Sunday, November 25, 2018

Your Friends The Titanosaurs, part 6: Austroposeidon, titanosaurs of Balochistan, and Baotianmansaurus

For Thanksgiving (US), we're getting overstuffed with extra titanosaurs. We're also venturing to three different Cretaceous landmasses: South America for Austroposeidon magnificus, the formerly separate landmass of the Indian Plate for a group of titanosaurs from Pakistan, and Asia for Baotianmansaurus henanensis.

Austroposeidon magnificus

Austroposeidon magnificus is one of the newest members of Titanosauria, having been described in 2016 by Bandeira et al. As such, it hasn't had the chance to feature in a lot of publications, although it does make a cameo in Brusatte et al. (2017). It's best known for its size, estimated at 25 m (82 ft) long, making it the biggest dinosaur yet found in Brazil (Bandeira et al. 2016). In recognition of this, it has a suitable name: "austro" for southern, "poseidon" from the Greek god Poseidon, responsible for earthquakes (and the sea and some other things, but when applied to sauropods, it's the earthquake part being alluded to), and "magnificus" from the Latin adjective for "great, elevated, or noble" (Bandeira et al. 2016). This gets you something like "noble southern earthquake-maker".

A. magnificus is another of those dinosaurs where the fossils were found several decades before they were described. In this case, the fossils were collected by founding Brazilian paleontologist Llewellyn Ivor Price in 1953. Price obtained them from near Presidente Prudente in São Paulo State, southern Brazil. The area is now urbanized and the site cannot be relocated, as the modern describers found, but the rocks can be attributed to the Upper Cretaceous Presidente Prudente Formation of Campanian–Maastrichtian age (Bandeira et al. 2016). Interestingly, as noted by Brusatte et al. (2017), this formation has also produced the latest known fossils of carcharodontosaurid theropods.

The holotype and only known specimen of A. magnificus consists of two partial cervical vertebrae (the last two, at the base of the neck), a cervical rib, a dorsal vertebra (the first), seven dorsal vertebra fragments, and a fragment of a sacral vertebra. They are interpreted as representing one individual, and are cataloged as MCT 1628-R (Museu de Ciências da Terra, in Rio de Janeiro) (Bandeira et al. 2016). The bones of A. magnificus have suffered somewhat from taphonomic processes, becoming somewhat twisted and compressed. They were found in a fine-grained sandstone that Bandeira et al. (2016) interpreted as possibly a crevasse splay deposit (the deposit you get when a river breaks through its levees and leaves sediment in the floodplain).

Being that all there is to work with are a few vertebrae and pieces of vertebrae, A. magnificus is diagnosed by various details of the laminae and processes of the neural spines. More broadly, Bandeira et al. (2016) found it to be the sister group to Lognkosauria, the titanosaur clade that tends to inexorably draw in the largest titanosaurs.

Figure 4e of Brusatte et al. (2017), showing the type material of Austroposeidon magnificus; unfortunately, the caption is missing descriptions of the elements. I apologize in advance; this isn't going to be the most image-rich post I've ever done.

Balochistan's titanosaurs

To date, the study of Pakistan's dinosaurs has been conducted almost entirely by M. Sadiq Malkani, for many years with the Geological Survey of Pakistan. He has documented the fossils in a number of works, mostly extended symposium abstracts, which can be accessed from his ResearchGate page. The most abundant of the fossils are Upper Cretaceous titanosaur bones from Balochistan, which Malkani has divided among nine genera and species. For expediency, I'm going to deal with all of these titanosaurs at once. For one thing, if I dealt with them separately as they came up, the entries would all be very similar: they're all from the same formation and the same region, and I'd have to deal with the same issues each time, too.

I think it would be fair to say that outside observers have not exactly taken the various genera and species into their hearts. Some people suggest that none of them have been properly described according to the rules of taxonomy (symposium abstracts are a type of publication not usually accepted for taxonomic purposes, while others of the publications have other technical issues). Others accept the first batch but not a more recent group. Depending on how you interpret the rules and the many publications, you may consider different citations as the publications of record. Even if they are all validly named, it's rather unlikely that they are all actually distinct taxa, because that would mean nine coexisting titanosaur species. ("But the Morrison Formation!" someone shouts. What about it? It covers more time and space than the Pab Formation, or Vitakri Formation of the most recent publications, and the Morrison sauropods feature several very different body plans.)

Omitting track taxa such as Pashtosaurus zhobi, and the Upper Jurassic Brohisaurus kirthari, which is considered to be a titanosauriform, our cast of characters can be divided into two groups based on when they were described. The first batch is more widely known and includes five genera and species. They are generally accepted as officially named in 2004 or 2006; the most thorough early descriptions appear to be in the citation I'm giving as Malkani (2006), but be aware that this is only one of several publications he produced that year; it's just the only 2006 paper I'm citing here. (Alternatively, if you're not up to dealing with the numerous original papers, you can find good summaries in Glut 2010 and 2012.) Each genus and species is based on a few caudal vertebrae, usually with various other remains referred.
  • Balochisaurus malkani
  • Khetranisaurus barkhani
  • Marisaurus jeffi
  • Pakisaurus balochistani
  • Sulaimanisaurus gingerichi
The more controversial second batch includes four genera and species which were first mentioned in 2014–2015. Malkani (2015; again, not the only 2015 paper!) seems to be the most authoritative source, but only has detailed descriptions of Maojandino and Nicksaurus, referring the reader to accounts in abstract volumes for the other two. Unfortunately, no differential diagnosis is offered for any of the four (unlike Malkani 2006), which is a missed opportunity. As a publication of the Geological Survey of Pakistan rather than a symposium abstract, Malkani (2015) would have been an ideal venue to explicitly deal with all of the various tasks associated with formally defining new genera and species.
  • Gspsaurus pakistani
  • Maojandino alami
  • Nicksaurus razashahi
  • Saraikimasoom vitakri
A significant difference this time around is that the taxa are no longer based on a few caudals. Gspsaurus and Saraikimasoom are both based on cranial material, and Maojandino and Nicksaurus are based on partial skeletons. Indeed, by this point several associated skeletons or other significant specimens are mentioned: one for Balochisaurus, one for Gspsaurus, one for Maojandino, three for Marisaurus, one for Nicksaurus, four for Pakisaurus, one for Saraikimasoom, and two for Sulaimanisaurus (Malkani 2017). (Leaving aside the number of species, I would be hesitant to refer material to taxa with the limited holotypes of the first batch, knowing the sad history of Titanosaurus indicus and others that were based on a few caudals).

One of the more unusual aspects of the publications is the use of a parallel system of classification, with several local families and subfamilies, some expressly used in place of existing names. For example, Balochisauridae is used as a substitute for Saltasauridae, and Pakisauridae is used as a substitute for the erstwhile Titanosauridae. Malkani has recently separated the taxa into three groups (Malkani 2018; you will find other configurations in older works): the Pakisauridae (Khetranisaurus, Pakisaurus, and Sulaimanisaurus), large-bodied but slender armored titanosaurs; the marisaurs (Gspsaurus, Maojandino, and Marisaurus), medium-sized, stocky, heavy, armored titanosaurs; and Balochisauridae (Balochisaurus, Nicksaurus, and Saraikimasoom), small-bodied, stocky, light, armored titanosaurs. The frequent reporting of osteoderms is a bit odd (as are some of the shapes of objects described as osteoderms); there will be a time to go into titanosaur armor in more detail later, but suffice it to say that armored titanosaurs from elsewhere appear to have had only a sparse covering of large plates, surrounded by abundant millimeter-scale bits (Cerda et al. 2015). One very unusual reported feature is a trispinous last caudal vertebra (Malkani 2015); unfortunately the small figures are difficult to interpret. (The publications are often supplied with numerous photos, but they are usually very small and of low resolution.)

These titanosaurs have not received a great deal of coverage outside of Malkani's works. Wilson et al. (2011) did not consider any of the taxa then named to be valid, regarded one specimen as referable to Isisaurus colberti and others potentially referable to Isisaurus or Jainosaurus, and postulated that Malkani's Pakisauridae and Balochisauridae may reflect an Isisaurus/Jainosaurus-like division. Malkani (2017) commented on this, regarding both Isisaurus and Jainosaurus as pakisaurids and suggesting that as few as three genera were present on the Indian-Pakistan landmass: Isisaurus/Sulaimansaurus, Jainosaurus/Pakisaurus, and Balochisaurus or another balochisaurid.

Baotianmansaurus henanensis

Baotianmansaurus henanensis is another titanosaur of fairly recent vintage. It is is our first representative of a small but growing group of Chinese titanosaurs. None of them have received much press to date, and all of them are very incompletely known. B. henanensis was described in Zhang et al. (2009). The genus name refers to the Baotianman natural preservation area, and the species name refers to Henan Province in east-central China.

There's not a lot known for Baotianmansaurus henanensis: the holotype includes a couple of partial dorsals (third and fifth), one and a half sacrals, a partial anterior caudal, three complete and two partial ribs, part of the distal scapula, and fragments. The material is cataloged as 41HIII-0200 at the Henan Geological Museum in Zhengzhou. These fossils were found northwest of Nanyang City in Neixing County; the formation was originally given as the Gaogou Formation (Zhang et al. 2009), but this name has been superseded by the Xiaguan Formation, considered to be of uncertain early Late Cretaceous age (Wang et al. 2013). There are a few unusual features: the neural spine of the third dorsal is bifid, very uncommon among titanosaurs (Opisthocoelicaudia, or Nemegtosaurus if you prefer, is the best-known example); the ribs are not pneumatic; and the caudal vertebra is amphicoelous (concave on both ends of the centrum) rather than procoelous (concave anterior, convex posterior), with a centrum that is shorter than it is wide (Zhang et al. 2009).

Zhang et al. (2009) originally described Baotianmansaurus henanensis as a titanosauriform, probably a titanosaurid. Since then, a titanosaurian consensus has appeared (Mannion et al. 2013; Poropat et al. 2016; Averianov and Sues 2017; Gonzàlez Riga et al. 2018), apart from a brief sojourn with the ever-enigmatic Euhelopus (D'Emic 2012). In fact, Baotianmansaurus has shown up in a surprising number of analyses for something that's basically five partial vertebrae and accessories. It has so far proven inseparable from fellow Chinese titanosaur Dongyangosaurus sinensis, represented by somewhat more complete material. The two of them appear to be similar to an as-yet unnamed titanosaur from the Bissekty Formation of Uzbekistan (Averianov and Sues 2017).

References

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

Bandeira, K. L., F. M. Simbras, E. B. Machado, D. de Almeida Campos, G. R. Oliveira, and A. W. A. Kellner. 2016. A new giant Titanosauria (Dinosauria: Sauropoda) from the Late Cretaceous Bauru Group, Brazil. PLoS ONE 11(10):e0163373. doi:10.1371/journal.pone.0163373.

Brusatte, S. L., C. R. A. Candeiro, and F. M. Simbras. 2017. The last dinosaurs of Brazil: the Bauru Group and its implications for the end-Cretaceous mass extinction. Anais de Academia Brasileira de Ciências 89(3):1465–1485.

Cerda, I. A., R. A. García, J. E. Powell, and O. Lopez. 2015. Morphology, microanatomy, and histology of titanosaur (Dinosauria, Sauropoda) osteoderms from the Upper Cretaceous of Patagonia. Journal of Vertebrate Paleontology 35(1):e905791. doi:10.1080/02724634.2014.905791.

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

Gonzàlez Riga, B. J., P. D. Mannion, S. F. Poropat, L. D. Ortiz David, and J. P. Coria. 2018. Osteology of the Late Cretaceous Argentinean sauropod dinosaur Mendozasaurus neguyelap: implications for basal titanosaur relationships. Zoological Journal of the Linnean Society 184(1):136–181. doi:10.1093/zoolinnean/zlx103.

Glut, D. F. 2010. Dinosaurs: the encyclopedia. Supplement 6. McFarland & Company, Inc., Jefferson, North Carolina.

Glut, D. F. 2012. Dinosaurs: the encyclopedia. Supplement 7. McFarland & Company, Inc., Jefferson, North Carolina.

Malkani, M. S. 2006. Biodiversity of saurischian dinosaurs from the Latest Cretaceous of Pakistan. Journal of Applied and Emerging Sciences 1(3):108–140.

Malkani, M. S. 2015. Dinosaurs, mesoeucrocodiles, pterosaurs, new fauna and flora from Pakistan. Geological Survey of Pakistan Information Release 823.

Malkani, M. S. 2017. A review of Pakisaurus titanosaur: Associated skeletons of sauropod and theropod dinosaurs and mesoeucrocodiles from Pakistan: Discussion on titanosaurs of Indo-Pak subcontinent. Proceedings of the Korean Geological Society, 2017 Fall Conference of Geological Sciences Union, Fifth International Symposium of International Geoscience Programme IGCP Project 608, “Cretaceous Ecosystems and Their Responses to Paleoenvironmental Changes in Asia and the Western Pacific” October 22-28, 2017, Jeju Island, Korea, 116–119.

Malkani, M. S. 2018. Two groups of titanosaurian sauropods based on two morphs of pes; a new hypothesis based on tracks and bone records. Researchgate.net Research.

Malkani, M. S., and S. Ge. 2016. Fossil biotas from Pakistan with focus on dinosaur distributions and discussion on paleobiogeographic evolution of Indo-Pak Peninsula. Global Geology 19(4):230–240.

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.

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.

Wang, R.-F., H.-L. You, S.-C. Xu, S.-Z. Wang, J. Li, L.-J. Xie, L. Jia, and Y.-X. Li. 2013. A new hadrosauroid dinosaur from the early Late Cretaceous of Shanxi Province, China. PLoS ONE 8(10):e77058. doi:10.1371/journal.pone.0077058.

Wilson, J. A., P. M. Barrett, and M. T. Carrano. 2011. An associated partial skeleton of Jainosaurus cf. septentrionalis (Dinosauria: Sauropoda) from the Late Cretaceous of Chhota Simla, central India. Palaeontology 54(5):981–998.

Zhang X., Lü J., Xu L., Li J., Yang L., Hu W., Jia A., Ji Q., and Zhang C. 2009. A new sauropod dinosaur from the Late Cretaceous Gaogou Formation of Nanyang, Henan Province. Acta Geologica Sinica 83(2):212–211.

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