Fossil Canids of the National Park Service

We've been taking a tour of Mammalia for the past two annual "Fossil [Group] of the National Park Service", and this year we'll make it three in a row with man's best friends, the Canidae. The dog record starts up in the Eocene with the hesperocyonines, who held court through the Oligocene but then petered out in the Miocene. Turning up in the Oligocene are the borophagines, or "bone-crushing dogs," and the canines, which include wolves, foxes, domestic dogs, and close relatives. Borophagines, as the nickname suggests, had robust jaws and teeth, which doesn't mean they should be typecast as slavering hypercarnivorous brutes (canids in general have been pretty flexible about diet over their history). They drop out of the record at about the end of the Pliocene, leaving the field clear for the canines, which had been a fairly minor component of the canid radiation until about the Late Miocene. If you're interested in paleontological nitty-gritty on these two groups, check out Wang et al. (1999) on borophagines and Tedford et al. (2009) on canines. Canids, incidentally, are a North American invention, and unlike some other groups that originated in North America (camels, horses, rhinos), they have never gone extinct on the continent.

Your Friends The Titanosaurs: Tiamat valdecii

I've been remiss in getting to our latest titanosaur, in part because I was busy with other projects and in part because it took a while to get a copy of the paper. A side visit to the University of Michigan library system after conference hours solved the second issue, so without further ado I present Tiamat valdecii.

Campus fossils of the University of Michigan

For the previous week I was attending the North American Paleontological Convention, held this year in Ann Arbor, Michigan by the University of Michigan. While walking and wandering on the campus, it became clear that many of the buildings include fossiliferous rock, so I began to look for interesting examples.

Like that. That's interesting. (coin in all examples with coins is a US quarter)

Diamantinasaurs, and being or not being a titanosaur

It's not all about new taxa with titanosaurs here. There are always publications on other topics; it might be fun to do a roundup feature every so often. Anyway, I thought I'd catch up on the Australian branch of the tree, as well as the eternal question of just what is a titanosaur, after all.

The Lives of the Strophs

As mentioned a few years ago, strophomenid brachiopods must have had a different lifestyle than your typical brachiopod. With no pedicle to attach to anything, they would have been loose on the seafloor. Their strongly concave-convex shell anatomy seem likely to have been inconvenient in several ways. If you place them convex-up, the opening between the valves is liable to be in the sediment, which doesn't help a filter-feeder. If you place them concave-up, the shell is liable to be flipped over if it is not partially sunk into the sediment, and even if it's clear, the narrow gape would make the intake prone to fouling. Clearly, though, they must have been doing something right, at least for a few million years in the Late Ordovician if the rocks in the Twin Cities have anything to say about it.

A stroph in the Magnolia Member of the Platteville. See, I can always find ways to use even more photos from Uŋčí Makhá Park!

A new publication by Dattilo et al. (2024) offers a lifestyle reconstruction of the stroph Rafinesquina that may resolve these issues: in brief, rather than a narrow valve gape, these brachiopods may have lived with their valves wide-open.

Perhaps like this, as restored by Kyle Hartshorn for Figure 15, not unlike some modern brachiopods. CC BY 4.0.

Dattilo et al. present several lines of evidence leading to the conclusions that Rafinesquina had a typical gape around 45 degrees and could potentially open wider. The major area of focus was the anatomy of the hinge, including both the hard structures and the inferred musculature. The assembly, as it turns out, is rather more complex than one might suspect just looking at Stroph #46893 in a random Platteville surface. (It's also rather more complex than can be explained in a couple of sentences, so fortunately there is the paper to refer to.)

Although to be fair, Stroph #46893 has its charms.

The possibility of widely gaped strophs leads to some other potential implications. For instance, once the ability to make a respectable gape is admitted, there is also the possibility for mobility. A stroph buried by sediment could have used valve clapping to escape. (And if we're doing that, why not a bit of clap-swimming, like modern scallops?) Clapping is also a great way to quickly clear sediment from the feeding organs, and we may have evidence of this in the form of "moats" around some stroph fossils. A natural wide gape also helps explain how stroph internal anatomy worked: a stroph with a narrow gape has a cramped area for its lophophore to function in, while a stroph with a wide gape doesn't have to worry about this as much, as long as there's enough space to stow the lophophore when the valves are closed. Finally, a wide gape does not settle the concave-up or convex-up question, as the brachiopod can function in either mode. Dattilo et al. suggest that convex-up is more stable and protective for the stroph's soft parts.

References

Dattilo, B. F., R. L. Freeman, K. Hartshorn, D. Peterman, A. Morse, D. L. Meyer, L. G. Dougan, and J. W. Hagadorn. 2024. Paradox lost: wide gape in the Ordovician brachiopod Rafinesquina explains how unattached filter-feeding strophomenoids thrived on muddy substrates. Palaeontology 67(2): e12697. doi:https://doi.org/10.1111/pala.12697.

Uŋčí Makhá Park 2024: another winter, more echinoderms

Two years after opening, Uŋčí Makhá Park can be considered a paleontological gem in the Twin Cities. With its Magnolia Member bedding planes, side cuts through the Magnolia and Carimona, easy access, and lack of vehicle traffic, it's nigh-on perfect for getting in touch with St. Paul as it was about 454–453 million years ago. It's kind of like our own Carnegie Quarry wall, except it's tiny marine invertebrates rather than dinosaurs, it probably wasn't planned, and you can walk right out over it. It's always fun to get to spend time there for work, and like last year, I got the opportunity to assist with a training session for Mississippi National River & Recreation Area seasonals there. Then, of course, I just had to make a quick return trip later to follow up on some things we'd seen.

Your Friends The Titanosaurs: Titanomachya gimenezi

2024 has been productive for titanosaurs. Not counting other titano-centric publications, there have already been (potentially) three new genera and species. For number 3, we head back to the familiar land of Patagonia in Argentina, although in this case our new guest represents an Upper Cretaceous formation with no previous named titanosaurs (which seems like a real oddity these days). Titanomachya gimenezi is also decidedly non-titanic for a titanosaur, hanging out down in the saltasaur neighborhood.