This is important work on a very neglected sauropod (Ruyangosaurus). One brief comment: you mention hindlimb material (NHM R 5903) that was referred to Titanosaurus indicus by Swinton (1947). This specimen is part of the "Chhota Simla titanosaur", which a few years ago was provisionally referred to Jainosaurus (as Jainosaurus cf. septentrionalis) by Wilson et al. (2011) doi: 10.1111/j.1475-4983.2011.01087.x
Hence, it is probably advisable to at least mention this revision rather than refer to NHM R 5903 as "Titanosaurus indicus".
If, however, you have reason to doubt the referral of NHM R 5903 to Jainosaurus, and would prefer to treat this material as "Titanosaurus indicus", then reason(s) should be provided.
Pitekunsaurus and Muyelensaurus are recovered as members of Aeolosaurini in the original description of Overosaurus by Coria et al. (2013), yet your paper recovers the two genera as lognkosaurians, but doesn't include any other aeolosaurins in the cladistic analysis. Also keep in mind that Gallino and Otero (2015) recover Laplatasaurus, Uberatitan, and Bonitasaura as close relatives of all titanosaurs that you classify as members of Lognkosauria.
Coria, R. A.; Filippi, L. S.; Chiappe, L. M.; García, R.; Arcucci, A. B. (2013). "Overosaurus paradasorum gen. et sp. nov., a new sauropod dinosaur (Titanosauria: Lithostrotia) from the Late Cretaceous of Neuquén, Patagonia, Argentina". Zootaxa. 3683 (4): 357–376. doi:10.11646/zootaxa.3683.4.2.
Pablo A. Gallina & Alejandro Otero (2015) Reassessment of Laplatasaurus araukanicus (SAUROPODA: TITANOSAURIA), from the Late Cretaceous of Patagonia, Argentina. Ameghiniana 52 (5):487–501. doi:10.5710/AMGH.08.06.2015.2911 http://www.ameghiniana.org.ar/index.php/ameghiniana/article/view/1011
Hi, congrats for you work.
Some few issues, first, you may check D'Emic et al. (2012) and Mannion et al. (2013). According to their phylogeny, Ruyangosaurus should be placed in basal Somphospondyli. Moreover, Longkosauria is only reported in South America.
According Mannion et al. (2013) on Ruyangosaurus:
"Non-titanosaurian somphospondylan according to the LSDM, and non-lithostrotian titanosaurian according to the LCDM; regarded as a basal titanosaur (‘Andesauridae’) by Lü et al. (2009b), a non-titanosaurian somphospondylan by Mannion & Calvo (2011), and a somphospondylan by D’Emic (2012)"
Concerning to the femur estimate at 235 cm. The restored femur is apparently restored too long, comparing Ruyangosaurus with other somphospondylan sauropods such us Chubutisaurus, Tastavinsaurus... (which fit fairly fine), the femur should be considerably shorter (215-200 cm, possibly even less). A ratio as low as 0.54 of tibia-femur is not very reliable (127/235).
My intention is only to improve your work, so please take my observations as constructive.
D'Emic, M. D. (2012). «The early evolution of titanosauriform sauropod dinosaurs». Zoological Journal of the Linnean Society 166 (3): 624-671. doi:10.1111/j.1096-3642.2012.00853.x
P. D. Mannion, 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
In addition to ignoring Mannion et al. (2013), who included Ruyangosaurus in their phylogenetic analysis based on first-hand observation of the type material, there's also a 2014 monograph by Lü and colleagues that describes and illustrates a lot more material from the same individual of Ruyangosaurus: this would absolutely need to be included in any paper attempting to revise the phylogenetic placement of this taxon.
Lü, J. et al. 2014. Osteology of the giant sauropod dinosaur Ruyangosaurus giganteus Lü et al., 2009. Geological Publishing House Beijing, 211 pp.
The femur FMNH 13020 labeled as Argyrosaurus ?superbus? has been referred to Titanosauria indet. by Mannion and Otero (2012). Also, the results of the SVP abstract by Tschopp et al. 2016 have yet to be published (the Tschopp et al. 2017 cladistic analysis for Galeamopus pabsti doesn't recover the Dinosaur National Monument Apatosaurus as a member of Brontosaurus, although it does recover Brontosaurus as paraphyletic with respect to Amphicoelias). Lastly, it may be necessary to include the recently described Neocomian titanosaur Triunfosaurus (Carvalho et al. 2017) and the African Rukwatitan (Gorscak et al. 2014) in the phylogeny because Triunfosaurus is the oldest unambiguous titanosaur and Malawisaurus is recovered in your paper as a basal lognkosaur. Although Tengrisaurus (Averianov and Skutschas 2017) is based on too few remains to be included in the cladistic analysis of Ruyangosaurus, it might be worth comparing it to other longkosaurians given that it is roughly the same age as Malawisaurus.
A. Averianov and P. Skutschas. 2017. A new lithostrotian titanosaur (Dinosauria, Sauropoda) from the Early Cretaceous of Transbaikalia, Russia. Biological Communications 62(1):6-18.
Carvalho, I.S.; Salgado, L.; Lindoso, R.M.; de Araújo-Júnior, H.I.; Costa Nogueir, F.C.; Soares, J.A. (2017). "A new basal titanosaur (Dinosauria, Sauropoda) from the Lower Cretaceous of Brazil". Journal of South American Earth Sciences. doi:10.1016/j.jsames.2017.01.010.
Gorscak, Eric; O'Connor, Patrick M.; Stevens, Nancy J.; Roberts, Eric M. (2014). "The basal titanosaurian Rukwatitan bisepultus (Dinosauria, Sauropoda) from the middle Cretaceous Galula Formation, Rukwa Rift Basin, southwestern Tanzania". Journal of Vertebrate Paleontology. 34 (5): 1133–1154. doi:10.1080/02724634.2014.845568.
Mannion and Otero, 2012. A reappraisal of the Late Cretaceous Argentinean sauropod dinosaur Argyrosaurus superbus, with a description of a new titanosaur genus. Journal of Vertebrate Paleontology. 32(3), 614-638.
Emanuel Tschopp; Octávio Mateus (2017). "[Osteology of Galeamopus pabsti sp. nov. (Sauropoda: Diplodocidae), with implications for neurocentral closure timing, and the cervico-dorsal transition in diplodocids].". PeerJ. 5: e3179. doi:10.7717/peerj.3179.
I forgot to mention that the euhelopodid classification of Daxiatitan by D'Emic (2012) is questioned by Mannion et al. (2013) and Poropat et al. (2016), who recover Daxiatitan as a titanosaur (Averianov and Sues 2017 place Daxiatitan in Titanosauria as well). Also note that if the placement of Diamantinasaurus as sister to Savannasaurus by Poropat et al. (2016) holds, then Savannasaurus is also a lithostrotian because your analysis recovers Diamantinasaurus as a lithostrotian.
The cervical series from Big Bend National Park you mention has been described by Tykoski and Fiorillo (2017) and referred to Alamosaurus. Cladistic analysis by Tykoski and Fiorillo recovers Alamosaurus as sister to Futalognkosaurus, lending support to the hypothesis that Alamosaurus could be descended from a Patagonian titanosaur instead of an Asian lithostrotian like Opisthocoelicauda. You refer to Tapuiasaurus as a possible nemegtosaurid but at the same time leave Nemegtosaurus and Quaesitosaurus out of the cladistic analysis, and cladistic analyses of the sauropod Sarmientosaurus by Martinez et al. (2016) recover Nemegtosaurus in a different phylogenetic position than Tapuiasaurus and Rapetosaurus.
Averianov, Alexander; Sues, Hans-Dieter (2017). "Review of Cretaceous sauropod dinosaurs from Central Asia". Cretaceous Research. 69: 184. doi:10.1016/j.cretres.2016.09.006.
Rubén D. F. Martínez, Matthew C. Lamanna, Fernando E. Novas, Ryan C. Ridgely, Gabriel A. Casal, Javier E. Martínez, Javier R. Vita and Lawrence M. Witmer (2016). "A Basal Lithostrotian Titanosaur (Dinosauria: Sauropoda) with a Complete Skull: Implications for the Evolution and Paleobiology of Titanosauria". PLoS ONE. 11 (4): e0151661. doi:10.1371/journal.pone.0151661. PMC 4846048 . PMID 27115989.
S. F. Poropat, 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 6:34467:1-12
Ronald S. Tykoski; Anthony R. Fiorillo (2017). "An articulated cervical series of Alamosaurus sanjuanensis Gilmore, 1922 (Dinosauria, Sauropoda) from Texas: new perspective on the relationships of North America's last giant sauropod". Journal of Systematic Palaeontology. 15 (5): 339–364. doi:10.1080/14772019.2016.1183150.
This is not a comment on the results of the paper so much as it is constructive criticism on the presentation of the phylogenetic analysis through the figures and the text. The simple descriptions in the figure legends might be more appealing to some, but it should probably be displayed that the values displayed under the nodes are their bootstrap values. As well, I believe it is recommended that what the figure is displaying is mentioned within the figure legend, such as "50% majority results of the phylogenetic analysis", or something that simply states that it is a phylogenetic cladogram that is being shown. Finally, when there is an existing clade, such as Lognkosauria (Mendozasaurus + Futalognkosaurus) it should probably be indicated within the figure in some way, such as a label or a number that is identified in the legend.
Edit, since I forgot to mention this before: The strength of specific groupings of the phylogenetic analysis should be noted in the text, because of the possible strong groupings that are not in the strict consensus tree simply not because of complete support.
It needs to be made clearer what is a new hypothesis in this paper and what ideas have been previously suggested in the literature. For example, you call Notocolossus and Dreadnoughtus “probable” and “putative” lognkosaurs, despite neither being considered lognkosaurs in previous research, and in fact both species have been shown not to be lognkosaurs in the past (González Riga et al., 2016). In addition, the text references Puertasaurinae and Futalognkosaurinae, both of which are nomina nuda. I would like it to be made clearer what “Puertasaurinae” and “Futalognkosaurinae” refer to, and I also think you should refer to them as “Puertasaurus clade” and “Futalognkosaurus clade” or something similar, rather than using a nomen nudum.
The phylogenetic dataset contains 399 characters, not 400 as stated in the text. Of these 399 characters, 24 are invariant and 94 more only differ in one taxon, so only 281 characters are parsimony-informative. Several characters are incorrectly ordered, seemingly due to using the character numbers of the matrix of González Riga et al. rather than the numbers in your modified matrix (González Riga et al., 2016). Furthermore, some new characters should be modified and ordered. Characters 138, 342, and 363 all describe continuous variables split into three discrete states, and as such should be ordered, though character 342 has the states incorrectly ordered, and should have states 1 and 2 switched.
The taxon sampling of your phylogenetic analysis is insufficient to properly test the relationships of the taxa you propose to be lognkosaurs. Pitekunsaurus has previously been found to be an aeolosaurin, and Dreadnoughtus has been suggested to have an affinity to aeolosaurs as well (Coria et al., 2013; Ullmann & Lacovara, 2016). In order to properly test their relationships, you should include other aeolosaurs. As Ruyangosaurus has been previously recovered as a non-lithostrotian somphospondyl, you should include a wider sample of basal somphospondyls, especially the other gigantic Asian taxa. Also, you should include Quetecsaurus and Bonitasaura, as both have been hypothesized to be the sister taxa of Lognkosauria before (González Riga & David, 2014; Gallina & Otero, 2015).
I have not taken the time to thoroughly review your data matrix, but some errors have already stuck out at me. Both Pitekunsaurus and Ruyangosaurus lack distal femora, but you code them as having proximally-placed fourth trochanters. Also, your extra state for character 212 of González Riga et al. (your character 244) is unnecessary, as “procoelous/distoplatyan” and “opisthoplatyan” refer to the same morphology.
Please present your phylogenetic results more clearly. You should state the length and number of the most parsimonious trees. Moreover, majority-rule consensus trees can be misleading. I would recommend presenting a strict consensus tree with unstable taxa pruned a posteriori instead.
Please familiarize yourselves with the phylogenetic definition of Lognkosauria. Lognkosauria is a node-based clade, defined as the most recent common ancestor of Futalognkosaurus and Mendozasaurus and all of its descendants (Calvo et al., 2007). According to your majority rule tree, Drusilasaura, Dreadnoughtus, Traukutitan, Pitekunsaurus, and Notocolossus are not lognkosaurs, but rather close relatives of the clade.
Calvo JO., Porfiri JD., González-Riga BJ., Kellner AW. 2007. A new Cretaceous terrestrial ecosystem from Gondwana with the description of a new sauropod dinosaur. Anais da Academia Brasileira de Ciências 79:529–541.
Coria RA., Filippi LS., Chiappe LM., García R., Arcucci AB. 2013. Overosaurus paradasorum gen. et sp. nov. , a new sauropod dinosaur (Titanosauria: Lithostrotia) from the Late Cretaceous of Neuquén, Patagonia, Argentina. Zootaxa 3683:357. DOI: 10.11646/zootaxa.3683.4.2.
Gallina PA., Otero A. 2015. Reassessment of Laplatasaurus araukanicus (Sauropoda: Titanosauria) from the Upper Cretaceous of Patagonia, Argentina. Ameghiniana 52:487–501. DOI: 10.5710/AMGH.08.06.2015.2911.
González Riga BJ., David LO. 2014. A New Titanosaur (Dinosauria, Sauropoda) from the Upper Cretaceous (Cerro Lisandro Formation) of Mendoza Province, Argentina. Ameghiniana 51:3–25. DOI: 10.5710/AMEGH.26.12.1013.1889.
González Riga BJ., Lamanna MC., Ortiz David LD., Calvo JO., Coria JP. 2016. A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot. Scientific Reports 6:19165. DOI: 10.1038/srep19165.
Ullmann PV., Lacovara KJ. 2016. Appendicular osteology of Dreadnoughtus schrani, a giant titanosaurian (Sauropoda, Titanosauria) from the Upper Cretaceous of Patagonia, Argentina. Journal of Vertebrate Paleontology 36:e1225303. DOI: 10.1080/02724634.2016.1225303.
Brachiosaurus spp. should read Brachiosaurus altithorax in the cladogram due to the erection of Lusotitan for Brachiosaurus atalaiensis. Also, Baotianmansaurus and Dongyangosaurus should be entered into the data matrix to test the hypothesis by Averianov and Sues (2017) that they form a titanosaur clade outside Lithostrotia, and it might also be necessary to include Yongjinglong into the data matrix.
Averianov, Alexander; Sues, Hans-Dieter (2017). "Review of Cretaceous sauropod dinosaurs from Central Asia". Cretaceous Research. 69: 184. doi:10.1016/j.cretres.2016.09.006.
If you have an opportunity, you might want to scrutinize the original description of the Maastrichtian form Qinlingosaurus by Xue et al. (1996) to see how it compare with Ruyangosaurus because Qinlingosaurus has been seldom discussed in the literature since the original description by Xue et al. (1996).
Xue, Zhang, Bi, Yue and Chen (1996). The development and environmental changes of the intermontane basins in the Eastern part of Qinling Mountains. Geological Publishing House, Beijing. ISBN 7-116-02125-6. 179 pages.
Simon et al. (in press) describe the new Patagonian titanosaur Choconsaurus baileywillisi from the Huincul Formation (from which Argentinosaurus hails). Because Choconsaurus is recovered as a titanosaur outside Eutitanosauria, it should be prudent to add Choconsaurus into the data matrix for Ruyangosaurus.
Edith Simón; Leonardo Salgado; Jorge O. Calvo, in press. A new titanosaur sauropod from the Upper Cretaceous of Patagonia, Neuquén Province, Argentina. Ameghiniana. doi:10.5710/AMGH.01.08.2017.3051.
Currie et al. (in press) report the relocation of the Nemegtosaurus holotype quarry and describe newly discovered postcranial remains from the Nemegtosaurus type locality that they assign to the Nemegtosaurus mongoliensis holotype. The authors note that the postcranial material, which overlaps within the Opisthocoelicauda holotype, provides the first evidence suggesting a probable synonymy of Opisthocoelicauda with Nemegtosaurus (the anterior caudal that is assigned to the Nemegtosaurus holotype bears the same opisthocoelous condition in the Opisthocoelicauda anterior caudals that gives Opisthocoelicauda it name). Because Nemegtosaurus is now known from postcranial material that can be compared to Opisthocoelicauda, it may be imperative to incorporate Nemegtosaurus into the data matrix utilizing the postcranial data for this genus from Currie et al., but also Quaesitosaurus based on the description by Kurzanov and Bannikov (1983) (available at https://www.researchgate.net/profile/A_Bannikov/publication/270817108_A_new_sauropod_from_the_Upper_Cretaceous_of_Mongolia/links/54b51a130cf2318f0f971e87/A-new-sauropod-from-the-Upper-Cretaceous-of-Mongolia.pdf). Assuming that the Nemegtosaurus postcrania confirm the synonymy of Opisthocoelicauda with Nemegtosaurus, Opisthocoelicaudiinae would be a senior synonym of Nemegtosauridae and to avoid confusion, Saltasauroidea would be used for Saltasauridae sensu Sereno (1998) and Upchurch et al. (2004), with Opisthocoelicaudiinae sensu Sereno (1998) becoming Opisthocoelicaudiidae and Saltasaurinae sensu Sereno (1998) becoming Saltasauridae.
Also, the newly described Asian titanosaur Zhuchengtitan (Mo et al. 2017) should be mentioned in comparisons with Ruyangosaurus because it represents the latest addition to the Middle-Late Cretaceous titanosaur fauna from the Far East.
Philip J. Currie; Jeffrey A. Wilson; Federico Fanti; Buuvei Mainbayar; Khishigjav Tsogtbaatar, in press. Rediscovery of the type localities of the Late Cretaceous Mongolian sauropods Nemegtosaurus mongoliensis and Opisthocoelicaudia skarzynskii. Stratigraphic and taxonomic implications. Palaeogeography, Palaeoclimatology, Palaeoecology. doi:10.1016/j.palaeo.2017.10.035
Jinyou Mo; Kebai Wang; Shuqing Chen; Peiye Wang; Xing Xu (2017). A new titanosaurian sauropod from the Late Cretaceous strata of Shan-dong Province. Geological Bulletin of China 36 (9): 1501–1505.
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