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PALAEONTOLOGY

A new lithostrotian titanosaur (Dinosauria, ) from the Early of Transbaikalia, Russia

Alexander Averianov a, b and Pavel Skutschas c a Zoological Institute, Russian Academy of Sciences, Universitetskaya nab., 1, St. Petersburg, 199034, Russian Federation; [email protected], [email protected] b Department of Sedimentary Geology, Institute of Earth Sciences, Saint Petersburg State Univer- sity, 16th Liniya V. O., 29, St. Petersburg, 199178, Russian Federation c Department of Vertebrate Zoology, Saint Petersburg State University, Universitetskaya nab., 7–9, St. Petersburg, 199034, Russian Federation; [email protected] Address correspondence and requests for materials to Alexander Averianov

Abstract

Tengrisaurus starkovi, gen. et sp. nov., is described based on three caudal verte- brae from the Lower Cretaceous (?) Murtoi Formation at Mogoito locality, near Gusinoe Lake in Buryatia, Russia. The new taxon is characterized by strongly procoelous anterior and middle caudal vertebrae, with strongly developed pre-epi- pophyses, highly pneumatic neural spine, and solid bone structure of the centrum. The reweighted phylogenetic analysis places the new taxon as a non-saltasau- rid lithostrotian titanosaur (Sauropoda). This is one of the oldest fossil records of and , which suggests a long and unexplored evolution of titanosaurs in the of Asia. Keywords: Dinosauria, Sauropoda, Titanosauria, Lithostrotia, Early Cretaceous, Transbaikalia, Russia

Citation: Averianov, A. and Skutschas, P. 2017. A new lithostrotian titanosaur (Dinosauria, Introduction Sauropoda) from the Early Cretaceous of Transbaikalia, Russia. Bio. Comm. 62(1): 6–18. The first Russian , the theropod “Allosaurus” sibiricus, was found in the doi: 10.21638/11701/spbu03.2017.102 Lower Cretaceous strata of Transbaikalia (Riabinin, 1914; Ivanov, 1940). During Author’s information: Alexander Averianov, Dr. Sci., Professor, orcid.org/0000-0001-5948-0799, the last century our knowledge of Transbaikalian improved insufficient- Researcher ID: M-8490-2013; Pavel Skutschas, ly (Nesov and Starkov, 1992; Nesov, 1995; Averianov and Skutschas, 2000, 2009; Ph.D., Ass. Prof., orcid.org/0000-0001-8093-2905, Researcher ID: D-5143-2013 Averianov et al., 2003). However, from what it is known it is clear that sauropods Manuscript Editor: Nikita Zelenkov, Borissiak were among the dominant herbivores in the Early Cretaceous of Transbaikalia (Ne- Paleontological Institute Russian Academy of sov, 1995). Dmitriev (1960) reported on the discovery of a procoelous, apparently Sciences, Russia caudal sauropod vertebra from the Murtoi Formation at Mogoito locality near Received: November 26, 2016; Gusinoe Lake in Buryatia (Fig. 1). In 1963, additional excavations at this site pro- Revised: January 21, 2017; duced a sauropod scapula and rib and some other bone fragments (Dmitriev and Accepted: February 02, 2017; Rozhdestvensky, 1968). Nesov and Starkov (1992) reported sauropod teeth and Copyright: © 2017 Averianov and Skutschas. This is an open-access article distributed under the terms of procoelous caudal vertebrae from the Mogoito locality. The chisel-like tooth with the License Agreement with Saint Petersburg State V-shaped wear facets, identified as cf. Chiayusaurus sp. (ZIN PH 4/13), and the University, which permits to the authors unrestricted distribution and self-archiving free of charge. procoelous caudal vertebra (ZIN PH 8/13), have been figured by Nesov (1995:pl. 3, Funding: The field work in Transbaikalia in fig. 13, pl. 4, fig. 1). Nesov and Starkov (1992) noted also two osteoderms from 1998–2002 was funded by the Russian Fund of Mogoito, which they referred to Armatosauria. These osteoderms cannot be iden- Basic Researches (grant 98-04-63044) and the National Geographic Society (grant 7089-01). The tified in the collection and their attribution to Sauropoda has not been checked. funders had no role in study design, data collection Averianov et al. (2003:figs 5, 6) described and figured a juvenile tooth (ZIN PH and analysis, decision to publish, or preparation of the manuscript. 9/13), an adult tooth (ZIN PH 4/13), and two caudal vertebrae (ZIN PH 7/13 and Competing interests: The authors have declared 8/13). All these specimens were identified as Titanosauridae indet. As was already that no competing interests exist. noted (Averianov and Skutschas, 2009:370), the small tooth ZIN PH 9/13 actu- ceous, Barremian?). Creta- (Lower Formation Murtoi Russia; Buryatia, Mogoito, views. (B) posterior or Fig. 2.Theropoda indet., tooth (ZIN PH 5/13), in lateral or medial (A, C) and anterior late global the (Clansean) seatransgression. to correlative Lycoptera, fish with level Aptian upper 3, dinosaurs; including remains, vertebrate with level 2, wood; silificied with level 1, coal. with clay and vicinity,coal Lake D, Gusinoe shale; the black of and map Designations: clay the bottom). C, on right sandstone; asterisk B, an conglomerate; by A, and top, right Starkov, and Nesov after modified (left; section Fig. 1.Geological 1992) BIOLOGICAL COMMUNICATIONS , vol.62,issue1,January–March,2017|doi:10.21638/11701/spbu03.2017.102 and geographic position of the Mogoito locality (indicated by a black square on the map of Russia, of map the on square black a by (indicated locality Mogoito the of position geographic and sauropod tooth from Mogoito (ZINPH 4/13),suggesting tanosauria indet. This istooth quite different from the Sereno, 1998) and attributedtooth the can be to Ti the foracteristic of teeth the derived titanosaurs (Wilson and formes indet. However, elliptical the wear facetsare char was which referred inBuryatia, locality to Titanosauri Lowerthe Cretaceous Formation Khilok at Krasnyi Yar ropod tooth with elliptical high-angled wear facetfrom saupencil-like a described and Skutschas (2009:fig. 3) sionally identified here as Theropoda indet. Averianov belong to 2003: fig. 2J). However, likely thisnot (Fig. 2) does tooth golosaurus Mogoito identified(ZIN PH 5/13) has as cf.been belongsally to One incomplete Ornithopoda. tooth from and referred to ?Sauropoda (Averianov et al., 7 (Mannion, 2011).It is provi Mon ------

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Fig. 3. P. Skutschas and G. Sazonov excavating the anterior caudal vertebra of Tengrisaurus starkovi gen. & sp. nov. (ZIN PH 14/13) at Mogoito locality in 1998.

that at least two titanosaurian taxa were present in the Type — Tengrisaurus starkovi sp. nov. Early Cretaceous of Transbaikalia. In 1998, an additional Diagnosis — As for the type and only species. sauropod vertebra (ZIN PH 14/13) has been excavated at Distribution — Early Cretaceous, Asia. the Mogoito locality (Fig. 3). The past decade witnessed a tremendous progress in the study of titanosaurian sau- Tengrisaurus starkovi sp. nov. ropods that allows recognizing the Mogoito sauropod as Figs 4–6 a distinct taxon. This is only the second dinosaur named from Transbaikalia and the first sauropod from Russia to Etymology — After Alexey Starkov for his gener- receive a scientific name. ous assistance and contribution to the study of Early The described material is housed in the Paleoherpe- Cretaceous vertebrates of Transbaikalia. tological collection of the Zoological Institute, Russian Holotype — ZIN PH 7/13, anterior caudal vertebra. Academy of Sciences (ZIN PH). Referred specimens — ZIN PH 14/13, anterior caudal vertebra; ZIN PH 8/13, middle caudal vertebra. Systematic palaeontology Type locality and horizon — Mogoito, near Gusinoe Lake, Buryatia, Russia; Murtoi Formation, Dinosauria Owen, 1842 Lower Cretaceous (Barremian-Aptian). See Nesov and Seeley, 1887 Starkov (1992) for discussion of the age. Sauropoda Marsh, 1878 Diagnosis — Referred to the Lithostrotia because of Titanosauriformes Salgado et al., 1997 strongly procoelous anterior and middle caudals. Differs Titanosauria Bonaparte et Coria, 1993 from all other lithostrotians by a unique combination of Lithostrotia Upchurch et al., 2004 the following characters: horizontal, anteriorly directed Tengrisaurus gen. nov. prezygapophyses on anterior caudals; pre-epipophyses projecting anteriorly beyond the prezygapophyseal ar- Etymology — From Tengri, the primary chief de- ticular surfaces; a divided interprezygapophyseal lamina ity in Mongolian-Turkish mythology, and σαῦρος of anterior caudal vertebrae; position of postzygapophy- (Greek), a lizard. ses well posterior to the anterior end of the middle cau- BIOLOGICAL COMMUNICATIONS , vol.62,issue1,January–March,2017|doi:10.21638/11701/spbu03.2017.102 interpostzygapophyseal lamina;tprl,interprezygapophyseallamina. tpol, lamina; spinoprezygapophyseal sprl, lamina; spinopostzygapophyseal spol, lamina?; spinodiapophyseal spdl?, lamina; prespinal prsl, fossa; prespinal prsf, postzygapophysis; poz, fossa; postspinal posf, lamina; postspinal posl, pre-epipophysis; prepi, prezygapophysis; prez, spine; neural nc, ns, Abbreviations: canal; Barremian?). neural Cretaceous, (Lower Formation Murtoi Russia; Buryatia, Mogoito, (below). drawings explanatory and (above) photographs Fig. 4.Tengrisaurusstarkovi gen. et sp. nov., ZIN PH 7/13, anterior caudal vertebra (holotype), in dorsal (A), anterior (B), lateral (C), and posterior (D) views; (D) posterior and (C), lateral (B), anterior (A), dorsal in (holotype), vertebra caudal nov.,anterior sp. 7/13, et PH gen. ZIN 9

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Fig. 5. Tengrisaurus starkovi gen. et sp. nov., ZIN PH 14/13, anterior caudal vertebra, neural arch in dorsal (A), lateral (B), and posteroventral (C) views; centrum in anterior (D), posterior (E), and lateral (F) views; photographs (left) and explanatory drawings (right). Mogoito, Buryatia, Russia; Murtoi Formation (Lower Cretaceous, Barremian?). Abbreviations: hr, hyposphenal ridge; nc, neural canal; ns, neural spine; pre, prezygapophysis; prepi, pre-epipophysis; posl, postspinal lamina; posf, postspinal fossa; poz, postzygapophysis; prsf, prespinal fossa; prsl, prespinal lamina; spol, spinopostzygapophyseal lamina; sprl, spinoprezygapophyseal lamina.

Fig. 6. Tengrisaurus starkovi gen. et sp. nov., ZIN PH 8/13, middle caudal vertebra, in anterior (A), dorsal (B), lateral (C), posterior (D), and ventral (E) views; photographs (left) and explanatory drawings (right). Mogoito, Buryatia, Russia; Murtoi Formation (Lower Cretaceous, Barremian?). Abbreviations: chf, chevron facet; nc, neural canal; ns, neural spine; pre, prezygapophysis; poz, postzygapophysis; posf, postspinal fossa; trp, transverse process. vertebrae. Differsfrom anteroposteriorly short spine neural caudal inmiddle caudal vertebrae. Differsfrom by lack of spinodiapophyseal lamina on (spdl) anterior anterior caudal vertebrae. Differsfrom transversely prespinal wider and postspinal laminae on surface. Differsfrom articular seal Neuquensaurus by caudalsmiddle posterior placed to postzygapophy the natitan posterodorsally or posteriorly. Differsfrom Gondwa by spine neural of anterior and caudals middle directed rus thocoelicaudia processes caudal inmiddle vertebrae. Differsfrom Opis brae. Differsfrom articulations anterior inthe and caudal middle verte Epachthosaurus processes caudal inmiddle vertebrae.seal Differsfrom from lackthe of postzygodiapophyseal Differs lamina (podl). ventrolaterally. faced ses Differsfrom Neuquensaurus by centrum. Differsfrom well posterior to anterior the end of caudal middle the fers from Aeolosaurus terzygapophyseal fossa in anterior caudal vertebrae. Dif Differsfrom pensis by lack of infraspinoprezygapophyseal lamina. caudal vertebrae. Differsfrom Aeolosaurus colhuehua by interprezygapophyseal adivided lamina of anterior faces. Differsfrom Trigonosaurus anteriorly beyond prezygapophyseal the sur articular saurus Differsfrom teriorly directed prezygapophyses on anterior caudals. fers from Opisthocoelicaudia lack of ventral fossa or groove on caudal centrum. Dif Neuquensaurus, shaped.” Differsfrom Opisthocoelicaudia condyle of anterior and caudal middle centra not “heart- displaced. Differsfrom pensis by posterior condyle of caudal centrum dorsally of caudal centrum. Differsfrom Aeolosaurus colhuehua from caudal centra not compressed dorsoventrally. Differs trally. Differsfrom Maxakalisaurus by anterior caudal centra not compressed dorsoven lisaurus longer caudal middle vertebrae. Differsfrom Maxaka licaudia structure of caudal the centra. directed posterodorsallydals bone orsolid posteriorly; centrum; spine neural dal of anterior and cau middle BIOLOGICAL COMMUNICATIONS , vol.62,issue1,January–March,2017|doi:10.21638/11701/spbu03.2017.102 Trigonosaurus , Differential Diagnosis Gondwanatitan Neuquensaurus by more round surfaces articular , and Lohuecotitan by posterior edge of spine neural of anterior and , by procoelous caudal vertebrae and relatively Gondwanatitan , and , and Neuquensaurus by horizontal, an , by lack the of hyposphene-hypantrum Saltasaurus by lack the of long postzygapophy , by position of postzygapophyses Trigonosaurus , by pre-epipophyses projecting Trigonosaurus Saltasaurus by lack the of lamina in — Differsfrom Opisthocoe , , and , by and middle posterior Aeolosaurus Rinconsaurus by areduced transverse , Aeolosaurus and Neuquensaurus and by postzygapophy Rocasaurus , and Lohuecotitan , , Rocasaurus , and Neuquensaurus, , by posterior , Overosaurus Overosaurus , , Aeolosau by the Trigono by an and and ------, ,

centra. Neuquensaurus by bone solid structure of caudal the concavity along dorsal the margin of anterior the ar missing ventral and lateral edges. There is a prominent of surface centrumticular the is largely with preserved, vertebra missing most of centrum. the The anterior ar The holotype (ZIN PH 7/13;Fig. 4) is an anteriorcaudal Description belong to one ifnot species, individual. in Mogoito three specimens likely and these locality all There areevidences no of morethan sauropodone taxon as apositional variationpected of anterior these caudals. archneural and caudal middle the has amorphology ex caudal vertebrae has almost identical morphology of the andDmitriev Rozhdestvensky, 1968).Thetwo anterior length inaravine Promoina called Klevenskogo (Fig. 3; found proximity inaclose outcrop in inasmall 5–6 m starkovi ferred here to Tengrisaurus posterolaterally oriented. The ventralmost margin the of and oval-shaped, long the axis anteromedially- being prezygapophyseal are surfaces articular gently convex like pre-epipophyses The on lateral their side (Fig. 4C). yond centrum. the There are well-developed,ridge- hyposphenal ridge along space. this space from canal neural the and there is alongitudinal teroposteriorly (Fig. 4D). It is separated by a considerable short lamina (tpol)transversely isseal very but long an are closely approximated and interpostzygapophy the column. The ventral margins postzygapophysesthe of centropostzygapophyseal laminais asimple (cpol) round ly centroprezygapophyseal defined lamina (cprl). The interprezygapophyseal the between ridge and poor the es. The anterior surface the of neural arch is depressed marginsal of canal neural the is bracketed by ridg these with dorsal the margin of canal neural (Fig. 4B). The dor ridges that of connect bases prezygapophyses the the is interprezygapophyseal adivided lamina (tprl), oblique anteriorly and more round posteriorly (Fig. 4B, D). There canalneural is oval-shaped, dorsoventrally compressed almostplaced on anterior the border of centrum. the The surface. The ticular anteriorborder the of neural arch is occupied by concavity the of centrum the anterior ar vertebra arch and neural the all is confined the to space arch neural the was positioned at anterior the end of the oriented). arch (Fig. 4C; on figure, this thecanal neural is obliquely cavity at placed level the of of posterior base neural the centrumthe is deeply concave, with centrum the of con is horizontally oriented, anterior the of surface articular ofsurface ticular centrum. the When canalneural the Remarks The prezygapophyses projects anteriorlybe well Although vertebra the is incomplete, it is clear that — All three sauropod— All caudal vertebrae re 11 gen. etsp. nov. were ------

PALAEONTOLOGY 12 BIOLOGICAL COMMUNICATIONS, vol. 62, issue 1, January–March, 2017 | doi: 10.21638/11701/spbu03.2017.102 prezygapophyseal articular surface is vertical and set at ball-like, asymmetrical in lateral view, with the dorsally angle with the rest of the facet. The postzygapophyseal displaced center (Fig. 5F). A strong ridge circumscribes articular surfaces are also oval-shaped, long axis ventro- the posterior condyle. The articular condyle is restricted medial-dorsolateral, and convex (more convex on the from the outer margin by a relatively wide flat area. On right side). the posterior side, below the centrum articular surface, Only the base of the transverse process is preserved. there are triangular-shaped chevron facets which face Evidently the transverse process was not dorsoventrally posteriorly. On the ventral side of the centrum there is expanded. It is anteroposteriorly wide, occupying all the a prominent longitudinal groove between the chevron anteroposterior width of the neural arch and likely dor- facets. sal part of the centrum. A very weak ridge, which might The neural arch of ZIN PH 14/13 is similar to that of be a remnant of the spinodiapophyseal lamina, is pres- ZIN PH 7/13 in size but differs in a number of morpho- ent only on the left side (spdl?; Fig. 4C). logical details. The prezygapophyseal articular surfaces When the neural canal is horizontally oriented, are relatively smaller. The left facet is obliquely oriented the neural spine is inclined posteriorly at an angle of and gently convex, as in ZIN PH 7/13. The right facet ~36° from the vertical axis. There are high spinoprezyg- is smaller than the left one, almost vertically oriented, apophyseal laminae (sprl; Fig. 4A, C) between the pos- and flat. On both facets, the ventral most part is set at an terior end of the prezygapophyseal facets and the top of angle to the rest of the facet and is vertical. The promi- the neural spine (incompletely preserved). These lami- nent pre-epipophyses (= nonarticulating anterior pro- nae define a large space between the prezygapophyses cesses of D’Emic and Wilson (2011)) extends as rod-like and the anterior surface of the neural spine. On the projections anteriorly well beyond the prezygapophyseal lateral side, there is a considerable depression between facets (Fig. 5A, B). The ventral side of the prezygapophy- the spinoprezygapophyseal lamina and the ventral base seal processes is flat, with the prominent medial ridges of the postzygapophyses. In this place, the neural arch corresponding to the interprezygapophyseal laminae. is markedly constricted and the distance between the These ridges are horizontal, in contrast with the vertical bottoms of these depressions on opposites sides is just interprezygapophyseal laminae in ZIN PH 7/13, and ex- about 1 cm. This depression continues dorsally into a tend between dorsal margin of neural canal and the base shallower groove that extends along the anterior and of the prezygapophyseal facets. The prominent grooves dorsal margins of the postzygapophyseal facet. The spi- separate ventrally the prezygapophyseal facets from the nopostzygapophyseal laminae (spol; Fig. 4A, D) are very rest of the prezygapophyseal process. Posteriorly there short, shorter than the postzygapophyseal facet. is no space between the neural canal and the postzyg- The prespinal lamina (prsl; Fig. 4A) is well devel- apophyseal facets. There is a prominent hyposphenal oped, tapers ventrally and intersects the entire prespinal ridge along the ventral side of the interpostzygapophy- fossa (prsf). The prespinal fossa (prsf; Fig. 4A) is round seal lamina (Fig. 5C), similar to the ridge placed on ZIN and deep. The postspinal lamina (posl; Fig. 4D) is also PH 7/13 between the neural canal and the interpostzyg- wide and tapers ventrally. There is a deep cleft between apophyseal lamina. The postzygapophyseal articular the ventral end of postspinal lamina and prezygapophy- surfaces are about twice smaller than in ZIN PH 7/13 ses, the postspinal fossa (posf; Fig. 4D). Along the lat- but have a similar shape and similarly concave. The eral edges of the prespinal and postspinal laminae there prespinal, postspinal, spinoprezygapophyseal, and spi- are several irregular foramina leading to the pneumatic nopostzygapophyseal laminae are developed as in ZIN chambers within the neural spine: two on right side and PH 7/13. The prespinal fossa is relatively smaller and one on left side anteriorly and a single foramen on each shallower (Fig. 5A). Along the prespinal lamina there is side posteriorly, where the right foramen is distinctly one pneumatic foramen in the middle of the right side larger. The distal end of the neural spine is laterally ex- and much larger foramen at the distal end of the left side. panded. The top of the neural spine is saddle-shaped, The top of the neural spine is broken on the right side depressed in the middle and elevated laterally. revealing a large pneumatic chamber between prespinal The more posterior anterior caudal vertebra, ZIN and postspinal laminae separated by a midline septum PH 14/13, has preserved the neural arch and anterior from the chamber on the left side. There are three pneu- and posterior articular surfaces of the centrum (Fig. 5). matic foramina drastically decreasing in size distally, The contact area between the neural arch and the ante- along the left side of the postspinal lamina. On the right rior part of the centrum is partially preserved. The an- side, only proximal of these foramina is present. The terior articular surface is oval-shaped, with an incised distal end is laterally expanded, as in ZIN PH 7/13. In dorsal margin (Fig. 5D), as in ZIN PH 7/13. It is deeply contrast to the latter specimen, it is not saddle-shaped concave, but its deepest point, in contrast with ZIN PH but has a medial eminence formed by the prespinal and 7/13, is placed at the level of the middle of the neural postspinal laminae and lateral projections formed by arch. The posterior articular condyle of the centrum is spinoprezygapophyseal and spinopostzygapophyseal uniformly distributed. The size the cellsof is notgreater by14/13, revealed breakage, is solid, with many tiny cells (Fig. 6D). deep still but is small fossa Thepostspinal laminae. apophyseal spinoprezyg the between fossa prespinal a shallow roof, with canal anterior end neural and of the lamina the Thereprespinal considerableis a between space posteriorly. not and fused horizontal nearly nae are lami spinoprezygapophyseal The spine. neural of top theplate at horizontal expanded andlaterally flattened by separated laminae postspinal veloped and prespinal concave.ventrolaterally,are Therepoorly de but still facing developed left on side the is small, (Fig. 6C). It better is surface articular Thepostzygapophyseal face. sur articular prezygapophyseal flat and elongated, longitudinally apoorly is there defined, process right (Fig. 6B, C).anteriorly centrum beyond well the the On extending prezygapophyses long processes are rod-like 6C). The (Fig. arch neural of the posterior third the occupies which process, transverse of remnant the like completely is a ridge- which is there suture, closed, tral neurocen roof. the On dorsal canal terior end of neural level an at of placed is the the surface anterior articular thepoint of The deepest centrum. of the anterior half ventrally. separating triangular chevron small the facetsthat face has shallow anterior and posterior longitudinal grooves of centrum the is somewhat flattened the middle at and side is deeply arched inlateral view. The ventral surface laterallystricted and ventrally at middle. The the ventral than width their smaller (Table 1). The centrum is con height of are surfaces centrum the articular slightly is restricted from outer the margin by a flat area. The circumscribing posterior the condyle and condyle the condyle. As inZINPH 14/13,there is astrong ridge laterally (dorsally displaced) asymmetrical posterior deeply convex anterior and surface articular ball-like, 6).The centrum is articulation procoelous,with (Fig. median eminence and lateral projections. laminae. There are distinct depressions these between BIOLOGICAL COMMUNICATIONS , vol.62,issue1,January–March,2017|doi:10.21638/11701/spbu03.2017.102 PNW, posteriorwidthofneuralarch(betweenlateralmarginspostzygapophyses) PCW, posteriorwidthofcentrum PCH, posteriorheightofcentrum CL, centrumlength(ventral) ANW, anteriorwidthofneuralarch(betweenlateralmarginsprezygapophyses) ACW, anteriorwidthofcentrum ACH, anteriorheightofcentrum The bone structure of the centrum ZIN PH 7 and boneThe structure the centrumof ZIN PH 7 and arch thePH ZIN of 8/13 is to confined The neural acomplete caudalZIN PH middle 8/13 is vertebra Murtoi Formation(LowerCretaceous,Barremian?) Table 1.Measurements(inmm)ofcaudalvertebraeTengrisaurus starkovigen.etsp.nov. Mogoito,Buryatia,Russia; Measurements ------However, transverse the process is po inZINPH 7/13 of cupies arch, neural the all it is similar to third the caudal teroposteriorly transverse wide process, oc base which dorsoventrally. By relatively large arch neural and an caudal its because transverse process is not expanded not certainly first the secondor bra (ZIN PH 7/13) is ken but likely has asimilar bone structure. tic search with 10,000 random sequence addition searchtic with 10,000 random repli value of consistency rescaled indices (RC), and aheuris PAUP, characters the were reweighted by maximum the weighting analysis (Farris, 1969)was conducted. Using lution and recover any phylogenetic asuccessive signal, resolution among Titanosauriformes. To increase reso presented inTable 2. consensus The strict tree finds little parsimoniousduced 544 most trees; tree the statistics is ratchet replications pro weight analysis with 10,000 2007), and PAUP* 2002). The 4.0b10 (Swofford, equal- PRAP, parsimony ratchet analysis using PAUP (Müller, 1 forpendix scored the characters. gen. nov. scored can be by 18 characters (5.3 are ordered. Tengrisaurus 256, 267,298,299,and 301 115, 116,119,120,154,164,213,216,232,233,234,235, The multistate characters 12,58,95,96,102,106,108, 341 characters. uninformative Eleven characters (3.2 and (2014).The matrix includedLacovara 74 taxa et al. sauropods, on Titanosauriformes, focused presented by For phylogenetic the analysis recent we used matrix of Phylogenetic analysis britoi Baurutitan complete the caudal vertebrae of 17–18 in caudal series caudal series. 7/13within the a more posterior position of ZINPH (D’Emictrum and Wilson, 2011: fig. 6A1). This suggests caudal of N. australis it is on dorsal the of half cen the sitioned mostly on arch, neural the third inthe while than 1–3 mm. The centrum of ZIN PH 8/13 is not bro The centrum of ZIN PH 8/13 is than 1–3 mm. Neuquensaurus australis et al., (Salgado 2005:fig. 6C). Interpretation of vertebrae The character-taxon matrix was analyzed using Measurements Table 1.— See fitsthe 8/13 By overall the proportions ZINPH ZIN PH7/13 (Kellner et al., 2005:fig. 19). 13 68.3 94.7 ZIN PH14/13 124.6 127.2 119.0 73.0 — The holotype verte ZIN PH8/13 %). See Ap%). See 135.0 88.5 78.6 32.7 84.6 56.1 71.2 %). ------

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Fig. 7. Part of the strict consensus tree of 171 most parsimonious trees produced by PAUP reweighting character analysis (see text), showing the interrelationships of Titanosauria including Tengrisaurus gen. nov.

Table 2. Statistics for equal weight (PRAP and PAUP) and reweight (PAUP) analyses

Parameters Equal weight analysis Reweight analysis 1 Reweight analysis 2 Reweight analysis 3 N, number of trees 544 133 171 171 L, tree length 1056 300.9 298.5 298.5 CI, consistency index 0.389 0.636 0.649 0.649 HI, homoplasy index 0.611 0.346 0.355 0.355 RI, retention index 0.278 0.544 0.554 0.554 RC, rescaled consistency index 0.245 0.419 0.422 0.422

cates and TBR (tree bisection and reconnection) branch acter 55). The procoelous middle and posterior caudal swapping was performed. During reweighting 227 char- vertebrae is a synapomorphy for a more exclusive acters (66.6 %) got a weight of less than 1. Tree statis- within the Titanosauria: + (Isisau- tics stabilized after three successive runs of the reweight rus + ) (Wilson, 2002: character 134) or Al- analysis (Table 2). A section of the strict consensus of amosaurus + Saltasaurini (D’Emic, 2012: character 61). 171 trees obtained in the last analysis, showing the in- In our analysis the last character (210(3)) is present in terrelationships of Titanosauria, is illustrated in Fig. 7. a clade containing Epachthosaurus and more derived The phylogenetic analysis revealsTengrisaurus as a non- taxa, but reversed in . Lithostrotia was saltasaurid lithostrotian titanosaur. defined as a node-based taxon containing the most re- cent common ancestor of Malawisaurus and Saltasaurus Synapomorphies of Tengrisaurus and and all the descendants of that ancestor and diagnosed by strongly procoelous proximal caudal centra and the other titanosaurs presence of strong procoely in all except the most distal Centrum articulations of caudal vertebrae — In Ten- caudals (Upchurch et al., 2004: character 311). This phy- grisaurus the anterior and middle caudal vertebrae are logenetic definition of the clade contradicts its diagnosis strongly procoelous, with deeply concave anterior artic- because in Malawisaurus the middle and posterior cau- ular surface (cotyle) and a hemispherical posterior ar- dal vertebrae are not procoelous (Gomani, 1999, 2005). ticular “ball” (condyle). The procoelous anterior caudal Ventral depression on caudal centra — In the vertebrae is a synapomorphy of Titanosauria (Wilson, middle caudal vertebra of Tengrisaurus (ZIN PH 8/13) 2002: character 118) or Lithostrotia (D’Emic, 2012: char- the ventral centrum surface is round in the transverse most eusauropods caudal the transverse processes dis transverse process is reduced to aridge-like bump. In 8/13of Tengrisaurus caudal middle the ZINPH in the middle caudals middle in the (Powell, 1992:fig. 23). inSaltasaurus Also attinct least up caudal to 20th the (Campos et al., 2005). trend. In taxon, this transverse the process is clearly dis Trigonosaurus appeared by caudal 10(Wilson, 2002: character 115). example appeared by caudal 15,but insome titanosaurs, for ter 58). Rogers, 2005:character 235;D’Emic, 2012:charac isacter asynapomorphy of Titanosauriformes (Curry is located on anterior the of half centrum. the This char vertebra and caudal middle the vertebra (ZINPH 8/13) saurus rior and posterior chevron facets faceventrally. on caudal middle the vertebra (ZINPH 8/13) ante both facemostly posteriorly,vertebra (ZINPH 14/13) while rus (Santucci and 2011). Arruda-Campos, De saurus have asimilar condition, except of two species Aeolo caudal vertebrae of Tengrisaurus sally more derived taxa. and containing forsynapomorphy clade the a 2011).Wilson, 196:1 is character the analysis our In cluding in fossa, have ventral that the number of titanosaurs are analysis). our ridges presentin a The ventrolateral (character fossa 196 in aventral bound that centrum the presence on of the ventrolateral ridges correlated with thosaurus Epach in but parallel evolved in moreand taxa, derived Trigonosaurus containing forsynapomorphy clade the petosaurus yarosaurus Mag node containing the reversed in is character the 230), Rogers (2005: character by but Curry analysis the in Saltasauridae phy + Lirainosaurus for clade the asynapomor is centra caudal middle a hollow the in 2012: 54). D’Emic, character Presence of such ter 132; charac 2002: napomorphy (Wilson, of Titanosauria hollow considered was asy longitudinal ventral with centra caudal middle Anterior and facets. chevron the anteriorly posteriorly, grooves and between gitudinal PH 14/13 lon incompletely is It shallow has preserved. ZIN vertebrae anteriorcaudal the of sion.centrum The groove or depres alongitudinal without cross-section, BIOLOGICAL COMMUNICATIONS , vol.62,issue1,January–March,2017|doi:10.21638/11701/spbu03.2017.102 the posterior the chevron facetsof anterior the caudal Caudal transverse process transverse disappearance Caudal Neural arch position on thecentrum facing posteriorly facets Chevron Apex of dor centrum posterior displaced condyle — This condition is present in anterior and middle the neural archneural the of holotype the anterior caudal , where apex the is to closer centrum the midline (D’Emic and and (D’Emic Neuquensaurus and Alamosaurus Opisthocoelicaudia and Malawisaurus and . In our analysis this character (209:1) character this a is analysis our . In , Malawisaurus represents departure astriking from this the transverse the process is not reduced , and Alamosaurus and . This character is partially is partially character . This . Most lithostrotians — In Tengrisau — In , and Ra , and , it dis Tengri — In the the ------in titanosauriforms (Wilson and Upchurch, 2009;Whit vertebrae of variouscervical sauropods and is common prezygapophyseal articulation facet.It is present on the prezygapophysisthe on placed sideopposite the to the apophyseal et al., 2013). Loeuff fossa (Le rus 1999).In Normanniasau apophyseal fossa (Sanz et al., rainosaurus anteriorlyplaced to postzygapophyseal the facet.In Li dorsal inposition compared with holotype the vertebra, 2011). The interzygapophyseal fossa is usually more 2007;Filippi et al., et al., 2006;Casal tucci and Bertini, spinal fossa in anterior caudal vertebrae con has been postzygapophyseal lamina ventrally. Presence of a post spinopostzygapophysealthe laminae laterally and inter tioned on posterior the sideof spine neural the between (203:1) isacter present infew not-related taxa. terior caudals of Tengrisaurus hyposphenal2013). Aweak ridge is present an inboth al., al., 2004; Mannion et Martin, 2003;Upchurch et most rebbachisaurids (Upchurch, 1998;Upchurch and many sauropods except derived somphospondylans and 1998). It is present anterior inthe caudal vertebrae of apophyses to top the of canal neural the (Upchurch, tends from ventral the junction midline of postzyg the postzygapophyseal facetsis less pronounced. Tengrisaurus de Azevedo, 1999).Asimilar condition in is observed prezygapophyses of following the vertebra (Kellner and forming encloses that the a“half-cylinder” partially form apronounced concavity, extends which ventrally apophyses inanterior caudals are relatively large and Gondwanatitan by D’Emic and Wilson (2011). sidered as an autapomorphy of Neuquensaurus australis rior processes on caudal middle the vertebrae were con apophyseal process. articular This non-articulating ante forms an anterior process projecting beyond prezyg the pre-epipophysis 14/18the is more developed and PH on holotype the caudal vertebra of Tengrisaurus 2011;Tschopplock, 2015).Such ridge is present et al., mantisaurus fossa, is presentyseal anterior inthe caudals of Ada pronounced. Asimilar fossa, interzygapoph the termed fossa this is muchposterior caudal, less ZIN PH 14/17, anteroventral to postzygapophyseal the facet.In amore transverse the between process and spine, neural the spine González Riga, 2003;Powell, Riga, González 2003;Gomani, 2005;San , and Petrobrasaurus there is aforamen position inthe of interzyg the Pre-epipophysis Postspinal fossa Hyposphenal ridge Postzygapophyses concave Fossa between the transverse process and neural process thetransverse Fossa and neural between — In holotype the vertebra there fossa is adeep there is alamina intersecting interzyg the , , though inthat taxon concavity the of the Aeolosaurus, Lirainosaurus Aeolosaurus, the articular surfaces of surfaces postzyg the articular the 15 — Pre-epipophysis is aridge on — The postspinal— The posi fossa is — The ridgehyposphenal ex . In our analysis char this — In (Sanz et al., 1999; (Sanz et al., Aeolosaurus , Malawisaurus . In ZIN and and ------,

PALAEONTOLOGY 16 BIOLOGICAL COMMUNICATIONS, vol. 62, issue 1, January–March, 2017 | doi: 10.21638/11701/spbu03.2017.102 sidered a synapomorphy for the clade containing Ma- sponge (both plastic tool and its living prototype) the lawisaurus, Nemegtosaurus, and (Curry internal cells are very small, usually not greater than Rogers, 2005: character 221). 1 mm. The centrum bone structure of the caudal verte- Neural spine transverse breath — In Tengris- brae in Tengrisaurus looks exactly as in a sponge, with aurus the neural spine of the holotypic vertebra is not small internal cells, not greater than 1–3 mm. This con- complete laterally; the preserved transverse breadth is dition is considered here the solid bone structure. We ~1.5 times greater than the anteroposterior length. In refrain from using the term “spongy bone” to avoid con- the other anterior caudal vertebra, ZIN PH 14/13, the fusion. The bone structure of the neural arch in caudal apex of the neural spine is complete from the left side. vertebrae of Tengrisaurus, at least partially, is camellate It has the transverse breadth ~2.1 times greater than (= somphospondlyus), with large internal cells. the anteroposterior length. The neural spine transverse The pneumatization of the caudal centra have in- breadth greater than anteroposterior length in anterior creased in the evolution of . In Saltasaurus, caudals was considered a synapomorphy for the clade Rocasaurus, and Neuquensaurus, the caudal centra have Isisaurus + Saltasauridae (Wilson, 2002: character 126). camellate bone structure (Powell, 1992; Salgado and The neural spine of anterior caudals is expanded later- Azpilicueta, 2000; Cerda et al., 2012; García and Sal- ally in Aeolosaurus, Adamantisaurus, and Trigonosaurus gado, 2013). (Campos et al., 2005; Santucci and Bertini, 2006; San- tucci and De Arruda-Campos, 2011). In our analysis General discussion this character (199:1) is a synapomorphy for the clade including Tengrisaurus and more derived taxa. The understanding of the evolutionary history of Titano- Neural spine inclination — In Tengrisaurus the sauria is hampered by the lack of an explicit and reliable neural spine is inclined posterodorsally in the holotype phylogenetic hypothesis. The content of Titanosauria vertebra and more posteriorly in ZIN PH 14/13. In the and the phylogenetic relationships within this taxon middle caudal ZIN PH 8/13, the neural spine is very greatly varies between studies (D’Emic, 2012; Mannion short and its inclination is difficult to assess. Salgado et al. et al., 2013). The most recent comprehensive study of the (2005) considered a strongly posteriorly directed neural titanosaurian interrelationships based on the Bayesian spine of caudal vertebrae posterior to the first caudal a analysis revealed quite different phylogeny of the group synapomorphy for the Saltasaurinae. In other titanosaurs (Gorscak and O‘Connor, 2016). This analysis postulate the neural spine is vertical, or even anteriorly inclined. Gondwanan origin of the Titanosauria in the Early Cre- Neural spine anterior edge position — In the taceous in South America. However, the analysis does middle caudal vertebra of Tengrisaurus, ZIN PH 8/13, not include taxa from the Early Cretaceous of Asia, like the sloping anterior margin of the neural spine is placed possible non-saltasaurid lithostrotian from mostly anterior to the postzygapophyseal facet. The an- the Aptian of China (You et al., 2008; Averianov and terior border of the neural spine located posteriorly with Sues, 2017). Tengrisaurus gen. nov. is another Asian non- respect to the anterior margin of the postzygapophyses saltasaurid lithostrotian which age (Barremian-Aptian?) in the middle caudals has been considered a synapo- is coeval with the other oldest records of Titanosauria. morphy for Saltasaurinae (Salgado et al., 1997). Presence of derived lithostrotian titanosaurs in the Early Neural spine pneumatic openings — In the ante- Cretaceous of Asia suggests earlier dates of divergence rior caudal vertebrae of Tengrisaurus there are irregu- of main titanosaurian and possible origin of the lar pneumatic openings on the neural spine along the group in Asia. lateral margins of the prespinal and postspinal laminae. Similar openings in anterior and middle caudal verte- Acknowledgements brae have been reported for , Baurutitan, Futa- We thank N. G. Borisova and G. I. Sazonov for the logistical support, lognkosaurus, Neuquensaurus, and Saltasaurus (Powell, A. V. Abramov and A. I. Starkov for the generous assistance during the field 2003; Martinelli and Forasiepi, 2004; Kellner et al., 2005; work in 1998 and 1999. We are grateful to I. A. Cerda, M. D. D’Emic, and Calvo et al., 2008; D’Emic and Wilson, 2011). an anonymous reviewer for reviewing the paper and useful suggestions. Osseous tissue structure — The term spongy bone is sometimes used as a synonym of the camellate bone References structure (Wilson and Sereno, 1998; García and Salgado, Averianov, A. O., and Skutschas, P. P. 2000. Kompleks pozvonochnykh 2013). Wilson (2002) distinguished between the spongy rannego mela Zabaikalya [A vertebrate assemblage from the Early bone, with centimetre-scale internal cells, “semicamel- Cretaceous of Transbaikalia (locality Mogoito)]; pp. 357–358 in late” according to Wedel et al. (2000), and camellate to A. V. Komarov (ed.), Materials of the Regional Conference of the Ge- ologists of Siberia, Far East and North East of Russia. GalaPress, somphospondylous bone structure, with subcentimetre- Tomsk. scale cells. Such definition of the spongy bone as hav- Averianov, A. O., and Skutschas, P. P. 2009. Additions to the Early Cre- ing centimetre-scale internal cells is confusing, as in a taceous dinosaur fauna of Transbaikalia, eastern Russia. Proceed- ed, I. Cerda, Campos, D. Casal, G. Curry Rogers, K. Rogers, Curry J. Calvo, ’mc M. D’Emic, M. D’Emic, Averianov,A. Ivanov,B. P.O‘Connor, and E., Gorscak, B. Riga, González J. Farris, Dmitriev,G. Dmitriev,G. Averianov, A. BIOLOGICAL COMMUNICATIONS , vol.62,issue1,January–March,2017|doi:10.21638/11701/spbu03.2017.102 Gomani, E. E. Gomani, García, R. L. Filippi, tologische Zeitschrift from South in sauropoddinosaurs pneumaticity America. Argentina. 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Appendix 1. Characters scored for Tengrisaurus starkovi gen. et sp. nov.

188(0): Caudal bone texture: solid. 189(1): Caudal transverse processes: disappear by caudal 15. 193(3): Anterior caudal centra (excluding the first), articular face shape: procoelous. 196(0): Anterior and middle caudal vertebrae, ventrolateral ridges: absent. 197(0): Anterior and middle caudal vertebrae, triangular lateral process on the neural spine: absent. 199(1): Anterior caudal neural spines, transverse breadth: greater than anteroposterior length. 200(1): Anterior caudal transverse processes, proximal depth: deep, extending from centrum to neural arch. 203(1): Anterior caudal vertebrae, hyposphene ridge: present. 205(0): Anterior caudal neural arches, spinoprezygapophyseal lamina (sprl): absent, or present as small short ridges that rapidly fade out into the antero- lateral margin of the spine. 206(0): Anterior caudal neural arches, spinoprezygapophyseal lamina (sprl)-spinopostzygapophyseal lamina (spol) contact: absent. 207(1): Anterior caudal neural arches, prespinal lamina (prsl): present. 208(0): Middle caudal centra, shape: cylindrical. 209(0): Anterior and middle caudal centra, ventral longitudinal hollow: absent. 210(3): Middle caudal centra, articular face shape: procoelous. 211(1): Middle caudal vertebrae, location of the neural arches: on the anterior half of the centrum. 212(0): Middle caudal vertebrae, height of the pedicels below the prezygapophysis: low with curved anterior edge of the pedicel. 213(2): Middle caudal vertebrae, orientation of the neural spines: slightly directed posteriorly. 215(0): Middle caudal vertebrae, ratio of centrum length to centrum height: less than 2, usually 1.5 or less.