Inicio > Evolución, Paleontología, Zoología > Nectocaris pteryx: el cefalópodo del cámbrico que vagó entre artrópodos y cordados

Nectocaris pteryx: el cefalópodo del cámbrico que vagó entre artrópodos y cordados

Cuando, a mediados de los 70, Simon Conway Morris comenzó a desempolvar el baúl de los recuerdos donde se encontraban los fósiles hallados por Charles Walcott a comienzos del s. XX en un lugar conocido como Burgess Shale, se topó con un espécimen insólito del cual Walcott no había dejado nota alguna a pesar de su buena preservación. El ejemplar en cuestión recibió el nombre de Nectocaris pteryx y Conway Morris lo describió1 dejando entrever que presentaba características similares a los artrópodos, sobre todo en su parte anterior. Sin embargo, el resto del cuerpo no revelaba indicio alguno de rasgos artropodianos, sino más bien de las formas basales de nuestro propio filo: los cordados. Si saber muy bien dónde colocar esta forma quimérica dentro del árbol evolutivo de los animales, Conway Morris concluyó lo siguiente:

«La imposibilidad de resolver definitivamente las afinidades de este organismo no deben ser motivo de sorpresa. La investigación actual está demostrando que varias especies de Burgess Shale no pueden acomodarse en ningún phylum actual.»1,2

Nectocaris parecía ser otro miembro más de los nuevos phyla que iban surgiendo de la reinterpretación de los fósiles de Burgess Shale.

Representación de Nectocaris pteryx siguiendo la interpretación inicial de Conway Morris.

Representación de Nectocaris pteryx siguiendo la interpretación inicial de Conway Morris.

Pues bien, hace menos de 24 horas salía publicado en Nature un artículo3 en el cual, tras el estudio de más de 90 nuevos especímenes de Nectocaris, se ha concluido que  posiblemente se trate del cefalópodo más antiguo conocido hasta la fecha. Los fósiles apuntan a que Nectocaris presentaba sólo un par de tentáculos largos y prensiles, así como un vistoso sifón que le permitiría la propulsión. En contra, no presentaba concha, lo que evidenciaría que la adquisición de ésta se desarrolló en cefalópodos con posterioridad al hiponome o sifón. En cualquier caso, este descubrimiento no sólo nos ayuda a comprender un poco más el origen de los cefalópodos, sino también a resolver un enigma más de la extraña fauna de Burgess Shale, así como reforzar la idea de que la explosión cámbrica posiblemente no fue tan dispar como en un primer momento se pensó.

A la izquierda, uno de los nuevos fósiles de Nectocaris hallados en Burgess Shale. A la derecha, reconstrucción siguiendo la reciente interpretación.

A la izquierda, uno de los nuevos fósiles de Nectocaris hallados en Burgess Shale. A la derecha, reconstrucción siguiendo la reciente interpretación.

1 Conway Morris, S. (1976), «Nectocaris pteryx, a new organism from the Middle Cambrian Burgess Shale of British Columbia», Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, 12: 703–713.

2 Gould, S. J. 1989. Wonderful life: the Burgess Shale and the nature of hitory. New York, W. W. Norton & Company. An ingsightful discussion of what fossils tell us about the nature of life’s evolutionary history.

3 Smith, Martin R and Caron, Jean-Bernard (2010). «Primitive soft-bodied cephalopods from the Cambrian». Nature, 465: 427–428.

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