[D] Rocasaurus muniozi [Su] [sG] [T]
Describer
Salgado & Azpilicueta, 2000
Time
Cretaceous Late Campanian Maastrichtian
Classification
Saurischia Sauropodomorpha Sauropoda Titanosauria
Diet
Herbivore
Fossilsite
Allen Formation, Provincia de Neuquen, Argentina
Length
8 meter
Info
Genus - Typespecies - Skull
Named after Roca city, nearly to the locality (south of Roca City) where it was found 90 kilometers south-east of the capital Neuquin.
Salgado, L. and C. Azpilicueta. 2000. Un nuevo saltasaurino (Sauropoda, Titanosauridae) de la provincia de Río Negro (Formacíon Allen, Cretácico Superior), Patagonia, Argentina. Ameghiniana 37 (3):259-264.
[A new saltasaurine (Sauropoda: Titanosauridae) from the province of Río Negro (Allen Formation, Upper Cretaceous), Patagonia, Argentina]
Translated by Matthew C. Lamanna, January 2001
Original English abstract[/b]
A new saltasaurine taxon based on a femur, pelvic bones and dorsal and caudal vertebrae is described. The closest relationships of the new taxon are with Saltasaurus loricatus Bonaparte and Powell from northwestern Argentina. These species share caudal vertebrae bearing a ventral depression divided by a longitudinal septum. The record of [Saltasaurinae] is thus limited to the Upper Cretaceous of Argentina, with three distinct taxa: Saltasaurus loricatus, Neuquensaurus australis Lydekker and Rocasaurus muniozi n. gen., n. sp.
Introduction
The [Saltasaurinae] (Powell, 1986, 1992) are a group of titanosaurids of modest size (7-8 meters in length), characterized by two synapomorphies, the centra of the caudal vertebrae low and the anterior border of the neural spine located posteriorly with respect to the anterior margin of the postzygapophyses in the middle caudals (Salgado et al., 1997). Powell (1986) recognized two species of saltasaurines, both from the Upper Cretaceous: Saltasaurus loricatus Bonaparte and Powell 1979, originating from the locality of El Brete, province of Salta, and Neuquensaurus australis Lydekker, recorded in the localities of Cinco Saltos and Neuquén, in the provinces of Río Negro and Neuquén (Powell, 1986). The characters that diagnose each one of them were enumerated by Powell (1986). The validity of the third species of [Saltasaurinae], [Neuquensaurus robustus] Lydekker 1893, was put in doubt by this author (Powell, 1986), who minimized the differences with Neuquensaurus australis indicated by Huene (1929) in his monograph on the dinosaurs of Argentina.
In Patagonia, the remains of [saltasaurines] are found associated to those of other dinosaurs, including other titanosaurids. In the case of the locality of Cinco Saltos (province of Río Negro), where a great number of materials have been collected, Neuquensaurus australis is recorded with two other titanosaurids: [Titanosaurus araukanicus] Huene, 1929 and Pellegrinisaurus powelli Salgado, 1996 (Powell, 1986; Salgado, 1996).
In this work we present materials corresponding to a new genus and species of [Saltasaurinae] and discuss its phylogenetic relationships. The same originate from the locality of Salitral Moreno, situated in the interior of the province of Río Negro that until the present has offered an important number and variety of remains of dinosaurs, the titanosaurid Aeolosaurus sp. (Salgado and Coria , 1993), Nodosauridae indet. (Salgado and Coria, 1997), Lambeosaurinae indet. (Powell, 1987), Theropoda indet., [Chelonia] indet., and eggs attributable to [Titanosauridae] Titanosauria (Powell, 1986).
Abbreviations used: MPCA-Pv: Collection of Paleovertebrates of the Provincial Museum of Cipoletti “Carlos Ameghino”.
Systematics and description
Order Saurischia Seeley, 1888
Suborder Sauropodomorpha Huene, 1932
Infraorder Sauropoda Marsh 1878
Family [Titanosauridae] Titanosauria Lydekker, 1893
Subfamily [Saltasaurinae] Powell, 1992
Rocasaurus n. gen.
Type species
Rocasaurus muniozi n. sp.
Etymology
“Roca”, for the rionegrine city of General Roca, nearby the locality of Salitral Moreno; \\\\\\\"saurus” (Greek), lizard.
Diagnosis
The same of the type species by monotypy.
Rocasaurus muniozi n. sp.
Holotype
MPCA-Pv 46 (figures 2-6): a juvenile individual represented by a cervical centrum, a cervical neural arch, two dorsal centra, three dorsal neural arches, two sacral neural arches, a middle caudal vertebra, a middle-posterior caudal vertebra, two ischia, a left pubis, a left ilium, a fragment of the right ilium and a left femur.
Referred material
Three anterior caudal bodies (MPCA-Pv 47, 48, and 60), a middle caudal body (MPCA-Pv 49), a posterior caudal body (MPCA-Pv 50) and six distal caudal bodies (MPCA-Pv 51-56). Cf. Rocasaurus sp. (figures 8.a-c): an anterior caudal (MPCA-Pv 57), a middle caudal (MPCA-Pv 58), a posterior caudal (MPCA-Pv 59).
Geographic provenance
Salitral Moreno, some 25 km to the south of the city of General Roca, province of Río Negro, Argentina
Stratigraphic provenance
Allen Formation, lower member (Powell, 1986). According to Powell (1986), the bearing levels are composed of yellowish medium to gross sandstones, sometimes adopting a gray greenish color, poorly sorted. The sequence evidences a fluvial paleoenvironment.
Age
Early Maastrichtian (Ballent, 1980) or Campanian-Maastrichtian (Uliana and Delapé, 1981).
Etymology
The species is dedicated to Sr. Juan Carlos Muñoz, attendant of the Area Paleontología of the Museo “Carlos Ameghino” of the city of Cipoletti, for his permanent support of the paleontological investigations in the region.
Diagnosis
[Saltasaurine] characterized by the presence of a distal expansion on the lateral margin of the pubis, ischium with an extensive lamina, caudal vertebrae with a deep ventral cavity divided by a longitudinal partition and with the posterior articulation notably depressed and extended ventrally forward.
Description
Cervical vertebrae
There is preserved a neural arch and a vertebral centrum that pertain to the holotype. The neural arch is presented deformed, in a manner that is not possible to find substantial differences with the pieces corresponding to other titanosaurids. In the body, notably compressed, due to post-mortem deformation, there is observed the parapophysis that projects laterally.
Dorsal vertebrae
There are recovered two strongly opisthocoelous dorsal centra, with a small pleurocoel in the form of an eye, a synapomorphic character of the Titanosauria (Bonaparte and Coria, 1993; Salgado et al., 1997). Three neural arches, one perhaps pertaining to a middle dorsal, and the other two to posterior dorsals present the diapophysis projected up, united to the parapophysis by means of diapo-parapophyseal laminae, and a prespinal lamina. The neural spine is wide and anteroposteriorly compressed in difference of Saltasaurus loricatus.
In the neural arch interpreted here as pertaining to a middle dorsal, it is not observed the inferior bifurcation of the infradiapophyseal lamina, that was proposed as a synapomorphy of the titanosaurids by Salgado et al. (1997), although it is clearly present in one of the posterior dorsals. In this last, that is found compressed laterally by crushing, also is observed a series of small laminae that connect the parapophysis with the infradiapophyseal lamina, at different heights. The more developed is interpreted here as the centro-parapophyseal lamina, a structure synapomorphic of the titanosaurids (Salgado et al., 1997).
In posterior view, two robust suprapostzygapophyseal laminae are observed, that connect the postzygapophysis with the neural spine and two infrapostzygapophyseal laminae. The diapo-postzygapophyseal lamina apparently has not been preserved completely for which it is not possible to determine its grade of development. In none of the cases is observed a hyposphene, to the same as the rest of the titanosaurids (Powell, 1986; Salgado et al., 1997).
Caudal vertebrae
All of the caudals are strongly procoelous and present a deep ventral cavity divided by a longitudinal partition, that constitutes one of the distinctive characteristics of this new species. The anterior caudals possess a short and wide body, of lateral faces dorsoventrally convex. Internally they possess a spongy structure composed by cells, equal to Saltasaurus. In the middle and posterior caudals, the posterior articulation of the vertebral centrum is extended ventrally forward, in a manner that, in lateral view, the concave inferior margin is notably short. The prezygapophyses are relatively short and the neural spine is reduced and inclined toward the rear, as in other [saltasaurines].
The posterior caudals attributed to Rocasaurus muniozi n. sp. are very dorsoventrally compressed, and they possess a smooth ventral depression, for it is understood that the strong cavity that is observed ventrally in the anterior and middle caudals, is less deep behind.
With relation to the vertebrae referred tentatively as Rocasaurus sp. (MPCA-PV 57 and 58, figure 8.a-c), is observed a characteristic ventral depression, divided by a longitudinal partition, and the great development of cavernous tissue. However, the neural arch is found here more displaced anteriorly and the posterior articulation does not present its ventral surface extended forward, for which perhaps it should be treated as a distinct species.
Ilium
The ilium posesses an amplified preacetabular lobe, of semicircular contour, characteristic of the Titanosauriformes (Salgado et al., 1997). It is twisted barely outside, a difference of that occurring in other titanosaurids, although it is possible that this owes itself to post-mortem deformation. In comparison with the ilium of Saltasaurus, it is noted that the postacetabular process is more large, the preacetabular lamina is more high and the pubic pedicel is slightly more elongated. Equal to the genus from northwest Argentina, the articulation with the ischium is barely insinuated, in contrast of that occurring in Neuquensaurus and other titanosaurids.
Pubis
The description corresponds to the left pubis. It is a sheetlike bone, possessing a dorso-lateral extension in the distal extreme that is not observed in other titanosaurids examined. The lamina is wide in the proximal portion, before the acetabular surface. The pubic foramen is closed and located in the upper half of the portion that articulates with the ischium. Not observed is the ventral longitudinal elevation characteristic of Saltasaurus loricatus (Powell, 1986).
Ischium
The pieces obtained correspond to a complete ischium and to one incomplete. It is a bone, short and laminar, in which the posterior process constitutes more than half of the length of the piece. The lamina of the ischium is extensive, in greater measure than that in Saltasaurus and Neuquensaurus . The length of the posterior process in relation with that of the iliac pedicel is higher than in Saltasaurus. The contact with the pubis is extensive, as in other camarasauromorphs (Salgado et al., 1997).
Femur
It is a straight bone, anteroposteriorly compressed. On the lateral margin, underneath the greater trochanter, is observed a strong bulge, a character that constitutes a synapomorphy of the titanosauriformes (Salgado et al., 1997; Wilson and Sereno, 1998). The minimum width of the diaphysis is found in the distal half of the bone, lower than in Saltasaurus and Neuquensaurus.
Discussion and conclusions
The characters that are observed in the materials that we have presented, indicate that Rocasaurus muniozi is more closely related with the species from northwest Argentina Saltasaurus loricatus. This would be supported by the presence of a ventral cavity divided by a longitudinal partition or septum in the anterior and middle caudals (though in the Patagonian form it is found more developed), and of the barely manifested ischiatic pedicle of the ilium. Other of the characteristics observed by Powell in Saltasaurus loricatus that are seen accentuated in Rocasaurus muniozi are the dorsoventral compression of of the caudal bodies and the higher grade of cavernousness. The morphology of the ischium of Rocasaurus muniozi also is different from the other saltasaurines, since the sheet is notably more extensive than in Saltasaurus loricatus and Neuquensaurus australis.
The record of saltasaurine sauropods is found confined to two areas of Argentina. In the northwest (province of Salta), Saltasaurus loricatus (Lecho Formation) is present and in the north of Patagonia (provinces of Neuquén and Río Negro), Neuquensaurus australis (Rio Colorado Formation) and Rocasaurus muniozi (Allen Formation). In this last region, the saltasaurines are found associated to other titanosaurids, although in no case has more than one species of [saltasaurine] been registered in the same stratigraphic level. The absence of [saltasaurines] in south-central Patagonia is outstanding. In effect, to date saltasaurines have not been registered to the south of the North-Patagonian Massif, in spite that the sediments of the Upper Cretaceous are found well represented in southern Patagonia (Malumián et al., 1983).
The fact that the [saltasaurine] sauropods have been registered uniquely in Argentina, seems to indicate that, probably, they had their origin after the fragmentation of Gondwana, and the opening of the South Atlantic, an event occurring possibly in the middle of the Cretaceous (Pimentel-Mizusaki et al., 1996). Though the available evidence is still fragmentary, it is possible to note that the diversity of the Patagonian titanosaurids increases toward the Late Cretaceous. In particular, the saltasaurines experienced a late diversification, with, at least, three different species.
Source: Polyglot Paleontologist
Salgado & Azpilicueta, 2000
Time
Cretaceous Late Campanian Maastrichtian
Classification
Saurischia Sauropodomorpha Sauropoda Titanosauria
Diet
Herbivore
Fossilsite
Allen Formation, Provincia de Neuquen, Argentina
Length
8 meter
Info
Genus - Typespecies - Skull
Named after Roca city, nearly to the locality (south of Roca City) where it was found 90 kilometers south-east of the capital Neuquin.
Salgado, L. and C. Azpilicueta. 2000. Un nuevo saltasaurino (Sauropoda, Titanosauridae) de la provincia de Río Negro (Formacíon Allen, Cretácico Superior), Patagonia, Argentina. Ameghiniana 37 (3):259-264.
[A new saltasaurine (Sauropoda: Titanosauridae) from the province of Río Negro (Allen Formation, Upper Cretaceous), Patagonia, Argentina]
Translated by Matthew C. Lamanna, January 2001
Original English abstract[/b]
A new saltasaurine taxon based on a femur, pelvic bones and dorsal and caudal vertebrae is described. The closest relationships of the new taxon are with Saltasaurus loricatus Bonaparte and Powell from northwestern Argentina. These species share caudal vertebrae bearing a ventral depression divided by a longitudinal septum. The record of [Saltasaurinae] is thus limited to the Upper Cretaceous of Argentina, with three distinct taxa: Saltasaurus loricatus, Neuquensaurus australis Lydekker and Rocasaurus muniozi n. gen., n. sp.
Introduction
The [Saltasaurinae] (Powell, 1986, 1992) are a group of titanosaurids of modest size (7-8 meters in length), characterized by two synapomorphies, the centra of the caudal vertebrae low and the anterior border of the neural spine located posteriorly with respect to the anterior margin of the postzygapophyses in the middle caudals (Salgado et al., 1997). Powell (1986) recognized two species of saltasaurines, both from the Upper Cretaceous: Saltasaurus loricatus Bonaparte and Powell 1979, originating from the locality of El Brete, province of Salta, and Neuquensaurus australis Lydekker, recorded in the localities of Cinco Saltos and Neuquén, in the provinces of Río Negro and Neuquén (Powell, 1986). The characters that diagnose each one of them were enumerated by Powell (1986). The validity of the third species of [Saltasaurinae], [Neuquensaurus robustus] Lydekker 1893, was put in doubt by this author (Powell, 1986), who minimized the differences with Neuquensaurus australis indicated by Huene (1929) in his monograph on the dinosaurs of Argentina.
In Patagonia, the remains of [saltasaurines] are found associated to those of other dinosaurs, including other titanosaurids. In the case of the locality of Cinco Saltos (province of Río Negro), where a great number of materials have been collected, Neuquensaurus australis is recorded with two other titanosaurids: [Titanosaurus araukanicus] Huene, 1929 and Pellegrinisaurus powelli Salgado, 1996 (Powell, 1986; Salgado, 1996).
In this work we present materials corresponding to a new genus and species of [Saltasaurinae] and discuss its phylogenetic relationships. The same originate from the locality of Salitral Moreno, situated in the interior of the province of Río Negro that until the present has offered an important number and variety of remains of dinosaurs, the titanosaurid Aeolosaurus sp. (Salgado and Coria , 1993), Nodosauridae indet. (Salgado and Coria, 1997), Lambeosaurinae indet. (Powell, 1987), Theropoda indet., [Chelonia] indet., and eggs attributable to [Titanosauridae] Titanosauria (Powell, 1986).
Abbreviations used: MPCA-Pv: Collection of Paleovertebrates of the Provincial Museum of Cipoletti “Carlos Ameghino”.
Systematics and description
Order Saurischia Seeley, 1888
Suborder Sauropodomorpha Huene, 1932
Infraorder Sauropoda Marsh 1878
Family [Titanosauridae] Titanosauria Lydekker, 1893
Subfamily [Saltasaurinae] Powell, 1992
Rocasaurus n. gen.
Type species
Rocasaurus muniozi n. sp.
Etymology
“Roca”, for the rionegrine city of General Roca, nearby the locality of Salitral Moreno; \\\\\\\"saurus” (Greek), lizard.
Diagnosis
The same of the type species by monotypy.
Rocasaurus muniozi n. sp.
Holotype
MPCA-Pv 46 (figures 2-6): a juvenile individual represented by a cervical centrum, a cervical neural arch, two dorsal centra, three dorsal neural arches, two sacral neural arches, a middle caudal vertebra, a middle-posterior caudal vertebra, two ischia, a left pubis, a left ilium, a fragment of the right ilium and a left femur.
Referred material
Three anterior caudal bodies (MPCA-Pv 47, 48, and 60), a middle caudal body (MPCA-Pv 49), a posterior caudal body (MPCA-Pv 50) and six distal caudal bodies (MPCA-Pv 51-56). Cf. Rocasaurus sp. (figures 8.a-c): an anterior caudal (MPCA-Pv 57), a middle caudal (MPCA-Pv 58), a posterior caudal (MPCA-Pv 59).
Geographic provenance
Salitral Moreno, some 25 km to the south of the city of General Roca, province of Río Negro, Argentina
Stratigraphic provenance
Allen Formation, lower member (Powell, 1986). According to Powell (1986), the bearing levels are composed of yellowish medium to gross sandstones, sometimes adopting a gray greenish color, poorly sorted. The sequence evidences a fluvial paleoenvironment.
Age
Early Maastrichtian (Ballent, 1980) or Campanian-Maastrichtian (Uliana and Delapé, 1981).
Etymology
The species is dedicated to Sr. Juan Carlos Muñoz, attendant of the Area Paleontología of the Museo “Carlos Ameghino” of the city of Cipoletti, for his permanent support of the paleontological investigations in the region.
Diagnosis
[Saltasaurine] characterized by the presence of a distal expansion on the lateral margin of the pubis, ischium with an extensive lamina, caudal vertebrae with a deep ventral cavity divided by a longitudinal partition and with the posterior articulation notably depressed and extended ventrally forward.
Description
Cervical vertebrae
There is preserved a neural arch and a vertebral centrum that pertain to the holotype. The neural arch is presented deformed, in a manner that is not possible to find substantial differences with the pieces corresponding to other titanosaurids. In the body, notably compressed, due to post-mortem deformation, there is observed the parapophysis that projects laterally.
Dorsal vertebrae
There are recovered two strongly opisthocoelous dorsal centra, with a small pleurocoel in the form of an eye, a synapomorphic character of the Titanosauria (Bonaparte and Coria, 1993; Salgado et al., 1997). Three neural arches, one perhaps pertaining to a middle dorsal, and the other two to posterior dorsals present the diapophysis projected up, united to the parapophysis by means of diapo-parapophyseal laminae, and a prespinal lamina. The neural spine is wide and anteroposteriorly compressed in difference of Saltasaurus loricatus.
In the neural arch interpreted here as pertaining to a middle dorsal, it is not observed the inferior bifurcation of the infradiapophyseal lamina, that was proposed as a synapomorphy of the titanosaurids by Salgado et al. (1997), although it is clearly present in one of the posterior dorsals. In this last, that is found compressed laterally by crushing, also is observed a series of small laminae that connect the parapophysis with the infradiapophyseal lamina, at different heights. The more developed is interpreted here as the centro-parapophyseal lamina, a structure synapomorphic of the titanosaurids (Salgado et al., 1997).
In posterior view, two robust suprapostzygapophyseal laminae are observed, that connect the postzygapophysis with the neural spine and two infrapostzygapophyseal laminae. The diapo-postzygapophyseal lamina apparently has not been preserved completely for which it is not possible to determine its grade of development. In none of the cases is observed a hyposphene, to the same as the rest of the titanosaurids (Powell, 1986; Salgado et al., 1997).
Caudal vertebrae
All of the caudals are strongly procoelous and present a deep ventral cavity divided by a longitudinal partition, that constitutes one of the distinctive characteristics of this new species. The anterior caudals possess a short and wide body, of lateral faces dorsoventrally convex. Internally they possess a spongy structure composed by cells, equal to Saltasaurus. In the middle and posterior caudals, the posterior articulation of the vertebral centrum is extended ventrally forward, in a manner that, in lateral view, the concave inferior margin is notably short. The prezygapophyses are relatively short and the neural spine is reduced and inclined toward the rear, as in other [saltasaurines].
The posterior caudals attributed to Rocasaurus muniozi n. sp. are very dorsoventrally compressed, and they possess a smooth ventral depression, for it is understood that the strong cavity that is observed ventrally in the anterior and middle caudals, is less deep behind.
With relation to the vertebrae referred tentatively as Rocasaurus sp. (MPCA-PV 57 and 58, figure 8.a-c), is observed a characteristic ventral depression, divided by a longitudinal partition, and the great development of cavernous tissue. However, the neural arch is found here more displaced anteriorly and the posterior articulation does not present its ventral surface extended forward, for which perhaps it should be treated as a distinct species.
Ilium
The ilium posesses an amplified preacetabular lobe, of semicircular contour, characteristic of the Titanosauriformes (Salgado et al., 1997). It is twisted barely outside, a difference of that occurring in other titanosaurids, although it is possible that this owes itself to post-mortem deformation. In comparison with the ilium of Saltasaurus, it is noted that the postacetabular process is more large, the preacetabular lamina is more high and the pubic pedicel is slightly more elongated. Equal to the genus from northwest Argentina, the articulation with the ischium is barely insinuated, in contrast of that occurring in Neuquensaurus and other titanosaurids.
Pubis
The description corresponds to the left pubis. It is a sheetlike bone, possessing a dorso-lateral extension in the distal extreme that is not observed in other titanosaurids examined. The lamina is wide in the proximal portion, before the acetabular surface. The pubic foramen is closed and located in the upper half of the portion that articulates with the ischium. Not observed is the ventral longitudinal elevation characteristic of Saltasaurus loricatus (Powell, 1986).
Ischium
The pieces obtained correspond to a complete ischium and to one incomplete. It is a bone, short and laminar, in which the posterior process constitutes more than half of the length of the piece. The lamina of the ischium is extensive, in greater measure than that in Saltasaurus and Neuquensaurus . The length of the posterior process in relation with that of the iliac pedicel is higher than in Saltasaurus. The contact with the pubis is extensive, as in other camarasauromorphs (Salgado et al., 1997).
Femur
It is a straight bone, anteroposteriorly compressed. On the lateral margin, underneath the greater trochanter, is observed a strong bulge, a character that constitutes a synapomorphy of the titanosauriformes (Salgado et al., 1997; Wilson and Sereno, 1998). The minimum width of the diaphysis is found in the distal half of the bone, lower than in Saltasaurus and Neuquensaurus.
Discussion and conclusions
The characters that are observed in the materials that we have presented, indicate that Rocasaurus muniozi is more closely related with the species from northwest Argentina Saltasaurus loricatus. This would be supported by the presence of a ventral cavity divided by a longitudinal partition or septum in the anterior and middle caudals (though in the Patagonian form it is found more developed), and of the barely manifested ischiatic pedicle of the ilium. Other of the characteristics observed by Powell in Saltasaurus loricatus that are seen accentuated in Rocasaurus muniozi are the dorsoventral compression of of the caudal bodies and the higher grade of cavernousness. The morphology of the ischium of Rocasaurus muniozi also is different from the other saltasaurines, since the sheet is notably more extensive than in Saltasaurus loricatus and Neuquensaurus australis.
The record of saltasaurine sauropods is found confined to two areas of Argentina. In the northwest (province of Salta), Saltasaurus loricatus (Lecho Formation) is present and in the north of Patagonia (provinces of Neuquén and Río Negro), Neuquensaurus australis (Rio Colorado Formation) and Rocasaurus muniozi (Allen Formation). In this last region, the saltasaurines are found associated to other titanosaurids, although in no case has more than one species of [saltasaurine] been registered in the same stratigraphic level. The absence of [saltasaurines] in south-central Patagonia is outstanding. In effect, to date saltasaurines have not been registered to the south of the North-Patagonian Massif, in spite that the sediments of the Upper Cretaceous are found well represented in southern Patagonia (Malumián et al., 1983).
The fact that the [saltasaurine] sauropods have been registered uniquely in Argentina, seems to indicate that, probably, they had their origin after the fragmentation of Gondwana, and the opening of the South Atlantic, an event occurring possibly in the middle of the Cretaceous (Pimentel-Mizusaki et al., 1996). Though the available evidence is still fragmentary, it is possible to note that the diversity of the Patagonian titanosaurids increases toward the Late Cretaceous. In particular, the saltasaurines experienced a late diversification, with, at least, three different species.
Source: Polyglot Paleontologist