Waukartus

There are so many outstanding fossil sites and productive formations (this link is just a sample) that it's not really feasible to be conversant with all of them and still have time for normal human interactions and responsibilities. I'd love to have that knowledge, but realistically I'd be doing pretty darn good if I only knew North America. A few of them on the linked list are not all that far from the Late Ordovician of the Twin Cities in time and space. We saw the Winneshiek Shale briefly when looking at the Decorah impact crater. Another example is the Waukesha Biota in southeastern Wisconsin, dating to the early Silurian. This assemblage came to mind because of the publication this month of Waukartus muscularis, a cousin to modern millipedes (Briggs et al. 2026).

The Waukesha Biota is found in basal dark shale of the Brandon Bridge Formation, otherwise composed of reddish dolomite. The productive beds are quite limited in distribution, described as extending about 350 m (about 1,150 ft, or not much more than a fifth of a mile) (Briggs et al. 2026). The strata were deposited at the toe of an erosional scarp at the beginning of a marine transgression (Briggs et al. 2026); think of them as akin to sedimentary filler. One of the things that's easy to forget when dealing with Paleozoic marine assemblages that are packed with shells and other hard parts, like our old friend the Decorah Shale, is that there were also a lot of things that just didn't fossilize well, particularly "worms" and arthropods that did not have the convenient durable exoskeletons of trilobites. You can find evidence of them through burrows and microfossils, but it's just not the same thing (it's hard to establish the taxonomic diversity, for one thing!). The Waukesha Biota is a Konservat-Lagerstätte, meaning the preservation is exceptional, and so we get to see those soft-bodied organisms. In fact, the Waukesha Biota is kind of Bizarro World as far as the Paleozoic is concerned, with uncommon brachiopods, crinoids, and mollusks, but abundant and diverse arthropods and "worms" (Wendruff et al. 2020). Preservation seems to have been greatly enhanced by microbial mats (Wendruff et al. 2020).

One of these otherwise unlikely fossils is the present subject, Waukartus muscularis. The genus name refers to Waukesha and limbs, which are an important part of the story, and the species name refers to the preservation of musculature (Briggs et al. 2026). This animal is not actually something that was just found; reports of this fossil animal go back to the 1980s. It was mentioned in the earliest papers on the Waukesha Biota (Mikulic et al. 1985a, 1985b) as a "myriapod-like animal". (Myriapoda is the group including centipedes and millipedes.) Specimens representing parts and sometimes counterparts of nearly three dozen individuals have been found. They top out at a little less than 3 cm (1.2 inches) long and perhaps 10% of that wide, and would have looked rather like chunky basic millipedes from a human's-eye-view. The body features a head, as many as 11 trunk segments (each segment looking deceptively like they were actually two parts), and a terminal segment. Despite the fairly large sample size, there isn't an especially well-preserved head, but there appears to have been four appendages on the head and eyes, likely on stalks. The terminal section is also poorly preserved but had a pair of blade-like projections on the underside (Briggs et al. 2026).

Some of the 35 individuals of Waukartus muscularis, including the holotype (A–E, part and counterpart) (Figure 1 in Briggs et al. 2026, which see for full caption; 5 mm scale in A–D and F, 2 mm for E, H, and I, 1 mm for G and J; ). CC-BY-4.0.

The limbs are the feature that has drawn the most comment. There is one pair of (rather stocky) limbs per trunk segment, unlike true millipedes, which have two. (Hence the scientific name for the group, "Diplopoda", meaning "double feet".) They are uniramous rather than biramous, the ancestral arthropod condition. A uniramous limb has "one branch", whereas a biramous limb forks into two branches. Many aquatic arthropods have biramous appendages and use one branch for locomotion and the other for respiration (think trilobites). Terrestrial insects, arachnids, and myriapods have uniramous limbs, and this has long been thought to be a specific adaptation to living on land (having feathery gill-like things on your limbs like trilobites did isn't quite as useful in the open air). Waukartus, though, was found in marine shales with nothing thought to be definitively terrestrial, and so is thought to have been marine as well. Therefore, uniramous limbs may not have been a terrestrial adaptation, at least in myriapods, but something that came in handy when the move occurred (exaptation, or pre-adaptation if you're older than you'd like to admit) (Briggs et al. 2026). It may have been respiring through its cuticle (Briggs et al. 2026), which is a neat trick you can get away with when you're a little less than 3 cm long.

Waukartus muscularis out for a stroll (head lower center, terminal segment upper left) (Figure 5 in Briggs et al. 2026, restoration by Leia Francis). CC-BY-4.0.

References

Briggs, D. E. G., J. C. Lamsdell, J. Kluessendorf, and D. G. Mikulic. 2026. A marine stem-myriapod from the Silurian Waukesha Lagerstätte, Wisconsin, USA: terrestrial traits pre-date the transition to land. Proceedings of the Royal Society B: Biological Sciences 293(2070). doi: 10.1098/rspb.2026.0131.

Mikulic, D. G., D. E. G. Briggs, and J. Kluessendorf. 1985a. A Silurian soft-bodied biota. Science 228: 715–717.

Mikulic, D. G., D. E. G. Briggs, and J. Kluessendorf. 1985b A new exceptionally preserved biota from the Lower Silurian of Wisconsin, USA. Philosophical Transactions of the Royal Society of London. B, Biological Sciences 311: 75–85.

Wendruff, A. J., L. E. Babcock, J. Kluessendorf, and D. G. Mikulic. 2020. Paleobiology and taphonomy of exceptionally preserved organisms from the Waukesha Biota (Silurian), Wisconsin, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 546(109631). doi: 10.1016/j.palaeo.2020.109631.

Your Friends The Titanosaurs: Phosphatotitan khouribgaensis

The latest friendly titanosaur to come along hails from Morocco, making it the first named Moroccan titanosaur but not the first record. Other occurrences are mentioned here. For some reason it seems like the new names are always specimens that weren't included. Still lots of titanosaurs out there!

Fish Creek Canyon

You never know where interesting geology will turn up. I've been poking around the Twin Cities for years and I'm still coming across places I'd never dreamed were there. Case in point: today's pictorial topic, Fish Creek Canyon. I know the name sounds like a place you might find in Montana or Idaho, where the water is cold, the fish are biting, and the bears are waiting for you to wander away from your cooler, but this particular Fish Creek Canyon is just about where St. Paul, Maplewood, and Woodbury meet. It's not a huge canyon, and I don't imagine the fish are very large these days, but it's the kind of little hidden backyard gem that makes exploring worthwhile. I visited it with a friend back in late November, not long before our on-off winter hit the "on" switch for the first time.

Down in the valley on a great fall day, with Fish Creek in view.

Fish Creek is spread across two city jurisdictions. Maplewood has Fish Creek Natural Area, which is mostly the heights above 494 on the south and east and Highway 61 on the west. If you scout around, you'll find that this is one of a handful of small bluff-top parks between Battle Creek Regional Park and 494 overlooking 61. Adjacent on the north is the actual canyon of Fish Creek, which is within St. Paul and owned by Ramsey County Parks but apparently not organized at the moment, per se. The area is also largely within Mississippi National River and Recreation Area (so I'm also *officially* curious). The bluff-top lands are well worth walking around in their own right. There are no official access points to the canyon from the bluff-top, but it is possible to reach the canyon via social trails, leading to a steep descent into the narrow valley.

The view from the bluff, with the November afternoon sun on a clear day.

The canyon itself is not vast or deep. The water power that carved the original ravine has long since dwindled to a hoppable creek. And yet, what the creek has cut for itself is such a perfect little feature, complete with a miniature waterfall.

You're walking along, and then the creek disappears.

A miniature waterfall.

There ought to be gnomes.

It widens a bit going down (note that this feature was put in by people, presumably for water management, although it's not bad for aesthetics, either).

The rock that has been cut through here is the St. Peter Sandstone in its case-hardened form, producing the steep-sided, narrow slot. If you've driven Highway 61 near here, you may have noticed how the St. Peter sinks out of view for most of the stretch between Battle Creek and Camels Hump in Cottage Grove. It's still there, it just only shows its face sporadically, and this is the most picturesque place to find it. Interestingly, the location of Frederick Sardeson's "Highwood" collecting locality for St. Peter Sandstone fossils was supposedly a little north of here, about a mile and a half south of Battle Creek Park on 61. This works out to about the area where the ravines now occupied by Highwood Avenue and Springside Drive empty out, so our old friend was successfully trying his luck out here back in the 1890s.

Sometimes the St. Peter feels like crumbling, and sometimes it feels like holding a wall.

Afton graptolites revisited

There are two great lost fossil sites in the Twin Cities area. (The Brickyards don't count; they're not lost, they just aren't open to collection.) One is the Johnson Street Quarry, where workers cut into a bed in the Hidden Falls Member of the Platteville Formation that had unusually abundant echinoderms. As described in Sloan et al. 1987: 200, "Sardeson mined out a spot in this unit in the old Johnson Street Quarry in Minneapolis (now filled with garbage, and covered with Interstate 35) that produced about 20 specimens of the starfish Protopalaeaster narrawayi, several specimens of the crinoid Cremacrinus arctus (Fig. 16.2), edrioasteroids, cystoids, brachiopods, bryozoans, molluscs, and graptolites." This is slightly out of date; instead of a dump, there's now a Quarry Shopping Center with a Cub Foods, Home Depot, and Target, although even with all those options you can't get an edrioasteroid there anymore. Regardless of the exact character of the overburden, it seems unlikely that anyone will be doing any paleontological follow-up there anytime soon. The other locality is the Afton graptolite locality in the St. Lawrence Formation. We already had a post on why this locality was important; what I'm curious about is where exactly it was. A locality, even if "lost", had to have been *somewhere*, and apart from the scientific and historic interest, there very well could be similar fossils in rocks nearby. Indeed, Hughes and Hesselbo (1997) reported graptolites in the lowest strata of the St. Lawrence Formation in their Afton section, where collection may have postdated the road work that destroyed the classic location. For some reason, despite its “classic” nature, nobody ever saw fit to just put a pin on the map. What clues do we have?

New page: Quaternary vertebrate inventories (USA)

There's an electronic stack of topics I've considered for blog posts, and within that a subset earmarked "do before hanging up the keyboard". One of these, almost from the very beginning, was a bibliography of Quaternary vertebrate locality inventories like the kind Oliver Perry Hay pulled together. Being a detail hoarder, I've always loved having this kind of information. Maybe I'm the only one, but it's my blog and if I want to put together a page of old locality lists, I'll do it. One might think "If I have to find this information, all I need is the Paleobiology Database" and call it a day, to which I just smile and nod politely. Anyway, you can find the page here.

Pop quiz! Mammoth or mastodon?

New thematic inventories and a bit more cave paleontology

A couple of thematic inventories have just been published with the involvement of the NPS Paleontology Program. One of these is the first part of a paleobotany series, eventually to be three parts covering the Cenozoic, Mesozoic, and Paleozoic. The first part, Matel et al. (2026), covers the Cenozoic and is available for download through February 24. This is one of the projects from the National Park Service-Paleontological Society Paleontology in the Park Fellowship Program. In it, we've worked to provide information on Cenozoic paleobotany for every park unit where it's known. (It's easier to do concisely when the record is one piece of petrified wood than when the park is, say, Florissant Fossil Beds National Monument, so necessarily the scale of detail varies.) For practical reasons the focus is on macrofossils, with pollen and such as an adjunct.

The other new inventory, Santucci et al. 2025, covers NPS cave paleontology from 2002 to 2023. This is presented as an update of a previous report (Santucci et al. 2001). I'm taking the opportunity here to add a postscript because the past couple of years have been very productive. First of all, we came upon a new park record: Kalaupapa National Historical Park, on the north side of Molokaʻi, Hawaii. Although main focus here is historical, this park has a very interesting geological story too, involving the collapse of a volcano and the subsequent growth of another smaller volcano. The smaller volcano is now extinct, leaving behind Kauhakō Crater. Inside the crater people have found bird bones in a cave. One is a partial ulna of the extinct flightless ibis Apteribis glenos, the other is a coracoid of Pterodroma hypoleuca, the modern Bonin petrel, which does not live on the island today (Olson and James 1982, 1991).

Also, a few things in press or under study have progressed in the past couple of years. Avid readers of this blog will know that the "musk ox" of Muskox Cave at Carlsbad Caverns National Park is now named Speleotherium logani (White et al. 2025). The Cumberland Bone Cave monograph has also been published (Eshelman et al. 2025). Most notable, though, has been the publication of work on Mammoth Cave National Park. The park inventory (Toomey et al. 2025) was mentioned here a few months back. There has also been a good short summary of the Mississippian vertebrates (Hodnett et al. 2024a) and no fewer than five new taxa: ctenacanthiforms Troglocladodus trimblei and Glikmanius careforum (Hodnett et al. 2023); petalodonts Clavusodens mcginnisi (Hodnett et al. 2024b) and Strigilodus tollesonae (Hodnett et al. 2024c); and holocephalan Macadens olsoni (Hodnett et al. 2025).

Clavusodens mcginnisi on the prowl, among the crinoids. Illustration by Benji Paysnoe for the National Park Service.

References

Eshelman, R. E., C. J. Bell, R. W. Graham, H. A. Semken, Jr., C. B. Withnell, S. G. Scarpetta, H. F. James, S. J. Godfrey, J. I. Mead, J.-P. Hodnett, and F. V. Grady. 2025. Middle Pleistocene Cumberland Bone Cave Local Fauna, Allegany County, Maryland: a systematic revision and paleoecological interpretation of the Irvingtonian, Middle Appalachians, USA. Smithsonian Contributions to Paleobiology 108.

Hodnett, J.-P., R. Toomey, H. C. Egli, G. Ward, J. R. Wood, R. Olson, K. Tolleson, J. S. Tweet, and V. L. Santucci. 2023. New ctenacanth sharks (Chondrichthyes; Elasmobranchii; Ctenacanthiformes) from the Middle to Late Mississippian of Kentucky and Alabama. Journal of Vertebrate Paleontology 43(3): e2292599. doi: 10.1080/02724634.2023.2292599.

Hodnett, J.-P., R. Toomey, R. Olson, K. Tolleson, R. Boldon, J. Wood, J. S. Tweet, and V. L. Santucci. 2024a. Sharks in the dark: Paleontological resource inventory reveals multiple successive Mississippian Subperiod cartilaginous fish (Chondrichthyes) assemblages within Mammoth Cave National Park, Kentucky. Park Stewardship Forum 40(1): 53–67. doi: 10.5070/P540162921.

Hodnett, J.-P. M., H. C. Egli, R. Toomey, R. Olson, K. Tolleson, R. Boldon, J. S. Tweet, and V. L. Santucci. 2024b. Obruchevodid petalodonts (Chondrichthyes, Petalodontiformes, Obruchevodidae) from the Middle Mississippian (Viséan) Joppa Member of the Ste. Genevieve Formation at Mammoth Cave National Park, Kentucky, U.S.A. Journal of Paleontology 98(6): 1087–1097. doi: 10.1017/jpa.2024.40.

Hodnett, J.-P., R. Toomey, R. Olson. J. S. Tweet, and V. L. Santucci. 2024c. Janassid petalodonts (Chondrichthyes, Petalodontiformes, Janassidae) from the middle Mississippian (Viséan) Ste. Genevieve Formation, Mammoth Cave National Park, Kentucky USA. Historical Biology 36(9):1783–1792. doi: 10.1080/08912963.2023.2231955.

Hodnett, J.-P., R. Toomey, H.-D. Sues, V. Santucci, K. Tolleson, and J. Tweet. 2025. A new euchondrocephalan chondrichthyan (Chondrichthyes, Euchondrocephali) from the Middle Mississippian (Viséan) Joppa Member of the Ste. Genevieve Formation at Mammoth Cave National Park, Kentucky, USA and a reassessment of the Lower Mississippian (Tournaisian-Viséan) “Helodus” coxanus Newberry, 1897. New Mexico Museum of Natural History and Science Bulletin 100: 87–93.

Matel, T. P., I. B. Huegele, C. R. Cace, K. M. M. Bober, L. D. Boucher, V. E. McCoy, E. J. Hermsen, S. R. Manchester, C. C. Visaggi, J. S. Tweet, and V. L. Santucci. 2026. Cenozoic paleobotanical resource inventory of the National Park System. Elements of Paleontology. Cambridge: Cambridge University Press. 10.1017/9781009770477.

Olson, S. L., and H. F. James. 1982. Prodromus of the fossil avifauna of the Hawaiian Islands. Smithsonian Contributions to Zoology 365: 1–59.

Olson, S. L. and H. F. James. 1991. Descriptions of thirty-two new species of birds from the Hawaiian Islands. Part I. Non-Passeriformes. Ornithological Monographs 45:1-88.

Santucci, V. L., J. Kenworthy, and R. Kerbo. 2001. An inventory of paleontological resources associated with National Park Service caves. National Park Service Geological Resources Division Technical Report NPS/NRGRD/GRDTR-01/02.

Santucci, V. L., J.-P. Hodnett, P. Seiser, J. S. Tweet, and J. Wood. 2025. National Park Service cave paleontology: 2002-2023. Journal of Cave and Karst Studies 87(4):108–116. doi: 10.4311/2024PA0119.

Toomey, R. S., J. S. Tweet, and V. L. Santucci , editors. 2025. Mammoth Cave National Park: Paleontological resource inventory (public version). Science Report NPS/SR—2025/243. National Park Service, Fort Collins, Colorado. https://doi.org/10.36967/2308547 

White, R. S., J. I. Mead, and G. S. Morgan. 2025. Logan's austral scrubox, a new ovibovine (Mammalia: Artiodactyla: Bovidae) from Muskox Cave, Eddy County, New Mexico. New Mexico Museum of Natural History and Science Bulletin 101: 473–494.

Your Friends The Titanosaurs: Yeneen houssayi

What do you get the formation that has five established titanosaur species and a couple of ne'er-do-wells? A sixth titanosaur, of course!

All joking aside, it's misleading to think of "Titanosauria" as a relatively small-scale group like Diplodocidae or Brachiosauridae when it's really a massive, sprawling complex including multiple distinct lineages that essentially monopolized all things sauropod in the Late Cretaceous. We talk of the Morrison Formation having diplodocids and dicraeosaurids and camarasaurids and brachiosaurids and whatever else, and that may sound more impressive than the Bajo de la Carpa Formation having six different titanosaurs. "What? You need all those titanosaurs?" "All those titanosaurs" are functionally replacing each of those smaller clades of the Morrison, as well as apparently just about everything else large and herbivorous. It's just the relationships and smaller divisions are still fuzzy. Eventually, we'll have a better grasp. But enough philosophy! Let's bring on today's guest, Yeneen houssayi. (And thank you to Alberta Claw and Stephen Poropat for supplying me with the paper!)