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Historical Biology An International Journal of Paleobiology

ISSN: 0891-2963 (Print) 1029-2381 (Online) Journal homepage: https://www.tandfonline.com/loi/ghbi20

A new of (Dinosauria: ) from the Middle of Yunyang, Chongqing, China

Chao Tan, Ming Xiao, Hui Dai, Xu-Feng Hu, Ning Li, Qing-Yu Ma, Zhao-Ying Wei, Hai-Dong Yu, Can Xiong, Guang-Zhao Peng, Shan Jiang, Xin-Xin Ren & Hai-Lu You

To cite this article: Chao Tan, Ming Xiao, Hui Dai, Xu-Feng Hu, Ning Li, Qing-Yu Ma, Zhao-Ying Wei, Hai-Dong Yu, Can Xiong, Guang-Zhao Peng, Shan Jiang, Xin-Xin Ren & Hai-Lu You (2020): A new species of Omeisaurus (Dinosauria: Sauropoda) from the of Yunyang, Chongqing, China, Historical Biology, DOI: 10.1080/08912963.2020.1743286 To link to this article: https://doi.org/10.1080/08912963.2020.1743286

Published online: 03 Apr 2020.

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Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=ghbi20 HISTORICAL BIOLOGY https://doi.org/10.1080/08912963.2020.1743286

A new species of Omeisaurus (Dinosauria: Sauropoda) from the Middle Jurassic of Yunyang, Chongqing, China Chao Tana,b, Ming Xiaoa,HuiDaia,Xu-FengHua,NingLia,Qing-YuMaa,Zhao-YingWeia,Hai-DongYua,CanXionga, Guang-Zhao Pengc, Shan Jiang c, Xin-Xin Rend,e,f and Hai-Lu You d,e,f aChongqing Laboratory of Geological Heritage Protection and Research, No. 208 Hydrogeological and Engineering Geological Team, Chongqing Bureau of Geological and Mineral Resource Exploration and Development, Chongqing, China; bInstitute of Sedimentary Geology, Chengdu University of Technology, Chengdu, China; cZigong Museum, , Sichuan, China; dKey Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China; eCAS Center for Excellence in Life and Paleoenvironment, Beijing, China; fCollege of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China

ABSTRACT ARTICLE HISTORY A new species of Omeisaurus, O. puxiani sp. nov., from the Middle Jurassic of Southwest China is reported. Received 11 February 2020 The holotype consists of partial articulated vertebrae, forelimb, hind limb and other materials of an Accepted 12 March 2020 Omeisaurus individual. Comparative study and cladistic analysis show that this new taxon belongs to , and KEYWORDS bears a unique combination of character states, such as all presacral vertebrae opisthocoelous, complex Pu’an; Chongqing; Shaximiao pneumatic fossa system in middle cervical centra, lateral fossae of dorsal centra divided by secondary septa, Formation; Middle Jurassic; end of anterior caudal neural spines expanding posteriorly, edge of humerus deltopectoral crest turning Sauropoda; Omeisaurus posterolaterally and ratio of length of ulna to humerus of 0.69. The previously reported single middle cervical (S66) from the same locality and horizon can be referred to this new species. The discovery of Omeisaurus puxiani enriches the diversity of the genus of Omeisaurus and provides additional information to help understanding the evolutionary history of this genus in Eastern China.

Abbreviations No. 208 HEGT: Chongqing Laboratory of Geological Heritage Protection and Research, No. 208 Hydrogeological and Engineering Geological Team, Chongqing Bureau of Geological and Mineral Resource Exploration and Development Chongqing, Chongqing, China; GSC: Chongqing Institute of Geological Survey, Chongqing, China; IVPP: Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China; ZDM: , Zigong, Sichuan, China

Introduction Among the abundant sauropod materials, a middle cervical verte- bra has been assigned to an undeterminated species of Omeisaurus Sauropod were the largest terrestrial once (Tan et al. 2018). Here we describe a partial articulated new saur- walked on our Earth. They appeared in Early Jurassic, and opod specimen from the same locality. Comparative study and achieved a global distribution throughout Middle Jurassic to cladistic analysis show that the new specimen is a member of Late (Weishampel et al. 2004). Sauropods had rela- Omeisaurus and different from other known species. Therefore, tively small skulls, extremely elongate necks and tails, as shown a new species of Omeisaurus, O. puxiani sp. nov., is established, in the early diverging clade of (Young and and the previously reported middle cervical vertebra (collection Chao 1972；Ouyang and Ye 2002; Russsell and Zheng 1993;He number (S66) (Tan et al. 2018)) can be assigned to this new species. et al. 1988; Suteethorn et al. 2012;Renetal.2018;Mannionetal. 2019). Mamenchisauridae is the most taxonomic diverse and specific abundant sauropod lineage in the Middle and Late Geological setting Jurassic in East Asian, especially in the Sichuan Basin in south- Geotectonically, Pu’an Town, Yunyang County, Chongqing western China, represented by from the upper Municipality is located in the southwest of the Yangzi Block (Gu member of Shaximiao Formation and Omeisaurus from the and Liu 1997). In this area, the red beds are well exposed, and the lower member of Shaximiao Formation (Young and Chao outcrops are generally continuous. The new taxon is yield from the 1972；Ouyang and Ye 2002; He et al. 1988). The first species of Shaximiao Formation. This Formation is divided into lower and Omeisaurus was discovered in the Zigong area of Sichuan Basin upper members (Stratigraphic table of Sichuan 1978, unpublished), by C. C. Young in 1939, and seven species have been reported which are generally equivalent to the Lower Shaximiao Formation until now, although the validity of some species are questionable and Upper Shaximiao Formation, respectively (Peng et al. 2005). (Young 1939, 1958;Dongetal.1983; He et al. 1988; Jiang et al. The age of the Shaximiao Formation was originally regarded as 2011;Fangetal.2004;Tanetal.2018). Middle Jurassic (Sha et al. 2010; Li et al. 2010; Li et al. 2018), but its In 2016, a new Middle Jurassic dinosaur quarry was discovered upper member could be Late Jurassic (Peng et al. 2005; Huang in Pu’an Town, Yunyang County, Chongqing Municipality (Fig. 1). 2018). The specimen in this study was recovered from the lower

CONTACT Hai-Lu You [email protected] Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China © 2020 Informa UK Limited, trading as Taylor & Francis Group

Published online 03 Apr 2020 2 C. TAN ET AL.

Figure 1. Geographic and geological maps showing the location of Omeisaurus puxiani sp. nov. (indicated by a dinosaur). The new specimen is from the lower Shaximiao Formation. to middle portion of the lower member of the Shaximiao (TBR) with 10 trees saved per replication. The resulting MPTs Formation. This horizon consists of purplish red muddy siltstone were then used as the starting trees for a Traditional Search using and silty mudstone interbedded with siltstone and mudstone. The TBR. All characters are equally weighted. specimen is generally articulated and distributed in a small area about 2 m by 7 m. Systematic palaeontology Method Dinosauria Owen 1842 Seeley 1887 Classification and Terminology Huene 1932 The topographic position of the cervical vertebrae was based in Sauropoda Marsh 1878 the relative position of the parapophysis and comparisons with Upchurch 1995 skeleton of louisae (Tschopp et al. 2015). The Omeisaurus Young 1939 nomenclature of laminae and fossae used in the vertebral ele- Omeisaurus puxiani sp. nov. ments are as follows: Wilson (1999; 2012)andWilsonetal. (2011). Holotype. CLGRP V00005 (Chongqing Laboratory of Geoheritage Protection and Research). Field number: 17YPmadao001. The holo- Phylogenetic analysis type is articulately preserved, and excavated in a same quarry. It Phylogenetic analysis was performed under TNT (ver. 1.5) preserves 10 middle to posterior cervicals (possibly cervicals 8–17), (Goloboff and Catalano 2016). The Traditional Search was applied 12 dorsals, partial sacrals, 24 caudals (10 anterior caudals, 10 middle first, setting 10,000 Maximum trees, applying a traditional search by caudals and 4 posterior caudals), fragments of ribs and chevrons, 1000 replicates of Wagner trees and tree bisection-reconnection partial clavicle, right forelimb (humerus, ulna, radius, two carpals, HISTORICAL BIOLOGY 3

Etymology. The specific name is after Samantabhadra (Pu Xian in Chinese, the Bodhisattva of Emei Mountain in the Sichuan Basin), ‘Pu’ in the specific name also indicates Pu’an, the holotype locality is a place attractive to virtue persons.

Locality and horizon Laojun Village, Pu’an Town, Yunyang County, Chongqing Municipality. Lower to middle portion of the lower member of the Shaximiao Formation.

Diagnosis Omeisaurus puxiani possesses the following unique combination of Figure 2. Representative elements of Omeisaurus puxiani sp. nov. in its skeleton character states (autapomorphies are marked by *): pleurocoels are reconstruction. well developed in cervical centra; the highest average elongation index value (EI) is beyond four (4.4 in cervical 9) among cervicals; lateral fossae of dorsal centra are divided by secondary septa; dorsal fi ve metacarpals and six phalanges), partial ilia, partial left and right neural spine ends are knob-shaped; neural spines of posterior fi femurs, partial right tibia and bula (Fig. 2; Tables 1 and 2). dorsals are transversely extended (other taxa of Omeisaurus are anteroposterior extended); caudal vertebrae are slightly

Table 1. Measurements of vertebrae of Omeisaurus puxiani sp. nov. An asterisk (*) and a plus (+) denote a measurement based on an incomplete element. All measurements are in millimetres. Vn CL CLB H ACH ACW PCH PCW NAH NSH NSL NSW Ca8 310+ ––––143 88* 61 67 235+ 23 Ca9 670 710 270 122 102* 152 108* 60 76 340 22 Ca10 240+ ––150 ––––––– Ca11 580+ ––––143 94* –––– Ca12 625 660 365 140* 92* 175 130 78 88 290 28 Ca13 600 645 320+ 160 106* 155 102 –––– Ca14 350+ ––145 92 200 87* –––– Ca15 180+ ––190 66 ––– – –– Ca16 310 370 ––140 129 215 –––– Ca17 235 285 ––205 100* 210 –––– D1 183 220 ––205 – 197 –––– D2 180 200+ – 185 – 175 –– – –– D3 180 200+ – 170 – 180 105 –––– D4 ––––––––124+ – 74 D5 ––––––––140 74 75 D6 155 165 500 160 –––90 195 50 58 D7 97* – 500 ––168 176 136 195 50 58 D8 155 165 500 170 95 180 120 120 175 45+ 46 D9 150 165 460 170 95 200 88 – 180 68 53 D10 ––––––––115+ 75* 60 D11 ––––––––110+ 80 65 D12 142 – 305 –– –––90± 85 62 Cd1 81+ – 475* –– –––162 80 – Cd2 87+ – 440 ––168 – 92 160 66 45 Cd3 96 – 440 ––175 – 90 155 61 53 Cd4 91 – 405 ––155 – 82 155 56 51 Cd5 91 – 390 ––150 – 72 145 48 43 Cd6 89 – 383 ––158 – 56 140 45 41 Cd7 88 – 365 ––150 – 63 133 52 42 Cd8 92 – 325 ––125+ – 58 128 80* 42 Cd9 ––280+ –– ––45 130 46 43 Cd10 ––––––––130 49 35 Cdm1 –––––––38 86 67 – Cdm2 112 – 219 ––97 – 35 76 63 – Cdm3 104 – 199 93 – 91 – 34 75 64 – Cdm4 102 – 195 92 – 92 – 35 66 56 – Cdm5 99 – 185 82 – 86 68 24 64 57 – Cdm6 70+ – 185 81 70 –––62 60 – Cdp1 97 – 141 68 60 62 – 25 ––– Cdp2 93 – 140 62 – 64 – 24 ––– Cdp3 91 – 127 61 – 57 – 22 ––– Cdp4 89 – 115 52+ – 58 – 22 ––– Abbreviations: Vn, vertebrate number; CL, centrum length (excluding ball); CLB, centrum length (including ball); H, height of vertebra; ACH, anterior centrum dorsoventral height; ACW, anterior centrum mediolateral width; PCH, posterior centrum dorsoventral height; PCW, posterior centrum mediolateral width; DFA, distance from anterior end of centrum to anterior margin of neural arch; DFP, distance from posterior end of centrum to posterior margin of neural arch; NAH, neural arch dorsoventral height (measured from dorsal margin of centrum up to the base of the postzygapophyses); NSH, neural spine dorsoventral height (measured from base of postzygapophyses up to neural spine summit); NSL, neural spine maximum anteroposterior length (measured above SPOLs); NSW, neural spine maximum mediolateral width; CCI, condylar convexity index (anteroposterior length of posterior condylar ball divided by mean radius of the condyle, i.e. mediolateral width + dorsoventral height of articular surface, divided by 4; Mannion et al., 2013); ca, cervical vertebra; d, dorsal vertebra; cd, caudal vertebra; cdm, middle caudal vertebra; cdp, posterior caudal vertebra. 4 C. TAN ET AL.

Figure 3. Cervical vertebrae of Omeisaurus puxiani sp. nov. (a) Ce 8-10; (b) drawing of Ce 8; (c) drawing of Ce 9; (d) Ce 11; (e) Ce 12; (f) Ce 13; (g) Ce 16; (H) Ce 17. A-F: left lateral; G: ventrolateral; H: ventral views, I: ventromedial view. Abbreviations: AP, anterior possess of rib; c, capitulum; CPRL, centroprezygapophyseal lamina; DI, diapophysis; pf, pneumatic fossa or foramen; NSP, neural spine; PA, parapophysis; PRZ, prezygapophysis; POZ, postzygapophysis; PODL, postzygodiapophyseal lamina; PPDL, paradiapophyseal lamina; PRDL, prezygodiapophyseal lamina; SPRL, spinoprezygapophyseal; t, tuberculum; VLR, ventrolateral ridge. Scale bars equal 10 cm.

fi Table 3. Revised scorings for Omeisaurus tianfuensis (O) and Mamenchisaurus amphicoelous; transverse process of the rst caudal extends dorso- youngi (M) in this study. ventrally; distal ends of anterior caudal neural spines expand pos- 148 159 170 214 220 236 teriorly (with a bifid extension)*; transverse processes of anterior ‘ ’ O0→10→12→10→10→1 caudals are wing-like ; edge of deltopectoral crest turns poster- M0→10→1 olaterally; ratio of length of ulna to humerus is relatively high (0.69). Description Axial skeleton Cervical vertebrae. Ten articulated cervical vertebrae are preserved Table 2. Measurements of metacarpals of Omeisaurus puxiani sp. nov. (Fig. 3). Most of them are intact with the left side exposed. These – Element L WA WP WM preserved cervicals are presumed to be Ce 8 17 according to Mc I 135 51 – 49 Omeisaurus tianfuensis which has 17 cervicals (He et al., 1988). Mc II 190 55 66 52 Furthermore, Ce 8–14 can be treated as middle cervicals, and Ce Mc III 185 68 55 40 15–17 as posterior cervicals based on their lengths (referred Mc IV 157 51 52 36 Tschopp et al. (2015), see Table 3 of that study). Mc V 150 47 67 40 Among the middle cervicals, cervicals 9, 11–13 are best pre- Ph I-1 50 50 – Ph I-2 136 70 – served and prepared (Fig. 3: A-F). Cervical 8 only preserves its Ph IV-1 39 36 48 – posterior portion, cervical 10 preserves its anterior articular surface Abbreviation: l, length of element; wa, anterior width of shaft; wp, posterior width and prezygapophyses, and cervical 14 preserves its prezygapophyses of shaft; wm, middle width of shaft. and postzygapophyses. The longest cervical is Ce 9, and its EI value HISTORICAL BIOLOGY 5

(length of centrum excluding condyle/height of posterior articular flexible neck at this position. The ventral surface of the centrum is surface) is 4.41. This high value (above 4) is typical for Omeisaurus, generally flat without the mid-keel in Ce 16 and 17. The ventrolateral for example, it is 4.81 in Ce 9 of Omeisaurus tianfuensis and 5.05 in ridge is weakly developed in Ce 16 and absent in Ce 17. The para- S66 which is presumed from one of Ce 5–8 (He et al. 1988; Tan et al. pophysis is broad and positioned on the anteroventral region of the 2018). The anterior articular surfaces of centra extend strongly as centrum. Only one relatively simple pneumatic fossa exists on the hemispherical balls. The posterior articular surfaces of centra are central lateral surface. The length of this fossa is about 2/3 length of concave mildly. In both anterior and posterior views, the shape of centrum. The EI values of Ce 16 and 17 are 2.4 and ~2.35, respectively. anterior and posterior articular ends is elliptical, higher than wider. No notch can be observed on the dorsal edge of the posterior Cervical ribs. All cervical ribs are incomplete. The capitulum is articular surface. The central ventral surface of centrum is concave a slightly dorsoventrally compressed element that extends medially with a mid-keel, which is more prominent on the posterior than the and a little dorsally from the main body of the rib. The angle anterior portion. This keel extends to the posterior articular surface between the capitulum and the anterior process is about 30 degrees. as the condition in Omeisaurus tianfuensis. Between the mid-keel This capitular plate extends anteroposteriorly towards the shaft. and the ventrolateral ridges of centra are two long concavities, and The tuberculum is also dorsoventrally compressed and extends the depth of the concavity increases posteriorly, resembling to that ventromedially. The angle between the tuberculum and anterior in S66 (Tan et al. 2018). process is about 60 degrees, and the angle between the tuberculum The parapophyses are anteroposteriorly extended. The diapo- and capitulum is about 30 degrees (Fig. 3I). The tuberculum and physis is situated on the neurocentral junction and oriented ven- capitulum form a shallow concave area on the medial part of the trolaterally, with an extending posterior portion as in Omeisaurus main body of the rib. There is a septum between the base of the tianfuensis and S66 (He et al. 1988; Tan et al. 2018). The paradia- capitulum and anterior process. The cross-section of ribs is trian- pophyseal lamina (PPDL) is situated on the posterodorsal portion gular and keeps its shape along the whole shaft. of parapophyses. Complex pneumatic fossae exist on the lateral surfaces of centrum. A large fossa occupies most the lateral surface, Dorsal vertebrae and its anteroposterior length is more than two thirds of the total All 12 dorsal vertebrae are preserved (Fig. 4). Although most of length of the centrum. The anterior edge of the fossa is above the them are completely preserved, only certain area are prepared and parapophysis, and its summit is on the middle portion. This fossa ready for study (e.g. D6, left lateral elements exposed). All centra are can be further divided into three secondary fossae, and the middle opisthocoelous, with hemispheric convex anterior articular surfaces one is the largest. The depth of the middle fossa is prominently and deeply concave posterior articular surfaces. Internal pneuma- greater than that of the anterior and posterior ones. It is extremely ticity (observed by broken dorsal vertebra) exists on dorsal centra, deep and the left and right fossae almost contact to each other with and the lateral pneumatic fossae are prominent. All neural spines of only several millimetres septum in between. Third level fossae also the dorsal vertebrae are single (no bifid), and vertically oriented. exist. Besides these complex fossa-septum systems, internal pneu- The neural spines reach their highest height in dorsals 6–9. maticity is also visible on broken vertebrae (Ce14) as in S66 (Tan Dorsal 3 is distinctly shorter than dorsal 1 and 2 (Fig. 4A). The et al. 2018). Additionally, there is a small pneumatic fossa on the articular ball is well developed, with its length about 30% that of the dorsal surface of the parapophysis. centrum. The ventral surface is flat, without mid-keel. An antero- The neural arch is distinctly shorter than the centrum. Height of posteriorly elongated and elliptical fossa exists on the posterior the neural arch is about two fifths of the central height. The neural portion of lateral surface of the centrum. The posterior margin of canal is elliptical and mediolaterally compressed. The prezygapophy- the fossa is round. The anteroposterior length of the fossa is about sis expands beyond the anterior margin of the central articular sur- one third the length of the centrum. In following dorsals, the fossa is face. The articular surface of prezygapophysis is flat with oval shape. more developed and situated closer to the anterior articular surface. The distal end of the prezygapophysis extends slightly ventrally. A septum exists in each fossa, similar to that in Omeisaurus tian- A prominent concavity exists on the dorsal surface of the prezyga- fuensis (He et al. 1988). pophysis, which is similar to the condition in Omeisaurus tianfuensis In dorsal 6, central length is about equal to the height of anterior and S66 (He et al. 1988; Tan et al. 2018). The prezygapophysis is articular surface. The middle portion of the centrum is prominently ventrally supported by the centroprezygapophyseal lamina (CPRL). compressed transversely. Deep pneumatic fossa is situated on the CPRL is not divided, and connects to the intraprezygapophyseal middle upper portion of the centrum. This condition is similar to lamina (TPRL) at the ventral surface of the prezygapophysis. The that in O. tianfuensis, whereas that in O. jiaoi is situated on upper posterior centrodiapophyseal lamina (PCDL) is weakly developed. portion of centrum. Anteroposterior length of this fossa is about The postzygodiapophyseal lamina (PODL) is a robust element. The half length of the centrum. Several septa divide the fossa into several postzygapophysis does not extend beyond the centrum. The centro- secondary fossae, similar to that in O. tianfuensis, whereas that postzygapophyseal lamina is not divided. septum is absent in Omeisaurus jiaoi (He et al. 1988; Jiang et al. The neural spine extends anteroposteriorly on the middle por- 2011). tion of the vertebra, and is low dorsoventrally and narrow trans- The height of neural arch in dorsal 6 is shorter than height of the versely. It is about half length of the centrum (0.51 in Ce 9 and 0.46 posterior central articular surface (Fig. 4C). The prezygapophysis in Ce12). The dorsal surface of neural spine is flat and does not oriented slightly dorsally and extends slightly beyond the anterior expand. A small fossa exists on the base of its lateral surface as in margin of the centrum, resembling to that in Omeisaurus tianfuen- S66 (Tan et al. 2018), whereas it is absent in Omeisaurus tianfuensis sis (He et al. 1988). The articular surface of the prezygapophysis is (He et al. 1988). elliptical and dorsomedially oriented. Parapophysis is on the ante- Among the posterior cervicals, Ce 15 only preserves its prezygapo- rodorsal portion of the neural arch and extends laterally. The physes, and Ce 16–17 only exposed the centra with other parts still in articular surface of the parapophysis is triangle. The diapophysis matrix (Fig. 3: G, H). The centra probably experienced dorsoventral is short, curves smoothly into the dorsal surfaces of its transvers compressed deformation, which makes their width larger than the process, similar to that in Omeisaurus tianfuensis (He et al. 1988). height. Ce 17 shows an extremely expanded articular ball, with its The articular surface of diapophysis is quadrangle with a central length ratio 0.44 of the length of the centrum. This may indicate a very concavity. 6 C. TAN ET AL.

Figure 4. Dorsals of Omeisaurus puxiani sp. nov. (A) Dorsal 1-3 and rib in ventrolateral view; (B) Dorsal 4-5 in posterodorsal view; (C) Dorsal 6 in left lateral view; (D) Dorsal 7 in posterior view; (E) Dorsal 8-9 in right lateral view, (F) Dorsal 10-12 in anterodorsal view, (G) Dorsal 10-12 and Sacral 1 in right view. Abbreviations: ACPL, anterior centroparapophyseal lamina; CPRL, centroprezygapophyseal lamina; dor, dorsal; DI, diapophysis; pf, pneumatic fossa or foramen; NC, neural canal; NSP, neural spine; PA, parapophysis; PRZ, prezygapophysis; POZ, postzygapophysis; PCDL, posterior centrodiapophyseal lamina; PODL, postzygodiapophyseal lamina; PPDL, prezygadiapophyseal lamina; PRDL, prezygodiapophyseal lamina; PRPL, prezygaparapophyseal lamina; RI, rib; sa, sacral; POST. SPDL, posterior spinodiapophyseal lamina; SPOL, spinoprezyga- pophyseal lamina; SPRL, spinoprezygapophyseal. Scale bars equal 10 cm.

The neural spine of dorsal 6 is rob-like, with its anteroposterior Dorsal 7 is anteroposteriorly short. This condition is mostly length is about equal to the mediolateral width. The height of the caused by anteroposteriorly compressing during preservation for neural spine is about 0.4 total height of the vertebra. The orienta- the posterior portion of vertebra is upward, by contrast, some other tion of the neural spine is vertical. In anterior view, the morphology elements are slightly mediolaterally compressed during preservation of neural spine is rectangular for most of its length. The pre-spinal for their lateral portion is upward (Fig. 4D). The shape of posterior lamina is absent, and the anterior surface is convex. Three fossae articular surface is generally circular with flat dorsal edge. Ratio of exist on the lateral surface of the neural spine, and the middle one is height of neural arch to total height of vertebra is relatively high the deepest. These fossae are also exist in Omeisaurus tianfuensis,by (0.27). The shape of neural canal is sub-circular, being considerably contrast, they are more close to each other in Omeisaurus tianfuen- taller than wide, and its diameter is 0.2 of the central height. The sis (He et al. 1988). Both spinoprezygapophyseal lamina (SPRL) and parapophysis is situated higher than that of dorsal 6. The diapophysis spinopostzygapophyseal lamina (SPOL) are well preserved, starting is oriented dorsolaterally. The height of the neural spine is slightly from the base of the neural spine. Spinodiapophyseal lamina higher than that of the centrum, and is 0.4 the total height of the (SPDL) also exists and contacts the middle portion of the SPRL. vertebra. The cross-section of neural spine is quadrangle. HISTORICAL BIOLOGY 7

Figure 5. Caudal vertebrae of Omeisaurus puxiani sp. nov. (A) Caudals 1-10 in right lateral view; (B) Six middle caudals in right lateral view; (C) Four middle caudals and chevron in left lateral view; (D) Four posterior caudals and chevron in left lateral view. Abbreviations: ca, caudal; NSP, neural spine; POZ, postzygapophysis; PRZ, prezygapophysis; sa, sacral. Scale bars equal 10 cm.

Dorsals 8 and 9 are articulated (Fig. 4E). The anterior articular Dorsal ribs. Several dorsal ribs are partly preserved. According to ball is not as convex as in the previous ones. Height of the articular the mostly complete one, the shaft is stout, with the width of the surface is larger than its width. The lateral fossa is more developed proximal end of 250 mm and middle width of the shaft of 82 mm. than in anterior ones. Height of the neural arch is two thirds the The capitulum and tuberculum form an angle of about 60 degrees. height of the vertebra. Shape of the articular surface of the para- The orientation of the capitulum is generally similar to that of the pophyses is oval. There is a small concavity on the dorsal surface of shaft. There is a concavity on the lateral surface of the capitulum. the parapophysis. Height of the neural spine is 0.37 the total height The tuberculum is an anteroposteriorly compressed sheet of bone, of the vertebra. The spinoprezygapophyseal lamina (SPRL) and and the tubercular articular surface expands to overhang the ante- spinopostzygapophyseal lamina (SPOL) start from the base of the rior and posterior surfaces of the proximal plate. The anterior neural spines. SPRL, SPDL and PRDL surround a fossa, while surface of the shaft is convex, while the posterior surface is concave. SPOL, SPDL and PODL surround a deep fossa. A large circular The cross section of the shaft is rectangle. fossa exists between SPRL and SPOL on the lateral surface of the neural spine. Caudal vertebrae. Twenty-four caudals are preserved as four ser- Dorsals 10–12 are articulated (Fig. 4 F). Total length of ies, and most of them are complete (Fig. 5). They represent anterior, these vertebrae is 450 mm. The ventral surface of dorsal 12 middle and posterior series. The anterior series includes caudals is transversely narrow. The anteroposterior length of the lat- 1–10. The middle caudals are represented by two parts (one series eral fossa is more than half the length of the centrum. of six, and the other of four). The posterior caudals include four Parapophysis is oriented laterally. The vertically oriented articulated ones. neuralspineisrod-like.Theanteroposterior length of the Anterior caudals are slightly amphicoelous, similar to that in neural spines is longer than its transverse width, whereas Omeisaurus tianfuensis. The transverse process of the first caudal shorter in Omeisaurus tianfuensis,andothertaxaof extends prominently dorsoventrally, and its neural spine is higher Omeisaurus (e.g. O. jiaoi)(Heetal.1988).SPRL,SPOL,and than the posterior ones. Neural spine of the first caudal is articulated SPDL are well preserved. The triangular aliform processes are to the last sacral. Lengths of these anterior centra are approximately the more developed than that in the anterior dorsals. same. Length of each centrum is shorter than height of the posterior articular surface. Height of posterior articular surface/total height of Sacral vertebrae. The first sacral is articulated with the last dorsal vertebra is below 0.4, whereas the ratios in Omeisaurus jiaoi are above vertebra (Fig. 4G), while the neural spine of the last sacral is 0.45 (Jiang et al. 2011). The ventral surface of centrum is transversely articulated with the first caudal vertebra (Fig. 5A). The diapophysis convex. The lateral surface of the centrum is concave in the middle of sacral 1 is prominently dorsoventrally extended, while the length portion. Transverse process is laterally oriented with ‘wing-like’ shape, of its neural spine is distinctly shorter than that of dorsals. The similar to that in Omeisaurus tianfuensis and Mamenchisaurus youngi height of neural spine of the last sacral is higher than that of caudal (He et al. 1988; Ouyang and Ye 2002). Height of neural arch is about vertebrae. Pneumatic fossa is absent on sacrals. half height of posterior surface of centrum. The neural arch is situated 8 C. TAN ET AL.

Figure 6. Anterior appendicular bones of Omeisaurus puxiani sp. nov. Clavicle in ventral (A), anterior (B), posterior (C), dorsal (D) views; Right humerus in posterior (E) and anterior (F) views; (G) Right ulna and radius in anterior view; (H - I) Right manus in dorsal view. Abbreviations: cap, carpal; DPC, deltopectoral crest; Mc: metacarpal. Scale bars equal 10 cm.

on the anterior half of centrum, and the neural arches of subsequent postzygapophyses are slender than those in anterior caudals. The centra generally extend backward in lateral view. The end of the anterior end of prezygapophyses is beyond the centrum, while the prezygapophysisisbeyondtheanterior margin of centrum. Its articu- posterior end of postzygapophyses end at the level of the posterior lar surface is elliptical, and dorsomedially oriented. The postzygapo- surface. The neural spines extend dorsally and slightly posteriorly. physis is not beyond the posterior margin of centrum. Heights of All posterior caudals are amphicoelous, and the posterior articu- neural spines are shorter than the height of centrum. The neural spines lar surfaces are more concave than those in the anterior ones. are dorsally oriented. The anteroposterior length of neural spines is Length of centrum is larger than height of posterior surface. slightly larger than its transverse length. The end of neural spines is Height of neural arch/length of centrum is about 0.3. The neural posteriorly expanded, a feature not seen in Omeisaurus and arch is situated on middle of centrum. Anteroposterior length of Mamenchisaurus (e.g. O. tianfuensis; O. jiaoi; O. maoianus; neural arch is more than half the length of centrum. The end of Mamenchisaurus youngi). This may increase the stability of anterior prezygapophysis is not beyond centrum. Postzygapophyses weakly caudals. SPRL and SPOL exist and start from the base of the neural develop. In lateral view, the neural spine is finlike, and strongly spines. oriented posteriorly. The middle caudals are slightly amphicoelous. Length of each centrum is larger than height of posterior articular surface. Height Chevrons. Anterior chevrons are closed ‘Y’ shaped (referred Otero of posterior articular surface is larger than width. Transvers process et al. (2011)). Crus bridging dorsal margin of haemal canal of is absent. The height of neural arch is one third that of posterior chevrons are present. The distal process of the chevron is plate- surface. In lateral view, neural arch is mostly situated on the ante- like in lateral view. Two processes of the middle chevrons are not rior half of the centrum, the posterior portion of neural arch over fused, and form a ‘Y’ shape with the angle below 90 degrees. The the midpoint of the centrum. The prezygapophyses and width of the dorsal process is about half total chevron length. Distal HISTORICAL BIOLOGY 9 chevrons are forked, and the angle between two dorsal processes is Ulna. The right ulna is well preserved (Fig. 6 G). Length of ulna much larger than that in anterior ones. is about 0.69 of humerus length (according to the preserved portion of humerus), and the minimum shaft width is 79 mm. The anterolateral, anteromedial, and posterior processes are Clavicle. An incomplete clavicle is preserved, missing both ends weakly developed, and the olecranon process is also weak. The (Fig. 6A-D). The length of preserved rob-like shaft is 420 mm, with anterolateral process (measured from the posterior surface to the maximum width of 80 mm and minimum width of 42 mm. tip of the anterolateral process) is longer than the anteromedial process (measured from the posterior surface to the tip of the Humerus. The right humerus is preserved with incomplete anteromedial process). The ‘U’ shape of proximal surface is trans- anterior and posterior ends (Fig. 6E and F). The lateral portion formed into a circular cross section at mid-shaft, similar to most of proximal end is incomplete, and the surface of proximal end of sauropods such as Omeisaurus tianfuensis. There is a convex is covered by layers of plaster totally. The preserved length of area on distal portion of anteromedial surface where it received the humerus is 850 mm, and the minimum mid shaft width is the posteromedial surface of distal end of the radius, resembling to 110 mm. In anterior view, both preserved proximal and distal that in Omeisaurus tianfuensis, Huangshanlong anhuiensis, portions expand gradually towards ends according to the pre- Anhuilong diboensis,andMamenchisaurus youngi (He et al. served portion. The deltopectoral crest is weakly developed, as 1988; Huang et al. 2014; Ouyang and Ye 2002; Ren et al. 2018). in Omeisaurus tianfuensis (He et al. 1988). The deltopectoral The distal surface of the ulna is oval, similar to Omeisaurus crest directs anteromedially, resembling to that in some early tianfuensis (He et al. 1988). diverging eusauropods (e.g. lii, Omeisaurus tian- fuensis). Moreover, the edge of the deltopectoral crest is Radius. The right radius is well preserved and articulated with oriented posterolaterally, similar to that in Anhuilong diboensis ulna (Fig. 6G). This element is slender, and length of radius is (Ren et al. 2018). The cross section of the mid-shaft is ovoid, about 0.67 of preserved humerus length. The distal width of similar to that in , Shunosaurus lii,andOmeisaurus proximal end is one-fifth the total length, and the width is tianfuensis (Cooper 1984;Zhang1988; He et al., 1988). about half width of proximal end. The proximal end is

Figure 7. Posterior appendicular bones of Omeisaurus puxiani sp. nov. Left ilium in lateral view (A); Left femur in posterior (B), medial (C), anterior (D) and lateral (E) views; Right tibia and fibula in posterior view (F). Abbreviations: 4th tr, the fourth trochanter of femur; fi, fibula PRA, preacetabular; ti, tibia. Scale bars equal 10 cm. 10 C. TAN ET AL. elliptical. A distinct convex area exists on the posteromedial references of Mamenchisaurus youngi (Ouyang and Ye 2002) and surface of distal portion. The distal end is elliptical with coarse Omeisaurus tianfuensis (He et al., 1988). (Table 3). surface. Our phylogenetic analysis generated 180 most parsimonious trees (MPTs) with following values: tree length = 1410, consistency Carpals. Two oval-shaped carpals are preserved (Fig. 6G). The index (CI) = 0.347, and retention index (RI) = 0.726. The strict mediolateral width of these two carpals are equal to the proximal consensus tree is relatively well resolved (Fig. 8). Omeisaurus pux- widths of metacarpals I and II, respectively. iani, S66 and Omeisaurus tianfuensis are recovered in an unresolved clade, and this clade and Mamenchisaurus youngi form the Metacarpals. Five right metacarpals are preserved (Fig. 6H and I; Mamenchisauridae clade. Table 2). Metacarpal I is the shortest. Its two distal condyles are The mamenchisaurid clade is supported by 13 unambiguous syna- ‘ ʹ ‘ ’ ‘ ’ prominent, and lateral process is stouter than the medial one. The pomorphies ( 0 to 1 for character 115, 122, 124, 129, 136, 148, 180; 1 ‘ ’ ‘ ’ ‘ ’ ‘ ’ ‘ ’ proximal end of metacarpal IV does not expand, and the upper to 0 for character 141, 174; 1 to 2 for character 207; 0 to 2&3 for ‘ ’ ‘ ’ ‘ ’ ‘ ’ portion of its medial surface is concave. Length of metacarpal V is character 161; 2 to 1 for character 175; 2 to 4 for character 119). slightly longer than that of metacarpal I, and its medial condyle is Omeisaurus puxiani shows 10 of the 13 synapomorphies of the stronger than the lateral one. Mamenchisauridae clade: Ventral surface of cervical centra is trans- versely concave (ch. 124); Epipophyses of cervical vertebrae are poster- Phalanges. Five proximal phalanges and one ungual are preserved iorly projecting prongs (ch. 129); Internal pneumaticity is present in (Fig. 6H and I). The proximal end of Ph I-1 is articulated to the Mc cervical centra (ch. 136); Height of the neural arch of middle cervical I, and its distal articular surface is not preserved. The proximal end vertebrae is less than the height of the posterior articular surface (ch. of Ph II-1 does not expand, and the shape of proximal surface is elliptical. Distal width of Ph II-1 is larger than its length. Its middle cross section is smaller than the proximal end. In distal view, medial and lateral surfaces are convex. The distal end does not expand prominently. Width of proximal end of Ph II-1 is two thirds of distal end width. The lateral and medial condyles of Ph II-1 are laterally and medially extend, respectively. The angle between two condyles is beyond 90 degrees. The medial condyle is slightly stouter than the lateral one. Ph IV-1 is much smaller than Ph II-1. The angle between its two distal condyles is less than 90 degrees. Ph V-1 persevers its proximal articular surface. Proximal end of Phalanx I-2 (Ungual 1) is incomplete. This bone is a stout element. Its dorsal surface is smooth. Proximal width of Ph I-2 is larger than distal width of Ph I-1. In lateral view, its dorsal and ventral surfaces are curve. The distal end is sharp.

Ilium. Partial anterior portion including the pre-acetabular pro- cess of the left ilium is preserved (Fig. 7A). The pre-acetabular process is 190 mm long and laterally oriented. The pubic peduncle is robust.

Femur. Both femora are partly preserved: the right one preserves its proximal portion, and the left one misses the femoral head and distal end (left femur in Fig. 7B–E). The lateral bugle is absent. The fourth trochanter is a high crest and positioned near the medial margin on posterior surface, similar to that in Omeisaurus jiaoi, whereas Omeisaurus tianfuensis and Mamenchisaurus youngi share a middle positioned fourth trochanter on posterior surface (Jiang et al. 2011; He et al. 1988; Ouyang and Ye 2002). The middle cross section is elliptical.

Tibia and fibula. Distal half of right tibia is preserved, and articu- lated with fibula (Fig. 7 F). Width of distal end is 1.8 that of middle cross section. The anteroposterior width of distal end is shorter than mediolateral width. The elliptical distal end extends promi- nently. Distal portion of right fibula is preserved. Its anteromedial surface is flat and articulated with the distolateral concavity of tibia.

Phylogenetic analysis. In order to explore the phylogenetic posi- tion of the new specimen a cladistic analysis is performed based on the data matrix of Tan et al. (2018). This matrix comprises 405 characters and 89 operational taxonomic units (OTUs) (including Omeisaurus puxiani sp. nov.). We revised seven scoring errors in Figure 8. Strict consensus of 180 MPTs from phylogenetic analysis. The data matrix the previous matrix based on personal observation and published follows Tan et al. (2018) with 89 taxa and 405 characters (See Appendix 1). HISTORICAL BIOLOGY 11

Figure 9. Comparison of middle cervical and dorsal vertebrae of Omeisaurus puxiani sp. nov (A and B), S66 (C), Mamenchisaurus youngi (D and E), and Omeisaurus tianfuensis (F and G) in lateral view. Abbreviations: DI, diapophysis; pf, pneumatic fossa or foramen; NSP, neural spine; PA, parapophysis; POZ, postzygapophysis; PRZ, prezygapo- physis. Scale bars equal 10 cm.

141); Parapophysis shape of middle and posterior cervical vertebrae middle and posterior dorsal centrum in transverse section (height: anteroposteriorly elongate (ch. 148); Pneumatic structures of dorsal width ratio) are slightly dorsoventrally compressed (ch. 195, centra are present with small and complex air-spaces (camerate or state 1); anterior caudal transverse processes shape is ‘wing-like’, polycamerate) (ch. 161); Neural spine minimums width/length of not tapering distally (ch. 236, state 1). anterior dorsal vertebrae are 0.5 or greater (ch. 174); Neural spine length (from TPRL to top) of anterior dorsal vertebrae is slightly higher than the centrum (ch. 175); Hyposphene-hypantrum of poster- Discussion ior dorsal vertebrae are present and weakly developed, mainly as a laminar articulation (ch. 180); Articular face shape of posterior dorsal It is worth noting that S66, the single middle cervical vertebra from centra is opisthocoelous (ch. 207). the same locality (Tan et al. 2018), shares numerous features with The (Omeisaurus tianfuensis, Omeisaurus puxiani, and S66) cervical 9 of Omeisaurus puxiani. For example, the complex lateral clade is supported by four synapomorphies: anteroposterior length fossa and internal pneumaticity of the centrum, the concavity divided the height of the posterior articular surface in middle formed by mid-keel and ventrolateral ridge on central ventral sur- cervical centrum is more than 4 (ch. 142, state 1); prominent face, pits at base of neural arch, and tuber on the anterior margin of triangular flange on posterior edge of the diapophyseal process in neural spines. Therefore, S66 (Tan et al. 2018) is here assigned as middle and posterior cervical vertebrae is present (ch. 146, state 1); a referred specimen of Omeisaurus puxiani. 12 C. TAN ET AL.

According to the study of S66, this specimen (therefore Disclosure Statement O. puxiani) is most similar to O. tianfuensis He et al. 1984 and No potential conflict of interest was reported by the authors. O. luoquanensis Li 1988. O. fuxiensis Dong et al. 1983 and O. jiaoi Jiang et al. 2011 do not preserve cervicals; therefore, cannot be compared to S66 (therefore O. puxiani) at that time. However, Funding O. fuxiensis only preserves partial cranial material and an axis, This study is supported by Project of Dinosaur Fossil Protection and Research of and its horizon is upper Shaximiao Formation, it is probably dif- Chongqing Planning and Natural Resources Bureau (No. kj-2018035); The ferent from O. puxiani (Fig. 9). Strategic Priority Research Program of Chinese Academy of Sciences (Grant In O. luoquanensis, no mid-keel exists on the ventral surface of number: XDB26000000); National Natural Science Foundation of China (Grant its middle cervicals, lengths of anterior caudal centra increase numbers: 41688103, 41872021); Natural Science Foundation of Chongqing, gradually, and cross section of the humerus shaft is more circular China (No. cstc2018jcyjAX0435); Postdoctoral Project of Chongqing, China (No. Xm2017069). than elliptical. In O. jiaoi, there is no septum in the lateral fossa of the centrum, and no lateral fossa on the spinoprezygapophyseal lamina as well. The height of the posterior articular surface is more ORCID than 45% of the total vertebral height in anterior caudals, and the Shan Jiang http://orcid.org/0000-0001-7766-222X length of the metacarpal III is obviously longer than that of the Hai-Lu You http://orcid.org/0000-0003-2203-6461 metacarpal II. All these features are not present in O. puxiani. O. tianfuensis is also different from O. puxiani. Firstly, an acces- sory lamina exists between prezygodiapophyseal lamina (PRDL) References and centroprezygapophyseal lamina (CPRL) in middle to posterior cervicals in O. puxiani, whereas this lamina is absent in Cooper MR. 1984. The prosauropod dinosaur carinatus Owen fi O. tianfuensis. Secondly, a pneumatic fossa exists on the lower from Zimbabewe: its biology, mode of life and phylogenetic signi cant. Occas Pap, Natl Mus. 6:689–840. portion of postzygapophysis O. puxiani, whereas this fossa is absent Dong ZM, Zhou SW, Zhang YH. 1983. Dinosaurs from the Jurassic of Sichuan. in O. tianfuensis. Thirdly, secondary septa dividing lateral pneu- Palaeontol Sin Ser C. 23:1–151. matic fossae are prominent and well developed on cervicals in Fang XX, Zhao XJ, Lu LW, Cheng ZW. 2004. Discovery of Late Jurassic O. puxiani, whereas most of cervicals in O. tianfuensis do not Mamenchisaurus in Yunnan, southwestern China. Geol Bull China. 23:1005–1009. possess secondary septa. Fourthly, anterior articular surface is Goloboff PA, Catalano SA. 2016. TNT version 1.5, including a full implementa- strongly expanded in anterior dorsals in O. puxiani, whereas that tion of phylogenetic morphometrics. Cladistics Int J Willi Hennig Soc. in O. tianfuensis is weakly developed. Fifthly, neural spines of 32:221–238. doi:10.1111/cla.12160 posterior dorsals are anteroposteriorly compressed in O. puxiani, Gu XD, Liu XH. 1997. lithostratigraphy of Sichuan (in Chinese). Hubei: China – by contrast, those in O. tianfuensis are transversely compressed. University of Geosciences Press; p. 1 417. He XL, Li K,Cai KJ. 1988. The Middle Jurassic Dinosaur Fauna from Dashanpu, Sixthly, the orientation of edge of deltopectoral crest is posterolat- Zigong, Sichuan. Chengdu: Sichuan Publishing House of Science and eral, whereas that in Omeisaurus tianfuensis is anterolaterally. Technology; p. 143. Seventhly, metacarpal I and IV of O. tianfuensis are stouter than He XL, Li K, Cai KJ,Gao YH. 1984. Omeisaurus tianfuensis—a new species of those of O. puxiani. Finally, the fourth trochanter is positioned near Omeisaurus from Dashanpu, Zigong, Sichuan. Journal of Chengdu College of Geology. 2:15–32. the medial margin of posterior surface in O. puxiani, whereas that Huang DY. 2018. Jurassic integrative stratigraphy and timescale of China. Sci in O. tianfuensis is on the middle of posterior surface. China Earth Sci. doi:10.1007/s11430-017-9268-7. Omeisaurus puxiani also possesses some unique features among Huang JD, You HL, Yang JT,Ren XX. 2014. A new sauropod dinosaur from the Omeisaurus, such as posteriorly expanded neural spine dorsal end Middle Jurassic of Huangshan. Anhui Province. Verteb Palasiat. 52(4):390– in anterior caudals, edge of humerus deltopectoral crest turns 400. Huene FV. 1932. Die Fossile Reptil-ordnung Saurischia: ihre Entwicklung und posterolaterally, and ratio of total length of ulna to humerus is Geschichte. Gebruder Borntraeger. Monographien Geol Palaontologie. 0.69. Therefore, O. puxiani represents a distinct species of the S1:1–361. Omeisaurus genus. Jiang S, Li F, Peng GZ, Ye Y. 2011. A new species of Omeisaurus from the middle Jurassic of Zigong, Sichuan. Vertebrata Palasiatica. 2:185–194. Li K, Yang CY, Liu J, Wang ZX. 2010. A new sauropod from the Lower Jurassic of Huili, Sichuan, China. Vertebrata Palasiatica. 48:185–202. Conclusions Li Y Q, He D F, Li D, Lu R, Fan C, Sun Y, Huang H. 2018. Sedimentary provenance constraints on the Jurassic to Cretaceous paleogeography of The new specimen represents a new species of Omeisaurus Sichuan Basin, SW China. Gondwana Res. 60:15–33. doi:10.1016/j. (O. puxiani), and the previously reported single middle cervical gr.2018.03.015 (S66) from the same locality and horizon can be referred to this Mannion PD, Upchurch P, Barnes RN,Mateus O. 2013. Osteology of the Late new species. The discovery of Omeisaurus puxiani enriches the Jurassic Portuguese sauropod dinosaur atalaiensis () and the evolutionary history of basal titanosauriforms. Zool J Linn Soc. 168 diversity of the genus of Omeisaurus and provides additional infor- (1):98-206. doi:10.1111/zoj.12029. mation to help understand the evolutionary history of this genus in Mannion PD, Upchurch P, Schwarz DA, Wings O. 2019. Taxonomic affinities of Eastern China. the putative titanosaurs from the Late Jurassic Tendaguru Formation of Tanzania: phylogenetic and biogeographic implications for eusauropod dino- saur evolution. Zool J Linn Soc. 99:1–126. Marsh OC. 1878. Principal characters of American Jurassic dinosaurs (Part 1). Acknowledgments Am J Sci. 16:411–416. doi:10.2475/ajs.s3-16.95.411 Otero A, Gallina PA, Canale JL, Haluza A. 2011. Sauropod haemal arches: We are grateful to Wei Guangbiao and He Jianjun and the personnel of the morphotypes, new classification and phylogenetic aspects. Hist Biol. 1–14. Yunyang Dinosaur Administration for various help during this study, to Zhang, doi:10.1080/08912963.2011.618269. Yu-Qing, Han, Xiang-Song and others for preparing the specimen, to Li, Qi for Ouyang H, Ye Y. 2002. The first mamenchisaurian skeleton with complete skull helping photographing, to Ye, Yong and Hao, Bao-Qiao for providing informa- Mamenchisaurus youngi. Chengdu: Sichuan Publishing House of Science and tion on Omeisaurus tianfuensis at Zigong Dinosaur Museum. Thoughtful Technology; p. 1–111. reviews by Guillermo J. Windholz, Toru Sekiya, an anonymous reviewer, and Owen R 1842. Report on British Fossil Reptiles. Part II. 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