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.
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| Unrelated: Rare miniature boreal sauropods. This unnamed taxon is also notable for its unusual osteoderms and short tail with well-developed caudofemoralis muscles. |
As we close in on the end of the alphabet, we drop by Brazil for the last time (for now) for a double feature (Trigonosaurus pricei and Uberabatitan ribeiroi), then head over to Madagascar for Vahiny depereti. Oddly enough, we've already had the last entry from Argentina.
Meridian Hill Park is one of the subunits of Rock Creek Park, in Washington, D.C., having joined it in 1910. It is a roughly rectangular parcel bounded on the north by Euclid Street NW, on the east by 15th Street NW, on the south by W Street NW (which is replaced by Florida Avenue west of the park), and on the west by 16th Street NW. The park gets its name from a geographic marker placed on the hill by Thomas Jefferson in 1804 to indicate the location of a longitudinal meridian (the White House Meridian). This marker no longer exists, but the name remains. The genesis of the park goes back to Mary Foote Henderson, who after unsuccessfully proposing the tract including the park as a site for a new White House, began the process of turning the tract into a public city park in the early 1900s.
Before there was a park, there had been an extensive outcrop of the mid-Cretaceous Potomac Group and overlying Cenozoic terrace deposits along 16th Street. It is mentioned at least as far back as Rogers (1875), which is also of interest for discussing the ubiquitous Skolithos-bearing cobbles of the Potomac region. Rogers described the exposure as showing the contact of underlying sandstone and overlying unconsolidated deposits, but noted that this had been obscured by grading and excavation after his visit in April 1875. The "Columbian College" mentioned in his description is what is now known as George Washington University, then located at Meridian Hill. Logically enough the site became known as the Sixteenth Street exposure in the literature. It didn't have much longer to last.
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| Cross-bedding in the exposure (Darton 1896). |
The Sixteenth Street outcrop was investigated in detail during the 1890s by Lester Ward, William Fontaine, and other geologists (Ward et al. 1905). A stratigraphic section was taken at the site in May and June 1894, shortly before the outcrop was fully obscured (Ward et al. 1905:382–387). Beginning north of the intersection with Florida Avenue at the southwest corner of what is now the park, they recorded approximately 40 ft (12 m) of Potomac "Formation" rocks, composed of 25 ft (8 m) of cross-bedded sandstone followed by 15 ft (5 m) of clay, overlain by 20 ft (6 m) of stratified gravel and clay attributed to the Lafayette Formation, and a 5-ft (1.5-m)-thick cap of boulder clay at the crest of the hill. The upper Potomac clay proved to be paleobotanically productive. The geologists made a couple of collections in spring and summer 1893 (Ward et al. 1905:516). The plant fossils were found in clay rip-ups, indicating they had been reworked from an older part of the Potomac. Fontaine identified the conifers Athrotaxopsis tenuicaulis (sometimes spelled Arthrotaxopsis), Nageiopsis angustifolia, and Podozamites distantinervis (then thought to be a cycad), and the fern Thrysopteris angustifolia.
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Here's another photo, this one from Ward et al. (1905). The composition
is kind of odd, with the building just peeking over the top of the
exposure. |
The outcrop on 16th Street has generally been hidden since the 1890s, but during work for improvements to the newly created park in the early 20th century, some access was possible. Sinnott and Bartlett (1916) described plant fossils collected during an episode of access. They described the geology at their spot as the Patuxent Formation (part of the Potomac) beneath the Lafayette Formation. The Patuxent Formation outcrop they accessed included 5 ft (1.5 m) green sandy clay beneath 3 ft (1 m) of lignite-rich clay with leaf impressions. The plant fossils included charcoal, cones, poorly preserved foliage, and lignified logs. As identified by the paleobotanist Edward Berry, the foliage represented essentially the same taxa as identified by Fontaine: the conifers Athrotaxopsis grandis, Nageiopsis angustifolia, and Podozamites distantinervis, and the fern Onychiopsis psilotoides (Thrysopteris angustifolia is a synonym). The logs included examples of the conifers Podocarpoxylon mcgeei and new species Paracupressinoxylon potomacense. Interestingly, unlike the reworked foliage described by Ward et al. (1905), Sinnott and Bartlett (1916) thought the logs were likely buried in place.
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| Slides of Paracupressinoxylon potomacense from Sinnott and Bartlett (1916). 13, 14, and 18 are radial sections, 15 is a tangential section, and 16 and 17 are transverse sections. |
Unfortunately, Sinnott and Bartlett did not specify what they based their new species on, so it is not clear if their type specimen (or specimens) came from Meridian Hill or a second locality, a paleobotanically productive deep excavation for Central High School (now the Cardozo Education Campus) a few blocks east. Nor did they specify anything else about the disposition of their fossils. Apparently their work was done at the Bussey Institution of Harvard and the USDA’s Bureau of Plant Industry, but Sinnott was based out of the Connecticut Agricultural College (now the University of Connecticut) and Bartlett was based out of the University of Michigan. When I was doing some research on the site a few years ago, I sent queries to several institutions, only to find that Harvard, the University of Connecticut, and the University of Michigan do not appear to have their material. (Also checked a bunch of museum databases, since why not. No dice.) I am not sure if the thin sections would have survived to the present, or would be informative or recognizable if they have survived. For that matter, the taxon Paracupressinoxylon potomacense has scarcely been used since 1916. I guess you can name something, but that doesn't mean anyone else has to notice.
References
Darton, N. H. 1896. Artesian-well prospects in the Atlantic Coastal Plain region. U.S. Geological Survey, Washington, D.C. Bulletin 138.
Rogers, W. B. 1875. Geological notes. Article II: On the gravel and cobble-stone deposits of Virginia and the Middle States. Proceedings of the Boston Society of Natural History 18:101–106.
Sinnott, E. W., and H. H. Bartlett. 1916. Coniferous woods of the Potomac Formation. American Journal of Science (4th series) 41(243):276–293.
Ward, L. F., W. M. Fontaine, A. B. Bibbins, and G. R. Wieland. 1905. Status of the Mesozoic floras of the United States. U.S. Geological Survey, Washington, D.C. Monograph 48. Text, plates.
My original plan was to cover Titanosaurus indicus plus the seven species that hadn't been otherwise included; overstuffed for Thanksgiving, if you like. After 4,500 words, not counting the 46 references, I thought that might be a little too overstuffed. So, I've decided to split the post in two. Today covers just T. indicus and the three other dubious species from India or Madagascar ("T." blanfordi, "T." madagascariensis, and "T." rahioliensis). Later this week, I'll put up the other half, which will take us to Argentina ("T." nanus), England ("T." lydekkeri and "T." valdensis), and Laos ("T." falloti). As usual, house rules apply: indeterminate species have gone back to their original genus and get quotation marks.
A few general remarks before we get started: Titanosaurus is notorious for the numerous far-flung species that have been attached to it (Wilson and Upchurch 2003). We've already seen the cream of the crop, the species which are still
considered to be valid or potentially valid, albeit under different genera:
Titanosaurus australis (Neuquensaurus), Titanosaurus colberti (Isisaurus), Titanosaurus dacus (Magyarosaurus), and Titanosaurus robustus (Neuquensaurus), plus Laplatasaurus araukanicus, which has sometimes been considered a species of Titanosaurus (e.g., Powell 2003). Let us not forget
Titanosaurus montanus
either, although technically it doesn't count because it was supposed to be a
different genus; O. C. Marsh just came up with the idea of naming a sauropod
Titanosaurus the same year that Richard Lydekker did. Anyway, this
leaves us with the type species T. indicus and seven dubious species,
not all of which are necessarily even titanosaurs. This doesn't get into another pool of fossils identified as Titanosaurus sp., but these are being left out here. If you'd like to delve into those, Wilson and Upchurch (2003) also address them. (One of the examples they address, also known as DGM Series C, later became Baurutitan britoi.)
Why were so many species attributed to Titanosaurus? My guess is there were several factors. First, paleontologists of the 19th century and early 20th century were more apt to add new species to existing genera than paleontologists today. Second, there wasn't much known about sauropods at the time, and almost all of what was known pertained to North American Jurassic sauropods. Third, Titanosaurus indicus is a blank canvas. Outside of characteristics that are now known to be widely distributed among titanosaurs, such as procoelous caudals, there wasn't much to define it. The great majority of the other Titanosaurus species are based on pretty scrappy material. Once the ball got rolling, the definition of Titanosaurus began to stretch and grow to accommodate the various new species, creating a positive feedback loop.
Recently I've been doing some work with geological stratotypes in National Park Service areas. The naming of geological formations is not unlike naming a fossil species of organism (or living species for that matter), except the type locality is also the type "specimen", and you don't dig up the type locality and put it in a museum (although you could certainly take a core). Anyway, there are a few stratotypes located within Mississippi National River and Recreation Area. I've alluded a couple of times to the type locality of the St. Peter Sandstone being the bluff under Fort Snelling. This locality is no longer accessible due to protective measures, but the formation *is* exposed in the immediate vicinity. The type locality of the Hidden Falls Member of the Platteville is in Hidden Falls Park (Sloan 1956). Sloan didn't state specifically where, but I have a pretty good idea. Finally, there are two units named from the section exposed at Lock and Dam No. 1.
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Beautiful exposure, even if you can't climb around on it. |
The Twin Cities Basin is just a small part of the area where the St.
Peter–Glenwood–Platteville–Decorah sequence is exposed, and across this area,
the rocks differ and the names differ. Reconciling nomenclature across states
is part of what Mossler (2008) was about. An example of outstate attention on
the Twin Cities Basin is Templeton and Willman (1963), from the Illinois Geological Survey. This publication brings
the Illinois nomenclature into the Twin Cities, via a section at Lock and Dam
No. 1 (p. 226–227). If you're used to the local names, the Lock and Dam
section requires a lot of translation. For example, the Platteville is
considered a group, divided into three formations and nine members. The
Templeton and Willman nomenclature has not taken off in Minnesota, which has
preferred a simpler system, and I can't say I disagree. It seems like overkill to pack that many formal divisions into about 9 vertical meters (30
ft), many of which are not visually distinguishable at a distance of a few meters. Their divisions of the transition from the St. Peter to the
Platteville are another matter.
Beginning with our old friend the Pecatonica and going down, Templeton and Willman (1963) divided the Lock and Dam rocks into the Chana Member and Hennepin Member of the Pecatonica Formation (Platteville Group), the Harmony Hill Member and Nokomis Member of the Glenwood Formation, and the St. Peter Sandstone. Two of these members were named from this section: the Hennepin Member and Nokomis Member. In turn:
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| My initial thoughts. Arrows point to the approximate center of the named unit, so I don't have to commit to contacts like the coward and cad I am. The scale boxes are *very* rough; I was able to put a scale bar on the outer wall, but this is some distance back, so prefer a larger number and don't take it too seriously. |
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| ...Or is this what Templeton and Willman intended? Might be easier if I could get closer. |
The Chana Member, 28 cm thick (11 in), is basically what we recognize as the Pecatonica;
The Hennepin Member is 69 cm (27 in) thick, divided into three parts: 46 cm (18 in) of clay-rich greenish-gray limestone, and green shale, over 15 cm (6 in) of clay-rich greenish-gray slightly sandy limestone, over 8 cm (3 in) of brown dolomitic sandstone (Templeton and Willman 1963). This unit, or at least the upper part of it, can be easily distinguished visually beneath the blocky overlying rocks (pers. obs.; see also the photos at the end of this post—areas that look white are weathered). The other two parts I'm not as sure about. The Hennepin Member should be thicker than the Chana and the underlying Harmony Hill put together, but from my photos and observations, I see four distinct units over whitish sandstone. Three of them seem fairly similar in thickness: the classic Minnesota Pecatonica, a light-colored recessive unit, and a greenish-brown recessive unit. Below them is a thinner, even more recessive yellow-brown unit. My first thought was that the greenish recessive unit was the Harmony Hill Member, but if I put it in the Hennepin Member and assume that the 15 cm and 8 cm beds of Templeton and Willman (1963) are both included in it, we get something much closer to the overall relative thicknesses T&W found for the Hennepin versus the Chana. Plus, the underlying thin yellow-brown interval looks to be closer to their description of the Harmony Hill Member. The internal proportions are still out of whack, though (three roughly equal units in photos versus 28 cm over 46 cm over 15+8 cm in the publication). (In case you were wondering, there is a grand total of zero [0] photos of outcrops in T&W '63, which is regrettable. A single decent photo with a couple of arrows would have helped immensely.) At any rate, the Hennepin Member is more shaley than the description in T&W '63 implies, or, rather, is less carbonate-rich (Mossler 2008). The Minnesota Geological Survey regards it as the upper part of the Glenwood Formation, rather than the basal part of the Platteville (Mossler 2008);
The Harmony Hill Member is 23 cm (9 in) of yellow-green shale (Templeton and Willman 1963);
The Nokomis Member is also tricky. Templeton and Willman (1963) described it as
330 cm (110 in) thick, divided into 10 to 18 cm (4 to 7 in) of silty white
sandstone, over 58 cm (23 in) of very silty, greenish-buff to red-brown,
thin-bedded, partly ferruginous sandstone, over 224 cm (78 in) of very silty
white to yellow-buff sandstone. Mossler (2008) noted that an interval of silty
sand is commonly found in Minnesota between standard Glenwood and standard St.
Peter, and this interval has frequently been included in the Glenwood. (The Glenwood is a bigger deal outside of Minnesota.) However, this
interval is difficult to distinguish from standard St. Peter in well logs and
natural gamma logs, so for practical purposes Mossler (2008) recommended including it in the St. Peter.
It is also difficult to identify a difference just by looking at the
outcrop from the vantage point of the landing. The best I can do is identify a couple of
slope breaks that may indicate changes in mineralogy which are not otherwise
apparent from color or bedding at that distance. A contact in the vicinity of the lower slope break would give a thickness in the vicinity of the quoted figure.
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The breaks are easier to see in oblique view than straight on. Note also how
plants like to colonize the Glenwood–upper Nokomis interval. |
References
Mossler, J. H. 2008. Paleozoic stratigraphic nomenclature for Minnesota. Minnesota Geological Survey, St. Paul, Minnesota. Report of Investigations 65.
Sloan, R. E. 1956. Hidden Falls Member of Platteville Formation, Minnesota. Bulletin of the American Association of Petroleum Geologists 40(12):2955–2956.
Templeton, J. S., and H. B. Willman. 1963.
Champlainian Series (Middle Ordovician) in Illinois. Illinois Geological Survey, Champaign, Illinois. Bulletin 89. [large
file]
No sooner do I announce that Titanosaurus is up next for the titanosaurs than a couple of gate-crashers show up to butt in line: Bravasaurus arrierosorum and Punatitan coughlini. These two taxa were described in the same paper (Hechenleitner et al. 2020) and from the same locality (Quebrada de Santo Domingo) and stratigraphic unit (Ciénaga del Río Huaco Formation), albeit from different levels. They are from Argentina, but not Patagonia; instead, they are from the western, Andean part of the northwestern province of La Rioja, becoming the first named titanosaurs from this province. They are also the first titanosaurs named from the Ciénaga del Río Huaco Formation. The age of this formation has not yet been tightly constrained but is regarded as Campanian–Maastrichtian. In addition to the titanosaur bones, at least three laterally extensive horizons of eggs attributed to titanosaurs were found, between the two bone-bearing levels.
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| Part of Figure 1 from Hechenleitner et al. (2020), featuring reconstructions of Punatitan coughlini (c) and Bravasaurus arrierosorum (d), with red highlights showing known fossils (scale bar = 1 m). CC-BY-4.0. |
Hyolith relationships and paleobiology continue to be active research topics, which isn't bad for animals that had their heyday more than 500 million years ago and are primarily known from diminutive shells. Let's get right down to the issue that has haunted study of Hyolitha, as posed in the title of Smith (2020): "Finding a home for hyoliths". For a couple of years recently, they'd been drifting into the welcoming arms of brachiopods and other lophophores (Moysiuk et al. 2017; Sun et al. 2018), as discussed in previous entries. However, cracks quickly began to emerge. A group of authors has published several papers challenging a close relationship with lophophores, instead emphasizing shell structural similarities with mollusks (Li et al. 2019, 2020) or being a bit more conservative and placing them nearer the base of Lophotrochozoa (lophophores, annelid worms, mollusks, etc.; Liu et al. 2020a).
Liu et al. (2020a) questioned the evidence presented by Moysiuk et al. (2017) and Sun et al. (2018). Liu et al. interpreted the putative pedicles of Sun et al. (2018) as crushing of the tip of the shell, with no evidence for a pedicle or an opening for one in intact hyolith shells. They concurred with Moysiuk et al. (2017) that hyoliths had a tentaculate feeding structure, but they did not regard this as homologous with a true lophophore. Smith (2020), in a commentary on Liu et al (2020a), illustrated two potential options: that hyoliths are closer to the mollusks and annelids, in which case the tentaculate feeding apparatuses of hyoliths and lophophores are not related but shells are an ancestral trait of lophotrochozoans (which also means that the Cambrian record of these groups is more complete than otherwise thought); or that hyoliths are closer to brachiopods, making the shell something that appears multiple times while limiting the tentaculate apparatus to the brachiopod line. (I suppose there could be an option where shells are ancestral *and* the hyolith tentacles are related to the lophophore feeding structure, but this wasn't explored.)
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| Dueling options for hyolith relationships, from Smith (2020). CC-BY-4.0. |
Another area of interest in recent years has been the feeding methods and internal anatomy, bolstered by Cambrian fossils with soft tissue traces. Liu et al. (2020a, 2020b) have documented a tentaculate feeding apparatus in a second hyolith genus, the orthothecid Triplicatella. This hyolith had a more "tuft"-like array of tentacles than the broader "gull-wing" spread of the hyolithid Haplophrentis, and like other orthothecids did not have helens (long curved rods; see Skovsted et al. 2020 for the latest on helens). Liu et al. proposed that Triplicatella was not a filter/suspension feeder, as proposed for Haplophrentis, but was instead a stationary deposit feeder, indicating distinct lifestyles for the orthothecid and hyolithid orders of hyoliths.
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| Interpretation of the internal anatomy of Triplicatella, an orthothecid (so no helens; compare to Figure 7 in Liu et al. 2020c). Figure 8 in Liu et al. (2020b). CC-BY-4.0. |
References
Li, L., X. Zhang, C. B. Skovsted, H. Yun, B. Pan, and G. Li. 2019. Homologous shell microstructures in Cambrian hyoliths and molluscs. Palaeontology 62(4):515–532. doi:10.1111/pala.12406.
Li, L., C. B. Skovsted, H. Yun, M. J. Betts, and X. Zhang. 2020. New insight into the soft anatomy and shell microstructures of early Cambrian orthothecids (Hyolitha). Proceedings of the Royal Society B 287(1933):20201467. doi:10.1098/rspb.2020.1467.
Liu, F., C. B. Skovsted, T. P. Topper, Z. Zhang, and D. Shu. 2020a. Are hyoliths Palaeozoic lophophorates? National Science Review 7(2):453–469. doi:10.1093/nsr/nwz161.
Liu, F., C. B. Skovsted, T. P. Topper, and Z. Zhang. 2020b. Revision of Triplicatella (Orthothecida, Hyolitha) with preserved digestive tracts from the early Cambrian Chengjiang Lagerstätte, South China. Historical Biology. doi:10.1080/08912963.2020.1747059.
Liu, F., C. B. Skovsted, T. P. Topper, and Z. Zhang. 2020c. Soft part preservation in hyolithids from the lower Cambrian (Stage 4) Guanshan Biota of south China and its implications. Palaeogeography, Palaeoclimatology, Palaeoecology. doi:10.1016/j.palaeo.2020.110079.
Moysiuk, J., M. R. Smith, and J.-B. Caron. 2017. Hyoliths are Palaeozoic lophophorates. Nature 541:394–397. doi:10.1038/nature20804.
Skovsted, C. B., M. Martí Mus, Z. Zhang, B. Pan. L. Li, F. Liu, G. Li, and Z. Zhang. 2020. On the origin of hyolith helens. Palaeogeography, Palaeoclimatology, Palaeoecology 555:109848. doi:10.1016/j.palaeo.2020.109848.
Smith, M. R. 2020. Finding a home for hyoliths. National Science Review 7(2):470–471. doi:10.1093/nsr/nwz194.
Sun, H., M. R. Smith, H. Zeng, F. Zhao, G. Li, and M. Zhu. 2018. 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.
We start off with two of the geologically oldest described titanosaurs before jumping back to the Late Cretaceous of Patagonia. If you're keeping track, you may notice that Titanosaurus seemingly should have been included. It's being held over for next month, which will be all Titanosaurus, including various species originally named to Titanosaurus that don't belong there and haven't otherwise been covered.
It's time for the annual review of The Compact Thescelosaurus. As is traditional, there's a new sheet, which this year covers mosasaurs, as you might have guessed from the image. The classification diagram page has been updated as well. (Don't forget, Wednesday the 14th is also National Fossil Day!)
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Mosasaurus conodon, hanging out at the Science Museum. |
Like any good Minnesotan, I appreciate a quality agate, and although I don't do a great deal of agate hunting, I *have* learned how to spot their characteristic luster. (I've never spotted anything big, but it's a neat trick.) When road work began this summer near where I live, I made it a point to observe the disturbed ground when I would take a walk. The glaciers that brought agates into the Twin Cities didn't linger where I am, but you never know. Until a couple of weeks ago, all I saw were chips, including the remains of one that may have been about the diameter of a dime had it not been shattered into shards by being run over (I didn't know they would splinter like that). This time, though, I noticed a red pebble with a cherty sheen on the path. I could tell it hadn't simply gotten paint on it, so I scooped it up to clean it for a closer look. Although it has microcrystalline quartz and red coloration, and certainly looks like it might be a Lake Superior agate from a few feet away, that's not what it turned out to be.
I'm cheating because I haven't yet showed a photo of one of the shorter sides, but this is actually a pebble of Mary Ellen jasper, a stromatolitic jasper that comes from the Biwabik Iron Formation. It's quite a bit older than any of the other fossils that have featured on this blog, coming from a Paleoproterozoic formation about 1.88 billion years old (Jirsa et al. 2008). It gets its name from the Mary Ellen Mine in the Iron Range. How did it get to where I live? Although it could have been a pebble in the subsurface, transported from the Iron Range by glaciers, it may instead have gotten here in gravel being used for the road work. The gravel would have been sourced from a gravel pit, which brings us back to glaciers again because the state's gravel pits are often in glacial deposits. In fact, in some of them you can pick out deposits left by different glaciers moving from different areas. Glaciers that passed through the Superior region brought agates south. Glaciers that passed through the Dakotas scraped up Cretaceous sedimentary rocks. (Cobban and Merewether 1983 commented on a fragment of phragmocone of a Cretaceous ammonite, Prionocyclus novimexicanus, found in glacial drift at the Brickyard.) The glacier that collected this pebble would have gone through the Range before depositing it.
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| This side of the pebble shows the characteristic red whorls of the stromatolitic layers with dark streaks between them. |
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| In this photo I've put water on the surface, in case that makes it easier to see. |
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.
Jirsa, M. A., J. D. Miller, Jr., and G. B. Morey. 2008. Geology of the Biwabik Iron Formation and Duluth Complex. Regulatory Toxicology and Pharmacology 52(supplement to 1):S5–S10.
Of course Changmiania liaoningensis was going to get my attention; nearly complete hypsil-grade ornithischians are always welcome here. I had a couple of other topics ahead of it in the queue, but with those out of the way, we can take a few minutes to appreciate this new species and its excellent fossils.
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| In fact, let's do that right now. Figure 1 from Yang et al. (2020); 1A and 1B are the type specimen, and 1C is the referred specimen. Red arrows indicate gastrolith clusters. CC-BY-4.0. |
Genus and species: Changmiania liaoningensis. The genus name is based on "changmian", pinyin for "eternal sleep", while the species name refers to Liaoning (Yang et al. 2020). A loose translation of the name is "eternal sleeper of Liaoning".
Citation: Yang, Y., W. Wu, P.-E. Dieudonné, and P. Godefroit. 2020. A new basal ornithopod dinosaur from the Lower Cretaceous of China. PeerJ 8:e9832. doi:10.7717/peerj.9832.
Stratigraphy and geography: Lujiatun Beds at the base of the Yixian Formation, from Lujiatun, Beipiao City, in western Liaoning, China (Yang et al. 2020).
Holotype: PMOL AD00114 (Paleontological Museum of Liaoning, Shenyang Normal University, Shenyang, Liaoning, China), a skeleton which is more or less complete and articulated. A second nearly complete and articulated specimen, PMOL LFV022, has been referred to the species. The specimens were acquired from local farmers, and had been partially prepared before acquisition, but show no evidence of being augmented (Yang et al. 2020).
If you've been at this for a while, you can probably envision a basic hypsil-type skeleton with little difficulty, and at first glance that's what you're getting here. There's the long tail (lacking abundant ossified tendons, but given some stiffness by the size of the transverse processes and the zygapophyses), the well-developed hind legs, short arms, small hands, light skull between a rectangle and an elongate triangle in shape, and so on. The body size is, unsurprisingly, small: Yang et al. (2020) give the total length of the type specimen as 1,170 mm (a hair over 46 inches), more than half of which is tail (650 mm or 25.6 in), with a skull 110.5 mm long (4.35 in) and a femur 115.5 mm long (4.55 in). The specimens have been left in their slabs, which does obscure some anatomical details but preserves the association of the bones (and the gastroliths, clusters of which are found with both specimens in the right "lumbar"/pelvic region).
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| The face of Changmiania liaoningensis; not quite as pointy and elongate as Thescelosaurus, but you get the idea. Figure 2 in Yang et al. (2020). CC-BY-4.0. |
After finishing admiring the outstanding specimens, one of the first anatomical differences you may notice from the standard model is that C. liaoningensis has no neck. Not literally, of course, but for a dinosaur it's unusually poorly supplied with cervicals, with only six cervicals of no particular length (you yourself have seven). If you're looking closely at the photos, you may also notice that the neural spines of the sacral vertebrae are not separated. This is not an artifact of preparation; the sacral neural spines are in fact fused into a bar. Yang et al. (2020) interpreted these and other features of the skeleton as evidence of adaptation for burrowing. Some of the other features include: fusion of the premaxillae; shortened forearms and hands; relatively large shoulder girdles in which the scapula and coracoid are fused; hips and leg sockets relatively canted, which would make it easier for the animal to assume a stable digging posture; and a well-muscled proximal tail, based on the relatively large processes. However, like other hypsils interpreted as having burrowing habits, the hind legs are still quite well suited for running, making it at most a part-time burrower. Yang et al. (2020) hypothesized that the two specimens of C. liaoningensis represent individuals trapped in collapsed burrows.
This brings us to the evolutionary relationships of C. liaoningensis, and if you've been paying attention to hypsil-grade ornithischians, you're well acquainted with the bewildering range of opinions. Sometimes practically every hypsil is an ornithopod, except Agilisaurus and Yandusaurus, which seem to be permanent outcasts (Dieudonné et al. 2020). Sometimes not even Hypsilophodon is an ornithopod (Madzia et al. 2018). You can find almost every other permutation in between in someone's paper. For the purposes of the paper we are actually looking at (Yang et al. 2020), which includes two of the authors of Dieudonné et al. (2020) and has a similar composition of Ornithopoda, C. liaoningensis ends up as the most basal ornithopod, not in a clade with any other hypsil, burrowing or not. (You may also notice that Nanosaurus agilis continues its astonishing revival.)
References
Dieudonné, P.-E., P. Cruzado-Caballero, P. Godefroit, and T. Tortosa. 2020. A new phylogeny of cerapodan dinosaurs. Historical Biology. doi:10.1080/08912963.2020.1793979.
Madzia, D., C. A. Boyd, and M. Mazuch. 2018. A basal ornithopod dinosaur from the Cenomanian of the Czech Republic. Journal of Systematic Palaeontology 16(11):967–979. doi:10.1080/14772019.2017.1371258.
Yang, Y., W. Wu, P.-E. Dieudonné, and P. Godefroit. 2020. A new basal ornithopod dinosaur from the Lower Cretaceous of China. PeerJ 8:e9832. doi:10.7717/peerj.9832.
This time we don't stop in Patagonia, instead visiting three different landmasses to meet three smallish titanosaurs known primarily from bones between the middle of the neck and the base of the tail. If you feel like you need a hit of fresh Patagonian titanosaurs, if you have access to the Journal of Vertebrate Paleontology allow me to suggest Otero et al. (2020), right off the presses, on the appendicular anatomy of Patagotitan mayorum. Or perhaps freely available Kundrát et al. (2020), dealing with an embryonic Patagonian titanosaur with a blunt horn?
When I wrote about the NPS fossil proboscidean inventory, you may recall that I mentioned there was one Eastern record I wished I could have confirmed. I thought it was only fitting to shine a spotlight on it in conjunction with the anniversary of the event that made the park unit in question famous.
Nothing too heavy today; I just wanted to draw your attention to a very unusual crinoid, Ammonicrinus from the Early and Middle Devonian of Europe and north Africa. While we're used to the idea that crinoids are either stalked things with spindly arms, or free-floating things with spindly arms, not all of them stuck to this body plan. Some of them evolved an enrolled body plan, such as Myelodactylus, which as a fossil looks a bit like a curled-up millipede. Some of them went even farther, like the subject of today's post (and see Bohatý 2011 for much more information).
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| Yes, this is a crinoid, just... different. Figure 1 in Bohatý (2011). CC-BY-4.0. |
Ammonicrinus came in three great flavors: stalked and with a shielded but exposed crown ("exposed roller-type", seen only in the early history of the genus); stalked and with an entirely enrolled crown, most of the animal laying on the seafloor ("encased roller-type"); and barely stalked with an entirely enrolled crown, perched on a brachiopod shell ("settler type"). For the remarkable "encased roller-type", the base was a holdfast attached to something, which was followed by several large, bead-like columnals. Then the columnals began to widen and flatten into broad concave-convex structures, shaped something like brackets in cross-section. These bracket-shaped columnals then turned into a much narrower section which connected to a stocky crown. The crown and the thinner columnals were wrapped up within the broader bracket-shaped segments, with just enough space on either side to pass water through. For good measure, the segments were also decorated with long, articulated, echinoid-like spines (Bohatý 2011).
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| An early Ammonicrinus, of the "exposed roller-type". Figure 6 in Bohatý (2011). CC-BY-4.0. |
What could have possessed the ammonicrinids to go in this direction? One possibility is that everything is tied to making an end-run around other crinoids. Typical crinoids would filter higher in the water column; Ammonicrinus could have the lower levels all to itself. The drawbacks are that the crinoid would be more exposed to predation from benthos (it's hard to believe that anything would willingly eat a crinoid, but there's no accounting for taste), and would be more vulnerable to fouling from the muddy bottom. Ammonicrinus addressed the issue of predation by protecting its crown via enrolling; the spines would have also offered protection. The spines would have also helped to brace the animal against the unstable bottom environment. To keep water flowing and to clear itself of sediment, it could rock the enrolled part of the skeleton, which would force water through the crown (Bohatý 2011).
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| An Ammonicrinus doing its thing, rocking to promote a current. Figure 14C in Bohatý (2011). CC-BY-4.0. |
References
Bohatý, J. 2011. Revision of the flexible crinoid genus Ammonicrinus and a new hypothesis on its life mode. Acta Palaeontologica Polonica 56(3):615–639.
Today on "Your Friends The Titanosaurs", it's a giant enigma (Ruyangosaurus giganteus), a much smaller and much better known titanosaur that also turns out to have its enigmatic side (Saltasaurus loricatus), and a good old-fashioned titanosaur skull taxon (Sarmientosaurus musacchioi), plus special guest stars Noasaurus and the Rincón de los Sauces titanosaur! (If anything seems odd, formatting-wise, it's because this is my first structurally complex post since Blogger changed to a new interface, and I'm dealing with a couple of things.)
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| From Broom (1904). The "x 1/7" business is not accurate outside of the original paper, but I will say the femur is estimated to have been 50 cm long (20 in) when complete, if that helps. |
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| One of these... |
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| Several more, in situ. A might be a ringer; I'm not sure. B is an overturned shell (note also the tiny pygidium just above and to the right). C is partially encrusted. D shows what happens when a thin piece of rock and a thin shell meet inexperienced preparation from the underside. |
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| What do the five rounded domed blobs of bryozoans have in common? If you turn them over, they all have the heart of a brachiopod. |
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| This strophomenid has a craniate encrusting on the lower right, as well as several cornulitids. |
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| The outline of the seaway is roughly after Robinson Roberts and Kirschbaum (1995), with a more substantial Mississippi Embayment added and a bit more on the Atlantic Coastal Plain, which I let peter out in New England. No attempt has been made to reconstruct the marine extent on the Pacific coast. Also, Minnesota was improvised after Sloan (1964), due to Robinson Roberts and Kirschbaum (1995) having a text box over the state. Sites mentioned in the post are: 1. Yellowstone National Park; 2. Little Bighorn Battlefield National Monument; 3. Badlands NP; 4. Missouri National Recreational River; 5. Dinosaur NM; 6. Glen Canyon National Recreation Area; 7. Mesa Verde NP; 8. Chaco Culture National Historic Park; 9. Big Bend NP; 10. Wrangell-St. Elias NP and Preserve; 11. Fort Washington Park. |
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| Lo, the type section of the St. Peter Sandstone, mostly behind a wall (probably for the best, given the way people use any handy outcrop of the St. Peter to practice their rock-carving skills) |
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| At this fall, out of the Mifflin Member of the Platteville, it's easy to see the lighter color where the rocks used to be. |
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| If the beds are noticeably tilted, that's a good indication they aren't where they started. (And also the whole "lying in jumbled heaps" thing, that's a good clue.) |
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| A small, gentle waterfall southeast of Coldwater, unnamed as far as I know, running through a cleft in the St. Peter. |
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| Same photo, light red lines added to trace the features. |
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| Gomphotherium osborni in Elephant Hall, University of Nebraska State Museum. You may not realize it, but proboscidean fossils are very common in Nebraska. We haven't had a gomphothere photo yet, so it seemed appropriate. |
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| Stegomastodon mirificus, same venue. Despite the name, it's not a close relative of mastodons (and certainly has nothing to do with Stegosaurus!); it's a later gomphothere. |