Archosauria: Avemetatarsalia to Neornithes
2° Nominal Author
Currie and Padian (1997) were first to define Marginocephalia. Independently, Sereno (1998) proposed a very similar definition using genera. Marginocephalia includes two well defined subclades, pachycephalosaurs and ceratopsians. Because there is some uncertainty regarding the monophyly of the clade, negative taxon qualifiers ensure that major external groups will not be included within Marginocephalia. The active definition is a first-order revision of both of these previous definitions.
Inactive Taxon Status
Current Age Range
Berriasian (146 Ma)
Maastrichtian (66 Ma)
Basis for Range
The earliest record is Berriasian-age
from the Obernkirchen Sandstone of Germany. The latest record is Maastrichtian-age pachycephalosaurs and ceratopsians from Asia and western North America (Weishampel et al. 2004). Dates are rounded to the nearest million, the earliest from the beginning of the stage and the latest from the end of the stage (Gradstein et al. 2004).
Definitional History #1
Ceratopsia and Pachycephalosauria and all descendants of their most recent common ancestor.
Currie and Padian 1997:415
Definitional History #2
, their most recent common ancestor and all descendants.