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Re: [dinosaur] Ceratopsid (Centrosaurinae: Nasutoceratopsini) from Oldman Formation of Alberta (free pdf)



In light of the problems surrounding the genus _Ceratops_ (see below;
but short version - it's toast), this might be a good opportunity to
abandon the 'family' Ceratopsidae.  Instead, raise Centrosaurinae and
Chasmosaurinae to 'family' level (Centrosauridae, Chasmosauridae), so
the new 'tribes' Centrosaurini and Nasutoceraratopsini (coined by Ryan
et al. [2016]) would each become 'subfamilies': Centrosaurinae and
Nasutoceratopsinae.  Similarly, Triceratopsini would be bumped up to
Triceratopsinae within Chasmosauridae. I'm not a huge fan of these
Linnaean constructs (and the obtruse ICZN rules that govern them), but
since we seem to be stuck with them, it's clear that _Ceratops_ should
not be giving its name to any coordinated family-level taxon.

_Ceratops_ (type species _C. montanus_) is known only a pair of
postorbital horn cores and a partial occiput.  The horn cores are
quite long and dorsolaterally projecting.  _Kosmoceratops_ and
_Albertaceratops_ specimens also have long and dorsolaterally
projecting postorbital horncores (Mallon et al., 2016).
_Albertaceratops_ is a centrosaurine, whereas _Kosmoceratops_ is a
chasmosaurine; so the horns of _Ceratops_ can't even be used to sort
it into either Centrosaurinae or Chasmosaurinae.  So _Ceratops_ is
useless as a specifier.

_Ceratops_ is clearly a nomen dubium.  The only way to salvage the
name _Ceratops_ is designate a neotype that is diagnostic.  This is
highly unlikely ever to happen.  The best chance was the Judith River
Formation chasmosaurine specimen CMN 57081.  From Mallon et al.
(2016): "It is possible - even likely, given their close stratigraphic
and geological association - that ‘_Ceratops_’ and CMN 57081 are the
same species, but without conclusive evidence for such, it is
preferable to erect a new species for CMN 57081."  So CMN 57081 became
_Spiclypeus_, rather than being referred to _Ceratops_, or nominating
it as the neotype of _Ceratops_.  This was undoubtedly the best
decision.  The nasutoceratopsin skull MOR 692 (tentatively regarded as
an adult _Avaceratops_ by Penkalski and Dodson [1999], but removed
from _Avaceratops_ by Ryan et al. [2016]) comes from the Coal Ridge
Member of the Judith River Formation, like _Spiclyepus_; but MOR 692
is an even weaker choice than CMN 57081 to become a _Ceratops_
neotype.

The only reason to nominate a neotype for _Ceratops_ at all would be
for book-keeping/nomenclatural reasons: _Ceratops_ is the name-giver
for Ceratopsidae and coordinated taxa like 'superfamily'
Ceratopsoidea.  (Ceratopsia, Ceratopsomorpha etc are fine, because
they are exempt from ICZN rules.)  But promoting Centrosaurinae and
Chasmosaurinae to families - or simply changing the name of
Ceratopsidae to Centrosauridae - means that _Ceratops_ can be
forgotten forever.


On Wed, Dec 14, 2016 at 4:56 AM, Ben Creisler <bcreisler@gmail.com> wrote:
> The official news release with illustrations:
>
>
> Researchers name two new horned dinosaur tribes
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.cmnh.org_announcements_ceratopsian-2Dtribes&d=DgIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=IRbuPQptQNlXoZq8JovgUI5ojPaPTN8TdtaKzKaQBeA&s=dkv3SQEX9GiwGDvDZ2Y5V6unoWajl4NvLyWRRmuybuQ&e=
>  
>
> https://urldefense.proofpoint.com/v2/url?u=http-3A__phys.org_news_2016-2D12-2Dscientists-2Dredefine-2Dhorned-2Ddinosaur-2Drelationships.html&d=DgIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=IRbuPQptQNlXoZq8JovgUI5ojPaPTN8TdtaKzKaQBeA&s=v-9lru50LBa481z6Bnw8L-ce1VZgUU53Wu6t5Z9Bg9U&e=
>