sign in sign up
<<
Home , Irritator, Khok Kruat Formation, Sao Khua Formation, Segisaurus, Siamotyrannus, Spinosauridae

Naturwissenschaften DOI 10.1007/s00114-012-0911-7

ORIGINAL PAPER

The first definitive Asian spinosaurid (Dinosauria: ) from the early of Laos

Ronan Allain & Tiengkham Xaisanavong & Philippe Richir & Bounsou Khentavong

Received: 25 November 2011 /Revised: 19 March 2012 /Accepted: 22 March 2012 # Springer-Verlag 2012

Abstract Spinosaurids are among the largest and most spe- from . Cladistic analysis identifies Ichthyovenator as a cialized carnivorous . The of their member of the sub- Baryonychinae and suggests a crocodile-like , stomach contents, and oxygen isotopic widespread distribution of this clade at the end of the Early composition of the bones suggest they had a predominantly Cretaceous. tashouikensis from the Creta- piscivorous diet. Even if close relationships between spino- ceous of Inner Mongolia, and an ungual phalanx from the saurids and Middle megalosaurs seem well estab- Upper Jurassic of Colorado are also referred to spinosaurids, lished, very little is known about the transition from a extending both the stratigraphical and geographical range of generalized large tetanuran to the specialized morphol- this clade. ogy of spinosaurids. Spinosaurid remains were previously known from the Early to of North , Keywords Cretaceous . Savannakhet basin . Theropoda . , and . Here, we report the discovery . Asia of a new spinosaurid theropod from the late Early Creta- ceous Savannakhet Basin in Laos, which is distinguished by an autapomorphic sinusoidal dorsosacral sail. This new Introduction , Ichthyovenator laosensis gen. et sp. nov., includes well-preserved and partially articulated postcranial remains. The spinosaurids are among the most bizarre dinosaurs. The Although possible spinosaurid teeth have been reported morphology of their superficially crocodile-like skull from various localities in Asia, the new (Taquet 1984; Charig and Milner 1997; Sereno et al. 1998; taxon I. laosensis is the first definite record of Spinosauridae Sues et al. 2002; Dal Sasso et al. 2005), as well as the stomach contents of the of walkeri Communicated by: Robert Reisz (Charig and Milner 1997), the biomechanical data (Rayfield et al. 2007), and the oxygen isotopic composition of the Electronic supplementary material The online version of this article (doi:10.1007/s00114-012-0911-7) contains supplementary material, bones (Amiot et al. 2010) of spinosaurs suggest they had a which is available to authorized users. predominantly piscivorous diet, even if it appears that they also fed on ornithopods (Charig and Milner 1997)and R. Allain (*) : P. Richir Département Histoire de la Terre, Centre de Recherches sur la (Buffetaut et al. 2004). Spinosauridae is mainly Paléobiodiversité et les Paléoenvironnements (CR2P), Muséum known from the Early Cretaceous of National d’Histoire Naturelle, Europe (Charig and Milner 1986) and from the late Early UMR 7207 du CNRS CP 38, 57 rue Cuvier, and early Late Cretaceous of (Stromer 1915; 75231 Paris cedex 05, France e-mail: [email protected] Sereno et al. 1998; Taquet and Russell 1998; Sues et al. : 2002). Furthermore, the first-described spinosaurid, Spino- T. Xaisanavong B. Khentavong saurus aegypticus, which was destroyed during World War Science and Technology Office, Savannakhet Museum, II in an Allied bombing raid of Munich, is famous for its Khanthabouly Road, Thamouang Village, Savannakhet, Kaisonphomvihan DistrictPO Box 739, République hypertrophied dorsal neural spines forming a high median Démocratique Populaire Lao sail on its back (Stromer 1915, 1934; Smith et al. 2006). Naturwissenschaften

Except for the close relationships with Middle Jurassic “hunter”). The generic name is in reference to the predom- megalosaurs (Sereno et al. 1998; Allain 2002; Holtz et al. inantly piscivorous diet of Spinosauridae. The specific name 2004; Benson 2010), early evolution of the Spinosauridae is derived from the name Laos. remains enigmatic as the first appearance datum of the taxon is in Early Cretaceous deposits. Holotype Partially articulated skeleton, curated at the Dino- The presence of spinosaurid theropods in Asia has been saur Museum, Savannakhet (MDS BK10-01 to 15), includ- tentatively reported on the basis of several isolated teeth ing the antepenultimate dorsal , the neural spine of from Cretaceous units in Thailand (Buffettaut and Ingavat the last dorsal vertebra, the first and the second caudal 1986), China (Buffetaut et al. 2008; Hone et al. 2010), and vertebrae, five incomplete sacral vertebrae found in articu- Japan (Hasegawa et al. 2003). An as-yet-undescribed partial lation, ilia, the right pubis, ischia, and a posterior dorsal rib postcranial skeleton from the (Figs. 1, 2. 3 and 4) (See ESM, for a complete description of of Thailand has also been referred to Spinosauridae (Milner the bones). et al. 2007; Brusatte et al. 2010). Our recent excavations in the Early Cretaceous “Grès supérieur” Formation of the Horizon and localit Ban Kalum, Tang Vay area, Savanna- Savannakhet Basin of southern Laos recovered the skeleton khet Province, Laos; “Grès supérieurs” Formation; Early of a new unquestionable spinosaurid that exhibits an ex- Cretaceous (Hoffet 1937;Allainetal.1997, 1999). The traordinary dorsosacral sail. The presently known postcra- “Grès supérieurs” Formation is considered here the lateral nial material was found in close association within a layer of equivalent of the Khok Kruat and Phu Pan formations in red sandstone, on a surface area of less than 2 m2. Pending neighbouring Thailand and is probably late to further excavations, a preliminary account of the postcranial early in age (Buffetaut 1991; Allain et al. 1999; skeleton of this new spinosaurid is described here. Sha 2007; Racey and Goodall 2009). The non-marine Cre- Dinosaurs from Southeast Asia have been known since taceous bivalve Trigonioides kobayashi–Plicatounio suzuki the 1930s based on the work of the French geologist J. H. assemblage (Hoffet 1937) which is the only known assem- Hoffet in the Savannakhet Basin, in Laos (Hoffet 1942; blage recovered in Tang Vay area suggests that Ichthyove- Hoffet 1944; Taquet 1994). It was not until the 1980s that nator is Aptian in age (Allain et al. 1999;Sha2007). joint Thai–French projects led to new discoveries of verte- brate assemblages from various formations of the western Diagnosis A baryonychine spinosaurid with the following part of the Khorat Plateau in Thailand (e.g., Ingavat et al. : a dorsosacral sinusoidal sail (Figs. 2 and 1978; Buffetaut et al. 2009). In 1991, a French–Lao team 6); penultimate dorsal neural spine is 410 % of centrum resumed research in the “Couches Rouges” from the Early length with anterodistal finger-like process (Fig. 1); fan- Cretaceous Savannakhet Basin of Laos. Since then, skeletal shaped sacral neural spines 3 and 4; transverse processes remains and tracks of sauropod, theropod and ornithischian of first caudal vertebra with sigmoid profile in dorsal view; dinosaurs, as well as turtles, bivalve, and plant have deep prezygapophyseal centrodiapophyseal fossae the first been collected from the Tang Vay area (Plate 1A–B) (Taquet caudal vertebra (Fig. 3); long iliac blade with ilium/pubis et al. 1995; Allain et al. 1997, 1999; de Broin 2004). Among length ratio highest than in any other theropods. Moreover, them are the type specimens of the basal titanosauriform I. laosensis is characterized by some features unknown in sauropod dinosaur Tangvayosaurus hoffeti (Allain et al. other tetanuran theropods: posterior dorsal ribs articulated 1999) and the turtle Shachemys laosiana (de Broin 2004). with sternal complex (ESM); proximal pubic plate with Further locality information is given in the electronic sup- obturator and pubic notches (Fig. 4); large ischial plate with plementary material (ESM). ischial foramen; and mediolaterally flattened ischial shaft.

Systematic palaeontology Description Dinosauria Owen 1842 Theropoda Marsh 1881 The 12th dorsal vertebra is one of the most unusual dorsal Gauthier 1986 vertebrae known in theropods except for those of the lost holotype of aegyptiacus (Fig. 1). The amphi- Spinosauridae Stromer 1915 coelous centrum is slightly longer than high, but wider than Baryonychinae Charig and Milner 1986 long. The neural arch is characterized by the presence of Ichthyovenator laosensis gen et sp nov. accessory centrodiapophyseal laminae and a set of faint ridges that joins the base of the transverse processes to the Etymology The generic name is derived from ichthos (an- neural spine. The hypertrophied neural spine is neither in- cient Greek word for fish), and from venator (Latin word for clined anteriorly nor posteriorly, as in Spinosaurus (Stromer Naturwissenschaften

Fig. 1 Twelfth dorsal vertebra (BK 10-01) of I. laosensis. a Lateral posterior centrodiapopyseal lamina, pisl distal extent of the posterior view. b Posterior view. c Anterior view. d Dorsal view. e Detailed interspinous ligament scar, podl postzygodiapophiseal lamina, poz lateral view (with the distal part of the neural spine removed). aisl postzygapophysis, pp parapophyses, ppdl parapodiapophyseal lamina, distal extent of the anterior interspinous ligament scar, al accesory prdl prezygodiapophyseal lamina, prpl prezygoparapophyseal lamina, lamina, bw basal webbing, di diapohysis, flap finger-like anterior prz prezygapophysis. Scale bars equal 10 cm process of the neural spine, ha hypantrum, hs hyposphene, pcdl

1915). The neural spine/centrum length ratio (410 %) is spine is marked by a 3-cm-long finger-like process, which is significantly less than in Spinosaurus, nearly equal to that not observed on the sacral neural spines of Ichthyovenator observed in Becklespinax (Naish 2011), but greater than in and unknown in other theropods. The distal part of the any other known theropods (see ESM for selected measure- neural spine has been deformed, so that it curves laterally ments). The transverse processes are laterally directed. The in anterior and posterior views. distal length of the neural spine process is 3.5 times its basal The last dorsal vertebra comprises only the neural spine length, resulting in an isosceles trapezoidal spine, rather (Fig. 2), which was preserved appressed against the right than a rectangular spine as in other spinosaurids, but also ilium. The spine is broken both proximally and distally and Becklespinax and (Owen 1855;Stromer it is uncertain that it was as much expanded as the neural 1915; Sereno et al. 1998; Ortega et al. 2010). Moreover, spine of the 12th dorsal vertebra; however, it presents the the anterodistal corner of the antepenultimate dorsal neural same prominence, seen on D12, which marks the distal

Fig. 2 Reconstruction and morphology of the sinusoidal dorsosacral sail of the holotype of I. laosensis (MDS BK10-01 to BK10-08). Twelfth and thir- teenth dorsal vertebrae, sacral vertebrae, and first and second caudal vertebrae in left lateral view. cd1-2 first and second caudal vertebrae, d12-13 twelfth and thirteenth dorsal vertebrae, s2-3 centra of the second and third sacral verte- brae, sp1-5 neural spines of the first–fifth sacral vertebrae. Scale bar equals 10 cm Naturwissenschaften

Fig. 3 First caudal vertebra (BK 10-02) of I. laosensis. a Anterior view. b Posterior view. c Left lateral view. d Dorsal view. cf chevron facet, ia artic- ulation for ilium, ns neural spine, poz postzygapophysis, prsf prespinal fossa, tp trans- verse process, prcdf prezygapo- physeal centrodiapophyseal fossa, prpl prezygoparapophy- seal lamina, prz prezygapophy- sis. Scale bar equals 10 cm

extent of the interspinous ligament on the posterior surface of Although most of the sacral centra have been destroyed the spine (Figs. 1 and 2). If we infer the position of the broken by erosion, all sacral spines are complete distally and were last neural spine from this prominence, the latter must be as found still in articulation in the same block (Fig. 2). The high as the D12 neural spine, and confirms that at least the second and third sacral centra are firmly fused to one an- D12 and D13 of Ichthyovenator supported a dorsal sail. other but the is still evident between the two centra. The height of the sacral neural spines increases from the first to the fourth vertebra and then decreases again at the level of the last sacral vertebra. Adjacent sacral spines are not fused to one another distally nor in contact as in , and unlike the condition observed in most other theropods. The first sacral neural spine is morphologically very different of the remaining sacral spines. It is very low compared with the posterior dorsal and other sacral neural spines, and is re- sponsible of the sinusoidal shape of the reconstructed sail of Ichthyovenator (Figs. 2 and 6). Thus, the latter could be subdivided into a sacral sail including sacral vertebrae S2 to S5 and the first two caudal vertebrae, and a tall dorsal sail including at least dorsal vertebrae D12 and D13. At present, the anterior extent of the dorsal sail of Ichthyovenator is unknown. In any case, the morphology of the sail is clearly distinct from that in Suchomimus in which the much deeper sail arches to an apex over the (Sereno et al. 1998), Fig. 4 of the holotype of I. laosensis. a reconstruction of the and from that in Baryonyx in which the dorsal sail is incip- pelvis in left lateral view based on the left ilium (MDS BK10-09) and ient and the sacral one is unknown (Charig and Milner reversed images of the right ischium (MDS BK10-13) and pubis (MDS 1997). Based on the disparity between the morphology of b BK10-11) (see the ESM). distal end of the right pubis in distal view. the differently elongated neurapophyses observed in thero- The white arrow points anteriorly. ac acetabulum, if ischial foramen, il ilium, is ischium, on obturator notch, pn pubic notch, pu pubis. Scale pod dinosaurs (Stromer 1915; Stovall and Langston 1950; bar equals 10 cm Sereno et al. 1998; Smith et al. 2006; Ortega et al. 2010) and Naturwissenschaften

Fig. 5 Time-calibrated result of the phylogenetic analysis showing the group of (Suchomimus + Baryonyx). For details of phylogenetic anal- interrelationships of I. laosensis within theropoda. Numerous synapo- ysis, see text and ESM morphies place Ichthyovenator within the Baryonychinae as the sister- recent histological investigations on hyperelon- ornament rather than in or energy storage gate neural spines (Huttenlocker et al. 2010), we postulate (Bailey 1997). here that the sail of Ichthyovenator functioned in display The first two caudal centra are amphicoelous and sig- or as a sexually selected and/or a recognition nificantly wider than long. The caudal spines are still elongated and form the posterior portion of the sacral sail. They are inclined posteriorly at about 30° from the verti- cal. There is no rugosity along the anterior and posterior edges of the neural spines. Prespinal and postspinal fossae are restricted to the region above the base of the neural spines. The robust and elongate transverse processes are low on the neural arch and extend posterolaterally and dorsally. The transverse processes of the first caudal ver- tebra have an unusual sigmoid shape in dorsal view (Fig. 3). Prezygodiapophyseal and anterior centrodiapo- physeal laminae are well marked on both the lateral side of the anterior part of the neural arche and the anterior edge of the transverse processes of the first caudal verte- brae. They define a deep prezygapophyseal centrodiapo- Fig. 6 Hypothetical live reconstruction of I. laosensis physeal fossa unknown in other theropods (Fig. 2). Naturwissenschaften

Only a complete posterior dorsal rib has been collected, even if the pubis/ischium length ratio is similar to that in close to dorsal vertebra D12. The rib head is similar to those and (see ESM). The of other medium-sized-to-large theropods. The rib shaft anteroventral margin of the ischial plate is continuous, with- exhibits a strong curvature, with a high shaft-neck angle out an obturator notch separating the ischial plate from the (see ESM). The rib shaft is subcircular in cross section ischial shaft as in Baryonyx. The ischial plate is perforated throughout its length. Its notched distal tip flares slightly by a large, suboval obturator foramen, which is elsewhere both mediolaterally and anteroposteriorly, relative to the only known in (Camp 1936; Carrano et al. 2005) adjacent portion of the shaft. This morphology is rare in and the basal tyrannosauroid (Xu et al. 2006). other theropods, in which the distal end of the posterior dorsal ribs is barely expanded or tapers to a point (O'Connor 2007). This indicates that the posterior dorsal ribs of Ich- Discussion thyovenator articulated with the sternal complex (sternal ribs or cartilages). Morphologically, the pelvis of Ichthyovenator is clearly The blade-like ilium closely resembles those of other different from that of the only other adequately known large large theropods although it is distinctly longer relative to theropod from the Lower Cretaceous of Southeast Asia, other pelvic elements (Fig. 4). Its preacetabular process is isanensis from the in significantly shorter than the postacetabular part. Although Thailand (Buffetaut et al. 1996). For example, Siamotyran- it is broken at its base, a medial preacetabular shelf is clearly nus has a more robust ilium, a pubis with a pubic boot and present (see ESM) on the medial surface of the ilium and an obturator process on the ischium (Buffetaut et al. 1996). forms the medial boundary of the preacetabular fossa. The We investigated the systematic position of I. laosensis using medial shelf has been reported as a synapomophy of Neo- a dataset of 178 osteological and dental characters and 28 venatoridae (Benson et al. 2010), but is plesiomorphically taxa. The data matrix was processed with NONA (Goloboff present in archosaurs (Hutchinson 2001). The ilium/pubis 1999) and the interface Winclada (Nixon 1999–2002). ratio (1.46) is the highest among known large theropods. Minimum-length trees were generated using the traditional The shaft of the pubis is mediolaterally flattened proximally heuristic Multiple TBR + TBR search options with a max- at the level of the obturator foramen, whereas it is dorso- imum of 1,001 trees kept, and 1,000 replicates. This analysis ventrally flattened at the level of the pubic foramen. The resulted in a single most parsimonious tree (tree length0 morphology of the pelvis of Ichthyovenator, and observa- 422, CI00.51, RI00.72) (for details refer to the ESM). tions of a similar morphology in basal allosauroids (Currie In agreement with many studies (Rauhut 2003; Carrano and Zhao 1994) and coelurosaurs (Xu et al. 2006), suggests et al. 2005; Smith et al. 2007), the current analysis that the reduction of the puboischial plate within Tetanurae recovers (including ) outside results from mosaic evolution. The unusual proximal pubic a monophyletic comprising + Teta- plate has two posteroventrally open features: the obturator nurae (Fig. 5). Within the latter clade, Spinosauroidea and notch proximally and the pubic notch or fenestra mediodis- represent successive sister taxa to Coeluro- tally (Hutchinson 2001). The latter is completely enclosed in sauria as in nearly all recent analyses (Sereno et al. 1998; basal theropod taxa such as Syntarsus, , Pro- Allain 2002; Holtz et al. 2004b; Smith et al. 2007; Benson ,andCoelophysis (Tykoski and Rowe 2010). Relationships within Allosauroidea are well resolved 2004), but opens ventrally to form what is named here the in our analysis but differ from the results of other studies pubic notch in Ichthyovenator, Segisaurus, Dilophosaurus, (Rauhut 2003; Holtz et al. 2004b; Smith et al. 2007; Brusatte and . A large pubic foramen is present on the and Sereno 2008;Xuetal.2009) and put the accent on the pubic apron surface. The distal end of the pubis has a lack of any consensus on the phylogenetic affinities of the distinctive L-shape in distal view and closely resembles allosauroids, even in analyses performed by a same author those of Baryonyx (Charig and Milner 1997) and Suchomi- (e.g., Benson 2010; Benson et al. 2010). Monolophosaurus is mus (Sereno et al. 1998) (Fig. 4). The ischium has not the recovered as the most basal allosauroid (Rauhut 2003; fairly typical Y-shaped outline and instead displays a well- Holtz et al. 2004b) rather than the sister taxon to Neo- developed proximal ischial plate, not observed in other tetanurae (Smith et al. 2007) or as a member of Spinosaur- tetanuran theropods (Hutchinson 2001). Moreover, the is- oidea (Benson et al. 2010). and are chial midshaft is much deeper dorsoventrally than wide recovered as sister taxa but are more closely related to mediolaterally in a unique way. On the other hand, the than to . ischial symphysis is unexpanded as in Monolophosaurus The current analysis places Ichthyovenator within Spino- (Zhao and Currie 1993; Zhao et al. 2010) and sauridae as the to the remaining baryonichines (Currie and Zhao 1994). The ischium is shorter than the Suchominus and Baryonyx (Fig. 5). It is noteworthy that pubis, more than in any other basal tetanuran theropods, except for the length of the dorsal neural spines, Naturwissenschaften

Spinosauridae is only supported by cranial and dental un- Spinosaurus and Ichthyovenator form a polytomy with Bar- ambiguous synapomorphies. Because substantial postcrani- yonychinae at the base of Spinosauridae in the strict con- al material are only known for baryonychines, identifying sensus of five most parsimonious trees (SEM). Thus, unambiguous spinosaurid synapomorphies is not yet possi- Chilantaisaurus is considered here a second Asian repre- ble, but another 11 synapomorphies could support Spino- sentative of Spinosauridae. Based on radioisotopic dating on sauridae under Fast Optimization (for character distribution, basalts from the underlying Suhongtu Formation, the Ulan- refer to ESM). Similarly, Spinosaurinae differs from Baryo- suhai Formation is at least younger than the Turonian, about nichinae only in dental features, and the separation between 92 Ma (Kobayashi and Lü 2003). This extends the strati- the subfamilies may not be as clear as usually supposed. The graphic range of Spinosauridae, and Chilantaisaurus is then following postcranial features identified in Ichthyovenator the youngest known member of the clade. characterize Baryonychinae in general: presence on the We concur with Buffettaut et al. (2008) that the limited posterior dorsal vertebrae of accessory centrodiapophyseal sampling and the nearly worldwide distribution (Europe, laminae and of basal webbing on the neural spine; medio- Asia, Africa, and South America) of spinosaurids at the laterally expanded pubic distal end (Sereno et al. 1998). end of the Early Cretaceous prevent any clear paleobiogeo- Ichthyovenator is the first definite spinosaurid known in graphic conclusions (Sereno et al. 1998; Holtz et al. 2004a). Asia because the phylogenetic identity of previously If one accepts our hypothesis of phylogenetic relationships reported Asian spinosaurid teeth has been questioned and the most common version of the breakup sequence of (Buffetaut and Ingavat 1986; Sereno et al. 1998;Sues Pangaea, in which Asia becomes isolated first (Russell et al. 2002; Holtz et al 2004b;Buffetautetal.2008). 1994; Smith et al. 1994), a spinosaurid distribution across The discovery of Ichthyovenator also underscores the Pangaea before the Late Jurassic is nevertheless likely. In need for more sampling and description of spinosaurid that case, both the absence of spinosaurids in North America postcranial material, compared with highly specialized cra- and the lack of clearly identified spinosaurid material from nial material, to understand the early evolution of the group strata older than the Early Cretaceous may be regarded as and confirm the close relationships between megalosaurs problematic. Galton and Jensen (1979: Fig. 1M) referred a and spinosaurids. Surprisingly, Ichthyovenator shares nu- large ungual phalanx of the first manual digit to Torvosau- merous unusual pelvic features including a pubic notch, an rus, in the original description of the taxon. However, this enclosed ischial foramen and a flattened ischial shaft with specimen, BYU 2020 (collections of Brigham Young Uni- Segisaurus halli (Camp 1936; Carrano et al. 2005). Segi- versity), was found isolated at the Calico Gulch Quarry, saurus from the late of 195 km from the Dry Mesa Quarry, which has yielded the Arizona is generally considered a member of Coelophysoi- holotype and most of the referred specimens of dea (Rauhut 2003; Tykoski and Rowe 2004; Carrano et al. (Galton and Jensen 1979; Britt 1991). Britt (1991) acknowl- 2005). As previously stated, Segisaurus possesses a few edged that the referral of this ungual phalanx to Torvosaurus derived characters unusual for a coelophysoid, including a was only tentative, but many authors subsequently used the in lateral view straight humeral shaft, short posterior dorsal presence of an enlarged manual ungual I in Torvosaurus in centra, a slender scapular blade, a well-developed ventral their phylogenetic analyses to diagnose Spinosauroidea process of the coracoid, a deep extensor groove and a large, (Sereno et al. 1998; Rauhut 2003; Benson 2010). Among enclosed ischial foramen (Camp 1936; Carrano et al. 2005). large theropod dinosaurs, an enlarged manual digit I ungual For the time being, and based on the current analysis, all has only been reported in the spinosaurids Baryonyx, Sucho- these features are considered homoplastic and independent- mimus and Chilantaisaurus. Therefore, the manual digit I ly acquired in Segisaurus and more derived tetanurans. ungual from Calico Gulch Quarry may not only be the first The enigmatic and poorly known Chilantaisaurus tashui- record of Spinosauridae from North America but also the kouensis from the Ulansuhai Formation of Inner Mongolia oldest known spinosaurid specimen, which could be con- (Hu 1964; Benson and Xu 2008) has recently been referred gruent with the early Pangaean distribution of spinosaurids to as (Benson 2010) and Neovenatoridae inferred above. (Benson et al. 2010), but was previously recognized as a spinosaurid (Rauhut 2003; Yates 2006). Many derived char- Acknowledgments Field expeditions in the Savannakhet Basin were “ ” acters observed in Chilantaisaurus such as the high ratio of supported by the Fondation de France , the French Ministry of Foreign Affairs, the Laotian National Authority for Science and Tech- humeral to femoral length, the in lateral view straight hu- nology, the Savannakhet Province, and the ‘Formation et Recherche au meral shaft, the enlarged manual ungual, and the presence of Laos’ Association. The Dinosavan Project is also supported by the a robust longitudinal ridge bounding the shallow astragalar National Geographic Society. We thank B. Ledimet, A. Soukrany, M. facet medially support its spinosaurid affinities. We added Veran, N. Ouprasay, and S. Phanvilay for assistance during fieldwork and preparation of the specimen, and M. Fontaine for the live recon- Chilantaisaurus to our data matrix and performed a new struction of Ichthyovenator in Fig. 6. We thank P. Taquet and A cladistic analysis in which Chilantaisaurus, , Thiollier who initiated paleontological researches in Laos; M. Carrano, Naturwissenschaften

L. Ferrer, and P. Sereno for helpful data on Segisaurus and Suchomi- Camp CL (1936) A new type of small bipedal dinosaur from the mus; K. Padian, S. Chapman, and A. Milner for access to specimens in Navajo sandstone of Arizona. Bull Univ California Dept Geol their care. We also thank Roger Benson and two anonymous referees Sci 24:39–53 for their thorough and constructive reviews. Carrano MT, Hutchinson JH, Sampson SD (2005) New information on Segisaurus halli, a small theropod dinosaur from the early Juras- sic of Arizona. J Vertebr Paleontol 25:835–849 References Charig AJ, Milner AC (1986) Baryonyx, a remarquable new theropod dinosaur. 324:359–361 Charig AJ, Milner AC (1997) Baryonyx walkeri, a fish-eating dinosaur Allain R (2002) Discovery of megalosaur (Dinosauria, Theropoda) in from the Wealden of Surrey. Bull Nat Hist Mus 53:11–70 the Middle of Normandy (France) and its implications Currie PJ, Zhao XJ (1994) A new carnosaur (Dinosauria: Theropoda) for the phylogeny of basal Tetanurae. J Vertebr Paleontol 22:548– from the Jurassic of Xinjiang, People’s Republic of China. Can J 563 Earth Sci 30:2037–2081 Allain R, Taquet P, Battail B, Dejax J, Richir P, Veran M, Sayarath P, Dal Sasso C, Maganuco S, Buffetaut E, Mendez MA (2005) New Khenthavong B, Thamvirith P, Hom B (1997) Pistes de dino- information on the skull of the enigmatic theropods Spinosaurus, saures dans les niveaux du Crétacé inférieur de Muong Phalane, with remarks on is size and affinities. J Vertebr Paleontol 25:888– province de Savannakhet (Laos). C R Acad Sci Paris 325:815–821 896 Allain R, Taquet P, Battail B, Dejax J, Richir P, Veran M, Limon- de Broin F (2004) A new Shachemydinae (Chelonii, Cryptodira) from Duparcmeur F, Vacant R, Mateus O, Sayarath P, Khenthavong B, the lower cretaceous of Laos: preliminary data. C R Palevol Phouyavong S (1999) Un nouveau genre de dinosaure sauropode 3:387–396 de la Formation des Grès supérieurs (Aptien-Albien) du Laos. C R Galton PM, Jensen JA (1979) A new large theropod dinosaur from the Acad Sci Paris 329:609–616 UpperJurassic of Colorado. Brigham Young Univ Geol Stud Amiot R, Buffetaut E, Lécuyer C, Wang X, Boudad L, Ding Z, Fourel 26:1–12 F, Hutt S, Martineau F, Medeiros MA, Mo J, Simon L, Suteethorn Gauthier J (1986) Saurischian and the origin of . In: V, Sweetman S, Tong H, Zhang F, Zhou Z (2010) Oxygen isotope Padian K (ed) The and the evolution of flight. Mem evidence for semi-aquatic habits among spinosaurid theropods. California Acad Sci. 8:1–55 Geology 38:139–142 Goloboff P (1999) NONA (No Name) ver. 2. Tucumán, Argentina Bailey JB (1997) Neural spine elongation in dinosaurs: sailbacks or Hasegawa Y, Buffetaut E, Manabe M, Takakuwa Y (2003) A possible buffalo-backs? J Paleontol 71:1124–1146 spinosaurid tooth from the Sebayashi formation (Lower Creta- Benson RBJ (2010) A description of bucklandii (Dino- ceous), Gunma, Japan. Bull Gunma Mus Nat Hist 7:1–5 sauria: Theropoda) from the Bathonian of the United Kingdom Hoffet JH (1937) Note sur la géologie du Bas-Laos. Bull Serv Geol and the relationships of Middle Jurassic theropods. Zool J Linn Indochine 24:1–22 Soc Lond 158:882–935 Hoffet JH (1942) Description de quelques ossements de Titanosauriens Benson RBJ, Xu X (2008) The anatomy and systematic position of the du Senonien du Bas-Laos. C R Séances Cons Rech Sci Indochine theropod dinosaur Chilantaisaurus tashuikouensis Hu, 1964 from 1942:51–57 the early cretaceous of Alanshan, People’s Republic of China. Hoffet JH (1944) Description des ossements les plus caracteristiques Geol Mag 145:778–789 appartenant a des Avipelviens du Senonien du Bas-Laos. Bull Benson RBJ, Carrano MT, Brusatte SL (2010) A new clade of archaic Cons Rech Sci Indochine 1944:179–186 large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that Holtz TR, Chapman RE, Lamanna MC (2004a) Mesozoic biogeogra- survived to the latest Mesozoic. Naturwissenschaften 97:71–78 phy of Dinosauria. In: Weishampel DB, Dodson P, Osmólska H Britt BB (1991) Theropods of Dry Mesa Quarry (Morrison Formation, (eds) The Dinosauria, 2nd edn. University of California Press, Late Jurassic), Colorado, with emphasis on the osteology of Berkeley, pp 627–642 Torvosaurus tanneri. Brigham Young Univ Geol Stud 37:1–72 Holtz TR, Molnar RE, Currie PJ (2004b) Basal Tetanurae. In: Brusatte SL, Sereno PC (2008) Phylogeny of Allosauroidea (Dinosau- Weishampel DB, Dodson P, Osmólska H (eds) The Dinosauria, ria: Theropoda): comparative analysis and resolution. J Syst 2nd edn. University of California Press, Berkeley, pp 71–110 Palaeontol 6:155–182 Hone DWE, Xu X, Wang DA (2010) A probable baryonychine tooth Brusatte SL, Benson RBJ, Xu X (2010) The evolution of large-bodied from the late cretaceous of Henan Province, China. Vertebrata theropod dinosaurs during the Mesozoic in Asia. J Iberian Geol PalAsiatica 48:19–26 36:275–296 Hu SY (1964) Carnosaurian remains from Alashan, inner Mongolia. Buffetaut E (1991) On the age of the Cretaceous dinosaur-bearing beds Vertebrata Palasiatica 8:42–63 of southern Laos. Newsl Stratigr 24:59–73 Hutchinson JH (2001) The evolution of pelvic osteology and soft Buffetaut E, Ingavat R (1986) Unusual theropod dinsoaur teeth from tissues on the line to extant birds (Neornithes). Zool J Linn Soc the upper Jurassic of Phu Wiang, northeastern Thailand. Rev Lond 131:123–168 Paleobiol 5:217–220 Huttenlocker AK, Rega E, Sumida SS (2010) Comparative anatomy Buffetaut E, Suteethorn V, Tong H (1996) The earliest known tyran- and osteohistology of hyperelongate neural spines in the sphena- nosaur from the Lower Cretaceous of Thailand. Nature 381:689– codontids Sphenacodon and Dimetrodon (Amniota: Synapsida). J 691 Morphol 271:1407–1421 Buffetaut E, Martill DM, Escuillié F (2004) Pterosaurs as part of a Ingavat R, Janvier P, Taquet P (1978) Découverte en Thaïlande d'une spinosaur diet. Nature 430:33 portion de fémur de dinosaure sauropode (, Reptilia). Buffetaut E, Suteethorn V, Tong H, Amiot R (2008) An early creta- CR Soc Geol France 3:140–141 ceous spinosaurid theropod from southern China. Geol Mag Marsh OC (1881) Principal characters of American Jurassic dinosaurs. 145:745–748 Part V. Am J Sc 21:417–423 Buffetaut E, Cuny G, Le Loeuff J, Sutheethorn V (2009) Late Palae- Milner A, Buffetaut E, Suteethorn V (2007) A tall–spined spinosaurid ozoic and Mesozoic continental ecosystems of SE Asia: an intro- theropod from Thailand and the of spinosaurs. J duction. Geol Soc London, Spec Pub 315:1–5 Vert Paleontol 27:118A Naturwissenschaften

Naish D (2011) Theropod dinosaurs. In: Batten DJ (ed) English weal- Stromer E (1915) Ergebnisse der Forschungsreisen Prof E. Stromer in den fossils. The Palaeontological Association, London, pp 526– den Wüsten Ägyptens. II Wirbeltier-Reste der Baharïje-Stufe 559 (unterstes Cenoman) 3: Das Original des theropoden Spinosaurus Nixon KC (1999–2002) WinClada 1.00.08. Ithaca, N.Y., Nixon KC aegyptiacus nov gen nov spec. Abhandl K Bayer Akad Wiss O’Connor PM (2007) The postcranial axial skeleton of Math-phys Kl 28:1–32 crenatissimus (Theropoda: ) from the late creta- Stromer E (1934) Ergebnisse der Forschungsreisen Prof Stromers in ceous of Madagascar. Mem Soc Vert Paleontol 8:127–162 den Wüsten Ägyptens II Wirbeltier-Reste der Baharije-Stufe Ortega F, Escaso F, Sanz JL (2010) A bizarre, humped Carcharodon- (unterstes Cenoman) 13: Dinosauria. Abhandl Bayer Akad Wiss tosauria (Theropoda) from the Lower Cretaceous of Spain. Nature Math Naturwiss Abt 22:1–79 467:203–206 Sues HD, Frey E, Martill DM, Scott DM (2002) Irritator challengeri,a Owen R (1842) Report on British reptiles. Part II. Rep Br Assoc spinosaurid (Dinosauria: Theropoda) from the lower cretaceous of Adv Sci 1841:60–204 . J Vertebr Paleontol 22:535–547 Owen R (1855) Monograph of the fossil Reptilia of the Wealden and Taquet P (1984) Une curieuse spécialisation du crâne de certains Purbeck formations. Part II. Dinosauria. Palaeontogr Soc Monogr dinosaures du Crétacé: le museau long et étroit des 8:1–54 spinosauridés. C R Acad Sci Paris II 299:217–222 Racey A, Goodall JGS (2009) Palynology and stratigraphy of the Taquet P (1994) Chercheur d’os au Laos. In : Commune d’Oberhaus- Mesozoic red bed sequences from Thailand. Geol bergen (ed.), Josué H. Hoffet, d’Oberhausbergen au Laos, pp 49- Soc Lond Spec Pub 315:69–83 62 Rauhut OWM (2003) The interrelationships and evolution of basal Taquet P, Russell DA (1998) New data on spinosaurid dinosaurs from theropod dinosaurs. Spec Pap Paleontol 69:1–215 the early cretaceous of the Sahara. C R Acad Sci Paris 327:347– Rayfield EJ, Milner AC, Xuan VB, Young PG (2007) Functional 353 morphology of spinosaur ‘crocodile-mimic’ dinosaurs. J Vertebr Taquet P, Battail B, Dejax J, Richir P, Veran M (1995) First discovery Paleontol 27:892–901 of dinosaur footprints and new discoveries of dinosaur bones in Russell DA (1994) The role of Central Asia in dinosaurian biogeogra- the lower cretaceous of the Savannakhet Province, Laos. In: IGCP phy. Canadian Journal of Earth Sciences 30:2002–2012 Symposium on Geology of SE Asia, Hanoi. J Geol 5–6:167 Sereno PC, Beck AL, Dutheil DB, Gado B, Larsson HCE, Lyon GH, Tykoski RS, Rowe T (2004) Ceratosauria. In: Weishampel DB, Dod- Marcot JD, Rauhut OWM, Sadleir RW, Sidor CA, Varricchio D, son P, Osmólska H (eds) The Dinosauria, 2nd edn. University of Wilson GP, Wilson JA (1998) A long-snouted predatory dinosaur California Press, Berkeley, pp 47–70 from Africa and the evolution of spinosaurids. Science 282: Xu X, Clark JM, Forster CA, Norell MA, Erickson GM, Eberth DA, 1298–1302 Jia C, Zhao Q (2006) A basal tyrannosauroid dinosaur from the Sha J (2007) Cretaceous trigonioidid (non-marine Bivalvia) assemb- late Jurassic of China. Nature 439:715–718 lages and biostratigraphy in Asia with special remarks on the Xu X, Clark JM, Mo J, Choiniere J, Forster CA, Erickson GM, Hone classification of Trigonioidacea. J Asian Earth Sci 29:62–83 DWE, Sullivan C, Eberth D, Nesbitt SJ, Zhao Q, Hernandez R, Jia Smith AG, Smith DG, Funnell BM (1994) Atlas of Mesozoic and CK, Han FL, Guo Y (2009) A Jurassic ceratosaur from China Cenozoic. Cambridge University Press, Cambridge helps clarify avian digital homologies. Nature 459:940–944 Smith JB, Lamanna MC, Mayr H, Lacovara KJ (2006) New informa- Yates AM (2006) A new theropod dinosaur from the early jurassic of tion regarding the holotype of Spinosaurus aegyptiacus Stromer, South Africa and its implications for the early evolution of thero- 1915. J Paleontol 80:400–406 pods. Palaeontol Afr 41:105–122 Smith ND, Makovicky PJ, Hammer WR, Currie PJ (2007) Osteology Zhao XJ, Currie PJ (1993) A large crested theropod from the Jurassic of ellioti (Dinosauria: Theropoda) from the of Xinjiang, People’s Republic of China. Can J Earth Sci 30: Early Jurassic of Antarctica and implications for early theropod 2027–2036 evolution. Zool J Linn Soc Lond 151:377–421 Zhao XJ, Benson RBJ, Brusatte SL, Currie PJ (2010) The postcranial Stovall JW, Langston W (1950) atokensis, a new skeleton of Monolophosaurus jiangi (Dinosauria: Theropoda) and species of lower cretaceous Theropoda from Oklahoma. from the Middle Jurassic of Xinjiang, China, and a review of Am Midl Naturalist 43:696–728 Middle Jurassic Chinese theropods. Geol Mag 147:13–27 本文献由“学霸图书馆-文献云下载”收集自网络，仅供学习交流使用。

学霸图书馆（www.xuebalib.com）是一个“整合众多图书馆数据库资源，

提供一站式文献检索和下载服务”的24 小时在线不限IP 图书馆。 图书馆致力于便利、促进学习与科研，提供最强文献下载服务。

图书馆导航：

图书馆首页 文献云下载 图书馆入口 外文数据库大全 疑难文献辅助工具