[dinosaur] Styracosaurus skull morphological variation (= Rubeosaurus jun. syn. )

Ben Creisler
[email protected]

A new paper:

Robert B.Holmes, Walter Scott Persons, Baltej Singh Rupal, Ahmed Jawad
Qureshi & Philip J. Currie (2019)
Morphological variation and asymmetrical development in the skull of
Styracosaurus albertensis.
Cretaceous Research (advance online publication)
https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1016_j.cretres.2019.104308&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=T68JAWZZTqUQc4QtYhiT3NUGcRyWpkXvFj8482WA_Gg&s=-KRSisLpI4PBSY9xVl8P-UO6au2uLRu10UcFrAI9Pec&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.sciencedirect.com_science_article_pii_S0195667119301946&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=T68JAWZZTqUQc4QtYhiT3NUGcRyWpkXvFj8482WA_Gg&s=s9A4qaeKda_MQcxGr8H-ivGrBFw9yGgTSU5VNKV0LIY&e= 


Highlights

The parietosquamosal frill of Styracosaurus albertensis is highly variable.
This variability questions taxonomic distinctions based on morphology of
the frill.
Rubeosaurus ovatus is a junior synonym of Styracosaurus.
Centrosaurus and Styracosaurus do not form an anagenic evolutionary series.


Abstract

The ceratopsid Styracosaurus albertensis is an important component of the
herbivorous dinosaur fauna preserved in the Campanian-aged Dinosaur Park
Formation in Alberta, Canada. A new skull (UALVP55900) exhibits previously
unobserved variability and asymmetry in this species. As in the type, the
right lateral parietal bar bears seven epiossifications, but the left
parietal bar has eight. Epiossifications p3‒p6 are asymmetrical with
respect to size, orientation, and position relative to the midline. A
re-evaluation of variation in Styracosaurus that includes this skull
expands the morphological range of the taxon to incorporate Rubeosaurus
ovatus, requiring the synonymy of the latter with the former. Unlike the
type, both p1 and p2 epiossifications of UALVP 55900 are large.
Epiossification p1 is procurved, and p2 is medially curved. These features
converge on the morphology considered diagnostic for Centrosaurus. This
observation, in combination with their sequential stratigraphic
relationship and geographic overlap might suggest that Centrosaurus and
Styracosaurus form an anagenic series, but the stratigraphic placement of
skulls exhibiting putative transitional morphologies does not support this
hypothesis.