ARE SCOLOSAURUS & DYOPLOSAURUS DISTINCT TAXA?

[darren.naish@port.ac.uk]

Caleb Lewis wrote...

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What is the current status of the taxa _Dyoplosaurus 
acutosquameus_ and _Scolosaurus cutleri_? It would seem 
that some sources say that _D. acutosquameus_ is a junior 
synonym of _Euoplocephalus tutus_ or a junior synonym of 
another species of _Euoplocephalus_. Some sources say 
that _S. cutleri_ is also a junior synonym of _E. tutus_, and 
I've also heard that they are both distinct from 
_Euoplocephalus_.
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Check out...

Blows, W. T. 2001. Dermal armor of the polacanthine 
dinosaurs. In Carpenter, K. (ed) _The Armored Dinosaurs_. 
Indiana University Press (Bloomington and Indianapolis), 
pp. 363-385.

Penkalski, P. 2001. Variation in specimens referred to 
Euoplocephalus tutus. In Carpenter, K. (ed) _The Armored 
Dinosaurs_. Indiana University Press (Bloomington and 
Indianapolis), pp. 261-297.

IIRC Blows finds armour differences between _Scolosaurus 
cutleri_ and _Euoplocephalus tutus_ which lead him to 
believe that both are distinct taxa. Penkalski also reports 
differences between these two and _Dyoplosaurus_ which 
lead to the suggestion that all three are distinct taxa. Funnily 
enough, Penkalski points to Carpenter as a contemporary 
ankylosaur worker who has also (at least occasionally) 
supported distinction of _Dyoplosaurus_ and 
_Euoplocephalus_. This for example is from the archives 
(http://www.cmnh.org/dinoarch/1994Jul/msg00115.html)...

"In describing the differences, Carpenter explains that 'the 
armor of Dyoplosaurus is well known from two specimens. 
On the neck, the armor consists of rectangular keeled scutes 
(bony knobs) and flat oval scutes. The tail club is as long as 
it is wide.' The armor on the neck of Euoplocephalus, on the 
other hand, consists only of oval plates fused to an 
underlying curved band of bone. In addition, the tail club is 
wider than it is long, distinguishing it from Dyoplosaurus."

However, if you check the table in...

Carpenter, K. 2001. Phylogenetic analysis of the 
Ankylosauria. In Carpenter, K. (ed) _The Armored 
Dinosaurs_. Indiana University Press (Bloomington and 
Indianapolis), pp. 455-483.

.. you'll see both _Scolosaurus_ and _Dyoplosaurus_ treated 
as synonyms of _Euplocephalus tutus_, so maybe Ken has 
changed his mind. Distinction of all three was also favoured 
in the taxonomy Tracy provides in...

Ford, T. L. 2000. A review of ankylosaur osteoderms from 
New Mexico and a preliminary review of ankylosaur armor. 
_New Mexico of Natural History & Science Bulletin_ 17, 
157-176.

-- 
Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth UK, PO1 3QL

email: darren.naish@port.ac.uk
tel: 023 92846045