Beyond the carapace: skull shape variation and morphological systematics of long-nosed armadillos (genus Dasypus)
- Published
- Accepted
- Subject Areas
- Taxonomy, Zoology
- Keywords
- Dasypus, skull, geometric morphometrics, species delimitation
- Copyright
- © 2017 Hautier et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2017. Beyond the carapace: skull shape variation and morphological systematics of long-nosed armadillos (genus Dasypus) PeerJ Preprints 5:e2924v1 https://doi.org/10.7287/peerj.preprints.2924v1
Abstract
Background. The systematics of long-nosed armadillos (genus Dasypus) has been mainly based on a handful of external morphological characters and classical measurements. Here, we studied the pattern of morphological variation in the skull of long-nosed armadillos species, with a focus on the systematics of the widely distributed nine-banded armadillo (D. novemcinctus). Methods. We present the first exhaustive 3D comparison of the skull morphology within the genus Dasypus, based on µCT-scans. We used geometric morphometric approaches to explore the patterns of the intra- and interspecific morphological variation of the skull with regard to several factors such as taxonomy, geography, allometry, and sexual dimorphism. Results. We show that the shape and size of the skull vary greatly between Dasypus species, with D. pilosus representing a clear outlier compared to other long-nosed armadillos. The study of the cranial intraspecific variation in D. novemcinctus evidences clear links to the geographic distribution and argue in favour of a revision of past taxonomic delimitations. Our detailed morphometric comparisons detected previously overlooked morphotypes of nine-banded armadillo, especially a very distinctive unit circumscribed to the Guiana Shield. Discussion. As our results are congruent with recent molecular data and analyses of the structure of paranasal sinuses, we propose that D. novemcinctus should be regarded either as a polytypic species (with three to four subspecies) or as a complex of several distinct species.
Author Comment
This is a submission to PeerJ for review.
Supplemental Information
S1
List of measured specimens (used for linear measurements and/or geometric morphometric analyses). Abbreviations: MNHN, Muséum national d’Histoire naturelle in Paris (collections Zoologie et Anatomie comparée, Mammifères et Oiseaux); BMNH, Natural History Museum in London; NBC, Naturalis Biodiversity Center in Leiden; ROM, Royal Ontario Museum in Toronto; LSU, Louisiana State University in Bâton-Rouge; AMNH, American Museum of Natural History in New York; USNM, National Museum of Natural History in Washington; IEPA, Instituto de Pesquisas Científicas e Tecnológicas do Estado do Amapá in Macapá; MHNG, Muséum d’Histoire naturelle in Geneva; KWATA, KWATA association; and PCDPC, Personal collection of Pierre Charles-Dominique.
S2
Regression of the common allometric shape vector (ASVc) on the logarithm of the centroid size for mandibles of five Dasypus species (A, R2=0.50; p<0.001) and D. novemcinctus (B, R2=0.34; p<0.001). Below, associate patterns of morphological transformation for mandibles with small (left) and large (right) centroid size. Symbols: same as in Figure 3 and 5.
S3
Regression of the common allometric shape vector (ASVc) on the logarithm of the centroid size for crania of five Dasypus species (A, R2=0.72; p<0.001) and D. novemcinctus (B, R2=0.48; p<0.001). Below, associate patterns of morphological transformation for crania with small (left) and large (right) centroid size. Symbols: same as in Figure 3 and 5.
S4
Principal component analyses with shape data corrected for allometry (PCres1 vs PCres 2) and associate patterns of morphological transformation for mandible of five Dasypus species. Symbols: blue squares, D. kappleri; black crosses, D. novemcinctus; green triangles, D. hybridus; green diamonds, D. septemcinctus; red circles, D. pilosus.
S5
Principal component analyses with shape data corrected for allometry (PCres1 vs PCres 2) and associate patterns of morphological transformation for crania of five Dasypus species. Symbols: blue squares, D. kappleri; black crosses, D. novemcinctus; green triangles, D. hybridus; green diamonds, D. septemcinctus; red circles, D. pilosus.
S6
(A) Principal component analysis (PC1 vs PC2) and associate patterns of morphological transformation for crania of five Dasypus species, including juveniles (indicated with smaller symbols) and excluding D. pilosus. (B) Regression of the first principal component on the logarithm of the centroid size (R2=0,63; p<0.001). Symbols: blue squares, D. kappleri; black crosses, D. novemcinctus; green triangles, D. hybridus; green diamonds, D. septemcinctus.
S7
Principal component analyses with shape data corrected for allometry (PCres1 vs PCres 2) and associate patterns of morphological transformation for mandibles of Dasypus specimens. Symbols: green diamonds, Bolivia; green triangle, Brazil (solid green triangles are for specimens from Amapa); green circles, Paraguay; green crosses, Peru; green squares, Uruguay; green bars, Venezuela; blue diamonds, Belize; blue “plus”, Guatemala; blue bars, Honduras; Blue squares, Mexico; blue crosses, Nicaragua; blue triangles, USA; blue circles, Costa Rica; black triangles, Colombia; black crosses, Ecuador; black stars, Panama; orange squares, French Guiana; orange crosses, Guyana; orange circles, Suriname.
S8
Principal component analyses with shape data corrected for allometry (PCres1 vs PCres 2) and associate patterns of morphological transformation for crania of Dasypus specimens. Symbols: green diamonds, Bolivia; green triangle, Brazil (solid green triangles are for specimens from Amapa); green circles, Paraguay; green crosses, Peru; green squares, Uruguay; green bars, Venezuela; blue diamonds, Belize; blue “plus”, Guatemala; blue bars, Honduras; Blue squares, Mexico; blue crosses, Nicaragua; blue triangles, USA; blue circles, Costa Rica; black triangles, Colombia; black crosses, Ecuador; orange squares, French Guiana; orange crosses, Guyana; orange circles, Suriname.
S9
Results of a posteriori classifications for the discriminant analysis performed on the cranial shape coordinates of Dasypus novemcinctus using countries as factors. Specimens with a star (*) were integrated into the analyses as ungrouped cases.
S10
Results of a posteriori classifications for the discriminant analysis performed on the cranial shape coordinates of Dasypus novemcinctus using the four subgroups (i.e., Northern, Central, Southern, and Guianan morphotypes) as factors. Specimens with a star (*) were integrated into the analyses as ungrouped cases.
S11
(A) Principal component analysis and linear discriminant analysis (B) performed on linear cranial measurements traditionally used in systematic studies. Same legend as figure 6.
S12
(A) Principal component analysis (PC1 vs PC2) and associate patterns of morphological transformation for crania of Dasypus kappleri. (B) Regression of the first principal component on the logarithm of the centroid size (R2=0.40; p<0.001). Symbols: green crosses, Peru; green bars, Venezuela; black triangles, Colombia; black crosses, Ecuador; orange squares, French Guiana; orange crosses, Guyana; orange circles, Suriname.
Dataset 1
Procrustes coordinates of the crania used in interspecific comparisons.
Dataset 2
Procrustes coordinates of the crania used in intraspecific comparisons (D. novemcinctus).
Dataset 3
Procrustes coordinates of the mandibles used in interspecific comparisons.
Dataset 4
Procrustes coordinates of the mandibles used in intraspecific comparisons (D. novemcinctus).