Sample of intra- and interspecific shell shapes, quantified as closed outlines using 7 harmonics and elliptic Fourier analysis, from 4 species of the extinct genus Ptychomya (Bivalvia: Crassatellidae).
shellsA list containing:
an "OutCoe" object containing a 137 x 28
matrix with the normalized Fourier coefficients describing the outline
of the shell of each specimen in left lateral view.
a vector of length 137 containing the centroid size of each fossil shell.
a 4-column data frame with information about the taxonomic classification, ammonoid biozone, estimated geochronologic age (in million years), and geographic provenance of each fossil shell.
The shells data contain data from 137 specimens belonging to
4 species of the extinct bivalve genus Ptychomya, tracking their
morphological changes through a 5 million years interval from the Lower
Cretaceous of west-central Argentina (approximately 140 million years ago).
The data set includes the information about the external shell shape (measured
using Fourier coefficients from 7 harmonics), centroid size, age (both relative,
taken from ammonoid biozones, and absolute, estimated using a combination
of the former, absolute dates, and stratigraphic data), geographic provenance,
and taxonomic classification of each fossil specimen.
Milla Carmona, P. S., Lazo, D. G., & Soto, I. M. (2018). Morphological evolution of the bivalve Ptychomya through the Lower Cretaceous of Argentina. Paleobiology, 44(1), 101-117.