Data for: Novel quantification of eggshell surfaces in Dromaius novaehollandiae with implications for the fossil eggshells of Oviraptorosauria (Dinosauria)

The external surface of non-avian dinosaur eggs is not usually smooth like
those of their avian descendants. Unique ornamentation patterns sculpt the
exterior of the eggs, a trait that is difficult to interpret because of
its scarcity in modern taxa. One avian species that does homoplastically,
present similar external eggshell ornamentation to that of non-avian
dinosaurs is Dromaius novaehollandiae Latham, 1790, the emu. Here we use
D. novaehollandiae eggs in conjunction with a clutch of oviraptorosaurian
dinosaur eggs (NCSM 33576, Macroelongatoolithus carlylei) to test new
methods of quantifying external eggshell ornamentation. Currently, the
only scientific language for describing and comparing ornamentation styles
in fossil ootaxa is restricted to qualitative categorization, which
introduces issues of subjectivity and overly broad and overlapping
typification. In this study, we derived and tested a new statistical
quantitative approach to quantifying ornamentation that includes two
existing functions of the molaR package in R previously applied to shape
quantifications of fossil teeth, and ‘Orientation’, a novel function
presented as a proxy for ‘direction’, needed to capture directionality.
Results demonstrate that 1) the quantitative approach provides statistical
backing to gross qualitative observations;  2) statistically
significant differences exist between the ornamentation in D.
novaehollandiae and M. carlylei, particularly in terms of relief; and 3)
intranest variation of M. carlylei can be demonstrated from harmonic mean
p-value differences between different pairs of eggs. This method offers a
strong platform to consolidate quantitative measures with existing
qualitative categories, improve the diagnoses of ootaxa, and answer broad
ecological and evolutionary questions regarding dinosaur reproduction.
Moreover, wider application of the technique is encouraged for a
multi-proxy quantitative analysis of any paleontological or biological
surfaces.