Análisis de variables morfométricas de Toxaster roulini Agassiz (Echinoides: Toxasteriidae) de la Formación Rosa Blanca, municipio de Zapatoca (Santander, Colombia)
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Universidad Industrial de Santander
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En la secuencia aflorante de la Formación Rosa Blanca sobre la carretera Zapatoca - Mina el Platanalito, se recolectaron directamente de los estratos que los contenían, 188 especímenes de Toxaster roulini Agassiz del Aptiano (Camacho, 1979). Se realizaron las respectivas mediciones de las variables morfométricas de los especímenes colectados: Largo 1, largo 2, ancho, alto, alto ano, distancia de la boca, con el fin de evaluar el tipo de crecimiento de estos individuos y la influencia de dichas variables en la deformación de los mismos durante el proceso de fosilización. Estos datos se procesaron aplicando regresiones lineales y correlaciones que utilizaron el programa STATISTICA versión 4.0. En el sitio de colección los individuos que predominaron (un 74.4%) se encontraban entre los 20 y 33 mm de longitud, con un ancho entre 17 y 30 mm, y una altura entre 11 y 18 mm, mostrando así, que éste es el tamaño común de la población de muestreo. Las variables alto ano y distancia de la boca constituyeron áreas específicas que no se vieron modificadas durante el crecimiento de los individuos, lo cual se confirma a partir de los bajos valores de correlación que presentan estas dos variables morfométricas con las demás. Los resultados de las regresiones y las correlaciones indican que el crecimiento de T. roulini Agassiz es isométrico y que además, existe una alteración en la variable altura inducida muy probablemente, por la presión de los estratos superiores durante el proceso de fosilización. Se plantea una hipótesis para la distribución en el hábitat de T. roulini Agassiz en la que los individuos de tamaños más pequeños, habitaban en la superficie del fondo marino y los individuos más grandes, se encontraban completamente enterrados en el fondo marino, basados en la posición del ano ya que para los primeros el ano se encontraba ubicado por debajo de la mitad de la altura total de cada individuo y para los más grandes, el ano se encontraba ubicado por encima de la mitad de la altura total de estos.
In the outcroping sequence of the Rosa Blanca Formation on the highway Zapatoca - the Platanalito Mines 188 specimens of Toxaster roulini Agassiz of the Aptiano (Camacho, 1979) were gathered directly from the strata that contained them. The respective measurements of the variable morphometrics of the collected specimens of Toxaster roulini Agassiz were carried out: long 1, long 2, width, high, high anus, distance of the mouth, with the purpose of evaluating the type of growth of these individuals and the influence of this variables in their deformation during the fossilization process. These data were processed applying lineal regressions and correlationships using the program STATISTICA version 4.0. In the sampling place the individuals that prevailed (74.4%) between 20 and 33 mm in length, between 17 and 30 mm in width, and between 11 and 18 mm in height, showing this way that this is the size common of the sampling population. The variables high anus and distance of the mouth constituted specific areas that were not modified during the growth of the individuals, which confirms from the low correlationship values that present these two variables morphometrics with the other ones. The results of the regressions and correlationships indicate that the T. roulini growth is isometric and alteration exists in the variable height very probably induced by the pressure of the superior strata during the fossilization process. We thinks about a hypothesis for the distribution in the habitat of T. roulini Agassiz in which the individuals of smaller sizes inhabited the surface of the marine bottom and the biggest individuals were totally buried in the marine bottom, based on the position of the anus for the first one the anus it is located bellow half of each individual's total height and for the biggest the anus it is located above half of the total height of these.
In the outcroping sequence of the Rosa Blanca Formation on the highway Zapatoca - the Platanalito Mines 188 specimens of Toxaster roulini Agassiz of the Aptiano (Camacho, 1979) were gathered directly from the strata that contained them. The respective measurements of the variable morphometrics of the collected specimens of Toxaster roulini Agassiz were carried out: long 1, long 2, width, high, high anus, distance of the mouth, with the purpose of evaluating the type of growth of these individuals and the influence of this variables in their deformation during the fossilization process. These data were processed applying lineal regressions and correlationships using the program STATISTICA version 4.0. In the sampling place the individuals that prevailed (74.4%) between 20 and 33 mm in length, between 17 and 30 mm in width, and between 11 and 18 mm in height, showing this way that this is the size common of the sampling population. The variables high anus and distance of the mouth constituted specific areas that were not modified during the growth of the individuals, which confirms from the low correlationship values that present these two variables morphometrics with the other ones. The results of the regressions and correlationships indicate that the T. roulini growth is isometric and alteration exists in the variable height very probably induced by the pressure of the superior strata during the fossilization process. We thinks about a hypothesis for the distribution in the habitat of T. roulini Agassiz in which the individuals of smaller sizes inhabited the surface of the marine bottom and the biggest individuals were totally buried in the marine bottom, based on the position of the anus for the first one the anus it is located bellow half of each individual's total height and for the biggest the anus it is located above half of the total height of these.
Keywords
Toxaster roulini, Fossilization, growth, Rosa Blanca Formation, Paleontology, Toxaster roulini, fosilización, crecimiento, Formación Rosa Blanca, Paleontología