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第47 卷摇第1期
2009 年1月摇摇摇摇摇摇摇 古 脊 椎 动 物 学 报
VERTEBRATA PALASIATICA 摇摇摇摇摇摇摇摇摇摇 pp.1 - 20
摇 figs.1 - 8
短吻贫齿龙(双孔亚纲:海龙目) :
头后骨骼及系统关系研究1)
吴肖春1,2摇程延年2摇佐藤环3摇单希瑛2
(1 加拿大自然博物馆摇渥太华 ON K1P 6P4)
(2 中国台湾自然科学博物馆摇台中 40453 )
(3 日本东京学艺大学摇东京 184 - 8501)
摘要:短吻贫齿龙是根据一保存较完整的头骨和下颌标本建立的;标本采自贵州关岭地区三
叠系法郎组灰岩。对其头后骨骼进行了详细描述。短吻贫齿龙在肩带的乌喙骨和间锁骨及
腰带的肠骨显示了与众不同的特征,例 如:紧靠肩臼后方乌喙骨有一明显的凹,间锁骨后半
部比前部要窄很多,及肠骨背突末端加宽等。头骨进一步细修表明,其中 一些部位需要进行
重新记述。依据头后骨骼和头骨中的新信息,对短吻贫齿龙的特征作了修订。系统关系分析
表明,贫齿龙是个 askeptosaurid,其下颌宽大于长的反关节突和肱骨缩小的三角 -胸大肌嵴表
明它与产自瑞士和意大利的 Askeptosaurus 关系最近。
关键词:贵州关岭,三叠纪,海龙目贫齿龙,头后骨骼,系统关系
中图法分类号:Q915. 864摇 文献标识码:A摇 文章编号:1000- 3118( 2009) 01- 0001- 20
MIODENTOSAURUS BREVIS CHENG ET AL.,2007 (DIAPSIDA:
THALATTOSAURIA): ITS POSTCRANIAL SKELETON AND
PHYLOGENETIC RELATIONSHIPS
WU Xiao鄄Chun1,2* 摇 CHENG Yen鄄Nien2摇 SATO Tamaki3摇 SHAN Hsi鄄Yin2
(1 Canadian Museum of Nature Ottawa ON K1P 6P4, PO Box 3443 STN “ D冶, Canada *Corresponding author:
摇 xcwu@ mus鄄nature. ca)
(2 Museum of Natural Science Taichung 40453, 1, Kuan Chien RD, Taiwan, China)
(3 Tokyo Gakugei University Tokyo 184 - 8501, 4- 1- 1 Nukui鄄Kita鄄Machi, Koganei City, Japan)
Abstract摇Miodentosaurus brevis was first established on the basis of the skull and mandible of a fairly
preserved skeleton from the Triassic Falang Formation, Guanling area, Guizhou Province. The descrip鄄
tion of the postcranial skeleton reveals that M. brevis is also distinct in the morphology of its girdle ele鄄
ments, such as the coracoid with a small embayment just posterior to the glenoid, interclavicle becoming
much narrower posteriorly than anteriorly, and the ilium having a dorsal blade with a expanded distal
end. With a further preparation, some of the skull anatomy are redescribed. Based on new information
from both skull and the postcranial skeleton, the diagnosis of the taxon is revised. A phylogenetic analy鄄
sis suggests that M. brevis is an askeptosauroid, closely related to Askeptosaurus from Switzerland and
Italy on the basis of two unequivocal synapomorphies, a retroarticular process broader than long and a
reduced deltopectoral crest in the humerus.
Key words摇 Guanling, Guizhou; Triassic; Thalattosauria, Miodentosaurus; postcranial skeleton; phylogeny
1) 中国科学院、国家外国专家局创新团队国际合作伙伴计划资助。
收稿日期:2008- 07- 03
2摇摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
1摇 Introduction
The holotype specimen (housed in National Museum of Natural Science, with a catalogue
number of NMNS 004727 / F003960) of Miodentosaurus brevis Cheng et al., 2007 was collected
from the Falang Formation (upper Middle to lower Upper Triassic) of Guanling area, Guizhou
Province, China. Its skull and mandible was first described by Cheng et al. (2007) while its post鄄
cranial skeleton was still in the matrix. Now the latter is fully prepared and described here. Before
the postcranial description, an anatomical revision of the skull and mandible is made on the basis of
a further preparation using Sand Bluster. With information drawn from the postcranial skeleton, the
diagnosis of M. brevis is revised and its phylogenetic relationships among thalattosaurians are ana鄄
lysed. M. brevis is an askeptosauroid (see the text below) and the morphological comparison is
made mainly with the taxa of the Askeptosauroidea (sensu Liu and Rieppel, 2005).
Neosinasaurus hoangi Zhou, 2000 (Zhou in Yin & Zhou, 2000)( = Sinasaurus hoangi Zhou,
2000 (Zhou in Yin et al., 2000)), Wayaosaurus geei Zhou, 2000 (Zhou in Yin et al., 2000), and
Wayaosaurus bellus Zhou,2000 (Zhou in Yin et al., 2000) were originally described as pachypleuro鄄
sauroids on the basis of unprepared specimens. Our examination of the true specimens indicates that
both genera are thalattosaurians. The original description of the two genera was not accurate or
wrong in many places; it is, for instance, obvious that both have only two rather than five sacral
vertebrae. N. hoangi (Gmr001, type specimen) appears to be similar to Miodentosaurus brevis but
clearly differs from the latter in that the neural spine of dorsal vertebrae is not constricted around
their base and the humerus is nearly symmetrically incurved on both sides. The paratype skull
(Gmr002) of N. hoangi bears a median ridge along the dorsal mid鄄line of the premaxillae as in M.
brevis but the neural spine of its dorsal vertebrae shows no constriction around the base. Any taxo鄄
nomic verification of N. hoangi has to wait for a full preparation of the specimens. It is possible that
the type and paratype of the taxon could represent two different thalattosaurians. W. bellus and W.
geei are separately based on a specimen preserved in ventral view. The specimen of W. bellus was
not accessible but the relatively long symphysis of its mandible (see fig. 2, 4 in Plate II in Zhou,
2000 (in Yin et al., 2000)) is not comparable to that of M. brevis. There is no doubt that the speci鄄
men of W. geei (Gmr004) is not referable to M. brevis because its mandibular symphysis is even rela鄄
tively longer than that of W. bellus. Again, the true taxonomic status of the two species of Wayaosau鄄
rus can be clarified until their specimens are fully prepared.
2摇 Description and comparison
Revision of the skull and mandibular anatomy摇 Fine preparation of the skull using Sand
Bluster shows that some skull elements were not properly described or even inaccurately interpreted
in Cheng et al. (2007), which are clarified here. 1) The maxillary鄄jugal relationship along the ven鄄
tral margin of the orbit was figured in the previous study as that the maxilla extends posteriorly me鄄
dial to the jugal (see fig. 2A in Cheng et al., 2007). This is not the case but the opposite is true
(Fig. 1), as in other thalattosaurians. 2) The frontal resembles that of most thalattosaurians in pos鄄
sessing a posterolateral process, but it is very peculiar in that the bone forms the anterior margin of
the pineal foramen (Fig. 1). This is unique among thalattosaurians. 3) The parietal is also very
distinctive in having a slender anterolateral process that wraps the posterolateral process of the fron鄄
tal. Again, this is unique among thalattosaurians. 4) The ventral edge of the surangular of the man鄄
dible is not as straight as figured in the study of Cheng et al. (2007) but abruptly convex at the
posterior third of the bone; in other words, the surangular suddenly broadens ventrally at the place
so that the surangular/ angular suture turns downward (Fig. 2). This appears to be unique for Mio鄄
dentosaurus brevis. The surangular/ angular suture also turns downward in Thalattosaurus alexandrae
(see fig. 2 in Nicholls,1999) but it is much weaker and more anteriorly positioned.
1期 吴肖春等:短吻贫齿龙(双孔亚纲:海龙目):头后骨骼及系统关系研究 3摇摇摇摇
Fig. 1摇 Photo ( A) and outline of the photo ( B) of the skull, mandible, and the first four cervical vertebrae
of Miodentosaurus brevis Cheng et al., 2007 in dorsal (the skull and right ramus of the mandible) and lateral
(the left ramus of the mandible and the four cervicals) views
Abbreviations: af. articular fossa 关节窝; amf. adductor mandibular fossa 下颌收肌窝; an. angular 隅骨;
ar. articular 关节骨; atar. atlantal neural arch 环椎神 经弓; atic. atlantal intercentrum 环椎间 椎体; ax.
axis 枢椎; cr. cervical rib 颈肋; cv. cervical vertebra 颈椎; d. dentary 齿骨; en. external naris 外鼻孔; f.
frontal 额骨; fo. foramen 孔; hy. hyoid 舌骨; j. jugal 轭骨; lp. lateral process of surangular 上隅骨外侧
突; m. maxilla 上颌骨; n. nasal 鼻骨; od. odontoid process of axis 环椎齿突; p. parietal 顶骨; pat. proat鄄
las 前环椎; pfo. pineal foramen 松果孔; pm. premaxilla 前颌骨; pmc. premaxillary crest 前颌骨嵴; pof.
postfrontal 后额骨; pps. slit鄄like postfrontal / parietal suture, indicating the position of the supratemporal fe鄄
nestra 狭长切口样的后额骨 /顶骨缝,表明原来上颞 孔的位置; prf. prefrontal 前额骨; pt. pterygoid 翼
骨; pz5. left prezygapophysis of cervical vertebra 5 第五颈椎 后关节突; q. quadrate 方骨; qcd. quadrate
condyle 方骨髁; qs. quadrate shaft 方骨杆; rap. retroarticular process 反关节突; sa. surangular 上隅骨;
sp. splenial 夹板骨; sq. squamosal 鳞骨; st. supratemporal 上颞骨; tyc. tympanic crest 鼓膜附嵴
4摇摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
Fig. 2摇 Photo ( A) and outline (B) of the skull, mandible, and the first four cervical vertebrae of Miodento鄄
saurus brevis Cheng et al., 2007 in ventral ( the skull and right ramus of the mandible) , medial ( the left
ramus of the mandible), and lateral (the four cervicals) views
Abbreviations as in Fig. 1 plus bo. basioccipital 基枕 骨; bs. basisphenoid 基蝶 骨; ch. choana 内鼻孔;
cn. coronoid 冠状骨; dsy. dentary symphysial facet 齿骨联合 面; dt. dentary tooth 齿骨齿; dts. dentary
tooth socket 齿骨齿窝; dts5. socket for dentary tooth 5 第五齿 骨齿窝; ec. ectopterygoid 外翼骨; ep.
epipterygoid 上翼骨; ica. internal carotid artery 内颈动脉孔; mgr. groove鄄like trough in maxillary 上颌骨
沟状槽; par. prearticular 前关节骨; pl. palatine 腭骨; pmt. premaxillary tooth 前颌骨齿; pop. parocci鄄
pital process 副枕突; prq. pterygoid ramus of quadrate 方骨翼骨支; ptv. pterygoid vacuity 翼骨间窝; qrp.
quadrate ramus of pterygoid 翼骨方骨支; sof. suborbital fenestra 眶下孔; spsy. splenial symphysial facet
夹板骨联合关节面; sta. stapes 镫骨; stf. trace of supratemporal fenestra 上颞孔遗迹; vo. vomer 犁骨
1期 吴肖春等:短吻贫齿龙(双孔亚纲:海龙目):头后骨骼及系统关系研究 5摇摇摇摇
Fig. 3摇 Skeleton of Miodentosaurus brevis Cheng et al., 2007 in ventral ( the skull and right ramus of the
mandible), medial (the left ramus of the mandible), and lateral (the postcranial skeleton) views ( circled
areas are reconstructed)
6摇摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
Axial skeleton摇 With the skull and mandible, the postcranial skeleton of Miodentosaurus
brevis is articulated and well preserved although the zeugopodium, the manus of the left hind鄄
limb, and some caudal vertebrae (3- 5, 12, 13, about 20 of the posterior most section) are
missing (Fig. 3). There are 87 vertebrae preserved, consisting of 38 presacrals ( 13 cervicals
and 25 dorsals), two sacrals, and 47 caudals. The cervicals are fewer in number than 15 or 16
of an askeptosauroid, Anshunsaurus species from south鄄western Guizhou, the number of the lat鄄
ter was recently clarified in a juvenile specimen (Liu, 2007). All but the atlas鄄axis complex
are amphicoelous. Sutures between the neural arches and centra are visible in all cervical and
the first five dorsal vertebrae, and evident in the posterior half of the other pre鄄caudal verte鄄
brae. Most of cervical and all preserved caudal, except for the first several, vertebrae are later鄄
ally compressed during fossilization.
The atlas鄄axis complex is better exposed on the left side. The atlas is represented by its in鄄
tercentrum and left neural arch, which are in their original position ( Fig. 4A). The intercen鄄
trum shows the left ventrolateral side, which is convex and has a thickened lateral margin. The
neural arch is slightly detached from the intercentrum. It is anteriorly convex, posteriorly con鄄
cave, ventrally massive, and dorsally narrows into the neural spine. The broken surface sug鄄
gests that the spine is missing its distal end. The lateral surface of the neural arch is bulged out
but becomes concave close to its ventral margin; its anterior portion is thickened but the arch
thins posteriorly. The thick ventral side of the arch is convex, with two facets; the anterior one
for the atlantal intercentrum and the posterior one probably for the atlantal rib. A piece of bone
anterior to the atlantal neural arch is probably the proatlas. A stout and round bone medial to
the atlantal neural arch may be the odontoid process of the axis.
The right side of the axis is well exposed ( Fig. 4B). The axial centrum is laterally com鄄
pressed due to postmortem deformation and approximately as long as tall; it should have been
longer than high in life although not as elongate as in Anshunsaurus huangguoshuensis (Liu and
Rieppel, 2005) and Askeptosaurus italicus (M俟ller, 2005). The lateral and ventral surfaces of
the axial centrum are significantly concave. The longitudinal keel along the ventral midline
might be exaggerated by the strongly lateral compression of the centrum. The rib facet is slightly
damaged; it projects laterally and is positioned across the neural arch鄄central suture at the ante鄄
rior end of the centrum. The prezygapophysis and postzygapophysis are very large, the latter is
larger than the former. The prezygapophysis faces more dorsally than laterally, and it extends
slightly beyond the anterior edge of the centrum. The postzygapophysis faces ventrolaterally,
with its facet overhanging the posterior edge of the centrum. There is a prominent epipophysis
dorsal to the postzygapophysis. The neural spine is low and longitudinally broad, extending
more posteriorly than the postzygapophysis. It is higher posteriorly than anteriorly, in contrast
with the straight in the species of Anshunsaurus (Liu and Rieppel, 2005; Liu, 2007) or convex
dorsal margin in Askeptosaurus italicus.
In the post鄄axial cervical vertebrae, the centrum is relatively longer, the neural spine is
significantly taller, and the prezygapophysis is more massive than those of the axis (Fig. 4B,
C) , as in other thalattosaurians. The ventral surface of the centrum is covered with the ribs in
those cervicals. The prezygapophysis faces dorsomedially and extends well over the anterior
edge of the centrum. The postzygapophysis extends beyond the posterior edge of the centrum but
to a lesser degree than in the axis. The epipophyses become smaller in the posterior cervicals
and entirely disappear in the eighth cervical. The concave lateral surface of the centrum is fur鄄
ther depressed, which is less so in the last two cervicals. The diapophyses become more pro鄄
nounced in the posterior cervicals, and those of the last (13th ) cervical are nearly as large as
those of the first dorsal. The parapophyses move dorsally in the posterior cervicals, close to the
diapophysis in the last cervical. The neural spine, complete only in cervicals 4 and 6, is
square鄄like in the first four post鄄axial cervicals. The neural spine of the cervical 7 is complete,
1期 吴肖春等:短吻贫齿龙(双孔亚纲:海龙目):头后骨骼及系统关系研究 7摇摇摇摇
Fig. 4摇 Some vertebrae of Miodentosaurus brevis Cheng et al., 2007 in lateral views
A- C. cervical vertebrae; D. the last cervical and the first two dorsal vertebrae (vertebrae 13 to 15);
E. dorsal vertebrae 12 to 14 ( vertebrae 25 to 27)
Abbreviations as in Fig. 1 plus atch. atlantal neural arch 环椎神经弓; atsp. atlantal neural spine 环椎神经
棘; cl. clavicle 锁骨; dip. diapophysis 椎弓横突; d14. the 14th dorsal vertebra 第十四背椎; dr. dorsal
rib 背肋; epip. epipophysis 后关节上突; fdi. rib facet for diapophysis 肋骨关节椎弓横突的面; fpa. rib
facet for parapophysis 肋骨关节椎体横突的面; icl. interclavicle 间锁骨; mip. middle process of cervical
rib 颈肋中央突; pap. parapophysis 椎体横突; poz. postzygapophysis 后关节突; prz. prezygapophysis 前
关节突; trp. transverse process 横突; v. vertebra 椎体
with a dorsal edge projecting further posteriorly than in the first four post鄄axial cervicals. The
neural spine is reconstructed for those posterior to the 7th and it in the last cervical may have
been as tall as that of the first dorsal.
The 14t h vertebra is considered as the 1st dorsal on the basis of the size of the diapophysis,
which is similar to that of the 15 th , obviously larger than the cervical vertebrae (Fig. 4D). In
comparison with the cervicals, the 25 dorsal vertebrae differs in that the centrum is longer, the
8摇摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
neural spine is much taller (compared with that of the 7th cervical), and the lateral surface of
the centrum is less depressed. The diapophysis and parapophysis are merged into a single trans鄄
verse process in all dorsals but the first dorsal in which the parapophysis is still separated from
the diapophysis as a distinct process, as indicated by the presence of the ventral head of the 1st
dorsal rib. The parapophysis is represented by a small facet facing dorsomedially in the trans鄄
verse process in the other dorsals (Fig. 4D). The centrum is relatively shorter in the anterior
few and the posterior most dorsals. The neural spines (partly seen in the first four or five dor鄄
sals but not exposed in the last two dorsals because of the overlapping of the girdle elements)
are strongly constructed around the ventral portion. This situation is also seen in the anterior
dorsals of the species of Anshunsaurus (see fig. 5 in Liu and Rieppel, 2005 or fig. 1 in Liu,
2007) although the spine is relatively taller than in Miodentosaurus. The ventral surface of all
dorsal vertebrae is smooth and lacks any ridges.
The two sacral vertebrae are characterized by the large facet for the sacral rib and the cen鄄
trum longer than in the last two dorsals (Fig. 5A) . The facet of the 1st sacral is taller than long,
and expands nearly to the anterior edge of the centrum, whereas the facet of the 2nd is much lar鄄
ger than that of the 1st , longer than tall, and expands nearly to the posterior edge of the cen鄄
trum. The morphology and location of the sacral rib facet in the 2 nd sacral vertebra contrasts with
those in Endennasaurus acutirostris in which the facet is nearly round in outline and positioned
near the mid鄄point of the centrum ( see fig. 3C in M俟ller et al., 2005; fig. 3C in Renesto,
1992) . The lateral surface of the centrum is significantly concave and the ventral surface is
smooth. The sacral neural spine is as tall as those in the dorsals, but the constriction at the
base is weak and the spine is relatively taller than in E. acutirostris and Anshunsaurus huangguo鄄
shuensis (see fig. 6 in Liu and Rieppel, 2005) .
The first two caudals are longer and slightly taller than the sacral vertebrae (Fig. 5B ).
Their neural spine is nearly vertical and relatively taller than in other askeptosauroids such as
Anshunsaurus and Askeptosaurus, and lacks the basal constriction seen in the most dorsals. The
rib facet is located close to the ventral edge of the centrum as in other thalattosaurians. There
are no chevron facets along the posteroventral edge of the centrum in the first two caudals. Cau鄄
dal vertebrae 3- 5 are not preserved. The 6th caudal differs from the first two in the following
features. The neural spine is posterodorsally directed, which is more so in the further posterior
caudals; the distal end of the neural spine is narrower than the base (Fig. 5C); and there are a
pair of chevron facets on the posteroventral side of the centrum. The rib facets become smaller
in posterior caudals and entirely disappear in the 10th caudal. It is clear that the caudal rib is
sutured but not fused to the transverse process until the 7 th caudal.
Cervical ribs are nearly complete except for the first four cervicals in which the ribs are in鄄
complete or covered with the vertebrae. The posterior portion of the 1st rib is rod鄄like ( Fig.
4A). The rest of cervical ribs are similar to those of other thalattosaurians in having two heads
and a process: a massive dorsal head for the diapophysis, a slender ventral head for the para鄄
pophysis, and a short middle process between the two ( Fig. 4C,D) . The middle process is
small and not as pronounced as in many archosaurs (such as a crocodylian Stangerochampsa (Wu
et al., 1996)). It slightly projects anterolaterally beyond the union of the dorsal and ventral
heads in the anterior cervicals, but it is more posteriorly located in the posterior cervical ribs.
The rib shaft gradually elongates in the posterior cervical region. The last cervical rib is only
partly exposed, and transition to the dorsal rib is unclear. The dorsal and ventral heads become
closer in position while their middle processes become smaller in the posterior cervical ribs.
Most dorsal ribs are complete and exposed in right lateral view (Figs. 3, 6, 7A,B). The
proximal head of the first three ribs is covered by the pectoral girdles, except for the first rib
which has a small ventral head for the parapophysis of the centrum as in the cervical ribs (Fig.
1期 吴肖春等:短吻贫齿龙(双孔亚纲:海龙目):头后骨骼及系统关系研究 9摇摇摇摇
Fig. 5摇 Sacral and anterior caudal vertebrae of Miodentosaurus brevis Cheng et al., 2007 in lateral views
A. sacral vertebrae and ribs; B. the 1 st and 2nd caudal vertebrae; C. the 8th to 10th caudal vertebrae
Abbreviations as in Fig. 4 plus ca. caudal vertebra 尾椎; is. ischium 坐骨; sa. sacral vertebrae 荐椎;
sr. sacral rib 荐肋
4D) . The dorsal ribs are strongly arched in life, with an expanded proximal head, a rod鄄like
shaft, a slightly broadened distal end, and a shallow groove along the proximal half of the late鄄
ral surface (Fig. 4E) . In a number of the dorsal ribs, the distal end is flattened during fossiliza鄄
tion. The most evident differences among the dorsal ribs are that the proximal head is broader
and the lateral grove is deeper in the anterior ribs than in the posterior ones.
The two sacral ribs are very distinctive, significantly shorter and much more massive than
any dorsal one ( Fig. 5A). The first sacral rib is comparable to that of Anshunsaurus huangguo鄄
shuensis in having a dorsoventrally broadened head and a horizontally broadened distal end, al鄄
though the distal end is narrower ( see fig. 6 in Liu and Rieppel, 2005) . The second sacral rib
is more massive than the 1st and its two broadened ends are situated in the same horizontal
plane, as in Anshunsaurus but not Endennasaurus in which the distal end of the second sacral
rib is thinner than the 1st( see fig. 3 in M俟ller et al., 2005). The distal end of the 2nd rib is
wider than the head as in many other thalattosaurians but Askeptosaurus in which the distal end
is much broader than (about three times as wide as) the head ( see fig. 8E in M俟ller, 2005).
10摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
Fig. 6摇 Pectoral girdle, forelimbs, and gastralia of Miodentosaurus brevis Cheng et al., 2007
A.elements of the pectoral girdles in outer view and the right humerus in ventral view; B. the left humerus, radius,
and ulna in ventral view; C. the radius, ulna, and manus of the left forelimb in ventral view; D. elements of gastralia
Abbreviations as in Fig. 4 plus cg. central element of gastralia 腹肋中央段; cla. claw ( ungual ) 爪; cn.
centrale 中央腕骨; cof. coracoid facet on scapula 肩胛骨上乌喙骨关节面; cog. glenoid on coracoid 乌喙
骨的肩臼部; dc. distal carpal 远侧腕骨; dpc. deltopectoral crest 三角肌—胸大肌嵴; emc. embayment on
coracoid 乌喙骨凹弯; eng. entepicondylar groove 内髁沟; fcl. facet for clavicle 关节锁骨的面; fco. fora鄄
men on coracoid 乌喙孔; ficl. facet for interclavicle 关节间锁骨的面; in. intermedium 中间腕骨; lcl. left
clavicle 左锁骨; lco. left coracoid 左乌喙骨; lg. lateral element of gastralia 腹肋外侧段; lh. left humerus
左肱骨; lra. left radius 左桡骨; lsc. left scapula 左肩胛骨; lul. left ulna 左尺骨; picl. anterior process
of interclavicle 间锁骨前突; rcl. right clavicle 右锁骨; rco. right coracoid 右乌喙骨; rh. right humerus
右肱骨; rra. right radius 右桡骨; rsc. right scapula 右肩胛骨; rul. right ulna 右尺骨; scg. glenoid on
scapula 肩胛骨的肩臼部; uln. ulnare 尺骨; I, II, V. the 1s t , 3rd , 5 th metacarpals / metatarsals 第一,二和
五掌骨及第一,三和五跖骨; 1 - 5. the 1 st to 5th digits of manus / foot 第一到第五指/趾
1期 吴肖春等:短吻贫齿龙(双孔亚纲:海龙目):头后骨骼及系统关系研究 11摇摇摇
Fig. 7摇 Pelvic girdle and hindlimbs of Miodentosaurus brevis Cheng et al., 2007
A. right pelvic girdle in outer view and right humerus in ventral view; B. left pelvic girdle in dorsal view;
C. right tibia, fibula, and foot elements in ventral view
Abbreviations as in Figs. 5 and 6 plus act. acetabulum 髋臼; adm. anterodorsal margin 前背缘; anm. an鄄
terior margin 前缘; bmdo. opening between the pubic symphysis and ischial symphysis 耻骨联合和坐骨联
合间孔; car. caudal rib 尾肋; dta. distal tarsal 远侧跗骨; fil. facet for ilium 关节肠骨的面; fis. facet for
ischium 关节坐骨的面; fpu. facet for pubis 关节耻骨的面; intr. internal trochanter 小转子; lf. left femur
左股骨; lil. left ilium 左肠骨; lis. left ischium 左坐骨; lpu. left pubis 左耻骨; mem. medial margin 内
缘; otf. obturator foramen 闭 孔; pdm. posterodorsal margin 后背缘; pom. posterior margin 后缘; ppi.
posterior process of ischium 坐骨后突; rf. right femur 右股骨; rfi. right fibula 右腓骨; ril. right ilium 右
肠骨; ris. right ischium 右坐骨; rpu. right pubis 右耻骨; rti. right tibia 右胫骨
12摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
There are only five right caudal ribs preserved, of which the 3rd is complete ( Fig. 7B ) .
The complete caudal rib is very short and has a slightly broadened head and somewhat pointed
distal end. The rib facets suggest there are 9 caudal ribs, of which the first three are separated
from the transverse process on the ventrolateral side of the centrum. The size of the transverse
process indicates that the ribs become shorter posteriorly and eventually fused with the small
transverse process.
Chevrons (haemal arches) are scattered around the mid鄄portion of the tail but more than
25 of them are fairly preserved ( Fig. 3). The chevrons are Y鄄shaped, with an articular facet
on each side facing dorsomedially, as in most other thalattosaurians. The forked portion in the
complete chevrons is shorter than the distal portion, similar to the condition seen in Anshunsau鄄
rus huangguoshuensis, but the forked portion is U鄄shaped rather than V鄄shaped in the latter
(see those around the 13th caudal vertebrae in IVPP V 11834). In an indeterminate thalattosau鄄
rian ( = thalattosauriform) from the Upper Triassic of Austria ( M俟ller, 2007), the forked
proximal portion is much shorter ( less than half) than the distal portion (see fig. 1 in M俟ller,
2007) . Three chevrons are illustrated for Askeptosaurus italicus, showing that the forked proxi鄄
mal portion is U鄄shaped and much longer (about twice) than the distal portion if these three are
complete (see fig. 8F in M俟ller, 2005).
Many gastralia are well preserved although not in original arrangement (Fig. 3). Each row
of the gastralia may have consisted of three elements, one medial and two laterals. The proximal
end of the medial element curves forward and meets the counterpart from the opposite side along
the midline (Fig. 6D). Distally, the medial element has a long articular facet on the anterior
side for receiving a lateral element. The latter is spindle鄄shaped but very narrow, with its proxi鄄
mal portion more pointed than its distal portion. The exact number of gastralia rows is unknown
owing to the postmortem displacement.
Pectoral girdle摇 All elements of the pectoral girdle are well鄄exposed except for the scapula
(Figs. 3, 6A). The right scapula is almost entirely covered by the coracoid and the left is
nearly vertical in orientation and its distal expansion is obscured. The articular facet for the cor鄄
acoid is triangular in outline, and the posterior portion close to the glenoid is much broader than
the anterior portion. The scapula has a broad dorsal plate, with a concave posterior edge and a
convex anterior edge, probably similar to that of Askeptosaurus italicus.
The coracoid is oval and the overall morphology is similar to that of Anshunsaurus huangguo鄄
shuensis,Askeptosaurus italicus, and Endennasaurus acutirostris. It has a long and straight me鄄
dial edge to articulate with the interclavicle. The scapular facet appears to be wider and the cor鄄
acoid foramen is more posteriorly positioned than in the aforementioned taxa. There is a small
embayment just posterior to the glenoid, which is absent in other askeptosauroids such as the
aforementioned three taxa. The dorsal surface of the coracoid is not observable.
The interclavicle is nearly complete and well鄄exposed, and the outline is similar to that of
Anshunsaurus huangguoshuensis ( see fig. 9 in Liu and Rieppel, 2005 ) and Endennasaurus
acutirostris (see fig. 4 in M俟ller et al., 2005 ). It characterized by a small anterior process
(unknown in E. acutirostris) and very elongate posterior shaft (Fig. 6A). The lateral process is
missing the distal tip on the left side, but it is suggested to be similar to that of the above two
taxa in life. The posterior portion of the shaft is much narrower than the anterior portion, in
contrast to the situation seen in A. huangguoshuensis,E. acutirostris and Askeptosaurus italicus.
In anterior view, the facet for the clavicle is a deep groove that widens dorsoventrally; the small
anterior process is the septum between the grooves from each side.
The right clavicle is well鄄preserved in posteromedial view, with its distal tip covered with
the right coracoid and the proximal portion with the left clavicle ( Fig. 6A) . It is roughly L鄄
shaped, as in Anshunsaurus huangguoshuensis, with a thickened transverse (proximal) portion
inserting into the groove鄄like facet on the interclavicle and a slender vertical ( distal) portion
1期 吴肖春等:短吻贫齿龙(双孔亚纲:海龙目):头后骨骼及系统关系研究 13摇摇摇
meeting the scapula. The anterolateral margin is thin whereas the posteromedial margin is
thick. The posteroventral surface is smooth and concave and the anterodorsal surface is not ex鄄
posed.
Pelvic girdle摇 The elements of the pelvic girdle are preserved in outer view on the right
side and in inner view on the left side (Fig. 7A,B). The ilium bears a nearly straight dorsal
blade with a slightly broadened distal tip, unlike the ilia in Askeptosaurus italicus, and Enden鄄
nasaurus acutirostris in which the dorsal blade is more strongly curved posteriorly and distally
narrowed (see fig. 10 in M俟ller, 2005; fig. 6 in M俟ller et al., 2005). In Anshunsaurus huang鄄
guoshuensis, the shaft of the dorsal blade is also curved and distally not broadened (see fig. 6 in
Liu and Rieppel, 2005). The dorsal blade of Hescheleria ruebeli is also distally broadened but
has a pointed tip (see fig. 8m in Rieppel, 1987). As in other askeptosauroids, the ventral por鄄
tion of the ilium is much broader than the dorsal blade; the iliac acetabulum is very broad and
concave, the facet for the pubis is wider than that for the ischium, and the medial surface is
convex. The articular facets for the two sacral ribs are still covered by the matrix.
The pubes are nearly complete (Fig. 7A,B). As a whole, the pubis resembles that of An鄄
shunsaurus huangguoshuensis(see fig. 10 in Liu and Rieppel, 2005). It is a polygonal plate as
in other thalattosaurians, with a curved anterior margin, a straight anterodorsal margin, and a
slightly bulged medial margin. The articular facet for the ischium is as large as that for the
ilium. The obturator foramen is located closer to the posterodorsal rather than the anterodorsal
margin. The ventral (outer) surface is convex and the dorsal (inner) surface is concave. The
pubic portion of the acetabulum is not well defined because of surface erosion.
The right ischium is nearly complete in ventral view. It is a plate鄄like bone that has a con鄄
cave posterodorsal, a slightly concave posteroventral, and a convex medial margin (Fig. 7A).
The posteriorly directed process between the posterodorsal and posteroventral margins is not as
sharply pointed as in most other thalattosaurians such as Anshunsaurus huangguoshuensis( see
fig. 10 in Liu and Rieppel, 2005), Askeptosaurus italicus( see fig . 10 in M俟ller, 2005 ) , and
Endennasaurus acutirostris (see fig. 8A in Renesto, 1992) . The anteromedial margin is convex
(but not complete) , which certainly indicates that there was a median opening between the pu鄄
bic symphysis and ischial symphysis in life. There is no evidence to suggest an opening or fora鄄
men present between the pubis and ischium, which is seen in E. acutirostris ( see fig. 6 in
M俟ller et al., 2005) .
Forelimbs摇 Both forelimbs, except for the left zeugopodium and manus, are preserved in
ventral (posterior) view although disarticulated (Figs. 3, 6A- C). Most of the limb elements
are measurable (Table 1) although they were flattened during fossilization. The humerus is a
massive bone with a slightly broadened head, a thick shaft, and an expanded distal end (Fig.
6A,B). The expansion of the distal end is certainly exaggerated by dorsoventral compression,
which is indicated by the difference in the width of two humeri. As in the species of Anshunsau鄄
rus, the proximal head does not form a pronounced articular prominence seen in Endennasaurus
acutirostris (see fig. 5A in M俟ller et al., 2005 (the humerus should be the left one rather than
the right)). The humerus is relatively short and stout in comparison with that of other askep鄄
tosauroids such as E. acutirostris and Askeptosaurus italicus. In ventral ( posterior ) view, the
deltopectoral crest is weakly developed when compared with that of Anshunsaurus huangguo鄄
shuensis (see fig. 9 in Liu and Rieppel, 2005). The ectepicondyle and entepicondyle are not
well鄄developed. There is an entepicondylar groove along the distomedial margin of the shaft.
The concavity of the ventral surface of the distal portion is exaggerated during preservation.
The right radius is complete and well鄄exposed. As in Anshunsaurus huangguoshuensis (but
see A. wushaensis ( see the type specimen, IVPP V 13782 or the juvenile in fig. 5 in Liu,
2007) ) , the distal end is slightly broader than the proximal end (Fig. 6B). The outer edge of
the radius is nearly straight and the ulnar edge is concave. The concavity on the ventral surface
14摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
of the bone is exaggerated during fossilization. The proximal articular surface is flat whereas the
distal articular surface is convex.
摇 摇 摇 摇 摇 摇 摇 摇 Table 1摇 Measurements of selected elements of Miodentosaurus摇摇摇摇摇(mm)摇
Axis C6 C9 D2 D12 S2 Ca2
Length of centrum 30. 3 35. 8 35. 5 38. 8 38. 1 36. 1 43摇
Height of whole vertebra 49摇 32 . 5 34. 2 35. 5 32. 5 32 . 9 37. 5
Height of centrum — 74. 5 82. 4 85. 8 109摇 摇 106. 9 摇 108. 6 摇
Maximal width of spine 46摇 18 . 7 22. 2 30 摇 34. 5 19 . 5 22. 5
Hu Ra Ul Fe Fi Ti
Length ( R) 186 114 87 210 . 6 96. 2 *94. 5 *
(L) 188 摇 103*105 — — —
Proximal width ( R) 摇 62. 5 36 — 49. 2 28 . 5 50. 5
(L) 摇 61. 9 37 33 — — —
Distal width (R) 摇 摇 68. 8 #摇 45. 5 摇 36 . 8 80. 4 — —
(L) 86 摇 47. 2 36 — — —
MCI MCII MC芋 MCIV MCV MTI MTII MT芋 MTIV MTV
Length / R 47 59 . 4 60 61. 5 52. 5 56. 4 68. 7 72. 5 — 63
摇 * preserved length; # exposed width.
The right ulna is entirely exposed although its proximal end is incomplete. The complete
left ulna is extensively covered with the gastralia (Fig. 6B,C). Both ends of the ulna are simi鄄
larly expanded, but the proximal end is incomplete or partly covered (see Table 1 for measure鄄
ments). The shaft is nearly symmetrically constricted as in Anshunsaurus huangguoshuensis.
The radial side of the ulna is more curved than the outer side in Askeptosaurus italicus and En鄄
dennasaurus acutirostris. The concave ventral surface of the bone is exaggerated by the dorso鄄
ventral compression.
The manus is disarticulated but many of its elements are preserved. The ulnare is nearly
round and has a concave ventral surface. The intermedium is roughly rectangular in outline and
has a concave dorsomedial side. The centrale is asymmetrically pentagonal in shape ( Fig.
6C). The four distal carpals and five metacarpals are closely associated. Distal carpal 2 is the
smallest and the hexagonal distal carpal 4 is the largest. Distal carpal 1 is smaller than distal
carpal 3 as in Anshunsaurus huangguoshuensis but the opposite is true in Askeptosaurus italicus
and Endennasaurus acutirostris.
As in some other askeptosauroids, metacarpal I is the shortest but most massive among the
five elements, with a proximal end much broader than the distal end (Fig. 6C). It is relatively
slender in Endennasaurus acutirostris (see fig. 5 in M俟ller et al., 2005). Metacarpals 域, 芋,
and 郁 are of approximately same length ( 59. 4, 60, and 61. 5 mm, respectively) , which is
comparable with those in the species of Anshunsaurus. Metacarpal V is longer than metacarpal
I, whereas the opposite is the case for E. acutirostris and Clarazia schinzi (see frig. 5 in Riep鄄
pel, 1987).
The first phalanx is closely associated with the corresponding metacarpal in each digit
(Fig. 6C). There is a phalanx close to the first of digit 1, which does not belong to this digit;
it is in the opposite direction, suggesting that it may have been displaced from a different digit.
In this case, it is most likely that digit 1 had two phalanges including the terminal claw ( un鄄
gual), as in other thalattosaurians. There are number of phalanges scattered around but it is
difficult to determine their original location; thus, the phalange formula of the forelimb cannot
be established.
Hindlimbs摇 The right hindlimb is more complete than the left (Fig. 3) . The right femur
1期 吴肖春等:短吻贫齿龙(双孔亚纲:海龙目):头后骨骼及系统关系研究 15摇摇摇
is exposed in ventral view, and longer ( about 112% ) than the humerus. The head is slightly
damaged but shows no evident expansion (Fig. 7A). The distal end is complete and expanded.
The posterior edge of the femoral shaft is nearly straight but the anterior (medial) edge is con鄄
cave. The internal trochanter is well鄄developed, located at the proximomedial (anterior) edge
near the articular head as in Anshunsaurus huangguoshuensis ( IVPP V 11834 , see Liu and
Rieppel, 2005:23). The fourth trochanter seen in Endennasaurus acutirostris ( see fig. 7 in
M俟ller et al., 2005) is not evident here. The shaft is flat but it is exaggerated by dorsoventral
compression during preservation. There is a depression on the proximoventral surface, and it
may have been enhanced by compression. The distovental surface of the femur is slightly con鄄
vex, and the distal end has a narrow condyle with which the fibula articulates.
The right tibia is nearly complete but it was superficially damaged in its distodorsal portion
(Fig. 7C). As in the species of Anshunsaurus, the proximal end is much wider than the distal
end. The inner (fibular) margin of the shaft is concave but the outer margin is nearly straight,
as in other thalattosaurians.
The right fibula is preserved in ventral view but the proximal and distal ends are damaged
(Fig. 7C). It should have been posterolateral to the tibia in life, but it is now located antero鄄
medial to the tibia due to the postmortem displacement. The distal end is wider than the proxi鄄
mal end, as in other thalattosaurians. The constriction of the fibular shaft is nearly symmetrical.
All tarsals are missing except for one which is identified as distal tarsal 5 ( Fig. 7C). The
surface is damaged but the round outline remains.
Metatarsals 玉- 芋 and V are preserved. The latter three were displaced from the postero鄄
lateral side to the anteromedial side (Fig. 7C), possibly along with the displaced fibula men鄄
tioned above. Metatarsal I is the shortest but most massive among the four. It resembles that of
Anshunsaurus species and Askeptosaurus italicus in that its outer side is shorter and more in鄄
curved than its inner side and its proximal end is much more expanded than its distal end. Meta鄄
tarsals 域 and 芋 are morphologically similar to each other although the latter is slightly longer
than the former. Their shaft does not constrict as much as in the aforementioned two taxa and
Endennasaurus acutirostris (see fig. 11 in Renesto, 1992). As in other thalattosaurians, meta鄄
tarsal V is more massive but shorter than metatarsals 域 and 芋. Its proximal surface for the ar鄄
ticulation with the fifth distal tarsal is oblique internally as in E. acutirostris.
There are 16 phalanges including five claws (Fig. 7C). The first phalanges of digits 2, 3,
and 5 are identified on the basis of their close association to the corresponding metatarsal. The
others are scattered around, and the foot phalangeal formula is unknown.
3摇 Revised diagnosis of Miodentosaurus brevis Cheng et al., 2007
Cheng et al. (2007) provided a set of diagnostic characters of Miodentosaurus brevis based
on the study of the skull and mandible. Comparison of the postcranial anatomy reveals that sev鄄
eral postcranial features are not common for the Thalattosauria and considered as extra diagnos鄄
tic characters of M. brevis. The most striking of those characters come from the girdle elements,
including the coracoid, interclavicle, ilium, and ischium. In addition, the morphology of the
frontal, parietal, and surangular clarified here is also distinctive within the Thalattosauria.
Therefore, the diagnosis of M. brevis is revised as: 1) straight snout very short, nearly as short
as post鄄snout region (from anterior edge of orbit to posterior edge of skull table); 2) presence
of crest along anterior third of dorsal midline of premaxillae; 3) premaxilla having six conical
teeth; 4) maxilla edentulous; 5) frontal forming anterior border of pineal foramen; 6) parietal
possessing slender anterolateral process to wrap posterolateral process of frontal; 7) dentary
having no more than six conical teeth implanted in rostral portion; 8) surangular suddenly
broadens ventrally at posterior third of its length; 9) coracoid possessing small embayment just
16摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
posterior to glenoid; 10) interclavicle becoming much narrower distally than proximally; and
(11) iliac blade with expanded distal end.
4摇 Phylogenetic relationships
Recently, a number of phylogenetic analyses of the Thalattosauria have been published
(Nicholls, 1999; Liu and Rieppel, 2001, 2005; Jiang et al., 2004; M俟ller, 2005, 2007;
M俟ller et al., 2005; also see Appendix 1). With a number of new thalattosaurians newly dis鄄
covered from China, most recent analyses have suggested that the Thalattosauria consists of two
major groups, the Thalattosauroidea and Askeptosauroidea ( Liu and Rieppel, 2005; M俟ller,
2005, 2007). In the study of the cranial morphology, Cheng et al. (2007) mentioned that the
features of the snout and palate suggest a close relationship of Miodentosaurus with askeptosau鄄
roids although no detailed phylogenetic analysis was carried out because the postcranial skeleton
was not available for the study then. The phylogenetic relationships of Miodentosaurus are estab鄄
lished here on the basis of a cladistic analysis that employs the data matrix derived from the
studies of M俟ller (2007) . The new data matrix ( Appendixes 2,3 ) consists of 42 characters
and 15 taxa including Miodentosaurus and Anshunsaurus wushaensis Rieppel et al., 2006. The
definition of the characters are not modified at all from those of M俟ller (2007) except for char鄄
acter 29, which is now redefined as a tri鄄state character: cervical vertebrae < 10 (0), > 10
(1), or 逸 15 (2). The analysis (using the branch鄄and鄄bound search option of PAUP*4. 0b
10 (Swofford, 2002), all characters unordered, multiple character states treated as polymor鄄
phism) produces three shortest trees, with a tree length of 72, CI of 0. 625, and RI of 0. 738.
In all three trees, the included thalattosaurians form two monophyletic groups, the Askeptosau鄄
roidea and Thalattosauroidea (Fig. 8A), as in Liu and Rieppel ( 2005) and M俟ller ( 2005,
2007) . The monophyly of the Askeptosauroidea is unequivocally supported by five synapomor鄄
phies, characters 11, 12, 19, 27, and 29 while the monophyly of the Thalattosauroidea is sup鄄
ported by six unequivocal synapomorphies ( characters 2, 4, 17, 30, 35, and 37 ) and four
equivocal characters (5, 21, 33, and 36) from ACCTRAN character optimization. Miodentosau鄄
rus and Anshunsaurus wushaensis are unequivocally grouped within the clade Askeptosauroidea.
Within this clade, a monophyletic Askeptosauridae including Anshunsaurus,Miodentosaurus,
and Askeptosaurus is supported as in Liu and Rieppel (2005) and M俟ller (2005, 2007) . An鄄
shunsaurus wushaensis is the sister group of A. huangguoshuensis, supporting the study of Riep鄄
pel et al. ( 2006), and Miodentosaurus has a closer relationship to Askeptosaurus than to An鄄
shunsaurus. The close relationship between Miodentosaurus and Askeptosaurus is unambiguously
supported by two synapomorphies, i. e., character states 28 ( presence of a small retroarticular
process, wider than long (a reversal)) and 38 (a reduced deltopectoral crest). The close rela鄄
tionship of the two species of Anshunsaurus is supported by state 2 of character 29 ( there are
more than 15 cervical vertebrae). Our result was exactly same as the analyses of M俟ller (2005,
2007) , in terms of the branching pattern of the Thalattosauroidea ( his Thalattosauria) . As in
previous analyses, the bootstrap support is not very strong for many clades ( Fig. 8B) , much
weaker than in M俟ller爷 s analyses (2005, 2007) . With the addition of M. brevis and A. wusha鄄
ensis, the monophyly of the Thalattosauroidea has a strong support in 100 bootstrap replicates
(84% ) , although it is not the case for the clades within this group. The bootstrap support for
the monophyly of the Askeptosauridae is lower than 50% , while the support for the monophyly
of the Askeptosauroidea is only 53% . There are two taxa ( K觟ssen鄄Form and Agkistrognathus)
that have only 4 or 5 characters out of the 42 are scored. This may have affected the results of
the analyses, but the tree ( s ) from an analysis without these two taxa is / are also poorly re鄄
solved. This may indicate that the members of the Askeptosauroidea might not be so closely re鄄
lated with one another.
1期 吴肖春等:短吻贫齿龙(双孔亚纲:海龙目):头后骨骼及系统关系研究 17摇摇摇
Fig. 8摇 Cladograms showing phylogenetic relationships of Miodentosaurus brevis Cheng et al., 2007
A. strict consensus of three shortest trees, with tree length of 72, CI of 0. 625, and RI of 0. 735; B. boot鄄
strap 50% majority鄄rule consensus tree, with bootstrap values > 50% indicated; numbers blocked indicate
decay index
Acknowledgements摇 We thank Dr. Jun Liu and Mr. Chun Li of the IVPP (Institute of Verte鄄
brate Paleontology and Paleoanthropology, Beijing) for their help during the course of the work.
Ms. Mei鄄li Yang provided office assistances during Wu爷 s visit to the NMNS, Taichung, and
Ms. Marisa Gilbert of Canadian Museum of Nature (CMN) did the initial phylogenetic analysis
18摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
and offered her assistance in graphic work. We appreciate Paleowonder Fossil and Mineral Mu鄄
seum in Taipei for the skillful preparation of the specimen and various assistances given during
the study. The comments and suggestions of the two reviewers are very helpful and need to be
acknowledged. X. 鄄c. Wu and T. Sato are grateful to the NMNS for supporting their stay when
visiting the NMNS. This work was supported by the research grants from the NMNS and National
Science Council of Taiwan, China (NSC 95- 2116- M-178- 001) to Y. 鄄n. Cheng;the CAS/
SAFEA International Partnership Program for Creative Research Teams and the CMN (RS34) to
X. 鄄c. Wu; KAKENHI (18. 6288) and Tokyo Gakugei University to T. Sato.
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Appendix 1摇 Specimens and literatures for the character鄄state data matrix
Araeoscelidia (Petrolacosaurus kansensis (Reisz, 1981))
Younginiformes (Y. capensis (Gow, 1975; Carroll, 1981 ))
Agkistrognathus campebelli ( Nicholls and Brinkman, 1993 )
Askeptosaurus italicus (Kuhn鄄Schnyder, 1971; M俟ller, 2005)
Thalattosaurus (T. alexandrae ( Nicholls, 1999) , T. borealis (Nicholls, 1999; Rieppel et al. 2005))
Anshunsaurus huangguoshuensis (IVPP V 11834 and V 11835; Rieppel et al., 2000; Liu and Rieppel, 2005)
Anshunsaurus wushaensis (IVPP V 13782; Rieppel et al., 2006; Liu, 2007)
Clarazia schinzi (Rieppel, 1987 ; Rieppel et al., 2005)
Hescheleria ruebeli (Rieppel, 1987)
Xinpusaurus (X. bamaolinensis including X . kohi Jiang et al., 2004 ( Cheng, 2003 ; Jiang et al., 2004) and X. suni (IVPP
V 11860 and V 14372; Liu and Rieppel, 2001; Luo and Yu, 2002; Rieppel and Liu, 2006 ))
Nectosaurus halius (Nicholls, 1999; Rieppel et al., 2005 )
Paralonectes merriami ( Nicholls and Brinkman, 1993 )
Endennasaurus acutirostris (Renesto, 1992; M俟ller et al., 2005)
K觟ssen鄄Form ( M俟ller, 2007)
Miodentosaurus brevis (NMNS- 004742 / F003960; Cheng et al. 2007; this study)
Appendix 2摇 Characters for the phylogenetic analysis of Miodentosaurus ( derived from the data matrix of M俟ller
(2007), with the modification of character 29)
1. Rostrum: absent (0); present (1 ).
2. Rostrum morphology: straight (0) ; deflected ventrally (1) .
3. Rostrum profile: straight (0) ; premaxilla moderately turned downwards (1); premaxilla strongly turned downwards, its
alveolar margin positioned nearly vertical relative to the alveolar margin of the maxilla (2) .
4. Proportions of maxilla: at least twice as long as high (0) ; with truncated anterior end and narrow, vertically positioned
ascending process (1) .
5. Tooth implantation: subthecodont (0 ) ; thecodont (1 ) ; ankylothecodont (2 ); teeth superficially attached to the bone
(3).
6. Premaxilla dentition: present (0) ; absent (1)( State 1 includes also pseudodont projections).
7. Diastema between premaxillary and maxillary teeth: absent (0) ; present (1).
8. Anterior most dentary teeth: upright (0) ; procumbent as their implantation curves around anterior end of dentary (1) .
9. Posterior dentary and maxillary teeth: conical and pointed (0) ; bulbous and blunt (1) .
10. Pterygoid transverse flange dentition: present (0) ; absent (1) .
11. Pterygoid palatal ramus dentition: present (1); absent (1 ).
12. Vomerine dentition: present (0) ; absent (1 )
13. Nasals, medial contact: meet each other medially (0); separated because of the posterior extent of the premaxilla (1).
14. Nasals, posterior extent: do not (0), or do (1) extend backwards to level behind anterior margin of orbit. Character cod鄄
ing has been changed for Paralonectes (1).
15. Anterolateral processes of frontal: broadly separated from external naris (0); closely approach or even enter the posterior
margin of external naris (1) .
20摇摇摇 古摇脊摇椎摇动摇物摇学摇报47 卷
16. Anteromedial process of frontal: broadly separated from external naris (0); closely approaching external naris (1) .
17. Nasal鄄prefrontal contact: nasal in contact with prefrontal (0); nasal separated from prefrontal (1) .
18. Posterolateral processes of frontal: absent (0); present (1 ).
19. Posterolateral processes of frontal, posterior extent: not extending far beyond anterior margin of lower temporal fossa (0) ;
extending distinctly beyond anterior margin of lower temporal fossa (1) .
20. Frontal鄄supratemporal contact: frontal separate from supratemporal (0) ; frontal in contact with supratemporal (1) .
21. Posterolateral process of frontal constriction: constricted (0 ); broad ( 1) (i. e., fronto鄄parietal suture interdigitating, orien鄄
ted transversely for most of its part (0), or deeply embayed in the shape of a broad V with apex pointing forward (1) ).
22. Postfrontal and postorbital: separate (0) ; fused (1).
23. Upper temporal fenestra: present and large (0) ; absent or reduced and slit鄄like (1) .
24. Squamosal: with (0), or without (1) posteroventral process.
25. Quadrate: with (0), or without (1 ) distinct medial lamina.
26. Quadratojugal: present (0) ; absent (1 ).
27. Pineal foramen: small and located at center or somewhat behind of parietal skull table (0 ); large and located in front of
midpoint of parietal skull table (1) .
28. Retroarticular process: small or absent (0) ; present and distinct (1) .
29. Number of cervical vertebrae: < 10 (0 ); > 10 (1); 逸15 (2) ( modified).
30. Neural spine height of posterior cervicals and thoracals: relatively low (0) ; at least two times taller than broad (1).
31. Proximal caudal neural spine height: relatively low (0); distinctly elongated and at least three times taller than broad (1).
32. Cervical ribs: without (0), or with (1) anterior process.
33. Scapula: broad and rounded (0) ; slender and elongate (1) .
34. Humerus: long and slender (0) , or stout and short (1 ), relative to the trunk.
35. Radius: slender (0); expanded (1).
36. Radius expansion: only slightly expanded (0) ; strongly expanded and roughly kidney鄄shaped (1 ).
37. Fibula: slender (0); expanded (1).
38. Deltopectoral crest: well developed (0) ; reduced (1).
39. Fibula expansion: slightly expanded (0) ; broadly expanded mediolaterally (1) .
40. Snout elongation: distance from the anterior margin of the orbit to the anterior tip of the rostrum less (0 ) , or more (1 ),
than twice the distance from the anterior margin of the orbit to the posterior margin of the parietal skull table.
41. Tip of snout: lateral edges of snout terminating in a blunt tip (0) ; converging and terminating in a pointed tip (1).
42. Shape of snout: lateral edges of snout converging (0); parallel (1).
Appendix 3摇 Character鄄taxon matrix for the phylogenetic analysis of Miodentosaurus (derived from that of Muller
(2007) with the addition of Miodentosaurus and Anshunsaurus wushaensis)
Araeoscelidia 00?0000000 00000000?? 0000000000 00000?00?0 00
Younginiformes 00?0000000 0001000100 0000000000 00000?00?0 00
Askeptosaurus 10?0000001 11110110鄄鄄 0010111010 01010?01?1 01
Thalattosaurus 1100211111 0010101101 1111010??1 ?? 1111?0?1 10
Anshunsaurus鄄h 1000000001 1111000110 0110011120 0101000001 01
Anshunsaurus鄄w 100000000? ??1?0????? ?11? 011120 01? 1000000 01
Clarazia 1101301111 001010? 101 0111110100 0? 0? 101100 10
Hescheleria 1111301111 0? 1??????? ?11???? 101 0101101100 ??
Xinpusaurus 1101?000? 0 0010001100 111011?101 1?11111011 10
Nectosaurus ?11110??01 0010??110 ? 111?11?1?1 1? 1111?0?0 ??
Paralonectes 1111201111 0011?????? ???0?1? 1?? ?????????? ??
Agkistrognathus ????2? 100? ?0???????? ?????????? ?????????? ??
Endennasaurus 10?0?1???1 1110? 1011? 01??1??110 0000??00? 1 10
K觟ssen鄄Form ?????????? ?????????? ?????????? 1????11?1? ??
Miodentosaurus 100000- 0- 1 1111000110 0110011010 0101000100 01
摇摇Anshunsaurus鄄h =Anshunsaurus huangguoshuensis;Anshunsaurus鄄w =Anshunsaurus wushaensis; “ - 冶 = inapplicable,
which is treated as “?冶 in analyses.
