Mesozoic vertebrates are known from India more than one and half century ago [1]. But from Pakistan the first bone of titanosaurian sauropod dinosaur [2] recently was discovered in 2000. So far 3000 fossil bones and pieces were discovered from Pakistan. All the fossil bones of titanosaurs were reported from the latest Cretaceous (67 - 66 Ma) Vitakri Formation from Pakistan [3] [4] and its coeval Lameta sediments from India. The skull of Marisaurus jeffi titanosaur [5], different types of osteoderms of titanosaurs were reported first time in Asia [6] and titanosauriforms or basal titanosaur [7] were reported from Pakistan. Five taxa of titanosaurs from Pakistan namely Pakisaurus balochistani, Sulaimanisaurus gingerichi and Khetranisaurus barkhani of pakisaurids, Marisaurus jeffi and Balochisaurus malkani of balochisaurids were established on diverse caudal vertebrae [8]. This extended abstract [8] was submitted earlier than papers [5] [6] [7] but due to conference date changing from 2003 to 2004, the papers [5] [6] [7] were published earlier than conference [8] paper. These taxa of titanosaurs were described and figured in 2006 [9]. Diverse presacral vertebrae of titanosaurs were also reported from Pakistan [10]. Later on many postcranial fossils were referred to Marisaurus jeffi [11] [12] [13], Balochisaurus malkani [13] [14] and Pakisaurus balochistani [15]. These titanosaurs were considered invalid [16] except Isisaurus and Jainosaurus. The fossils from Pakistan were diagnostic and consequently Gspsaurus pakistani [17] and Saraikimasoom vitakri [17] were established on diagnostic skull and snout which were previously referred to Marisaurus jeffi [9] and Balochisaurus malkani [9] respectively. Further Nicksaurus razashahi [17] [18] and Maojandino alami [18] [19] were established on holotypic cranial, vertebral and appendicular elements which were previously referred to Marisaurus jeffi [9] and Balochisaurus malkani [9] respectively. Recently four titanosaurs from Indo-Pakistan like Gspsaurus pakistani [20] [21], Saraikimasoom vitakri [22] [23], Pakisaurus balochistani [24] and here, and Isisaurus colberti [25] (and here) were diagnosed out of total 15 named taxa from Indo-Pakistan subcontinent.

There were suggestions from Prof. Ashok Sahni and Dr. Okmar Verma from India and Dr. Nick Longrich from UK to carry out dry and wet sieving of sediments at 7, 18, 25 mesh to carry out microvertebrates study for comparisons with Indian microvertebrates but it is not possible due to security problem. The author collected about 2 kilograms of stream sediments (about coarse sandy size) from Bara Khadro section of Lakhi Range, Sind and after study of a few 100 gram, one silicified tooth was found [26]. It tells incouraging results to continue further microvertebrates study especially in Vitakri dome and surrounding area of Sulaiman foldbelt (Balochistan Province of Pakistan) and Bara-Khadro and other anticlinal core areas of Lakhi thrusted anticline of eastern Kirthar foldbelt (Sindh Province of Pakistan).

So far Mesozoic vertebrates are found from about 30 localities. Some localities have many sites. Some major localities belong to Vitakri dome, Dhaola-Andhari, Andhari-Chapar (Sadiqani-Chapar), Mari Bohri and Rakhni (Mat Khetran-Kachar) areas of Barkhan District of Balochistan, Beaker area of Dera Bugti District of Balochistan, and Fort Munro-Rakhi Gaj areas of Dera Ghazi Khan District of South Punjab [14]. Vitakri dome includes the Sangiali 1, Bor 2, Shalghara 3, Kinwa 4, mid Kinwa 4m, north Kinwa 4n, Top Kinwa 16, Alam 19 (19c), north Alam 19n, south Alam 19s, Eastern Alam 18, Dada Pahi 17 and Roosmani 20. The Dhaola-Gambrak area included Dagar 5, Goes Wanga Pass 6, Zubra peak 7, South Zubra or Basti Nala 7, Darwaza 8, Grut 9, Rahi Wali 10, northeast 11, eastnortheast Dolwahi 12 and Dolwahi east 13. Andhari-Chapar range produced only one locality namely Sadiqani Chapar locality 14 which was visited; the remaining areas of this range is not visited so far. Mari Bohri area produced also only one Mari Bohri 15 locality with 4 or 5 sites. Fort Munro area has produced Top Girdu 24 and Mian Ghundi 25 (Khar Fort Munro). Rakhni area produced Mat Khetran 21 and Kachar 23. Beakar (Baekar/Beaker) area of Dera Bugti District produced one locality namely Bhal 22 [14]. At the end locality numbers are marked. The other significant areas are Chitri and Dragal Maarri of Rajan Pur district, South Punjab especially for bones, eggs and footprints. Most of these localities belong to Sulaiman (middle Indus) Range and their locations are shown in maps [14]. However some localities from western Kirthar range, Khuzdar district of Balochistan [14] and Khadro-Bara and other anticlinal core areas of Laki thrusted anticline of eastern Kirthar range, Jam Shoro District of Sindh [26]. Footprints and trackways of late Jurassic dinosaurs were also found from Malakhel area of Mianwali district, Kohat-Potwar basin, Punjab [27].

Here two slender titanosaurs from Indo-Pakistan namely Pakisaurus balochistani and Isisaurus colberti are recognized. Previously no any comparisons of slender titanosaurs from Pakistan and India are available, so here the Pakisaurus balochistani the slender titanosaur are being described and compared with other titanosaurs from India and Pakistan. Further the missing gaps especially femur, tibia, fibula and metatarsal of hind limb of Isisaurus colberti are discovered from Pakistan and being added here.

The systematic paleontology of Pakisaurus balochistani is as follows.

Dinosauria [28];

Saurischia [29];

Sauropoda [30];

Titanosauria [31];

Poripuchia [4] [27];

Pakisauridae [9];

Pakisaurus [9];

Pakisaurus balochistani [9];

(Figures 1-5).

The holotypic postcranial materials (Figures 1-3) of Pakisaurus balochistani were found from South Kinwa 4, Pakistan Dinosaur Locality 4/PDL 4. These holotypic materials (Figures 1-3) were considered associated and belong to one animal due to finding from same locality and same formation, fit in size and no

duplication. The holotypic skeletal bones (Figures 1-3) are consistent with other associations of bones of this taxon and other 3 recognized taxa from Pakistan

and India. A postcranial skeleton from lower Bor (Figure 4) is significant exemplar of Pakisaurus balochistani. Some materials referred from northwestern Top Kinwa 16 (Figure 5), Shalghara 3 (Figure 5), North Alam 19n (Figure 5), and east Dolwahi 13 (Figure 5) localities from Pakistan. A braincase (Figure 5) and some other fossils were also referred from India.

The lower Bor skeleton (Figure 4) is represented by a pair of humerus (left and right humerus), a pair of femur (left and right femur), a pair of tibia (left and right tibia), a fibula and possibly a caudal vertebra. Most of these bones are partial and incomplete but represents typical and key features of a taxon Pakisaurus balochistani. The association of bones are evidenced by the field occurrence at one place/site/locality within a diameter of 10 meter on the just close to western side of peak, on the surface of host upper shale unit, fit in size, pair of bones with same size and features, and no duplication of bones representing another animal. Here the bones were found from the upper shale unit of Vitakri

Formation which is capped by the upper sandstone unit of Vitakri Formation. The slender flattened tibia with anteroposteriorly broad distal end, humerus with expanded and anteriorly exposed radial condyle, and tall caudal vertebra of lower Bor locality are the major key elements for attribution to Pakisaurus balochistani. The humerus and caudal vertebra of lower Bor are overlapped with holotype (Figures 1-3) of Pakisaurus balochistani. The lower Bor skeletal key elements did not match to holotypic materials of Isisaurus colberti from Dangargaon, India [25], and referred lower Sangiali and Zubra peak skeletons [23] from Pakistan (Figure 6) of Isisaurus colberti pakisaurid slender Poripuch titanosaur, and Chota Simla skeleton from India [16] [21] [32] and Alam, Top Kinwa and Mari Bohri skeletons from Pakistan of Gspsaurus pakistani [20] [21], and north Kinwa and Mari Bohri skeletons and lower Sangiali fossils from Pakistan of Saraikimasoom vitakri [22] [23] gspsaurid stocky poripuchian titanosaurs. Further the holotypic (Figures 1-3) and lower Bor exemplar (Figure 4) skeletons bones are consistent with skeletons of other 3 recognized taxa from Indo-Pakistan. The holotypic (Figures 1-3) and referred (Figure 4, Figure 5) specimens from Pakistan are housed in the Museum of the Geological Survey of Pakistan, Quetta.

Some fossils from India referred to Pakisaurus balochistani [24] (and here) like an isolated tooth GSI 20,006 from Rahioli [33] [34]; braincase GSI K27/497 [35]; axis from Nand [36]; caudal vertebra K20/315, poorly preserved tibia K20/321 and fibula K27/489 from Bara Simla [35] [37]; caudal vertebra K27/504, braincase GSI K27/497 (Figure 5), caudal vertebra K20/317 and chevron from Bara Simla [35] and middle caudal vertebra (NHMUK R16481) from Chota Simla of Jainosaurus (=Antarctosaurus) septentrionalis [16]. The tall, flat sided and ventrally not reduced caudal vertebrae, slender flattened tibia and teeth with almost constant diameter are the key elements of Pakisaurus balochistani.

The Jainosaurus (=Antarctosaurus) septentrionalis limb materials from Chota Simla [16] [32] are referable to Gspsaurus pakistani due to its key element stocky proximal tibia. Further right scapula [35] of Jainosaurus (=Antarctosaurus) septentrionalis show affinity to Isisaurus colberti. The distinct part of distal humeri from India [35] destroyed and not preserved. In this way Jainosaurus (=Antarctosaurus) septentrionalis [35] bones show multiple taxa affinity and seems no stability. These Indian fossils are referred due to possible similarity with caudal vertebra (tall and the dorsal and ventral mid caudal width ratio 1) and flattened and transversely thin and narrow bone tibia and transversely narrow distal scapula. Braincase referred due to finding large sized and different than Gspsaurus and Saraikimasoom and also suggested by a few previous researchers. This materials from India referred to Pakisaurus balochistani due to tall midcaudal with ratio of mid caudal width above and below is about 1 i.e. in ventral view the dorsal width are not clearly observed [24]. The Pakisaurus named after the host country Pakistan and species P. balochistani named after the Balochistan province, Pakistan [8] [9].

Geological Formation and Age: The holotypic and referred materials were collected from the Latest Cretaceous (latest Maastrichtian; 67 - 66 Ma) Vitakri Formation of Fort Munro Group [14] from Pakistan [3] [4] [9] and Lameta Formation from India. The Pab Formation was divided into lower member Dhaola, middle member Kali and upper member Vitakri [3]. Later on the Vitakri Formation was established by [14] which include the meandering river deposits as sandstone units alternated by two overbank red, green and mottled coloured mud units. Two mud units of the Vitakri Formation (which is the upper part of previous Pab Formation) are the host of these fossils. Most of these fossils found as surface finds as clusters on the shale units, however a few were excavated partially and a few were found as isolated. Vitakri Formation varies from 1 m to 35 m in thickness deposited by alluvial fresh water terrestrial deposits. In Sulaiman (middle Indus) basin where these bones are found so far, the Vitakri sediments consist of two red mud units (mostly red and maroon shale with subordinate green and khaki shale) of over bank deposits and two sandstone units (thin to thick bedded, grey to white muddy quartzose, not clean) of meandering river channel deposits. The lower red mud units-over bank deposits (4 - 14 m), middle sandstone unit (3 - 4 m), upper shale/mud unit (3 - 11 m) and upper sandstone unit (4 - 7 m) are found in the eastern Sulaiman foldbelt [3]. At places the shale units and the middle sandstone unit is covered by scree. The Vitakri Formation (Ziarat laterite) is 0.3 m to 2 m in the Ziarat and Sanjawi areas of Ziarat district [3] while it is 1m thick (laterite and carbonaceous shale just like of latest Cretaceous Kingri coal of Vitakri Formation in eastern Sulaiman Basin) exposed in the Sor Tangi section of Zhob district located between Musafar Pur to Mina [38] [39], as tectonic set up Sor Tangi is located at the western extremity of Western Indus Suture and eastern extremity of North Balochistan basin. The Vitakri Formation is about 30 - 35 m thick (red sandstone with minor red muds) in the Bara and Khadro sections of Laki thrusted anticline, Sindh Province, southern Pakistan. The lower contact of Vitakri Formation found with Dhaola member of Pab Formation (white colored washed sandstone of Pab Formation in eastern Sulaiman) and Kali member of Pab Formation (only difference is the red and maroon muds of Vitakri Formation and stratigraphic position) in western Sulaiman foldbelt and upper contact with marine limestone and green shale and sandstone of Sangiali Formation or Rakhi Gaj formation in Sulaiman basin and Khadro or Bara Formation in eastern Kirthar basin. The Vitakri Formation in Laki anticline of eastern Kirthar (Sindh Province) is typically represented by red to brown colored sandstone and shale which has lower contact with white colored sandstone of Pab Formation, exposed in the thrusted core of Laki anticline [26]. The Sangiali and Khadro formations are found clearly only in type sections, in other places their finding and identifications are difficult. However the Rakhi Gaj Formation is well exposed in Sulaiman and western Kirthar basins while its coeval Bara Formation is well exposed in eastern Kirthar. The lower contact of Vitakri Formation (Ziarat laterite) found with Parh Limestone and upper contact with marine limestone of Dungan Formation in Sanjawi-Ziarat areas. The lower contact of Vitakri Formation found with Pab and upper contact with Paleocene Nisai Limestone in Sor Tangi section of Zhob District. The equivalent of Vitakri formation in Upper Indus basin is Indus Formation (Latest Cretaceous and Infra Tertiary boundary; laterite, bauxite, glauconite and chamosite; previously a part of basal Hangu Formation).

Pakistan is the best place for the study of KT mass extinction and latest archosaurs and other biotas from where the latest archosaurs (titanosaurian sauropod and theropod dinosaurs, mesoeucrocodiles) and other biotas became extinct and the existing of wide exposures of marine and non-marine KT or KPg boundary. The characters of the latest titanosaurs and other archosaurs and biotas, end Cretaceous their mass extinction, wide exposures of terrestrial and marine Cretaceous-Tertiary boundary/KT boundary or Cretaceous-Paleogene boundary K-Pg boundary and dispersal of Cenozoic biotas from Pakistan have attracted the world scientists. In the eastern surrounding areas of Balochistan, the south Punjab also host the Vitakri Formation (and its vertebrates) exposed in Rakhi Gaj area and Mian Ghundi anticline in the Khar Fort Munro area of Dera Ghazi Khan, and Chitri and Dragal-Maarri areas of Rajanpur district, south Punjab.

Reference [40] reported Orbitoides (Lepidorbitoides) minor from lower part of the unit (Pab and Mughalkot formation) in Rakhi Nala representing early Maestrichtian age. Reference [41] reported mixed benthonic-pelagic foraminifers of Maastrichtian age from type locality area of Pab Formation. Reference [42] reported Globotruncana aff. G. linnei, Lituola sp., Omphalocyclus macropora, Orbitella media, Orbitoides sp., Siderolites sp., from Moro area in Moro (=Pab) formation with Maestrichtian age. According to dinosaur and associated vertebrate fossils, stratigraphic position and previous work, the reference [43] considered the age of Vitakri Formation as latest Maastrichtian or latest Cretaceous (67 - 66 Mya/Million years ago) [44]. The Lameta Formation from India (coeval of Vitakri Formation from Pakistan) is the host of latest Cretaceous vertebrates from India. Its age latest Maastrichtian (67 - 66 Mya) is based on the microfossils, vertebrates, and the associated basal flows of the Deccan lavas [1] [45] [46].

The Isisaurus colberti shares with Poripuchia because all the reported its caudal vertebrae especially distal caudals from India and Pakistan show procoely. The Isisaurus colberti shares with Pakisauridae (medium to large sized slender titanosaurs) the ratio of mid transverse width above and below of mid caudal centrum is about 1.00 i.e. the ventral view of mid caudal centra are not compressed or slightly compressed and slender flattened tibia with anteroposteriorly broad distal ends, while Gspsauridae is represented by ventrally reduced mid caudals and stocky tibia with transversely broad distal ends.

Isisaurus colberti is represented by one associated partial skeleton from India [25] and three associated partial skeletons from Pakistan. These three associated partial skeleton includes the holotypic caudal vertebrae of Sulaimanisaurus gingerichi [9] from south Kinwa 4; referred slender flattened tibia, fibula and metatarsal (Figure 6) of Sulaimanisaurus gingerichi from Zubra peak 7; and slender humerus and femur (Figure 6) of Sulaimanisaurus gingerichi from lower Sangiali 1. It is necessary to mention that the Sulaimanisaurus gingerichi fossils are referred to Isisaurus colberti due to more similarity and recent recognition of 4 taxa of titanosaurs out of fifteen named titanosaurs from Indo-Pakistan subcontinent. So now these three associations from Pakistan are being referred to Isisaurus colberti which have filled many significant missing gaps (Figure 6) of Isisaurus colberti for the understanding of missing links and fuller anatomical features. Isisaurus colberti [25] have many missing bones especially cranial, hind limb and foot bones. Here the author referred some missing bones of hind limb and foot bones from Zubra Peak 7, and some overlapping distal humerus and distal femur bones from Sangiali 1, Pakistan (Figure 6). Isisaurus colberti has

flattened or transversely thin proximal tibia with relatively less anteroposteriorly broad triangular distal view of distal ends (Figure 6) than Pakisaurus balochistani (Figure 7) which have broader distal end. The anteroposteriorly width of tibial shaft is about 3 times the transverse width, while in Gspsaurus it is more than 2 times and in Saraikimasoom it is subcircular or less than 1.5 times. The diagnostic taxon Isisaurus colberti have flattened tibia. The outer morphology, proportional measurement, shape and features allow its identification and assignment to Isisaurus colberti because its proportion of distal tibia is relatively less (16 cm anteroposterior width) than the lower Bor distal tibia (about 20 cm anteroposterior width) of Pakisaurus while the proximal anteroposterior width are approximately same as 25 cm. It is likely that both may have about 80 - 100 cm length. It is also necessary to mention that the anteroposterior breadth of proximal tibiae are almost same in all main describing tibia but its transverse width is variable and allow their distinction with other characters among each others (Figure 7). Its ratio of anteroposterior width of distal end (16 cm) to anteroposterior width of proximal end (25 cm) is 0.64 while the ratio of Pakisaurus tibia is high as 0.80.

The distal humerus (Figure 6) has no expanded and anteriorly exposed radial condyle like its holotypic humerus, and unlike other poripuch titanosaurs from Indo-Pakistan. The right femur has same size as the distal humerus and both found from same site of lower Sangiali 1, so believed associated.

The distal femur (Figure 6) is slender and has triangular shaped small hollow cavity observed in the cross sectional view.

Fibula (Figure 6) has medial crest trending dorsoposteriorly to anteroventrally and terminating at mid way. Further this fibula has no rugose parallel structures (Figure 6) unlike the fibula of Pakisaurus balochistani (Figure 3). Metatarsal is thick subcircular shaft and convex shaped end.

The recent [20] [21] [22] [23] [24] [27] and present work recognized four titanosaur taxa out of the total 15 named taxa of titanosaurs from Indo-Pakistan. These recognized four taxa from South Asia are Pakisaurus balochistani and Isisaurus colberti pakisaurid Poripuch slender titanosaurs, and Gspsaurus pakistani and Saraikimasoom vitakri gspsaurid Poripuch stocky titanosaurs. Further this assessment is consistent with the clues of four taxa of titanosaur from Madagascar.

Most of the workers recognized three or four titanosaur taxa from Indo-Pakistan [1] [20] [21] [22] [23] [24] [27] [35] [75]. The fossils reported by [35] show three titanosaurs while fourth titanosaur Isisaurus colberti was reported later in 1997 [25]. Reference [16] recognized two titanosaur taxa from Indo-Pakistan. The present work and other recent discoveries [21] [23] from Pakistan since 2000 to so far revealed at least four titanosaurs with four diverse cranial and postcranial fossils like skull and teeth, tibiae, humeri, femora, scapulae, caudal vertebrae and others. The major problem in considering only two titanosaur taxa is the referring of tetra diverse and diagnostic fossils collected from India and Pakistan so far. While this problem is solved, when [20] [21] [22] [23] [24] and present work revealed four recognized titanosaur taxa from Indo-Pakistan on diagnostic tetra diverse associated cranial and postcranial skeletons especially tibiae. Their typical key elements and comparison are being presented here.

Four typical key tibiae of Poripuch titanosaurs from Indo-Pakistan: Two types of slender, flattened, transversely compressed tibia (described above), and two types of stocky and transversely expanded tibia described by [21] [23] along with other bones resolved certainly the long standing controversy regarding the number of taxa of titanosaurs from Indo-Pakistan. Now it became certain by four types of tibia (Figure 7) along with other associated cranial and postcranial

materials. The outer morphology, proportional measurement, shape and features of tibiae of recognized four taxa allow its distinction. Saraikimasoom has quite robust and stockiest (most expanded transversely and anteroposteriorly approaches their equal widths), proximal tibia with equal anteroposterior and transverse width (subsquare shaped femoral articular surface in proximal view) with subsquare to subcircular shaped mid shaft cross section (anteroposteriorly width of shaft may be about same or slightly more than transverse width), and quite robust transversely broad suboval to subrectangle shaped distal tibia (Figure 7), Gspsaurus has robust and stocky (expanded anteriorly and transversely), proximal tibia (anteroposteriorly slightly long, asymmetric biconvex lense shaped femoral articular surface in proximal view) with oval shaped mid shaft cross section (anteroposteriorly width of shaft may be about or slightly more than twice transverse width), and quite robust transversely broad subrectangle shaped distal view of distal tibia (Figure 7), Isisaurus colberti has slender transversely compressed proximal tibia, with anteroposteriorly broad triangle shaped distal view of distal tibia (Figure 7), and Pakisaurus has quite slender flattened and transversely compressed proximal tibia with anteroposteriorly quite broad/more broader distal tibia than Isisaurus colberti (Figure 7).

Jainosaurus (=Antarctosaurus) septentrionalis is based on braincase, vertebra and left and right scapula two left humeri and one or two weathered bones reported from Bara Simla India [35] which represents dual affinity and chimera nature, and further also no associated other materials. Two braincases are reported from Pakistan [21] [23] and four braincases from India [76]. Pakistani braincases have constricted sagital groove and w-shaped occipital condyle and all Indian braincases have D-shaped condyles with no sagital groove, while as a whole all six are different. This braincase GSI K27/497 of Jainosaurus (=Antarctosaurus) septentrionalis [35] referred to Pakisaurus balochistani [24] due to large size with D-shaped condyle and distinguished from W-shaped condyle of braincases of Gspsaurus [20] [21] and Saraikimasoom [22] [23], and D-shaped small sized braincase of Isisaurus colberti. The scapula has affinity to Isisaurus colberti due to relatively longer articular surface for coracoids, while this articular surface is relatively shorter in the Pakisaurus, Saraikimasoom and Gspsaurus. Pakisaurus has transversely relatively less expanded distal scapula, Saraikimasoom has transversely relatively expanded distal scapula, and Gspsaurus has transversely relatively more expanded distal scapula. Further the two humeri of Jainosaurus (=Antarctosaurus) septentrionalis [35] are also different with each other and may belong to two different taxa. The vertebra of Jainosaurus (=Antarctosaurus) septentrionalis [35] may be referable to Pakisaurus. The Chota Simla assemblages of Matley [32] were referred to Jainosaurus (=Antarctosaurus) septentrionalis [16]. Again the materials described by [16] have dual affinity. The vertebra described by [16] is referable to Pakisaurus due to tall, flat sided and ventrally not reduced. The associated limb elements described by [16] referable to Gspsaurus [21] due to transversely expanded and anteroposteriorly long lense shaped typical key tibia.

Diverse femora of Poripuch titanosaurs from Indo-Pakistan: Four types of femora of four recognized taxa of titanosaurian sauropods are reported from Indo-Pakistan. Their comparisons can be explained as below. The Saraikimasoom vitakri [23] and Gspsaurus pakistani [21] femora are relatively more expanded anteroposteriorly than the Pakisaurus balochistani and Isisaurus colberti femora. The Pakisaurus balochistani shows (wavy style) rounded proximal one third deflection and then became vertical straight just close to greater trochanter while Saraikimasoom have medially deflection with straight line lateral profile from deflection point to greater trochanter. The Saraikimasoom vitakri and Gspsaurus pakistani show mid shaft transverse width 2 times than anteroposterior thickness while the Pakisaurus balochistani and Isisaurus colberti have 3 times mid shaft transverse width than anteroposterior thickness. The Saraikimasoom vitakri and Gspsaurus pakistani show relatively more expanding anteroposteriorly tibial and fibular condyles than Pakisaurus balochistani and Isisaurus colberti. The Saraikimasoom vitakri and Gspsaurus pakistani have rugosities on the distal femur which extended on to shaft while Pakisaurus balochistani and Isisaurus colberti show no rugosities extension.

Diverse humeri of Poripuch titanosaurs from Indo-Pakistan: The diverse morphologies of humeri were recorded for four recognized taxa of titanosaurian sauropods from Indo-Pakistan. First morphology of humerus [25] is large and transversely more expanded belongs to Isisaurus colberti, which represents humerus without expanded radial distal condyle which is not expanded well anteriorly. Second morphology of humerus (presented here) is also large and transversely expanded belongs to Pakisaurus balochistani, which represents distal condyle expanded or well divided especially radial condyle is expanded and exposed anteriorly and situated almost at the transverse centre. Third morphology of humerus [21] is moderate in size belongs to Gspsaurus pakistani, which represents prominent medial process of medial limb of proximal humerus is more extruded in the medial side (with possibly distal condyle expanded or well divided). Fourth morphology of humerus [23] is relatively small belongs to Saraikimasoom vitakri which represents distal humerus with expanded radial condyle exposed anteriorly but situated offset from centre. The deltopectoral crest is shifted medially shown in the Sangiali humeri of Saraikimasoom Vitakri and also like the Chota Simla humerus of Gspsaurus pakistani.

Five types of caudal vertebrae of titanosaurs from Indo-Pakistan: Five types of vertebrae especially caudal vertebrae [9] of poripuch titanosaurs were diagnosed from Indo-Pakistan subcontinent. First type, tall mid caudals with ratio of mid transverse width above and below of centrum is about 1 belong to Pakisaurus balochistani; slightly tall mid caudals with ratio of mid transverse width above and below of centrum is about 1.3 to 1.5, belong to Gspsaurus pakistani; squarish to broad mid caudals with ratio of mid transverse width above and below of centrum is about 1.5 to 2, belong to Saraikimasoom vitakri; squarish mid caudal with ratio of mid transverse width above and below of centrum is about 1, belong to Isisaurus colberti or Sulaimanisaurus gingerichi; squarish mid caudal with ratio of mid transverse width above and below of centrum is slightly less than 1, belong to Khetranisaurus barkhani.

Diverse skulls of titanosaurs from Indo-Pakistan: Four braincases were described from the latest Maastrichtian Vitakri Lameta Formation in Bara Simla and Dongargaon localities of central India and Rahioli locality of western India [76]. Two braincases reported from the latest Maastrichtian Vitakri Lameta Formation in Alam [21] and Eastern Top Kinwa [23] localities of Balochistan, central Pakistan. The Kinwa locality braincase assigned to Saraikimasoom vitakri and Alam locality braincase is part of holotype of Gspsaurus pakistani. All these braincases are different from each other. In this way more than four types of braincases were reported from Indo-Pakistan like large braincase having thick quadrangular occipital condyle with median cut, ventral W-shaped surface and dorsal reverse W-Shaped surface and almost straight lateral sides of Gspsaurus pakistani [21]; relatively small braincase with convex lateral sides and ventral feeble W-shaped of Saraikimasoom vitakri [23]; large braincase with D-shaped and convex lateral sides of Pakisaurus balochistani; and small braincase with D-shaped and lateral convex sides belong to Isisaurus colberti.

Three or four types of snout/rostrum (skulls) were reported from Indo-Pakistan. First type of small skull of Gspsaurus pakistani having V shaped mandible teeth row with circular to subcircular, long slender, recurved and conical teeth particularly characterised by decreasing teeth diameter from base to tip [20] [21]. Second type of very small skull of Saraikimasoom vitakri having U shaped mandible teeth row with circular to subcircular, long slender, recurved and conical teeth particularly characterised by decreasing teeth diameter from base to tip [22] [23]. Third type of Pakisaurus balochistani circular to subcircular, long slender and recurved teeth with constant tooth diameter from base to tip (except tip) similar to teeth and may be similar to the skull of Rapetosaurus [27]. The fourth type of skull may belong to Isisaurus colberti.

The Cretaceous dinosaur fauna of Indo-Pakistan has remained poorly understood because of a lack of associated and articulated remains, proliferation of named species, and an incomplete understanding of the clades present [16]. Due to recent discoveries from Pakistan, the above problems are resolved. The recent work [20] [21] [22] [23] [24] [27] and present work recognized four titanosaur taxa out of the total 15 named taxa of titanosaurs from Indo-Pakistan. Recognized four taxa from South Asia are Pakisaurus balochistani and Isisaurus colberti pakisaurid Poripuch slender titanosaurs, and Gspsaurus pakistani and Saraikimasoom vitakri gspsaurid Poripuch stocky titanosaurs. These recognized four taxa of titanosaurs based on the following associated partial skeletons. These associated skeletons provide a fuller understanding of its anatomy and phylogenetic affinities.

Pakisaurus balochistani is represented by two associated partial skeletons from Pakistan like the holotypic vertebral and appendicular elements [77] (Figures 1-3) from Kinwa (the western site of South Kinwa) and its exemplar associated skeleton of vertebral and mostly appendicular elements (Figure 4) from lower Bor 2 locality. The Pakisaurus balochistani holotypic associated partial skeleton of south Kinwa includes the cervical, cervicodorsal, dorsal, sacral and caudal vertebrae, sternal, a pair of scapula (left and right scapula), right humerus, radius, a pair of ulna (left and right ulna), ilium, right femur, a pair of fibula (left and right fibula), manus/pes foot bones (Figures 1-3).

The other associated partial skeleton of Pakisaurus balochistani found from lower Bor 2 includes the caudal vertebrae, sternal, a pair of scapula (left and right scapula), right humerus, radius, a pair of ulna (left and right ulna), ilium, right femur, a pair of fibula (left and right fibula), and manus/pes foot bones (Figure 4). Here the slender flattened tibia (Figure 4, Figure 7) is the major typical key element for the diagnosis of Pakisaurus balochistani. The four typical key tibiae are found from Pakistan which shows affinity to four recognized titanosaur taxa from Indo-Pakistan. Besides these two associated partial skeletons, many bones are being referred to Pakisaurus balochistani from Pakistan (Figure 5) and India.

Isisaurus colberti is represented by one associated partial skeleton from India [25] and three associated partial skeletons from Pakistan (added here). Three associated partial skeleton includes the holotypic caudal vertebrae of Sulaimanisaurus gingerichi [9] from south Kinwa 4, slender flattened tibia, fibula and metatarsal (Figure 6) (Figure 7) of Sulaimanisaurus gingerichi from Zubra peak 7 and slender humerus and femur (Figure 6) of Sulaimanisaurus gingerichi from lower Sangiali 1. It is necessary to mention that the Sulaimanisaurus gingerichi fossils are referred to Isisaurus colberti due to recent recognition of 4 taxa of titanosaurs out of fifteen named titanosaurs from Indo-Pakistan subcontinent. So now these three associations from Pakistan are being referred to Isisaurus colberti which have filled many missing gaps (Figure 6) of Isisaurus colberti for the understanding of fuller anatomical features.

Gspsaurus pakistani is represented by three associated partial skeletons from Pakistan and one associated partial skeleton from India [21]. First the Gspsaurus pakistani holotypic cranial, vertebral and appendicular skeleton from central Alam 19 which includes the partial skull with braincase, cervical, dorsal and caudal vertebrae, partial ilium or sternal, a pair of scapula (left and right scapula), radius, left femur, and a pair of tibia (left and right tibia). Second the associated partial skeleton of Gspsaurus pakistani found from Top Kinwa 16 locality includes the dorsal, sacral and caudal vertebrae, sternal, a pair of scapula (left and right scapula), radius, a pair of ulna (left and right ulna), ilia, left tibia fibula and a pair of fibula (left and right fibula). Third the associated partial skeleton of Gspsaurus pakistani found from Mari Bohri 15 locality includes the first biconvex caudal and other procoelous caudal vertebrae, right scapula, right pubis and right femur. The fourth associated partial skeleton of Gspsaurus pakistani reported from Chota Simla India by [16] [32] includes a pair of humeri (left and right humerus), left radius, left femur, left tibia and left fibula. Besides these four associated partial skeletons, many bones are being referred to Pakisaurus balochistani from Pakistan and India.

Saraikimasoom vitakri is represented by four associated partial skeletons from Pakistan [23]. First the Saraikimasoom vitakri holotypic snout including the articulated lower and upper jaw bones with full teeth rows and some other skull bones from South Kinwa 4. Second the associated partial skeleton of Saraikimasoom vitakri found from north Kinwa 4n locality includes jaw bone with 6 complete teeth, cervical, dorsal and caudal vertebrae, humerus, radius, pubis, a pair of femur (left and right femur) and a pair of tibia (left and right tibia). Third the associated partial skeleton of Saraikimasoom vitakri found from Mari Bohri 15 locality includes the cervical, dorsal, first biconvex caudal and other procoelous caudal vertebrae, left sternal, left humerus, left ulna, left acetabulum, left femur and left tibia. Fourth possible associated partial skeleton of Saraikimasoom vitakri found from mid Sangiali 1 locality includes the cervical, cervicodorsal, dorsal and caudal vertebrae, left scapula, left humerus, left coracoid, left and right femur, left tibia and left fibula, while this site also produced two more proximal humerus and one more cervicodorsal vertebra revealing three animals of Saraikimasoom vitakri at mid Sangiali 1. Besides these four associated partial skeletons, many bones referred to Saraikimasoom vitakri from Pakistan and India.

Further theropods [78] [79], mesoeucrocodiles [78] [80] [81], and pterosaurs [27] [78] were also were also found from the latest Cretaceous (67 - 66 Million years ago/Mya) Vitakri Formation [4] [15] [16] of Fort Munro Group [16] from Pakistan. First large sized theropod Vitakridrinda sulaimani is represented by holotypic skeleton [78] includes more than 10 teeth and a few cranial small bones, tall dorsal vertebra and a pair of femora (left and right femur) from Alam 19 type locality [78], and referred materials include possibly partial skeleton of tall dorsal vertebrae, subcircular caudal vertebra, whiplash elongated distal caudal centrum and metatarsals from Top Kinwa 16 [78], tall dorsal vertebra from Sangiali 1 [78], and anterior caudal vertebrae from Mari Bohri 15 [78]. Second large sized theropod Vitakrisaurus saraiki [79] is represented by holotypic skeleton [78] includes almost complete manus with articulated and associated its most of the elements, anterior and mid caudal vertebrae, proximal ulna, cross section of humerus and limb bones found from mid-Bor 2 type locality [78], and referred materials include subcircular cylindrical dorsal vertebra from Shalghara 3 locality of Vitakri dome area, Barkhan district, possibly leg bones [78] from Karkh area of Khuzdar district, Pakistan, and a caudal vertebra with two chevrons [35] [37] [78] from Bara Simla India. Medium to large sized mesoeucrocodile Induszalim bala [80] is represented by holotypic skeleton [78] includes snout/rostrum, rib, caudal vertebrae, proximal humerus and proximal ulna, metacarpals, ilium, femur, tibia articulated with fibula, and metatarsals found from mid Bor 2 type locality and referred materials include anterior snout with teeth, dentary ramus with 4 alveoli with partial teeth, jaw ramus with two teeth sandwiched by a diastema, anterior snout with articulated 2 teeth (one tooth on right and one on left jaw ramus) found from Shalghara 3, and dentary ramus with articulated four spaced teeth from Bor 2, and dorsal vertebra from Top Kinwa 16, Barkhan district, Balochistan and a partial rib/phalanges from south western vicinity of Khuzdar town, Balochistan. Medium to large sized mesoeucrocodile Pabwehshi pakistanensis [81] is represented by holotypic snout articulated with dentary found from Top Kinwa 16 and referred dentary symphysis from Shalghara 3. Medium to large sized mesoeucrocodile Sulaimanisuchus kinwai [82] is represented by holotypic dentary symphysis with articulated teeth and proximal humerus from south Kinwa 4 or 4s. Medium to large sized pterosaur Saraikisaurus minhui [78] is represented by holotypic beak or dentary with articulated 8 teeth (some teeth are overlapped) found from Top Kinwa 16, Barkhan District, Pakistan [78] and referred jaw with overlapped teeth [83] from Kotah, Rajasthan, India [78]. Further recently discovered basilosaurid, baluchithere rhinoceros, horses, sea cow, proboscidean, eucrocodile, pterosaurs, plesiosaur, fishes, invertebrates and wood fossils, and footprints and trackways were reported from Pakistan [27]. All these fossils from Pakistan and their significant localities are geoheritage and paleobioheritage and assets of Pakistan which needs their protection [84] [85] [86] [87] and also considered significant remains from Pakistan which have no parallel from India [88]. These latest Cretaceous materials of titanosaurs [20] [21] [22] [23] [24] and present work, theropods [78] [79], Mesoeucrodiles [78] [80] and pterosaurs [27] [78] revealed paleobiogeographic Gondwanan affinity.

Due to lack of associated skeletons of slender and large titanosaurs from Indo-Pakistan (South Asia), this finding of holotypic associated skeleton from south Kinwa and referred associated skeleton from lower Bor, Balochistan, Pakistan is providing significant features of Pakisaurus balochistani a slender and large titanosaur from Indo-Pakistan subcontinent. There is also lack of cranial and associated postcranial remains of titanosaurs in Indo-Pakistan but this cranial, and associated postcranial remains of Pakisaurus balochistani slender and large titanosaur from Indo-Pakistan provides significant and distinct cranial and postcranial features for the comparison, evolutionary and phylogenetic studies of titanosaurs in the globe.

Isisaurus colberti which is based on associated postcranial skeletons has many important missing links. Among these some significant missing links especially hind limb elements, are partly filled and added here. This filling of missing gaps of Isisaurus colberti the slender titanosaur from Pakistan is unique gift and provided the key elements especially slender flattened and transversely compressed tibia with key features for future phylogenetic studies.

So far no any comparison of Indo-Pakistan titanosaur fauna is made but here a comparison of cranial, vertebral, appendicular and limb elements of four recognized taxa of titanosaurs from Indo-Pakistan is presented. Recently the four recognized titanosaur taxa from Indo-Pakistan include the two slender titanosaurs like Pakisaurus and Isisaurus and two stocky titanosaurs like Gspsaurus and Saraikimasoom.

Fortunately the four typical key tibiae of four recognized titanosaur taxa associated with other elements were found from Pakistan. There was a long standing controversy and issue regarding the valid and coexisting titanosaur taxa in Indo-Pakistan subcontinent. Luckily the findings of four typical key tibiae (along with associated cranial and postcranial skeletons) discarded the hypothesis of two titanosaur taxa from Indo-Pakistan subcontinent and revealed two distinct slender poripuchian titanosaurs and two distinct stocky poripuchian titanosaurs from Indo-Pakistan subcontinent.

The extension of procoely into anterior and middle caudal vertebrae has been considered a feature of lithostrotian [51] [52] [53] [54] [55], while the extension of procoely into anterior and middle and posterior caudal vertebrae from Indo-Pakistan subcontinent has been considered a feature of Poripuchia [4] [27] titanosaurs. Poripuch is the Saraiki language word means full tail (with procoelous vertebrae). The Poripuchia titanosaurs consist of all procoelous caudals including the distal caudals also; however in some taxa especially stocky titanosaurs the first caudal is biconvex. In pakisaurids and gspsaurids all the caudal vertebrae found so far belong to anterior, middle and distal caudal vertebrae are procoelous (except first biconvex caudal). The Poripuchia is the most inclusive clade containing all caudal procoelous (except first biconvex caudal in few taxa). The Poripuchia is the most inclusive clade containing Pakisaurus and Isisaurus of pakisaurids, and Gspsaurus and Saraikimasoom of gspsaurids the derived titanosaurs.

Further many cranial and postcranial associations of recognized two slender and two stocky titanosaurs from Pakistan and also India are presented and discussed. Pakisaurus balochistani slender titanosaur has two associations from south Kinwa and lower Bor in Pakistan, while Isisaurus colberti slender titanosaur has one holotypic association from Dangargaon India and three brief associations from Pakistan, which is the holotypic and exemplars of Sulaimanisaurus gingerichi, here being referred to Isisaurus colberti. Besides slender titanosaurs, the stocky titanosaurs are relatively more common in Pakistan and also have more associations of cranial and postcranial skeletons. Gspsaurus pakistani have three association from Pakistan like Alam, Top Kinwa, Mari Bohri and mid Bor of Pakistan and one association from the Chota (Chhota) Simla of India. Saraikimasoom vitakri have one holotypic snout (including articulated lower and upper jaws and complete teeth row) found from south Kinwa, and other three associations from Pakistan like north Kinwa, Mari Bohri, mid Sangiali (probably), south Zubra Basti Nala and Grut localities of Pakistan.

The author declares no conflicts of interest regarding the publication of this paper.

Malkani, M.S. (2020) Pakisaurus balochistani (Poripuchia, Slender Titanosauria, Sauropoda) Associated Skeletons Found from the Latest Maastrichtian Vitakri Formation of Pakistan and Referred Fossils from India; Filling of Important Missing Links of Isisaurus colberti Titanosaur Found from Pakistan. Open Journal of Geology, 10, 408-447. https://doi.org/10.4236/ojg.2020.104019