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Postcranial Anatomy of Jeholosaurus shangyuanensis (Dinosauria, Ornithischia) from the Lower Cretaceous Yixian Formation of China

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Jeholosaurus shangyuanensis is a small ornithischian dinosaur from the Lower Cretaceous Yixian Formation of the Lujiatun locality, Liaoning Province, China. Here, we provide the first detailed description of its postcranial skeleton based on the holotype and four other well-preserved skeletons, and compare it with material of other primitive cerapodans. Jeholosaurus can be diagnosed on the basis of one postcranial autapomorphy, relating to the absence of parapophyses from the anterior dorsal vertebrae, and a unique combination of postcranial characters, but its anatomy is otherwise similar to that of many other basal ornithischians. A phylogenetic analysis incorporating these new postcranial data confirms previous suggestions that Jeholosaurus is a basal ornithopod and that it forms a clade with Changchunsaurus and Haya; Koreanosaurus and Yueosaurus might also belong to this clade, though additional material of both will be required to test this hypothesis. The name Jeholosauridae is proposed for this apparently endemic group of Cretaceous East Asian taxa.
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Postcranial anatomy of
Jeholosaurus shangyuanensis
(Dinosauria, Ornithischia) from the Lower Cretaceous Yixian
Formation of China
Journal:
Journal of Vertebrate Paleontology
Manuscript ID:
JVP-2011-0221.R1
Manuscript Type:
Article
Date Submitted by the Author:
02-Apr-2012
Complete List of Authors:
Han, Fenglu; Institute of Vertebrate Paleontology and
Paleoanthropology,Chinese Academy of Sciences,
Barrett, Paul; The Natural History Museum, Palaeontology
Butler, Richard; GeoBio-Center, Ludwig Maximilian University,
Xu, Xing; Institute of Vertebrate Paleontology and Paleoanthropology,
Chinese Academy of Sciences,
Key Words:
Ornithischia, China, Cretaceous , Yixian Formation, Ornithopoda
Society of Vertebrate Paleontology
Journal of Vertebrate Paleontology: For Review Only
Postcranial anatomy of Jeholosaurus shangyuanensis (Dinosauria, Ornithischia) from the Lower
Cretaceous Yixian Formation of China
FENG-LU HAN,
*,1,2
PAUL M. BARRETT,
3
RICHARD J. BUTLER,
4
and XING XU
1
1
Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate
Paleontology and Paleoanthropology and
2
Graduate University of the Chinese Academy
of Sciences, Chinese Academy of Sciences, 142 Xizhimenwai Street, Beijing 100044,
People’s Republic of China; hfl0501@gmail.com, xingxu@vip.sina.com;
3
Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7
5BD, United Kingdom; p.barrett@nhm.ac.uk;
4
GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Straße 10,
D-80333 Munich, Germany; r.butler@lrz.uni-muenchen.de
*Corresponding author.
RH: HAN ET AL.—POSTCRANIAL ANATOMY OF JEHOLOSAURUS
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ABSTRACT—Jeholosaurus shangyuanensis is a small ornithischian dinosaur from the
Lower Cretaceous Yixian Formation of the Lujiatun Locality, Liaoning Province, China.
Here, we provide the first detailed description of its postcranial skeleton based on the
holotype and four other well-preserved skeletons, and compare it to material of other
primitive cerapodans. Jeholosaurus can be diagnosed on the basis of one postcranial
autapomorphy, relating to the absence of parapophyses from the anterior dorsal vertebrae,
and a unique combination of postcranial characters, but its anatomy is otherwise similar
to that of many other basal ornithischians. A phylogenetic analysis incorporating these
new postcranial data confirms previous suggestions that Jeholosaurus is a basal
ornithopod and that it forms a clade with Changchunsaurus and Haya: Koreanosaurus
and Yueosaurus might also belong to this clade, though additional material of both will be
required to test this hypothesis. The name Jeholosauridae is proposed for this apparently
endemic group of Cretaceous East Asian taxa.
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INTRODUCTION
Phylogenetic relationships among basal ornithopod dinosaurs are poorly understood
and the published tree topologies for these taxa, and other basal cerapodans, have only
weak statistical support (e.g., Xu et al., 2006; Butler et al., 2007, 2008). This problem
stems from a number of causes, including the fragmentary remains of many of the
specimens and the difficulties in finding characters with strong enough phylogenetic
signals to tease apart the early evolutionary history of the clade. The first step needed to
improve this situation is the provision of more detailed information on the anatomy of
basal ornithopods, in order to highlight potential characters that might be of phylogenetic
significance.
Jeholosaurus shangyuanensis is a small ornithischian dinosaur from the Lower
Cretaceous Yixian Formation of Lujiatun, Liaoning Province, China (Xu et al., 2000). Xu et
al. (2000) provided a preliminary description of two specimens, the holotype (IVPP V12529,
a skull and associated partial postcranial specimen) and one referred specimen (IVPP
V12530, a skull with associated cervical vertebrae), and assigned this taxon to a basal
position within Ornithopoda. Subsequently, a detailed description of the cranial anatomy
was produced on the basis of these specimens and four other nearly complete skulls (Barrett
and Han, 2009). Interestingly, Jeholosaurus was shown to possess a combination of features
present in both ornithopods and marginocephalians, making attribution to either one of these
clades difficult (Barrett and Han, 2009). Nevertheless, all previous phylogenetic analyses
that include Jeholosaurus have generally recovered it as a basal ornithopod (Xu et al., 2000;
Butler et al., 2008; Barrett and Han, 2009), often in a clade with Changchunsaurus from the
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Quantou Formation (Aptian–Cenomanian) of Jilin Province (Butler et al., 2011) and Haya
griva from the Javkhlant Formation (?Santonian) of Mongolia (Makovicky et al., 2011). By
contrast, an alternative proposal is that Jeholosaurus and Changchunsaurus might be basal
marginocephalians, on the basis of an as yet unpublished phylogenetic analysis that
incorporated information from seven individuals of Jeholosaurus, including five nearly
complete skeletons (Han, 2009). Here, we provide the first detailed postcranial description
of Jeholosaurus shangyuanensis, based on the holotype specimen, the original referred
specimen, and three other nearly complete postcranial specimens, and assess the impact of
this new information on the systematics of basal cerapodans.
Institutional AbbreviationsIVPP, Institute of Vertebrate Paleontology and
Paleoanthropology, Beijing; NHMUK, Natural History Museum, London; SAM, Iziko
South African Museum, Cape Town; ZDM, Zigong Dinosaur Museum, Zigong.
SYSTEMATIC PALEONTOLOGY
DINOSAURIA Owen, 1842
ORNITHISCHIA Seeley, 1887
CERAPODA Sereno, 1986 sensu Butler et al. (2008)
ORNITHOPODA Marsh, 1881 sensu Butler et al. (2008)
JEHOLOSAURIDAE, fam. nov.
Diagnosis—All ornithischians more closely related to Jeholosaurus shangyuanensis
Xu, Wang, and You, 2000 than to Hypsilophodon foxii Huxley, 1869, Iguanodon
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bernissartensis Boulenger in Beneden, 1881, Protoceratops andrewsi Granger and
Gregory, 1923, Pachycephalosaurus wyomingensis (Gilmore, 1931), or Thescelosaurus
neglectus Gilmore, 1913.
Type SpeciesJeholosaurus shangyuanensis Xu, Wang, and You 2000.
Taxonomic ContentJeholosaurus shangyuanensis Xu, Wang, and You, 2000,
Haya griva Makovicky, Kilbourne, Sadleir, and Norell, 2011 and Changchunsaurus
parvus Zan, Chen, Jin, and Li, 2005.
JEHOLOSAURUS Xu, Wang, and You 2000
Type SpeciesJeholosaurus shangyuanensis (by monotypy).
Diagnosis—As for the type species (see below).
Distribution—Early Cretaceous (?upper Barremian–lower Aptian), northeastern
China.
JEHOLOSAURUS SHANGYUANENSIS Xu, Wang, and You, 2000
(Figs. 1–13)
Emended Diagnosis—Cranial autapomorphy: presence of a row of small foramina
on the lateral surface of the nasal immediately dorsal to the premaxillary articulation.
Unique combination of cranial character states: six premaxillary teeth (distinct from all
other cerapodans, but present in Lesothosaurus, Scutellosaurus, and some ankylosaurs);
presence of a foramen enclosed within the quadratojugal (distinct from all ornithischians
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except Haya, Hypsilophodon, and Tenontosaurus); combined presence of nodular
ornamentation on the postorbital and jugal (distinct from all ornithopods and non-
cerapodan ornithischians, but also present in pachycephalosaurs, Archaeoceratops,
Xuanhuaceratops, and Yinlong); and jugal caudal process bifurcated distally (distinct
from all cerapodans except Psittacosaurus, but present in some early ornithischians
including Emausaurus, Lesothosaurus, and Scelidosaurus). Cranial characters are
discussed in detail in Barrett and Han (2009).
Postcranial autapomorphy: parapophyses absent from dorsal vertebrae 1 and 2.
Unique combination of postcranial character states: possession of three distal tarsals, with
fused distal tarsals 1 + 2 (distinct from all other ornithischians, with the exception of
Orodromeus) and phalanx 3-4 is the longest element in pedal digit 3 (also present in
Xiaosaurus).
Holotype—IVPP V12529, a partial skeleton consisting of a skull, seven cervical
vertebrae, several fragmentary dorsal vertebrae and partial sacrum, articulated sections of
caudal vertebrae, and both hind limbs.
Locality and Horizon—Lujiatun, Liaoning Province, People’s Republic of China;
‘Lujiatun Bed’, Yixian Formation, ?upper Barremian–lower Aptian, Early Cretaceous
(Wang et al., 1998; He et al., 2006). The locality is collection number 53493 within the
Paleobiology Database. It is not known if all of the specimens are from the same level
within the ‘Lujiatun Beds’ and this seems unlikely given the preservational differences
between them. However, they were all recovered from the complex of sites around
Lujiatun that pertain to the ‘Lujiatun Beds’.
Referred Specimens—IVPP V12530, a skull with articulated cervical vertebrae;
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IVPP V12542, a skull with a nearly complete vertebral column, partial forelimb and hind
limb, and a nearly complete pelvis; IVPP V15719, a nearly complete skull, partial axial
column, pelvic girdle, and hind limbs; IVPP V15939, partial post-cervical axial column,
partial pelvic girdle, and a complete hind limb and pes.
Material—Four of the five specimens described herein are associated with skulls
(IVPP V12529, V12530, V12542, and V15719), allowing them all to be referred to
Jeholosaurus on the basis of diagnostic cranial characters (Barrett and Han, 2009). The
fifth specimen (IVPP V15939), which is also the largest, consists only of postcranial
elements, but shares the diagnostic combination of postcranial characters present in the
other specimens.
IVPP V12529. Postcranial elements of the holotype specimen include: the anterior
cervical vertebrae (cervicals 1–7, which are well preserved); four strongly compressed
anterior dorsal vertebrae; three associated, but badly damaged sacral vertebrae; several
groups of well preserved, articulated caudal vertebrae (whose exact positions within the
tail cannot be determined with confidence); the almost complete left femur and the distal
part of the right femur; both tibiae and fibulae; the right astragalus (which is broken and
preserved in two sections: one in articulation with the right tibia, and the other in
articulation with the right pes), the ascending process of the left astragalus, and both
calcanea; and substantial portions of both feet, which are well preserved, but somewhat
compressed mediolaterally (see Xu et al., 2000).
IVPP V12530. The only postcranial elements preserved in this specimen are ten
articulated vertebrae, consisting of the axial neural arch (the axial centrum and axis are
not preserved), cervicals 3–9, and dorsals 1–2.
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IVPP V12542. A previously undescribed partial skeleton consisting of: a damaged,
but almost complete skull; an articulated vertebral column extending from the middle of
the dorsal series to the middle of the tail, including a complete sacrum and several
chevrons, but lacking dorsal and caudal ribs; a right humerus; pelvic girdle elements
(articulated ischium and pubis and displaced ilium); right and left femora and tibiae; a
right fibula; and a left pes. The specimen is still embedded in matrix and all of the
elements are visible from one side only.
IVPP V15719. This is the smallest specimen in the sample and remains partially
embedded within a white tuffaceous mudstone block. Consequently, many of the
elements are visible in one view only. The preserved parts of the skeleton are generally
articulated, though the right forelimb and the anterior–middle parts of the dorsal vertebral
column, and most of the tail, are missing. In addition to the skull, IVPP V15719 consists
of: a series of articulated cervical/dorsal vertebrae (from the axis to dorsal 1); a left
scapula, coracoid, and humerus; a section of vertebral column comprising five dorsal
vertebrae and three sacral vertebrae; five caudal vertebrae; an almost complete right ilium
and right ischium, the proximal end of the right pubis, and a damaged left ischium
(missing the central part of its shaft); left and right femora (left femur complete, right
femur represented by the distal end only), tibiae (both complete), and fibulae (distal part
only on the left side); the right astragalus and calcaneum; and partial left and right pedes.
An isolated metatarsal preserved in the block represents another larger animal and will
not be discussed further herein.
IVPP V15939. This specimen represents the largest known individual and is well
preserved. It includes: a set of four associated dorsal vertebrae, one isolated dorsal, an
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articulated vertebral column extending from the posterior-most dorsal through the sacrum
to caudal vertebra 9; both ilia and ischia, an almost complete right pubis and the left
pubic shaft, with most of the girdle elements in articulation with each other and the
sacrum; and complete left and right hind limbs.
None of the specimens includes a complete dorsal or caudal vertebral series, sterna,
ulnae, radii, or manual elements. Key measurements from all of these specimens are
provided in Appendix 1.
Comments—Xu et al. (2000) included three postcranial characters in their diagnosis
of Jeholosaurus, but none of these are autapomorphic. The first of these, absence of an
anterior intercondylar groove on the distal femur, is an ornithischian symplesiomorphy
(e.g., Butler et al., 2008). The second, the tubular arrangement of the metatarsals, is due
to preservational factors affecting the holotype specimen (IVPP V12529) and is not
present in any of the better-preserved referred specimens (e.g., IVPP V15939). Finally,
pedal phalanx 3-4 is the longest phalanx in pedal digit 3 not only in Jeholosaurus, but
also in Xiaosaurus, as noted by Xu et al. (2000). However, this does form part of a unique
character combination for Jeholosaurus (see Diagnosis, above). The proposed
autapomorphy and unique combination of characters proposed herein are visible in the
holotype specimen and can also be seen in some of the referred specimens, notably IVPP
V15939, which lacks an associated skull and whose referral to Jeholosaurus relies on
postcranial characters alone. Additional discussion of these features is provided below.
DESCRIPTION AND COMPARISONS
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Axial Skeleton
Cervical Series—The cervical vertebrae can be completely reconstructed on the
basis of IVPP V12529, V12530, and IVPP V15719 (Figs. 1, 2). Jeholosaurus possessed a
total of nine cervical vertebrae, as also occurs in Heterodontosaurus (SAM-PK-K1332;
Santa Luca, 1980), ?Scutellosaurus (Colbert, 1981), the basal neornithischians
Hexinlusaurus (ZDM T6001; He and Cai, 1984; Barrett et al., 2005) and Agilisaurus
(ZDM T6011; Peng, 1992), non-iguanodontian ornithopods (e.g., Changchunsaurus
[Butler et al., 2011], Haya [Makovicky et al., 2011], Hypsilophodon [NHMUK R196;
Galton, 1974], and Orodromeus [Scheetz, 1999]), and most species of the basal
ceratopsian Psittacosaurus (Russell and Zhao, 1996; You and Dodson, 2004). Fewer
cervical vertebrae occur in the basal thyreophoran Scelidosaurus (six cervicals: NHMUK
R1111; Owen, 1863; Norman et al., 2004a), ankylosaurs (7–8 cervicals: Vickaryous et al.,
2004), and the early stegosaur Huayangosaurus (eight cervicals: Zhou, 1984), whereas
more than nine cervical vertebrae appear in iguanodontian ornithopods (Norman, 2004)
and most ceratopsians (Dodson et al., 2004; You and Dodson, 2004). Cervical vertebrae
1–7 are preserved in the holotype (Fig. 1A, C–F) and cervical vertebrae 2–9 are present
in IVPP V12530 (Fig. 1B) and IVPP V15719 (Fig. 2).
Atlas—The proatlas is not preserved in any of the available specimens and the only
information available for the atlas comes from the holotype (IVPP V12529), which
includes the atlantal intercentrum and right atlantal neural arch only (Fig. 1). The atlantal
intercentrum has rotated to the left relative to its life position (Fig. 1A, D). In anterior
view, the intercentrum has a crescentic outline (Fig. 1D). Its anterior surface slopes
posterodorsally and is concave for the reception of the occipital condyle. This fossa is
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deepest on the midline and becomes shallower laterally. A distinct, thin flange forms the
ventral margin of the fossa and separates the anterior surface of the intercentrum from its
ventral surface. In anterior view, the lateral margins of the intercentrum are
dorsoventrally expanded: the dorsal margins of these expansions form the articular
regions for the atlantal neural arches, while the ventral parts form ventrolaterally
extending bosses (diapophyses) that would have articulated with the atlantal ribs. These
bosses are present in Hypsilophodon (NHMUK R2477; Galton, 1974), but are only subtly
developed in Hexinlusaurus (ZDM T6001; He and Cai, 1984). In ventral view, the
intercentrum is anteroposteriorly narrow and the surface is excavated with a broad groove
that is delimited by the anterior and posterior margins of the intercentrum and the
diapophyses (Fig. 1A, C). A similar groove is present in Hexinlusaurus (He and Cai,
1984). In lateral view, the intercentrum is wedge-shaped, being broadest centrally and
tapering to a narrow dorsal apex. The posterior surface of the intercentrum is partially
obscured by the axis, but the visible portion shows that it was shallowly convex.
The right neural arch (Fig. 1D) has become disarticulated from the intercentrum and
forms an inverted ‘L’-shape in anterior and lateral views. The postzygapophysis is
missing and the prezygapophysis is damaged anteriorly. In lateral view, the base of the
neural arch is expanded to form the articulation with the intercentrum, but the arch
narrows as it extends dorsally, before expanding again to form the pre- and
postzygapophyses (Fig. 1A, C). Ventrally, the articular surface for the intercentrum is
anteroposteriorly and mediolaterally expanded and rugose. An angle of approximately
90° separates the long axis of the neural arch pedicle from the prezygapophysis.
Axis—The axis is well preserved and essentially complete in IVPP V12529 (Fig. 1A,
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C–F): the axial neural arch is present in IVPP V12530 (Fig. 1B), and IVPP V15719
includes the axial centrum. As a result the following description is based primarily on
IVPP V12529, supplemented with information from the other two specimens. The
various components of the axis in IVPP V12529 have not fused, and the junctions
between the centrum, intercentrum, and neural arch are clearly visible. It is not possible
to determine whether the odontoid is fused to the centrum or not as its contacts are
obscured.
In anterior view, the odontoid process is prominent, with a hemispherical outline and
strongly convex articular surface (Fig. 1D). The sub-rounded ventral surface is in
articulation with the intercentrum. In dorsal view, the dorsal surface of the odontoid
process is planar and has a convex anterior margin (Fig. 1E). The anterior and posterior
surfaces of the centrum are flat, and semicircular in outline. The lateral surfaces of the
centrum are excavated so that they are strongly concave anteroposteriorly and convex
dorsoventrally: the two surfaces converge ventrally to form a sharp keel that gives the
centrum a triangular transverse cross-section at midlength. By contrast, the axial centrum
of Haya lacks a distinct keel (Makovicky et al., 2011). Anteriorly, the centrum articulates
with a small, wedge-shaped intercentrum. There is no trace of any foramina on the lateral
surface of the axis. A prominent, dorsoventrally elongate parapophysis is present at the
junction of the anterior edge and lateral margins of the centrum at approximately
midheight (Fig. 1A, C).
The height of the neural arch is slightly greater than that of the centrum. Laterally, it
supports a slender, finger-like diapophysis that is positioned just dorsal to the
neurocentral suture. The presence of an atlantal diapophysis contrasts with the condition
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in Changchunsaurus in which the diapophysis is absent (Butler et al., 2011).
Prezygapophyses were present, but are not well preserved, and only the base of the left
prezygapophysis is visible in IVPP V12529 (Fig. 1C). The postzygapophyses are
positioned slightly more dorsally on the arch than the prezygapophyses and face
ventrolaterally: in IVPP V12529 they are in articulation with the prezygapophyses of
cervical 3. In lateral view, the neural spine is oriented posterodorsally at an angle of 45°
to the horizontal and in anterior view it is expanded transversely to form a vaulted plate
(Fig. 1A, C, E). The midline of the spine forms a sharp crest that extends along its entire
length. The neural spine is very elongate and extends beyond the posterior margin of the
axial centrum to overlap cervical vertebra 3 (Fig. 1A, C), as occurs in some early
ornithischians, including Lesothosaurus (Sereno, 1991) and Heterodontosaurus (Santa
Luca, 1980), non-iguanodontian ornithopods, such as Haya (Makovicky et al., 2011) and
Changchunsaurus (Butler et al., 2011), and some ceratopsians (Butler et al., 2011).
Breakage to the axial neural spine in IVPP V12530 results in a structure on the right-hand
side that resembles a strongly developed epipophysis, whose presence would be unusual
in an ornithischian: however, this feature is actually the result of damage to the spine and
a similar process is not present on the left-hand side.
An axial rib is preserved in IVPP V12529. It is short, but broken distally, and its
proximal end is in contact with the parapophysis. The dorsal part of the rib is damaged,
so it is not possible to confirm the presence or absence of a second rib head, but the
presence of a diapophysis suggests that the rib may have been at least incipiently double-
headed.
Cervical Vertebrae 3–9—The centra of cervicals 3–9 are amphiplatyan to slightly
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amphicoelous (Figs. 1, 2). They are pentagonal and shield-shaped in anterior or posterior
view, and have anteroposteriorly concave, saddle-shaped lateral surfaces that each bear a
small centrally positioned nutrient foramen. All of the cervicals possess thin, sharp keels
on the ventral midline (Fig. 1F): similar keels are present in basal ornithischians,
including Heterodontosaurus (Santa Luca, 1980), Stormbergia (Butler, 2005), Eocursor
(Butler, 2010), and Hexinlusaurus (He and Cai, 1984), and some basal ornithopods, such
as Changchunsaurus (Butler et al., 2011) and Orodromeus (Scheetz, 1999). These ventral
keels differ from those in some other ornithopods (e.g., Hypsilophodon, NHMUK R196;
Galton, 1974) and basal ceratopsians (e.g., Psittacosaurus: Averianov et al., 2006), which
have much broader keels.
In lateral view, all of the centra have an almost square outline, with subequal
dorsoventral heights and anteroposterior widths, and they are also similar in length to
each other along the entire cervical column (Fig. 1A–C). This combination of features
also occurs in Changchunsaurus (Butler et al., 2011), Orodromeus (Scheetz, 1999),
Psittacosaurus (Averianov et al., 2006), and Yueosaurus (Zheng et al., 2012), but differs
from the condition in Heterodontosaurus (SAM-PK-K1332; Santa Luca, 1980),
Hexinlusaurus (He and Cai, 1983), and Hypsilophodon (NHMUK R196; Galton, 1974),
and especially Koreanosaurus (Huh et al., 2010) in which the cervical centra are
significantly longer than tall. As in Changchunsaurus, Haya, and several other basal
cerapodans, the ventral margins of the anterior cervical centra are slightly convex in
lateral view, rather than concave or straight as in the majority of other ornithischians,
such as Heterodontosaurus, Hypsilophodon, Orodromeus, Psittacosaurus, and
Yueosaurus (Butler et al., 2011; Makovicky et al., 2011; Zheng et al., 2012).
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The parapophyses are stout rounded processes, with subovate outlines in lateral view.
In IVPP V12529, cervical 3 bears dorsolaterally extending parapophyses that are
positioned at the anterodorsal corner of the centrum, just ventral to the neurocentral
junction. Between cervical vertebrae 4–7 the parapophyses migrate dorsally to straddle
the neurocentral suture, with the articular surface of the parapophysis now facing
anteroventrally (Fig. 1A–C). In IVPP V12530 and IVPP V15719, the majority of the
parapophysis lies above the suture in cervical vertebra 9 (Fig. 1B). The dorsolateral
orientation of the parapophyses in Jeholosaurus differs from the ventrolateral orientation
present in Yueosaurus (Zheng et al., 2012). The sutures between the neural arch and
centrum are not straight, but ascend dorsally to reach its highest point at a point
approximately halfway along the centrum before descending ventrally to the posterior
margin of the vertebra.
The neural arches become progressively taller though cervicals 3–7, as in other
ornithischians. In IVPP V12529, the posteroventrally extending diapophyses of cervical 3
are much more robust and elongate than those of the axis. The diapophyses remain
similar in shape along the cervical series. They have cylindrical cross-sections and project
posteroventrally, forming an angle of approximately 45° with the horizontal in both
lateral and dorsal views. In IVPP V12530 and IVPP V15719, the position of the
diapophysis migrates dorsally in more posterior cervicals and the direction in which they
extend from the neural arch gradually changes from posteroventral to more posterolateral.
In dorsal view, the distal end of the diapophysis in cervical 3 is slightly expanded
anteroposteriorly relative to its shaft. However, this distal expansion is not present, or is
only very weakly developed, in the other cervical vertebrae. In IVPP V12530, the
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diapophyses become progressively longer posteriorly, so that cervical 8 has the longest
and most robust diapophysis in the neck, as preserved (Fig. 1B).
In all cervical vertebrae, the neural arches are inclined slightly anteriorly in lateral
view. The neural spine of cervical 3 is relatively prominent, as in Changchunsaurus and
Haya, in contrast to the small neural spines present on the cervical 3 of other small
ornithischians (Fig. 1A, C: Butler et al., 2011; Makovicky et al., 2011). The remaining
cervical neural spines are lower in height and are transversely compressed plates, whose
summit forms a sharp ridge dorsally. In posterior view, the neural canals are broad and
ovate in outline, narrowing dorsally. The prezygapophyses face dorsomedially and have
facets oriented at an angle of approximately 30° to the vertical, while the
postzygapophyses face ventrolaterally. As the cervicals in all specimens are preserved in
articulation, other features of the pre- and postzygapophyses are generally obscured.
Nevertheless, as in the majority of small ornithischians (e.g., Galton, 1974; Scheetz,
1999), the postzygapophyses appear to be relatively short, and do not overlap the
succeeding vertebra for a considerable distance, in contrast to the elongate
postzygapophyses present in Koreanosaurus (Huh et al., 2010).
In cervical 7 of IVPP V12529, a short lamina forms the medioventral border of a
posteriorly opening, shallow fossa that is bounded dorsomedially by the
postzygapophysis, dorsally by a low postzygodiapophyseal lamina, and laterally by an
incipient posterior centrodiapophyseal lamina. This fossa is also present in an incipient
form on cervical 6 of the same specimen.
Incomplete cervical ribs, consisting of the proximal part only, are present in IVPP
V12529 (Fig. 1A, C), while in IVPP V15719 only the seventh and eighth cervical ribs are
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preserved (Fig. 2A). The post-axial cervical ribs are double-headed. The anterior cervical
ribs are more slender than those on more posterior cervicals. They are ‘Y’-shaped in
lateral view, but the tuberculum is longer and more slender than the capitulum. The
capitulum and tuberculum form an angle of approximately 90º and the rib shaft tapers
distally.
Dorsal VertebraeDorsal vertebrae are partially preserved in most of the above-
mentioned specimens, but none of these preserve a complete dorsal series. It is likely that
the complete dorsal column contained around 15 vertebrae, based on comparisons with
other closely related taxa, such as Hypsilophodon (Galton, 1974). The first dorsal
vertebra and dorsal vertebrae 1 and 2 are present in IVPP V15719 and IVPP V12530,
respectively, preserved in articulation with the neck, and are similar to the cervicals (Fig.
1B and 2B). IVPP V15939 includes six dorsal vertebrae, four in articulated series and the
fifth and sixth articulated with the sacrum in a separate block (Figs. 3, 4). The last five
dorsals are also preserved in articulation with the sacrum in IVPP V15719. Ten dorsal
vertebrae are preserved in IVPP V12542, but their surfaces are badly damaged and
provide little information about their anatomy (Fig. 5A).
All of the preserved dorsal vertebrae are slightly amphicoelous. The anterior dorsals
are very similar to the posterior cervicals and differ from the posterior dorsals in several
respects. Dorsals 1 and 2 lack parapophyses (Fig. 1B), whereas these structures are well-
developed on the posterior dorsals (Fig. 3). By contrast, parapophyses are present on
dorsals 1 and 2 in other small ornithischians (e.g., Hexinlusaurus [He and Cai, 1984],
Hypsilophodon [Galton, 1974], and Orodromeus [Scheetz, 1999]; the condition cannot be
determined in Changchunsaurus or Haya due to preservation [Butler et al., 2011;
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Makovicky et al., 2011]) and their absence is provisionally regarded as an autapomorphy
of Jeholosaurus. In addition, the posterior articular surfaces of the anterior dorsal centra
have a subpentagonal outline, whereas those of the posterior dorsals are subcircular. This
difference is due to the presence of a sharp, midline ventral keel on the anterior dorsals
(IVPP V12530, IVPP V15719: Fig. 1B), which develops into a small process on the
ventral midline of the anterior articular surface and is absent from the posterior dorsals
(see below).
In anterior or posterior view, the posterior dorsal centra are approximately as wide as
they are high (Figs. 3, 4, and 6: IVPP V15719 and V15939). The lateral surfaces are
depressed relative to the articular regions and are gently concave longitudinally. Very
small nutrient foramina are present in the centre of this depression, and are variable in
number, size, and exact position (Fig. 3). The ventral surface is broad and divided from
the lateral surfaces by subtle breaks in slope, rather than well-defined ridges. Each ventral
surface bears a distinct, but low, midline keel, which is more strongly developed in the
posterior-most dorsals than in the middle dorsals (Fig. 3). Immediately adjacent to the
articular surfaces, the lateral and ventral margins of the centra are textured with numerous
fine grooves and pits, which are obvious on IVPP V15939 (Fig. 3), but hard to see in
IVPP V15719 and IVPP V12542. In IVPP V15939 and IVPP V15719, the neurocentral
sutures are open.
In all of the posterior dorsals, the neural canals are subelliptical in outline and are
broader than they are high (visible in IVPP V15939 only). The transverse processes have
a ‘stepped’ morphology in dorsal view with the diapophysis extending further laterally
than the parapophysis. The parapophysis and diapophysis are situated at almost the same
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height in lateral view. In anterior or posterior view, the transverse processes extend
almost horizontally, and a little posteriorly, and thicken dorsoventrally towards their
lateral ends. In the posterior-most dorsals, the parapophysis coalesces with the
diapophysis, so that in the first two preserved dorsals of IVPP V15939 (dorsals 10–11,
assuming a total dorsal count of 15) these processes are still distinct, but are joined to
form a compound articular surface with a horizontally oriented ‘figure-of-eight’-shaped
outline in lateral view (Fig. 3A). Posterior to this point (dorsals 12–15) the stepped
morphology of the transverse process disappears to replaced by a simpler morphology
with subparallel anterior and posterior margins. The parapophysis and diapophysis merge
in these vertebrae to form a single undivided articular surface.
In ventral view, the transverse processes bear a ridge that subdivides the ventral
surface into two depressions, which extend along the anteroventral and posteroventral
surfaces of the process respectively. Dorsally, the surface of transverse process is gently
convex anteroposteriorly.
The transverse processes lie at nearly at the same level as the zygapophyses. The
articular surfaces of the prezygapophyses face dorsomedially at an angle of 45° to the
horizontal, while those of the postzygapophyses mirror this, facing anterolaterally. The
articular surfaces of both the pre- and postzygapophyses are almost flat and have
subelliptical outlines. A short, deep, dorsoventrally oriented, and slit-like fossa separates
the postzygapophyses medially in posterior view. The neural spines are transversely
compressed subrectangular plates with subparallel anterior and posterior margins in
lateral view and straight dorsal margins. The dorsal margins of the spines are slightly
expanded mediolaterally relative to the spine bases, so that the top of spine forms a flat
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narrow platform.
With the exception of a few uninformative fragments, no dorsal ribs are preserved in
any of the available specimens.
Sacral Vertebrae—The sacrum consists of six sacral vertebrae (IVPP V15939, Fig.
4; IVPP V12542, Fig. 5). Three anterior sacrals are preserved in articulation with the
ilium and posterior dorsals in IVPP V15719 (Fig. 6). In all cases, with the exception of
the last two sacral vertebrae in IVPP V15939 (which are slightly disarticulated), the
sacral vertebrae are tightly connected, but are not co-ossified. IVPP V15939 is preserved
with all six sacrals in articulation with the right ilium, via five pairs of sacral ribs
(attaching to sacral vertebrae 2–6), and the first six caudal vertebrae. As the best-
preserved specimen, IVPP V15939 forms the basis for most of the following description.
All of the sutural contacts between the centra and sacral ribs, adjacent sacral ribs, and
between the sacral ribs and ilia are unfused in this specimen. However, the neural arches
are fused to the centra in sacrals 2–6, but the neurocentral suture is still visible in sacral 1.
Six sacral vertebrae occur in many basal ornithopods, including Haya (Makovicky et
al., 2011), Orodromeus (Scheetz, 1999), Parksosaurus, Thescelosaurus, Othnielosaurus
(Norman et al., 2004b), and some specimens of Hypsilophodon (NHMUK R193; Galton,
1974), as well as in the basal ceratopsian Psittacosaurus (You and Dodson, 2004) and
heterodontosaurids such as Heterodontosaurus and Fruitadens (Butler et al., in press).
Five sacral vertebrae are present in more primitive ornithischians, including
Lesothosaurus (Sereno, 1991), Agilisaurus (ZDM T6011; Peng, 1992), Hexinlusaurus
(ZDM T6001; He and Cai, 1984; Barrett et al., 2005), and probably Eocursor (Butler et
al., 2007). Sacra with more than six sacral vertebrae occur in derived ornithopods
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(Norman, 2004) and ceratopsians (Dodson et al., 2004).
In IVPP V15939, the anterior articular surface of sacral 1 is gently concave and
transversely expanded in anterior view, so that the centrum is wider than high and
subelliptical in outline. The posterior articular surface of sacral 1 is obscured by contact
with sacral 2, but is clearly wider than the anterior articular surface. The dorsolateral
portion of the centrum supports the anterior part of the second sacral rib. In lateral view,
the surfaces of the centrum are strongly concave longitudinally and do not possess any
nutrient foramina. Matrix obscures much of the ventral surface, which is separated from
the lateral surfaces by distinct changes in slope. Due to breakage, the diapophyses are
missing from sacral 1 in IVPP V15939. However, diapophyses are present in IVPP
V15719, in which they are short, anterolaterally directed, and similar in morphology to
those of the posterior dorsals. On this basis it seems likely that sacral rib 1 was free and
would not have been fused to the vertebra. In IVPP V15939, the prezygapophyses face
dorsally and the neural spine is transversely compressed and plate-like with a
subrectangular outline in lateral view. The posterior margin of the neural spine is closely
appressed to that of sacral 2. Details of the postzygapophyses are not visible in IVPP
V15939 due to the close apposition of sacral 2. In lateral view, small openings are present
between each of the sacral vertebrae, positioned ventral to the articulated post- and
prezygapophyses and dorsal to the centrum. A thin platform of bone extends along the
lateral surface of the neural arch, connecting the prezygapophysis to the diapophysis and
diapophysis to the postzygapophysis, in a position equivalent to the prezygodiapophyseal
and postzygopophyseal laminae of saurischian dinosaurs (Wilson, 1999). This platform is
transversely narrow in dorsal view and continuous between the first four sacrals. It is still
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present on sacral 5, though not prominent as in sacrals 1–4 and is strongly reduced on
sacral 6.
A large facet for the reception of the posterior part of the second sacral rib is present
on the anterolateral surface of the centrum in sacral 2. The rest of the lateral surface is
strongly concave anteroposteriorly and bears several small nutrient foramina. Low ridges
separate the lateral and ventral surfaces of the centrum. The third sacral rib contacts the
posterodorsal corner of the centrum, but there is no large facet for its reception. In ventral
view, the anterior articular surface of sacral 2 is transversely expanded and subequal in
width to the posterior articular surface of sacral 1, forming laterally projecting bosses for
the articulation of the sacral rib. Posterior to this point the centrum narrows transversely
and the width of the posterior articular surface is narrower than that of the anterior
surface. The ventral surface of the centrum bears a broad, shallow, anteroposteriorly-
extending groove that is bounded laterally by the ridges that divide the ventral and lateral
surfaces. Neural spine morphology is identical to that of sacral 1 and the spines of sacrals
1 and 2 are the same dorsoventral height in lateral view, though the spine of sacral 2 is
slightly longer than that of sacral 1. Unfortunately, the pre- and postzygapophyses are
largely obscured by their close apposition to each other. The diapophyses extend laterally
and ventrally as a thick bar that articulates with the sacral rib ventrally and they maintain
a constant anteroposterior width in dorsal view. The anterior and posterior surfaces of the
diapophyses are excavated, so that a deep fossa is formed on each surface, with that on
the anterior surface extending onto the dorsal part of the sacral rib. The posterior fossa is
deeper than the anterior fossa.
In ventral view, the anterior articular surface of sacral 3 is equal in width to the
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posterior margin of sacral 2. However, the centrum expands transversely towards its
posterior surface. The anteroventral ridges dividing the ventral from the lateral surfaces
of the centrum are more clearly defined than in sacral 2, and the ventral concavity on
sacral 3 is correspondingly deeper. A single small nutrient foramen is present in the centre
of the lateral surface. The anterodorsolateral part of the centrum bears an elongate facet
that extends for almost half of the length of the centrum, and which accommodates most
of the base of the third sacral rib. A smaller facet for articulation with the anterior part of
the fourth sacral rib is present on the posterodorsolateral corner of the centrum. The
neural arch of sacral 3 is effectively identical to that of sacral 2, although in dorsal view
the diapophysis is slightly shorter in sacral 3.
In almost all respects, sacral 4 is very similar to sacral 3 and only differences are
noted here. Sacral 4 has anterior and posterior articular surfaces that are subequal in
width in ventral view, unlike in sacrals 1–3 in which one articular surface is more
strongly expanded than the other. Sacral 4 also possesses the deepest ventral concavity of
any sacral vertebra. The lateral surface of the centrum possesses a single nutrient
foramen, but this is displaced more ventrally and posteriorly than in the preceding sacrals
due to the presence of a large attachment for sacral rib 4.
In ventral view, the centra of sacrals 5 and 6 are subequal in anterior and posterior
width. All of their articular surfaces are transversely narrower than the posterior articular
surface of sacral 4. Sacrals 5 and 6 still possess the ventral concavity, but this less clearly
offset from the lateral surfaces than sacrals 2–4. Distinct ridges separating the lateral and
ventral surfaces of the centrum are absent in sacral 5, but they are present in sacral 6 in
which they are similar to those occurring in sacral 3. These ventral concavities are absent
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or poorly developed in IVPP V15719, a smaller individual, so it is possible that these
features are subject to individual or ontogenetic variation. The posterior articular surface
of sacral 6 is bordered by rugose ornament as also occurs in some dorsal vertebrae. Sacral
5 possesses one nutrient foramen on the lateral surface of the centrum and two foramina
are present in the same position on sacral 6. Anterolaterodorsally, the centrum of sacral 5
bears a large facet for the fifth sacral rib that extends almost halfway along the centrum.
There is no facet for sacral rib 6, which is borne completely on the centrum of sacral 6
and extends for almost two-thirds of centrum length. The diapophyses for sacrals 5 and 6
appear to be longer and more robust than those of the preceding sacrals, but this may, in
part, be due to minor breakage of the latter. The distal ends of the diapophyses in these
vertebrae are strongly expanded anteroposteriorly, so that they are ‘T’-shaped in dorsal
view. The neural arches and spines are very similar to those described for the preceding
sacrals, although the neural spines are anteroposteriorly shorter in sacrals 5 and 6 than in
sacral 4. In sacral 6, the neural spine, which is the tallest of the sacral neural spines, bears
a ridge or swelling that arises on the posterior part of the lateral surface and that merges
with the rest of the spine dorsally. This ridge forms the posterior margin of a shallow
excavation that extends along the base of the spine.
In dorsal view, the diapophyses articulate with each other distally to form a narrow
sacricostal yoke that encloses a series of large, subcircular sacral foramina (the margins
of these foramina are complete between sacrals 2–3 and 5–6: the other diapophyses are at
least partially broken distally: Fig. 4D).
Caudal Vertebrae—The most complete caudal series is present in IVPP V12542,
which has caudal vertebrae 1–15 preserved in articulation in right lateral view (Fig. 5).
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IVPP V15939 includes the first nine caudal vertebrae in articulated series (Fig. 4); five
anterior caudals are preserved in articulation in IVPP V15719, in right lateral and ventral
views (Fig. 6); and IVPP V12529 includes several articulated sections of the tail,
consisting of middle and distal caudals (Fig. 7). In IVPP V12529, the neurocentral sutures
of the middle caudals are unfused, whereas those of the distal caudals are fused. All of the
neurocentral sutures in the anterior tail of IVPP V15939 are closed.
All of the caudal vertebrae are amphiplatyan or have gently concave articular
surfaces. In IVPP V15939, the centrum of caudal 1 has an anterior articular surface that is
as tall as it is wide, and the centrum length is also approximately equal to these two
diameters (Fig. 4B). These proportions change gradually along the anterior portion of the
tail, with anterior caudal centra further along the series becoming longer than they are tall
and developing posterior articular surfaces taller than wide (Fig. 4C). Both the lateral and
ventral surfaces of the centra very gently concave anteroposteriorly and these surfaces are
separated from each other by low, but distinct ridges. The lateral and ventral surfaces of
caudals 1–6 bear some small, irregularly distributed nutrient foramina, but these appear to
be absent thereafter. The ventral surface of the anterior caudals in IVPP V 15939 bears a
shallow groove, which contains a faint midline ridge. However, these features are absent
in IVPP V15719 and in this specimen the ventral and lateral surfaces are not separated by
ridges, but grade into each other. These differences may be ontogenetic as IVPP V15719
is considerably smaller than IVPP V15939.
In IVPP V15939, posterior chevron facets are present from the second caudal onward
and an anterior facet appears in caudal 3 and subsequent vertebrae. There is some
variation in this character, however, as IVPP V12542 appears to lack chevrons on the first
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two vertebrae (Fig. 5A). In addition, although IVPP V15719 has posterior chevron facets
on caudals 2 and 3, it does not gain anterior chevron facets until caudal 4. The chevron
facets have a subcrescentic outline in anterior or posterior view and the posterior facets
are more prominent than the anterior facets. The transverse processes of the anterior
caudals (broken at their bases in all specimens except IVPP V15939) project horizontally,
and curve slightly posteriorly in their distal part. They are elongate and taper distally to a
rounded terminus.
Anterior caudal vertebrae have gracile neural spines, which are anteroposteriorly
narrower and dorsoventrally taller than those of the sacral vertebrae, and which are
inclined slightly posterodorsally. The spines of the first four caudals are approximately
equal in height, but after this point they decrease in height caudally (Figs. 4, 5). In IVPP
V15939, the neural spines of anterior caudals 1–5 have a tear-drop-shaped transverse
cross-section, with plate-like anterior margins and posterior margins that are slightly
expanded transversely. This cross-section reflects expansion of the ventroposterolateral
margin of the neural spine, which occurs in the same manner as in sacral vertebra 6 (see
above). However, the development of this feature is more marked in than anterior caudals
than in the posterior-most sacral, so that the shallow excavation bordered by this swelling
on the lateral surface of the neural spine is more obvious than that seen in sacral 6.
Breakage of the neural spines or poor preservation prevents determination of how far this
feature continues along the proximal part of the tail. In IVPP V15939, the articular
surfaces of the pre- and postzygapophyses are more steeply inclined than in either the
dorsal or sacral vertebrae, being oriented at approximately 60° to the horizontal. The
prezygapophyseal articular surfaces are larger and broader than those of the
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postzygapophyses. Neither the pre- nor postzygapophyses extend far beyond the anterior
or posterior margins of the centrum. In lateral view, the postzygapophyses are positioned
dorsal to the level of the prezygapophyses.
The middle and posterior caudals of IVPP V12529 are poorly preserved and generally
lack most of the neural arch (Fig. 7). The middle caudals are essentially smaller versions
of the anterior caudals, although they exhibit a trend toward elongation of the centra, and
still bear chevrons and short transverse processes. Some of the centra retain a faint
ventral groove.
Posterior caudals become significantly more elongate, being at least twice as long as
they are high and the centra have a subrectangular cross-section (Fig. 7). Ventral grooves
are absent. Small transverse processes and chevron facets are present on the anterior-most
posterior caudals, but are absent more distally. In the posterior caudals, the
postzygapophyses fuse along the midline to form a single unified structure. Both the pre-
and postzygapophyses become very elongate, extending well beyond the anterior and
posterior limits of the centrum and exhibiting considerable overlap. The articular facets of
the zygapophyses become almost vertically inclined.
Chevrons—Eight chevrons are preserved in articulation with the anterior-most
caudal vertebrae of IVPP V15939 and can be seen in anterior, dorsal, and lateral views
(e.g., Fig. 4B, E). Four chevrons are preserved in articulation with the anterior tail in
IVPP V12542 (Fig. 5A), and IVPP V12529 includes three broken, disarticulated
chevrons. The following description is based on IVPP V15939. In anterior or posterior
view, the chevrons are approximately ‘Y’-shaped with a transversely expanded proximal
end consisting of two stout processes that merge distally to form the chevron blade. These
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processes form the lateral margins of the neural canal, which is bridged dorsally by a
continuous bar of bone that bears the articular facets for the caudal vertebrae. The
chevron blade tapers distally, to form a transversely compressed sheet. In lateral view, the
proximal end of the chevron is wedge-shaped and dived into anterodorsally and
posterodorsally facing articular surfaces: the anterior articular surface is smaller than the
posterior surface. The chevrons are anteroposteriorly expanded proximally, but narrow
ventrally. In chevron 2 the shaft tapers in lateral view and its distal end curves slightly
posteriorly, but in most other chevrons the anterior and posterior margins are subparallel
and the distal margin is squared-off. Chevron 8 differs from this general pattern in having
a distal end that is expanded anteroposteriorly relative to the shaft. Chevron 2 is longer
than chevron one, and the anterior-most chevrons appear to show an increase in overall
length, at least up to chevron 5 or 6, though many of the chevrons are broken distally
preventing determination of their total length.
Ossified Tendons—Ossified tendons are found extending alongside the neural spines
of the dorsal and sacral vertebrae in IVPP V15719, but are absent from the tail region.
The tendons are long and slender and cylindrical in cross-section. In IVPP V15939,
ossified tendons are preserved adjacent to the neural spines of the sacrum and might have
extended on to the first or second caudal vertebra (Fig. 5C). This distribution of ossified
tendons is similar to that in the early ornithischians Lesothosaurus (Thulborn, 1972),
Agilisaurus (Peng, 1992), and Heterodontosaurus (Santa Luca, 1980), some ornithopods
(e.g., Haya: Makovicky et al., 2011), and some basal ceratopsians and ceratopsids
(Dodson et al., 2004). However, it differs from the condition seen in other ornithopods
(e.g., Hypsilophodon: Galton, 1974) and some species of Psittacosaurus (e.g., P.
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xinjiangensis) in which ossified tendons extend along the caudal vertebrae. The tendons
lack a distinct lattice-like arrangement and appear to be arranged in linear bundles. There
is no evidence for the tendons extending onto anterior dorsals or cervical vertebrae in any
specimen.
Pectoral Girdle and Forelimb
Scapula—A left scapula is preserved in IVPP V15719, but its posterior portion is
partially damaged so the full extent of any posterior expansion cannot be assessed (Fig.
2A). The scapula and coracoid are unfused as also occurs in the majority of small
ornithischians (e.g., Galton, 1974; Scheetz, 1999), with the exceptions of Koreanosaurus
(Huh et al., 2010) and Oryctodromeus (Varricchio et al., 2007) in which a fused
scapulocoracoid is present. The scapula shaft is slender and blade-like with a
dorsoventrally convex lateral surface. The dorsal margin of the shaft is gently convex,
while the ventral margin is concave. Towards its posterior end, the blade expands slightly
dorsoventrally and it is bowed laterally along its entire length. Proximally the shaft
expands dorsoventrally to form the proximal plate, which comprises the humeral glenoid
and the articular surface for the coracoid (Fig. 2B). The dorsal margin of the proximal
plate is damaged and incomplete, but forms a low ridge-like acromial process, while a
second low ridge forms the ventral margin of the proximal plate, supporting the glenoid.
These two ridges merge into the base of the scapula blade caudally. The proximal plate
lacks the supraglenoid fossa and supraglenoid buttress present in Yueosaurus (Zheng et
al., 2012). The dorsal part of the proximal plate anterior margin forms a subcrescentic
articular surface for the coracoid. The ventral portion of the scapula anterior margin
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forms the glenoid cavity, which is slightly concave dorsoventrally, has a ‘D’-shaped
outline, and is transversely expanded relative to the rest of the proximal plate (Fig. 2B).
The scapula is very similar to that of other cerapodans and small ornithischians,
including Agilisaurus (ZDM T6011; Peng, 1992), Changchunsaurus (Butler et al., 2011),
Haya (Makovicky et al., 2011), Hexinlusaurus (ZDM T6001; He and Cai, 1984),
Hypsilophodon (NHMUK R196; Galton, 1974), Psittacosaurus (Sereno, 1990), and
Yueosaurus (Zheng et al., 2012), but it does not appear to be as elongate as that of
Heterodontosaurus (SAM-PK-K1332; Santa Luca, 1980). In contrast to Jeholosaurus,
Koreanosaurus possesses a scapula blade with a straight dorsal margin in lateral view
(Huh et al., 2010) and both Koreanosaurus and Oryctodromeus possess strongly
developed acromial ridges (Varricchio et al., 2007; Huh et al., 2010). Damage to the
proximal and distal ends of the scapula prevent additional comparisons with these other
taxa.
Coracoid—The left coracoid is preserved in IVPP V15719 in partial articulation
with the scapula (Fig. 2B). In lateral view, it is a small subquadrate plate with a slightly
convex external surface. A very small coracoid foramen appears to be present close to its
posterior margin. All of the margins of the coracoid are broken, preventing meaningful
comparisons with other taxa.
Humerus—A left and right humerus are preserved in IVPP V15719 and IVPP
V12542, respectively, both of which have suffered some damage to their proximal ends.
In anterior view, the humerus of IVPP V15719 is elongate, slender, and approximately
70% the length of femur (Fig. 8). The proximal end is gently inclined medially, with the
humeral head positioned at a level dorsal to the medial tubercle. This medial curvature is
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more strongly developed in the larger individual IVPP V12542 (Fig. 5C), which
potentially indicates some ontogenetic variation in this character. The anterior surface of
the proximal end is mediolaterally concave, with this concavity bounded laterally by the
presence of the anteriorly extending deltopectoral crest, which is oriented at
approximately 90° to the humeral shaft. The deltopectoral crest is complete in IVPP
V12542 (Fig. 5C: present but damaged in IVPP V15719, see Fig. 8) and is triangular in
outline. The medial margin of this proximal concavity is formed by a well-defined low
ridge that is continuous with the medial tubercle. Ventral to point at which the
deltopectoral crest merges with the shaft, the shaft is elliptical in cross-section. The distal
end of the humerus is slightly expanded transversely with respect to the shaft, to form the
two articular condyles, which are dumbbell-shaped in distal end view. The medial ulnar
condyle is broader than the lateral radial condyle, and projects slightly further anteriorly.
The anterior surface of the distal end is bears a shallow, broad intercondylar fossa, while
the posterior surface is flattened. In general, the morphology of humerus is exceptionally
similar to that of Changchunsaurus (Butler et al., 2011), Haya (Makovicky et al., 2011),
Hypsilophodon (NHMUK R196; Galton, 1974), Orodromeus (Scheetz, 1999),
Psittacosaurus (Averianov et al., 2006), and Yueosaurus (Zheng et al., 2012), but it
differs from the much stouter humeri present in Koreanosaurus and Oryctodromeus, in
which the shafts are relatively shorter and wider relative to the total length of the bone
(Varricchio et al., 2007; Huh et al., 2010).
Pelvic Girdle and Hind Limb
Ilium—Both ilia are present and well-preserved in IVPP V15939: the left ilium is
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essentially fully visible, while the medial surface of the right ilium is largely obscured by
matrix and its contact with the sacrum (Figs. 4, 9A, D). The left ilium (in lateral view)
and right ilium (again, in lateral view only) are well preserved in IVPP V12542 (Fig. 5A)
and IVPP V15719 (Fig. 6), respectively. Most of the following description is based on
IVPP V15939, supplemented with observations from the other specimens.
The ilium is anteroposteriorly elongate, consisting of a gracile preacetabular process,
a dorsoventrally tall main body, and a stout postacetabular process (Figs. 4C, 9A, D). In
lateral view, the surface of the ilium is flat to slightly concave, and the dorsal margin of
the ilium is convex in outline. Numerous short, fine, dorsoventrally oriented striations are
present around its dorsal margin. In dorsal view, the ilium is bowed medially, due to
slight lateral deflection of the preacetabular process (of approximately 10° from the
midline: Fig. 4D).
The preacetabular process accounts for approximately 40% of total ilium length. In
lateral view, the surface of the preacetabular process is gently concave dorsoventrally
(Figs. 4C, 9A). The process tapers anteriorly, reducing in dorsoventral height, and curves
anteroventrally. The medial surface of the process bears a prominent ridge, which extends
posteroventrally from its origin at a point approximately halfway along the dorsal margin
of the preacetabular process, fading into the main body of the ilium just dorsal to the
ischial peduncle (Fig. 9D). This ridge forms the dorsal border of a deep elongate groove
that tapers posteriorly and merges into the base of the pubic peduncle. The groove is
defined ventrally by a sharp medially extending shelf, which gives the preacetabular
process an almost ‘L’-shaped transverse cross-section. This medial shelf has a flat ventral
surface. In dorsal view, the narrow dorsal margin of the preacetabular process undergoes
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a slight decrease in its transverse width along its length.
The postacetabular process is shorter and deeper than the preacetabular process, and
accounts for 36% of ilium length, similar to the condition in many basal ornithischians
and ornithopods, including Haya (Makovicky et al., 2011), Hexinlusaurus (ZDM T6001;
He and Cai, 1984), and Hypsilophodon (NHMUK R196; Galton, 1974). It differs from
Psittacosaurus (Sereno, 1990) and Yinlong (IVPP V14530: HF–L, pers. obs.), which have
pre- and postacetabular processes of almost equal length, from Orodromeus, in which the
postacetabular process is relatively longer than the preacetabular process (Scheetz, 1999),
and from Heterodontosaurus, whose postacetabular process accounts for only ~25% of
total ilium length (SAM-PK-K1332; Santa Luca, 1980). The dorsal margin of the process
begins as a narrow ridge anteriorly, but thickens posteriorly to terminate in an obliquely
oriented truncated surface. The posteroventrolateral margin of the postacetabular process
forms a prominent ridge that extends anteroventrally to merge with the ischial peduncle.
This ridge forms the lateral margin of the brevis fossa. However, the brevis fossa is not
visible in lateral view (Fig. 9A), a character that also occurs in many ornithopods (e.g.,
Changchunsaurus [Butler et al., 2011], Hypsilophodon [NHMUK R196; Galton, 1974],
Orodromeus [Scheetz, 1999]), in contrast to the condition in basal ornithischians such as
Agilisaurus (ZDM T6011; Peng, 1992), Scelidosaurus (NHMUK R1111), Stormbergia
(NHMUK R11000; Butler, 2005), and some basal ornithopods (e.g., Haya: Makovicky et
al., 2011) in which the brevis fossa is visible in lateral view. The brevis fossa is
essentially absent in Psittacosaurus (Averianov et al., 2006), but is present in Yinlong (Xu
et al., 2006). In ventral view, the brevis fossa is elongate, shallow, and transversely
narrow. It is defined dorsally by a prominent brevis shelf that merges into the medial
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surface of the ischial peduncle cranially.
In lateral view, the acetabulum is fully open and is not backed by a sheet of bone
medially (Figs. 4C, 9A). A very weak supraacetabular buttress is present as a low ridge
forming the dorsal margin of the acetabulum, but this is not developed into a distinct
flange. The pubic peduncle is triangular in outline and in transverse cross-section. It
projects anteroventrally and slightly laterally, forming an angle of approximately 30° with
the preacetabular process, and tapers distally. It is not as robust as, and is slightly shorter
than, the ischial peduncle. The ischial peduncle is subtriangular in lateral view, with a
subovate articular surface that is directed laterally and slightly anteroventrally. As in most
basal ornithopods (e.g., Haya [Makovicky et al., 2011], Hypsilophodon [NHMUK
R2477; Galton, 1974], Orodromeus [Scheetz, 1999]), the ischial puduncle is more robust
than the pubic peduncle.
The dorsal portion of the medial surface of the iliac main body is obscured in most
specimens, but where visible is largely flat and featureless. The medial surface of the
pubic peduncle is deeply excavated to form an attachment scar for sacral 1 and two
prominent subelliptical scars on the medial surface of the main body represent the
attachment sites for sacral ribs 2 and 3.
Ischium—Ischia are preserved in IVPP V12542 (right ischium only: Fig. 5A), IVPP
V15719 (complete right ischium and broken, partially obscured left ischium: Fig. 6), and
IVPP V15939 (both ischia present and complete, although both proximal ends can be
separated from the block containing most of the pelvic material: Figs. 4A, D, E and 9B–C
and E–G). The proximal end of the ischium consists of two processes that arise from a
central plate: an anterodorsally facing iliac process and anteriorly extending pubic
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process (Fig. 9B–C, E–G). The pubic process is a little longer than the iliac process and is
also more compressed transversely. An angle of approximately 120° separates the
processes in lateral view, and the region between them forms the ischiadic contribution to
the acetabulum. The acetabular surface is smoothly convex anteroposteriorly and
maintains an almost constant width along its entire length. The lateral surface of the pubic
process is gently convex dorsoventrally and this convexity is maintained over most of the
lateral surface of the proximal plate and becomes stronger as the proximal plate merges
into the shaft. In contrast, the lateral surface of the iliac process is concave
dorsoventrally. In anterior view, the pubic articulation has an inverted ‘L’-shaped outline,
due to the presence of a small, medially extending process from the dorsomedial corner
of the otherwise subrectangular articular surface. A similarly shaped pubic articular
surface also occurs in Hypsilophodon (Galton, 1974). The articular surface on the iliac
process is divided into two facets: a dorsolaterally facing smooth area with a subovate
outline, and a posteriorly facing rugose surface with a subtriangular outline. The medial
surface of the proximal plate is generally concave anteroposteriorly, except for the iliac
process, which is anteroposteriorly convex.
The posteroventral corner of the proximal plate gives rise to the shaft, which has an
elliptical cross-section in its proximal part. The shaft undergoes torsion just distal to the
proximal plate, so that the majority of the shaft lies in a plane set at approximately 120°
to the anteroposterior plane of the proximal plate. In IVPP V15939, the dorsolateral
surface of the proximal shaft bears a shallow, distinct groove, which originates just
posterior to the junction between the plate and the shaft and that terminates at a point
approximately level with the anterior margin of the obturator process. This groove was
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present along the lateral surface of shaft in IVPP V15939. However, this groove is absent
in IVPP V12542 and IVPP V15719: the presence or absence of this feature might
represent an ontogenetic or taphonomic variation. The ventromedial margin of the shaft
possesses a proximally positioned prominent tab-like obturator process (Fig. 4A, D:
which is usually broken distally), as in Agilisaurus (ZDM T6011; Barrett et al., 2005),
Haya (Makovicky et al., 2011: although in this taxon the process is more distally
positioned than in Jeholosaurus), Hexinlusaurus (ZDM T6001; He and Cai, 1984),
Orodromeus (Scheetz, 1999), and Stormbergia (NHMUK R11000; Butler, 2005). This
differs from the condition in Hypsilophodon (NHMUK R196; Galton, 1974) in which the
obturator process is present but more distally positioned, and from Eocursor (Butler,
2010), Lesothosaurus (Butler, 2005), Heterodontosaurus (SAM-PK-K1332; Santa Luca,
1980), and basal ceratopsians (You and Dodson, 2004), which all lack the obturator
process. Posteriorly the shaft becomes dorsoventrally flattened and transversely
expanded, to produce a sheet-like cross-section. The lateral margin of the shaft thins to a
greater extent than the medial margin, and forms a sharp edge. By contrast, the medial
margin develops into a thickened ridge that runs along the dorsal margin of the distal-
most third of the shaft. The medial surface of the distal shaft is concave. The ischiac
shafts are appressed to each other for approximately 70% of their lengths distally.
Elongate ischiac symphyses also occur in basal ornithischians including Agilisaurus
(ZDM T6011; Barrett et al., 2005), Eocursor (Butler, 2010), and Lesothosaurus
(NHMUK RUB17; Butler, 2005). In Agilisaurus the symphysis accounts for
approximately 50% of ischial length (Barrett et al., 2005). Elongate distal symphyses are
absent in Hypsilophodon (Galton, 1974) and Stormbergia (Butler, 2005). The length of
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the ischiac symphysis cannot be measured accurately in Haya due to damage (see
Makovicky et al., 2011), but the more distally positioned obturator process of this taxon
indicates that its ischiadic symphysis must have been relatively shorter than that of
Jeholosaurus.
Pubis—No complete pubis is preserved, but the morphology of the pubes can be
nearly entirely reconstructed by combining information from IVPP V12542, IVPP
V15719, and IVPP V15939 (Figs. 4–6). IVPP V12542 and IVPP V15939 both include a
nearly complete right pubis, but the proximal plate is damaged in both specimens. IVPP
V15939 also includes the pubic rod of the left pubis, while IVPP V15719 possesses a
partial right pubis consisting of the proximal plate and a small section of the shaft.
In IVPP V15719 and V15939 the preserved part of the proximal pubis is a
transversely compressed plate of bone. The lateral surface of this plate is shallowly
concave in the former specimen and gently convex in the latter (Fig. 6). Most of the
description of the proximal plate is based in IVPP V15719 as the prepubic process and
iliac articular surface are broken in IVPP V15939. The posterodorsal margin of the
proximal plate is slightly expanded transversely to form a subrectangular articular surface
for the ilium. Anteriorly, the plate tapers to form a slender prepubic process with a
cylindrical transverse cross-section, as also occurs in a number of basal ornithichians and
basal ornithopods including Haya (Makovicky et al., 2011), Hexinlusaurus (ZDM T6001;
He and Cai, 1984), Hypsilophodon (NHMUK R195; Galton, 1974), and Orodromeus
(Scheetz, 1999). However, none of the available specimens preserves a complete
prepubic process, so it is not possible to determine if it terminated anterior or posterior to
the anterior end of the iliac preacetabular process. The posteroventral part of the proximal
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plate expands mediolaterally to form the base of the pubic rod.
It cannot be established with certainty if the obturator notch was open or closed as
the margins of this opening are partially broken in all specimens (Figs. 5, 6). However, in
IVPP V15719 the section of pubic rod ventral to the area where a notch might have been
positioned has surfaces composed of finished bone, lacking any trace of a broken surface
that might indicate the presence of a bony sheet that would have extended dorsally to
close the posterior margin of the notch: consequently, it seems likely that a notch was
present and opened posteriorly. This suggestion is also supported by the preserved
morphology of the proximal plate in IVPP V15939, in which the ventral corner of the
proximal plate appears to form a distinct ventrally directed process, which is separated
from the rest of the plate by a notch with smooth concave margins. Open obturator
notches are present in the majority of primitive cerapodans, including basal ceratopsians
such as Archaeoceratops (Dong and Azuma, 1997) and Psittacosaurus (Averianov et al.,
2006), basal ornithopods such as Haya (Makovicky et al., 2011), and more derived
ornithopods (Norman, 2004; Norman et al., 2004b) and ceratopsians (You and Dodson,
2004). This differs from the condition in basal ornithischians, such as Agilisaurus (ZDM
T6011; Barrett et al., 2005), Hexinlusaurus (ZDM T6001; He and Cai, 1984), some
specimens referred to Stormbergia (Butler, 2005), and the basal ornithopod Orodromeus
(Scheetz, 1999) in which the notch is closed to form a foramen. This character is
polymorphic in Hypsilophodon, as different individuals of this taxon exhibit either a
notch or a foramen (Galton, 1974).
The pubic rod is elongate, extends parallel to the ischial shaft and has a cylindrical
transverse cross-section (Figs. 4D, E, 5A). In IVPP V12542 and IVPP V15939, the
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ventral surface of the proximal part of the shaft bears a shallow groove, which attenuates
distally and disappears at a point approximately 25% of the distance along the shaft
length from the proximal plate.
Femur—Both femora are essentially complete and well preserved in IVPP V15939
(Fig. 10G–L) and IVPP V12542 (Fig. 5A), though those of the latter specimen remain
embedded in a block. The holotype specimen (IVPP V12529) includes an almost
complete left femur, which is missing only the femoral the head and the distal part of the
fourth trochanter, and the poorly preserved distal end of the right femur (Fig. 10A–F).
The left femur of IVPP V15719 is almost complete (Fig. 6), but its fourth trochanter is
broken, while the right femur is represented by distal part only.
The femur is long, slender, and bowed anteriorly in lateral view (Fig. 10A, I). The
degree of bowing varies somewhat between specimens, with that of smaller individuals,
such as the holotype, being more marked than in IVPP V15939. Proximally the femoral
head expands medially and slightly dorsally to form a large, subspherical articular
condyle. This is offset from the rest of the proximal end by a constricted, saddle-shaped
neck (the fossa trochanteris), which is concave mediolaterally and convex
anteroposteriorly (Fig. 10G, K). A fossa trochanteris is present in Changchunsaurus
(Butler et al., 2011), Hypsilophodon (NHMUK R196; Galton, 1974), Koreanosaurus
(Huh et al., 2010), and Orodromeus (Scheetz, 1999), but absent in some basal
ornithischians (e.g., Heterodontosaurus [Santa Luca, 1980], Fruitadens [Butler et al., in
press], Hexinlusaurus [He and Cai, 1984], and Lesothosaurus [Thulborn, 1972]), and
psittacosaurids (e.g., Psittacosaurus sibiricus [Averianov et al., 2006]). The posterior
surface of the femoral head is excavated by a deep groove (Fig. 10G, J), also present in
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Changchunsaurus (Butler et al., 2011), Hypsilophodon (NHMUK R196; Galton, 1974),
Koreanosaurus (Huh et al., 2010), and Orodromeus (Scheetz, 1999), which marks the
insertion of the M. iliotrochantericus (Maidment and Barrett, 2011). The greater
trochanter is expanded anteroposteriorly, and its dorsal margin is gently convex in the
same direction. In lateral view, a dorsoventrally extending ridge is present on the lateral
surface of the greater trochanter and proximal femoral shaft. It represents a ventral
extension of the proximal cleft separating the greater and anterior trochanters and extends
parallel to the anterior margin of the anterior trochanter (Fig. 10A, I). A similar ridge also
occurs in other small ornithischians (e.g., Changchunsaurus [Butler et al., 2011],
Hypsilophodon [Galton, 1974], Micropachycephalosaurus [Butler and Zhao, 2009]). This
ridge divides the lateral surface of the proximal femur into a narrow anterior region
(effectively the base of the anterior trochanter) for the M. iliofemoralis, and a broader,
posterior region for the insertion of the M. puboischiofemoralis internus (Maidment and
Barrett, 2011). The latter surface is finely striated and textured and is subdivided into
anterior and posterior portions by a low dorsoventrally extending ridge. The anterior
trochanter is a finger-like process with a suboval cross-section. In lateral and anterior
views, the tip of the anterior trochanter terminates ventral to the dorsal margin of the
greater trochanter (Fig. 10A, I, L). It is separated from the greater trochanter by a short
cleft, as also occurs in many other small ornithischians, such as Hypsilophodon (e.g.,
NHMUK R196; Galton, 1974), Orodromeus (Scheetz, 1999), Psittacosaurus (Sereno,
1990), and Yinlong (HF, pers. obs.). This differs slightly from the condition in some basal
ornithischians, including including Eocursor (Butler et al., 2007) and Hexinlusaurus (He
and Cai, 1984), in which the cleft separating the anterior and greater trochanters is
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deeper, and from heterodontosaurids like Heterodotosaurus and Fruitadens in which the
trochanters are fused to one another (Butler et al., in press).
A well-developed pendant fourth trochanter is present on the posteromedial edge of
the femoral shaft, and is situated on the proximal half of the shaft. In IVPP V12529, the
distance from the ventral margin of the fourth trochanter to the proximal margin of the
femur is approximately 45% of total femur length. The fourth trochanter has a flatted
medial surface and it is convex laterally with a ‘D’-shaped cross-section at its base,
which becomes narrow and triangular distally. In IVPP V15939, a long, deep depression
extends along the posterolateral margin of the shaft from a point just ventral to the greater
trochanter, until a point approximately 75% of the distance from the proximal end.
However, this feature is not present in any other specimen and is likely a result of
crushing and deformation. A subcrescentic depression on the posteromedial margin of the
shaft, adjacent to the fourth trochanter is the insertion for the M. caudofemoralis brevis. A
small circular foramen pierces the base of the fourth trochanter in posterior view, at a
point approximately halfway along the contact between the process and the shaft in IVPP
V12529 in IVPP V15939 (Fig. 10J). The shaft has a subcircular cross-section at
midlength.
In IVPP V15939, the anterior surface of the shaft bears a shallow and wide
depression, but this feature is absent or only incipiently developed in other individuals.
An anterior intercondylar groove is absent. Xu et al. (2000) suggested that the absence of
this feature might be diagnostic for Jeholosaurus, but many other small ornithopods and
basal ornithischians also lack an intercondylar groove and this is an ornithischian
symplesiomorphy (e.g., Norman et al. 2004b; Butler et al., 2008). All specimens exhibit a
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deep posterior intercondylar groove, separating the tibial and fibular epicondyles. In
distal end view, the medial (tibial) condyle is transversely wider than the lateral (fibular)
condyle and has a larger surface area (Fig. 10E, H). However, the two condyles extend
for the same distance from the shaft posteriorly and also extend to the same point
ventrally (except where deformation occurs, as in the left femur of IVPP V15939 and
right femur of IVPP V12529). In distal view, the articular surface is quite rugose. A
poorly developed shallow notch separates the lateral margin of the fibular condyle and
the fibula epicondyle in distal view, as also occurs in Hexinlusaurus (He and Cai, 1984)
and some individuals of Hypsilophodon (Galton, 1974).
Tibia—Both tibiae are present and complete in IVPP V12529, IVPP V12542, IVPP
V15719, and IVPP V15939 (Figs. 5A, 6, 11). The tibiae are often preserved in
articulation with the fibulae and the proximal tarsals. Tibiae of IVPP V15719 and IVPP
V12542 are still partially embedded in matrix, while those of the other specimens have
been completely prepared. The ratio of tibia to femur length ranges from 1.16–1.22 in
IVPP V12529, IVPP V12542, and IVPP V15939, and is similar to that of Hexinlusaurus
and Hypsilophodon (Barrett et al., 2005). However, this ratio is approximately 1.40 in the
smallest specimen (IVPP V15719), which may represent individual or ontogenetic
variation.
The tibia consists of proximal and distal expansions, linked by an elongate, slender
shaft (Fig. 11). The proximal end consists of a robust, laterally compressed cnemial crest
that extends anteriorly and slightly laterally, tapering toward a bluntly rounded apex. The
cnemial crest is separated from the laterally extending fibula condyle by a deep narrow
groove (Fig. 11E, M), in contrast to the much shallower groove separating these features
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in Hypsilophodon (Galton, 1974). A second well-defined sulcus separates the fibular
condyle from the inner condyle posterolaterally (Fig. 11E, M). Taken together the inner
condyle and the cnemial crest give the proximal end a crescentic outline, with the fibula
condyle extending from the centre of the crescent’s concave lateral surface. The cnemial
crest, fibula condyle, and inner condyle have approximately equal dimensions in
proximal view. The inner condyle tapers to the subtriangular, bluntly rounded apex,
whereas the fibula condyle has a broader, subrectagular lateral margin. The latter bears a
shallow notch, which is restricted to the surface of the condyle and does not extend
further ventrally on to the surface of the shaft. The entire proximal articular surface is
slightly rugose and anteroposteriorly convex.
Immediately ventral to the proximal expansion, the tibia narrows to form the shaft.
The grooves originating from the sulci separating the inner condyle/fibula condyle and
fibula condyle/cnemial crest extend along the posterolateral and anterolateral margins of
the shaft, respectively. Both of these grooves attenuate ventrally and disappear at a point
equal to approximately 25% of shaft length from the proximal end. The tibial shaft has a
circular cross-section at midlength, but this becomes subtriangular towards the proximal
and distal expansions. Distal to midlength, the anterolateral margin of the tibial shaft
bears an elongate, low rounded eminence that articulates with the medial surface of the
fibula. This eminence continues ventrally to merge with the lateral malleolus (Fig. 11A,
C, K, L).
Distally, the shaft expands mediolaterally to form the malleoli, whose long axis is
oriented transversely at approximately 90° to that of the proximal expansion. In anterior
or posterior view, the lateral malleolus extends further ventrally and is mediolaterally
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wider than the medial malleolus (Fig. 11A, C, K, L). The anterior surface of the distal
expansion bears a deep midline concavity whose ventral-most part would have
accommodated the ascending process of the astragalus. In posterior view, the medial
surface of the distal expansion is planar, the posterior surface is planar to very gently
concave, and these surfaces are separated by a distinct break in slope, forming a low,
proximally extending ridge that divides the medial and lateral malleoli. In distal end
view, the articular surface is approximately ‘L’-shaped, with the anterior surface of the
anteroposterioly narrow, transversely elongate, and laterally extending lateral malleous
forming an angle of around 120° with that of the anteroposteriorly expanded, transversely
narrow, and posteromedially extending medial malleolus. The articular surfaces of both
malleoli are rugose and end in blunt, rounded apices in distal end view.
In general, the tibiae of Jeholosaurus are very similar to those of Changchunsaurus
(Butler et al., 2011), Haya (Makovicky et al., 2011), Hypsilophodon (NHMUK R5830;
Galton, 1974), and Orodromeus (Scheetz, 1999), but are more gracile than those of
Psittacosaurus (Averianov et al., 2006).
Fibula—Complete fibulae are present in all of those specimens that include tibiae:
these two elements are usually preserved in articulation (Fig. 11). The fibula is an
elongate slender element with small proximal and distal expansions. The proximal end is
anteroposteriorly expanded with respect to the shaft, but is transversely compressed,
producing a subelliptical outline in proximal view. The articular surface is gently convex
anteroposteriorly and transversely. The medial margin of the proximal end is shallowly
concave, and this area articulates with the fibula condyle of the tibia. This medial
concavity continues onto the medial surface of the fibula shaft to create a shallow,
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ventrally extending groove that attenuates at a point approximately one-third of the way
along the fibula. Ventral to this point, the fibula has a subcircular cross-section, which is
maintained until a point just dorsal to the distal expansion, where the cross-section
becomes subtriangular, with the apex of this triangle situated anteriorly. The minimum
transverse width of the shaft in anterior view occurs at a point approximately two-thirds
of the distance from the proximal end of the bone. The proximal half of the fibula shaft is
separated from that of the tibia, whereas ventrally its medial margin is appressed to the
tibia. The distal articular surface has a subtriangular outline in distal view, and is
transversely expanded with respect to the shaft. The distal articular surface is convex and
articulates with a facet on the calcaneum. The ventromedial corner of the fibula has a
small contact with the astragalus. The fibula is not fused to the calcaneum (contra Zheng
et al., 2012).
Astragalus—Both astragali are preserved in IVPP V15939 (Fig. 11O–R), an
incomplete right astragalus and the ascending process of the left astragulus occurs in
IVPP V12529 (adhered to the left tibia: Fig. 11G–H), and IVPP V15719 includes the
right astragalus. The left astragulus is preserved in IVPP V12542, but the surface is
obscured by matrix and it offers few useful details. In all specimens that preserve both
elements, the astragalus and calcaneum are tightly appressed but do not fuse: the
articulation between them remains at least partially open. The contact between the two
elements occurs along a straight line that wraps around the anterior, ventral, and posterior
surfaces, but cannot be traced dorsally.
In anterior view, the lateral margin of the astragalus contacts the calcaneum (Fig.
11O). Progressing medially, the dorsal margin gives rise to a short, spur-like ascending
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process, before extending ventrolaterally to form the rounded medial margin of the
element. The medial margin of the astragalus is dorsoventrally shorter than its lateral
margin. The anterior surface bears one or two small foramina, which are situated ventral
to the ascending process: several areas of the surface are also slightly rugose, suggesting
that they were areas of muscle attachment. The ascending process is subrectangular in
anterior view, with a rounded dorsal margin, and extends dorsally and slightly laterally. A
narrow, deep, mediodorsally extending fossa is present on the lateral side of the
ascending process in both IVPP V12529 and IVPP V15939 (Fig. 11O). A similar feature,
described as a ‘forked ascending process’ is present in Orodromeus (Scheetz, 1999), but
is absent in Hypsilophodon (Galton, 1974). A shallow depression extends mediolaterally
across the anterior surface of the astragalus and on to the calcaneum: a similar depression
is reported in Haya (Makovicky et al., 2011).
The astragalus has a crescentic outline in medial view (Fig. 11S). This medial surface
is very gently concave, but becomes flatter as it tapers dorsally. In ventral view, the
astragalus is anteroposteriorly widest at its medially and tapers laterally toward its contact
with the calcaneum, giving it a wedge-like shape (Fig. 11Q). The ventral surface forms an
anteroposteriorly convex articular region that blends smoothly into the posterior surface
of the bone: the ventral and anterior surfaces are divided by an abrupt change of slope,
although there is no distinct ridge.
In dorsal view, the proximal surface bears a series of complex articular facets for
contacts with the tibia and fibula (Fig. 11R). A deep, obliquely oriented depression with a
saddle-shaped articular surface would have received the lateral mallelous and the lateral-
most portion of the medial malleolus. This facet consists of a deeply concave area
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laterally (the largest portion of the facet) that is defined posteriorly by a prominent
process arising from the posteromedial corner of the astragalus and delimited anteriorly
by a low ridge that forms the dorsal margin of the anterior surface. Moving laterally, this
facet arches dorsally to from a broad convex ridge that is defined posteriorly by the
posteromedial process and anteriorly by the ascending process (Fig. 11R). A small
dorsally facing facet with a subovate outline is situated immediately lateral to the base of
the ascending process and forms a small surface for contact with the distal fibula. A small
fossa is present on the dorsal surface close to the lateral margin of the element and may
represent a remnant of the junction between the astragalus and calcaneum. In posterior
view, the posteromedial process has a subtriangular outline that is tallest medially and
reduces in height towards the calcaneum (Fig. 11H, P).
Calcaneum—Calcanea are present in all of the specimens that also possess the
astragalus. The calcaneum is a small, block-like element whose lateral surface is
hemispherical in outline and bears a concave surface that is surrounded by prominent
ridge anteriorly and ventrally (Fig. 11T). A small triangular process extends
posterodorsally from a point halfway along the element’s posterodorsal margin and
articulates with the distal end of fibula laterally (Fig. 11O–R). In dorsal view, this process
marks the lateral end of a well-developed, mediolaterally extending ridge that divides the
articular surface of the calcaneum into two facets: a small, shallow anterior part and a
deeper, larger posterior part, which are separated from each other by an angle of
approximately 130° (Fig. 11R). The anterior facet has a wedge-shaped outline and forms
the articular surface for the distal fibula. It is confluent with a small fibula facet on the
anterolateral corner of the astragalus (see above) and is bounded anteriorly by a low rim
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of bone that forms the anterodorsal margin of the calcaneum. The posterior facet is
subrectangular in outline, continuous with the large tibial facet on the dorsal surface of
the astragalus, and articulated with the lateral mallelous of the tibia. The latter facet is
backed by a low ridge that forms the posterodorsal margin of the calcaneum. When in
articulation, the posterior, posterodistal, and lateral surfaces of the tibia are still visible. In
ventral view, the distal articular surface is strongly convex anteroposteriorly and bears a
rounded lateral margin (Fig. 11Q). The ventral surface of the calcaneum reduces in
anteroposterior width close to its junction with the astragalus, forming a narrow neck
between the calcaneum and astragalus.
Distal Tarsals—Two distal tarsals (representing fused distal tarsals 1+2 and a
separate distal tarsal 3) are preserved in articulation with the right pes of IVPP V15939
(Fig. 12G–K), with both feet of IVPP V12529 (though in the latter they are partially
obscured by other elements: Fig. 12L–P), and the right pes of IVPP V15719 (Fig. 13).
The distal tarsals are described with the foot held vertically.
Distal tarsals 1 + 2 appear to be fused to form a composite bone: there is no trace of a
suture between them in either IVPP V12529 or IVPP V15939 (Fig. 12K, L). This does
not appear to be under ontogenetic control given the size difference between these two
specimens. In dorsal view, distal tarsal 1 + 2 is a squat, reversed ‘L’-shaped element, with
horizontal bar of the ‘L’ forming distal tarsal 1 (identified on the basis of it capping the
proximal end of metatarsal 2), and the upright bar of the ‘L’ represents distal tarsal 2
(which caps the proximal end of a metatarsal 3). The element is dorsoventrally expanded
along its lateral margin, but tapers medially, so that both the anterior and posterior
surfaces are triangular in cross-section with the tip of the triangle pointing dorsomedially
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in both cases. The anterolateral corner is the deepest part of the bone. The anterolateral
surface bears a shallow crescentic concavity, while the rest of the proximal articular
surface is almost flat. A shallow and broad sulcus extends dorsoventrally along the
posterior surface of the bone and may represent a remnant of the junction between distal
tarsals 1 and 2. The lateral surface is slightly concave anteroposteriorly in order to
articulate with the medial margin of distal tarsal 3. In dorsal view, three shallow and
narrow grooves are present on the posterior margin of distal tarsals 1 + 2 (Fig. 12G).
Similar grooves are also present in the same position in some individuals in
Hypsilophodon (NHMUK R200).
Distal tarsal 3 has a wedge-shaped outline with a convex lateral and slightly concave
medial margin in proximal view (Figs. 12L, 13). The dorsal surface is concave and
surrounded by a raised rim of bone, which would have articulated with the astragalus. In
posterior view, a small foramen pieces on the center of the posterior surface. The anterior
surface is slightly concave: the ventral and lateral surfaces are obscured by the presence
of other elements. Distal tarsal 3 articulates with the proximal surface of metatarsal 4. In
IVPP V15939, the proximal articular surface of metatarsal 4 is concave, suggesting the
ventral surface of distal tarsal 3 is convex.
Distal tarsal number is somewhat variable among ornithischians (e.g., Norman et al.,
2004b). Two distal tarsals, sitting atop metatarsals 2–4 are present in Agilisaurus (Peng,
1992), Hexlinusaurus (He and Cai, 1984), Lesothosaurus (Thulborn, 1972),
Scelidosaurus (Norman et al., 2004a), some pachycephalosaurs (Maryanska et al., 2004),
basal ceratopsians (You and Dodson, 2004), and several basal ornithopods (Norman et
al., 2004b: including Haya [Makovicky et al., 2011]). Three distinct, unfused distal
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tarsals are present in Heterodontosaurus, with distal tarsal 1 situated above metatarsals 1
and 2, distal tarsal 2 above metatarsals 3 and 4, and distal tarsal 3 above metatarsal 4
(Santa Luca, 1980). The condition in Jeholosaurus in which three distal tarsals are
present, but with fusion of distal tarsals 1+2 (on the basis of positional relationships), is
unusual, but a similar condition also appears to be present in Orodromeus. The latter
taxon possesses a large “medial distal tarsal” (Scheetz, 1999:figs. 30D–F, 31), which is
‘L’-shaped in proximal view, bears possible evidence of a line of fusion between
potentially separate two ossification centres (a prominent ridge on its ventral surface:
Scheetz, 1999:fig. 30E), and articulates with the proximal ends of metatarsals 2 and 3.
Thus, this element may also represent the fused distal tarsals 1+2. An additional “lateral
distal tarsal” (Scheetz, 1999:fig. 30G–I) could therefore be interpreted as a distal tarsal 3.
This combination of features has not been described in any other ornithischians.
Metatarsus—Metatarsals are preserved in IVPP V12529, IVPP V15719, and IVPP
V15939 (Figs. 12, 13). IVPP V15939 processes both articulated metatarsalia, including
metatarsals 1–4 in each case (Fig. 12A, B), and in IVPP V15719 articulated metatarsals
1–4 are preserved on the right (Fig. 13) and 2–4 on the left with metatarsal 2 broken
distally. In IVPP V12529, metatarsals 1–5 are preserved in the right pes, but are generally
damaged or obscured proximally and metatarsals 1–4 are preserved in left pes (Fig. 12C–
F). IVPP V12542 includes left metatarsals 2–4. All of the metatarsals lie in almost the
same plane in IVPP V15719, IVPP V15939, and IVPP V12542, forming a posteriorly
concave shallow arch in dorsal view (Figs. 12A, B, 13). By contrast, in IVPP V12529 the
metatarsi have a more tubular arrangement, which was originally proposed as a
diagnostic feature of Jeholosaurus (Xu et al., 2000: Fig. 12C–F). However, this tubular
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arrangement is due to transverse compression of the pedes, which has caused bunching of
the metatarsals, and this morphology cannot be regarded as a useful diagnostic character.
Metatarsal 3 is the longest and stoutest, with metatarsal 1 being approximately 50% of
the length of metatarsal 3, as is common in basal ornithopods (Norman et al., 2004b).
Metatarsals 2 and 4 are approximately equal in length (Figs. 12A, B, 13). The dorsal
surface of the articulated metatarsus is transversely convex. Proximally, the metatarsals
are expanded anteroposteriorly, especially in metatarsals 2 and 3. All of the metatarsal
shafts are closely appressed throughout most of their lengths, separating from each other
ventrally just proximal to their distal articular surfaces. Many features of the metatarsals
are obscured by the close apposition of these elements in the articulated feet of the
available specimens. The metatarsi are described as held in a vertical orientation.
Metatarsal 1 is thin and splint-like proximally and does not articulate with the distal
tarsals. Its proximal end terminates slightly ventral to the proximal end of metatarsal 2
and the shaft of metatarsal 1 is closely appressed to that of metatarsal 2 along its entire
length. In medial view, it tapers ventrally, but expands anteroposteriorly towards its distal
end to form the articular region for phalanx 1-1. As a result, the anterior margin of the
shaft is strongly concave in medial view. In anterior view, the shaft of metatarsal 1 is
mediolaterally compressed proximally and expands transversely distally. The distal end is
weakly divided into lateral and medial condyles, which extends for the same distance
ventrally in anterior view. A shallow ligament pit appears to be present on the medial side
of this articular condyle (e.g., in the right metatarsal 1 of IVPP V15939), but there is no
trace of a lateral ligament pit.
Metatarsal 2 has a subelliptical outline in dorsal view, with its long axis extending
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anteroposteriorly. The medial margin of the proximal end is slightly emarginated and
forms the dorsal margin of shallow sulcus that extends a short distance along its medial
margin to house the head of metatarsal 1. The shaft retains a subelliptical cross-section
along its entire length, except in the distal articular region where it is subrectangular. In
medial view, the shaft of the metatarsal constricts anteroposteriorly just ventral to the
proximal end forming a concave proximal anterior margin, which then expands at the
distal end to form the articular surface for phalanx 2-1. The distal articular surface is
more strongly expanded than the proximal end of the metatarsal, both transversely and
anteroposteriorly. The shaft is essentially straight in both anterior and medial views and
its lateral surface is closely appressed to metatarsal 3: however, in anterior view, the
distal-most part of the shaft diverges a little medially, so that a short, narrow gap is
present between it and the distal end of metatarsal 3. The distal end bears a subdivided
articular condyle, with the medial condyle deflected medioventrally and slightly smaller
than the lateral one. A distinct groove separates the medial and lateral condyles
posteriorly, but does not extend on to the anterior surface of the shaft. A shallow pit is
present on the medial surface of the shaft and a deeper, larger pit is on the lateral surface.
Metatarsal 3 has a subrectangular proximal surface that is weakly concave both
laterally and medially for the reception of metatarsals 2 and 4. In anterior view, the shaft
is straight in its proximal part, but curves laterally towards its distal end. The posterior
surface bears a very shallow excavation, bounded medially and laterally by the margins
of the shaft, which extends for approximately 80% of shaft length before fading out
dorsal to the distal articular surface. As in metatarsal 2, the distal articular expansion is
subrectangular in cross-section, with the articular surface divided into two condyles by a
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groove posteriorly. A shallow ligament pit is present on the medial surface of the distal
articular expansion and a deeper pit occurs on the lateral surface. A deep fossa is formed
on the anterior surface of the distal end, just dorsal to the articular surface.
Metatarsal 4 has a wedge-shaped outline in proximal view, with the narrow end of
the wedge extending laterally. The shaft narrows in anteroposterior thickness ventrally
and maintains a subtriangular cross-section with the apex of the triangle extending
laterally. However, the shaft expands anteriorly in its distal-most part to form a
cylindrical cross-section, and then becomes subrectangular near to the distal end. In
anterior view, the shaft of metatarsal 4 is deflected more laterally than that of the other
metatarsals and has a sinuous outline. It extends parallel to metatarsal 3 in its proximal
half, but diverges laterally from metatarsal 3 for much of the rest of its length. However,
the distal-most end of the shaft changes course to extend more medially, bringing the
distal end back into contact with metatarsal 3. In posterior view, the shaft is widest
proximally, narrows distally, and expands slightly into the distal end. In distal view, the
triangular cross-section of the shaft results in an anteroposteriorly expanded medial
condyle and a reduced, ridge-like lateral condyle. In posterior view, a prominent
longitudinal ridge arises from the medial margin of the shaft at a point approximately
one-third of the way from the proximal end, and extends ventrally and progressively
more laterally until it terminates close the lateral border of the shaft, and merges into the
distal end.
Metatarsal 5 is present in the right pes of IVPP V12529 only. It is a small, slender,
distally tapering, and splint-like element with a mediolaterally compressed proximal end.
It is similar to those present in Haya (Makovicky et al., 2011), Hypsilophodon (Galton,
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1974), and Orodromeus (Scheetz, 1999); it is not clear if metatarsal 5 was present or
absent in Changchunsaurus (Butler et al., 2011).
Phalanges—Complete sets of phalanges are present in both feet of IVPP V12529
(Fig. 12E, F) and IVPP V15939 (Fig. 12A, B); IVPP V15719 includes phalanges 2-1 and
2-2 in the left pes and 4-1 in the right pes; and IVPP V12542 has phalanges 2-2 and 3-3
in right pes. In the following description, the phalanges are described as though held in
plantigrade stance. The phalangeal count is 2-3-4-5-0, as occurs in a variety of other basal
ornithopods, basal ceratopsians, and basal ornithischians (e.g., Agilisaurus [Peng, 1992],
Haya [Makovicky et al., 2011], Heterodontosaurus [Santa Luca, 1980], Hexilusaurus [He
and Cai, 1984], Hypsilophodon [Galton, 1974], Psittacosaurus [Averianov et al., 2006],
and probably Changchunsaurus [Butler et al., 2011]). Some of the phalanges are partially
reconstructed or may have been added from other individuals.
In dorsal view, all of the non-ungual phalanges are essentially similar in morphology,
differing only in proportions and subtle variations in the development of features
including the dorsal lappets and collateral ligament pits (see below: Fig. 12B). They
consist of a constricted central shaft with concave margins that connects the transversely
expanded proximal and distal articular surfaces. Well-developed, ‘V’-shaped lappets
extend posteriorly from the dorsal margins of all non-ungual phalanges, with the
exception of phalanges 1-1, 2-1, 3-1, and 4-1 in IVPP V12529 and IVPP V15719, as also
occurs in Haya (Makovicky et al., 2011) and Hypsilophodon (Galton, 1974). This
difference may be due to either ontogeny, as IVPP V15939 is the largest individual, or
some error in the reconstruction of the pes in the latter individual. In lateral view, the
ventral margins of the shafts are curved and dorsally concave, while dorsal margins are
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straight and slopes ventrally. Both the proximal and distal articular surfaces are
dorsoventrally expanded and this expansion is greater at the proximal end of the element.
Both lateral and medial surfaces of the distal articular surfaces bear well-developed
collateral ligament pits, and these become deeper and more clearly defined in distal
phalanges. In anterior view, the distal end of each phalanx is divided into lateral and
medial ginglymi, which bear a saddle-shaped articular surface.
All ungual phalanges are claw-like (Fig. 12A, B, E, F). In dorsal view, the unguals
are broadest proximally, taper distally to a narrow tip, and lack dorsal lappets. Laterally,
the proximal end is dorsoventrally expanded and the dorsal and ventral margins of the
ungual converge distally. The dorsal margin is arched and convex, while the ventral
margin is deeply concave, producing a strongly curved, ventrally extending, sharp distal
tip to the ungual. An elongate, shallow ligament groove originates from the proximal end
of the ungual and extends for almost the full length of the element on both lateral and
medial surfaces.
Phalanx 1-1 of Jeholosaurus is relatively short and does not extend to a point level
with the distal end of metatarsal 2 (Fig. 12A): this contrasts with Changchunsaurus,
which has a much more elongate phalanx 1-1 (Butler et al., 2011). The ungual phalanx of
digit 3 is longer than the other unguals (Fig. 12A), as also occurs in Hexinlusaurus (He
and Cai, 1984). This differs from Changchunsaurus, in which the length of the digit 2
ungual exceeds that of the digit 3 ungual (Butler et al., 2011). In addition, in
Jeholosaurus, phalanx 3-4 is the longest in digit 3 (IVPP V12529: Xu et al., 2000), as
also occurs in Xiaosaurus (Dong and Tang, 1983), whereas in Agilisaurus (Peng, 1992),
Changchunsaurus (Butler et al., 2011), Heterodontosaurus (Santa Luca, 1980),
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Hexinlusaurus (He and Cai, 1984), Hypsilophodon (Galton, 1974), Lesothosaurus
(Thulborn, 1972), and Orodromeus (Scheetz, 1999) this is not the case (Butler et al.,
2011).
PHYLOGENETIC ANALYSIS
To reassess the phylogenetic position of Jeholosaurus based upon the new
postcranial information provided here, we modified the matrix of Butler et al. (2011),
correcting their scores for Jeholosaurus (see Appendix 2 for character scores and Online
Supplementary Information for character list and data matrix). In addition, we added four
other East Asian small ornithischian taxa: the Early Cretaceous basal cerapodan
Albalophosaurus (using character scores taken primarily from Ohashi and Barrett, 2009),
the ‘middle’ Cretaceous Yueosaurus (scored based upon Zheng et al., 2012), the Late
Cretaceous Koreanosaurus (scored based upon Huh et al., 2010), and the Late Cretaceous
Haya (using character scores taken from Makovicky et al., 2011). Following Makovicky
et al. (2011), Bugenasaura was deleted and their character scores were used for
Thescelosaurus. The resultant data matrix consists of 227 characters and 54 taxa (see
Online Supplementary Information: note that an all-zero ‘dummy’ character was added at
the beginning of the matrix to aid with interpretation because TNT numbers characters
beginning with ‘0’). Following Butler et al. (2011), five characters (112, 135, 137, 138,
174) were treated as ordered.
The matrix was analysed using TNT (Goloboff et al., 2008). First, we analyzed
the matrix under the ‘new technology search’ option, using sectorial search, ratchet, tree
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drift, and tree fuse options with default parameters and 100 random addition sequences.
Second, these generated trees were analysed under traditional TBR branch swapping
(which more fully explores each tree island). The analysis recovered 3240 most
parsimonious trees (MPTs) of 577 steps. Standard bootstrapping (sampling with
replacement) was carried out using 1,000 replicates and a new technology search (ratchet,
with 10 random addition sequences). Reduced bootstrap standard frequencies were
calculated excluding five wildcard taxa (see below).
The strict consensus of these trees does not recover a monophyletic Ornithopoda,
and the phylogenetic positions of Jeholosaurus, Changchunsaurus, Haya, and the other
East Asian taxa (with the exception of Albalophosaurus, which is resolved within
Ceratopsia) are poorly resolved. The 50% majority-rule consensus tree places all of the
East Asian taxa (again, with the exception of Albalophosaurus) within an unresolved
polytomy at the base of Cerapoda. However, reduced consensus analysis (carried out
using the ‘Comparisons – Pruned Trees’ option of TNT) demonstrated that Yandusaurus
hongheensis, Anabisetia, Echinodon, Yueosaurus, and Koreanosaurus act as highly
unstable ‘wildcard’ taxa. A strict reduced consensus tree calculated a posteriori excluding
these taxa (Fig. 14) shows considerably greater resolution, and places Jeholosaurus,
Changchunsaurus, and Haya together within a clade (Jeholosauridae), with Jeholosaurus
and Changchunsaurus as sister taxa. Interestingly, Koreanosaurus is placed within
Jeholosauridae in a 50% majority-rule reduced consensus tree when Yandusaurus
hongheensis, Anabisetia, Echinodon, and Yueosaurus are excluded a posteriori, and
Yueosaurus, which has not formerly been included within a cladistic analysis, is placed
within Jeholosauridae in a 50% majority-rule reduced consensus tree when Yandusaurus
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hongheensis, Anabisetia, Echinodon, and Koreanosaurus are excluded a posteriori. Thus,
these two East Asian taxa might prove eventually to be members of Jeholosauridae, but
more detailed phylogenetic studies and new specimens of both are required to confirm
this hypothesis. Jeholosauridae is consistently positioned basally within Ornithopoda in
reduced consensus trees, but more derived than an Orodromeus + Zephyrosaurus clade.
This result is consistent with that recovered by Makovicky et al. (2011).
It has also been suggested that Koreanosaurus forms a clade with the North
American taxon Orodromeus, possibly together with Oryctodromeus and Zephyrosaurus
(Huh et al., 2010). However, although Orodromeus and Zephyrosaurus are recovered as
sister taxa by our analysis, we find no support for this more inclusive clade. Nevertheless,
we cannot test this alternative hypothesis fully herein, as our data matrix excludes
Oryctodromeus: only a brief description of this taxon has been published to date
(Varricchio et al., 2007), which is inadequate to allow comprehensive character scoring,
and we have not yet had the opportunity to examine this material ourselves.
DISCUSSION AND CONCLUSIONS
Although initially described as a basal ornithopod, Xu et al. (2000) noted that
Jeholosaurus shared some characteristics with marginocephalians and retained a number
of ornithischian symplesiomorphies. However, this work did not explore or discuss
ornithischian interrelationships within a rigorous phylogenetic framework. Subsequently,
incorporation of Jeholosaurus into a large-scale ornithischian phylogeny, confirmed the
suggestion of Xu et al. (2000), recovering Jeholosaurus as a basal member of
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Ornithopoda (Butler et al., 2008). This conclusion has been reinforced by the addition to
this dataset of new cranial data for this taxon (Barrett and Han, 2009) and, especially,
cranial and postcranial data from Changchunsaurus and Haya (Butler et al., 2011;
Makovicky et al., 2011). The new information on the postcranial anatomy of
Jeholosaurus presented herein provides additional support for this conclusion and for the
suggestion that these three taxa form a clade (Butler et al., 2011; Makovicky et al., 2011)
that might have been endemic to East Asia during the Cretaceous. Although
Changchunsaurus, Haya, and Jeholosaurus are very similar in overall anatomy, they can
be distinguished by sets of cranial and postcranial autapomorphies, as well as unique
combinations of character states (see comparative comments in the Description, above),
and probably represent a genuine radiation of small-bodied taxa. In this context, it is
noteworthy that Xu et al. (2000) proposed that several Chinese genera, spanning the
Middle Jurassic–Early Cretaceous (Agilisaurus, Hexinlusaurus, Jeholosaurus, and
Xiaosaurus) might have formed an endemic clade. However, three of these are currently
thought to represent more basally positioned ornithischian taxa that lie outside of
Ornithopoda (Butler et al., 2008). It is plausible that Koreanosaurus and Yueosaurus
might also be closely related to, or included within, Jeholosauridae. Small ornithopods
are generally rare in Eastern Asia and future work needs to resolve further the
phylogenetic affinities of taxa including ‘Gongbusauruswucaiwanensis and
Yandusaurus hongheensis in order to determine if any other Chinese taxa might shed light
on the early evolution of Jeholosauridae, or if they belong to other ornithischian lineages.
Although our analysis places Jeholosaurus within Ornithopoda, it should be noted
that relationships among basal cerapodan taxa remain weakly supported, and it is possible
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that the addition of new taxa or characters will have a major influence on tree topology,
especially as some basal ornithopods and basal marginocephalians are now known to be
more similar to each other than acknowledged previously. This point is illustrated by a
novel result from our analysis, which recovers the Early Cretaceous Japanese genus
Albalophosaurus as a basal marginocephalian, contrary to the earlier analysis of Ohashi
and Barrett (2009) that could only resolve this taxon as a basal cerapodan.
ACKNOWLEDGMENTS
PMB and RJB would like to thank HF-L and XX for their invitation to work on this
material. Funding for PMB to travel to China was provided by the Palaeontological
Investment Fund of the NHMUK, and this project was carried out under the auspices of a
Memorandum of Understanding between IVPP and NHMUK. Two anonymous referees
provided useful comments on an earlier version of this paper. HF-L and XX were
supported by grants from the National Natural Science Foundation of China. RJB is
supported by the DFG Emmy Noether Programme (BU 2587/3-1).
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Submitted Month 12, 2011; revisions received Month XX, XXXX; accepted Month XX,
XXXX.
Handling editor: XXXX.
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FIGURE CAPTIONS
FIGURE 1. Photographs and outline drawing of the cervical vertebrae of Jeholosaurus
shangyuanensis (IVPP V12529 and IVPP V12530). A, cervical vertebrae 1–7 of the
holotype IVPP V12529 in left lateral view; B, cervical vertebrae 2–9 (note only the
neural spine of the axis is preserved) and anterior dorsal vertebrae 1–2 of IVPP V12530
in right lateral view. Note the absence of parapophyses on dorsals 1 and 2; C, outline
drawing of cervical vertebrae 1–7 of IVPP V12529 in left lateral view; D, atlas-axis of
IVPP V12529 in anterior view; E, cervical vertebrae 1–7 of IVPP V12529 in dorsal view;
F, Cervical vertebrae 1–7 of IVPP V12529 in ventral view. Abbreviations: ax, axis; cr,
cervical rib; cv, cervical vertebrae; di, diapophysis; dv, dorsal vertebrae; gro, groove;
inc1, atlas intercentrum; inc2, axis intercentrum; na, neural arch; nc, neural canal; ns,
neural spine; odp, odontoid process; pa, parapophysis; poz, postzygapophysis; prez,
prezygapophysis; vk, ventral keel. [planned for page width]
FIGURE 2. Skull, neck, and pectoral girdle of Jeholosaurus shangyuanensis (IVPP
V15719). A, lateral view; B, ventral view. Abbreviations: c, coracoid; cr, cervical rib;
gc, glenoid cavity; sc, scapula. [planned for 2/3 page width]
FIGURE 3. The last four dorsal vertebrae of Jeholosaurus shangyuanensis (IVPP
V15939). A, left lateral view; B, ventral view. Abbreviations: di, diapophysis; ns, neural
spine; pa, parapophysis; poz, postzygapophysis; tp, transverse process; vk; ventral keel.
[planned for column width]
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FIGURE 4. Posterior dorsal vertebrae, sacrum, anterior caudal vertebrae, and pelvic
girdle elements of Jeholosaurus shangyuanensis (IVPP V15939). A, left lateral view; B,
left lateral view with pubis and ischium removed; C, right lateral view; D, dorsal view; E,
ventral view. Abbreviations: bs, brevis shelf; cav, caudal vertebrae; ch, chevron; dv,
dorsal vertebrae; il, ilium; is, ischium; ob, obturator process; ot, ossified tendons; pu,
pubis; sar, sacral rib; sv, sacral vertebrae. [planned for 2/3 page width]
FIGURE 5. Postcranial skeleton of Jeholosaurus shangyuanensis (IVPP V12542). A,
lateral view of the whole skeleton; B, ischia in posterior view; C, right humerus in
anterior view. Abbreviations: ca, caudal vertebrae; dc, deltopectoral crest; dv, dorsal
vertebrae; il, ilium; is, ischium; lfe, left femur; lp, left pes; lti, left tibia; pu, pubis; rfe,
right femur; rfi, right fibula; rh, right humerus; rti, right tibia; sa, sacral vertebrae; sk,
skull. [planned for page width]
FIGURE 6. Pelvic region of Jeholosaurus shangyuanensis (IVPP V15719) in ventral
view. A, photograph; B, outline drawing. Abbreviations: cav1, caudal vertebra 1; lfe, left
femur; lfi, left fibula; lis, left ischium; lti, left tibia; ril, right ilium; ris, right ischium;
rpu, right pubis; sv1, sacral vertebra 1. [planned for 2/3 page width]
FIGURE 7. Caudal vertebrae of Jeholosaurus shangyuanensis (IVPP V12529). A, middle
caudal vertebrae in lateral view; B, a series of posterior caudal vertebrae in dorsal view;
C, posterior caudal vertebrae in lateral view. Exact positions of these sequences within
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the tail are unknown. Abbreviations: ch, chevron; ns, neural spine; poz,
postzygapophysis; prez, prezygapophysis; tp, transverse process. [planned for column
width]
FIGURE 8. Left humerus of Jeholosaurus shangyuanensis (IVPP V15719). A, anterior
view; B, posterior view. Abbreviation: dc, deltopectoral crest. [planned for column
width]
FIGURE 9. Pelvic girdle of Jeholosaurus shangyuanensis (IVPP V15939). A, left ilium
in lateral view; B, right proximal ischium in lateral view; C, left proximal ischium in
lateral view; D, left ilium in medial view; E, right ischium in dorsal view; F, left ischium
in medial view; G, right ischium in medial view. The pelvic elements were detached from
the main pelvic block of IVPP V15939 for photography. Abbreviations: ilp, iliac
process; isped, ischiac peduncle; pp, pubic process; pped, pubic peduncle; prp,
preacetabular process; sras, sacral rib attachment scar. [planned for page width]
FIGURE 10. Femora of Jeholosaurus shangyuanensis (IVPP V12529 and IVPP V15939).
Left femur of IVPP V12529 in A, lateral, B, posterior, C, medial, D, anterior, E, distal,
and F, proximal views (note that the proximal head in missing in this specimen). Right
femur of IVPP V15939 in G, proximal, H, distal, I, lateral, J, posterior, K, medial, and L,
anterior views. Abbreviations: atr, anterior trochanter; dep, depression; fh, femoral
head; for, foramen; ftr, fourth trochanter; gtr, greater trochanter; ico, inner condyle; ls,
ligment sulcus; oco, outer condyle; rid, ridge; tub, tubcle. [planned for page width]
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FIGURE 11. Left tibia, fibula, calcaneum, and astragalus of Jeholosaurus
shangyuanensis (IVPP V15939 and IVPP V12529). Left tibia and fibula of IVPP V12529
in A, anterior, B, lateral, C, posterior, D, medial, E, proximal, and F, distal views. Distal
part of right tibia and fibula, calcaneum, and astragalus of IVPP V12529 in G, anterior,
H, posterior, I, medial, and J, lateral views. Left tibia and fibula of IVPP V15939 in K,
posterior, L, anterior, M, proximal, and N, distal views. Left calcaneum and astragalus of
V15939 in O, anterior, P, posterior, Q, ventral, and R, dorsal views; S, astragalus in
medial view; T, calcaneum in lateral view. Abbreviations: as, astragalus; ca, calcaneum;
cc, cnemial crest; fco, fibula condyle; fi, fibula; fos, fossa in ‘forked’ ascending process;
ico, inner condyle; proa, ascending process of astragalus; ti, tibia. [planned for 2/3 page
width]
FIGURE 12. Pedes of Jeholosaurus shangyuanensis (IVPP V15939 and IVPP V12529).
Left pes of IVPP V15939 in A, posterior/ventral and B, anterior/dorsal views (following
the different orientations used to described the metatarsi and phalanges in the text). Left
metatarsus of IVPP V12529 in C, posterior, and D, anterior views. Right pes of IVPP
V12529 in E, medial and F, lateral views. Distal tarsals of IVPP V15939 in G, anterior,
H, posterior, I, medial, J, lateral, and K, proximal views. Distal tarsals of IVPP V12529
in L, proximal, M, anterior, N, posterior, O, lateral, and P, medial views. Abbreviations:
for, foramen; mt, metatarsals; dp, dorsal pit; dt.1 + 2, fused distal tarsals 1 and 2; dt3,
distal tarsal 3; sul, sulci. [planned for page width]
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FIGURE 13. Right hind limb (in anterior view) and pes (in ventral view) of Jeholosaurus
shangyuanensis (IVPP V15719). Abbreviations: as, astragalus, ca, calcaneum, dt.1 + 2,
fused distal tarsals 1 and 2; dt3, distal tarsal 3; fe, femur; fi, fibula, mt, metatarsals, ti,
tibia. [planned for column width]
FIGURE 14. Strict reduced consensus tree of ornithischian interrelationships based on an
analysis of 227 characters for 54 taxa (see text and Supplementary Online Information for
details). Bootstrap values are shown above branches. [planned for page width]
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APPENDIX 1. Measurements for girdle and limb elements (all given in mm).
Measurements in plain type represent those take from complete elements; those in bold
figures indicate minimum measurements taken from partially broken or damaged
specimens; bold figures in parentheses are estimated total measurements from partially
broken or damaged specimens. Abbreviations: AP, the direction in which a specimen
was measured anteroposteriorly; Dm, the minimum height measured from the dorsal edge
of the ilium to the dorsal margin of the acetabulum; DV, the direction in which a
specimen was measured dorsoventrally; L, left; Le, the greatest length; Lp, the length
from the proximal end of the pubic process of the ischium to the point at which the two
ischial shafts meet along the midline; Lpf, the distance from the proximal end of the
femur to the base of the fourth trochanter; ML indicate the direction in which a specimen
was measured mediolaterally; Mw
,
the minimum width of the shaft; R, right; Wd, the
greatest length of distal end; Wp, the greatest length of proximal end; Wpp
,
the
mediolateral width of the pubic peduncle of the ilium..
TABLE 1. Measurements of the bones of the pectoral girdles.
Bone Specimen
Number L/R Le
(AP)
Le
(DV)
Wp
(DV)
Wp
(AP)
Wd
(DV)
Wd
(AP)
Wd
(ML) Mw
Scapula V15719 L 27.2
? 7.8(9) 5.3(DV)
Coracoid V15719 L
8.9 10.4 10
8.2(AP)
Humerus V12542 R
61.5
15.8
9.4
(11.5)
4.3(ML)
Humerus V15719 L
33.6
5.1(5.5)
6 2.4(ML)
TABLE 2. Measurements of the ilium
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Bone Specimen
Number L/R Le (AP)
Preacetabular Process Wpp
Dm
Le (AP) Width (DV)
Ilium
V15939 L 124 43.7 15.2 11.5 27.5
V15939 R 126.1 49.8 16.4 11.1 25.7
V12542 L 77.4 26.8 10.0
V15719 R 39.7(41.0) 13.6 5.2 2.4 8.4
TABLE 3. Measurements of the ischium and pubis
Bone Specimen
Number L/R Length Wp (AP) Wd
(AP) Mw Lp
Ischium
V15939 L 133.8 30.1 13.6 4.3 37.7
V15939 R 137.4 31.5 11.4 4.3
V12542 L 98.4(101) 13.2 4.6 3.0 25.9(29)
V15719 R 45.9(50) 6.1(9) 14.6
Pubis
V15939 R 3.7
V12542 R 2.8
V15719 R 5.6
TABLE 4. Measurements of the hand limb elements.
Bone Specimen
number L/R Le (DV) Wp (ML) Wp (AP) Wd
(ML)
Wm
(ML/AP) Lpf
Femur V15939 R 132.1 38.1 36.1 13.2 60.2
V15939 L 134.7 37.9 35.6 13.6 60.6
V12529 L 90.6 21 18.9 8.5 37.6
V12529 R 19.1 8.4
V12542 R 94.4 22.6 19.1 9.8 43
V12542 L 24.0 43.5
V15719 L 49.6 10.1 4.9 20.9
V15719 R 8.9
Tibia V15939 R 161.4 32.8 34.4 8.9
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TABLE 4. (Continued)
V15939 L 157.4 30.2 34.8 8.9
V12529 R 107.8 21.2 21.4 7.7
V12529 L 106.4 25.3 21.4 7.7
V12542 R 113.4 23.5 23.4 7.8
V15719 L 68.9 11.5 11.5 4.3
V15719 R 65.3 11.4 11.5 4
Fibula V15939 R 148.3 16.6(20) 11.3 4.3
V15939 L 151 20.8 11.8 4.9
V12529 R 101.3 13.2 6.2 2.4
V12529 L 100.8 14.1 6.8 2.9
V12542 R 100.1 3.0
V15719 R 60.8 6.9 3 1.3
TABLE 5 Measurements of pedal elements.
Specimen
number Bone L/R Le (AP)
Proximal end Distal end
Width
(ML)
Height
(DV)
Width
(ML)
Height
(DV)
V15939 Metatarsal I L 43.6 2.9 9.4 8.0 7.4
phalange1 15.3 8.8 9.0 7.7 6.9
phalange2 18.2 6.9 7.8
Metatarsal II 66.8 10.1 16.5 10.4 10.9
phalange1 23.4 10.4 10.1 19.5 9.1
phalange2 17.8 8.5 9.9 8.6 7.9
phalange3 25.8 7.6 7.7
Metatarsal III 76.2 8.9 15.3 13.5 9.5
phalange1 18.0 11.1 9.7 10.3 8.1
phalange2 18.0 8.5 10.3 8.2 7.0
phalange3 11.7 7.4 8.1 6.8 6.2
phalange4 30.7 8.0 8.1
Metatarsal IV 67.1 14.5 12.5 10.0 10.2
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TABLE 5. (Continued)
phalange1 16.9 9.5 9.5 9.9 6.9
phalange2 13.1 8.7 9.0 8.7 6.7
phalange3 11.8 8.6 8.7 8.4 6.4
phalange4 10.8 7.7 8.3 8.2 6.7
phalange5 21.9 7.9 8.3
Metatarsal I R 44.3 4.3 8.4 8.3 8.0
phalange1 15.4 8.1 9.2 7.5 6.2
phalange2 17.9 6.8 8.2
Metatarsal II 69.1 9.2 20.3 10.3 9.0
phalange1 21.8 10.4 10.2 8.9 8.0
phalange2 15.5 8.7 9.3 7.4 6.8
phalange3 24.5 6.8 7.6
Metatarsal III 75.7 7.8 17.1 13.7 10.1
phalange1 18.5 10.7 10.5 10.8 8.2
phalange2 16.1 10.2 9.7 9.3 8.0
phalange3 11.9 8.5 8.5 7.6 7.3
phalange4 25.8 7.5 7.5
Metatarsal IV 65.8 12.4 11.4 9.2 12.5
phalange1 16.4 10.4 10.1 9.3 7.8
phalange2 13.7 8.9 9.2 8.7 7.7
phalange3 11.7 8.4 8.8 8.0 7.5
phalange4 11.4 7.6 8.0 6.6
phalange5 20.9 7.5 7.3
V12529 Metatarsal I L 13.7 (25) 1.0 3.8
Metatarsal II 48.1 5.4 13.0 7.0 7.6
phalange1 (15.2) 6.6 6.6
phalange2 13.7 6.8 7.2 5.4 5.4
phalange3 16.7 5.5 5.6
Metatarsal III 53.5 5.6 9.1 6.8
phalange1 18.4 9.5 8.1
(10)
6.3
phalange2 12.8 8.6 6.5 7.0 5.9
phalange3 13.1 7.8 7.2 6.0 5.0
phalange4 16.2(18)
5.9 5.5
Metatarsal IV 47.6 8.2 8.6 5.7 6.7
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TABLE 5. (Continued)
phalange1 11.9 7.9 7.2 5.7 5.7
phalange2 10.0 4.5 7.0 (5.0) 5.1
phalange3 9.1 6.6 4.7
phalange4 8.1 6.2 4.3
phalange5 13.8 4.6 4.8
Metatarsal I R 22.5(25) 4.8 4.6
phalange1 11.1 5.9 5.7 4.9 4.3
phalange2 4.3 4.9
Metatarsal II 41.5(49)
))
)
6.0 7.9
phalange1 16.4 6.4 7.6 5.3 5.7
phalange2 13.3 7.7 4.6
phalange3 9.0(12) 5.1
Metatarsal III 54.1 7.2 9.0 6.6
phalange1 17.6 9.3 7.8 7.8 6.4
phalange2 12.7 8.0 7.8 6.9 5.9
phalange3 6.8 6.1 7.3 7.0 6.2
phalange4 16.7 4.4 6.8 0.0 0.0
Metatarsal IV 40.5(50) 9.7 5.9
phalange1 12.2 7.5 5.6
phalange2 10.0 7.4 5.0
phalange3 9.6 6.1 3.9
phalange4 9.1 6.1 3.8
phalange5 12.2 4.2 7.0
Metatarsal V 19.6 2.8 6.8
V12542 Metatarsal II R 50.2 7.8
phalange1 17.0 8.6 7.4
Metatarsal III 59.4 8.0 9.7
phalange1 18.1 9.3 9.1 6.3
Metatarsal IV 50.1 8.6 6.7 7.8 6.5
V15719 Metatarsal II L 33.5 3.1 3.1
phalange1 9.3 2.6 2.7 3.1
phalange2 8.6 2.8 3.6 2.8 2.7
Metatarsal III 37.8 3.7 5.4 4.8 3.7
Metatarsal IV 21.7(33) 4.2 5.0
Page 91 of 94
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Journal of Vertebrate Paleontology: For Review Only
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TABLE 5. Continued
Metatarsal I R 19.9 2.9 2.5
Metatarsal II 33.1 2.0 3.0 3.7 3.4
Metatarsal III 36.0 3.0 4.5 3.6
Metatarsal IV 31.5 4.6 4.0 4.0
phalange1 8.1 4.0 3.4 3.0 2.9
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APPENDIX 2. Updated character scores for Jeholosaurus shangyuanensis, Koreanosaurus
(based on Huh et al., 2010), and Yueosaurus (based on Zheng et al., 2012), and additional scores
for Albalophosaurus. The latter taxon was originally scored for inclusion in an expanded version
of Butler et al. (2008) (see Ohashi and Barrett, 2009), whereas the most recent iteration of this
phylogeny incorporates six new characters (characters 222–227: Butler et al., 2011), whose
scores are provided here. Other scores for Albalophosaurus remain unchanged from those in
Ohashi and Barrett (2009). The full data matrix used for the analysis conducted herein is
available as Online Supplementary Information and the character list is published in Butler et al.
(2011). Characters for Jeholosaurus whose scoring differs from that in Butler et al. (2011),
following from the new data presented herein (mainly as the result of adding previously missing
data), are shown in bold type: these account for changes in 52 character scores (23% of the total).
1 11 21 31 41
Jeholosaurus 0?0--11001 1010-00011 000??10?10 000100-000 1000010000
Koreanosaurus ?????????? ?????????? ?????????? ?????????? ??????????
Yueosaurus ?????????? ?????????? ?????????? ?????????? ??????????
51 61 71 81 91
Jeholosaurus 0110000001 11010000-- 0000100?00 ?001???001 1100001000
Koreanosaurus ?????????? ?????????? ?????????? ?????????? ??????????
Yueosaurus ?????????? ?????????? ?????????? ?????????? ??????????
101 111 121 131 141
Jeholosaurus 1101000000 001011?110 0-00001111 00001??300 00?0?1??10
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Koreanosaurus ?????????? ?????????? ?????????? ???0?????? ???????100
Yueosaurus ?????????? ?????????? ?????????? ???0?????? 00?0?????0
151 161 171 181 191
Jeholosaurus 01000????? ???0100000 0-11101100 00110110-? 01???10131
Koreanosaurus 10?01????? ???0???0?? ????111?0? ?????????? ??????0131
Yueosaurus 00?00????? ?????????? ?????????0 ?0???110?? ?????10???
201 211 221
Jeholosaurus 2000011110 10--01?000 0??0001
Koreanosaurus 200011???? ?????0??00 0?000?1
Yueosaurus 20???1???? ????000?00 0??000?
New scores for Albalophosaurus: character 222(1); characters 223–227 all ‘?’.
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... Heterodontosaurus tucki (Butler et al., 2008a) and Fruitadens haagarorum (Butler et al., 2012). The latter is used in this revision (Figure 4.14). ...
... Heterodontosaurus Nesbitt, 2011) and Fruitadens (Butler et al., 2012). ...
... B408. Fibula, distal end is strongly reduced and splint-like: 0, absent, 1, present (Han et al., 2012). ...