Your Friends The Titanosaurs, part 35: Part-Time Titanosaurs, or: The Next Best Thing

Following on the previous post in the series, this post takes a look at the taxa that hang out near the base of Titanosauria, usually outside but sometimes slipping under the velvet rope held by Andesaurus. Usually on these occasions they don't really get under that rope, per se, but are wrapped up in a massive polytomy that also includes Andesaurus (e.g., González Riga et al. 2018; Averianov and Efimov 2018; Hechenleitner et al. 2019; Rubilar-Rogers et al. 2021). Alternatively, they form a bunch of little clades at the base of Titanosauria within one larger clade including Andesaurus (e.g., Sallam et al. 2018; Gorscak and O'Connor 2019; some results in Mannion et al. 2019), which I guess in principle would resurrect Andesauridae, but no one has seemed excited about the proposition. I still say that Andesaurus has done about as well as possible marking the boundary of the arbitrary human construct Titanosauria, but admittedly it does sometimes indulge an appetite for polytomies.

Paleozoic Taxa of the St. Croix Valley

Back when I was working on the Saint Croix National Scenic Riverway project, I'd compiled a spreadsheet of all of the fossil genera and species that had been reported from the rocks exposed along the valley. There had been some talk of spinning it off as a separate thing, but that never happened, so I played with the idea of posting it here. I then forgot about it until recently looking through the backlog of half-formed ideas. The spreadsheet itself was all ready to go, so I figured "why not?"

It's pretty simple; a column of numbers so it can be sorted back to the original organization when I'm working, a column for the genus/species, a column for the broad classification, twelve columns for the formations (go here for a refresher; the names are abbreviated for space, but each one has a note providing the full name), a column for references (defined on the "References" tab), and a column for additional notes. If a given species is present in a particular formation, the corresponding cell is marked "Y" and filled blue; if there's some question, the cell is marked "?" and filled yellow. If it's not present, there's a dash and no color fill. To check it out, you can enter here. I would not be surprised if there has been some oversplitting, if for no other reason than the challenges of preservation (we're dealing with a lot of natural molds and casts of partial trilobites in sandstone; fragility and preservation fidelity leave something to be desired).

It's worth mentioning that there is a document that covers some of the same ground, Raasch (1950). In one sense it's more narrowly focused, on Cambrian trilobite biostratigraphy, but in another it's more diffuse, with a larger area of interest.

References

Raasch, G. O. 1950. Zonal range of Croixan trilobite genera in the upper Mississippi Valley. Cambrian Subcommittee Memorandum No. V. Illinois State Geological Survey, Urbana, Illinois.

Rugalichnus

Here we have a textbook example of Rugalichnus. This particular example was observed in the Wupatki Member of the Moenkopi Formation at Wupatki National Monument.

Click to embiggen; it's the labyrinthine surficial feature.

That's all well and good, but what is Rugalichnus?

First off, it's not Rivularites. (For some reason Rivularites has attached itself to my mental conception of features like this, but that's not important.)

Rugalichnus is a microbially induced sedimentary structure (MISS), which is a reasonably self-explanatory name: it's a sedimentary structure that resulted from the influence of a microbial mat. This means it has a metaphorical foot both in "trace fossil" and in "sedimentary structure". Another way of thinking about it is as a cousin to stromatolites. It isn't stacked and occurs in clastic rocks rather than carbonates, but it shares the same principle of a sticky microbial mat influencing the preservation of sedimentary features.

Features similar to Rugalichnus have been reported for more than a century. Charles Doolittle Walcott (1914) named the ur-example Kinneyia simulans from Precambrian rocks in Montana, thinking it was an algal fossil. It became a topic of controversy for decades, culminating in the "genus" and "species" turning out to be an inorganic dud (Davies et al. 2016; Stimson et al. 2017). If you look at the figure below, you might think you're seeing a bedding plane, like the object in my photo. However, it isn't; it's actually an artifact of weathering. Stimson et al. (2017) opted to coin the new name Rugalichnus matthewi for the MISS features that people had been calling "Kinneyia" (and yes, the naming of MISS is a can of worms unto itself).

Kinneyia simulans. Plate II, Figure 3 in Walcott (1914).

There are many varieties of MISS, reflecting the many ways a microbial mat can interact with its sedimentary substrate. Rugalichnus is known from storm wave deposits, indicating it formed after storms (Herminghaus et al. 2016). When Rugalichnus (as Kinneyia) was first interpreted as a MISS, it was thought to have formed beneath an active microbial mat (see for example Porada et al. 2008 and Thomas et al. 2013). Mariotti et al. (2014) proposed instead that the ridges and troughs resulted from rolling mat fragments and loose mat ends. Herminghaus et al. (2016) conceded that there were circumstances that could produce the wrinkle structures using the Mariotti et al. model, but preferred their own hydrodynamic instability model from Thomas et al. (2013). Given that there are abiotic features that look very similar (Davies et al. 2016), there's certainly no reason to assume that all Rugalichnus-like wrinkles formed the same way. Me, I don't have a horse in this race; I just find the structure interesting.

References

Davies, N. S., A. G. Liu, M. R. Gibling, and R. F. Miller. 2016. Resolving MISS conceptions and misconceptions: A geological approach to sedimentary surface textures by microbial and abiotic processes. Earth-Science Reviews 150:210–246.

Herminghaus, S., K. R. Thomas, S. Aliaskarisohi, H. Porada, and L. Goehring. 2016. Kinneyia: a flow-induced anisotropic fossil pattern from ancient microbial mats. Frontiers in Materials 3. doi:https://doi.org/10.3389/fmats.2016.00030.

Mariotti, G., S. B. Pruss, J. T. Perron, and T. Bosak. 2014. Microbial shaping of sedimentary wrinkle structures. Nature Geoscience 7:736–740.

Porada, H., J. Ghergut, and E. H. Bouougri. 2008. Kinneyia-type wrinkle structures—critical review and model of formation. PALAIOS 23:65–77.

Stimson, M. R., R. F. Miller, R. A. MacRae, and S. J. Hinds. 2017. An ichnotaxonomic approach to microbially induced sedimentary structures from the Saint John Group of New Brunswick: why comparison to Kinneyia Walcott 1914 must be abandoned. Ichnos 24(4):291–316. doi:10.1080/10420940.2017.1294590.

Thomas, K., S. Herminghaus, H. Porada, and L. Goehring. 2013. Formation of Kinneyia via shear-induced instabilities in microbial mats. Philosophical Transactions of the Royal Society A 371(2004):20120362.

Walcott, C. D. 1914. Cambrian geology and paleontology III, no. 2. Pre-Precambrian Algonkian algal flora. Smithsonian Miscellaneous Collections 64:77–156.

Your Friends The Titanosaurs, part 34: Titanosaurs of Yesterday

There are a few taxa of interest that haven't yet been covered. They include: 1) "historical titanosaurs", the kind you might stumble across in a 1980s dinosaur dictionary; 2) poorly known species regarded as titanosaurs mostly on the circumstantial evidence of time and place, without the anatomical evidence to back up a classification; 3) species that have turned up in Titanosauria once or twice during the cladistic era (mid-1990s to the present) but are not currently or generally regarded as titanosaurs; and 4) species that appear to have been near Titanosauria and sometimes hop the line in analyses, but usually are found outside. This post is for the first three varieties. We've got 15 in the queue, so as you can image I'm not going to go into a great deal of detail.

Curiously, most of McIntosh's "Sauropoda incertae sedis" from the first edition of The Dinosauria show up on this page: "Pelorosaurus" becklesii (=Haestasaurus), Mongolosaurus, Austrosaurus, and Aepysaurus (=Aepisaurus), plus a shout-out to "Apatosaurus" minimus. The only ones not here are "Morosaurus" agilis (now described as a rebbachisaurid [2021/04/02: no, dicraeosaurid; do this long enough and they all run together], Smitanosaurus), and Campylodoniscus, which was previously featured. This says something about quasi-titanosaurs, but I'm not sure what. The taxa also skew old, with many of Early Cretaceous or even Late Jurassic age, suggesting it's harder to get a handle on putative early titanosaurs. Unsurprisingly, many of them are dubious, albeit in all kinds of ways: from garden-variety causes like too little material, to "unavailable for study due to being destroyed by monsoons", to "the osteoderms turned out to be ribs", to "the original describer thought a pile of caudals from several sites separated by miles belonged to one individual", to "actually filled mollusk borings".

As a reminder, because the terms come up several times, Titanosauriformes is the clade made up of the most recent common ancestor of Brachiosaurus and Saltasaurus plus all of its descendants, and Somphospondyli is the clade made up of all sauropods more closely related to Saltasaurus than to Brachiosaurus.

Your Friends The Titanosaurs, part 33.5: Arackar and Ninjatitan

Two titanosaurs were announced within a few days of each other at the end of February–beginning of March: Arackar licanantay and Ninjatitan zapatai. They're both from the South American stronghold of the group, but at opposite ends of the titanosaurian geologic time frame. Neither is currently known from a great deal of material. Will these be the last species to sneak in under the line before the end of this series?

Arackar licanantay

Back in the entry for Atacamatitan chilensis, I mentioned that A. chilensis was based on the second-best titanosaur specimen from Chile, with the best specimen being undescribed at that time. That specimen, SNGM-1 (Servicio Nacional de Geología y Minería, Santiago, Chile), has now received the name Arackar licanantay (Rubilar-Rogers et al. 2021), although not without some controversy over less-than-helpful aspects of how the preprint has been presented.

Genus and species: Arackar licanantay is translated as "in reference to 'bones of the Atacamenians' in Kunza, the language of the original indigenous people of the Atacama region" (Rubilar-Rogers et al. 2021), but the exact breakdown of the genus and species names is not specified. [2021/03/19: a breakdown by Ben Creisler can be found here. Short answer: "arackar" for bones, "Lican Antay" for the Atacamenian people.]

Citation: Rubilar-Rogers, D., A. O.Vargas, B. Gonzalez Riga, S. Soto-Acuña, J. Alarcón-Muñoz, J. Iriarte-Díaz, C. Arévalo, and C. S. Gutstein. 2021. Arackar licanantay gen. et sp. nov. a new lithostrotian (Dinosauria, Sauropoda) from the Upper Cretaceous of the Atacama Region, northern Chile. Cretaceous Research. doi:10.1016/j.cretres.2021.104802.

Stratigraphy and Geography: The type and only known specimen of A. licanantay was discovered in 1993 at Quebrada La Higuera, approximately 75 km (47 mi) south of Copipaó in Atacama Region, northern Chile. The site is in the lower to middle Hornitos Formation, described as Campanian–Maastrichtian in age. The type specimen was found in lacustrine mudstone within a lacustrine mudstone–fluvial sandstone sequence (Rubilar-Rogers et al. 2021).

Holotype: SNGM-1/1–23, consisting of two cervical centra, two anterior and one posterior dorsal neural arch, three dorsal centra, the right humerus, the left ischium, the left femur, and fragments, found over an area of about two square meters (22 square feet). These bones are well-preserved and represent a partially grown individual (Rubilar-Rogers et al. 2021).

A. licanantay is one of a small number of titanosaurs known from the Pacific side of South America, joining Atacamatitan chilensis and Yamanasaurus lojaensis as the only named species, and is the most completely represented of this group. Most of the diagnostic features pertain to the various laminae of the vertebrae; perhaps the most obvious feature from a distance is the strong posterior angle of the dorsal neural spines. The limb bones are on the gracile side. The humerus, at 590 mm long (23.2 in), is about 4/5ths the length of the femur, at 740 mm (29.1 in) (Rubilar-Rogers et al. 2021). Rubilar-Rogers et al. (2021) ran a phylogenetic analysis and found their new species to group with an Indo–Madagascar group consisting of Isisaurus colberti and Rapetosaurus krausei, interestingly enough.

Ninjatitan zapatai

Our next guest was announced a few days before A. licanantay. Not only does it come with a memorable name, it is also a contestant in the ongoing "world's oldest titanosaur" competition.

Genus and species: Ninjatitan zapatai contains references to two people. The genus name honors paleontologist Sebastián Apesteguía by his nickname "Ninja"; if you've been looking at the citations in this titanosaur series, you'll have noticed his name numerous times. The species name honors Rogelio Zapata, a technician at the Museo Municipal Ernesto Bachman, and by extension the work of the rest of the museum's technician team (Gallina et al. 2021). The name might be translated loosely as something like "titan of Sebastián Apesteguía and Rogelio Zapata".

Citation: Gallina, P. A., J. I. Canale, and J. L. Carballido. 2021. The earliest known titanosaur sauropod dinosaur. Ameghiniana 58(1):35–51. doi:10.5710/AMGH.20.08.2020.3376.

Stratigraphy and Geography: Lower Cretaceous Bajada Colorada Formation (late Berriasian–Valanginian age), Bajada Colorada locality, approximately 40 km (24 mi) southwest of Picún Leufú in Neuquén Province, Argentina. We visited this locality a couple of years ago for Bajadasaurus pronuspinax. In this case, the bones came from a level 4 m (13 ft) below the previously described specimens (Gallina et al. 2021).

Holotype: MMCh-Pv228 (Museo Municipal Ernesto Bachmann, Villa el Chocón, Neuquén), which includes a partial anterior/middle dorsal, a middle dorsal centrum, an anterior caudal centrum with a bit of neural arch (first caudal?), the left scapula, distal femur, and nearly complete left fibula. The bones came from an area 6 m square (about 65 square feet, which might sound like a lot but is basically 8 feet by 8 feet) and are regarded as representing one individual (Gallina et al. 2021).

We can tell that N. zapatai is not a diplodocoid and thus is neither Bajadasaurus nor Leinkupal, the other named sauropod from the Bajada Colorada Formation. Three features indicate it is a titanosaurian: a slightly procoelous caudal, pneumatization of the caudal's neural arch, and the position of a process on the scapula (Gallina et al. 2021). (If the caudal in Figure 3.2 seems backwards, note that it's in right-lateral view rather than left-lateral view [threw me for a moment before I read the caption].) When analyzed phylogenetically, it came out as either just within Titanosauria or nested in Colossosauria, in fact within Lognkosauria (Gallina et al. 2021). N. zapatai as the earliest named titanosaur would push the origin of the group at least near the Jurassic–Cretaceous boundary. We also get the interesting coincidental association of the most recent named diplodocid (Leinkupal) with the earliest named titanosaur.

References

Gallina, P. A., J. I. Canale, and J. L. Carballido. 2021. The earliest known titanosaur sauropod dinosaur. Ameghiniana 58(1):35–51. doi:10.5710/AMGH.20.08.2020.3376.

Rubilar-Rogers, D., A. O.Vargas, B. Gonzalez Riga, S. Soto-Acuña, J. Alarcón-Muñoz, J. Iriarte-Díaz, C. Arévalo, and C. S. Gutstein. 2021. Arackar licanantay gen. et sp. nov. a new lithostrotian (Dinosauria, Sauropoda) from the Upper Cretaceous of the Atacama Region, northern Chile. Cretaceous Research. doi:10.1016/j.cretres.2021.104802.

Proboscidean update: the Williamsburg mammoth (or mastodon)

Leaving titanosaurs aside for the moment...

A couple of times now, I've featured inventories of National Park Service proboscidean fossils: mammoths, mastodons, and so forth. One of the records that's been stuck as questionable is an 1811 report from the area of Colonial National Historical Park. To quote from the most recent published assessment, in Mead et al. (2020):

“The Williamsburg-area mastodon was first reported in 1811 (Anonymous 1811). The details vary from report to report, but apparently the bones were found 10 km (6 mi) south (Anonymous 1811) or east (Mitchill 1818) of Williamsburg on the south bank of the York River. It is unclear where the former location would be, but the latter is potentially within COLO [Colonial National Historical Park], in the vicinity of Bellefield Plantation and the mouth of Indian Field Creek. Anonymous (1811) reported that the site was a few yards within high water near the home of Gawin Corbin. The fossils include 2 tusks, 2 vertebrae, 1 pelvis, 1 femur, and partial mandibles with 7 associated teeth (Mitchill 1818). Given the presence of molars, it is surprising that Mitchill (1818) identified the specimens as mammoth, yet Hay (1923) reported them as a mastodon (Mammut). Hay (1923) reported that the bones were probably destroyed in the 1859 fire at the College of William and Mary. Clark and Miller (1912) refer this specimen to the Pleistocene of the Talbot Formation (a now-obsolete name)."

I and others have made attempts over the past few years to determine who the Gavin Corbin in question was and where his property was located, most recently as part of the Colonial National Historical Park paleontological inventory currently being reviewed. The primary issue has been the numerous Corbins who have lived in this region, including multiple Gawin Corbins. In such a case, sometimes you have to trust in serendipity, and I can now state that I'm practically certain the answer is at hand. The man in question is Gawin Lane Corbin (1778–1821), and the property is the “Kings Creek” plantation, now within the U.S. Navy's Cheatham Annex just north of the Colonial Parkway.

This was the kind of thing where it was helpful to have some experience in genealogical research. It wasn't enough to have a good candidate for the name; there also had to be a way to track the location. In this case, "Kings Creek" has a lengthy history, beginning as "Utimaria" in 1630 and passing through various hands until being sold to Corbin's father in 1790 (Tyler 1894; Anonymous 1913). Later the area was known as Penniman, and eventually the Navy's Cheatham Annex. Importantly for us, we also know that the Ringfield and Bellefield (or Bellfield, or Belfield) plantations were active in the same time frame as the fossil discovery, on what is now the NPS side of Kings (or King’s, or King) Creek. With this knowledge, we can be certain than any mammoth or mastodon found near the home of Gawin Corbin on the York River shore was found in what would now be part of the Cheatham Annex, and therefore near but not within the historical park. (On the other hand, if anyone from the Annex is reading this, it looks like there's a mammoth or mastodon in your history.)

Presumably Corbin had some idea of the significance of the find for it to have been collected in the first place. He was certainly in a position to have been exposed to discussion of such fossils, having social standing and a college education (William & Mary alum; Anonymous 1922) at a time when fossils of mammoths and mastodons held an unusual fascination beyond their scientific value.

Near the mouth of King's Creek, looking north toward Penniman Spit.

References

Anonymous. 1811. Curious discovery [elephant bones from York River, Williamsburg, Virginia]. Philadelphia Repertory 2:87–88.

Anonymous. 1913. Notes from the records of York County. William and Mary College Quarterly Historical Magazine 22(2):73–89.

Anonymous. 1922. The Corbin Family (continued). The Virginia Magazine of History and Biography 30(4):403–407.

Clark, W. B., and B. L. Miller. 1912. The physiography and geology of the Coastal Plain province of Virginia. Virginia Geological Survey Bulletin 4:13–222.

Hay, O. P. 1923. The Pleistocene of North America and its vertebrated animals from the states east of the Mississippi River and from the Canadian provinces east of longitude 95 degrees. Carnegie Institution of Washington, Washington, D.C. Publication 322.

Mead, J. I., J. S. Tweet, V. L. Santucci, J. T. Rasic, and S. E. Holte. 2020. Proboscideans from US National Park Service lands. Eastern Paleontologist 6:1–48.

Mitchill, S. L. 1818. Observations on the geology of North America; illustrated by the description of various organic remains found in that part of the World. Pages 319–431 in G. Cuvier. Essay on the theory of the Earth, with mineralogical notes, and an account of Cuvier’s geological discoveries, by Professor Jameson. Kirk and Mercein, New York, New York.

Tyler, L. G. 1894. Notes by the editor. The William and Mary Quarterly 2(4):230–236.

Your Friends The Titanosaurs, part 33.3: Alamosaurus of Texas and Mexico?

Having visited New Mexico and Utah (with side trips to Wyoming and Montana), we come now to more southerly Alamosaurus, concentrated in the Big Bend region of Texas. After a slow start Big Bend titanosaurs have attracted a lot of study, with numerous publications over the past quarter-century. There are also some less well-documents reports from elsewhere in Texas and across the border in Chihuahua, Mexico. We also have a little more on the question of whether or not we're dealing with just one species, and Tyrannosaurus makes yet another cameo.

This post marks the end of the main part of "Your Friends The Titanosaurs" (I can hardly believe it!) although we do have a few things to follow up with before calling it closed.

A view of the Perot Museum of Natural History mount (Dallas, Texas) emphasizing the neck. The original neck vertebrae are visible near floor level behind the torso of the mount. In the lower right a Tyrannosaurus rex has second thoughts. Photo by Louis Tanner from Garland, TX, USA, CC-BY-2.0, via Wikimedia Commons.