Sauropod Phylogeny



Allain, R., P. Taquet, B. Battail, J. Dejax, P. Richir, M. Véran, F. Limon-Duparcmeur, R. Vacant, O. Mateus, P. Sayarath, B. Khenthavong, and S. Phouyavong.  1999.  Un nouveau genere de dinosaure sauropode de la formation des Grés supérieurs (Aptien-Albien) du Laos.  Comptes Rendus de l'Academie des Sciences Paris, Sciences de la Terre et des Planétes 329:609-616.

Bonaparte, J. F.  1986a.  The early radiation and phylogenetic relationships of sauropod dinosaurs, based on vertebral anatomy; pp. 247-258 in K. Padian (eds.), The Beginning of the Age of Dinosaurs.  Cambridge University Press, Cambridge.

_____.  1986b.  Les dinosaures (Carnosaures, Allosauridés, Sauropodes, Cétiosaurides) du Jurassique moyen de Cerro Cóndor (Chubut, Argentine).  Annales de Paléontologie 72:325-386.

Borsuk-Bialynicka, M.  1977.  A new camarasaurid sauropod Opisthocoelicaudia skarzynskii, gen. n., sp. n. from the Upper Cretaceous of Mongolia.  Palaeontologica Polonica 37:1-64.

Buffetaut, E., V. Suteethorn, G. Cuny, H. Tong, J. LeLoeuff, S. Khansubha, and S. Jongautchariyakul.  2000.  The earliest known sauropod dinosaur.  Nature 407:72-74.

Calvo, J. O.  1994.  Jaw mechanics in sauropod dinosaurs.  GAIA 10:183-193.

_____ and L. Salgado.  1995.  Rebbachisaurus tessonei, sp. nov. A new Sauropoda from the Albian-Cenomanian of Argentina; new evidence on the origin of Diplodocidae.  GAIA 11:13-33.

Curry, K. A.  2001.  The evolutionary history of the Titanosauria.  Ph. D., State University of New York, Stony Brook.

Curry Rogers, K. A. and C. Forster.  2001.  The last of the dinosaur titans: a new sauropod from Madagascar.  Nature 412: 530-534.

Curry Rogers, K. A. and C. Forster.  2004.  The skull of Rapetosaurus krausei (Sauropoda: Titanosauria) from the Late Cretaceous of Madagascar.  Journal of Vertebrate Paleontology 24:121-144.

Galton, P. M. and J. van Heerden.  1985.  Partial hindlimb of Blikanasaurus cromptoni n. gen. and n. sp., representing a new family of prosauropod dinosaurs from the Upper Triassic of South Africa.  Géobios 18:509-516.

González Riga, B. J.  2003.  A new titanosaur (Dinosauria, Sauropoda) from the Upper Cretaceous of Mendoza Province, Argentina.  Ameghiniana 40:155-172.

He, X.-L., K. Li, and K.-J. Cai.  1988.  [The Middle Jurassic dinosaur fauna from Dashanpu, Zigong, Sichuan. Vol. IV. Sauropod Dinosaurs (2) Omeisaurus tianfuensis].  Sichuan Scientific and Technological Publishing House, Chengdu, 143 pp.

_____, C. Wang, S. Liu, F. Zhou, T. Liu, K. Cai, and B. Dai.  1998.  [A new sauropod dinosaur from the Early Jurassic in Gongxian County, South Sichuan].  Acta Geologica Sichuan 18:1-6.

Huene, F.  1932.  Die fossil Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte.  Monographen zur Geologie und Palaeontologie 4:1-361.

Jacobs, L. L., D. A. Winkler, W. R. Downs, and E. M. Gomani.  1993.  New material of an Early Cretaceous titanosaurid sauropod dinosaur from Malawi.  Palaeontology 36:523-534.

Jain, S. L. and S. Bandyopadhyay.  1997.  New titanosaurid (Dinosauria: Sauropoda) from the Late Cretaceous of central India.  Journal of Vertebrate Paleontology 17:114-136.

Janensch, W.  1929a.  Material und Formengehalt der Sauropoden in der Ausbeute der Tendaguru Expedition.  Palaeontographica (Supplement 7) 2:1-34.

Le Loeuff, J.  1995.  Ampelosaurus atacis (nov. gen., nov. sp.), un nouveau Titanosauridae (Dinosauria, Sauropoda) du Crétacé supérieur de la Haute Vallée de l'Aude (France).  Comptes Rendus de l'Academie des Sciences Paris (série II) 321:693-699.

Marsh, O. C.  1878.  Principal characters of American Jurassic dinosaurs.  Pt. I.  American Journal of Science (series 3) 16:411-416.

Martin, V., E. Buffetaut, and V. Suteethorn.  1994.  A new genus of sauropod dinosaur from the Sao Khua Formation (Late Jurassic or Early Cretaceous) of northeastern Thailand.  Comptes Rendus de l'Academie des Sciences Paris (série II) 319:1085-1092.

Martínez, R., O. Giménez, J. Rodríguez, M. Luna, M. C. Lamanna.  2004.  An articulated specimen of the basal titanosaurian (Dinosauria: Sauropoda) Epachthosaurus sciuttoi from the early Late Cretaceous Bajo Barreal Formation of Chubut Province, Argentina.  Journal of Vertebrate Paleontology 24:107-120.

McIntosh, J. S.  1990.  Sauropoda; pp. 345-401 in D. B. Weishampel, P. Dodson, and H. Osmólska (eds.), The Dinosauria.  University of California Press, Berkeley.

_____, C. A. Miles, K. C. Cloward, and J. R. Parker.  1996.  A new nearly complete skeleton of Camarasaurus.  Bulletin of the Gunma Museum of Natural History 1:1-87.

Nowinski, A.  1971.  Nemegtosaurus mongoliensis n. gen., n. sp., (Sauropoda) from the uppermost Cretaceous of Mongolia.  Palaeontologica Polonica 25:57-81.

Ostrom, J. H.  1969.  Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana.  Bulletin of the Yale Peabody Museum of Natural History 30:1-165.

Powell, J. E.  1992.  Osteología de Saltasaurus loricatus (Sauropoda-Titanosauridae) del Cretácico Superior del Noroeaste argentino; pp. 165-230 in J. L. .Sanz, and A. D. Buscalioni (eds.), Los Dinosaurios y su Entorno Biotico.  Instituto "Juan de Valdes", Cuenca.

Raath, M.  1972.  Fossil vertebrate studies in Rhodesia: a new dinosaur (Reptilia, Saurischia) from the near the Trias-Jurassic boundary.  Arnoldia 30:1-37.

Romer, A. S.  1968.  Notes and Comments on Vertebrate Paleontology.  University of Chicago Press, Chicago, 304 pp.

Salgado, L., R. A. Coria, and J. O. Calvo.  1997.  Evolution of titanosaurid sauropods. I: phylogenetic analysis based on the postcranial evidence.  Ameghiniana 34:3-32.

Sanz, J. L., J. E. Powell, J. Le Loeuff, R. Martínez, and X. Pereda-Suberbiola.  1999.  Sauropod remains from the Upper Cretaceous of Laño (northcentral Spain). Titanosaur phylogenetic relationships.  Estudios del Museo de Ciencias Naturales de Álava 14:235-255.

Sereno, P. C., A. L. Beck, D. B. Dutheil, H. C. E. Larsson, G. H. Lyon, B. Moussa, R. W. Sadleir, C. A. Sidor, D. J. Varricchio, G. P. Wilson, and J. A. Wilson.  1999.  Cretaceous sauropods from the Sahara and the uneven rate of skeletal evolution among dinosaurs.  Science 286:1342-1347.

Smith, J. B., M. C. Lamanna, K. J. Lacovara, P. Dodson, J. R. Smith, J. C. Poole, R. Giengengack, and Y. Attia.  2001.  A giant sauropod dinosaur from an Upper Cretaceous mangrove deposit in Egypt.  Science 292:1704-1706.

Upchurch, P. 1995.  The evolutionary history of sauropod dinosaurs.  Philosophical Transactions of the Royal Society of London B 349:365-390.

_____.  1998. The phylogenetic relationships of sauropod dinosaurs.  Zoological Journal of the Linnean Society 124:43-103.

Upchurch, P., P. M. Barrett, and P. Dodson.  2004.  Sauropoda; pp. 259-322 in D. B. Weishampel, P. Dodson, and H. Osmólska (eds.) The Dinosauria, 2nd Ed.  University of California Press, Berkeley.

Wilson, J. A. 1999.  Vertebral laminae in sauropods and other saurischian dinosaurs.  Journal of Vertebrate Paleontology 19:639-653.

_____.  2002.  Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136: 217-276.

_____. 2005a. Redescription of the Mongolian sauropod Nemegtosaurus mongoliensis Nowinski (Dinosauria: Saurischia) and comments on Late Cretaceous sauropod diversity.  Journal of Systematic Palaeontology 3 (in press).

_____.  2005b. Integrating ichnofossil and body fossil records to estimate locomotor posture and spatiotemporal distribution of early sauropod dinosaurs: a stratocladistic approach.  Paleobiology 31 (in press). 

_____ and M. T. Carrano. 1999. Titanosaurs and the origin of "wide-gauge" trackways: a biomechanical and systematic perspective on sauropod locomotion.  Paleobiology 25:252-267.

_____ and P. C. Sereno. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs.  Society of Vertebrate Paleontology Memoir 5:1-68 (supplement to Journal of Vertebrate Paleontology 18).

Yates, A. M. and J. W. Kitching. 2003. The earliest known sauropod dinosaur and the first steps towards sauropod evolution.  Proceedings of the Royal Society of London B 270: 1753-1758.

Zhang, Y. 1988. The Middle Jurassic dinosaur fauna from Dashanpu, Zigong, Sichuan.  Journal of Chengdu College of Geology 3:1-87.

Sauropoda – a brief history

The pace of discovery of sauropod species is summarized in the histogram above. Prior to the “Dinosaur Renaissance”, which was inaugurated with John Ostrom’s (1969) description of Deinonychus, sauropod discoveries rarely topped more than a handful every five years. A notable outlier, however, is the burst of sauropod discoveries and descriptions in the late 1870s that coincides with peak Cope-Marsh activity. Following 1969, however, sauropod discoveries always exceed five per five years, steadily increasing through the late 1990s when 25 sauropods were named.  The subsequent drop in sauropod discoveries at the far right is an artifact of only counting up to the year 2002.

Returning to Notes and Comments on Vertebrate Paleontology (1968) in this context, 70 out the 121 sauropod species were described after Romer’s famous laments. Early sauropod researchers not only had poorer material (fewer complete skeletons), they had fewer than half the number of species available to current researchers. The pace and nature of discovery of sauropod dinosaurs has certainly colored the way our understanding of their phylogeny unfolded, but the advent of numerical techniques for assessing the proximity of ancestry had an important (though not immediate) impact on sauropod studies. 

Sauropods are the largest animals known to have walked on land. Their stratigraphic range extends from the Late Triassic until the Late Cretaceous, and they are known from all continental landmasses except Antarctica (but we expect they were there too). The group increased in diversity through time, and the most recent survey recognizes 121 valid sauropod species (Upchurch et al. 2004).  My research in sauropod systematics focuses on documenting the history of osteological changes that led to the body plan and its various modifications over the course of 160 million years of evolution. I began my investigations as a graduate student with Paul Sereno at the University of Chicago; at that time there had been few attempts to establish the genealogy of sauropod dinosaurs. An example of the general attitude towards the study of sauropod systematics was given by the famous vertebrate paleontologist A. S. Romer, who bookended his comments on sauropods in Notes and Comments on Vertebrate Paleontology (1968:137-138) with the following laments:  “A proper classification of the great amphibious sauropods has the despair of everyone working on the group”, and “it will be a long time, if ever, before we obtain a valid, comprehensive picture of sauropod classification and phylogeny”. 

Although a “valid” and “comprehensive” sauropod phylogeny was not available during Romer’s time, steps had already been initiated to resolve the relationships of constituent taxa.  Sauropod interrelationships were resolved in stages, beginning with early classifications of O.C. Marsh (1895, 1898), Werner Janensch (1929), and Friederick von Huene (1932). Later José Bonaparte (1986a,b) recognized ”eo” and “neo” sauropods, and Jack McIntosh (1989, 1990a,b) delineated numerous sauropod families. Romer (1968:137-138) suggested that the fragmentary nature of many sauropod taxa contributed to the difficulty in resolving their interrelationships: “The reasons for our difficulties are apparent. Few complete skeletons exist; feet and skulls are rare; many of the numerous described forms are based on fragmentary material”.  This was certainly the case, and the improvement in our understanding of sauropod phylogeny is the result of an improved sauropod fossil record. Recent key discoveries, in stratigraphic order, include the discovery of primitive sauropods in Africa (e.g., Charig et al., 1965; Raath, 1972; Yates and Kitching, 2003; Allain et al., 2004) and India (e.g., Jain et al., 1975; Yadagiri, 2001), Middle Jurassic sauropods from China (Zhang, 1988; He et al., 1988, 1998; Tang et al., 2001; Ouyang and Ye 2002) and Argentina (Bonaparte, 1986b), and well preserved sauropod skeletons from the Cretaceous of Asia (Borsuk-Bialynicka, 1977; Suteethorn et al., 1995), South America (Bonaparte and Salgado, 1992; Calvo and Salgado, 1995; Martínez et al., 2004; González Riga 2003), India (Jain and Bandyopadhyay, 1997), Africa (Jacobs et al., 1993; Sereno et al., 1999), and Madagascar (Curry Rogers and Forster, 2001).

Wilson & Curry Rogers 2005

I began investigating sauropod anatomy in earnest in the summer of 1993, as preparation for field work in Niger with Paul Sereno – where we were sure to find sauropod dinosaurs. Our museum visits in Brigham Young University, University of Utah, and the Museum of the Rockies, along with field work on Jobaria tiguidensis (below right) really opened my eyes to sauropod anatomy and encouraged me to pursue sauropod phylogeny as a thesis topic.

The following Spring and Summer I joined Paul Sereno again in museum research out west. Paul and I developed a core of character data that I was one of the first attempts to resolve sauropod phylogeny, albeit at a coarse scale. We presented our results at the Society of Vertebrate Paleontology meetings that year (abstract) and I continued to build on that dataset during a month-long trip to Argentina in early 1994, where I was able to study key Middle Jurassic and Lower Cretaceous sauropod material. I continued museum research in North America in 1995 and joined Paul for field work in Morocco that summer, where I was excited to  find remains of the enigmatic sauropod  Rebbachisaurus garasbae. That trip was more successful in for theropods than sauropods, but we did collect some interesting sauropod material.

Without a doubt, my most important museum research took place at the Indian Statistical Institute in Calcutta in the Fall of 1996, where I was able to examine the wonderful remains of the Lower Jurassic sauropod Barapasaurus tagorei. This was my first good look at a primitive sauropod, and it really shaped my views on the early differentiation of sauropod dinosaurs. When I returned from that trip, I went into the field in Mendoza, Argentina with Paul Sereno and had the opportunity to collect some beautiful titanosaur material from the Río Colorado Formation.  When I returned I left for Europe and Russia to spent three winter months seeing all the material I could set my eyes on.

Throughout the course of this museum research, Paul and I were chipping away at what eventually became a monographic description of the characters that defined the basic relationships of sauropod dinosaurs. As it turns out, others were working on the same question. The 1990s were a busy decade for sauropod systematics!

Early attempts to classify sauropods had broken the group into narrow-toothed and broad-toothed groups. The broad-crowned sauropods included camarasaurs and brachiosaurs (left, above), and the narrow-toothed sauropods included diplodocids and titanosaurs (left, below). Sauropod experts like Jack McIntosh and had pointed out that many postcranial characteristics went against this dichotomy, but there was no real alternative hypothesis set forward to explain sauropod classification.

The first serious cladistic analysis of sauropods, by Paul Upchurch in 1995, supported the traditional narrow-vs.-broad tooth dichotomy as an evolutionary hypothesis. Jorge Calvo and Leo Salgado published an analysis focused on diplodocid that same year, which introduced new character data. In 1997, Leo Salgado et al. published a broader analysis that suggested that the two narrow-toothed groups were distantly related, and that titanosaurs shared a close relationship with Brachiosaurus.

In 1998, Paul Sereno and I published the monograph we had been working on for so long, which outlined for the first time the early course of sauropod evolution and highlighted the important herbivorous and locomotory changes in the group. Our hypothesis of sauropod interrelationships is shown above. Our character data supported the Salgado et al. Brachiosaurus-Titanosauria grouping to the exclusion of diplodocids, and further suggested that broad teeth are a primitive feature of sauropods, whereas narrow teeth are a derived feature that appeared at least twice independently within the group. In that paper, we explored what the character data implied for the sequence of changes in the evolution of herbivory, neck elongation, and locomotion (below).

Jobaria quarry

Museum and Field Research

Higher-Level Phylogeny of Sauropoda

That same year (1998), Paul Upchurch published the first lower-level treatment of sauropod phylogeny, in which he accepted the independent origin of narrow-toothed clades and the close relationship between Brachiosaurus and Titanosauria. I too was working on a lower-level analysis of sauropod dinosaurs, which I completed for my Ph.D. thesis in 1999. I soon left for the University of Michigan and worked hard to balance a teaching load with modifying, checking, and publishing my my growing core of character data. This was eventually published as a paper in the Zoological Journal of the Linnean Society in 2002.

Lower-Level Phylogeny of Sauropoda

The resultant hypothesis of sauropod relationships is shown above. In many ways it agrees with previous results of other researchers, but there were important topological differences with Upchurch’s topology that I addressed in detail in the paper. Principal among them were differences in: (1) the affinities of the enigmatic Mongolian sauropods Nemegtosaurus and Quaesitosaurus; (2) affinities of the Chinese sauropods Shunosaurus, Omeisaurus, Mamenchisaurus, and Euhelopus, which Upchurch considered a natural group he called “Euhelopodidae”.

In that same paper, I explored how different regions of the skeleton were changing in different sauropod groups through time. I assessed the relative importance of cranial, axial, and appendicular data to the character support for the two most neosauropod  clades, Macronaria and Diplodocoidea.  I sorted characters by anatomical region and tallied the types of synapomorphies that characterize various groups (see table at left). Because of the prevalence of missing data in the analysis, some of the differences in the relative cladewise support of different anatomical regions will be artifactual. However, based on the relative frequencies of missing data in each terminal taxon, these effects are expected to be minimal.

Macronaria and Diplodocoidea are comparably sized sister-taxa that comprise Neosauropoda. These sister-taxa have identical lineage durations that begin with the origin of Neosauropoda in the Middle or Late Jurassic and end at the Cretaceous–Tertiary boundary. During this interval, which lasted less than 100 Myr, 365 synapomorphies and autapomorphies were recovered in my analysis; 149 within Diplodocoidea and 216 within Macronaria. Despite similar amounts of missing data (please refer to table 8 of Wilson 2002), the relationships within Marcronaria and Diplodocoidea are supported by character data from distinct anatomical regions.

In diplodocoids, cranial and axial features constitute 85% of the total support for the topology, whereas appendicular synapomorphies provide only minimal support. Macronarians, in contrast, have much more balanced support. They are characterized by fewer cranial synapomorphies and a surprisingly high proportion of appendicular synapomorphies. Changes in the axial column were common in both lineages.

The discrepancy in support for the two major neosauropod lineages suggests that the divergence and subsequent diversification of each may have been shaped by innovations focused in different regions of the skeleton. Interestingly, Late Cretaceous survivors of each clade represent the morphological extremes in each case – diplodocoids survive in the form of shovel-snouted, slender-necked rebbachisaurids; macronarians persist as stocky, wide-gauged saltasaurines.

I believe that this analysis is a starting point for future work in Sauropoda. The core of character data  has, I think, begun to establish a robust hypothesis of descent for most sauropods, but there are some areas of the topology that are not well supported, such as the position of the neosauropod Haplocanthosaurus.  Future discoveries and re-examination of the relevant materials will certainly help in that effort. There are many other sauropod genera that have not been included in a phylogenetic analysis, and these too need to be examined. I tried to give a best guess as to where many of these fit in (see table below) based on preserved synapomorphies, but these need to be revisited.

from Wilson & Sereno 1998

Brachiosaurus brancai

Diplodocus longus

Wilson & Sereno 1998

Wilson & Sereno 1998

Wilson 2002

Wilson 2002

Wilson 2002

In discussing the history of sauropod studies, I have thus far focused on those that addressed a broad array of sauropod dinosaurs. Other analyses have focused on smaller subgroups of sauropods, predominantly within Titanosauria. These include analyses by Sanz et al. (1999), Curry (2001), Curry Rogers and Forster (2001), Calvo and González Riga (2003), González Riga (2003), Upchurch et al. (2004), and Curry Rogers (2005).

I am currently working on a collaborative project with Kristi Curry Rogers to investigate the interrelationships of Titanosauria.  More information can be found on this page.

Analyses of Sauropod Subgroups