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Re: Horner and Goodwin on Triceratops



Jamie Stearns wrote:

I don't really see a lot of good ways to classify the various ceratop(s?)ids, myself. On one hand you have those who would make up new species for every minor horn/frill variation,

That used to be an issue, especially with the erection of new species of _Triceratops_ and _Monoclonius_. This is not so much of a problem these days.


and on the other, there are those who would dump everything into one species and cite "individual variation" to explain away the differences.

I would say that ontogeny rather than individual variation per se may explain away certain differences. For example, Sampson et al. (1997) presented a strong case that _Brachyceratops_ and _Monoclonius_ represent subadult specimens of other centrosaurines_. More recently, Norell and Makovicky (2006) suggested that _Platyceratops_, _Lamaceratops_ and _Magnirostris_ may all fall within the range of ontogenetic variation observed (or inferred) for _Bagaceratops_. (BTW, I'm not advocating the latter hypothesis; I'm just drawing attention to it as an example of differing viewpoints on taxonomy.)


I seem to recall horridus and prorsus were mainly separated on the basis of the nasal horn being anteriorly curved in prorsus, posteriorly curved in horridus,

I'm not sure this was one of the characters used to separate _T. horridus_ and _T. prorsus_, although the curvature of the brow horns and relative length of the nasal horns were cited.


Briefly, the characters were:
Length of the nose horn core (longer in _prorsus_);
Length of the rostrum anterior to the nasal horn core (longer in _prorsus_);
Length and angle of the orbital horn cores (shorter and more anteriorly inclined in _prorsus_ - 60 vs 90 degrees relative to the horizontal);
Presence of frontal fontanelle (present in _horridus_ but not _prorsus_);
Dorsal border of lower temporal fenestra (jugal in _horridus_, squamosal in _prorsus_) .


So Forster used more than just the size and angle of the horn cores to separate the two _Triceratops_ species.

similar to the situation of apertus/nasicornus in Centrosaurus [snip] Could this mean Centrosaurus species ought to be reevaluated as well?

Most _Centrosaurus_/_Monoclonius_ species have already been synonymized with _C. apertus_, including _dawsoni_, _flexus_, _nasicornis_ and _longirostris_. The species _C. brinkmani_ was recently erected by Ryan and Russell (2005), based on differences in horn core morphology and frill ornamentation between it and _apertus_; but these characters appear to fall outside the range of variation seen in _apertus_.


David Marjanovic wrote:

Yes, it should be, but it isn't. The ICZN now forbids the correction of "incorrect latinizations" and the like as "unjustified emendation", so we are stuck with what some call a "barbarism".

(Begin rant)

"Barbarism" is the word. Recent Chinese fossil bird papers in particular are fertile ground for badly named families. Here, incorrect latinization takes a back seat to bad spelling. Hopefully we won't be stuck with names like Aberratiodontuidae (from _Aberratiodontus_), Gansuiornithidae (from _Gansus_) and Yandangithidae (for _Yandangornis_) forever.

(Rant complete)

Cheers

Tim