The Continuing Story of Nanosaurus agilis

Recently Barrett and Maidment (2025) published a paper on the state of Morrison hypsilophodont-things, which is of great interest here because after two long posts on Nanosaurus agilis, we're solidly invested in its fate. How did it fare? Short answer: not very well. But, on the other hand, neither did anybody else. Well, Drinker was shown more appreciation than probably anyone has given it since 1990, but that's not saying much.

So, what to call these happy fellows at the Denver Museum of Nature and Science?

Barrett and Maidment (2025) went over the type specimens of N. agilis, N. rex (Othnielia), Laosaurus celer, L. consors (Othnielosaurus), L. gracilis, and, via illustrations, Drinker nisti. (There is a slight advance on Carpenter and Galton 2018, in that we now get the implication that Bob Bakker has D. nisti as opposed to the whereabouts being unknown.) They find none of the type specimens to be diagnostic. The one that comes off the worst is L. consors. Material cataloged as the type is an assemblage rather than an individual. To be fair, Marsh knew he had multiple individuals at the time, but then he should have been more careful about specifying a type. The parts that had been on display as a panel mount at Yale may be one associated individual, consisting of most of the cervical and dorsal series (just centra), possibly six sacrals, parts of the left shoulder girdle and the pelvis, a partial left femur and complete left foot, and parts of the right femur, tibia, and astragalus. This is a lot of parts/partials plus a lot of plaster, which is not encouraging. The rest of the material is a chimeric mix including at least juvenile dryosaur and hypsil material. The only one of the six that ends up being interesting is D. nisti, which has some dental and jugal features reminiscent of pachycephalosaurs (but is still not diagnostic, although it would be nice to have the type material in hand to be sure).

Where does this leave the Morrison hypsil(s), which Carpenter and Galton (2018) had declared N. agilis? Anonymous, for the time being. Carpenter and Galton (2018) looked upon the pile of Morrison hypsil bits and proposed it was "all" Nanosaurus agilis. Barrett and Maidment (2025) looked upon the same pile and clutch of names and regarded it as a taxonomic dead end, to be set aside to allow a fresh start for more complete and better preserved specimens (with quarry maps and documented associations and such).

At heart, we're seeing two different approaches to taxonomy, and which one you choose depends on how pragmatic you are and how bound you feel by existing names. If you want a species with a holotype featuring robust apomorphies, N. agilis is not for you. We saw that in the comments section of the last post: most of the characters cited by Carpenter and Galton (2018) are widely distributed among hypsil-things, with just a couple that might have some particular use. However: Is there a hypsil-thing in the Morrison that is anatomically consistent across specimens, whether or not said specimens are diagnostic across Ornithischia? If so, is it reasonable to call this hypsil *something*, knowing that it may be revised later? If so, the oldest existing name is Nanosaurus agilis. If you go that route, I'd recommend looking into a neotype, though. ("All would be well, if, if, if, if, if...")

References

Barrett, P. M., and S. C. R. Maidment. 2025. A review of Nanosaurus agilis Marsh and other small-bodied Morrison Formation “ornithopods". Bulletin of the Peabody Museum of Natural History 66(1): 25–50. doi: https://doi.org/10.3374/014.066.0102.

Carpenter, K., and P. M. Galton. 2018. A photo documentation of bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation, USA. Geology of the Intermountain West 5:167–207. doi:

Prosauropod rehab

I once wrote that "When you get interested in something, what's already there when you arrive will seem like it has always been there, and everything that comes along later will always seem a little new to you, even if it has been decades." Taxonomic fashion is one of those things. When I got into dinosaurs in the mid-1980s, prosauropods had shrunk to something like a half-dozen well-regarded genera plus some dross and a few names that were too new for someone to have gotten around to sinking. One of the survivors was always Ammosaurus, which somehow parlayed a few pelvic differences from Anchisaurus into family-level separation (Ammosaurus the plateosaurid, Anchisaurus the anchisaurid). Meanwhile, all of Africa's prosauropod diversity was being crammed, with varying degrees of success, into Euskelosaurus, Massospondylus, these things called "roccosaurids", and Aristosaurus. (Aristosaurus? You had to be there.) Since I had no personal memory of the work that had gone on in years before, and at five years old wasn't really pouring through the primary literature, it seemed like things had always been that way. This is not the case, though. The vast majority of this synonymization had taken place in the previous 10–15 years and was the work of just a few authors. What had come before that?

Well, obviously, what had come before that were the decades of describing and naming scads of prosauropods; otherwise, there wouldn't have been anything to synonymize. It seems like people loved to name them and then forget about them. The history of their research is littered with misconceptions, some of which seem blindingly obvious in hindsight (big predatory prosauropods? You sure you're not just looking at shed crowns from carnivorous animals?). It's a matter of lack of respect and interest: If dinosaurs were a sideshow to the evolution of important things (i.e., mammals), prosauropods were a sideshow to the sideshow, a couple of card tables featuring a guy with a big unibrow and someone doing "pull my finger" jokes.

Skip ahead a few decades. Some of my readers will have never heard of Aristosaurus (well, okay, nobody living has heard of Aristosaurus except me and maybe 10 other people who have been sworn to secrecy, and now I've lost my membership in the group for a cheap gag) and know only of Euskelosaurus as this thing that nobody talks about except to badmouth in the "Background" section of papers. You wouldn't remember the heady days of the '00s, when that genus collapsed under the weight of its synonyms. Instead, it will have always been a nomen dubium to you, and if it somehow returned (stranger things have happened), it wouldn't be a resumption of your interrupted Euskelosaurus service but something new. (Why, yes, I do have a sense I'm getting older. The only thing that saved me from being older than all MLB players this year was four games and 3 2/3rds innings from Rich Hill.)

Anyway, I've long had a soft spot for prosauropods. They're never been supremely popular and had the poor marketing insight to go extinct before they could be menaced by particularly charismatic theropods, but they have a subtle charm, like small bipedal ornithischians. Over the past year or so, there's been a series of papers providing redescriptions and historical analyses of some of the most venerable genera and species of prosauropods, including comments on some of those 1970s–1980s synonymizations. They include Barrett and Chapelle (2024) on Massospondylus, Barrett and Choiniere (2024) on Melanorosaurus, and Regalado Fernández et al. (2023) and Schaeffer (2024) on Plateosaurus.

Massospondylus

Another instance of perception not matching up with chronology: one of the things that comes out of Barrett and Chapelle (2024) was that before the 1970s, Massospondylus was kind of a dog of a taxon. It achieved its present exalted status mostly by getting there first and being less of a dog than the other choices. If Richard Owen had decided to lead with Leptospondylus or Pachyspondylus in 1854 instead of Massospondylus, it wouldn't have had that first point in its favor, and then where would we be? When a name was needed to absorb the mid-sized prosauropods of the Early Jurassic of southern Africa, M. carinatus was there waiting. Some of the new material was good enough to support a name, and our conception of Massospondylus carinatus drifted from the varied bones named by Owen to that material, which eventually supplied a neotype (a type or name-bearing specimen selected after a species was named, to replace a type that was lost or not specified). The original material was no longer available to query, having been destroyed in World War II, but casts and line drawings of some of it remain, and Barrett and Chapelle (2024) provided redescriptions of as much as they could. In the end, it's just as well that the species is now represented by a neotype, because that original material is not diagnostic beyond the level of Massospondylidae at best. The drift of the conception of Massospondylus, plus the uncritical assignment of a lot of material since the 1970s, leaves the possibility of surprises once "Massospondylus" specimens are thoroughly examined. This also applies to Melanorosaurus and Plateosaurus. (Granted, I'm not convinced that every new genus and species will stand the test of time, but that's for another time, when the pendulum eventually swings back to consolidation.)

Massospondylus as a flowchart. Figure 4 of Barrett and Chapelle (2024). CC BY 4.0.

Melanorosaurus

Proposed synonymizations don't always pan out, of course (one reason not to go overboard committing to the conclusions of New Paper Of The Week). The proposed sinking of Lufengosaurus and Yunnanosaurus into Massospondylus at the height of prosauropod consolidation did not attract much support, and the proposed sinking of Melanorosaurus into Euskelosaurus fared only marginally better. Although it escaped that fate, Melanorosaurus has never seemed to get much respect. It's almost a reflex for authors to mention its questionable type material, as if apologizing for trotting it out. Barrett and Choiniere (2024) went back to the original syntype series (a group of specimens used to bear a name) to see what could be salvaged.

M. readi, like many a species, was based on your standard pile o' bones of unclear association. Barrett and Choiniere (2024) regarded a subset, including several partial or complete vertebrae, an ulna, a radius, an ilium, a partial pubis, two tibiae, a fibula, and parts of four metatarsals, as representing one skeleton that they designated a lectotype (a name-bearing specimen selected from a syntype series). Furthermore, they were able to find several diagnostic features. It's not the prettiest type, but it *is* useable. The authors compared the lectotype to several other specimens frequently used as Melanorosaurus exemplars in the literature. Unfortunately, this part doesn't go quite so well for M. readi; NMQR 3314, one of the more important specimens (including a skull), is excluded on both anatomic and stratigraphic grounds. Another specimen, NMQR 1551, is considered consistent with M. readi but an assignment is not confirmed. (I personally hope it is, because I don't want an excuse for someone to try to bring back "Roccosaurus" as a name.) The upshot is M. readi is valid but not particularly helpful at the moment, pending reclamation of more complete material.

Plateosaurus

If Massospondylus is what you get when specimen assignment goes to the last species standing, Plateosaurus is what happens when people care too much. For sheer mind-numbing taxonomic complexity in the world of dinosaurs, it's hard to beat the adventures of Upper Triassic European prosauropods. An extensive historical review can be found in Regalado Fernández et al. (2023), along with detailed reports on many of the significant specimens involved in the story. One of the things I find useful is rather than synonymize the many lesser lights with a species of Plateosaurus, the authors treat them as dubious species. Why is this useful? Keeping them separate helps to keep the concept of the host species from drifting. It's not as if there's some prize for having the tidiest faunal list, after all; specimens should only be assigned to the level of confidence.

Stratigraphic distribution of German Plateosaurus and friends. I could quote every figure in this article, but then I might as well reproduce the whole thing. Figure 2 in Regalado Fernández et al. (2023) CC BY 4.0.

Coming at Plateosaurus from a different angle, Schaeffer (2024) redescribed the holotype (singular name-bearing specimen) of P. trossingensis, which became the type species of Plateosaurus a few years back (another long story). This gets right at the heart of the taxonomic drift: you have to establish your basis of comparison before you can compare anything to it. Continuing with this, Schaeffer ran a phylogenetic analysis of sauropodomorphs with Plateosaurus trossingensis based just on the holotype. Fortunately, the species behaved predictably in terms of general location and neighbors.

References

Barrett, P. M., and K. E. J. Chapelle. 2024. A brief history of Massospondylus: its discovery, historical taxonomy and redescription of the original syntype series. Palaeontologia africana 58: 97–131.

Barrett, P. M., and J. N. Choiniere. 2024. Melanorosaurus readi Haughton, 1924 (Dinosauria, Sauropodomorpha) from the Late Triassic of South Africa: osteology and designation of a lectotype. Journal of Vertebrate Paleontology 44(1): e2337802. doi: https://doi.org/10.1080/02724634.2024.2337802

Regalado Fernández, O. R., H. Stöhr, B. Kästle, and I. Werneburg. 2023. Diversity and taxonomy of the Late Triassic sauropodomorphs (Saurischia, Sauropodomorpha) stored in the Palaeontological Collection of Tübingen, Germany, historically referred to Plateosaurus. European Journal of Taxonomy 913(1): 1–88. doi: https://doi.org/10.5852/ejt.2023.913.2375

Schaeffer, J. 2024. Osteological redescription of the holotype of Plateosaurus trossingensis (Dinosauria: Sauropodomorpha) from the Upper Triassic of SW Germany and its phylogenetic implications. Journal of Systematic Palaeontology 22(1): 2335387. doi: https://doi.org/10.1080/14772019.2024.2335387

Geranosaurus atavus

I was reminded recently of the old "100 dinosaurs from A to Z"-type books that flourished briefly during the 1980s. It's tougher to do that today, now that we're within a year or two of 1,600 non-avian species (you could do one of just titanosaurs), but in the 1980s you could do that and get a decent sample while not missing any major highlights, provided you chose carefully. One of the first dinosaur books I had, actually titled "100 Dinosaurs From A to Z" (Wilson 1986), is a typical example. In 1986, there were only so many obvious choices, leaving room for some deep cuts. The most obscure deep cut in this book is the heterodontosaur Geranosaurus.

Fossil Crocodylomorphs of the National Park Service

For this year's National Park Service fossil group inventory, I've chosen crocodylomorphs, which for convenience I'm going to refer to as "crocs". Crocodylomorpha encompasses the true crocodilians and their closest extinct relatives, which over the years has been defined to exclude major groups of allied Triassic archosaurs (rauisuchids, poposaurs, prestosuchids, etc.). (Technically speaking, traditional Crocodilia is closer to the clade Crocodyliformes, but I have a soft spot for "sphenosuchians" and it's my blog.) Non-crocodilian crocodylomorphs were big players throughout the Mesozoic but came to peter out in the Cenozoic, with holdouts into the Miocene (Sebecosuchia). Some of these non-crocodilian crocodylomorphs looked basically like modern crocodilians and presumably filled very similar niches, but by definition weren't crocodilians*. Others were quite a bit different; for example, small, long-legged terrestrial crocs had a wide distribution from the Late Triassic through the Jurassic, and there were multiple groups of marine forms.

*I have certain misgivings about crown groups, particularly that future stability of usage relies on groups not going extinct (or there would have to be backdating, like radiocarbon dates are pegged to 1950), although at this point I might as well complain about the decline in use of Etruscan.

The NPS record of croc fossils turns out to be sparser than I expected: there are 17 park units with solid records (albeit two of these being reworked or washed up, making them hard to place stratigraphically), and another couple potential records. Here is the requisite map and its accompanying long caption:

Click to embiggen. The sites mentioned in this post are: 1. John Day Fossil Beds National Monument; 2. Bighorn Canyon National Recreation Area; 3. Fossil Butte NM; 4. Dinosaur NM; 5. Colorado NM; 6. Curecanti NRA; 7. Bryce Canyon National Park; 8. Glen Canyon NRA; 9. Petrified Forest NP; 10. Chaco Culture National Historical Park; 11. Theodore Roosevelt NP; 12. Badlands NP; 13. Agate Fossil Beds NM; 14. Niobrara National Scenic River; 15. Big Bend NP; 16. Waco Mammoth NM; 17. Gateway NRA; 18. Fort Washington Park; 19. Cumberland Island National Seashore.

These 19 units are primarily in the Colorado Plateau and northern Great Plain, and these two areas correlate in large part to temporal distribution: the Colorado Plateau records are mostly Jurassic and Cretaceous, and the Great Plains records are Cenozoic. A couple of compact diagrams will show this:

Part 1 shows the Mesozoic, Paleocene, and Eocene records, which make up the bulk of the reports.

Part 2 shows the few younger records; the two that can't be pinned down are added to keep them company.

You can probably guess a lot of the story if you have some familiarity with the stratigraphy of western North America. As so many other groups of terrestrial vertebrates, the place to go in the NPS for Triassic crocs is Petrified Forest National Park, where "sphenosuchians" have been found in the famous Chinle Formation. (Ignore the phytosaurs; they only look like crocs.) After that, possible early croc tracks have been found in the Navajo Sandstone of Glen Canyon National Recreation Area; with all of the Early Jurassic tracks in the Colorado Plateau parks, there are likely other track records. We have no body fossil records in the parks' rocks yet, though (the facies aren't as forgiving as elsewhere). Four parks have records for the Late Jurassic: Bighorn Canyon National Recreation Area has swim traces attributed to crocs in the Sundance Formation, and no points for guessing what's represented at the other three. (It's the Morrison Formation.) NPS Morrison crocs are best known from Dinosaur National Monument, which primarily has the well-represented Amphicotylus (formerly Goniopholis), but also produced the type specimen of the diminutive Hoplosuchus kayi.

The Cretaceous is more sparsely represented, with nothing confirmed from the Early Cretaceous. Ot the Late Cretaceous records, neither Bryce Canyon NP (Straight Cliffs and Wahweap microvertebrate remains) nor Chaco Culture National Historical Park (Menefee isolated material) have much to speak of. Big Bend NP, on the other hand, has the most impressive croc record in the NPS. Granted, that's an easy call when you can point to the type specimen of the suitably Texas-sized Phobosuchus riograndensis (now a species of Deinosuchus), but the park also has by far the longest record of crocs in the NPS. Five formations are represented: the Aguja Formation and Javelina Formation, both Late Cretaceous; the overlying Black Peaks Formation, which straddles the Cretaceous and Paleocene; the Early Eocene Hannold Hill Formation; and the Middle Eocene Canoe Formation. Recently a second croc species has been named from Big Bend NP fossils: Bottosaurus fustidens, from the Paleocene part of the Black Peaks Formation. Other taxa are present, but have not been studied in as much detail.

Looking elsewhere in the Paleocene, there is a single record of a partial bone from the Aquia Formation at Fort Washington Park, and Theodore Roosevelt NP has crocs in the Bullion Creek and Sentinel Butte Formations, comparable to nearby Wannagan Creek (only not quite so concentrated). The Eocene is fairly good for NPS crocs. Apart from Big Bend, we have croc fossils in: the Wasatch Formation at Fossil Butte NM; the Clarno Formation at John Day Fossil Beds NM; and the Chadron Formation at Badlands NP. The type specimen of Caimanoidea visheri (now considered a synonym of Alligator prenasalis) may have come from Badlands NP.

And that's almost the end. Crocs disappeared from the drying interior of North America during the middle Cenozoic. For the Miocene, we have one *very* sketchy potential record from the early Miocene Anderson Ranch Formation of Agate Fossil Beds NM and better records of crocs from the middle Miocene Valentine Formation of Niobrara National Scenic River (including the type specimen of Nordenosaurus magnus, originally described as a big lizard but now identified as a small crocodilian). At Waco Mammoth NM there is late Pleistocene alligator material, but we are otherwise lacking Pleistocene crocodilian records. Two units have material of uncertain provenance: a scute found in dredge material at Cumberland Island National Seashore and various croc fossils that have washed up at Gateway NRA.

Your Friends The Titanosaurs, part 34: Titanosaurs of Yesterday

There are a few taxa of interest that haven't yet been covered. They include: 1) "historical titanosaurs", the kind you might stumble across in a 1980s dinosaur dictionary; 2) poorly known species regarded as titanosaurs mostly on the circumstantial evidence of time and place, without the anatomical evidence to back up a classification; 3) species that have turned up in Titanosauria once or twice during the cladistic era (mid-1990s to the present) but are not currently or generally regarded as titanosaurs; and 4) species that appear to have been near Titanosauria and sometimes hop the line in analyses, but usually are found outside. This post is for the first three varieties. We've got 15 in the queue, so as you can image I'm not going to go into a great deal of detail.

Curiously, most of McIntosh's "Sauropoda incertae sedis" from the first edition of The Dinosauria show up on this page: "Pelorosaurus" becklesii (=Haestasaurus), Mongolosaurus, Austrosaurus, and Aepysaurus (=Aepisaurus), plus a shout-out to "Apatosaurus" minimus. The only ones not here are "Morosaurus" agilis (now described as a rebbachisaurid [2021/04/02: no, dicraeosaurid; do this long enough and they all run together], Smitanosaurus), and Campylodoniscus, which was previously featured. This says something about quasi-titanosaurs, but I'm not sure what. The taxa also skew old, with many of Early Cretaceous or even Late Jurassic age, suggesting it's harder to get a handle on putative early titanosaurs. Unsurprisingly, many of them are dubious, albeit in all kinds of ways: from garden-variety causes like too little material, to "unavailable for study due to being destroyed by monsoons", to "the osteoderms turned out to be ribs", to "the original describer thought a pile of caudals from several sites separated by miles belonged to one individual", to "actually filled mollusk borings".

As a reminder, because the terms come up several times, Titanosauriformes is the clade made up of the most recent common ancestor of Brachiosaurus and Saltasaurus plus all of its descendants, and Somphospondyli is the clade made up of all sauropods more closely related to Saltasaurus than to Brachiosaurus.

Trilophosaurus and Ophthalmothule

For this post, we highlight two extinct reptiles that have been the subjects of publications in the past few days. Other than that, they don't have much in common. One is a short-necked terrestrial herbivore less than three meters long that lived during the Late Triassic in what is now Arizona, the other is a long-necked marine carnivore between five and six meters long that lived at about the Jurassic–Cretaceous boundary at what is now an Arctic island (not quite so arctic at the time).

Ngwevu intloko

For our first "prosauropod" entry since Ledumahadi mafube back in September 2018, we return to the Upper Elliot Formation of South Africa. This time around, it's massospondylid Ngwevu intloko. Or, is it just a distorted, young, or otherwise odd individual of the Upper Elliot classic Massospondylus carinatus?

What I Did While I Was Out

I made no post last week because I was traveling for work. Generally, I don't have the time to work on a post while traveling, and this was no exception. In order to get the most bang for our buck on work travel, we try to schedule as many projects as possible, and this trip was no exception. I had four separate projects scheduled over eleven days.

Photos from Albuquerque

Back in October I attended the annual meeting of the Society of Vertebrate Paleontology, held at Albuquerque, New Mexico. The meeting was co-hosted by the New Mexico Museum of Natural History and Science. Part of the program of the annual meeting is a reception at a co-hosting institution, where the attendees can mingle among the institution's exhibits. I was fortunate enough to be in the company of JP and Sarah Hodnett, who are very familiar with the museum. (In fact, we'd actually spent most of that day there already, working the National Fossil Day event.) Thanks also to JP and Sarah for helping me get around Albuquerque!

We also had the able assistance of ceratopsids for National Fossil Day.

Rebbachisauridae

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

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

Ledumahadi mafube

For reasons which are mysterious to me, this blog has become full of sauropodomorphs of one kind or another. It's been a good year for them. The latest is Ledumahadi mafube from the Elliot Formation of South Africa, an early giant near the base of the sauropod tree.

Yizhousaurus sunae

I originally had something else in mind for today, but it was heavily photo-dependent, and the photos weren't coming out very well (unresolved lighting and depth-of-field issues). I will have to try again some other time. Meanwhile, here comes Yizhousaurus sunae to the rescue! I'm not quite sure why "prosauropods" should have featured so frequently here (see also Bagualosaurus, Meroktenos, Xingxiulong, and two visits with Anchisaurus), but there you go.

Figure 3 from Zhang et al. (2018) (check the link for the lengthy caption). Note that the quadrate and associated bones are displaced from the back of the skull, which obscures the complete shape of the profile.

Dryosaurus elderae and the revenge of Nanosaurus agilis

It's been a busy few days over at The Compact Thescelosaurus, with new alvarezsaurs, nodosaurs, and dryosaurs. For this post, I'm going to focus on Carpenter and Galton (2018), which not only describes new species Dryosaurus elderae, but also is quite important for previous subject Nanosaurus agilis, and in general ticks off several of my boxes anyway ("hypsilophodonts", Morrison Formation, National Park Service areas, etc.).

Figure 2 from Carpenter and Galton (2018), showing the distribution of bipedal Morrison ornithischians. A keen-eyed observer who's familiar with the Morrison fauna might notice the absence of Drinker nisti and Othnielosaurus consors, and an abundance of Nanosaurus agilis...

Lingwulong shenqi

After our latest titanosaur entry and a week off, here's... another sauropod. This one's different though: it comes from early on in the history of sauropods, and shines a light on the early diversification of the group. I introduce Lingwulong shenqi, debuting as the world's oldest known dicraeosaurid at somewhere around 175 million years old, and the first substantiated dicraeosaurid from Asia. These "oldests" and "firsts" are more important than they might sound.

Stegomosuchus longipes, the terrestrial croc relative of Massachusetts

If you're the kind of person who reads this blog regularly, you're probably also the kind of person who's got at least one rock laying around. Maybe you've got dozens. Maybe you've got too many. Who am I to judge? The point is you've got rocks. Odds are, though, there isn't a potential type specimen in your yard.

Nanosaurus agilis: the smallest dinosaur you've never heard of (and for good reason)

Many millions of years ago, in a time that we would call the Jurassic and in a place we would call Colorado, small bipedal herbivorous dinosaurs frolicked and otherwise did things appropriate to small bipedal herbivorous dinosaurs. In their time, they died and a very, very few were selected by taphonomy to be fossilized. Of that tiny number, an even smaller subset have happened to be exposed at the surface at the right time and place to be found by a similarly tiny number of human beings who were specifically looking for such things. Having been found, their remains were sent off to be studied by another tiny number of people who had a lot of things on their minds, living in a world that has had little use for small bipedal herbivorous dinosaurs except as props to show off the (speculated) abilities of small bipedal carnivorous dinosaurs. It's not really that surprising that some of them have fallen through the cracks. Then there's Nanosaurus agilis.

Xingxiulong

Two dinosaurs were published on February 16, 2017. One of them was Isaberrysaura mollensis, which has gotten a lot of press because it's a weird basal ornithischian with gut contents. The other was Xingxiulong chengi, which hasn't gotten as much attention, although the Wikipedia article is pretty extensive. Xingxiulong is among what we used to call "prosauropods", now known as basal sauropodomorphs. It is represented by most of the skeleton, excepting the tips of the jaws, most of the hands, and the coracoids and sternal elements. It also provides me a half-point on my prediction for "prosauropods", which I'll take because it's been kind of a slow year so far.

Isaberrysaura, and the further revenge of gut contents

This week saw the publication of two new dinosaurs. Both of them have something to recommend them, but given my own preoccupations we'll have to leave Xingxiulong for someone else, or for another time. (Feel free to hop over to the paper, though!) Instead, we shall meet Isaberrysaura mollensis, a basal ornithischian packing an identity crisis and a belly full of seeds.

The "Kweichow Sauropod"

"Somebody's got to tell the tale/I guess it must be up to me" — B. Dylan

Among all the other oddities we encountered in the Glut (1982) series in the summer, there was one purported sauropod of particular obscurity, from "Kweichow" (Guizhou). I figured it was the specimen described in Young [Yang] (1948), but was somewhat discomfited to find that it had made itself scarce in the years since 1948. There weren't even any dinosaurs listed in "The Dinosauria" from Guizhou. Had it been re-evaluated as non-dinosaurian, or actually come from a different province? To my surprise, the journal was listed as "in storage" in the University of Minnesota library system, so I fired off an interlibrary loan request and in a few days was the proud owner of a shiny new pdf. Acting on the principle that every dinosaur deserves its day, I present the "Kweichow sauropod".

Chilesaurus

Well, sic transit gloria mundi to Chilesaurus, I guess. A couple of days on top of the world, and then hustled off the stage for a tiny-maniraptoran-slash-Batman-cosplayer. Could be worse; at least it's Batman. 'Round here, though, I've never really had much interest in the origins of flight, early bird evolution, or so on, so nuts to Yi. Let's bring Chilesaurus back on the stage for a few more minutes.