INVESTIGADORES
CASSINI Guillermo Hernan
congresos y reuniones científicas
Título:
Morphological integration of native South American ungulate mandibles based on 3d landmarks
Autor/es:
CASSINI, GUILLERMO HERNÁN; MUÑOZ, NAHUEL ANTÚ; HERNANDEZ DEL PINO, SANTIAGO; VIZCAINO, SERGIO FABIÁN
Lugar:
Mendoza
Reunión:
Congreso; 4th International Palaeontological Congress The history of life: A view from the Southern Hemisphere; 2014
Institución organizadora:
International Palaentological association
Resumen:
South American native ungulates include several
extinct lineages that evolved within the context of South American Cenozoic
geographic isolation. By the late Early Miocene Santacrucian Age, the three
orders Notoungulata, Litopterna, and Astrapotheria were clearly differentiated.
Recent studies, in an ecomorphological framework, highlighted a complex
functional pattern related to habitat/diet and hypsodonty. In order to
understand these complex relationships in an evolutionary context we used
geometric morphometrics methods to evaluate the morphological integration of
two of the primary functional units of the mandible: the alveolar region and
the ascending ramus. Twenty seven mandibular three-dimensional landmarks were
digitized. Principal component analyses (PCA), and two blocks Partial Least
Squared analyses (PLS) were used to explore the patterns of covariation between
these two modules. The PCA of tangent space coordinates resulted in the six PCs
accounting for nearly 85% of variance with the three first PCs accounting for
most of the 70% cumulative variance. The shape changes associated with the
first eigenvector go from a robust, curved mandibular corpus and expanded
coronoid and angular process on the negative end to a gracile, straight mandibular
corpus and shrunken coronoid and angular process on the positive end. The PLS
analyses show a very high RV coefficient (~0.73) and only the first pair of PLS
were significant, explaining 88% of covariation. The shape changes associated
with PLS1 were very similar to those of PC1 (angle between vectors: 5°). These
results were consistent when the PLS was repeated on the independent contrast.
These results indicate a strong morphological integration in these three
orders. In the Astrapotheria and Litopterna we found a common pattern of
covariation, which might be due to similar constraints (developmental,
functional and/or biomechanical). Conversely, in the Notoungulata the
dimensions displayed a clear distinction among species suggesting a slighty
different pattern of covariation in the different families of the order. The PLS
within the litopterns and notoungulates indicate that only PLS1 was
significant, explaining ~93% and 87% of covariation and showing higher RV
coefficients, 0.91 and 0.66, respectively. The fact that the three orders
differ in their hypsodonty could shape the morphological covariation between
the two modules. In addition, the different covariation patterns in
notoungulates with respect to litopterns are in concordance with both the
taxonomic and morphological diversity of the clade, particularly in the
typotheres.