Tharosaurus indicus, Bajpai & Datta & Pandey & Ghosh & Kumar & Bhattacharya, 2023

Bajpai, Sunil, Datta, Debajit, Pandey, Pragya, Ghosh, Triparna, Kumar, Krishna & Bhattacharya, Debasish, 2023, Fossils of the oldest diplodocoid dinosaur suggest India was a major centre for neosauropod radiation, Scientific Reports 13 (1), No. 12680, pp. 1-15 : 1-8

Tharosaurus indicus gen. et sp. nov.

Etymology. Generic name is a combination of Tharo, referring to the ‘Thar desert’ of western India where the type specimen was found, and saurus, which is derived from the Greek word ‘sauros’ meaning lizard; specific name is for the country of origin i.e., India.

Holotype. RWR-241(A–K) ; partial middle/posterior cervical vertebra; middle/posterior cervical anterior condyle and right prezygapophyses; partial anterior dorsal neural arch; middle/posterior neural spines; anterior dorsal rib; partial anterior and middle caudal vertebrae ( Figs. 2 , 3 , 4 , 5 ; Supplementary Table 1).

Horizon and locality. Fort Member of the Jaisalmer Formation (early–middle Bathonian), Jethwai village, District Jaisalmer, Rajasthan state, western India.

Diagnosis. Tharosaurus exhibits a unique combination of the following characters: middle/posterior cervical centroprezygapophyseal lamina divided into lateral and medial branches, the latter connecting with the intraprezygapophyseal lamina (shared with all dicraeosaurids); middle/posterior cervical centropostzygapophyseal fossa elliptical and bordered laterally by pillar-like centropostzygapophyseal lamina (shared with the dicraeosaurids Lingwulong , Brachytrachelopan , and Pilmatueia ); deep bifurcation of cervical neural arch extending up to the dorsal margin of the neural canal (shared with the dicraeosaurids Amargasaurus and Pilmatueia ); paired fossae on the ventral surface of the middle/posterior cervical centrum separated by a mid-line keel (shared with all dicraeosaurids, barring Smitanosaurus , Kaatedocus and Suuwassea , and the diplodocids— Barosaurus and Dinheirosaurus ); paired ventral fossae extending up to the posterior margin of centrum; anterior condyle of middle/posterior cervical more rugose compared to the rest of the centrum (shared with the dicraeosaurid Kaatedocus ); bifid middle/posterior cervical neural spine (shared with Flagellicaudata); divided lateral fossa/ pleuroceol on cervical centra (shared with Flagellicaudata); lateral fossa divided into deep posterior and shallow anterior half by weak ridge on the ventral surface of the fossa; prominent lateroventral flanges on middle/posterior cervical centrum (shared with Flagellicaudata); middle/posterior cervical vertebrae with pre-epipophysis (shared with Flagellicaudata); cordiform cross-section of anterior caudal centra (shared with Flagellicaudata); middle/posterior dorsal transverse process laterally directed (shared with Diplodocidae ); middle caudal centra articular surface with flat ventral margin (shared with Diplodocoidea); ventral surface of mid-caudal centrum with deep median fossa.

Autapomorphies: triangular ventrolateral projections lying below posterior cotyle of middle/posterior cervical centrum visible in posterior view; ventral mid-line keel on middle/posterior cervical centrum bifurcating posteriorly but not meeting the lateroventral flanges; lateral pleuroceol on anterior caudal centra.

Description. The cervical vertebrae are represented by five partial specimens found in association (Supplementary Table 1), including the anterior condyle, posterior half of a vertebra and three right prezygapophyses ( Figs. 2 , 3 ). The anterior condyle is U-shaped with an opisthocoelous condition as in other eusauropods 22, 23 ( Fig. 2A ), and is mediolaterally wider than dorsoventrally tall [RWR-241-A, centrum articular surface height (cH)/centrum articular surface width (cW)= 0.7; Supplementary Table 2, Supplementary Fig. 2 ]. In this respect, Tharosaurus is similar to the middle/posterior cervicals of several flagellicaudatans: Suuwassea 24 (cH/cW = 0.7), Lingwulong 13 (cH/cW =0.7), Pilmatueia 8 (CV7/8, cH/cW = 0.9), Amargasaurus 5 (CV8, cH/cW = 0.8), Apatosaurus louisae 25 (CV9, cH/cW = 0.7) and Diplodocus carnegii 26 (CV11, cH/cW = 0.9). The anterior condyle is markedly more rugose than the other vertebral elements, as in Kaatedocus 27 (CV14).

The centrum shows strong anterior constriction with the lateral surfaces excavated by large fossae, similar to many flagellicaudatans 8, 13, 24, 26 ( Fig. 2B–E ). The fossa is partially preserved with much of the dorsal rim and medial wall broken off. The preserved portion suggests the fossa was elliptical, being elongated and dorsoventrally compressed ( Fig. 2B–C ). The dorsal margin of the fossa is rod-like and extends laterally beyond the ventral margin. The latter is robust, rounded and thickest near the posterior end of the centrum, accentuating the depth of the fossa. Anteriorly it becomes flush with the lateral surface of the centrum ( Fig. 2B–C ). Beneath the ventral margin of the fossa, the lateral surface of the centrum is markedly concave and flares posteriorly. The fossa is restricted to the posterior half of the centrum and includes two distinct halves: a short and shallow anterior half and a longer and deeper posterior half. The two halves are demarcated by a low U-shaped ridge on the ventral surface of the fossa, medial to the ventral margin and extending slightly onto the medial wall of the fossa. This contrasts with the dicraeosaurids Amargasaurus , Dicraeosaurus , Bajadasaurus , and Pilmatueia where the fossa is undivided and shallow 5, 7, 8. In the middle cervicals of Lingwulong and Suuwassea , however, the lateral fossa is deep and extends nearly along the entire length of the centrum 13, 24. Furthermore, the lateral fossa in Tharosaurus is succeeded by a posteroventral fossa ( Fig. 2D,E ), as seen in the mid-cervicals of Amargasaurus , Apatosaurus , Bajadasaurus , and Pilmatueia 26, 28.

The ventral surface of the centrum ( Fig. 2F–G ) accommodates paired longitudinal depressions/fossae. Such depressions are common in diplodocids and most dicraeosaurids, barring Bajadasaurus which only bears a longitudinalkeel 7, 8, 13, 26. The fossae are asymmetrical, with the right fossa mediolaterally wider, and extend up to the posterior margin of the centrum where they flare out. However, in Dicraeosaurus , Lingwulong , and Pilmatueia the fossae are symmetrical and strongly expressed anteriorly, but do not reach the posterior margin of the centrum 8, 13, 26. The fossae in Tharosaurus are flanked laterally by prominent lateroventral flanges and separated by a sharp midline keel ( Fig. 2F,G ). The keel shows lef lateral convexity and remains prominent throughout its preserved length. It extends nearly up to the posterior margin of the fossae and bifurcates into two short ridges. The latter, however, do not reach up to the lateroventral flanges. An accessory ridge, present only on the right ventral surface, extends posterolaterally from the midline keel. The presence of a ventral keel is shared with a diverse array of flagellicaudatans including most dicraeosaurids ( Lingwulong , Dicraeosaurus , Pilmatueia , Bajadasaurus and Brachytrachelopan ) 7 – 9, 13 and some later-diverging diplodocids ( Barosaurus lentus , Diplodocus carnegii , Dinheirosaurus ) 23, 26. It is, however, absent in some putative plesiomorphic dicraeosaurids ( Suuwassea and Smitanosaurus ) 24, 29, barring Kaatedocus 27 which is the earliest-diverging dicraeosaurid. The disposition and morphology of this midline keel differentiate Tharosaurus from Lingwulong , Dicraeosaurus , Brachytrachelopan and Barosaurus where the keel is prominent anteriorly 4, 8, 9, 26. In Dinheirosaurus the keel is restricted to the posterior part of the centrum and does not extend anteriorly as in Tharosaurus, whereas in Pilmatueia the keel forks anteriorly and posteriorly with the bifurcation point placed slightly anterior to the mid-length of the centrum.

The posterior cotyle of the centrum (RWR-241-B, cH/cW = 0.6, Fig. 2H,I , Supplementary Table 2) is strongly concave and mediolaterally wider than dorsoventrally tall, a feature seen in the middle cervicals of many sauropods including Lingwulong 13 (cH/cW =0.7), Apatosaurus louisae 25 (cH/cW= 0.7) and Gleamopus 30 (cH/cW= 0.9), and the posterior cervicals of Pilmatueia 8 (cH/cW = 0.6) and Suuwassea 24 (cH/cW = 0.7). The posterior cotyle is cordiform in outline with a weakly concave dorsal margin immediately ventral to the neural canal as in Lingwulong and Pilmatueia 8, 13. Tharosaurus, however, can be distinguished by the presence of posteriorly facing triangular facets along the ventrolateral margin of the posterior articular surface.

The neural arch is partially preserved and includes the right prezygapophysis and the region surrounding the neural canal ( Figs. 2B–K , 3 , Supplementary Table 1). The anterior exit of the canal, although partial, appears oval, but the posterior exit is complete and elliptical, being transversely wider than dorsoventrally high. In Pilmatueia this exit is triangular, whereas in Suuwassea and Lingwulong it is circular–subcircular 8, 13, 24.

The prezygapophysis is anterodorsally directed with the articular facet strongly convex transversely and longitudinally ( Fig. 3A–G ). The latter feature is shared with middle and posterior cervicals of the flagellicaudatans Diplodocus carnegii (CV8) and Kaatedocus (CV10) 26 – 29. The prezygapophyseal articular surface is oblong with the posterior border offset from the surrounding dorsal surface of the prezygapophysis by a transverse sulcus ( Fig. 3C,D,G ), similar to the posterior cervicals of Kaatedocus 27. Immediately ventral to the articular surface, the lateral surface of the prezygapophysis bears an anterodorsally-posteroventrally oriented pre-epipophysis (sensu Tschopp et al. 26; Fig. 3A,B ). The latter is dorsoventrally compressed and succeeded ventrally by a shallow fossa. Such a ridge is also reported in the middle and posterior cervicals of Kaatedocus 27 (CV7–10), Apatosaurus louisae 26 (CV11) and Suuwassea 24, 26. The prezygapophysis is supported ventrally by a dorsoventrally high and robust centroprezygapophyseal lamina (cprl, Fig. 3C–F ). The lamina is divided into a larger and medially concave lateral branch connecting with the prezygapophysis (lcprl) and a smaller medial branch joining the intraprezygapophyseal lamina (mcprl). The two halves of the cprl accommodate a triangular and deep centroprezygapophyseal fossa ( Fig. 3C,D ) which borders the neural canal dorsolaterally and is roofed by a sheet-like intraprezygapophyseal lamina. While a divided cprl is common in Flagellicaudata 1, in dicraeosaurids the medial branch of the cprl connects with the intraprezygapophyseal lamina and is listed as a synapomorphy of Dicraeosauridae (sensu Whitlock and Wilson Mantilla 29). Unlike in Tharosaurus, however, both branches of the cprl join the prezygapophysis in diplodocids 1, 26, 29, 31. Nonetheless, the anterior surface of the lcprl immediately ventral to the prezygapophyseal articular surface bears a depression giving the impression of a split cprl, where both branches connect to the prezygapophysis, akin to diplodocids. Further scrutiny shows this depression to be almost indistinct and unlike the morphology of the bifurcated crpl of diplodocids 26, 32. Furthermore, in diplodocids the apex of this bifurcation is ventrally directed in contrast to the incipient depression in Tharosaurus which is broad and dorsally convex. Therefore, the expression of the divided cprl in the new Indian taxon is closer to that of dicraeosaurids and supports its taxonomic allocation.

The posterior exit of the neural canal is flanked dorsolaterally by two elliptical centropostzygapophyseal fossae [cpof(e)] which are bordered laterally by robust pillar-like centropostzygapophyseal laminae [cpol(e), Fig. 2H,I ]. The cpof(e) are roofed by thin intrapostzygapophyseal laminae. The arrangement of the vertebral laminae and fossae in Tharosaurus is comparable with the condition in Lingwulong , Brachytrachelopan , Dicraeosaurus , Amargasaurus and Pilmatueia 4, 5, 8, 9, 13. However, in the latter two taxa, the cpof(e) are triangular. Furthermore, as in Amargasaurus 5, 8, the neural arch in Tharosaurus is devoid of a median tubercle.

The preserved neural arch above the neural canal shows deep bifurcation which descends to the roof of the canal and encloses an anteroposteriorly extensive passage of uniform width ( Fig. 2H–K ; Supplementary Fig. 3 ). The broken ends of the neural arch dorsal to the cpof(e) suggest the presence of strongly divergent postzygapophyses. These features are reminiscent of the deeply bifurcated neural arch-spine complex of middle to cervicodorsal vertebrae of Amargasaurus and Pilmatueia 5, 8, 28. Moreover, the surface of the neural arch within this passage is finished (as seen in dorsal view, Fig. 2J,K ), and bears rugose scars along the mid-line which possibly represent ligament scars. The scars largely occupy the posterior half of the passage and bordered laterally by sub-parallel striations. Rugose tuberosity on the floor of bifurcated neural arch-spine complexes of Apatosaurus ajax and Dicraeosaurus have been interpreted as ligament scars 33. Although Tharosaurus lacks the tuberosity, a feature shared with Amargasaurus 8, these scars attest to the presence of bifid neural spines in Tharosaurus. Similar bifid neural spines are listed as a synapomorphy of Flagellicaudata in previous studies (e.g., Wilson 1).

The specimens (RWR-241-A–E) likely represent the 6th/8th cervical based on comparisons with the middle cervicals of Lingwulong and Bajadasaurus , and the middle–posterior cervicals of Dicraeosaurus , Suuwassea , Amargasaurus , Pilmatueia and Kaatedocus 5, 8, 13, 24, 27.

Three isolated specimens including a partial neural arch and two partial neural arch-spine complexes are referable to the dorsal vertebral series ( Fig. 4A–L , Supplementary Table 1). The neural arch comprises a stout, sub-horizontal transverse process with an anteroposteriorly broad and sigmoidal diapophysis ( Fig. 4A–F ). Anteriorly, the transverse process bears a broad and moderately deep prezygapophyseal centrodiapophyseal fossa ( Fig. 4A,B ), whereas its posterior surface bears a thin, mediodorsally-lateroventrally directed lamina, possibly representing the postzygodiapophyseal lamina ( Fig. 4C,D ). A deep centrodiapophyseal fossa (cdf) positioned ventral to the transverse process is bordered by an anteroventrally directed anterior centrodiapophyseal lamina and a near-vertical posterior centrodiapophyseal lamina ( Fig. 4E,F ). The specimen is tentatively assigned to the anterior dorsals based on similarity in overall morphology including laminae and fossae configuration with those of the flagellicaudatans Apatosaurus louisae , Dinheirosaurus , Lingwulong and Amargasaurus cazaui 5, 13, 23, 25, 26.

The neural arch-spine complex is strongly compressed anteroposteriorly and expanded transversely, suggesting a more posterior position in the dorsal vertebral series (sensu McPhee et al. 34). The arch comprises a transversely broad and subtriangular spinoprezygapophyseal fossa ( Fig. 4G,H ). The transverse process is laterally directed, with a vertically oriented distal end, similar to all diplodocids 23, 35. This laterally oriented transverse process can be considered a local autapomorphy of Tharosaurus unlike a dorsolaterally oriented transverse process in other dicraeosaurids 5, 9, 13, 36. This feature may alternatively represent a symplesiomorphy, although Mannion et al. 23 listed the dorsolaterally projecting diapophysis in the dorsal vertebrae of the diplodocid Dinheirosaurus as a local autapomorphy. The neural spine is transversely expanded and non-bifid and the disposition of the lateral spinal margins suggests dorsal flaring in anterior/posterior views ( Fig. 4G–J ). This suggests affinity with the middle/posterior dorsal vertebrae because non-bifurcated neural spines appear from the 6th/7th dorsal of dicraeosaurids, as seen in Lingwulong and Brachytrachelopan 9, 13. Such flaring of the lateral spinal margins is also known from the middle and posterior dorsals of dicraeosaurids 4, 13, 35. In lateral view, the anterior and posterior borders of the neural spine remain subparallel ( Fig. 4K,L ), unlike the sub-triangular spinal lateral profile characteristic of many titanosauriforms 34, 37. The neural spine bears a sharp prespinal lamina placed along the longitudinal midline on the anterior surface ( Fig. 4G,H ). The prespinal lamina does not extend up to the base of the spine and terminates dorsal to the spinoprezygapophyseal fossa. This lamina, however, extends down to the base of the neural spine in the posterior dorsals of Amargasaurus and Dicraeosaurus 5, 36. Only a small part of the spinoprezygapophyseal lamina is preserved along the lateral margin of the anterior spinal surface ( Fig. 4G,H ). The spinodiapophyseal lamina is robust and broad, descending gently from the neural spine to the transverse process ( Fig. 4G,H,K,L ). The posterior surface of the spine preserves only the right spinopostzygapophyseal lamina ( Fig. 4I,J ). It is robust and well-rounded, extending medially from the lateral margin of the posterior spinal surface towards the midline. In lateral view, the anterior surface of the spinopostzygapophyseal lamina unites with the posterior surface of the spinodiapophyseal lamina as seen in the posterior dorsals of Brachytrachelopan 9 ( Fig. 4K,L ), and these laminae enclose the postzygapophyseal spinodiapophyseal fossa. Thus, these vertebral specimens likely belong to the middle/posterior dorsals.

An isolated, nearly complete rib ( Fig. 4M,N ) is identified as the right anterior dorsal rib, based on similarity with that of Galeamopus pabsti 30. The specimen is Y-shaped, flares out proximally, and becomes dorsoventrally skewed distally. The rib lacks pneumatic openings as in diplodocoids but contrasts with those of titanosauriforms 38. The capitulum is elliptical, anteroposteriorly compressed, and directed anterodorsally. It is longer than the tuberculum and bears prominent striations on the anterior surface ( Fig. 4M ). The tuberculum is short and curved towards the capitulum. The tuberculum and capitulum enclose a broad U-shaped space. A robust and rounded ridge occupies the anterior surface of the rib distal to the capitulum and tuberculum ( Fig. 4M ). The ridge extends distally and gradually becomes flush with the surface. The ventral margin is sigmoidal with the portion immediately distal to the tuberculum strongly convex. The dorsal margin is concave, and its posterior surface is largely flat and featureless, except for the strongly rugose tuberculum.

The collection includes two caudal vertebrae (Supplementary Table 1). One of these, a partial centrum of an anterior caudal vertebra, preserves the anterior cotyle and the proximal-most part of the neural arch ( Fig. 5A–C ). The centrum is robust with a moderately concave anterior cotyle. The latter is dorsoventrally taller than mediolaterally wide (RWR-241-J, cH/cW =1.2, Supplementary Table 2) and comparable in proportion to the anterior caudals of other flagellicaudatans such as Dicraeosaurus 39, 40 (cH/cW = c. 1), Suuwassea 24 (ANS 21122, cH/cW = 1.1), Lingwulong 13 (cH/cW = 1.1) and Amazonsaurus 41 (cH/cW = 1.1). It is, however, dorsoventrally taller compared to Diplodocus 40 (cH/cW = 0.9), Amargatitanis 11 (MACN PV N53, cH/cW = 0.7) and Brontosaurus excelsus 26, 42 (YPM 1980, cH/cW = 0.9). The ventral margin of the anterior cotyle, although partial, preserves a small chevron facet ( Fig. 5A ). The preserved lateral surface of the centrum is convex and bears a lateral foramen immediately ventral to the neural arch, a feature present in anterior caudals of most diplodocids 23, 40, 43 ( Fig. 5B ). The lateral surface, however, does not bear any ridges, similar to Amargatitanis 11. In lateral view, the ventral margin of the centrum is strongly concave, akin to Lingwulong 13. Moreover, the curvature of the ventral margin suggests the ventral rim of the posterior central articular surface to be at a lower level than the anterior, a feature shared with Dicraeosaurus 39 and Suuwassea 24. The neural arch is poorly preserved ( Fig. 5A,B ) and placed anteriorly on the centrum as in Dicraeosaurus 39, Lingwulong 13 and Suuwassea 24. The ventral surface is weakly convex transversely with an incipient midline keel ( Fig. 5C ). This ventral keel is also present in other dicraeosaurids, including Suuwassea and Dicraeosaurus 8, 24, 39.

The second caudal (RWR-241-K) vertebra is a nearly complete centrum but without the neural arch ( Fig. 5D–G ). The centrum is anteroposteriorly elongated, suggesting a more posterior position in the caudal series compared to RWR-241-I (sensu Coria et al. 8). The centrum is 1.6 times as long as high, with a deep fossa extending along the entire length of the centrum, identifying it to be a middle caudal (sensu McPhee et al. 34). This is corroborated by similarities with middle caudal centra of Suuwassea 24 (cL/cH = 1.5) and Amargatitanis 11 (cL/cH = 1.3). A prominent lateral fossa is also reported in the dicraeosaurid Amargatitanis 11. Furthermore, judging from the broken dorsal surface of the centrum, the neural arch was possibly more anteriorly placed in RWR-241-J as in the afore-mentioned dicraeosaurids. The centrum is platyceolous with the anterior and posterior cotyles dorsoventrally taller than mediolaterally wide ( Fig. 5D,E ), although there is some evidence of deformation. The ventral surface is strongly concave in lateral view with the ventral margin of the posterior cotyle descending below the level of the anterior cotyle. The fossa on the ventral surface is deep, constricted at midlength and bordered by robust ventrolateral ridges ( Fig. 5G ), similar to the derived diplodocids such as Diplodocus 44, Seismosaurus 45, and Barosaurus 46.

Phylogenetic analysis. The inter-relationship of Tharosaurus within Sauropodomorpha was tested in a reduced version of the data matrix used by Gallina et al. 7 (see “Methods” and Supplementary Note 2). The analysis recovered 20 most parsimonious trees with a tree length of 760, consistency index (CI) of 0.483 and retention index (RI) of 0.647. The topology of the strict consensus tree (Supplementary Fig. 4 ) shows a well resolved clade Sauropoda with diplodocoids and macronarians showing distinct clustering within Neosauropoda, consistent with previous studies 7, 13. Tharosaurus is recovered as a dicraeosaurid flagellicaudatan, although the clade Dicraeosauridae is poorly resolved. In the 50% majority rule tree ( Fig. 6 ), Dicraeosauridae is better resolved with Tharosaurus being a sister taxon to (( Pilmatueia + Amargatitanis ) + ( Brachytrachelopan + ( Dicraeosaurus + Amargasaurus ))).

Figures

Figure 2. Cervical vertebrae (CV6/8) of hvarosaurus indicus. (a) RWR-241-A, anterior cotyle in anterior view. (b–k) RWR-241-B, partial vertebra, photographs and line drawings in (b,c) right lateral view, red line indicates U-shaped ridge demarcating anterior and posterior halves of lateral pneumatic fossa; (d,e) lef lateral view; (f,g) ventral view, red line indicates posteriorly bifurcated midline keel and arrow indicates accessory ridge; (h,i) posterior view, arrows and red arrowheads indicate deep bifurcation of neural arch and triangular facets below cotyle, respectively. (j,k) dorsal view, arrowhead indicates passage enclosed by bifid neural arch and ligament scars and striations marked in red and purple, respectively. Broken areas and artefacts in grey and pink, respectively. c centrum, cpof centropostzygapophyseal fossa, cpol centropostzygapophyseal lamina, lf lateral fossa, lvf lateroventral flange, mk midline keel, na neural arch, nc neural canal, pvf posteroventral fossa, tpol intrapostzygapophyseal lamina. Scale bars represent 50 mm.

Figure 3. Right cervical prezygapophysis (CV6/8) of hvarosaurus indicus. RWR-241-C, photographs and line drawings in (a,b) lateral view; (c,d); medial view; (e,f) anterior view; (g) dorsal view. Arrowheads indicate transverse sulcus beneath dorsal articular surface of prezygapophysis. cprf centroprezygapophyseal fossa, epi pre-epipophysis, lcprl lateral branch of centroprezygapophyseal lamina, mcprl medial branch of centroprezygapophyseal lamina, nc neural canal, tprl intraprezygapophyseal lamina. Scale bars represent 50 mm.

Figure 4. Dorsal vertebrae of hvarosaurus indicus. RWR-241-F, partial anterior dorsal neural arch, photographs and line drawings in (a,b) anterior view; (c,d) posterior view; (e,f) anterior view. RWR-241-G, partial middle/ posterior dorsal neural arch-spine complex, photographs and line drawings in (g,h) anterior view; (i,j) posterior view; (k,l) lateral view. RWR-241-I, nearly complete anterior dorsal rib in (m) anterior view; (n) posterior view. acdl anterior centrodiapophyseal lamina, ca capitulum, cdf centrodiapophyseal fossa, da diapophysis, ns neural spine, pcdl posterior centrodiapophyseal lamina, podl postzygodiapophyseal lamina, posdf postzygapophyseal spinodiapophyseal fossa, prcdf prezygapophyseal centrodiapophyseal fossa, prsl prespinal lamina, spdl spinodiapophyseal lamina, spol spinopostzygapophyseal lamina, sprl spinoprezygapophyseal lamina, sprf spinoprezygaposphyseal fossa, tp transverse process, tu tuberculum. Scale bars represent 50 mm.

Figure 5. Caudal vertebrae of hvarosaurus indicus. RWR-241-J, partial anterior caudal vertebra in (a) anterior view; (b) right lateral view; (c) ventral view. RWR-241-K, middle caudal centrum in (d) anterior view; (e) posterior view; (f) lef lateral view; (g) ventral view. c centrum, chf chevron facet, lf lateral fossa, lpfo lateral pneumatic foramen, vf ventral fossa, vr ventrolateral ridge.

Figure 6. Phylogenetic position of hvarosaurus indicus gen. et sp. nov. (RWR-241) in 50% majority-rule tree. Clade Dicraeosauridae shaded in pink. Numbers above nodes indicate Bremer support values.