Aquilops americanus is not a neoceratopsian

Aquilops americanus was described 
by Farke et al. 2018, “The taxon is interpreted as a basal neoceratopsian closely related to Early Cretaceous Asian taxa, such as Liaoceratops and Auroraceratops.” This may be due to taxon exclusion.

Aquilops is much more primitive
than neoceratopsians, like Chasmosaurus and Triceratops, according to the large reptile tree (LRT, 1304 taxa; subset Fig. 1) which nests Aquilops between Laquintasaura and Hexlinusaurus, both basal to the psittacosaur – ceratopsian split. Both were excluded from the Farke et al. study.

Figure 1. Aquilops nests at the base of psittacosaurs + ceratopsians in the LRT. Pachycephalosaurs, like Stegoceras, are not the sisters to ceratopsians.

Figure 1. Subset of the LRT focusing on the Ornithischia where Aquilops nests at the base of psittacosaurs + ceratopsians in the LRT. Pachycephalosaurs, like Stegoceras, are not the sisters to ceratopsians.

Distinct from Laquintasaura,
Aquilops has an eagle-like hooked rostral bone (Fig. 2) and retains an antorbital fenestra with fossa. It was likely a biped, based on phylogenetic bracketing. Here (Fig. 1) skull only Auroraceratops nests with skull-less Stenopelix at the base of the Neoceratopsia. Liaoceratops nests with Psittacosaurus and Yinlong. We’ll look at them in future posts.

Figure 2. Aquilops skull as restored and as discovered.

Figure 2. Aquilops skull as restored and as discovered. The squamosal has been artificially restored with a parietal shield in the restoration, traits not preserved in the partial material. 

References
Farke AA, Maxwell WD, Cifelli RL and Wedel MJ 2014. A Ceratopsian Dinosaur from the Lower Cretaceous of Western North America, and the Biogeography of Neoceratopsia. PLoS ONE. 9 (12): e112055. doi:10.1371/journal.pone.0112055

wiki/Aquilops
https://p3d.in/G34T8+welcome
https://samnoblemuseum.ou.edu/collections-and-research/vertebrate-paleontology/discovering-aquilops-americanus/

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