Your Friends The Titanosaurs, part 22: Paludititan, Panamericansaurus, and Paralititan

The inexorable march of the titanosaurs continues, bringing us to the letter "P" (which for whatever reason is a popular letter for starting off titanosaur names, like "A" and "M"). For variety, we have a small species from Europe (Paludititan nalatzensis), a small species from South America (Panamericansaurus schroederi), and a large species from Africa (Paralititan stromeri). If you're looking ahead, the next couple of anticipated posts are heavy on South American species, and include two of the largest known titanosaurs (Patagotitan mayorum and Puertasaurus reuili).

Paludititan nalatzensis

We already covered some of this ground back in September 2019 with Magyarosaurus, so let's just briefly set the scene: Transylvanian titanosaur material has historically been either disassociated bones, or any original association has been lost due to vague or nonexistent collection information. Paludititan nalatzensis represents the first well-documented associated titanosaur specimen from this region, and so has the potential to help clarify the relationships of the other titanosaurs (should they wish to cooperate).

P. nalatzensis is based on a partial skeleton discovered and excavated from Nălaţ-Vad near Haţeg, Romania, by a joint Romanian–Belgian crew in 2002. The horizon is a dark paleosol ("fossil soil") mudstone within the Sânpetru Formation. The bed is interpreted as a water-logged terrestrial setting, which inspired the genus name: "paludos" is Ancient Greek for marshy. The species name is a reference to Nălaţ-Vad, so together we get something like "marsh titan from Nălaţ-Vad". The type specimen is UBB NVM1 (Babes-Bolyai University, Cluj-Napoca, Romania), which was found as an associated accumulation of bones from the core of the body. All told, the specimen included: three dorsal vertebrae; 12 largely complete caudals and fragments of other caudals from various parts of the tail; ribs and rib fragments; 12 incomplete chevrons; a partial right pelvis (much of the ilium missing, but the ischium and pubis mostly intact); a left ischium; a fragment of the right femur; two ungual phalanges; and unidentified or incompletely prepared fragments. It is possible that other bones were present, but have been lost to modern erosion. The only non-titanosaur bone found with UBB NVM1 was a theropod tooth, suggesting that some scavenging occurred (Csiki et al. 2010).

We don't have a complete limb bone, so I can't provide you a humerus or femur measurement for comparison, but the figure below shows that P. nalatzensis was larger than Magyarosaurus dacus, not that this feat is difficult for sauropods to achieve. Among other features, the shaft of the pubis is long and gracile (which looks very disproportionate versus the diminutive ischium, but the two were found in articulation with each other and the ilium), and the tail shows a tendency toward "Rinconsaurus Syndrome", incorporating procoelous, amphiplatyan (flat articulations at both ends of the centrum), and platycoelous (anterior flat, posterior concave) articulations in the middle tail (Csiki et al. 2010).

A clip from Figure 12 of Csiki-Sava et al. (2015), showing posterior dorsal vertebrae of Magyarosaurus dacus (D, left) and Paludititan nalatzensis (E, right). One rather notable difference is that the P. nalatzensis vertebra is quite a bit larger than either of the two M. dacus vertebrae (the scale bar for D is 5 cm and the scale bar for E is 10 cm). These are right lateral views, so the head of the dinosaur was off to the right. CC-BY-4.0.

Csiki et al. (2010) were faced with the question of whether to describe UBB NVM1 as its own taxon or as a specimen of Magyarosaurus. They opted to go with the first option because of the issues surrounding Magyarosaurus and the uncertain correlation and titanosaur diversity of the Sânpetru Formation (yielding P. nalatzensis) and the Densuş-Ciula Formation (yielding the lectotype of Magyarosaurus dacus). The choice by Csiki et al. (2010) to describe P. nalatzensis as separate from Magyarosaurus appears to be independently justified, as documented by Mannion et al. (2019) in an abstract (actually two abstracts, one for the SVP meeting and one for EAVP, but I've chosen to cite the SVP version). They found that P. nalatzensis can be distinguished from Magyarosaurus dacus and does not turn up with "M." hungaricus in their phylogenetic analysis (the two cannot be compared directly because their material does not overlap). Just for good measure, Mannion et al. (2019) also reported the presence of a fourth undescribed taxon, one with a large body. (In the Jurassic and Early Cretaceous, formations would have multiple sauropod species, but they'd represent several different clades: diplodocids, dicraeosaurids, camarasaurs, brachiosaurids, etc. In the Late Cretaceous, you'd still get several species, but they'd all be titanosaurs, which says something both about the extent of the titanosaur radiation and our ability to parse them into different clades.)

Csiki et al. (2010) ran P. nalatzensis through several existing data sets, and it obligingly bounced around Titanosauria (with some fondness for Epachthosaurus). More recently, the data set shared and modified by Gorscak et al. (2017), Sallam et al. (2018), and Gorscak and O'Connor (2019) usually finds it as a derived titanosaur in the company of Ampelosaurus atacis, Mansourasaurus shahinae, or both, while Díez Díaz et al. (2018) found it to clade with Lohuecotitan pandafilandi near the base of Titanosauria.

Panamericansaurus schroederi

I was initially excited when the name Panamericansaurus was announced that this might mean it was known from both North and South America. This was not the case. Instead, this titanosaur is named for the Pan American Energy company in recognition of its support of Proyecto Dino (Calvo and Porfiri 2010). The species name honors the Schroeder family of Neuquén, on whose land the specimen was found, giving us something like "the Schroeder family's Pan American Energy lizard." P. schroederi is based on MUCPv-417 (Museo de la Universidad del Comahue, Paleontología de Vertebrados), which is composed of five caudals, a sacral, the left humerus, a couple of chevrons, and rib fragments. This specimen was found on the Bodega Familia Schroeder near San Patricio del Chañar (Calvo and Porfiri 2010), making this the second titanosaur to be associated with wine (after Ampelosaurus atacis). Titanosaurs and wine just seem to go together, I guess. Stratigraphically, it was found in the Allen Formation (Calvo and Porfiri 2010), which has also produced Bonatitan reigi and the saltasaur Rocasaurus muniozi (and potentially a bunch more; Garcia and Salgado 2003). (A joke along the lines of "an aeolosaur, a saltasaur, and a lognkosaur walk into a bar" was all the rage in 70 Ma Patagonia, but you had to have been there.)

The caudals do not make a series, but do have characteristic aeolosaur features of the neural arch. The humerus is 123 cm long (48.4 in) and has a strong deltopectoral crest but is otherwise gracile. Among aeolosaurs, it appears to be more similar to that of Gondwanatitan faustoi than Aeolosaurus rionegrinus. By comparison with G. faustoi, the type individual of P. schroederi was estimated by Calvo and Porfiri (2010) as approximately 11 m long (36 ft). As you might have guessed from the constant mentions of aeolosaurs, Calvo and Porfiri (2010) described P. schroederi as an aeolosaur, and it has so far not disappointed in phylogenetic analyses (e.g., Santucci and de Arruda-Campos 2011; França et al. 2016; Gorscak et al. 2017; Sallam et al. 2018; Gorscak and O'Connor 2019). Otherwise, it has mostly kept its nose out of the literature following its original description.

Paralititan stromeri

It's not entirely obvious why some giant sauropods prosper in the public mind and others fade. Argentinosaurus huinculensis, of course, has priority as the champion. Dreadnoughtus schrani and Patagotitan mayorum have the best press, plus some of the best material. Futalognkosaurus dukei is a cult alternative (albeit still incompletely described). Then we get to Notocolossus gonzalezparejasi and the current entrant, Paralititan stromeri, which like the proverbial comet burst onto the scene but then departed. We could blame it on incompleteness, but that doesn't take into account Puertasaurus reuili, which is known from even more incomplete remains but looms larger (figuratively speaking) in dinosaur enthusiast circles than Notocolossus or Paralititan. Maybe N. gonzalezparejasi and P. stromeri are on the wrong side of a lower threshold where there has to be enough bones to speculate but not enough to narrow things down.

Paralititan stromeri was described in Smith et al. (2001), during what could be called the Titanosaur Renaissance or something similarly portentous (pretentious, same diff), denoting a time frame of about 10–15 years beginning in the 1990s when paleontologists first began to seriously grapple with the group. Highlights include the transfer of Nemegtosaurus and Opisthocoelicaudia to Titanosauria, Argentinosaurus (1993), Malawisaurus (1993 for the genus), Ampelosaurus (1995), the announcement of the Auca Mahuevo egg site (1998), Lirainosaurus (1999), Paralititan (2001), Rapetosaurus (2001), Isisaurus and the revision of Titanosaurus (2003), Bonitasaura (2004) to emphasize that we really didn't know much at all, and a major phylogenetic analysis (Curry Rogers 2005) to cap it off.

P. stromeri was uncovered in Egypt, in the Bahariya Formation of the Bahariya Oasis, which as you may recall is also where the smaller Aegyptosaurus baharijensis came from. The type specimen of P. stromeri was found in sediments deposited in a tidal setting. Brown tidal-flat shale beds loaded with plant fossils, especially of the mangrove fern Weichselia, alternate with tidal channel beds. Smith et al. (2001) regarded the association of groups of bones as evidence that there was little transportation, instead suggesting that the type individual had expired at the site. Like Paludititan above, Paralititan is based on a Greek word for the environment of deposition, in this case a tidal setting (Greek "paralos" means "near the sea"; Smith et al. 2001 translated the name loosely as "tidal giant"), and stromeri honors Ernst Stromer, the original describer of the Bahariya vertebrates, giving us "Stromer's tidal giant".

The type specimen is GCM 81119 (Egyptian Geological Museum, Cairo). It consists of two fused sacrals, the first caudal, another proximal caudal, dorsal and sacral ribs, partial scapulae, a complete left humerus and partial right humerus, part of a metacarpal, and some additional unstated bones. These remains were clustered in several clumps over an area about 6 m by 6 m (20 ft by 20 ft), with a carcharodontosaur tooth (Smith et al. 2001). In addition, Stromer (1932) described a large posterior dorsal (1912VIII64, now destroyed) which Smith et al. (2001) suggested was another specimen of Paralititan. Some other isolated titanosaur bones reported by Stromer (1932) as potentially from Aegyptosaurus cannot be confidently assigned to either taxon (Smith et al. 2001).

This is really a handy figure, isn't it? Item i is the left humerus of P. stromeri (Figure 4 in González Riga et al. 2019). CC-BY-4.0.

To be clear, this isn't a whole lot to go on. The scapula has a process similar to that of Brachiosaurus altithorax (Smith et al. 2001), which leads me to wonder if perhaps P. stromeri was also forelimb-dominant. The complete humerus is 1.69 m long (5.54 ft), then the longest known titanosaurian humerus but since overtaken by Notocolossus gonzalezparejasi. Paul (2019), noting the limited data, estimated that the type individual of P. stromeri could have massed anywhere between 30 and 55 tonnes (33 to 61 US tons).

Although "super-titanosaur = lognkosaur" has become a bit of a cliché, P. stromeri does not strongly exhibit this tendency. This may have to do with its incompleteness and relatively rare appearances in phylogenetic analyses. However, in the three recent papers that include it (Gorscak et al. 2017, Sallam et al. 2018, Gorscak and O'Connor 2019, as noted all using iterations of the same data set), it shows up consistently in the company of Maxakalisaurus topai, and just to be perverse, also with the classic saltasaurs Neuquensaurus and Saltasaurus in the 2018 and 2019 papers. Two things stand out: first, none of these are exactly large titanosaurs; second, none of them are from particularly near Egypt, either. Based on these studies, P. stromeri doesn't seem to be closely related to any other known African titanosaurs or to any other known super-titanosaurs. Go figure.

References

Calvo, J. O. and J. D. Porfiri. 2010. Panamericansaurus schroederi gen. nov. sp. nov. Un nuevo Sauropoda (Titanosauridae-Aeolosaurini) de la Provincia del Neuquén, Cretácico Superior de Patagonia, Argentina. Brazilian Geographical Journal: Geosciences and Humanities research medium 1:100–115.

Curry-Rogers, K. 2005. Titanosauria: a phylogenetic overview. Pages 50–103 in K. Curry-Rogers and J. Wilson, editors. The sauropods: Evolution and paleobiology. Indiana University Press, Bloomington and Indianapolis.

Csiki, Z., V. Codrea, C. Jipa-Murzea, and P. Godefroit. 2010. A partial titanosaur (Sauropoda, Dinosauria) skeleton from the Maastrichtian of Nǎlaţ-Vad, Haţeg Basin, Romania. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 258(3):297–324. doi:10.1127/0077-7749/2010/0098.

Csiki-Sava, Z., E. Buffetaut, A. Ősi, X. Pereda-Suberbiola, and S. L. Brusatte. 2015. Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago. Zookeys 469:1–161. doi:10.3897/zookeys.469.8439.

Díez Díaz, V., G. Garcia, X. Pereda Suberbiola, B. Jentgen-Ceschino, K. Stein, P. Godefroit, and X. Valentin. 2018. The titanosaurian dinosaur Atsinganosaurus velauciensis (Sauropoda) from the Upper Cretaceous of southern France: new material, phylogenetic affinities, and palaeobiogeographical implications. Cretaceous Research 91:429–456. doi:10.1016/j.cretres.2018.06.015.

França, M. A. G., J. C. de A. Marsola, D. Riff, A. S. Hsiou, and M. C. Langer. 2016. New lower jaw and teeth referred to Maxakalisaurus topai (Titanosauria: Aeolosaurini) and their implications for the phylogeny of titanosaurid sauropods. PeerJ 4:e2054. doi:10.7717/peerj.2054.

García, R. A., and L. Salgado. 2013. The titanosaur sauropods from the late Campanian-early Maastrichtian Allen Formation of Salitral Moreno, Río Negro, Argentina. Acta Palaeontologica Polonica 58(2):269–284.

González Riga, B. J., M. C. Lamanna, A. Otero, L. D. Ortiz David, A. W. A. Kellner, and L. M. Ibiricu. 2019. An overview of the appendicular skeletal anatomy of South American titanosaurian sauropods, with definition of a newly recognized clade. Academia Brasileira de Ciências 91(Supp. 2): e20180374. doi:10.1590/0001-3765201920180374.

Gorscak, E., and P. M. O’Connor. 2019. A new African titanosaurian sauropod dinosaur from the middle Cretaceous Galula Formation (Mtuka Member), Rukwa Rift Basin, southwestern Tanzania. PLoS ONE 14(2):e0211412. doi:10.1371/journal.pone.0211412.

Gorscak, E., P. M. O'Connor, E. M. Roberts, and N. J. Stevens. 2017. The second titanosaurian (Dinosauria: Sauropoda) from the middle Cretaceous Galula Formation, southwestern Tanzania, with remarks on African titanosaurian diversity. Journal of Vertebrate Paleontology 37(4):e1343250. doi:10.1080/02724634.2017.1343250.

Mannion, P., V. Díez Díaz, Z. Ciski-Sava, P. Upchurch, and A. Cuff. 2019. Dwarfs among giants: resolving the systematics of the titanosaurian sauropod dinosaurs from the latest Cretaceous of Romania. Journal of Vertebrate Paleontology, Program and Abstracts, 2019:148.

Paul, G. 2019. Determining the largest known land animal: A critical comparison of differing methods for restoring the volume and mass of extinct animals. Annals of Carnegie Museum 85(4):335–358.

Sallam, H. M., E. Gorscak, P. M. O’Connor, I. A. El-Dawoudi, S. El-Sayed, S. Saber, M. A. Kora, J. J. W. Sertich, E. R. Seiffert, and M. C. Lamanna. 2018. New Egyptian sauropod reveals Late Cretaceous dinosaur dispersal between Europe and Africa. Nature Ecology & Evolution 2:445–451. doi:10.1038/s41559-017-0455-5. Supplementary information.

Santucci, R. M., and A. C. de Arruda-Campos. 2011. A new sauropod (Macronaria, Titanosauria) from the Adamantina Formation, Bauru Group, Upper Cretaceous of Brazil and the phylogenetic relationships of Aeolosaurini. Zootaxa 3085:1–33.

Stromer, E. 1932. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharîjestufe (unterstes Cenoman). 11. Sauropoda. Abhandlungen der Bayerischen Akademie der Wissenschaften, Mathematisch-naturwissenschaftliche Abteilung, Neue Folge 10:1–20. [no two bibliographies ever give this citation the same way]

Smith, J. B., M. C. Lamanna, K. J. Lacovara, P. Dodson, J. R. Smith, J. C. Poole, R. Giegengack, and Y. Attia. 2001. A giant sauropod from an Upper Cretaceous mangrove deposit in Egypt. Science 292(5522):1704–1706.