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Desarrollo de dientes y mandíbulas en los primeros vertebrados con mandíbula
Martin Rücklin1, Philip C J Donoghue, Zerina Johanson
1School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK. m.ruecklin@bristol.ac.uk
Nature
|October 19, 2012
Resumen
Los primeros vertebrados de mandíbula, los placodermos, poseían dientes sucesivos verdaderos, no estructuras convergentes similares a los dientes. Este hallazgo aclara los orígenes evolutivos de los dientes y las mandíbulas en los vertebrados.
Área de la Ciencia:
- Paleontología Paleontología.
- Biología del desarrollo evolutivo Biología del desarrollo evolutivo.
- Paleontología de los Vertebrados.
Sus antecedentes:
- Las mandíbulas y los dientes son innovaciones clave en la evolución de los vertebrados, centrales para la radiación adaptativa.
- El origen evolutivo de los dientes y su presencia en placódermos extintos sigue siendo objeto de debate.
- Los placodermos, un grupo hermano extinto de los condrichtios y los osteictios, poseían mandíbulas, pero sus estructuras dentales son controvertidas.
Objetivo del estudio:
- Para investigar la presencia y la naturaleza de los dientes en el extinto placodermo Compagopiscis croucheri.
- Para aclarar los orígenes evolutivos de los dientes y las mandíbulas en los primeros vertebrados con mandíbula.
- Para determinar si las estructuras dentales del placodermo representan dientes verdaderos o evolución convergente.
Principales métodos:
- Se utilizó la radiación sincrotrón en la microscopía tomográfica de rayos X (SRXTM).
- Analizó una serie de desarrollo de especímenes de Compagopiscis croucheri.
- Examinó el desarrollo, estructura y composición de la mandíbula y los dientes.
Principales resultados:
- Las mandíbulas placodérmicas comprenden distintos cartílagos, osificaciones gnatales y elementos dérmicos.
- Las osificaciones gnaciales en Compagopiscis son estructuras compuestas de dientes sucesivos.
- Estos dientes, compuestos de dentina y hueso con una cavidad pulpar, son distintos de otras estructuras de placodermo.
Conclusiones:
- Compagopiscis y otros arthrodires poseían dientes verdaderos, no estructuras convergentes similares a los dientes.
- Los dientes sucesivos evolucionaron temprano en el linaje gnathostome, poco después de los orígenes de la mandíbula.
- El desarrollo de dientes y mandíbulas en los placodermos no estaba integrado, lo que refleja distintos orígenes evolutivos.
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