Tetrapod Zoology

Another obscure ceratopsian from the defunct field guide project: for the back story go here and here.

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A distinctive chasmosaurine similar in size to a large rhino (total length approximately 3.5 m), Anchiceratops ornatus was a heavily built species with a particularly short tail and robust limbs [adjacent image from wikipedia. Not bad, but it doesn’t depict the rear margin of the frill or epoccipitals correctly]. Barnum Brown first discovered this species in 1912 in the Campanian Dinosaur Park Formation, and named it in 1914. Brown’s specimen had long, erect brow horns, leading some to suggest that it was a male. A supposed second species, A. longirostris, was named by Charles M. Sternberg in 1929 for a more lightly built specimen with shorter and more forwardly inclined brow horns from the Maastrichtian Horseshoe Canyon Formation. This specimen seems similar enough to the A. ornatus holotype to belong to the same species, though the differences have led some researchers to suggest that it represents a female (Lehman 1990, Dodson 1996).

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The best Anchiceratops specimen is the articulated, complete skeleton (NMC 8538: it lacks only the skull) collected by Sternberg in 1925 near Rumsey, Alberta, and today displayed at the Canadian Museum of Nature in Ottawa [the attached pic, ripped from a pdf of Lull (1933), is the best image I have of it, sorry. The Greg Paul reconstruction shown below is based on this specimen]. When discovered, it lay on its right side, but during mounting its orientation was reversed, such that the right side is the one that projects outwards. There is hardly any published information on this specimen: Lull (1933) provided a terse description and apparently expected a longer account to appear later on. Authors have typically noted the heavy construction of its limbs, and the shortness of its tail. There are only 38 caudal vertebrae, as opposed to a more typical 45-46 (Lull 1933, Dodson 1996). The specimen confirms that, in articulated ceratopsian skeletons, the ribs sweep strongly backwards: an observation that has obvious implications for the position of the shoulder girdle. The skull placed on the skeleton is a copy of the 1929 specimen.

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Unlike Pentaceratops and some species of Chasmosaurus, Anchiceratops lacked a concavity on the frill’s rear margin and its parietal fenestrae were relatively small. Six large epoccipitals bordered the frill’s dorsal edge and two smaller epoccipitals were located near the frill’s dorsal edge and along its midline. It had a long snout and a small, low nasal horn. In contrast to many other ceratopsians, Anchiceratops fossils come from sediments deposited in low-lying marshy environments, suggesting that it was an inhabitant of swampy regions. Langston (1959) suggested that the long face may have ‘assisted breathing while the animal crossed marshy ground or waded in shallow water’ (p. 10), and that the frill and large, heavy epoccipitals may have counter-balanced the snout when the animal was holding its snout up high, but this sounds unlikely.

For previous Tet Zoo articles on ceratopsids see…

Refs – –

Dodson, P. 1996. The Horned Dinosaurs. Princeton University Press, Princeton, NJ.

Langston, W. 1959. Anchiceratops from the Oldman Formation of Alberta. Natural History Papers, National Museum of Canada 3, 1-11.

Lehman, T. M. 1990. The ceratopsian subfamily Chasmosaurinae: sexual dimorphism and systematics. In Carpenter, K. & Currie, P. J. (eds) Dinosaur Systematics: Approaches and Perspectives. Cambridge University Press, Cambridge, pp. 211-229.

Lull, R. S. 1933. A revision of the Ceratopsia or horned dinosaurs. Memoirs of the Peabody Museum of Natural History 3, 1-175.

Comments

  1. #1 Hai~Ren
    April 20, 2009

    Ah yes, Anchiceratops. A dinosaur mentioned so often in children’s dinosaur books, but rarely if ever reconstructed.

    I’m intrigued by the fact that Anchiceratops has been found in both the Judith River and Horseshoe Canyon Formations. Is it possible that specimens were reworked? It seems quite extraordinary for this ceratopsian to stick around so long, especially when all the other ceratopsids were undergoing very quick turnover and succession of species during that time.

  2. #2 Hai~Ren
    April 20, 2009

    My bad. I meant Dinosaur Park Formation, not Judith River.

  3. #3 anon
    April 20, 2009

    Always surprising to see how long the neck actually is, for creatures that are supposed to be built like tanks and in the habit of head-bashing.

    I’ve just been Googling rhino skeletons, and their necks seem to be in general a little shorter, and frankly a little more gracile, than I’d expect.

    (Hm, now Googling hippo skeletons – seem to have roughly the same relative neck length as the Anchiceratops here.)

  4. #4 Metalraptor
    April 20, 2009

    Out of curiosity, how do we know that Anchiceratops and other ceratopsians had frills. I mean it seems just as likely that the frill could have been attached to the rest of the body by a flap of skin, and the chamber could have been filled with fatty tissue, sort of like in our neck. I think there is some modern animal skull that looks like that, but the name escapes me.

  5. #5 220mya
    April 20, 2009

    If NMC 8538 lacks a skull, how do we know it is assignable to Anchiceratops? Stratigraphy alone is not a valid criterion.

  6. #6 Matt
    April 20, 2009

    The paleoecology of Anchiceratops and other ceratopsians is an interesting topic. Dodson(1996) says the Lance beds of Wyoming where an abundance of triceratops are, were a similar environment to the Florida Everglades. Since Anchiceratops comes from a similar environment could some ceratopsians have been in an ecological role similar to the Indian or Sumatran rhino?

  7. #7 Darren Naish
    April 20, 2009

    Randy writes…

    If NMC 8538 lacks a skull, how do we know it is assignable to Anchiceratops? Stratigraphy alone is not a valid criterion.

    Good call. Lull (1933, p. 105) stated that, associated with the NMC 8538 skeleton were ‘a few diagnostic fragments of the posterior portion of the crest which determined the genus and probably the species’. So, the specimen is not devoid of cranial material entirely: I will change the text to reflect this.

  8. #8 Jerzy
    April 20, 2009

    Hmm, the head on the photo of the fossil is actually raised above the back.

    Why you think Anchiceratops was less able to raise its head above water than average hippo? Big animal cannot inhale in any case when lungs are much below the surface!

  9. #9 Warren B.
    April 20, 2009

    Anchiceratops is an obscure ceratopsian? I’m a bigger ‘ceratophile’ than I thought. Or much geekier than I thought. Same thing, probably. (Thanks for this and the Udanoceratops stuff, Darren. :) Pity it’s not going into print, though.)

    “…the ribs sweep strongly backwards: an observation that has obvious implications for the position of the shoulder girdle.”

    The squatting forelimb thing? The most I know of it is from Dodson’s The Horned Dinosaurs. Is the argument still going going on?

    “I mean it seems just as likely that the frill could have been attached to the rest of the body by a flap of skin…”

    Another half-remembered hypothesis… a palaeonotologist/artist (no idea who, at this point)illustrated ceratopsians like that, attaching the frill to the back with an enormous wedge of muscle. AFAIK the idea was thoroughly debunked, and I’d like to hear a bit more about it from someone in the know.

  10. #10 Zach Miller
    April 20, 2009

    Thanks for doing a post about one of my favorite ceratopsians, Darren. We used to think Anchiceratops was up here in Alaska, but I recently asked Tony Fiorillo what the currently valid genera are, and he said there’s no more Anchiceratops. That makes me a sad panda. Given the short tail of this genus, and the relatively short tails of other ceratopsians, one wonders how these animals used their tails (if at all).

    Here’s a question for you? How do paleo-artists decide where to attach the top of the neck to the back of the frill? Seems that different artists have different locations. Greg Paul places the top of the neck fairly high on frill, but are there osteological correlates for where the neck muscles would attach?

  11. #11 Boesse
    April 20, 2009

    Warren,

    I remember the paleo-artist you’re talking about! I remember reading an old ‘childrens’ book in the local library back home when I was 10 or 11, and seeing the illustrations, and laughing at it (even then). I guess it looked intuitively wrong to me even at such a young age. Although then (or now, really) I can’t argue against it (mainly because dinosaurs are outside of my field of study, and lame – i.e. not mammals).

    Bobby

  12. #12 Metalraptor
    April 20, 2009

    Warren B. and Zach, that is exactly what I am asking. How do we know that these creatures had frills, and that the frill did not attach to the rest of the animal through a flap of skin and perhaps a wedge of fat or muscle. I mean I think there are some animals (is it chameleons?) that have a “frill” on their skull, but on the living animal it is invisible because of the fat and muscle. I mean, I cannot think of any extant animal that has a frill like that today. Of course, just because no animal today has it doesn’t mean that the frill on ceratopsians could be just that, a frill, but I’m just trying to inject a healthy dose of skepticism here.

  13. #13 Darren Naish
    April 20, 2009

    Thanks to all for comments. Some quick responses.

    — Warren referred to the forelimb orientation issue. A few papers have been published arguing that, during locomotion, the forelimb swung in the parasagittal plane and that the elbows were only slightly angled outwards (Paul & Christiansen 2000, Senter 2007). This work might mark an end to the controversy, but I get the impression that some are still at least considering a sprawling posture (see Dodson et al. 2004, p. 511). Kent Stevens has presented DinoMorph animations that show a semi-sprawling posture.

    — Were the frills really projecting bony shields, or were they submerged in soft tissue? I think we can be pretty confident that they really did ‘stand out’ as bony shields. However, this is such an interesting issue I’ll discuss it separately in a short article (to be published tomorrow, probably). I’ll be talking about that artist whose name you’ve forgotten… ok, it’s John McLoughlin.

    — Zach asked how we know where the neck musculature attached. Very distinct attachment scars of the rectus capitis muscles are present on the supraoccipital, and they also extend onto the base of the parietals, so the muscles did incorporate the very base of the frill. I don’t know how variable this is within ceratopsians; I’ve only seen it in Triceratops.

    Refs – –

    Dodson, P., Forster, C. A. & Sampson, S. D. 2004. Ceratopsidae. In Weishampel, D. B., Dodson, P. & Osmólska, H. (eds) The Dinosauria, Second Edition. University of California Press (Berkeley), pp. 494-513.

    Paul, G. S. & Christiansen, P. 2000. Forelimb posture in neoceratopsian dinosaurs: implications for gait and locomotion. Paleobiology 26, 450-465.

    Senter, P. 2007. Analysis of forelimb function in basal ceratopsians. Journal of Zoology 273, 305-314.

  14. #14 David Marjanović
    April 20, 2009

    Out of curiosity, how do we know that Anchiceratops and other ceratopsians had frills. I mean it seems just as likely that the frill could have been attached to the rest of the body by a flap of skin,

    Difficult to imagine because of the mobility of the head on the neck, and the sheer size of the frill in some chasmosaurines…

    and the chamber could have been filled with fatty tissue, sort of like in our neck.

    There’s fatty tissue in my neck? Where? What do you mean? ~:-|

  15. #15 jck
    April 20, 2009

    A question about the tail; It seems like although the tail is small, it looks to have been very flexible. Would that make it useful for swatting pests, like cattle and horses do today? If some ceratopsians had quills along the tail, would it be possible for the quills on other ceratopsians to be longer and thinner, like the hair on a horse’s tail?

  16. #16 Zach Miller
    April 20, 2009

    Thanks, Darren. I’ve always wondered about that.

    Metalraptor: Chameleons do, indeed, have distinct frills formed by the same bones as in ceratopsians. However, usually, the frill is separate from the “neck meat.” I’ve had two Jackson chameleons, and while their frills are short, they were not attached to the neck. There are, of course, exceptions. Meller’s chameleon has a uniquely-shaped frill that connects to the neck because of the wavy back. However, yet other chameleons have very large frills (specifically the veiled chameleon). Besides, chameleon frills are more triangular in horizontal cross-section that ceratopsian frills, which are pretty flat.

  17. #17 Jenny Islander
    April 20, 2009

    Can anybody point me to a plausible summary of dinosaurs and other fauna and their habitat for a given location and time? Something like “Wildlife of the Serengeti for Armchair Enthusiasts,” with the nifty spread of assorted antelope and gazelle species, each standing in a sample of its habitat? I tend to turn up either extremely technical discussions about teeth or a bland statement that dinosaur X probably ate plant types Y and Z, or alternatively a description of a biome without mention of what was walking around in it.

    It really seems counterintuitive to me that I can find so many articles that go into depth about the known anatomy of a given beastie, end with speculation about what it did with said parts, but don’t mention any associated fossils or paleogeographic evidence. Isn’t it obvious that you need to look at what was living nearby, and in what type of habitat, when trying to figure out what a beastie ate? Is there a hiccup in the process of analyzing fossil finds that accounts for this? Or am I just looking in the wrong parts of the Intartubes?

  18. #18 Metalraptor
    April 20, 2009

    Thanks Darren and Zach, just curious about that. And David, I have this picture of a human neck in cross section, and there is a big lump of what looks like fatty tissue that smooths out the head and doesn’t make the back of our cranium stand out so much. I think its neural tissue, though I am not sure, the print on this is very small.

  19. #19 Boesse
    April 20, 2009

    Jenny,

    Excellent question, which is answerable within the realm of paleoecology. Unfortunately, it is often extremely difficult to attempt any sort of meaningful reconstruction of trophic structure. There are two ways to go about this – direct and indirect ‘evidence’ of trophic structure. Direct evidence includes gut residues, and shed teeth/identifiable tooth marks. Indirect evidence includes relative abundance, feeding ecology diversity, and size diversity. Unfortunately, the indirect evidence is extremely sensitive to taphonomic bias, and there is no guarantee that the fossil record EVER consitutes a random sample of the living fauna. In most cases, making an assumption of a random sample without removing the taphonomic overprint correctly (which is likely incredibly difficult if not impossible to tell) is an indefensible position.

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