Sunday, July 3, 2022

Fossil Felids of the National Park Service

For this year's annual focus on a fossil group in National Park System units, I am going to pay my Internet cat tax and present a quick look at the fossil felids of the parks. If you're not familiar with the history of Felidae, it may come as a surprise that cats are a relatively recent innovation. They have only a few tens of millions of years under their collective belts, and didn't arrive in North America until Pseudaelurus in the early Miocene. (Note: barbourofelids and nimravids may give off saber-toothed cat vibes, but they aren't Felidae.)

It turns out that there are 24 NPS units with cat body or trace fossils. All of the records, unsurprisingly, are early Miocene in age or younger. The great majority are Quaternary (concerning the question of when to cut off the paleontological record, caves don't discriminate if you happen to be 11,000 years old rather than 12,000 years old, and neither do we): only seven of the 24 park units have pre-Q cats. These are Big Bend National Park, Death Valley NP, Hagerman Fossil Beds National Monument, John Day Fossil Beds NM, Lake Mead National Recreation Area, Mojave National Preserve, and Niobrara National Scenic River.

These maps are so much easier to make now that I have one file with all of the parks as points, and I can just turn them on and off. 1. John Day Fossil Beds National Monument; 2. Oregon Caves NM; 3. Lava Beds NM; 4. Hagerman Fossil Beds NM; 5. Yellowstone National Park; 6. Great Basin NP; 7. Death Valley NP; 8. Tule Springs Fossil Beds NM; 9. Lake Mead National Recreation Area; 10. Mojave National Preserve; 11. Joshua Tree NP; 12. Grand Canyon NP; 13. Chaco Culture National Historical Park; 14. White Sands NP; 15. Carlsbad Caverns NP; 16. Guadalupe Mountains NP; 17. Big Bend NP; 18. Amistad NRA; 19. Waco Mammoth NM; 20. Niobrara National Scenic River; 21. Ozark National Scenic Riverways; 22. Chickamauga & Chattanooga National Military Park; 23. Potomac Heritage National Scenic Trail; 24. Valley Forge NHP.

Geographically the sites are concentrated in the southwestern US; in fact, 15 of the sites are in Arizona, California, Nevada, New Mexico, or Texas. This seems to say something about cat biogeography, given these are mostly Quaternary sites and the NPS has a pretty good Quaternary record in terms of geographic spread. I wouldn't base a thesis on it or anything, though.

It's not stated on the map, but the Quaternary record is heavy on caves; a dozen of the records are from caves or rock shelters. These included significant records at Carlsbad Caverns NP, Grand Canyon NP, Guadalupe Mountains NP, Potomac Heritage NST (Cumberland Bone Cave), and Valley Forge NHP (Port Kennedy Bone Cave).

Most of the records are body fossils, but at least three have cat trace fossils: tracks at Death Valley NP and White Sands NP, and tracks and cave scratches at Chickamauga & Chattanooga NMP. One of these sites has yielded a track type specimen, Felipeda scrivneri Sarjeant et al. (2002) from Death Valley NP. There are also eight fossil felid species named from body fossils discovered within or potentially within NPS areas (all named before the units were established):

  • Felis lacustris Gazin (1933) from Hagerman (now Puma lacustris)
  • Machairodus? hesperus Gazin (1933) from Hagerman (now Megantereon hesperus)
  • Felis augustus Leidy (1872) possibly from Niobrara (now Panthera onca [augusta], and Pleistocene instead of Miocene in age)
  • Felis (Pseudaelurus) intrepidus Leidy (1858) possibly from Niobrara (now Pseudaelurus intrepidus)
  • Crocuta inexpectata Cope (1895) from Valley Forge (now Miracinonyx inexpectatus) 
  • Lynx calcaratus Cope (1899) from Valley Forge (now considered a synonym of Lynx rufus)
  • Smilodon gracilis Cope (1880) from Valley Forge
  • Uncia mercerii Cope (1895) from Valley Forge (now considered a synonym of Smilodon gracilis)

Attaining consensus on cat taxonomy and nomenclature can be like, well, herding cats. It doesn't help that it can be difficult to tell cats apart; see a record of "Panthera onca" at Carlsbad Caverns NP becoming Panthera atrox (Kottkamp et al. 2022), and "Puma concolor" fossils at Grand Canyon NP becoming Miracinonyx trumani (Hodnett et al. 2022; take the skull for a spin here). Nevertheless, the Quaternary sample can be divided among seven species or species groups. Three are extinct:

  • American cheetah (Miracinonyx inexpectatus and M. trumani): found at Carlsbad, Grand Canyon, Potomac Heritage, and Valley Forge
  • American lion (Panthera atrox): found at Carlsbad, Potomac Heritage, and Tule Springs
  • Saber-toothed cats (Smilodon spp.): found at Potomac Heritage, Tule Springs, Valley Forge, and Waco Mammoth

Two are still around but not this far north:

  • Jaguar (Panthera onca): found at Lava Beds, Oregon Caves, Ozark, Potomac Heritage, and Valley Forge (these are all pretty far north for something we associate with tropical jungles!)
  • Jaguarundi (Herpailurus yagouaroundi): found at Valley Forge

Finally, two are still found in the United States:

  • Bobcat (Lynx rufus, with allowance for Lynx sp.): Amistad, Carlsbad Caverns, Chaco Culture*, Great Basin*, Grand Canyon, Guadalupe Mountains, Joshua Tree*, Lava Beds, Tule Springs, Valley Forge, and Yellowstone* (*=Holocene only)
  • Cougar/mountain lion/puma (Puma concolor): Carlsbad Caverns, Chaco Culture*, Guadalupe Mountains, and Tule Springs

The most species-rich sites are:

  • Carlsbad Caverns NP (American cheetah, American lion, bobcat, cougar)
  • Hagerman Fossil Beds NM (American cheetah, Homotherium sp. [a saber-toothed cat], Lynx rexroadensis, Megantereon hesperus [or cultridens; another saber-toothed cat], Puma lacustris)
  • Tule Springs Fossil Beds NM (American lion, bobcat, cougar, saber-toothed cat)
  • Valley Forge NHP (American cheetah, bobcat, jaguar, jaguarundi, saber-toothed cat)

Of these four, the Hagerman assemblage is Pliocene, the Valley Forge assemblage is middle Pleistocene, and the other two are late Pleistocene. In the Pleistocene, at least, a robust cat assemblage may include a big lion-type cat, a saber-toothed cat, a smaller big cat (but apparently not cougars and jaguars at the same place), and a bobcat-sized cat.

Felids are relatively uncommon compared to the other big terrestrial carnivorans. Fossil dogs and bears are more widely distributed in NPS units than cats. Furthermore, all but one NPS assemblage that has cats also has dogs, bears, or both (the exception being the Pliocene tracks of Death Valley NP). These groups, though, are for another time...

References

Cope, E. D. 1880. On the extinct cats of America. American Naturalist 14(12):833–858.

Cope, E. D. 1895. The fossil Vertebrata from the fissure at Port Kennedy. Proceedings of the Academy of Natural Sciences of Philadelphia 47:446–450.

Cope, E. D. 1899. Vertebrate remains from Port Kennedy bone deposit. Journal of the Academy of Natural Sciences of Philadelphia, 2nd series, 11(3):193–286.

Gazin, C. L. 1933. New felids from the upper Pliocene of Idaho. Journal of Mammalogy 14:251–356.

Hodnett, J. P., R. White, M. Carpenter, J. Mead, and V. L. Santucci. 2022. Miracinonyx trumani (Carnivora; Felidae) from the Rancholabrean of the Grand Canyon, Arizona and its implications on the ecology of the “American cheetah.” New Mexico Museum of Natural History Bulletin 88:157–186.

Kottkamp, S., V. L. Santucci, J. S. Tweet, R. D. Horrocks, and G. S. Morgan. 2022. Pleistocene vertebrates from Carlsbad Caverns National Park, New Mexico. New Mexico Museum of Natural History and Science Bulletin 88:267–290.

Leidy, J. 1858. Notice of remains of extinct Vertebrata, from the valley of the Niobrara River, collected during the exploring expedition of 1857, in Nebraska, under the command of Lieut. G. K. Warren, U.S. Top. Eng., by Dr. F. V. Hayden, Geologist to the expedition. Proceedings of the Academy of Natural Sciences of Philadelphia 10:20–29.

Leidy, J. 1872. Remarks on some extinct vertebrates. Proceedings of the Academy of Natural Sciences of Philadelphia 24:38–40.

Sarjeant, W. A. S., R. E. Reynolds, and M. M. Kissell-Jones. 2002. Fossil creodont and carnivore footprints from California, Nevada, and Wyoming. Pages 37–50 in R. E. Reynolds, editor. Between the Basins: Exploring the western Mojave and southern Basin and Range Province. California State University, Fullerton, California.

Sunday, June 26, 2022

The doldrums

There's been a distinct lack of dinosaurian content around here for the past few months. To be honest, this is partially on my end: my own attention and energy have been elsewhere, and I haven't been all that interested in what has been coming down the pipe (I don't care if spinosaurs fished, hunted, scavenged, browsed, or got take-out). However, there is something external going on as well. With about half of the year in the books, I think it's reasonable to guess that 2022 is not going to be remembered as a banner year in the field of dinosaur paleontology. This is a predictable result of the COVID-19 pandemic: you don't just find a couple of bones in the rock and name them then and there. (Well, you *can*, but it generally doesn't go over well. Don't you at least want to prep the bones first?) Between excavation, preparation, comparative study, writing, revising, reviewing, and publishing, description of a fossil takes years. What happens when travel is greatly curtailed and museums close their doors? You've cut off those first three parts. Sure, maybe you have time to write now, but you can't participate in expeditions and excavations, you can't prepare fossils, and you can't go to other institutions to look at their specimens. The slowdown wasn't immediately evident in the literature in 2020 because there were still plenty of papers in the pipeline. With that in mind, there was still a pretty decent flow through 2021.

Then things tightened up. Looking at one measurement of activity, in 2022 we've gone through three stretches of a month or more without a new genus or species: from late December 2021 to early February 2022, mid-March to late April, and early May to the present. We're currently in the longest gap between new taxa since whatever happened (or didn't happen) between late November 2016 and early February 2017. In addition, many of the species that have been named are not known from especially complete specimens, to put it politely. I don't know about you, but I've gotten the impression that there's been some clearing out of small projects (which would make sense under pandemic conditions). This slowdown would reflect the challenges of working on research projects in 2020–2021, and it would be safe to suspect that we are in for at least a few more slow months (with the opportunity for global political and economic instability to wreak their own impacts following).

Sunday, June 12, 2022

Fusulinids: Jumbo Forams

Foraminifera are among the most abundant and best known kinds of microfossils (and they aren't exactly confined to the past, either). While it's true that many aren't microscopically microscopic, they're still smaller than is comfortable for practically any human being to study without some kind of magnification at hand. Without such, you'd be stuck squinting at sand-grain-sized things and making such helpful observations as "okay, this one looks like a stack of spheres, and this one is coiled up, and this one is... no, wait, that's an itty-bitty fish vertebra or something." And then there are some that don't require quite as much eye strain to spot.

Like these: every grain-looking thing is a foram.

Among these giant microfossils are the fusulinids (or "fusies" if you're lazy like me), the kings of the realm of single-celled organisms during the late Paleozoic. If you can see something the size of a rice grain or a grass seed, you can see a fusulinid. In fact, the comparison will give you the idea of what to look for: fusulinids tend to look like fat, whitish seeds. The Latin word "fusus" means "spindle-shaped", or "something that's long, widest in the middle, and tapering at the ends". There's your fusulinid.

And there's another, and another... These are getting to around 3 mm long, or a bit more than a tenth of an inch. (Note also what looks to be a sliver of a trilobite pygidium near the center.)

During their heyday, fusulinids could be so abundant that their tests (shells, basically) could more or less make up sediment beds. The resulting rocks are a bit monotonously fossiliferous, as fusulinids tended to look the same on the outside. The interior architecture of chambers is how different species are distinguished, so even though you can see them without needing a microscope, you're going to need one to tell them apart. (Plus the grinding and polishing and all that jazz.) "Why bother?", you may ask. Well, it turns out that the geologically rapid turnover of fusulinid species makes them great biostratigraphic indicators in some places where people are keenly interested in subterranean resources (like the Permian oil fields of Oklahoma and Texas). Know the fusulinids, know the rock; know the rock, know the resources.

Zooming down to an even closer look, we can see that many of the fusulinids have a "perforate" appearance, which is the result of weathering exposing some of the internal chambers. Although most of the forams are seen lengthwise, there are some cross-sections scattered throughout, showing rings of chambers.

The particular examples in these photos come not from in situ outcrops, but building stone. The rock is Cottonwood Limestone used in historic structures in Kansas, and although there are other fossils, the fusulinids are by far the most abundant. The Cottonwood is early Permian in age (Wolfcampian stage in the grand old North American series), so at this point the fusulinids had a few tens of millions of years left to flourish before bowing out at the end of the Permian. According to my old copy of "Invertebrate Fossils" by Moore, Lalicker, and Fischer (1952), this would most likely represent the Pseudoschwagerina zone.

The stairs are made of forams! (No, it doesn't have the same ring as "The floor is lava!", but you *are* walking on the bodies of millions of fossilized amoeba things...)

Sunday, May 29, 2022

Recent Work from the National Park Service Paleontology Program

My day job is with the Paleontology Program of the National Park Service, and I thought you might like to see some of the work we've put out over the past few months. First up is the Spring 2022 issue of the Park Paleontology newsletter. For this issue, we have articles on:

Next, a couple of articles have just come out in the latest volume of the New Mexico Museum of Natural History and Science Bulletin series, both focused on Quaternary cave paleontology of specified parks in the southwest. Hodnett et al. (2022) describes previously overlooked bones from Grand Canyon National Park as specimens of the "American cheetah" Miracinonyx trumani. Meanwhile, drawing on the Carlsbad Caverns National Park paleontological inventory published a few years ago, Kottkamp et al. (2022) discusses the Pleistocene vertebrate record of the park's various caves.

Finally, public versions of our four latest park-specific paleontological inventory reports are also available to view and download. For just four parks, they feature a wide range of types of fossils, geology, and geography. They are:

References

Hodnett, J. P., R. White, M. Carpenter, J. Mead, and V. L. Santucci. 2022. Miracinonyx trumani (Carnivora; Felidae) from the Rancholabrean of the Grand Canyon, Arizona and its implications on the ecology of the “American cheetah.” New Mexico Museum of Natural History Bulletin 88:157–186.

Kottkamp, S., V. L. Santucci, J. S. Tweet, R. D. Horrocks, and G. S. Morgan. 2022. Pleistocene vertebrates from Carlsbad Caverns National Park, New Mexico. New Mexico Museum of Natural History and Science Bulletin 88:267–290.

Sunday, May 15, 2022

Rockfall

One of the characteristic aspects of the Mifflin Member of the Platteville Formation is its habit of planar jointing. The faces of outcrops often look like someone took a rock saw to them. Nor are they necessarily single flat planes; sometimes joints intersect to form sharp angles. The heavy thunderstorms the previous week inspired a large chunk of Mifflin outcrop to collapse along intersecting joints.

Tumbled down

The joint planes did not form overnight, which can be seen by the amount of roots and soil in the new outcrop faces. There were some pretty big roots in there as well, but whatever tree(s) had once produced them is long gone.

A view into the wedge more or less along one of the two joints.

This particular rockfall was about as polite as possible, occurring not at the top of a stereotypical 30-foot bluff but from a much lower bluff, adjacent to a bike path. The orientation of the wedged stack shows that it toppled out of its former position. The top of the stack is therefore farthest from the bluff. Perhaps it failed at the base first, due to poor support from the Pecatonica, then flopped over.

History going from left to right

Saturday, April 30, 2022

Synchronicity of Large Crinoids

I was recently out of town for work, and one of the things I saw was Middle Pennsylvanian-age building stone with stem segments from large crinoids:

Big ol' crinoids

It's like bony fingers strewn on the ground

You'd think with all this stem, there'd be a calyx somewhere, but no dice

At a shade over 1 cm (about 0.4 in) in diameter, the columnals are quite a bit bigger than garden-variety columnals, but still are well shy of world champ columnals, which reportedly exceed 2.5 cm (1 in); certainly much bigger than anything in Minnesota, right?

Yes! Time for the ironic photo!

Only yesterday, less than a week after returning from the above trip, I was visiting a couple of Decorah Shale sites and came across the above specimen. I happened to be caught short of a traditional scale bar, so you will have to take my word that the fingernail of the above finger is 1.1 cm (0.43 in) across at its widest point. Therefore, that columnal is 1.5 cm (0.59 in) across, which is pretty darn big for anything in the Decorah except for certain trilobites. In fact, it made me wonder if the stone might be a ringer transported from another formation, by glacier, river, or what-have-you. (Not impossible at all; here's a neat report on all kinds of exotic rocks and fossils found in Mississippi gravel, including Lake Superior agates and Sioux Quartzite; closer to home, a piece of an Upper Cretaceous ammonite was once found at the Brickyard, as related in Cobban and Merewether 1983:19.) However, the chunk shows no evidence of transport, and lithologically it looks the same as any piece of thin limestone eroded out of the Decorah. Were it not for the great honking columnal, I wouldn't have thought twice about its legitimacy. (I wouldn't even have thought once!) My guess is that this particular specimen originated from higher in the formation than the stuff I usually see, or that great honking crinoids were a very minor part of the Decorah fauna and this just happens to be my first encounter.

References

Cobban, W. A., and E. A. Merewether. 1983. Stratigraphy and paleontology of mid-Cretaceous rocks in Minnesota and contiguous areas. U.S. Geological Survey, Washington, D.C. Professional Paper 1253.

Sunday, April 10, 2022

Mitchell Caverns

Back in the fall of 2021, I made a work visit to Mojave National Preserve, located logically enough within the Mojave Desert of southern California. While there, I had the opportunity to tour Mitchell Caverns. Mitchell Caverns is in the unusual position of being part of a state land parcel (Mitchell Caverns Natural Preserve or State Natural Preserve, depending on the source), entirely surrounded by another parcel of state land (Providence Mountains State Recreation Area), which is itself surrounded by a National Park Service unit (Mojave National Preserve). For good measure, the cave system is also a National Natural Landmark. It's parks all the way down in the Providence Mountains. (To be fair, the natural preserve designation is kind of a map artifact; it's not really distinct from the state recreation area.)

Sunday, March 27, 2022

Detour into Choristodera

This week a paper on unusual prehistoric aquatic reptiles was published. I am speaking, of course, of Brownstein (2022) on choristoderes. (If you thought it was going to be spinosaurs, you must be new around here!)

We have a soft spot for choristoderes here at Equatorial Minnesota Towers, even if they rarely rate so much as an "and also featuring Champsosaurus" credit in sci-pop culture. Brownstein (2022) includes the classic Champ but is more focused on the short(er)-faced choristodere Simoedosaurus, although under a fresh coat of taxonomic paint: the North American species S. dakotensis is moved to the new genus Kosmodraco on the grounds of anatomical differences and differences in time and place from the type species, European S. lemoinei. It also gets a new friend, K. magnicornis. Which said, sure... but the species of Kosmodraco still clade more closely to Simoedosaurus than to anything else, so if your genericometer was so tuned, you could still include them in Simoedosaurus with a clear phylogenetic conscience. (There are a lot of anatomical differences between the two genera. My only quibble with Kosmodraco is that it's an awfully pretty name for a choristodere; it sounds more like an an extravagantly crested pterosaur. Meanwhile, Champsosaurus itself is still secretly a taxonomic booby trap waiting to be sprung. Sooner or later someone is going to do something with the various species that is entirely legal by the rules of taxonomy and yet manages to displease everyone else.)

The type skull of Kosmodraco magnicornis. It'll take a moment to orient yourself: the bitey part is surprisingly short (see the "r. lacrimal"? The eye was behind that). What you're looking at is a modest snout attached to a greatly flaring right "cheek" (which comes with a scalloped fringe). Figure 1 in Brownstein (2022). CC BY 4.0.

Either way, the skull is worth a look. There's garden-variety "weird" and then there's "why is this all practically all post-orbital?" (It certainly wasn't for intellect, most of the posterior of choristodere skulls being a series of struts and bars. Note that the maxillary teeth of Kosmodraco only go back as far as the eyes.) Champsosaurus, as we've already seen, had a long, narrow toothy muzzle, with the rest of the skull being broad and low. Kosmodraco had a skull that was still low but much more wedge-shape in dorsal view, as if someone smooshed or amputated a Champsosaurus-like snout. The business end of a Kosmodraco skull is an interesting analog for the modern alligator gar. It's the back of the skull where things get different, as Brownstein (2022) notes. Kosmodraco has a lot more skull going on behind the eyes, which themselves are elevated on skull like those of an alligator. The posterior margin is also ornamented with a series of knobs, and the skull is quite low (Brownstein 2022).

A comparison of the palatal regions of choristoderes Kosmodraco and Champsosaurus to an alligator and an alligator gar also serves as a comparison of basic facial shapes for the four. Similarities between Kosmodraco and the gar aren't as great if you continue through the rest of the skull. Figure 13 in Brownstein (2022). CC BY 4.0.

I'd like to take the opportunity to note that there's another extinct group of aquatic tetrapods with flat, blunt, broad skulls and eyes relatively far forward on the skull, which has so far avoided comparisons to Simoedosaurus/Kosmodraco: the metoposaurid amphibians of the Triassic. Again, it's not a perfect comparison (metoposaur snouts are blunter), but it would seem to point to the long-term existence of a niche for freshwater predators with certain cranial adaptations.

One of the other points noted by Brownstein is there is more diversity in choristoderes than you might suspect by simply looking at the number of genera. For example, as of this writing Champsosaurus is composed of several species over about 20 million years. North American specimens have tended to be lumped with either the short-faced Simoedosaurus or the long-faced Champsosaurus.

References

Brownstein, C. D. 2022. High morphological disparity in a bizarre Paleocene fauna of predatory freshwater reptiles. BMC Ecology and Evolution 22: article number 34. doi:10.1186/s12862-022-01985-z.

Sunday, March 20, 2022

The Grand Pitch Formation

Back in October I posted on a formation I saw in Maine, the Matagamon Sandstone. While going through my photos, I realized I had a number of scenic and interesting shots of another formation, also not widely known: the Grand Pitch Formation.

Comes with waterfalls!

The Grand Pitch Formation goes back in the literature to the 1930s, when it was known as the Grand Falls Formation (Ruedemann and Smith 1935). This name, though, was already in use, so the more specific Grand Pitch name was substituted (Neuman 1962). The name refers to the Grand Pitch, a waterfall on the East Branch of the Penobscot supported by more resistant beds of the formation.

Resistant beds like these.

If you've taken a historical geology class in North America, you've probably spent some time with the assembly of eastern North America. Back when I was taking that class, it was a three-stage process marked by the Taconic, Acadian, and Alleghanian (or Appalachian) mountain-building events (orogenies). Well, as you might guess, it's a bit more complicated than that. (Just a bit.) In actual practice, the North American craton, microplates, continental fragments, island arcs, and all and sundry were bumping and jostling and colliding with each other all the time. In the present example, the Grand Pitch Formation was deposited not in North America, but on a Gondwanan terrane known as Ganderia (or Gander) that eventually piled up on the continent after a series of its own adventures (including running into another terrane) (Neuman and Max 1989).

Just like our slice of the Equator in Minnesota, here in Maine you can stand on a former sliver of the tropics.

The Grand Pitch Formation is a heterogeneous unit, including beds of gray, green, and red siltstone and slate, quartzite, and minor amounts of graywacke and tuff (Neuman 1967). Siltstone and slate are charming lithologies but are not noted for resistance to weathering; instead, the falls are supported by quartzite beds. The depositional environment has been interpreted as a continental slope-rise setting (Wellensiek et al. 1990).

Finer-grained beds as seen at the surface: not recommended for load-bearing outcrops.

It's a pretty thick formation, encompassing at least 1,500 m (5,000 ft) (Neuman 1967), but it's not in mint condition, to say the least. The formation has undergone several episodes of deformation, going back to the Ganderia days with a Cambrian–Ordovician event termed the Penobscot Orogeny or Disturbance (Neuman and Max 1989).

Red and gray beds make it easy to see minor faulting here.

The age of the Grand Pitch Formation is not entirely clear. Only one kind of fossil has ever been reported from it, the invertebrate trace fossil Oldhamia, which looks kind of like a fireworks burst or a palm frond and is thought to have been produced by something "mining" beneath microbial mats (Seilacher et al. 2005). Oldhamia was most abundant in the early Cambrian, but is not limited to that time frame, nor does its occasional presence mean the entire Grand Pitch Formation has to be that age, either (Neuman 1962, 1967). Generally the formation is attributed to some interval of the Cambrian.

Going back to deformations and alterations, here we have a patch of the formation scored with glacial striations.

References

Neuman, R. B. 1962. The Grand Pitch Formation: new name for the Grand Falls Formation (Cambrian?) in northeastern Maine. American Journal of Science, series 5, 260:794–797.

Neuman, R. B. 1967. Bedrock geology of the Shin Pond and Stacyville quadrangles, Penobscot County, Maine. U.S. Geological Survey, Washington, D.C. Professional Paper 524-I.

Neuman, R. B., and M. D. Max. 1989. Penobscottian-Grampian-Finnmarkian orogenies as indicators of terrane linkages. Pages 31–45 in R. D. Dallmeyer, editor. Terranes in the circum-Atlantic Paleozoic orogens. Geological Society of America, Boulder, Colorado. Special Paper 230.

Ruedemann, R., and E. S. C. Smith. 1935. The Ordovician in Maine. American Journal of Science, series 5, 30:353–355.

Seilacher, A., L. A. Buatois, and M. G. Mángano. 2005. Trace fossils in the Ediacaran–Cambrian transition: behavioral diversification, ecological turnover and environmental shift. Palaeogeography Palaeoclimatology Palaeoecology 227(4):323–356.

Wellensiek, M. R., B. A. van der Phijm, R. Van der Voo, and R. J. E. Johnson. 1990. Tectonic history of the Lunksoos composite terrane in the Maine Appalachians. Tectonics 9(4):719–734.

Sunday, February 13, 2022

Your Friends The Titanosaurs: Abditosaurus kuehnei

Today we add Abditosaurus kuehnei to the long-running "Your Friends The Titanosaurs" series. January was pretty slow around here as far as new non-avian dinosaurs go, but coincidentally enough the dinosaur to break the dry spell was a titanosaur. Since then, we've also gotten Guemesia ochoai, an abelisaurid, which is very nice if you enjoy theropods. (It did make entry #1600 in the dinosaur sheet of The Compact Thescelosaurus.)

Genus and Species: Abditosaurus kuehnei. "Abditus" is Latin for "concealed", referring to the long gap between discovery and description, making this a comrade of our friend Thescelosaurus neglectus. "Kuehnei" honors the discoverer, Walter Georg Kühne (Vila et al. 2022). Together we get something like "Walter Georg Kühne's concealed lizard".

Citation: Vila, B., A. Sellés, M. Moreno-Azanza, N. L. Razzolini, A. Gil-Delgado, J. Canudo, and A. Galobart. 2022. A titanosaurian sauropod with Gondwanan affinities in the latest Cretaceous of Europe. Nature Ecology & Evolution. doi:10.1038/s41559-021-01651-5.

Stratigraphy and Geography: The type and only known specimen comes from the lower Conques Formation at a locality identified as Orcau-1 (also known as "Barranco de Orcau" or "Orcau"). This location is about 6 km (4 mi) east of Tremp, in the county of Pallars Jussà, Catalonia, Spain (Vila et al. 2022).

Holotype: The holotype is not catalogued as a unitary specimen. Instead, the bones are held at the Museo Nacional de Ciencias Naturales in Madrid (MNCN) and the Museu de la Conca Dellà in Isona (MCD) and catalogued under a variety of numbers. The bones pertain to an associated and semi-articulated partial skeleton found over an area about 6 m by 4 m (20 ft by 13 ft) and include: isolated teeth, 12 partial articulated cervical vertebrae, 7 anterior and middle dorsals, cervical and dorsal ribs, 3 chevrons, the right and partial left scapula, right coracoid, left sternal plate, a sternal rib (a titanosaurian rarity), a fragment of the left ilium, parts of both humeri, partial right radius, part of the right femur, the right tibia and fibula, and partial left fibula with attached calcaneum (another titanosaurian rarity). Some other material has gone missing (Vila et al. 2022).

Abditosaurus kuehnei, as its name suggests, is one of those dinosaurs that was not described until decades after it had been discovered. The history of the specimen is described in the supplementary information to the paper (here; ten times longer than the paper, so yeah, necessary stuff!). The abridged Abditosaurus story is that Kühne discovered the fossils September 25, 1954 while prospecting for Cretaceous mammals. Over the next couple of weeks he collected a few bones and jacketed a few more for later collection. He made a return trip in 1955 and collected more bones. Plans for additional collection were scuppered by lack of funds. Lapparent and Aguirre (1956) proposed that Kühne's sauropod was a new species of Hypselosaurus, which is what you did in 1956. The locality was revisited in the mid-1980s, but not fully collected until a series of expeditions 2012–2014 (Vila et al. 2022 supplementary information).

A few anatomical notes: The humerus is notably robust while the tibia is gracile. The ilium is pneumatized. There are several osteological indications of age, such as the presence of a sternal rib and a calcaneum, thought to have only ossified with great age (Vila et al. 2022). (Also, the cervical ribs are fused to their vertebrae.) In the supplementary information Vila et al. describe osteological samples from the limb bones that indicate the type individual had reached skeletal senility (histological ontogenetic stage HOS-14). Vila et al. estimated that the sauropod was 17.5 m (57.4 ft) long and a shade more than 14 metric tons (15.4 US tons) in body mass. These figures would make A. kuehnei somewhat larger than a typical titanosaur, and definitely larger than your typical subcompact European titanosaur.

The size of A. kuehnei is one of the major talking points. Along with its lengthy history, this species comes equipped with a full suite of implications. While titanosaurs seem to be big fans of some kind of phylogenetic uncertainty principle, in this case A. kuehnei shows no indication of clading with other European titanosaurs. Instead, it hangs out in the general vicinity of saltasaurs and its phylogenetic best friend appears to be the even larger Paralititan stromeri from the Cenomanian of Egypt. Vila et al. (2022) posited a scenario in which North African titanosaurs arrived in Ibero-Amorica during an early Maastrichtian marine lowstand via a loop through the various smaller landmasses then dotting the narrow Tethys Ocean. They tied this to an early Maastrichtian faunal turnover in which the previous mini-titanosaurs were replaced, and suggested something similar happened in Romania. Let the fossil record show that large(ish) titanosaurs in the Haţeg Basin fauna of Romania have been reported by Le Loeuff (2005), Stein et al. (2010), and Mannion et al. (2019).

I've mentioned this before, but I suspect that sauropods were excellent at dispersal over water, similar to elephants. They were big, full of air and fermenting plant gases, and had long necks that could have been held well above the water. Get 'em out to sea, and they could probably have gone a long way. Postulate that your traveling sauropod was a gravid female, and given what we know about the number of eggs a sauropod could lay, you've got a pretty good scenario for populating any landmass that was large enough to support sauropods and a reasonable distance from a landmass that already had sauropods.

References

Lapparent, A. F., and E. Aguirre. 1956. Présence de dinosauriens dans le Crétacé supérieur du bassin de Tremp (province de Lérida, Espagne). Comptes Rendus Sommaires de la Société Geólogique de France 14:261–262.

Le Loeuff, J. 2005. Romanian Late Cretaceous dinosaurs: big dwarfs or small giants? Historical Biology 17:15–17.

Mannion, P., V. Díez Díaz, Z. Ciski-Sava, P. Upchurch, and A. Cuff. 2019. Dwarfs among giants: resolving the systematics of the titanosaurian sauropod dinosaurs from the latest Cretaceous of Romania. Journal of Vertebrate Paleontology, Program and Abstracts, 2019:148.

Stein, K., Z. Csiki, K. Curry Rogers, D. B. Weishampel, R. Redelstorff, J. L. Carballidoa, and P. M. Sandera. 2010. Small body size and extreme cortical bone remodeling indicate phyletic dwarfism in Magyarosaurus dacus (Sauropoda: Titanosauria). Proceedings of the National Academy of Sciences of the United States of America 107(20):9258–9263.

Vila, B., A. Sellés, M. Moreno-Azanza, N. L. Razzolini, A. Gil-Delgado, J. Canudo, and A. Galobart. 2022. A titanosaurian sauropod with Gondwanan affinities in the latest Cretaceous of Europe. Nature Ecology & Evolution. doi:10.1038/s41559-021-01651-5.

Sunday, February 6, 2022

Send in the nautiloids: Early Ordovician fossils of the National Park Service

Previously we looked at the National Park Service records of the late Cambrian and Late Ordovician. What comes between the late Cambrian and Late Ordovician? That's right, the Early Ordovician. (The Middle Ordovician also does, but at the moment I've got Early on my mind. You know, in North America it might actually be more practical to divide the period into Early and Late, based on the lowstand that separates the Sauk Sequence from the Tippecanoe Sequence; or, maybe not. Who knows? You start to think about things like that when contemplating the divisions of the geologic time scale; where would the lines have been placed if it had been initially developed somewhere other than northwestern Europe?)

The Early Ordovician is kind of a transitional episode; in some ways, it's like a tag to the end of the Cambrian, considering it's the wind-down of the Sauk Sequence. I get the feeling that this epoch was not necessarily the most pleasant 15 or so million years in North America, at least in some areas. For example, in the Upper Midwest the Early Ordovician is represented by our old friend the Prairie du Chien Group. The PdC was certainly not bereft of life, but a whole lot of that life was stromatolite-building cyanobacteria, and a general rule of thumb is that any non-Precambrian geologic unit that features intervals of wall-to-wall stromatolites was probably not that hospitable while being deposited. Otherwise, the groups most commonly reported from Lower Ordovician rocks in NPS areas are brachiopods, nautiloids, gastropods, trilobites, graptolites, and conodonts. Apart from the nautiloids, you might think you were back in the late Cambrian. The evolutionary flowering that is evident in Middle and especially Upper Ordovician rocks was just kind of simmering: mollusks and echinoderms were chugging (although a lot of those early echinoderms didn't catch on), but corals and bryozoans were in low gear.

By my count, as many as 15 NPS units and affiliated areas have fossiliferous Lower Ordovician rocks, although the records at several of these units are not known to be particularly impressive at this time. Four of the parks are represented by the good old PdC, with fossils at Effigy Mounds NM, MNRRA, Saint Croix National Scenic Riverway, and potentially one of the units of NPS-affiliated Ice Age National Scientific Reserve. The distribution is a decent match for Early Ordovician finds in the United States as a whole (compare to the Early Ordovician records in the Paleobiology Database, for example). The major holes are New Mexico/Oklahoma/Texas, the Hudson River Valley, and Utah; none of Utah's NPS units includes a classic Ibexian sequence, but Great Basin NP next door in Nevada is Ibexian-adjacent and no slouch itself. It hosts one of the more interesting Early Ordovician fossil records in the NPS, along with Chesapeake and Ohio Canal National Historical Park, Death Valley NP, and Pictured Rocks National Lakeshore.

As usual, click to embiggen. Our Early Ordovician parks are 1) Death Valley NP; 2) Great Basin NP; 3) Kobuk Valley NP; 4) Denali NP & Preserve; 5) Yukon-Charley Rivers NPres; 6) Wind Cave NP; 7) Mississippi National River and Recreation Area; 8) Saint Croix National Scenic Riverway; 9) Picture Rocks National Lakeshore; 10) Ice Age National Scientific Reserve (affiliated area); 11) Effigy Mounds NM; 12) Ozark National Scenic River; 13) Buffalo National Scenic River; 14) Great Smoky Mountains NP; 15) Chesapeake and Ohio Canal National Historical Park.

Chesapeake and Ohio Canal NHP preserves good examples of the standard Early Ordovician assemblage in the Stonehenge Limestone and overlying Rockdale Run Formation. The Early Ordovician of both Death Valley NP and Great Basin NP is represented by rocks of the Pogonip Group, although different formations are present at the two parks. (When considering Paleozoic paleontology, if Death Valley or Yukon-Charley Rivers don't have something, it might not be present in the NPS. In this case Death Valley has the better record.) Great Basin is distinguished for examples of some of the wacky echinoderms that proliferated during the Ordovician. Pictured Rocks National Lakeshore is noted for the oldest NPS vertebrate material (I reserve the right to be cagy about the exact placement of conodonts), consisting of armor attributed to Anatolepis (Miller et al. 2006; a pteraspidomorph, or ostracoderm in more old-timey lingo). Pictured Rocks, incidentally, has an interesting unresolved stratigraphic issue: the above specimens came from the Au Train Formation and were associated with other microfossils of Early Ordovician age (Miller et al. 2006). However, a dissertation (Oetking 1952) documented Au Train macrofossils from the lakeshore area that appear to be correlative to Platteville fossils (i.e., Late Ordovician). This all suggests to me that either the identifications of Oetking's fossils are overly generous, or that the rocks identified as the Au Train Formation are more complex than currently suspected (a cryptic unconformity, etc.).

References

Miller, J. F., R. L. Ethington, and R. Rosé. 2006. Stratigraphic implications of Lower Ordovician conodonts from the Munising and Au Train Formations at Pictured Rocks National Lakeshore, Upper Peninsula of Michigan. Palaios 21:227–237.

Oetking, P. F. 1952. The relation of the Lower Paleozoic to the older rocks in the northern peninsula of Michigan. Dissertation. University of Wisconsin, Madison, Wisconsin.

Sunday, January 23, 2022

Bruce Erickson

This week saw the end of an era in Minnesota paleontology with the passing of Bruce Erickson. Bruce had been the curator of paleontology at the Science Museum of Minnesota from 1959 to 2017, where he was most famous for his work on the Paleocene fossils of Wannagan Creek. Much of his research was on crocodilians (several examples of which were featured in this post), but he also worked on many other topics, including the dinosaurs of the Poison Creek Quarry (Morrison Formation), champsosaurs, and turtles. Examples of many of these fossils can be seen in the paleontology exhibit area of the Science Museum, which includes a Wannagan Creek section (one of the few large Paleocene exhibits you'll find in a museum), several Morrison dinosaurs, and an enormous Triceratops (a composite of two partial skeletons he collected early in his tenure). If you'd like to know more, many of his publications and other paleontological publications from Science Museum collaborators can be downloaded here.

Sunday, January 16, 2022

Passing thoughts on Struthiosaurus (and Silvisaurus!)

I saw the headline "Surprising Dinosaur Discovery: Ankylosaur Was Sluggish And Deaf" and was indeed surprised, not so much by the "sluggish" part but by the "deaf" part. Hearing is generally pretty lightweight in terms of anatomical investment and it's useful wherever there is a medium to communicate sound. Even snakes can perceive sounds via vibrations. We're not talking about something like flight, a costly adaptation that requires a body specifically dedicated for it. It's not difficult to understand why, in the absence of natural pressure to maintain it, many lineages of birds have become flightless on islands. Hearing, though... I was having trouble coming up with a selective scenario that would eliminate it. So I thought I'd have a look at the actual paper (Schade et al. 2022).

...And it turned out the headline overstated things. Schade et al. (2022) described the holotype braincase of the diminutive Late Cretaceous European nodosaur Struthiosaurus austriacus. As part of their study, they measured the areas of the braincase associated with hearing. They calculated the mean hearing frequency as 1230 Hz and the bandwidth as between 296 and 2164 Hz. For the musicians among us, that works out to keys 42 (D above middle C) to 76 (double high C), centered just below key 67. Judging by a helpful chart on Wikipedia, this range is comparable to that of a chicken. [Update, 2022/01/17: Lead author Marco Schade has sent me an article, Hill et al. 2014, that shows chickens have a wider hearing range: 9.1 Hz to 7.2 kHz at 60 dB. This honestly makes more sense than the Wiki range, which seemed pretty constricted for a bird. The next closest match on the chart is the bullfrog, provided of course that the range is accurate; Heffner and Heffner 2007 give a slightly more constricted range than the Wiki chart, of 100 Hz to 2.5 kHz.] Schade et al. also commented that "the auditory acuity of S. austriacus seems somewhat superior to that of turtles". Thus, the paper did not find S. austriacus to be deaf, although it appears that they did not enjoy an especially rich range of sounds. [2022/01/20: To be completely fair to the headline writers, there seems to have been some difficulty with the German word "schwerhörig", which as Schade informed me means something like "barely able to hear".] (We must of course remember that this is one braincase, and it's possible that we happened to have stumbled on one individual with poor auditory capabilities, violating our unspoken assumption that fossilized organisms tend to the average rather than the extremes. More braincases would help to tell.)

 Struthiosaurus austriacus, the perfect nodosaur for around the house. Just don't call for it in a low-pitched voice. Figure 1 from Schade et al. (2022) (which see for full caption). CC BY 4.0.

There is also an intriguing counterpoint featuring the somewhat larger and earlier North American nodosaur Silvisaurus condrayi. In the original description (Eaton 1960), Eaton noted the presence of inflated nasal sinuses, which he interpreted as resonating chambers. With a diameter of approximately 50 mm (2 in), the chambers were postulated to have produced a sound "about E or F four octaves above middle C". This is surprisingly high-pitched, at keys 101 or 102 on an extended piano, or 5274.041 or 5587.652 Hz. (In fact, it's so high-pitched something doesn't seem right. Either Eaton or I have misinterpreted something in the sound physics, those aren't resonating chambers, or Silvisaurus went through life projecting the majestic sound of tinnitus.) Either would be well beyond the postulated hearing range of S. austriacus.

This all still leaves room to play with that original headline. How could we get a lineage of deaf nodosaurs? It has been suggested that snakes have reduced auditory capabilities because they evolved from burrowing ancestors. This doesn't seem especially feasible for nodosaurs; if nothing else they would have lost their spikes and plates long before their hearing had they been doing serious full-body burrowing. There's another possibility, though: S. austriacus is thought to have been an island endemic. If the founding population included an individual with reduced auditory capabilities, and that individual contributed disproportionately to the gene pool, we have a route for this trait becoming prevalent in at least this population of nodosaurs. A similar phenomenon could happen later in the island population's history as well, although it would be more difficult for any one mutation to spread with a larger population. Unfortunately, it would be very difficult to test this hypothesis without a whole lot of braincases from multiple stratigraphic horizons.

References

Eaton, T. H., Jr. 1960. A new armored dinosaur from the Cretaceous of Kansas. The University of Kansas Paleontological Contributions: Vertebrata 8:1–24.

Heffner, H. E., and R. S. Heffner. 2007. Hearing ranges of laboratory animals. Journal of the American Association for Laboratory Animal Science 46(1):20–22.

Hill, E. M., G. Koay, R. S. Heffner, and H. E. Heffner. 2014. Audiogram of the chicken (Gallus gallus domesticus) from 2Hz to 9 kHz. Journal of Comparative Physiology A 200:863–870.

Schade, M., S. Stumpf, J. Kriwet, C. Kettler, and C. Pfaff. 2022. Neuroanatomy of the nodosaurid Struthiosaurus austriacus (Dinosauria: Thyreophora) supports potential ecological differentiations within Ankylosauria. Scientific Reports 12:article 144. doi:10.1038/s41598-021-03599-9.