[dinosaur] 'Vagaceratops' irvinensis is species of Chasmosaurus (free pdf)

Ben Creisler
[email protected]

Not yet mentioned, a new paper in open access:


James Alexander Campbell, Michael J. Ryan, Claudia J. Schroder-Adams,
Robert B. Holmes & David C. Evans (2019)
Temporal range extension and evolution of the chasmosaurine ceratopsid
'Vagaceratops' irvinensis (Dinosauria: Ornithischia) in the Upper
Cretaceous (Campanian) Dinosaur Park Formation of Alberta.
Vertebrate Anatomy Morphology Palaeontology 7: 83-100
DOI: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.18435_vamp29356&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ksr5CF9_j6yuqI44wFoMrr6oSt8-Gq6ngEYwXvC5Y0I&s=QxDM4EWw064ZdZoVsNEnCuswcw1syumxk98bFkTvBKM&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.library.ualberta.ca_vamp_index.php_VAMP_article_view_29356&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ksr5CF9_j6yuqI44wFoMrr6oSt8-Gq6ngEYwXvC5Y0I&s=ECENqJBpSwSfhszLLUrcMBbdZeqvlfhzg1rs3EboEhw&e= 

Free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.library.ualberta.ca_vamp_index.php_VAMP_article_view_29356_21410&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ksr5CF9_j6yuqI44wFoMrr6oSt8-Gq6ngEYwXvC5Y0I&s=MqOxb5c8FA6fadpwyhR78NiXWcB_rvfFpbKOY_4hWyw&e= 

The Dinosaur Park Formation (DPF) has a diverse assemblage of
chasmosaurines currently represented by Chasmosaurus belli, C. russelli,
Vagaceratops irvinensis, and Mercuriceratops gemini, and may also include
remains possibly referable to Spiclypeus shipporum. Two skulls, YPM 2016
and AMNH 5402, previously referred to C. belli, both have a straight
posterior parietal bar with five epiparietals present (YPM 2016) or
inferred (AMNH 5402) on each side – the combination of which is unique to
V. irvinensis. Based on our new morphological observations and
interpretations of these two skulls, we recover V. irvinensis as a species
of Chasmosaurus (C. irvinensis), although the interrelationships between C.
irvinensis, C. belli, and C. russelli remain unclear. We refrain from
formerly assigning YPM 2016 and AMNH 5402 to C. irvinensis, however, as
their parietal fenestrae are significantly larger and their epiparietals
are significantly shorter than those of C. irvinensis; instead, we reassign
these two skulls to Chasmosaurus sp. Given the low stratigraphic position
of YPM 2016 (unknown in AMNH 5402) relative to C. irvinensis, we believe
this specimen to represent a basal member of the lineage leading to C.
irvinensis. If our assessment is correct, this would indicate that the C.
irvinensis lineage has a large degree of stratigraphic overlap with that of
C. belli and C. russelli. The close phylogenetic relationship and supposed
stratigraphic separation for these three taxa reported in previous studies
were used to suggest that they may represent an anagenetic lineage, whereby
C. russelli evolved into C. belli, and C. belli evolved into, and was
entirely replaced by, the latter. However, the lack of stratigraphic
separation between these three taxa indicates that they instead arose via
cladogenesis.

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