Your Friends The Titanosaurs, part 28: Savannasaurus, Shingopana, and Sonidosaurus

This time we don't stop in Patagonia, instead visiting three different landmasses to meet three smallish titanosaurs known primarily from bones between the middle of the neck and the base of the tail. If you feel like you need a hit of fresh Patagonian titanosaurs, if you have access to the Journal of Vertebrate Paleontology allow me to suggest Otero et al. (2020), right off the presses, on the appendicular anatomy of Patagotitan mayorum. Or perhaps freely available Kundrát et al. (2020), dealing with an embryonic Patagonian titanosaur with a blunt horn?

Savannasaurus elliottorum

Savannasaurus elliottorum is our second Australian titanosaur (it's been a while since the first, Diamantinasaurus matildae). It also hails from the Winton Formation of Queensland in northeastern Australia. To date, there is only one publication focusing on S. elliottorum (Poropat et al. 2016), but I have it on good authority that a more detailed osteology is in the pipeline. [Update, 2020/09/30: The prophecy is fulfilled with Poropat et al. 2020!]

S. elliottorum is known from an associated partial skeleton, one of the best sauropod skeletons from Australia. This specimen, AODF 660 (Australian Age of Dinosaurs Museum, Winton, Queensland, Australia), was found at the "Ho-Hum Site", AODL 82, at Belmont sheep station. It includes (deep breath): a posterior cervical vertebra, eight dorsals, at least four fused sacrals, at least five partial caudals, several cervical and dorsal ribs, a fragmentary scapula, the left coracoid, both sternal plates, incomplete left and right humeri, a shattered ulna, the left radius, all five metacarpals of the right hand and the left metacarpal IV, two manual phalanges, fragments of both ilia, fused pubes and ischia, the left astragalus, the right metacarpal III, and fragments. These bones were found in a single large concretion (Poropat et al. 2016). "Savanna" in the name refers to the countryside of the discovery locality, and "elliottorum" honors the Elliott family for their contributions to Australian paleontology (Poropat et al. 2016), giving us something like "the Elliott family's savanna lizard".

The association of the holotype elements of S. elliottorum (scale bar 1 m). Figure 3 in Poropat et al. (2016). CC-BY-4.0.

The most outstanding anatomical feature of S. elliottorum is its wide hips: the incomplete sacrum is greater than a meter wide (more than 40 inches) at its narrowest point for a titanosaur of modest dimensions, and the fused lower pelvic bones are also more than a meter wide. The cervical ribs are elongate. The cervical vertebra has a keel on the ventral side of the centrum, unlike most macronarians, while the dorsals do not have keels, unlike Diamantinasaurus. The caudals are amphicoelous, but the anterior part of the tail is not known, so it is not clear if there were no procoelous caudals at all or if they were confined to the base of the tail. The sternal plates are large, as in other titanosaurs, but do not have the typical bean shape of titanosaurian sternals. The presence of a couple of manual phalanges shows that this titanosaur had not reduced its hands to metacarpals only (Poropat et al. 2016).

The skeleton of S. elliottorum, with a 500 mm scale bar. Figure 4 in Poropat et al. (2016). CC-BY-4.0.

Proportionally, S. elliotorum has much wider hips than Diamantinasaurus, and the forelimbs are built quite differently. The longest metacarpal of S. elliottorum is about half (0.49) the length of the radius, which in turn is around three-quarters the length of the humerus, while in D. matildae the longest metacarpal is 0.61 times the length of the radius, which is 0.63 times the length of the humerus (Poropat et al. 2016). In other ways, though, they are similar forms (Poropat et al. 2016), and in phylogenetic analyses the two are either closely related in a small clade with AODF 836 (described as a second specimen of D. matildae in Poropat et al. 2016), or in similar positions in the titanosaur tree without forming a clade (except for one result in Mannion et al. 2019; extended implied weights and K=3 if you're curious).

Shingopana songwensis

Shingopana songwensis makes the third titanosaur from the Galula Formation of Songwe, Tanzania, and the second from the Namba Member. For reference, Rukwatitan bisepultus is the other titanosaur named from the Namba Member, and Mnyamawamtuka moyowamkia is from the underlying Mtuka Member. S. songwensis is not as well-represented as M. moyowamkia, nor does it have the interesting taphonomic history of R. bisepultus; instead, it gets by on the basis of its neck.

S. songwensis is based on a partial associated skeleton excavated 2002–2004 from the TZ-07 locality west of Mbeya in Songwe, Tanzania. This skeleton was recovered from a mudstone lens in a dominantly sandstone unit of the Namba Member. Some of the bones have evidence of borings, interpreted as insect borings. The bones were found in an area less than 2.5 m by 2.5 m (8.2 ft by 8.2 ft), and primarily represent the neck and anterior torso. They are catalogued as RRBP 02100 (Rukwa Rift Basin Project collection of the Tanzanian Antiquities Unit in Dar es Salaam, Tanzania), and include a left angular, a partial anterior cervical, four more posterior cervicals, six partial cervical ribs and four partial dorsal ribs, a nearly complete left humerus, and a partial left pubis (Gorscak et al. 2017). The genus name come from the Kiswahili "shingo" meaning "neck" and "pana" meaning "wide", which Gorscak et al. chose in reference to the "bulbous expansion of the neural spine exhibited by the well-preserved cervical vertebra", while "songwensis" refers to the Songwe area and geologic sub-basin. Together these give us something like "wide-neck from Songwe".

As indicated by the etymology, there is indeed a prominent expansion on the neural spine of the best-preserved cervical, a feature also seen on Bonitasaura salgadoi, Overosaurus paradasorum, and Trigonosaurus pricei. S. songwensis also has flanges on the dorsal ribs like those of Overosaurus (Gorscak et al. 2017). The humerus is 815 mm long (32 inches) (Gorscak et al. 2017), indicating a smallish titanosaur (that humerus is not a great deal longer than the best humerus of Rinconsaurus).

S. songwensis is distinguished by a single autapomorphy, having to do with the laminae of the cervicals (Gorscak et al. 2017), but can be readily distinguished from the other Galula Formation titanosaurs. In fact, to date it has yet to show up as closely related to either of them, or to any other African titanosaurs for that matter. Instead, it shows a definite attraction to the aeolosaurs and Normanniasaurus genceyi (Gorscak et al. 2017; Sallam et al. 2018; Gorscak and O'Connor 2019). Interestingly, it manages this without any caudal vertebrae being known to date. Shingopana and Normanniasaurus as members of the aeolosaur lineage imply an earlier divergence and wider distribution of aeolosaurs than previously thought (Gorscak et al. 2017).

Sonidosaurus saihangaobiensis

For its relative age (a 2006 publication date means it predates approximately half of the titanosaurs named so far), Sonidosaurus saihangaobiensis has not received a lot of press, which we can attribute at least in part to the sparseness of its known material. It's another case of enough information to be interesting but not enough to do much with.

S. saihangaobiensis is based on an associated partial skeleton excavated in 2001 from fluvial sandstone in the Iren Dabasu Formation (=Erlian Formation, spelled Elian Formation in Xu et al. 2006), at Saihangaobi, Sonid Zuoqi, Inner Mongolia in China. This formation is rather better known for its theropods, such as the giant oviraptorosaur Gigantoraptor. Gigantoraptor happens to come from the same place as S. saihangaobiensis: as the story goes, the first specimen of Gigantoraptor was found during a re-enactment of the discovery of Sonidosaurus for a documentary. With the locality information in hand, it unsurprisingly turns out that the name of this titanosaur is a double geographical reference: "Sonid lizard from Saihangaobi" (Xu et al. 2006). The holotype and only known specimen is LH V 0010 (Long Hao Geologic and Paleontological Research Center, Hohhot, Inner Mongolia). It includes five dorsals, the last sacral, an anterior caudal, several dorsal ribs, a chevron, and a partial pelvis. The type individual is interpreted as a mature but smallish titanosaur, on the order of 9 m long (30 ft) (Xu et al. 2006).

The neural arches of the dorsals are relatively tall for a titanosaur, but the neural spine part of the arch is relatively short. The spine is not deeply divided on the midline, as seen in diplodocoids, but does have a dip in its wide upper margin ("saddle-shaped" or "weakly bifid" per Xu et al. 2006). As in Opisthocoelicaudia skarzynskii, the anterior caudal is opisthocoelous (Xu et al. 2006), which naturally leads to thoughts about the two being related. The ilium is flared and has pneumatic chambers (Xu et al. 2006).

Xu et al. (2006) interpreted S. saihangaobiensis as a titanosaur with a mix of basal and derived features, and with many similarities to Opisthocoelicaudia. Other authors have generally accepted it as a titanosaurian of poorly understood affinities (e.g., Mannion et al. 2013, 2019; Averianov and Sues 2017; Averianov and Lopatin 2020); D'Emic (2012) was non-committal on the titanosaur aspect (text vs. Table 9). There is a mounted skeleton out there, but I'm not sure what to make of it, given the only described specimen includes fewer than two dozen bones. (Unless, of course, there is unpublished material including substantially more of the skeleton, in which case it would be nice to have that published, rather than only on display like poor "Nurosaurus".)

References

Averianov, A. O., and A. V. Lopatin. 2020. An unusual new sauropod dinosaur from the Late Cretaceous of Mongolia. Journal of Systematic Palaeontology (advance online publication). doi:10.1080/14772019.2020.1716402.

Averianov, A., and H.-D. Sues. 2017. Review of Cretaceous sauropod dinosaurs from central Asia. Cretaceous Research 69:184–197. doi:10.1016/j.cretres.2016.09.006.

D'Emic, M. D. 2012. The early evolution of titanosauriform sauropod dinosaurs. Zoological Journal of the Linnean Society 166(3):624–671.

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.

Kundrát, M., R. A. Coria, T. W. Manning, D. Snitting, L. M. Chiappe, J. Nudds, and P. E. Ahlberg. 2020. Specialized craniofacial anatomy of a titanosaurian embryo from Argentina. Current Biology (advance online publication). doi:10.1016/j.cub.2020.07.091.

Mannion, P. D., P. Upchurch, R. N. Barnes, and O. Mateus. 2013. Osteology of the Late Jurassic Portuguese sauropod dinosaur Lusotitan atalaiensis (Macronaria) and the evolutionary history of basal titanosauriforms. Zoological Journal of the Linnean Society 168:98–206. doi:10.1111/zoj.12029.

Mannion, P. D., P. Upchurch, X. Jin, and W. Zheng. 2019. New information on the Cretaceous sauropods of Zhejiang Province, China: impact on Laurasian titanosauriform phylogeny and biogeography. Royal Society Open Science 6(8):191057. doi:10.1098/rsos.191057.

Otero, A., J. L. Carballido, and A. P. Moreno. 2020. The appendicular osteology of Patagotitan mayorum (Dinosauria, Sauropoda), Journal of Vertebrate Paleontology, article e1793158. doi:10.1080/02724634.2020.1793158.

Poropat, S. F., P. D. Mannion, P. Upchurch, S. A. Hocknull, B. P. Kear, M. Kundrát, T. R. Tischler, T. Sloan, G. H. K. Sinapius, J. A. Elliott, and D. A. Elliott. 2016. New Australian sauropods shed light on Cretaceous dinosaur palaeobiogeography. Scientific Reports 6:article number 34467. doi:10.1038/srep34467.

[Poropat, S. F., P. D. Mannion, P. Upchurch, T. R. Tischler, T. Sloan, G. H. K. Sinapius, J. A. Elliott, and D. A. Elliott. 2020. Osteology of the wide-hipped titanosaurian sauropod dinosaur Savannasaurus elliottorum from the Upper Cretaceous Winton Formation of Queensland, Australia. Journal of Vertebrate Paleontology article e1786836. doi:10.1080/02724634.2020.1786836.] [added 2020/09/30]

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.

Xu X., Zhang X., Tan Q., Zhao X., and Tan L. 2006. A new titanosaurian sauropod from Late Cretaceous of Nei Mongol, China. Acta Geologica Sinica 80(1):20–26.