Your Friends The Titanosaurs, part 6: Austroposeidon, titanosaurs of Balochistan, and Baotianmansaurus

For Thanksgiving (US), we're getting overstuffed with extra titanosaurs. We're also venturing to three different Cretaceous landmasses: South America for Austroposeidon magnificus, the formerly separate landmass of the Indian Plate for a group of titanosaurs from Pakistan, and Asia for Baotianmansaurus henanensis.

Decorah gastropods (and some things that look like gastropods)

The snails* of the Decorah Shale are a lesser component of the fauna than bryozoans, brachiopods, or crinoids. My personal experience is that snails are uncommon except for certain beds, which feature abundant and diverse snails. One of these beds is perhaps 20 ft (6 m) above the top of the Carimona in St. Paul; this bed produced the plate in the "Equatorial Minnesota" box near the top of the page. For whatever reason, this bed also hosts abundant trilobite pieces, particularly of Eomonorachus. There's probably a facies thing going on, such that the original depositional environment was favorable to snails and trilobites; it's not quite as stark as, say, McKee (1938)'s mollusk and open marine facies of the Kaibab Formation (the very durable rock at the top of the Grand Canyon stack), but there's certainly some kind of difference. It might be a carbonate thing; both the underlying Platteville and overlying Cummingsville/Prosser, which have more limestone and dolomite, also have more diverse mollusks than the muddy Decorah (Sloan and Webers 1987). On the other hand, the relatively limited diversity and abundance of snails, combined with most genera having visually distinctive appearances, make it possible to summarize them in a reasonably brief guide.

*and things that look a whole lot like snails, and things that people argue about, such as Sinuites

Several snails in a small section of a slab: C for Clathrospira, S for Sinuites, and L for "lophospiroid".

Rebbachisauridae

Diplodocoidea contains three wings: Diplodocidae, where the popular diplodocoids such as Apatosaurus, Barosaurus, Brontosaurus, and Diplodocus hang out; Dicraeosauridae, somewhat undersized and short-necked sauropods that are seemingly content to be represented in the public eye by Amargasaurus and its magnificently strange vertebrae; and Rebbachisauridae, also generally known for undersized and short-necked sauropods represented in the public eye by one exceptional taxon. In the case of rebbachisaurids, it's Nigersaurus, famous for its skull, which looks kind of like the animal habitually slept with its snout pressed against a wall.

Yeah, like that. Photo taken at a traveling exhibit at the Science Museum of Minnesota back in May 2014.

Cumberland Bone Cave

There are a handful of notable Pleistocene "bone caves" in the Mid-Atlantic states. We've stopped at one of the classic sites already, Port Kennedy Bone Cave. Another classic site is Cumberland Bone Cave in western Maryland. Its scientific history began a few decades later than Port Kennedy, but both sites are of Irvingtonian age (between approximately 1.9 and 0.25 Ma), rather than a younger age like most Pleistocene sites, and the faunas from the two sites are often mentioned together.

Your Friends The Titanosaurs, part 5: Argyrosaurus, Atacamatitan, and Atsinganosaurus

We're almost beyond the letter "A" in the alphabet of titanosaurs (for whatever reason titanosaur researchers have given a disproportionate number of genera names that begin with "A"). For this entry we have a historic name (Argyrosaurus superbus), the first non-avian dinosaur named from Chile (Atacamatitan chilensis), and our second well-represented smallish titanosaur from from western Europe (Atsinganosaurus velauciensis).

Compact Thescelosaurus Year Three

It's mid-October, with National Fossil Day coming up (Wednesday the 17th) and the anniversary of the original Thescelosaurus just behind us (Sunday the 7th). It's also time for something new for The Compact Thescelosaurus on its third birthday. Last year, pterosaurs joined dinosaurs and choristoderes. This year, plesiosaurs and a variety of more basal sauropterygians and possible sauropterygians join them.

Elasmosaurid Thalassomedon haningtoni, Denver Museum of Nature and Science

Hyoliths III: Season of the Hyolith

You may remember that last year we had some Paleozoic excitement with the publication of specimens showing the enigmatic hyoliths to be lophophorates, related to brachiopods, bryozoans, and phoronid worms (Moysiuk et al. 2017). Independent support for this position has just been published based on Chinese Cambrian specimens. In this case, hyoliths are not only lophophores, but they are stem brachiopods (closely related to modern brachiopods, but not within the group including modern brachiopods, the crown brachiopods), based on the presence of pedicles in a species of basal hyolith (Sun et al. 2018a).

The pedicle is a fleshy organ, found in most brachiopods, which anchors the shell to the substrate. (Curiously enough, our last visit with the brachiopods covered the strophomenids, noted for not having pedicles.) Sun et al. (2018a) describe a new hyolith taxon, Pedunculotheca diania, which has the typical elongate pointed main shell and lid-like operculum of hyoliths (a bit more oval in cross-section than the classic triangles we've seen so far), with the addition of a short nonmineralized stalk ending in a small holdfast growing from the tip of the shell.

An anchored hyolith, like Pedunculotheca diania, would be a suspension feeder, but other, more derived hyoliths were unattached (Sun et al. 2018a). Moysiuk et al. (2017) interpreted hyoliths in general as filter feeders, but it appears that hyoliths were more ecologically flexible. Recent publications have documented aggregations of hyoliths around coprolites (Kimmig and Pratt 2018; Sun et al. 2018b) and dead animals (Sun et al. 2018b), indicating scavenging/detritivore roles. Because skeletal fragments have never been reported in hyolith guts, Sun et al. (2018b) suggested that they focused on the more fluid phase of the decomposing detritus (or at least the non-mineralized phase), or on microbial films growing around the detritus. The authors also found hyoliths associated with small burrows, indicating that they could enter the uppermost substrate.

In my quest to always have different hyolith images when the topic comes up, here is Figure 2a from Plate LXIII in Walcott (1899). It is a "reproduction of photograph of a slab of sandstone, with numerous specimens of H. primordialis, from the St. Croix sandstone of Wisconsin. The small shells are identical with H. gregaria of M. and H. [Meek and Hayden]." The publication is actually on fossils of Yellowstone National Park, but Walcott had identified hyoliths there as basically the same as H. primordialis from Wisconsin, which is why he included this figure. Later, the Yellowstone hyoliths would be transferred to a new species (H. gallatinensis Resser 1938) and eventually genus (Haydenoconus Malinky 2014).

References

Kimmig, J, and B. R. Pratt. 2018. Coprolites in the Ravens Throat River Lagerstätte of northwestern Canada: implications for the Middle Cambrian food web. Palaios 33:125–140. doi:10.2110/palo.2017.038.

Malinky, J. M. 2014. Cambrian Hyolitha and problematica from West Laurentian North America: taxonomy and palaeobiology. Alcheringa 38(3):338–362.

Moysiuk, J., M. R. Smith, and J.-B. Caron. 2017. Hyoliths are Palaeozoic lophophorates. Nature 541:394–397. doi:10.1038/nature20804.

Resser, C. E. 1938. Fourth contribution to nomenclature of Cambrian fossils. Smithsonian Miscellaneous Collections 97(10).

Sun, H., M. R. Smith, H. Zeng, F. Zhao, G. Li, and M. Zhu. 2018a. Hyoliths with pedicles illuminate the origin of the brachiopod body plan. Proceedings of the Royal Society B: Biological Sciences 285(1887). doi:10.1098/rspb.2018.1780.

Sun, H.-J., F.-C. Zhao, R.-Q. Wen, H. Zeng, and J. Peng. 2018b. Feeding strategy and locomotion of Cambrian hyolithides. Palaeoworld 27(3):334–342. doi:10.1016/j.palwor.2018.03.003.

Walcott, C. D. 1899. Cambrian fossils. Pages 440-478 in Geology of the Yellowstone national park. U.S. Geological Survey, Washington, D.C. Monograph 32.