BE-AFA2-46E9-9712-3F7767C31C56
urn:lsid:zoobank.org:act:A906797B-9B90-4C19-AC96-AD8726A7EDD9
SXMG V 00001 (Shanxi Museum of Geology, Taiyuan, Shanxi Province, China). Associated but disarticulated partial skeleton of one individual, including the caudodorsal part of the skull (ZY007-37 and -38, separated along the floor of the braincase), two cervical vertebrae (-40 and -41), partial dorsal neural arch and neural processes (-36), two caudals (-27, proximal; -19, middle), distal portions of both ischia (-11, left; -12, right), distal end of left femur (-32), proximal portion of right tibia (-1), and distal portion of left tibia with astragalus (-2). See
Bone | Dimension | Measurement |
Caudodorsal part of the skull (ZY007-37, -38) | Width between the pendent paroccipital processes | 370 |
Height from the apex of the supraoccipital to the ventral edge of the occipital condyle | 175 | |
Length of preserved parietal | 140 | |
Midline length from the caudal end of the parietal to the caudal end of the paroccipital processes | 120 | |
Cervical (ZY007-40) | Length of centrum including cranial articular process | 135 |
Length of centrum | 90 | |
Width of cranial articular surface | 105 | |
Width of caudal articular surface | 140 | |
Height of centrum on the cranial articular surface | 88 | |
Height of total vertebra | 195 | |
Diameter of neural canal | 36 | |
Proximal caudal (ZY007-27) | Length of centrum | 89 |
Width of cranial articular surface | 160 | |
Width of caudal articular surface | 156 | |
Height of centrum on the cranial articular surface | 175 | |
Height of total vertebra | 540 | |
Diameter of neural canal | 23 | |
Middle caudal (ZY007-19) | Length of centrum | 95 |
Width of cranial articular surface | 107 | |
Width of caudal articular surface | 110 | |
Height of centrum on the cranial articular surface | 123 | |
Height of total vertebra | 330 | |
Diameter of neural canal | 23 | |
Distal portion of left ischium (ZY007-11) | Length | 295 |
Cross section at proximal end (length/width/perimeter) | 49/44/160 | |
Expanded distal end (length/width/perimeter) | 100/70/290 | |
Distal portion of right ischium (ZY007-12) | Length | 270 |
Cross section at proximal end (length/width/perimeter) | 50/48/170 | |
Expanded distal end (length/width/perimeter) | 97/69/290 | |
Distal end of left femur (ZY007-32) | Preserved length | 320 |
Cross section of preserved proximal end (length/width/perimeter) | 103/66/490 | |
Craniocaudal length of medial condyle | 270 | |
Craniocaudal length of lateral condyle | 240 | |
Proximal portion of right tibia (ZY007-1) | Preserved length | 565 |
Cross section of preserved distal end (length/width/perimeter) | 110/100/350 | |
Distal portion of left tibia (ZY007-2) | Preserved length | 385 |
Cross section of preserved distal end (length/width/perimeter) | 120/97/360 |
The generic name “Yungang” is after “Yungang Grottoes”, a UNESCO World Heritage built in the 5th and 6th centuries about 50 km east of the fossil locality; “long” means “dragon” in Chinese. The specific name reflects “Datong”, the city in which the locality is situated.
In the vicinity of Zuoyun County, Datong City, Shanxi Province, P. R. China. Lower part of Zhumapu Formation, lower Upper Cretaceous
In the Zuoyun area, the Zhumapu Formation reaches 722 m in thickness. It overlies the Lower Cretaceous Zuoyun Formation with a parallel unconformity relationship and is covered by Tertiary basalts. The age of the Zhumapu Formation is determined by biostratigraphic correlations, including evidences from angiosperm plants, spores and pollens, ostracodes, and bivalves
Basal hadrosauroid with the following unique combination of four character states: 1) caudal surface of the supraoccipital inclined steeply forward at approximately 450 (present in
The caudodorsal part of the skull is preserved, including the parietal, paroccipital processes, and the almost complete braincase (
(A)-Right lateral view. (B)-Dorsal view. (C)-Caudal view. Scale bar = 10 cm.
(A)-Right lateral view. (B)-Dorsal view. (C)-Caudal view. Scale bar = 10 cm. bo = basioccipital, bs = basisphenoid, eo = exoccipital, ls = laterosphenoid, oo = opisthotic, pa = parietal, po = prootic, pop = paroccipital process, ps = parasphenoid, so = supraoccipital, sq = squamosal.
In dorsal view, the preserved parietal length is 14.0 cm, and the narrowest transverse width at the mid-length of the parietals is 6.0 cm. There is a low sagittal crest along the midline of the preserved parietal portion, but whether or not it continued caudally to form a tall nuchal crest as in
The caudal surface of the supraoccipital is steeply inclined rostrally; the bone is nearly horizontal. In occipital view, the dorsal portion of the supraoccipital consists of a median knob-like dorsal process and two dorsolateral projections. Ventrally, the supraoccipital is separated from the exoccipitals by a slit-like transverse groove on the latter, which continues laterally underneath the opisthotics. The ventral edge of this groove forms a strong horizontal ridge, which borders the foramen magnum dorsally. The lateral sides of the foramen magnum are enclosed by the exoccipitals, which bear a knob-like ventral corner on each side. The exoccipitals also meet along the floor of the foramen magnum.
The paroccipital processes strongly bend caudolaterally, enclosing an arc of around 100 degrees in dorsal view and thereby, increasing the length of skull. The longitudinal distance from the caudal end of the parietal to an imaginary point on the midline between the caudal ends of the paroccipital processes is 12.0 cm, almost the same length as the parietal. In lateral view, the straight and vertical pendent portions of the paroccipital processes are set caudal to the occipital condyle, with their ventral tips slightly below the ventral edge of the occipital condyle.
The occipital condyle is formed by the basioccipital and describes a crescent in caudal view. Its caudal surface is vertical and slightly bulging, while its ventral surface is strongly convex. The surface is generally smooth, and one groove is visible on the left half of the caudal surface (
The braincase is broken along a line through the exits of the cranial nerves. The positions of these cranial nerve exits are conventional compared to other hadrosauroids, and generally correspond to those in closely related taxa, such as
Two cervicals (ZY007-40, -41) are preserved, and ZY007-40 is almost complete (
(A)-Cranial view. (B)-Right lateral view. (C)-Dorsal view. (D)-Caudal view. (E)-Left lateral view. (F)-Ventral view. Abbreviations: dia, diapophysis; par, parapophysis; poz, postzygapophysis; prz, prezygapophysis. Scale bar = 6 cm.
A partial dorsal neural arch and neural spine are preserved (ZY007-36) (
(A, B)-Partial dorsal neural arch and neural spine in (A) dorsal and (B) caudal views. (C, E)-Proximal caudal in (C) left lateral and (E) caudal views. (D, F)-Middle caudal in (D) left lateral and (F) caudal views. Abbreviations: chf, chevron facet; dia, diapophysis; ns, neural spine; poz, postzygapophysis; prz, prezygapophysis; transverse process, trp. Scale bar = 6 cm.
One proximal (ZY007-27) (
The distal portions of both ischia are preserved (ZY007-11 left, -12 right) (
(A, C)-Distal portion of left ischium in (A) medial and (C) cranial views. (B, D)-Distal portion of right ischium in (C) medial and slightly caudal and (D) distal and slightly dorsal views. Abbreviation: cede, cranially expanded distal end. Scale bar = 10 cm.
The distal end of the left femur is preserved (ZY007-32). The cross section of the preserved proximal end of the shaft is elliptical, and its transverse width is twice its craniocaudal width. The intercondylar extensor groove of the femur is deep, U-shaped, partially enclosed by expansion of medial and lateral condyles. The medial condyle is slightly larger than the lateral. The medial surface of the medial condyle is flat, while the lateral surface of the lateral condyle bears a stout longitudinal ridge. The caudal condyles are strongly developed, fan-shaped, and longer proximodistally than craniocaudally in lateral and medial views. In caudal view, the medial condyle is more expanded than the lateral, about three times wider transversely. On the lateral surface of the medial condyle, a small longitudinal ridge develops close to the shaft (
(A)-Cranial view. (B)- Caudal view. (C)-Proximal view. (D)-Distal view (E)-Lateral view. (F)-Medial view. Abbreviations: ieg, intercondylar extensor groove; ifg, intercondylar flexor groove; lc, lateral condyle; mc, medial condyle. Scale bar = 10 cm.
The proximal portion of the right tibia (ZY007-1) (
(A–F)-Proximal portion of right tibia in (A) media, (B) cranial, (C) lateral, (D) caudal, (E) proximal, and (F) distal views. (G–K)-Distal portion of left tibia with astragalus in (G) cranial, (H) caudal, (I) medial, (J) lateral, and (K) distal views. Abbreviations: as, astragalus; cc, cnemial crest; cf, concavity for articulation of distal end of fibula; cmc, caudomedial condyle; lc, lateral condyle; lm, lateral malleolus; mm, medial malleolus. Scale bar = 10 cm.
Phylogenetic analysis recovered 303 MPTs (most parsimonious trees) of 294 steps, with a CI (consistency index) of 0.534 and a RI (retention index) of 0.858. The strict consensus tree recovered
Bremer supports no less than 1 and bootstrap frequencies more than 50 are indicated above and below relevant branches, respectively. “•” represents node-based definition, and “→” represents branch-based definition.
In the strict consensus tree, the Hadrosauroidea clade is supported by 7 unambiguous synapomorphies (40[1], parietal sagittal crest long, more than 2/3 length of parietal; 46[1], antorbital fenestra external opening absent; 57[1], lacrimal-nasal contact absent; 74[1], length of basipterygoid processes extending well below level of ventral border of occipital condyle; 75[1], occipital condyle articular surface vertical; 103[1], cervical zygapophyseal peduncles on arches elevated, extending well above level of neural canal, zygapophyses long and dorsally arched; 114[1], humeral distal condyles compressed mediolaterally, flaring little from shaft of humerus), the (
The 50% majority rule tree further resolved (
The strict consensus tree recovered by our analysis is more resolved than those consensus trees of
In
The available information does not allow direct anatomical comparisons between
Young
(TNT)
(EMF)
(EMF)
We are grateful to Mr. Zhi-Lu Tang for arranging this study; to the crew of the Shanxi Museum of Geological and Mineral Science and Technology for discovering, excavating, and preparing the specimen; to Mr. Jing-Tao Yang for processing the photos; to Mrs. Jin-Ling Huang for drawing