Your Friends The Titanosaurs, part 36.2: Coming Attractions (Europe and South America)

Here we go: Apart from next month's wrap-up (and anything that gets named before then), this is the last time down the titanosaurian rabbit hole. We're going to visit the unnamed titanosaurs of Europe and South America, complementing the visit last time to the rest of the world. Some of the best examples are in this post, such as MAU-Pv-LI-595, MAU-Pv-AC-01, and MUCPv-1533, all from the vicinity of Rincón de los Sauces/La Invernada.

Note: This is another long one. On the other hand, it's split into many paragraph-sized chunks, so it's good for skipping around.

Your Friends The Titanosaurs, part 36.1: Coming Attractions (outside of Europe and South America)

Here we have a few of the many, many unnamed and/or undescribed titanosaurs. Some of their common habitats are abstracts, dissertations, press releases, and offhand comments in publications. Sometimes they're the subject of a paper describing some particular anatomical topic, or a geographic range extension. In other cases they're among five different morphotypes in a bonebed, and you can only hope that this pans out, because otherwise there's no negotiating with a von Huene puzzle. All the while you grit your teeth because you despair of ever seeing the really notable specimens published, especially so long as there's a theropod knuckle left to be described...

Anyway, this is not quite like "Coming Attractions in Dinosauria", which was based primarily on unnamed species with nicknames in long use. This is more like the original Addendum II in "The New Dinosaur Dictionary", except with specimen numbers and more references. It is certainly not exhaustive, and would take a lot more than a few weeks to make so. I am omitting embryonic forms (note that titanosaur nests have been found in several areas, including Argentina, India, and Spain), tracks, and named forms that need further description (Ampelosaurus, Futalognkosaurus, etc.). I've organized this by continent, and then by country; it turns out that if a country has terrestrial Cretaceous rocks, there is an excellent chance it has titanosaurs. Because of the sheer number of entries, I opted to split the post, with Europe and South America to come later.

I don't know if this will impress anyone, but I had a lot of fun writing this post.

Your Friends The Titanosaurs, part 35.5: Arrudatitan and Dzharatitanis?

Here's a quick update on some breaking news, with a new genus for an existing species and a putative rebbachisaur potentially hopping over from Diplodocoidea.

Arrudatitan maximus

This series has now gone on long enough that a species from one of the earliest entries has been transferred to a new genus. What we first came to know as Aeolosaurus maximus, third species of Aeolosaurus, is now Arrudatitan maximus (Silva et al. 2021). Confusingly, or conveniently, it remains A. maximus, but if you're facing a situation where using just one letter might cause confusion, the usual way to solve the problem is to go to two letters: Ar. maximus instead of the old Ae. maximus. The type specimen and provenance have not changed since Santucci and Arruda-Campos (2011) named Ae. maximus. For reference (repeating from the original entry), this species is based on a partial associated skeleton collected in 1997 and 1998 by staff of the Museu de Paleontologia de Monte Alto, Brazil, mentioned as early as Santucci and Bertini (2001). The skeleton, MPMA 12-0001-97, includes two partial posterior cervicals, fragments of several dorsals, parts of nine caudals, seven partial cervical ribs, twelve partial dorsal ribs, eight chevrons, a fragmentary scapula and arm bones, the left and partial right femur, the left ischium, and fragments. This specimen was found in sandstone at the top of the Adamantina Formation 12 km (7.5 mi) southwest of Monte Alto in São Paulo State. Croc and theropod teeth were found with the titanosaur, but no tooth marks were observed (Santucci and Arruda-Campos 2011). Brusatte et al. (2017) estimated the type individual as on the order of 14 to 15 m long (46 to 49 ft), but it seems to have grown since then: Silva et al. (2021) suggested it was 19 to 22 m long (62 to 72 ft), which is a bit more "maximus". The complete femur measures 1.55 m (5.09 ft) long, but is slender for its size (Santucci and Arruda-Campos 2011). The new genus name honors the now-deceased Professor Antonio Celso de Arruda Campos (Silva et al. 2021), one of the two authors of the original description. Originally the name would have translated as something like "greatest Aeolosaurus", but it would now be more akin to "Antonio Celso de Arruda Campos's greatest titan".

Future Arrudatitan maximus caudals, from Figure 1 in Martinelli et al. (2011). Scale bar is 5 cm (2 in). (License apparently CC, but iteration not stated.) If the second and third in sequence were articulated more closely at the centrum, more of the droop apparent farther back would be visible.

"Aeolosaurus" maximus had never been entirely comfortable in Aeolosaurus. Martinelli et al. (2011) regarded the caudal vertebrae of the type specimen (then "MPMA/without number") as more like those of other Brazilian aeolosaurinids than Aeolosaurus, a distinction observed quantitatively in Filippi et al. (2013): "A." maximus plotted with the great unwashed masses of aeolosaurinids rather than A. rionegrinus and A. colhuehuapensis in some details of placement of vertebral features. Bandeira et al. (2016), in their description of Austroposeidon magnificus, found A. maximus to plot rather distantly from the other two Aeolosaurus species in their phylogenetic analysis, and therefore referred to it as "A." maximus throughout the paper. The same result came up in Silva et al. (2019) and Hechenleitner et al. (2020) (and, it goes without saying, in Silva et al. 2021).

Given it hasn't been that long since the 2018 post, you might think that there hasn't been a lot of other news on this species. However, last year a paper was published devoted to its tail (Vidal et al. 2020). The articulated tail segment as discovered had a significant droop, as if Ar. maximus never got the memo about how dinosaurs didn't let their tails drag. This is not simply taphonomy, either; the vertebrae quite comfortably articulate in a downward curve. (This is also reportedly the only case of sauropod protony, as opposed to the well-known phenomenon of opisthotony in dinosaur skeletons leaving the neck and tail arched over the back.) Regrettably, at this point we only have a few vertebrae from one individual to work with.

(This also seems like as good a place as any to mention that the rock unit that produced Baurutitan britoi, Trigonosaurus pricei, and Uberabatitan ribeiroi has been differentiated from the Marília Formation as the Serra da Galga Formation, described in Soares et al. 2021 and alluded to in Silva et al. 2021.)

Dzharatitanis kingi

At the end of February 2021, Averianov and Sues published a description of a new sauropod, Dzharatitanis kingi, the first rebbachisaurid from Asia. At the end of April, in one of the faster turnarounds in memory, Lerzo et al. (2021) published a re-evaluation of the type and only known specimen that found it to be a titanosaur.

But we haven't been properly introduced yet. D. kingi is based on a well-preserved and nearly complete anterior caudal, USNM 538127 (U.S. National Museum of Natural History, Washington, D.C.). This fossil was found in 1997 during an URBAC (Uzbek/Russian/British/American/Canadian; think "Urbacodon") expedition in Uzbekistan. It came from the Turonian-age Bissekty Formation of Dzharakuduk in Navoiy Region. The genus name refers to Dzharakuduk and the species name honors the late Dr. Christopher King, giving us something like "Christopher King's Dzharakuduk titan" (Averianov and Sues 2021). USNM 538127 is one of a number of sauropod fossils from Upper Cretaceous rocks of central Asia, many of which are described in some detail in Sues et al. (2015) and Averianov and Sues (2017). There are two minor issues with the material that have held back greater understanding: the great majority of the specimens are teeth, and so far there isn't much in the way of associated specimens. USNM 538127 was obliquely referred to a couple of times before being unveiled in Sues et al. (2015) (Sues and Averianov 2004; Wilson 2005; you're not missing a whole lot if you don't go check them out, as the presence of USNM 538127 is only made clear by following Sues et al. 2015 back).

USNM 538127 in posterior (A), right lateral (B), and anterior (C) views. Scale bar 10 cm (4 in). Figure 1 in Averianov and Sues (2021). CC0 1.0.

USNM 538127 is kind of an odd piece, actually. It's notably short anterior-posterior for a titanosaur caudal, and notably short vertically for a rebbachisaur caudal. The centrum is advertised as opisthocoelous, but it's very modest about it. Lerzo et al. (2021) ran the rescored specimen in two data sets, including that used by Averianov and Sues (2021), with further tweaking based on whether or not the caudal is the first caudal or farther back. In all cases, they found it more likely to be a somphospondylan than a rebbachisaurid, well within Titanosauria in their first data set. The Averianov and Sues result is not illustrated, but stated to be a somphospondylan titanosauriform. This and some other information make me feel a slight twinge about diving in with a titanosaurian identification, though. Sues et al. (2015) and Averianov and Sues (2017) noted similarities between USNM 538127 and Baotianmansaurus henanensis and Dongyangosaurus sinensis, currently existing not quite in and not quite out of Titanosauria (Mannion et al. 2019). I have a sneaking suspicion that D. kingi may be something similar.

References

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.

Averianov, A., and H.-D. Sues. 2021. First rebbachisaurid sauropod dinosaur from Asia. PloS ONE 16(2), e0246620. doi:10.1371/journal.pone.0246620.

Bandeira, K. L. N., F. Medeiros Simbras, E. Batista 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.

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.

Filippi, L. S., A. G. Martinelli, and A. C. Garrido. 2013. Registro de un dinosaurio Aeolosaurini (Sauropoda, Titanosauria) en el Cretácico Superior (Formación Plottier) del norte de la provincia de Neuquén, Argentina, y comentarios sobre los Aeolosaurini Sudamericanos [Record of an Aeolosaurini dinosaur (Sauropoda, Titanosauria) in the Upper Cretaceous (Plottier Formation) of northern Neuquén Province, Argentina, and comments on the South American Aeolosaurini]. Revista Brasileira de Paleontologia 16(1):147–156.

Hechenleitner, E. M., L. Leuzinger, A. G. Martinelli, S. Rocher, L. E. Fiorelli, J. R. A. Taborda, and L. Salgado. 2020. Two Late Cretaceous sauropods reveal titanosaurian dispersal across South America. Communications Biology 3:article number 622. doi:10.1038/s42003-020-01338-w.

Lerzo, L. N., J. L. Carballido, and P. A. Gallina. 2021. Rebbachisaurid sauropods in Asia? A re-evaluation of the phylogenetic position of Dzharatitanis kingi from the Late Cretaceous of Uzbekistan. Publicación Electrónica de la Asociación Paleontológica Argentina 21(1):18–27. doi:10.5710//PEAPA.24.03.2021.389.

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.

Martinelli, A. G., D. Riff, and R. P. Lopes. 2011. Discussion about the occurrence of the genus Aeolosaurus Powell 1987 (Dinosauria, Titanosauria) in the Upper Cretaceous of Brazil. Gaea 7(1):34–40.

Santucci, R. M., and R. J. Bertini. 2001. Distribuição paleogeográfica e biocronológica dos titanossauros (Saurischia, Sauropoda) do Grupo Bauru, Cretáceo Superior do sudeste brasileiro. Revista Brasileira de Geociências 31(3):307–314.

Santucci, R. M., and A. C. de Arruda-Campos. 2011. A new sauropod (Macronaria, Titanosauria) from the Adamantina Formation, Bauru Group, Upper Cretaceous of Brazil and the phylogenetic relationships of Aeolosaurini. Zootaxa 3085:1–33.

Silva, J. C. G. Jr., T. S. Marinho, A. G. Martinelli, and M. C. Langer. 2019. Osteology and systematics of Uberabatitan ribeiroi (Dinosauria; Sauropoda): a Late Cretaceous titanosaur from Minas Gerais, Brazil. Zootaxa 4577(3):401–438. doi:10.11646/zootaxa.4577.3.1.

Silva, J. C. G. Jr., A. G. Martinelli, F. V. Iori, T. S. Marinho, E. M. Hechenleitner, and M. C. Langer. 2021. Reassessment of Aeolosaurus maximus, a titanosaur dinosaur from the Late Cretaceous of southeastern Brazil. Historical Biology advance online publication. doi:10.1080/08912963.2021.1920016.

Soares, M. V. T, G. Basilici, T. S. Marinho, A. G. Martinelli, A. Marconato, N. P. Mountney, L. Colombera, A. F. Mesquita, J. T. Vasquez, F. R. Abrantes Jr., and L. C. B. Ribeiro. 2021. Sedimentology of a distributive fluvial system: the Serra da Galga Formation, a new lithostratigraphic unit (Upper Cretaceous, Bauru Basin, Brazil). Geological Journal 56(2):951–975. doi:10.1002/gj.3987.

Sues, H.-D., and A. Averianov. 2004. 2004. Dinosaurs from the Upper Cretaceous (Turonian) of Dzharakuduk, Kyzylkum Desert, Uzbekistan. Journal of Vertebrate Paleontology 24(supplement to 3):119A–120A.

Sues, H.-D., A. Averianov, R. C. Ridgely, and L. M. Witmer. 2015. Titanosauria (Dinosauria, Sauropoda) from the Upper Cretaceous (Turonian) Bissekty Formation of Uzbekistan. Journal of Vertebrate Paleontology 35(1):e889145. doi:10.1080/02724634.2014.889145.

Vidal, L. D. S., P. V. L. G. da Costa Pereira, S. Tavares, S. L. Brusatte, L. P. Bergqvist, and C. R. dos Anjos Candeiro. 2020. Investigating the enigmatic Aeolosaurini clade: the caudal biomechanics of Aeolosaurus maximus (Aeolosaurini/Sauropoda) using the neutral pose method and the first case of protonic tail condition in Sauropoda. Historical Biology advance online publication. doi:10.1080/08912963.2020.1745791.

Wilson, J. A. 2005. Redescription of the Mongolian sauropod Nemegtosaurus mongoliensis Nowinski (Dinosauria: Saurischia) and comments on Late Cretaceous sauropod diversity. Journal of Systematic Palaeontology 3(3):283–318.

The Lost Fucoids of Edwin McKee

Okay, that's hyperbole. The fucoids were never lost, they were just overlooked.

Many of you have probably heard of Edwin "Eddie" Dinwiddie McKee, who was the park naturalist at Grand Canyon National Park from 1929 to 1940. He moved on to other positions, but the Canyon was never far behind him. By the end of his career he'd written monographs about almost all of the Paleozoic sedimentary formations of the canyon, missing only the Temple Butte Formation and Hermit Shale/Formation for a complete set. He doesn't seem to have focused much on the Precambrian sedimentary rocks, though. Maybe the logistics of access made them less appealing (you have to go all the way to the bottom to see them, after all). Maybe the relative paucity of non-microscopic fossils made them harder to interpret. Maybe he just wasn't interested in the Precambrian. We do, though, have an interesting assortment of Precambrian rocks collected and briefly described by McKee.

In May 1930, McKee paid a visit to the Chuar Creek/Lava Creek area of eastern Grand Canyon NP, returning with about two dozen specimens from the Dox Formation, part of the Mesoproterozoic Unkar Group (lower chunk of the park's famous Grand Canyon Supergroup). Several had intriguing spindle-shaped surficial pits and ridges. McKee gave a brief description of them in an article about "fucoides" at Grand Canyon (McKee 1932). "Fucoid" goes back to the 19th century proposition that what we now know as invertebrate burrow fossils were actually seaweed fossils. (Usually the plural is "fucoids", not "fucoides") By the early 1930s, this was pretty raggedy, as McKee acknowledged; he was using it as a term of convenience for "any structure of that general nature regardless of its origin." Among the "fucoides" he presented were spindle-shaped markings on two pieces of Dox Formation rock. A careful examination of the photo will reveal that the markings in the piece on the left are incised into the rock, and those on the right-hand piece project out of the rock. They're something like mud cracks, but are certainly not textbook cracks (McKee also notes that there *are* more typical mud cracks in the Dox).

"Grant" is noted NPS photographer George A. Grant. Somewhere there must be a higher-quality version of this photo, but I haven't found it yet (I've seen one of the next figure in the article, but not this one).

This is the last we hear of these Dox "fucoides" from McKee, and probably the last anyone who was not a Grand Canyon National Park museum curator thought about them until 2019, when we began the Grand Canyon National Park paleontological inventory. I was working on the Precambrian paleontology chapter, and I love the historical side of the science, so McKee's article was right up my alley. I included the photo in my draft, and one of the reviewers noted, quite accurately, that there was no scale. Well, I couldn't do much about it (there isn't even a "photo is 2/3rd actual size" or something like that, and my time machine is in the shop, plus I don't do temporal paradoxes). That fall, though, when I was at the park I had the opportunity to visit the museum collections, and there they were. I took them outside to mimic the original photo, which appears to have been taken in front of a step, retaining wall, or something along those lines (of course including a scale bar this time).

It's not quite the same, but you get the idea. The white object is a box I used to provide additional support for the piece on the left, which at some point had been broken in two with the two pieces given different specimen numbers (the new numbers have yellowish backgrounds, while the original numbers have white backgrounds; if you compare this to the original photo, you can see the same spots).

While I was working, a number of other paleontologists were also visiting the collections as part of our National Fossil Day event. Spencer Lucas observed that the specimens looked a lot like microbially induced sedimentary structures (MISS), and asked about writing a short paper about them, to which I agreed (Tweet and Lucas 2021). The specimens themselves turned out to be more complex than is apparent from either photo. They are actually part and counterpart: in the color photo above, the large gray redox spots on the margins of the two pieces are the same spot, and the concave and convex features fit quite nicely when the pieces are lined up properly. Furthermore, there is another piece that belongs to this group, not included in the original photo (perhaps it didn't fit the composition?).

Here's a group shot, with the redox spots lined up and the previously omitted piece included.

The matching surfaces are laced with spindle-shaped features, convex in the upper row in the previous photo, concave in the lower row. Most of them are around 20 to 30 mm long (a little more or less than an inch), about 5 mm across, and with less than 5 mm of relief. A gentle, roughly longitudinal warp is most evident in the two left pieces, which might be a ripple or something similar but is heavily obscured. Flipping them over revealed additional but different features, a combination of blebs and long stringy features.

Figure 5 in Tweet and Lucas (2021). The black arrows in A point to two potential generations of ripples, and the white arrow points to the edge of a bed. B, the lower row in the preceding photo, is particularly marked by equant convex blebs and long stringy features, but there are a few on A as well.

The spindle-shaped features on the part-counterpart surfaces are shrinkage cracks, but as noted they aren't your typical mud cracks. Mud and coarser-grained sediments respond to shrinkage differently; mud grains stick to each other until something gives and a fissure forms, but sand grains slide apart from each other and do not form cracks unless something else interferes. That "something else" can be abiotic or, more frequently, biotic, such as a sticky microbial mat (Seilacher 1999). Something that is counterintuitive about microbially mediated cracks is that they are often preserved as positive features (Eriksson et al. 2007): mat and substrate contract and fissure, sediment fills fissure (either from above or from below due to environmental pressure), mat decays, and presto!—positive cracks! The long linear features in the photo above are similar to a different kind of MISS, in this case rolled-up mat fragments (Donaldson 1967; Eriksson et al. 2007).

This is more of a preliminary assessment than a definitive study. We don't have much to go on for the original geologic context, for one thing, and for another, if you really want to cover all of your bases, you need to take thin sections; MISS and inorganic features can be easily confused. Regardless, the features are highly suggestive of MISS, and the Dox Formation is already known to have stromatolites in other beds (Stevenson and Beus 1982). The Precambrian of the Grand Canyon has produced many features that were originally reported as burrow-like or "fucoidal", but most non-stromatolite features were dismissed as inorganic in the 1960s and 1970s, a couple of decades before the study of MISS took off. I would not be surprised if new study of the various formations of the Grand Canyon Supergroup, attuned to the possibility of MISS, were to uncover them in intervals previously regarded as barren of fossils.

References

Donaldson, J. A. 1967. Precambrian vermiform structures: a new interpretation. Canadian Journal of Earth Sciences 4:1273–1276.

Eriksson, P. G., H. Porada, S. Banerjee, E. Bopuougri, S. Sarkar, and A. J. Bumby. 2007. Mat-destruction features. Pages 76–105 in J. Schieber, P. K. Bose, P. G. Eriksson, S. Banerjee, S. Sarkar, O. Catuneanu, and W. Altermann, editors. Atlas of microbial mat Features preserved within the clastic rock record. Elsevier, Amsterdam.

McKee, E. D. 1932. Some fucoides from Grand Canyon. Grand Canyon Nature Notes 7(8):77–81.

Seilacher, A. 1999. Biomat-related lifestyles in the Precambrian. Palaios 14:86–93.

Stevenson, G. M. and S. S. Beus. 1982. Stratigraphy and depositional setting of the upper Precambrian Dox Formation in Grand Canyon. Geological Society of America Bulletin 93:163–173.

Tweet, J. S., and S. G. Lucas. 2021. Re-evaluation of Precambrian “fucoids,” microbially induced sedimentary structures in the Proterozoic Dox Formation, Grand Canyon National Park, Arizona. New Mexico Museum of Natural History and Science Bulletin 82:427–435.