Your Friends The Titanosaurs, part 12: Futalognkosaurus, Gondwanatitan, and Hypselosaurus

For today's entry in the ongoing series, we have a big sauropod that used to be even bigger, a small sauropod that appears to have been lost in a fire, and a small sauropod of historical interest which is a bit of a humbug.

Futalognkosaurus dukei

Futalognkosaurus dukei burst onto the scene over a decade ago as the latest, greatest, and largest sauropod. Like the other latest, greatest, and largest sauropods, it has since deflated somewhat, and Argentinosaurus huinculensis remains standing off to the side with a look of detached amusement playing on its face (a difficult thing for a sauropod to pull off). Nevertheless, it is among the best represented of the big titanosaurs, even if not everything that is known has been described.

Futalognkosaurus dukei being big and moodily lit at the Royal Ontario Museum. Photo taken by Steve Depolo, found on Wikimedia Commons.

F. dukei first came to light in March 2000, in the form of a cervical found on the north shore of  Barreales Lake in rocks of the Portezuelo Formation, Neuquén Province, Argentina. We visited the same formation and general area with Baalsaurus. The type locality has yielded a diverse assemblage including fossils of conifers, angiosperms,bivalves, fish, turtles, crocs, pterosaurs, the theropods Megaraptor and Unenlagia, and iguanodonts. The site is interpreted as within the floodplain of a meandering river (Calvo et al. 2007a). F. dukei is based on MUCPv-323 (CePaLB-Universidad del Comahue, Neuquén), a partial skeleton including 14 cervicals, 10 dorsals, the sacrum, an anterior caudal, ribs, both ilia, and the right pubis and ischium (Calvo et al. 2007a). There are also additional specimens which have yet to be described or figured in any detail. The supplementary information for the Notocolossus description (González-Riga et al. 2016) reported a femur 1,910 mm long (75.2 inches) with a conference abstract as source (Calvo 2014), and attributed it to the type specimen, which is an interesting detail.

The type material of F. dukei as illustrated in Calvo et al. (2007a) (Figure 2; see for full caption). CC-BY-4.0.

The name comes from the Mapuche "futa" for "giant" and "lognko" for "chief", with the species name honoring the Duke Energy Argentina Company, which sponsored the 2002–2003 excavation (Calvo et al. 2007a). This gives us "Duke Energy Argentina Company's giant chief lizard". Counterintuitively, the name is pronounced as if it was spelled "Futalongkosaurus", which may well be responsible for early reports of a new dinosaur of that name. (Sometimes I suspect that the people responsible for transliterations are slightly deranged.)

Anatomically, F. dukei is particularly notable for its neck. The enormous neck of the type specimen helped to show that titanosaurs were not limited to the relatively scrawny necks of saltasaurs. The cervicals are elongate and feature tall triangular ("sail-like") neural spines (Calvo et al. 2007b). Titanosaurs were not slim in the hips, and the type of F. dukei was blessed with a breadth that is truly impressive. (Don't forget that the rib cage would have been even wider in a big herbivore like this, which thrived on volume rather than quality.) The pubis is also a large, robust bone. The ?first caudal seems unusually beefy based on the figures. 

F. dukei started off in print as 32 to 34 m long (105 to 112 ft) (Calvo et al. 2007a), but was revised down to 26 m (85 m), based on an approximate 13 m (43 ft) pre-caudal length and a tail estimated as about the same length (Calvo et al. 2008), so a shorter tail could knock a few more meters off of that figure. González-Riga et al. (2016) used the mystery femur to estimate a mass just above 38 metric tons (about 42 US tons).

F. dukei also spawned the clade Lognkosauria, originally designated for it and Mendozasaurus (Calvo et al. 2007a). The Futalognkosaurus/Mendozasaurus relationship has proven to be durable, because F. dukei and Mendozasaurus almost always show up as sister taxa or adjacent to each other when both are included in phylogenetic analyses. Other lognkosaurs have proven harder to pin down. At times most of the other giant titanosaurs end up pulled into to Lognkosauria (e.g. González Riga et al. 2018 with Argentinosaurus, Notocolossus, Patagotitan, and Puertasaurus), but in others it's just the two original lognkosaurs, or the two don't form a meaningful clade to the exclusion of most other titanosaurs.

Gondwanatitan faustoi

As related by Kellner and Azevedo (1999), the specimen that became the basis for Gondwanatitan faustoi was found by Yoshitoshi Myzobuchi on his farm in the Álvares Machado region of São Paulo, Brazil, and was excavated over the next few years by Dr. Fausto Luiz de Souza Cunha and his crew from the Museu Nacional/Universidade Federal do Rio de Janeiro. It was briefly noted at the time (Cunha and Suarez 1985), but was not completely prepared or studied until the late 1990s. The type specimen is/was MN 4111-V (Museu Nacional/UFRJ). "Museu Nacional" may be more familiar to you as the National Museum of Brazil, which unfortunately means the specimen was there for the fire, and to date I haven't seen any indications that it's turned up since then.

At the time, MN 4111-V was considered the most complete dinosaur specimen from Brazil. It consisted of an associated skeleton including "two partial cervicals, seven dorsals, six sacrals, twenty-four caudals (some articulated), and four unidentified vertebrae; proximal part of left scapula, left ilium (incomplete), middle portion of both pubis, both ischia (incomplete), both humeri, both tibiae, several remains of ribs, and several unidentified fragments" (Kellner and Azevedo 1999). The genus name is pretty self-explanatory if you've been at this for a while: "Gondwana" for the southern supercontinent plus "titan". Faustoi honors Dr. Cunha, giving us "Fausto Luiz de Souza Cunha's Gondwana titan". The "titan" part is a bit of an honorific itself, because the type specimen was only about 6 to 7 m long (20 to 23 ft). More of the specimen was originally preserved than could be recovered, due to erosion. It was found in a fluvial sequence of the Adamantina Formation (Bauru Group) that also yielded croc remains, with more croc and turtle fossils found higher in section (Kellner and Azevedo 1999).

The type specimen of G. faustoi, from Kellner and Campos (2000:Figure 10). CC-BY-4.0.

Anatomically, G. faustoi has been noted for the heart-shaped posterior articular surfaces of its caudals. The caudals also do the Aeolosaurus thing where the neural arches are on the leading end of the caudals. The humeri are relatively long and slender with well-developed deltopectoral crests.

In the years since its description, the main point of interest about G. faustoi has been whether or not it should be Aeolosaurus faustoi. Kellner and Azevedo (1999) recognized that G. faustoi was most similar to Aeolosaurus of all the titanosaurs then known. Since they do appear to be close relatives, the question in some ways boils down to the sensitivity of your genericometer. Be that as it may, the synonymy was advocated in Bertini et al. (2000), Santucci and Bertini (2001), and Santucci (2002). Candeiro (2010) listed several differences regarded as significant at the generic level, such as the heart-shaped caudal articular surfaces in G. faustoi, other details of the caudal anatomy, the configuration of the ischia, and a more slender humerus in Aeolosaurus. This was accepted by Martinelli et al. (2011) in their review of aeolosaur material, and in general G. faustoi has been recognized as a distinct genus. G. faustoi does tend to show up as a sister taxon of Aeolosaurus or otherwise closely related in a fairly small clade (Bandeira et al. 2016; França et al. 2016; Gorscak et al. 2017; Díez Díaz et al. 2018; Sallam et al. 2018; Gorscak and O'Connor 2019); Overosaurus and Trigonosaurus seem to be the most frequent sidekicks.

Hypselosaurus priscus

Hypselosaurus priscus is not really the kind of thing you want to see staring you down from your blog-post-in-preparation. There are numerous references, most of which are in a language I don't happen to read (French), and in the long run they don't matter because H. priscus is a classic example of a species based on scrappy remains that ended up in wide circulation for decades because it was there. Very existential, I'll give it that. Today, there are several different titanosaur species known from much better remains from the Upper Cretaceous of France, and there is no particular reason to break out H. priscus except as a historical thing.

H. priscus has pride of priority as the first name that can be ascribed to Titanosauria, dating back to 1869 (Matheron 1869; yes, there's Aepisaurus, but no one's put up an argument for it being a titanosaur outside of vague guilt-by-association). Titanosaurs not being a thing in 1869, and sauropods barely known at all, Matheron interpreted his new genus and species as a giant crocodile-like aquatic animal. The fossils themselves went back even farther; Matheron first mentioned them as far back as 1846, putting us close to the birth of Dinosauria. The bones he described in 1869 included: a damaged and incomplete left femur estimated as on the order of 80 cm long (24 in), not particularly impressive these days but more substantial then; a partial tibia; a partial fibula; and two caudals. They were collected from Rognac in the Aix Basin of Provence, southeastern France (Le Loeuff 1993). Per Le Loeuff (1993), these fossils are missing from the Muséum d'Historie Naturelle of Marseilles.

The sum total of Hypselosaurus priscus, from Matheron (1869).

Over the next few decades, there was a steady accretion of miscellaneous titanosaur remains from France and eventually Spain and Romania to H. priscus; the curious reader can follow this to some extent in Le Loeuff (1993) and Glut (1997; see if you can pick out what became Ampelosaurus). The most substantial report along these lines was Lapparent (1947), which split known French titanosaur remains between Hypselosaurus and Titanosaurus based on size. (Everyone was doing it at the time.) Being based on three partial limb bones and two caudals which all disappear is not healthy for long-term scientific survival. Le Loeuff (1993), in a review of European titanosaurs, regarded H. priscus as a dubious titanosaur, and no one seems to have complained much about this turn of events.

Despite all of the other bits and pieces assigned to it over the years, H. priscus has never been widely known for its bones. Its major claim to fame is the associated eggs and eggshells first mentioned by Matheron (1869), which came to be recognized as the first reported non-avian dinosaur egg material. In the absence of embryonic remains (let alone diagnostic adult remains of H. priscus), there is no firm reason to assign any of the egg material to H. priscus.

References

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