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Canis dirus and Smilodon Procrustes coordinates

Citation

O'Keefe, Frank (2022), Canis dirus and Smilodon Procrustes coordinates, Dryad, Dataset, https://doi.org/10.5061/dryad.d7wm37q01

Abstract

The primary goal of this paper is to examine and rationalize different integration metrics used in geometric morphometrics, in an attempt to arrive at a common basis for the characterization of phenotypic covariance in landmark data. We begin with a model system; two populations of Pleistocene dire wolves from Rancho La Brea that we examine from a data-analytic perspective to produce candidate models of integration. We then test these integration models using the appropriate statistics and extend this characterization to measures of whole-shape integration. We demonstrate that current measures of whole-shape integration fail to capture differences in the strength and pattern of integration. We trace this failure to the fact that current whole-shape integration metrics purport to measure only the pattern of inter-trait covariance, while ignoring the dimensionality across which trait variance is distributed. We suggest a modification to current metrics based on consideration of the Shannon, or information, entropy, and demonstrate that this metric successfully describes differences in whole shape integration patterns. Our new metric allows detailed comparison of the hyperellipses occupied by the two populations in morphospace (which is a form of covariance space). Finally, the information entropy approach allows comparison of whole shape integration in a dense semilandmark environments, and we demonstrate that the metric introduced here allows comparison of shape spaces that differ arbitrarily in their dimensionality and landmark membership.

Methods

These data comprise two dimensional landmark data from left jaws of the dire wolf, Canis dirus, from Rancho La Brea, California. The landmarks were digitized from photographs of the specimens.

Usage Notes

The data set contains the following fields:

Genus: This is Canis dirus, or Smilodon. Most the analyses in the paper concern Canis dirus, but we discuss the Smilodon data briefly in the discussion.

Specimen/Photograph ID: This is the specimen number of the fossil photographed for Canis dirus. For Smilodon it is the photograph number indexed to data in:

Meachen, J.A., O'Keefe, F.R. and Sadleir, R.W., 2014. Evolution in the sabre‐tooth cat, S milodon fatalis, in response to P leistocene climate change. Journal of Evolutionary Biology27(4), pp.714-723.

Pit: The Rancho La Brea pit deposit of origin for each fossil.

LMnx,y: Original digitized landmark coordinates for Canis dirus jaws. These data are not included for Smilodon because we do not use them in the paper.

1.x,y: Generalized Procrustes Analysis (GPA) transformed coordinates for Canis dirus and Smilodon.

Centroid Size: This is the centroid size vector yielded by the GPA analysis.

Funding

Division of Environmental Biology, Award: NSF EAR-SGP 1757236