Know Your Ankylosaurs: North American Odds and Ends Edition

I've covered many of the North American ankylosaurs in my previous papers and blog posts. In 2013, I argued that what we thought was Euoplocephalus was more likely 4 taxa – Anodontosaurus, Dyoplosaurus, Scolosaurus, and Euoplocephalus proper. Then in 2014 we described a newankylosaurid, Ziapelta, from New Mexico. There are a few other taxa that had previously been proposed to be ankylosaurids, so let's take a look at them here.

Aletopelta, Stegopelta and Glyptodontopelta

Aletopelta is one of the more tantalizingly enigmatic ankylosaurs from North America. It's from a weird place – California – which may have been much further south 75 million years ago compared to its current position. It was also found in marine sediments, and the decaying carcass had formed a little reef, with oysters encrusting the ribs. The only known specimen of Aletopelta is relatively complete, all things considered, with the osteoderms in situ over part of the pelvis, the legs partially articulated, and with various odds and ends like osteoderms and vertebrae. Unfortunately, the ends of the bones are often chewed apart, and some of the material is a bit hard to interpret.

Here's the articulated pelvis and hindlimbs, and some other armour pieces, on display at the San Diego Museum of Natural History.

Regardless, Aletopelta is a very interesting ankylosaur. It has an unusual osteoderm morphology over the pelvis, with small hexagonal osteoderms closely appressed to each other. Ankylosaur pelvic armour seems to come in two major flavours: fused rosettes, like we saw in Dongyangopelta and Taohelong (and perhaps most famously in Polacanthus), and interlocking hexagons, like in Stegopelta, Glyptodontopelta, and Aletopelta. Tracy Ford suggested that ankylosaurs with these hexagonal pelvic shields might represent a clade (dubbed Stegopeltinae) of ankylosaurids. Glyptodontopelta has since typically been interpreted as a nodosaurid, as has Stegopelta, but the most recent interpretation of Aletopelta was that it was an ankylosaurid. In the revised phylogeny in my new paper, we found Stegopelta and Glyptodontopelta as nodosaurids, but Aletopelta as a very basal ankylosaurid. However, although Ford and Kirkland reconstructed Aletopelta with the typical ankylosaurid tail club, I don't think that it possessed one: the preserved distal caudal vertebrae don't show any of the lengthening or other modifications that are characteristic of ankylosaurid handle vertebrae.

An updated restoration of the known elements in Aletopelta - the main differences between this and Ford and Kirkland's reconstruction are the absence of a tail club, and uncertainty over what the head should look like.

Cedarpelta

Cedarpelta is an important taxon for understanding the biogeography and evolution of ankylosaurids, and I wish we had more specimens! I don't have many new comments to add about this taxon, since Ken Carpenter published a great description of the disarticulated skull back in 2001. Cedarpelta has been interpreted as a shamosaurine ankylosaur, as a relative of taxa like Gobisaurus and Shamosaurus (which I'll talk about in the next post) from Asia, and thus may point towards a mid Cretaceous faunal interchange between these two continents. In our revised phylogenetic analysis, we didn't find Cedarpelta as the sister taxon to either Gobisaurus or Shamosaurus, but it does come out as a basal ankylosaurid in their general neighbourhood, and I honestly wouldn't be surprised if future analyses or new taxa show support for it as a shamosaurine ankylosaur after all.

Nodocephalosaurus

Nodocephalosaurus! What a fun ankylosaur. It's really quite unlike the other ankylosaurids from North America, which typically have flat, hexagonal cranial ornamentation. Instead, Nodocephalosaurus has bulbous, conical cranial ornamentation. Bulbous cranial ornamentation is typical of Campanian-Maastrichtian Mongolian ankylosaurs like Saichania and Tarchia, but in those taxa the ornamentation is pyramidal rather than conical. The front end of the snout in Nodocephalosaurus is also unusual, because there's no obvious narial opening and instead the ornamentation has a stepped appearance. Hopefully better specimens with more complete snouts will resolve this weird morphology. I've also reinterpreted the position of the quadratojugal horn compared to Sullivan's original figures – the horn should be rotated forward so that the bottom margin of the orbit is complete.

Nodocephalosaurus holotype skull in dorsal and left lateral views.

Tatankacephalus

I don't have much to say about Tatankacephalus because I didn't look at the original material myself, but the previous phylogenetic analysis by Thompson et al. recovered it as a nodosaurid rather than an ankylosaurid as originally suggested by Parsons and Parsons, and we found the same result. Overall, Tatankacephalus is VERY similar to Sauropelta, so this is perhaps not surprising.

Up next: More odds and ends, but after I return from Utah!


Arbour VM, Currie PJ. In press. Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs. Journal of Systematic Palaeontology.

Know Your Ankylosaurs: New Mexico Edition!

There's a new ankylosaur in town - meet Ziapelta sanjuanensis from the Cretaceous of New Mexico!

Hello, Ziapelta! Many thanks to new Currie Lab MSc student Sydney Mohr for this wonderful life restoration of Ziapelta.

Ziapelta is represented by the holotype skull, first cervical half ring, and assorted other osteoderms, AND a referred first cervical half ring! (What are the odds of finding two really nice cervical half rings in the same field season? Bonkers!) It's a wonderful find from an area that seems to keep producing interesting dinosaur fossils.

Surprisingly, Ziapelta doesn't seem to be particularly closely related to the other ankylosaurid from the Kirtland Formation, Nodocephalosaurus. Instead, it's a close relative of Euoplocephalus and friends from Alberta – it shares the same general shape and pattern of cranial ornamentation, with flat, hexagonal caputegulae rather than the round, conical caputegulae of Nodocephalosaurus. Ziapelta is distinct from all of the Albertan ankylosaurids though: it's squamosal horns are thick and curve slightly downwards laterally, and its median nasal caputegulum is huge and triangular, rather than hexagonal. Somewhat bizarrely, Ziapelta has slightly bulbous or 'inflated' looking cranial caputegulae, not to the same extent as some of the Mongolian ankylosaurids like Saichania, but definitely moreso than Euoplocephalus or Anodontosaurus.

Cervical half rings once again prove to be taxonomically useful. Ziapelta has taller, more rectangular keeled osteoderms compared to Euoplocephalus, Anodontosaurus, and Scolosaurus, but does share the interstitial osteoderms present in Anodontosaurus.

Although we don't have the rest of the postcrania, we can assume that Ziapelta would have had a tail club since it is deeply nested within the clade of clubbed ankylosaurids. Did it have huge, triangular osteoderms like Anodontosaurus, a round tail club like Euoplocephalus, or a narrow tail club like Dyoplosaurus?

Ziapelta isn't the first ankylosaur described from New Mexico - in fact, it's just the latest in a string of interesting armoured dinosaur discoveries from there. At present, Glyptodontopelta is the only nodosaurid from the state, from the Maastrichtian Ojo Alamo Formation. It's known only from osteoderms, and mostly those from the pelvic region, but they're pretty distinctive and have a unique dendritic surface texture.

Glyptodontopelta bits at the Smithsonian.

Nodocephalosaurus is known from a partial skull from the De-na-zin Member of the Kirtland Formation. Its nodular cranial ornamentation is totally unique among North American ankylosaurids and more closely resembles the Late Cretaceous Mongolian ankylosaurids - an intriguing biogeographical conundrum that remains unresolved.

Nodocephalosaurus holotype skull at the State Museum of Pennsylvania. Check out those conical caputegulae!

Lesser known but deserving of more attention, my fellow labmate Mike Burns and colleague Bob Sullivan recently named another ankylosaurid from the stratigraphically lower Hunter Wash member of the Kirtland Formation. Ahshislepelta has a weird scapula with a strongly folded-over acromion process, as well as various other bits and bobs of the postcrania. Although there is little overlapping material between Ahshislepelta and Ziapelta, Ahshislepelta's osteoderms have a smoother surface texture, and the stratigraphic separate suggests we're probably looking at two different species.

Ahshislepelta holotype scapula at the State Museum of Pennsylvania.

Ziapelta is also neat because it (and Nodocephalosaurus) occur in a slice of time where we don't have very good ankylosaurid material in Alberta. In Alberta, we're in the lower part of the Horseshoe Canyon Formation – probably Anodontosaurus was found here around that time, but we don't have too many good specimens. Was it possible that Ziapelta roamed through the lower HCF? Or, are Ziapelta and Nodocephalosaurus characteristic of a southern Laramidian dinosaur fauna, like we seem to be seeing with some of the slightly older formations in Alberta (Dinosaur Park Formation) and Utah (Kaiparowits Formation)? Only more specimens will help us answer those questions.

I'm very grateful to Bob Sullivan, who found these specimens, for inviting me to help out with this paper, and to Spencer Lucas at the New Mexico Museum of Natural History and Science for his hospitality during my visit in 2012 to study the specimen. I hope one day I can have a chance to do some fieldwork in New Mexico, although I fear my thick Canadian blood would not serve me well and I would pretty much immediately die from the heat. Mike Burns and I had a great visit to Albuquerque in June 2012 to study the specimen, but boy howdy was it hot there. Ziapelta is housed at the New Mexico Museum and will be on display there, so if you're in the neighbourhood go say hi for me!

You can read all about Ziapelta in our open access paper in PLOS ONE!

Arbour VM, Burns ME, Sullivan RM, Lucas SG, Cantrell AK, Fry J, Suazo TL. 2014. A new ankylosaurid dinosaur from the Upper Cretaceous (Kirtlandian) of New Mexico with implications for ankylosaurid diversity in the Upper Cretaceous of western North America. PLOS ONE 9:e108804.

Ninja-edit! I would be severely remiss in not linking to some of the thoughtful news coverage we were very lucky to receive for this paper!
* Brian Switek covers our research at Laelaps: "Ziapelta - New Mexico's newest dinosaur."
* Hear my weirdo voice on the CBC's Edmonton AM!
* And via the University of Alberta, "New dinosaur from New Mexico has relatives in Alberta."

More papers!

Burns ME, Sullivan RM. 2011. A new ankylosaurid from the Upper Cretaceous Kirtland Formation, San Juan Basin, with comments on the diversity of ankylosaurids in New Mexico. New Mexico Museum of Natural History and Science Bulletin 53:169-178.

Ford TL. 2000. A review of ankylosaur osteoderms from New Mexico and a preliminary review of ankylosaur armor. New Mexico Museum of Natural History and Science Bulletin 17:157-176.

Sullivan RM. 1999. Nodocephalosaurus kirtlandensis, gen. et sp. nov., a new ankylosaurid dinosaur (Ornithischia: Ankylosauria) from the Upper Cretaceous Kirtland Formation (Upper Campanian), San Juan Basin, New Mexico. Journal of Vertebrate Paleontology 19:126-139.

Did the sauropod Leinkupal survive the End Cretaceous mass extinction?

No.

Discovery News has a short video up discussing a new paper in PLOS ONE, Gallina et al.'s "A diplodocid sauropod survivor from the Early Cretaceous of South America". I think it is really great that they want to showcase this interesting new find! But the DNews report leaves an awful lot to be desired.

The news report is titled "There's a dinosaur that survived mass extinction!", which would lead most people to think that some kind of post-Cretaceous dinosaur has been discovered. At about 25 seconds in, the reporter says this is the first time scientists have found a dinosaur that survived the great extinction, presumably referring to the End Cretaceous mass extinction that happened 66 million years ago. Right away, it seems that there's a huge misunderstanding here – there have been multiple mass extinctions in the history of life, not just the one that killed the non-avian dinosaurs. Additionally, the 'great extinction' should really refer to the End Permian extinction, by all accounts the most devastating mass extinction ever.

Anyway, Gallina et al. have described a new diplodocid sauropod, called Leinkupal, from the Early Cretaceous (probably about 140-130 million years ago) in Patagonia. This is significant because diplodocid sauropods were pretty abundant in Jurassic rocks from North America, Europe and Africa, but seem to have disappeared from the fossil record after the Jurassic. Since diplodocids were present in the Jurassic of Africa, it was also thought that they were probably present in the Jurassic of South America, but no fossils had ever been found. So, Leinkupal confirms one hypothesis (that diplodocids were present in South America), and also rejects another (diplodocid sauropods went extinct at the end of the Jurassic). Good stuff all around! But Leinkupal does not tell us that dinosaurs survived the 'great extinction' (whatever that is), and it certainly did not survive the End Cretaceous extinction, on account of it having been dead for about 70 million years before that happened.

Vertebrae from Leinkupal, from Gallina et al.

This little video is an amazing microcosm of misconceptions about evolution and palaeontology, and it's really frustrating to see this coming from Discovery News. Here's some other little snippets:

* "The diplodocid sauropod is a family" – I hate to nitpick over grammar (wait, who am I kidding – I love nitpicking over grammar!), but the grammatical failure here I think represents a pretty basic misunderstanding of how taxonomy works. Later on, the reporter says of diplodocids that "the species was thought to be an exclusively North American dinosaur". Diplodocids are a subset of sauropods, in the same way that sauropods are a subset of dinosaurs. Diplodocidae is the formal 'family' name for this group, and Diplodocidae contains many genera and species. Some of these are familiar, like Diplodocus and Apatosaurus, some are less familiar, like Tornieria and some are new, like Leinkupal. We use classification systems to understand how animals are related to each other, and to understand the scale of certain biogeographic patterns. Getting this stuff right is both relatively easy and also important!

The imposing figure of "Seismosaurus" hallorum, a diplodocid from New Mexico on display at the New Mexico Museum of Natural History & Science. "Seismosaurus" is thought by some authors to be the same genus as Diplodocus.

*At one point, the reporter says that diplodocids were "assumed to have gone extinct", which is kind of true but also takes a lot of the science out of the story! Palaeontologists didn't just assume diplodocids were extinct, they observed the pattern in the fossil record in which diplodocids were present in some layers and then not in others, and concluded that either 1) diplodocid sauropods went extinct at the end of the Jurassic or 2) we have incomplete data, and sauropods may just not be preserved in the post-Jurassic rocks we've looked at. It turns out that the latter idea was correct!

* The reporter comments that the Patagonian discovery is the earliest record of diplodocids. It's easy to get mixed up with this sometimes, but Leinkupal represents the youngest, and therefore latest record of the group. The earliest record of a group would be the first record, and therefore the oldest record. Since this is the main point of this story, they should really get this right!

* The reporter also states that Leinkupal was found in a place that palaeontologists never expected (South America), when in fact the biogeographic pattern of known diplodocids hinted strongly at the possibility of South American diplodocids. This is so great! We were able to use our knowledge of the fossil record to predict where we might find a kind of dinosaur that we had not found there before.

* Finally, the segment opens with the reporter making a show of how hard it is to pronounce the new dinosaur's name. It's true that Leinkupal doesn't have the familiar Something-saurus structure that lots of dinosaurs have, but it's not overly difficult to pronounce. There are two things that bother me here: 1) Why, Discovery News, are you making your female presenter pretend to be dumber than she surely is? and 2) An unfamiliar foreign word is made out to be this super weird and difficult thing, when they could have taken a moment to point out that this unusual name means "Vanishing family" in Mapudungun. It's a beautiful and evocative word that reflects the significance of the specimen, and highlights a local language that most of us are not familiar with. A moment that could have been used to learn something new was instead used to indicate that new things are weird and learning is hard.

This is really shallow and lazy writing. All of the important points to cover in a video segment of this length can be found in the three-paragraph introduction of the open-access paper. There's no excuse to not get it right. Instead of highlighting how this discovery shows the power of scientific predictions, we got a video that can't get basic facts correct, and pretends that this stuff is really hard rather than working to make it accessible to everyone.

What I Did on My Summer Vacation: Take the Left Turn at Albuquerque

I visited the New Mexico Museum of Natural History in June for a couple of days with my friend and colleague Mike Burns to look at [top secret specimen yet again, sorry!]. OH MAN was Albuquerque toasty in June. But we had a very fine time indeed eating southwest food and visiting the museum.

 

 

 

In part I liked the museum because it has such a large collection of Triassic vertebrates, which I don't really see too much of in my travels to look at Late Cretaceous dinosaurs. I hadn't really realized just how BIG Placerias was.

 

 

 

There was a wonderful big block of Ghost Ranch Coelophysis, which you could definitely spend a good amount of time poring over.

 

 

 

And I also enjoyed the various walls-o-Triassic-skulls, like these phytosaurs.

 

 

 

I know Stegosaurus is a staple of many dinosaur halls, but the subdued yet modern pose of this particular mount is really pleasing. Note also that the manus is correctly mounted!

 

 

 

The Jurassic gallery is dominated by this Seismosaurus and Saurophaganax pair, as well as a deliciously weird but detailed mural. Many of the original bones used to create these mounts are laid out on the bases of the mounts, and there are helpful skeletal diagrams to show what original material is known.

 

 

A temporary exhibit celebrating 100 years of discovery in New Mexico reveals a new exhibit case each month. One month featured a relatively recently named tyrannosaur called Bistahieversor.

 

 

The Cretaceous hall was pretty neat, with lots of living trees and other plants and a mural of the seaside enveloping the room. Two life reconstructions of marine vertebrates of the Cretaceous, a mosasaur and the swimming bird Hesperornis, were particularly cool. I really liked the grebe feet on the Hesperornis! I'm not sure if there's any evidence for it, and now I want to find out!