Monday, 18 February 2013

M is for Mojoceratops

Moving on to the letter 'M', we welcome another ceratopsian (horned) dinosaur to our Alberta dinosaurian alphabet with Mojoceratops

Mojoceratops has an interesting history, and invokes discussion of a common problem in palaeontology that we deal with constantly. As is often the case, Mojoceratops is known from partial remains, and in this case, it is known from several skull pieces, representing nearly an entire skull. First, Lambe found a partial skull, which he called "Eoceratops canadensis" in 1915 [1]. Unfortunately, this was based on a skull with no descriptive characters, and furthermore, is a juvenile. A few years later, Brown found another partial skull and named it "Chasmosaurus kaiseni", again from partial remains with few descriptive characters (albeit more than E. canadensis[2]. Even more difficult, a further specimen was named "Chasmosaurus canadensis". This specimen is the type specimen, of the species Mojoceratops perifania named by Nick Longrich in 2010, along with the previously mentioned specimens and other new specimens [3]. You might think the name is a bit funny, and you would be right. First of all, genus and species names are almost always derived from Latin or Greek, and 'mojo' is neither: it's derived from "20th century African-American English" [3]. Furthermore, it means just what you think it means. Longrich describes a mojo as "a magic charm or talisman often used to attract members of the opposite sex", referring to its large frill that may have been used in courtship. He distinguishes it from Chasmosaurus because it lacks a forward-curving process on the frill and reduced postorbital horns found in Chasmosaurus. Currently recognised specimens come mainly from southern Alberta in the Dinosaur Park Formation, while some may be found in southern Saskatchewan as well. The fossils come from the Late Cretaceous, about 75 million years ago. 
Artists impression of Mojoceratops perifania by Nobu Tamura. Note the large frill and orbital horns.
The complicated history of Mojoceratops makes it a somewhat controversial taxon. It does seem to be recognised as separate from Chasmosaurus, because it lacks specific features found in Chasmosaurus (like the curved processes and short orbital horns). However, the rules of zoological nomenclature are clear: the name that was first given to an animal takes precedent over any other name given to it, unless there is a valid reason not to. In the case of "Eoceratops canadensis", its non-descriptive and juvenile nature provide a good reason NOT to use this as a name. Moving to "Chasmosaurus kaiseni" provides us with another challenge. It is recognisably different from Chasmosaurus, and therefore should be given a new generic (as in the first name in species). Normally in these cases, a new generic name is erected, while the specific epithet ("kaiseni") is kept, to recognise the original name. However, Longrich chose to erect both a new generic and specific name. In one study, they refer to it as Mojoceratops kaiseni, recognising the original specific name [4]. This is often a problem in palaeontology, especially when looking at fossils that were found in the early 1900's. Making this species even more controversial, a recent study questioned its distinctiveness from Chasmosaurus [4]

In general, it's a bit of a mess, but it is currently recognised as a valid taxon. Hopefully this has given you a bit of insight into the complicated nature of naming fossils, and the struggles that follow.  Next week we'll carry on with the letter 'N', with an armoured dinosaur! 

Other 'M' dinosaurs found in Alberta:
Monoclonius (also a controversial ceratopsian)
Montanaceratops - a ceratopsian 

References
1 Lambe, L. 1915. On Eotriceratops canadensis, gen. nov., with remarks on other genera of Cretaceous horned dinosaurs. Canada Geological Survey, Museum Bulletin 12: 1-49.
2 Brown, B. 1933. A new longhorned Belly River ceratopsian. American Museum Novitates 669: 1-3.
3 Longrich, N.R. 2010. Mojoceratops perifania, a new chasmosaurine ceratopsid from the late Campanian of western Canada. Journal of Paleontology 84: 681-694.
4. Mallon, J.C., et al. 2011. Variation in the skull of Anchiceratops (Dinosauria, Ceratopsidae) from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta

2 comments:

  1. Hey dudes, great post! But I thought I'd point out one small error: Eotriceratops is actually a valid taxon (E. xerinsularis) from the Horseshoe Canyon Formation, and was named in 2007 by Wu et al. Eoceratops is the genus named by Lambe. The University of Alberta Paleontology Museum has one of the original "Eoceratops" skulls on display, UALVP 40, which was originally described by Gilmore (1923).

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  2. Thanks for pointing that out Victoria! I definitely knew that, but somehow my brain decided that it was Eotriceratops rather than Eoceratops. I'll fix that right away!

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