Saturday, February 20, 2021

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.

Saturday, February 13, 2021

Your Friends The Titanosaurs, part 33.2: Alamosaurus of Utah and points north?

We head north into Utah this time for the next major discoveries of Alamosaurus. Unlike Alamosaurus of the San Juan Basin or the Big Bend area of Texas (as we'll see next time), Alamosaurus sanjuanensis from the North Horn Formation of Utah has been more or less represented by one specimen, although others are known. Fortunately, that one specimen has been very informative in its own right. In addition to Utah, we have sketchy references to finds in Wyoming and Montana to deal with, plus a couple of incomplete threads from the San Juan Basin to tie up.

Saturday, February 6, 2021

Your Friends The Titanosaurs, part 33.1: Alamosaurus of New Mexico

The time has come to deal with the one and only named North American titanosaur, the redoubtable Alamosaurus sanjuanensis. You may remember that in the very first post of this series, I mentioned I was skipping Alamosaurus for the moment. I was waiting on it because I was concerned that it might suffer a taxonomic detonation at any time, so I thought I'd hold off as long as possible. Such has not happened (yet).

I originally thought I could get away with one post. This was before I actually sat down to the substantial body of literature on A. sanjuanensis. I ended up going through around 60 references, with another few I haven't been able to find yet due to them being dissertations or conference ephemera or some such. This number does not count the many, many cameo performances for our guest, which turns up in almost every paper dealing with titanosaurs, being cited for anatomical comparisons or included in a phylogeny. This is what comes of 1) a century of publications; 2) being the only named titanosaur in the paleontological hotbed of North America; 3) shouldering the burden of breaking the Great North American Sauropod Hiatus™; 4) being (seemingly) represented by lots and lots of specimens; and 5) having a wide geographic distribution.

In the interests of sanity (both yours and my own dwindling reserves) and length, I'm therefore splitting the material over multiple posts for February, going by geography. There are three natural geographic divisions (New Mexico, Utah, and Texas), plus some miscellaneous records of interest that should fit under that format (Wyoming and Montana with Utah, and Mexico with Texas), so I think three posts will take care of things. We'll start off with New Mexico, because chronologically that's where the story begins.

(Of course, in March someone will publish a paper that will undo everything.)

Sunday, January 24, 2021

Vermillion Falls

As the old story goes, when you visit a place, you go to all the sights, but if you live there, you never get around to seeing them. I decided to play the tourist and see Vermillion Falls in Hastings, which I'd never done despite living about 10 to 15 minutes away most of my life. (And yes, it's spelled with two "l"s here.)

Partly frozen over, with adjoining industrial facility at the falls itself.

Looking down into the gorge from above the falls.

Vermillion Falls is a waterfall on the Vermillion River, a tributary to the Mississippi. The falls and downstream gorge are actually not unlike a miniature version of the Mississippi gorge from Fort Snelling up to St. Anthony Falls. Aside from scale, the major difference is the steeper walls. Unlike the Mississippi, which has only had to contend with about 15 to 30 feet (5 to 10 m) of Platteville Formation before getting to the soft underbelly of Glenwood and St. Peter, the Vermillion has the task of cutting through something like 100 to 150 feet (30 to 45 m) of genuine Prairie du Chien Group, which hasn't eroded peaceably for anyone in 475 million years and isn't about to start now. The walls of the gorge have been weathered to a crisp.

Although we can identify several substantial subdivisions, and plenty of beds.

Looking downstream within the gorge, from the floor.

Hastings escaped the attention of the most recent glaciation, so the Vermillion River has had longer to work on its gorge than the Mississippi has in Minneapolis–St. Paul above Dayton's Bluff. Instead, the current incarnation of the Vermillion River postdates the preceding glaciation, the Illinoian, which would make Vermillion Falls's origin about an order of magnitude older than St. Anthony Falls and the other Mississippi gorge falls (i.e., older than a hundred thousand years rather than ten thousand years). Before that, the Vermillion disappears into the hazy web of buried channels beneath the glacial drift. Hastings is surrounded by buried channels, including a massive example south of town cut down all the way into the Franconia (see Mossler 2006 for the layout). In fact, if some evil genius were to remove all of the loose post-bedrock sediment, most of metropolitan Hastings would become a roughly rectangular island. (Also of note: the Hastings Fault only clips the northwest corner of the city.)

Looking upstream in the gorge toward the falls (not visible due to a bend in the river) from a small bridge.

Sneaking a peek from just below.

References

Mossler, J. H. 2006. Bedrock geology of the Hastings Quadrangle, Dakota, Goodhue, and Washington Counties, Minnesota. Minnesota Geological Survey, St. Paul, Minnesota. Miscellaneous Map 169. Scale 1:24,000.

Saturday, January 16, 2021

Your Friends The Titanosaurs, Part 32: Volgatitan, Xianshanosaurus, Yamanasaurus, and Zhuchengtitan

Here we are, at the end of the alphabet. You might have noticed that every letter has had an entry except one: W. Wintonotitan sometimes ends up in Titanosauria, but it's not a consensus titanosaur. This means, of course, that those of us who are describing new titanosaurs should consider generic names starting with "W" (as well as adding a couple more to those letters represented by single names). We aren't at the end of the series, though; for one thing, there is still one rather significant genus and species that hasn't yet taken its turn in the spotlight...

Anyway, the four titanosaurs at the end of the alphabet include some of the most recently described genera and species, which isn't really surprising; it wasn't until the past couple of decades that genera beginning with letters after "T" became more than a novelty. Three of the four postdate 2016, leaving Xianshanosaurus as the relative oldster with a 2009 name. This means there isn't a lot of literature for them, so having four in one post seems reasonable. The four are also alike in that each name is a double geographic reference.

Sunday, January 3, 2021

J-Term 2001: Zion National Park in the snow

Nothing too heavy for the first post of 2021, just a few photos. These were taken twenty years ago, during field camp with the University of St. Thomas. We were doing mapping in the Rainbow Gardens area east of Las Vegas, in the figurative shadow of Frenchman Mountain. We started out January 7, 2001, and for several days had progressively worse weather until on the morning of the 12th, the forecast was the worst yet, so we drove over to Zion National Park for some geo-tourism. Predictably enough, it snowed at Zion while playing nice at our field area. Anyway, the weather turned for the better after that.



These were all scanned from physical photographs. Forget cell phone cameras; I don't think I'd ever even used a digital camera by 2001. This also means that, unlike today when you take as many photos as you want, I wasn't taking loads of photos a day.

Zion gets about an inch of snow (2.54 cm) on average each month of the winter, so we'd managed to show up on the day of the monthly delivery for January (plus a little more).


Group photo! Apparently black and/or blue coats were the style in Minnesota in the winter of 2000–2001. Our inadvertent coordination (and hats and hoods!) makes it a real puzzle to identify more than about half of us in this photo.

Your host, January 2001. Still have the hat. Welcome to 2021!

Sunday, December 27, 2020

Your Friends The Titanosaurs, part 31.5: Garrigatitan meridionalis

Santa brought along one more titanosaur to place under the tree. It's not a super-titanosaur, although it still probably wouldn't fit too comfortably in your house. Welcome Garrigatitan meridionalis, joining us from the late Campanian of southern France.

Unrelated: Rare miniature boreal sauropods. This unnamed taxon is also notable for its unusual osteoderms and short tail with well-developed caudofemoralis muscles.