Critic analysis of regression equation models used to associate isolated postcranial bones and tooth remains: the case of the South American Paleogene ungulates.

LORENTE, M.; GELFO J. N.

La Plata

Congreso; X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología; 2010

Museo de La Plata

The taxonomy of fossil mammals is mostly based on dental characters as a consequence of the better preservation of teeth when comparing with other body parts. Paleogene South American native ungulates are well represented by teeth, and there are a large number of non-associated postcranial remains suspected to belong to them. Based on the high correlation between body mass and dental measurements, three different logarithmic equations have been proposed to assigned postcranial bones, particularly the astragalus, to the dental remains of native ungulates. These models considered the m2 area as a variable dependent or independent, and are: 1) Ln em2 areaf = -0.77 + 1.55 * Ln eastragalar lengthf, based on 10 condylarths; 2) Ln elength of the trochleaf = -0.283 + 1.345 * Ln em2 areaf, considering 6 condylarths and 2 litopterns; 3) Ln elength of the trochleaf = -0.970 + 1.698 * Ln (ãm2 area), based on 10 condylarths. In these models neither the original measurements for building the equation nor the residual standard deviation, both necessary for making predictions and calculate probabilities, are available. In order to solve this problem, a new dataset of 15 different astragalar variables, and length and width of molar series, was made from 24 articulated skeletons of bunodont artiodactyls, perissodactyls and primates. As in previous models the em2 areaf is the best dental variable to use in correlations. In contrast, for the astragalus, the ewidth of the neckf shows better r values for new dataset of 15 different astragalar variables, and length and width of molar series, was made from 24 articulated skeletons of bunodont artiodactyls, perissodactyls and primates. As in previous models the em2 areaf is the best dental variable to use in correlations. In contrast, for the astragalus, the ewidth of the neckf shows better r values for new dataset of 15 different astragalar variables, and length and width of molar series, was made from 24 articulated skeletons of bunodont artiodactyls, perissodactyls and primates. As in previous models the em2 areaf is the best dental variable to use in correlations. In contrast, for the astragalus, the ewidth of the neckf shows better r values for the regressions and higher loadings in a PCA than etotal lengthf or etrochlea lengthf. The model fit to our database was calculated and the residuals used to produce a testable and predictable model to test previous re-association inferences.