The sauropod clade Titanosauria is one of the most diverse and interesting dinosaur groups. Their fossils show an amazing size range, and some of them, were the largest animals ever to walk the Earth. Titanosaurs like Argentinosaurus, Futalognkosaurus, and Puertasaurus surpassed lengths of 30 m and masses of 70 tons.
Titanosaurs exhibit a worldwide distribution useful for paleobiogeographic studies. They were important terrestrial herbivores during the Jurassic and specially the Cretaceous periods, and their remains have been recovered from all continents except Antarctica. Moreover, their fossil record is important for studying the composition of dinosaur faunas near the mass extinction at the K-T boundary.
Another interesting aspect of titanosaurs is their extraordinary diversity, similar to that of the Late Cretaceous North American hadrosaurids. At the time of this writing, more than 48 titanosaur species have been discovered, around one third of all known sauropods. In this context, phylogenetic studies of titanosaurs are important as a basis for further evolutionary and paleobiogeographic interpretations. Likewise, locomotion and growth strategies are topics of great interest.
Unfortunately, these research topics have been limited by the fossil record, since most titanosaur species, like other sauropods, are represented by incomplete and mostly disarticulated skeletal elements, such as dorsal and caudal vertebrae, and appendicular bones. However, this situation is changing with the discovery of well preserved specimens, such as the titanosaur Rapetosaurus collected in Madagascar (Curry Rogers and Forster, 2001). Recently, several new genera, such as Gobititan (You et al. 2003) and Sonidosaurus (Xu et al., 2006), were discovered in Asia. In Europe, the titanosaurs Aragosaurus (Sanz et al., 1987; Canudo et al., 2001) and Lirainosaurus (Sanz et al., 1999) and the basal somphospondilyan Tastavinsaurus (Canudo et al., 2008) were described.
Likewise, during the last decade, 18 new titanosaur genera were discovered in South America; in Argentina and Brazil the record now reaches 30 genera (see Table 1).
Moreover, in Patagonia, extraordinary embryos and eggs (Chiappe et al., 1998, 2001; Salgado et al., 2005a) and exceptionally articulated specimens (Martínez et al., 2004; Calvo et al., 2007a; González Riga et al., 2008) were found.These discoveries show the importance of the South American record for understanding both the phylogeny and paleobiology (ontogenetic stages, behavior and locomotion) of titanosaurs.
Table 1. South American titanosaur species.
1. Adamantisaurus mezzalirai Santucci and Bertini 2006 / Adamantina Formation/ Brazil/ Campanian-?Maastrichtian
2. Aeolosaurus rionegrinus Powell, 1987b /Angostura Colorada Formation/ Argentina/late Campanian-Maastrichtian
3. Aeolosaurus colhuehapensis Casal, Martínez, Luna, Sciutto and Lamanna 2007 / Bajo Barreal Formation/ Argentina /late Cenomanian-early Turonian
4. Agustinia ligabuei Bonaparte 1999 /Lohan Cura Formation / Argentina / late Apitan-Albian
5. Amargatitanis macni Apesteguía 2007 / La Amarga Formation/ Argentina / Barremian-early Aptian
6. Andesaurus delgadoi Calvo and Bonaparte 1991 / Candeleros Formation /Argentina/ early Cenomanian
7. Antarctosaurus wichmanianus Huene 1929 / ?Anacleto Formation / Argentina / early Campanian
8. Argentinosaurus huinculensis Bonaparte and Coria 1993 / Huincul Formation / Argentina / late Cenomanian
9. Argyrosaurus superbus Lydekker 1893 / Bajo Barreal Formation / Argentina / late Cenomanian-early Turonian
10. Baurutitan britoi Kellner, Campos and Trotta 2005 / Marília Formation / Brazil / Maastrichtian
11. Barrosasaurus casamiquelai Salgado y Coria 2009 / Anacleto Formation / Argentina / early Campanian
12. Bonatitan reigi Martinelli and Forasiepi 2004 / Allen Formation / Argentina / late Campanian-early Maastrichtian
13. Bonitasaura salgadoi Apesteguía 2004 / Bajo de la Carpa Formation /Argentina /Santonian
14. Chubutisaurus insignis Del Corro 1975 / Cerro Barcino Formation / Argentina / Aptian-Albian
15. Epachthosaurus sciuttoi Powell, 1990 /Bajo Barreal Formation /Argentina /late Cenomanian-early Turonian
16. Futalonkosaurus dukei Calvo, Porfiri, González Riga and Kellner 2007 / Portezuelo Formation / Argentina / late Turonian-early Coniacian
17. Gondwanatitan faustoi Kellner and Azevedo 1999 / Bauru Group /Brazil / Santonian-Maastrichthian
18. Laplatasaurus araukanicus Huene 1929 /?Anacleto Formation /Argentina / early Campanian
19. Ligabuesaurus leanzai Bonaparte, González Riga, and Apesteguía 2006 / Lohan Cura Formation / Argentina / late Aptian-Albian
20. Malarguesaurus florenciae González Riga, Previtera, and Pirrone 2009 / Portezuelo Formation / Argentina / late Turonian-early Coniacian
21. Maxakalisaurus topai Kellner, Campos, Azevedo, Trotta, Henriques, Craik, and Silva 2006 /Adamantina Formation / Brazil / Campanian-?Maastrichtian
22. Mendozasaurus neguyelap González Riga 2003 / Río Neuquén Subgroup (Portezuelo-Plottier formations) /Argentina / late Turonian- Coniacian
23. Muyelensaurus pecheni Calvo, González Riga and Porfiri, 2007 /Portezuelo Formation Argentina /late Turonian-early Coniacian
24. Neuquensaurus australis (Lydekker, 1893) Powell, 1986 / ?Anacleto Formation /Argentina /early Campanian
25. Pellegrinisaurus powelli Salgado 1996 / ?Anacleto Formation / Argentina /early Campanian
26. Pitekunsaurus macayai Filippi and Garrido 2008 / Anacleto Formation / Argentina / early Campanian
27. Puertasaurus reuili Novas, Salgado, Calvo, and Agnolin 2005 / Pari Aike Formation / Argentina / early Maastrichtian
28. Rinconsaurus caudamirus Calvo and González Riga 2003 / Río Neuquén Subgroup (Portezuelo-Plottier formations) / Argentina / late Turonian-Coniacian
29. Rocasaurus muniozi Salgado and Azpilicueta 2000 / Allen Formation / Argentina / late Campanian-early Maastrichtian
30. Saltasaurus loricatus Bonaparte and Powell 1980 / Lecho Formation / Argentina / Campanian-Maastrichtian
31. Trigonosaurus pricei Campos, Kellner, Bertini, and Santucci 2005 / Marília Formation
Brazil / Maastrichtian
32. Uberabatitan ribeiroi Salgado and Souza Carvalho 2008 / Marília Formation / Brazil /Maastrichtian