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Un cráneo condríctico simmoriiforme y el origen de los peces quimeroides
Michael I Coates1, Robert W Gess2, John A Finarelli3,4
1Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois 60637-1508, USA.
Nature
|January 5, 2017
Resumen
La caja cerebral fósil de Dwykaselachus revela rasgos quimeroides tempranos en un tiburón simórico. Este hallazgo reconfigura la comprensión de la evolución de los vertebrados con mandíbula y los orígenes de los condrichtios después de la extinción del Devónico.
Área de la Ciencia:
- Paleontología
- Biología evolutiva
- Anatomía comparada
Sus antecedentes:
- Los peces quimeroides (Holocefalia) son un grupo clave de vertebrados con mandíbula con una anatomía única.
- La evidencia fósil de la evolución temprana de los quimeroides es limitada debido a las primeras especializaciones en fósiles conocidos.
- Los quimeroides ofrecen información sobre las condiciones ancestrales de los condrichtios y los gnathostomes.
Objetivo del estudio:
- Para analizar el cerebro del enigmático chondrichthyan Dwykaselachus usando tomografía computarizada.
- Investigar el origen evolutivo y las primeras especializaciones de los peces quimeroides.
- Para aclarar la filogenia de los primeros gnathostomes y las respuestas condrichthyan a la extinción devoniana.
Principales métodos:
- Análisis de tomografía computarizada (TC) de la caja cerebral de Dwykaselachus.
- Análisis morfológico comparativo de las características internas y externas.
- Análisis filogenético que incorpora nuevos datos.
Principales resultados:
- La caja cerebral de Dwykaselachus, de sedimentos sudafricanos de ~ 280 millones de años de antigüedad, es externamente semejante a un tiburón simórico e internamente semejante a una quimeroide.
- La morfología interna muestra especializaciones quimeroides características, incluido el laberinto ótico y las configuraciones del espacio cerebral.
- El espécimen es el ejemplo más completo y sin triturar de su tipo, proporcionando detalles sin precedentes.
Conclusiones:
- Dwykaselachus exhibe un mosaico de características simmorídicas y quimeroides, lo que sugiere una base morfofuncional temprana para el cráneo quimeroide derivado.
- Estos hallazgos proporcionan una estructura robusta para la filogenia temprana de gnathostome y los orígenes de chondrichthyan modernos.
- El estudio arroja luz sobre la adaptación y supervivencia de los condrichtianos después del evento de extinción de finales del Devónico.
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