Your Friends The Titanosaurs, part 30 continued: the rest of Titanosaurus

I hope you've saved room for Round II! This time we visit three continents and most of the Cretaceous as we finish off the rest of the species attributed to Titanosaurus. Our guests are "Titanosaurus" falloti, "T." lydekkeri, "T." nanus, and "T." valdensis. Not all of them are still thought to be titanosaurs, and all four are mostly footnotes these days.

"Titanosaurus" falloti

"T." falloti was described in Hoffet (1942) from a complete but damaged right femur, the distal end of another femur, and two femoral heads, recovered from the Muong Phalane area of Laos. Hoffet also referred a cylindrical tooth, incomplete humeral head, possible scapula, and an amphicoelous caudal to Titanosaurus sp. These specimens were placed in the Musée du Service géologique in Hanoi. The species name "falloti" honors Hoffet's professor Paul Fallot, and with the genus name gives us something like "Paul Fallot's titan lizard". The complete femur was flattened during fossilization and later had been damaged by a tree growing over it, which weakened it. During collection, it broke into three pieces and the outer layer splintered badly. Hoffet measured it as 175 cm long (68.9 in), indicating a large sauropod (certainly quite a bit bigger than the femur Lydekker assigned to T. indicus, but not really into truly titanic sauropod range). Hoffet reported several differences from known femora of titanosaurs, such that it's not entirely clear to me why it ended up in Titanosaurus.

At the time, the rocks were thought to be Senonian in age (Coniacian–Maastrichtian), but the host formation, the Grès supérieurs Formation, is now known to be much older, dating to the Aptian–Albian of the Early Cretaceous (Allain et al. 1999). More sauropod bones were recovered from this formation in the 1990s, to the south in Tang Vay; these specimens became the basis for Tangvayosaurus hoffeti (Allain et al. 1999), which is one of these euhelopodid/huabeisaur/phuwiangosaur species that generally hangs out near but outside of Titanosauria, occasionally jumping in when the base of Titanosauria becomes a messy polytomy.

"T." falloti doesn't get much discussion, except when authors either propose to include it or exclude it from some other genus. McIntosh (1990) included it among the valid sauropods and wrote that it "may belong to another genus and possibly another family." Allain et al. (1999) regarded it as indeterminate within Tangvayosaurus (as T. sp.) but refrained from making a formal synonymization at the species level because they couldn't find any distinguishing characteristics in the type material of "T." falloti. Wilson and Upchurch (2003) disagreed with this decision, preferring to describe it as an indeterminate titanosaur. The two authors then went different directions, Upchurch et al. (2004) describing it as a dubious sauropod, while Wilson (2005) accepted "T." falloti as a synonym of Tangvayosaurus. Meanwhile, Pang and Cheng (2000) recommended placing the species in their new genus Huabeisaurus, another sauropod similar to Tangvayosaurus, but later contributed to another paper which stated that H. allocotus and "T." falloti did not belong to the same genus (D'Emic et al. 2013). With two sets of authors independently allying "T." falloti to euhelopodid/huabeisaur/phuwiangosaur-type sauropods (Allain et al. 1999; Pang and Cheng 2000), I can't help but thinking "where there's smoke, there's fire."

"Titanosaurus" lydekkeri

There are obscure sauropods, and then there's "Titanosaurus" lydekkeri. "T." lydekkeri goes back to a caudal mentioned briefly in Lydekker (1888a), cataloged as NHMUK 32390 (BMNH in older references; Natural History Museum, London), from the Upper Greensand of the Isle of Wight. This specimen is a strongly procoelous anterior caudal with partial neural spine, placed anteriorly on the centrum (Le Loeuff 1993). Lydekker, regarding it as a specimen of his Titanosaurus, described it as larger than Wealden "Titanosaurus" caudals (see "T." valdensis below), and potentially the same as Dinodocus mackesoni. He reiterated most of this information in Lydekker (1888b), except now identifying it as Titanosaurus sp. b. It was apparently purchased circa 1857, and measured 175 mm long (6.89 in) (apparently just the centrum), with an anterior articular surface 140 mm tall (5.51 in) and 120 mm across (4.72 in) (Lydekker 1888b).

Huene (1929) opted to name it as a new species of Titanosaurus, although he was not sure if it really belonged to Titanosaurus; the species name honors Lydekker. McIntosh (1990) tentatively sank the species into Macrurosaurus semnus (an assortment of sauropod caudals; Le Loeuff 1993) without discussion. Le Loeuff (1993), reviewing European titanosaurs, provisionally regarded the species as dubious, but did not make it a second species of Iuticosaurus as reported in Wilson and Upchurch (2003). That combination has popped up in other papers, though (Molnar and Wiffen 2007). The general feeling is that "T." lydekkeri is an indeterminate titanosaur (Le Loeuff 1993; Naish and Martill 2001; Wilson and Upchurch 2003).

"Titanosaurus" nanus

Lydekker named this species in 1893 for "two apparently associated anterior dorsal and cervical vertebrae from Neuquen, which, from the absence of any trace of a neuro-central suture seem to be undoubtedly adult, and are far too small to have pertained to a fullgrown individual of T. australis." In fact, he felt they were so small that he considered the referral to Titanosaurus as only tentative, denoting the species Titanosaurus (?) nanus (creating the contradictory "dwarf titan lizard").

Lydekker's types are now cataloged as MLP-Ly 18 and MLP-Ly 19 (Museo de La Plata in La Plata, Argentina) (Powell 2003; Otero and Reguero 2013). D'Emic and Wilson (2011) stated that the vertebrae were from the Titanosaurus australis (=Neuquensaurus) type locality, although there is nothing to say either way in Lydekker (1893), and Powell (2003) described the provenance as the "right bank of Río Neuquén, between 2 and 4 km before the railway bridge which crosses this river, very close to the city of Neuquén", tentatively in the Bajo de la Carpa Member of the Río Colorado Formation (=Bajo de la Carpa Formation).

Part of Plate III in Lydekker (1893). Items 1 and 3 are the type vertebrae of "T." nanus (MLP-Ly 18 and 19, respectively and retroactively), while 2 is the type vertebra of Microcoelus patagonicus.

And here they are today, depicted in Otero and Reguero (2013) (scale bar 100 mm). 1–3 are MLP-Ly 19, a cervical, and 4–6 are MLP-Ly 18, a dorsal. CC-BY-4.0, apparently.

"T." nanus never attracted much interest historically, and of late has been either sunk into australis (McIntosh 1990; Upchurch et al. 2004) or abandoned as indeterminate (Powell 2003; Wilson and Upchurch 2003; Otero and Reguero 2013).

"Titanosaurus" valdensis

You may be more familiar with this species under its 1990s guise of "Iuticosaurus, Very Early Titanosaur". The fossils of concern first came to notice in Lydekker (1887), in which Lydekker discussed two unusual caudal centra from the Wealden of Brook on the Isle of Wight. They had been obtained for the British Museum from noted collector William Fox and cataloged as R. 151 and R. 146a. Lydekker compared them favorably to T. indicus and "T." blanfordi caudals, regarding them as most like blanfordi. Although there was certainly a resemblance, he was not quite ready to commit to them as Titanosaurus specimens, instead deciding that they were more likely caudals of Ornithopsis. He came to this conclusion essentially because Ornithopsis was there and no caudals had yet been reported for it. (I'm quite serious.) Having made this deduction, he then entertained the notion that Titanosaurus might be a synonym of Ornithopsis, or at least in the same family, Ornithopsidae. A brief discussion followed, in which other members of the Geological Society expressed doubts that Ornithopsis had anything to do with these vertebrae, and Harry Govier Seeley (by implication) considered both the Indian and Isle of Wight specimens to be inadequate for identification, anticipating Wilson and Upchurch by almost 120 years. The two Isle of Wight specimens are indeed more promise than substance; as described by Lydekker, R. 151 is water-tumbled and R. 146a is just the anterior half of a centrum.

Behold, NHMUK R151, from Seeley (1887).

By the next year, Lydekker had committed to Titanosaurus over Ornithopsis and identified the two specimens as Titanosaurus sp. a. Forty years later, Huene (1929) gave the two specimens the name Titanosaurus valdensis, or roughly "titan lizard from the Weald". Le Loeuff (1993) transferred them to a new genus, Iuticosaurus, a reference to the Jutes of England (of course, in the Latin alphabet "Jute" begins with an I). Le Loeuff also referred a third caudal to the species, R1886 from an unknown Wealden locality on the Isle of Wight. This one is more is more complete, including part of the neural arch with very long postzygapophyses.

This was more or less the high point for "T." valdensis. Not only was it the earliest European titanosaur (Le Loeuff 1993), but it provided evidence for a European origin of titanosaurs (Salgado and Calvo 1997). Things were all downhill from there. Authors began to describe it as an indeterminate titanosaur (Naish and Martill 2001; Wilson and Upchurch 2003; Upchurch et al. 2011). Then things got worse: it was downgraded to an indeterminate titanosauriform (D'Emic 2012; Mannion et al. 2013). The problem is that the features used to place "T." valdensis as a titanosaur are more widely distributed. For example, procoelous middle caudals are more widely distributed than just Titanosauria; the celebrated Giraffatitan also has them, for one. With just the existing specimens, there's no way to be certain if "T." valdensis is a true titanosaur or some other kind of titanosauriform. It should be noted, though, that there are definitely titanosaur fossils in the Wealden: two-and-a-bit middle caudals from the Wessex Formation of Brook, cataloged as NHMUK R5333 (Upchurch et al. 2011; D'Emic 2012; Mannion et al. 2013, 2019).

References

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

D'Emic, M. D., and J. A. Wilson. 2011. New remains attributable to the holotype of the sauropod dinosaur Neuquensaurus australis, with implications for saltasaurine systematics. Acta Paleontologica Polonica 56(1):61–73. 

D'Emic, M. D., P. D. Mannion, P. Upchurch, R. B. J. Benson, Q. Pang, and Z. Cheng. 2013. Osteology of Huabeisaurus allocotus (Sauropoda: Titanosauriformes) from the Upper Cretaceous of China. PLoS ONE 8(8):e69375. doi:10.1371/journal.pone.0069375.

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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.

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