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RE: Protoceratops juvies, unfenestrated parietal (repost)
Denver Fowler wrote:
<Not relevant? Of course they are relevant. Protoceratops parietal
fenestration through ontogeny sets a precedent, especially as Proto is a
more basal taxon. Regardless of whether or not you agree with
trike-toro synonomy, most people accept that Triceratops is paedomophic
(in many aspects of its morphology). This at least is consistent with
retention of unfenestrated parietal until late in ontogeny.>
My qualification was "relevant in _late_ ontogeny," and as such I am making a
statement about relative _time_. Since, as you also note, as the
"triceratopsin" group is considered paedomorphic, if it were, this is unique to
the group among all of *Coronosauria* within *Ceratopsia*; it is as unique as
having a character "parietal fenestrae present/not present" be effectively
uncodable save for the complex of species lumped into *Triceratops*. This is,
incidentally, why I put the name *Triceratops* in quotes in my last two
replies: the assumptions made by Scannella and Horner are without respect to
species-level distinctions, and thus the assumptions are made on a presumed and
untested "generic" qualification. *Protoceratops andrewsi* parietal
fenestration is as relevant as *Pachyrhinosaurus lakustai* fenestration, and is
thus irrelevant to the particulars of late-ontogeny expression. My statement
was also in regards to the argument that Scannella and Horner had made the infe!
rence that post-hatchling ontogeny produces the fenestrae, but this is a "duh"
moment: The Polish-Mongolian team has made a number of discoveries of specimens
that have been argued to merely be juvenile *Protoceratops andrewsi,* and these
specimens have unfenestrated parietals. *Bagaceratops rozhdestvenskyi*
especially has been questioned as an adult taxon, which is certainly testable,
and recent taxa like *Magnirostris dodsoni* (see Makovicky & Norell, 2006, and
Osi et al., 2010). But *Triceratops horridus* (at least) is doing something
different, regardless of Scannella and Horner's hypothesis, and I'm not sure
there's a whole lot of equating their ontogeny to *Protoceratops andrewsi*,
merely distinguishing them; thus, [I do not think that] they are not "relevant
in _late_ ontogeny."
<"can be true"? If these little dinosaurs are indeed Protoceratops, then it IS
Maybe. They _are_ juveniles, and are at least protoceratopsid, but are they
*Protoceratops*? Are they *Protoceratops andrewsi*? Are they actually? Given
the number of distinct adult _theropod_ taxa that have been recovered from the
Djadokhta, how certain are you that any large-bodied ceratopsian is the same
taxon? Sure, one can make the assumption that similar taxa will have similar
ontogenies, but the diagnosis of taxa should be done without simple assumption
of lumping. Fastovsky et al. (2011:pg.1037) are aware of this:
"In addition to indicating their immature status, several features of the
skull, including the relatively flat, straight snout and the short,
parallel-sided frill, also constitute the plesiomorphic condition for
Ceratopsia (Balanoff et al., 2008). In these features, these ceratopsians
resemble the adults and juveniles of more basal members of this clade, like
*Psittacosaurus* spp. (Long and McNamara, 1995; Meng et al., 2004; Zhao et al.,
2007), *Liaoceratops*, and *Auroraceratops* (You and Dodson, 2004).
"For all that, however, several characters suggest *Protoceratops* affinities
including an eliptical antorbital fossa, median keel on the frill, small
fronto-parietal depressions (Dong and Currie, 1983; You and Dodson, 2004), and
hoof-shaped pedal unguals (Sereno, 2000). Within *Protoceratops*, two species
are recognized: *P. andrewsi* (Granger and Gregory, 1923) and *P.
hellinkorhinus* (Lambert et al., 2001). Of the characters that distinguish the
latter from P. andrewsi-the absence of premaxillary teeth, two nasal horns,
well-developed frontoparietal depressions, and a forwardly curved frill (You
and Dodson, 2004)-the presence or absence premaxillary teeth has the potential
to diagnose; the other characters are simply not well developed within these
juvenile skeletons. In the case of the teeth, however, insufficient preparation
precludes positive identification of the character, even presuming that at this
juvenile stage they would have erupted. There are, however, no reas!
ons to preclude a specific assignment to *P. andrewsi*, and given the fact that
adult *Protoceratops andrewsi* are the only ceratopsians known from Tugrikin
Shire (Brown and Schlaikjer, 1940; Dodson, 1976; Dong and Currie, 1993; Lambert
et al., 2001), we tentatively refer all of the individuals in MPC-D 100/530 to
*P. cf. andrewsi*."
Unable to distinguish the species by morphology (assuming the morphology is
consistent that young), the authors use _locality_ to presume identity. The
authors use "cf." as a label to suggest their uncertainty on this, and this is
almost certainly a label of convenience.
<Ah "problematic". Fenestrae open through ontogeny in Protoceratops.
Maybe we should just ignore these specimens because they are so much of a
I think I covered this above: The "problem" is that they open _at different
times_ between *Triceratops horridus* (say, using Scannella and Horner's
hypothesis) and *Protoceratops andrewsi* (using Fastovsky et al's) -- since the
opening through ontogeny is not understood throughout *Ceratopsia* it is
"problematic" to assume one's ontogeny says anything about the other's. It is
also a concern that juveniles are problematic when attempting to identify
_species_, when similar species will have juveniles that are largely
<Why did Triceratops have a solid frill at all? Why have brow horns? why
elongate the rostrum? why start developing a big nasal or? Why
morphology? For Triceratops: differential paedomoprhism (more prevalent)
and permorphism. Heterochrony. That's where we are right now.>
Yes, it would be great to get an answer to the first question. Why indeed? I
won't delve into the conflicts surrounding whether or not heterochrony is
useful in this regard, when we lack the refined degree of analysis that
observing living organisms provides.
<Different species have different growth trajectories. Protoceratops
developing fenestrae ontogenetically shows that the tendency/ability to
do so was present in a more basal ceratopsian. Sorry that this rocks
your world so badly you choose to ignore it.>
I completely understand how you got this from what I said, the borderline
misrepresentation notwithstanding. That there are _other_ ceratopsians with
parietal fenestrae should indicate that it is present in, at the least, their
common ancestor. That adults of *Protoceratops andrewsi* have parietal
fenestrae should be the relevant data. _Of course_ they open ontogenetically,
as the basal condition _lack_ them (e.g., *Psittacosaurus* spp.), and the
_inferrence_ is that there will be a point at which they will open in
descendants. That those _times_ are different in different taxa is my point.
How is the earlier timing relevant in *andrewsi* compared to *horridus* when we
don't understand the timing in an intermediate?
<Does Avaceratops have fenestrae? Does Brachyceratops have fenestrae? Can
Are those taxa "real"? Are they ontogenetic stages of other, known taxa? Can
we know? Should we value juvenile or subadult taxa as holotypes when that level
of uncertainty towards diagnostic characteristic exist?
<Is parietal thinning in these taxa indicative of incipient
fenestrae? Fenestration is 1:0, present or absent; what would incipient
fenstrae look like? how would you code it? Is extreme parietal thinning
different from 2 inch thick solid frill? why? How many complete
parietals exist for Triceratops? How many are incomplete? How many of
those incomplete specimens are conveniently broken where the fenestrae
(incipient or otherwise) would be? When do fenestrae form in
ceratopsids? in the egg? through ontogeny? Protoceratops says through
Something tells me you're trying to compare the ontogeny versus biomechanical
reduction model of Tanke and Farke. You're also trying to say, it seems, that
only one model can be true, for the whole of ceratopsians. What if
chasmosaurine ceratopsids developed fenestrae early, and in one lineage, closed
them, which then opened up under biomechanical resorption at extreme age? Can
both models truly, _truly_ be true? It's not the most _parsimonious_ argument
when taken on the face of it, but it might be just as accurate. And as I said
before, maybe it varies across taxa, so that one taxon is no accurate model for
another. It would be a mistake then to presume that the fenestrae of
*Torosaurus latus* are homologous to those of *Protoceratops andrewsi*, if they
arise under biomechanical conditions that can differ across even closely
Fastovsky, D. E., Weishampel, D. B., Watabe M., Barsbold R., Tsogtbaatar K. &
Narmandakh P. 2011. A nest of *Protoceratops andrewsi* (Dinosauria,
Ornithischia). _Journal of Paleontology_ 85(6):1035-1041.
Makovicky, P. J. & Norell, M. A. 2006. *Yamaceratops dorngobiensis*, a new
primitive ceratopsian (Dinosauria: Ornithischia) from the Cretaceous of
Mongolia. _American Museum Novitates_ 530:1-42.
Ősi, A., Butler, R. J. & Weishampel, D. B. 2010. A Late Cretaceous ceratopsian
dinosaur from Europe with Asian affinities. _Nature_ 465:466-468.
Tanke, D. H. & Farke, A. A. 2007. Bone resorption, bone lesions and extra
cranial fenestrae in ceratopsid dinosaurs: a preliminary assessment. pp.319-347
in Carpenter (ed.) _Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs_.
(Indiana University Press, Bloomington.)
Jaime A. Headden
The Bite Stuff (site v2)
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion
> Date: Fri, 11 Nov 2011 19:14:04 +0000
> From: firstname.lastname@example.org
> To: email@example.com
> Subject: Re: Protoceratops juvies, unfenestrated parietal (repost)
> ----- Original Message -----
> From: Jaime Headden <firstname.lastname@example.org>
> > In "Triceratops," Scannella and Horner infer the fenestrae open _only_
> during adulthood, discretely classifying a "young adult" above the "subadult"
> stage which acheived adult size and frill characteristics, no fenestrae, but
> are not "old adult" which is reserved for specimens ascribed to *Torosaurus
> latus* and *gladius*.
> Yes. Triceratops ontogeny is not identical to Protoceratops.
> > The relative size of the fenestrae in the parietals in *Protoceratops
> > andrewsi* do not appear, in this small sample, to be relevant in _late_
> > ontogeny, which was Scannella and Horner's argument for "Triceratops."
> Not relevant? Of course they are relevant. Protoceratops parietal
> fenestration through ontogeny sets a precedent, especially as Proto is a more
> basal taxon. Regardless of whether or not you agree with trike-toro synonomy,
> most people accept that Triceratops is paedomophic (in many aspects of its
> morphology). This at least is consistent with retention of unfenestrated
> parietal until late in ontogeny.
> > Based on the photo below, the skulls of these juveniles appear to be about
> > 50mm, so smaller than the smallest specimen Dodson sampled, and thus the
> > assertion that fenestrae appear "somewhere post-hatching ontogeny" can be
> > true,
> "can be true"? If these little dinosaurs are indeed Protoceratops, then it IS
> >but the arguments for any sort of comparison is problematic.
> Ah "problematic". Fenestrae open through ontogeny in Protoceratops. Maybe we
> should just ignore these specimens because they are so much of a problem.
> >Why did the frill open up so extremely late in *Triceratops horridus* or
> >*prorsus* ontogeny?
> Why did Triceratops have a solid frill at all? Why have brow horns? why
> elongate the rostrum? why start developing a big nasal or? Why morphology?
> For Triceratops: differential paedomoprhism (more prevalent) and permorphism.
> Heterochrony. That's where we are right now.
> >But it certainly wasn't the same timing as *Protoceratops an
> Different species have different growth trajectories. Protoceratops
> developing fenestrae ontogenetically shows that the tendency/ability to do so
> was present in a more basal ceratopsian. Sorry that this rocks your world so
> badly you choose to ignore it.
> Does Avaceratops have fenestrae? Does Brachyceratops have fenestrae? Can we
> know? Is parietal thinning in these taxa indicative of incipient fenestrae?
> Fenestration is 1:0, present or absent; what would incipient fenstrae look
> like? how would you code it? Is extreme parietal thinning different from 2
> inch thick solid frill? why? How many complete parietals exist for
> Triceratops? How many are incomplete? How many of those incomplete specimens
> are conveniently broken where the fenestrae (incipient or otherwise) would
> be? When do fenestrae form in ceratopsids? in the egg? through ontogeny?
> Protoceratops says through ontogeny.