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Jason D Pardo1, Matt Szostakiwskyj2, Per E Ahlberg3

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La evolución temprana de los tetrápodos fue más diversa de lo que se pensaba anteriormente. Un nuevo análisis del aïstopod Lethiscus stocki revela características primitivas, que desafían la comprensión actual de la diversidad y las relaciones de los tetrápodos del tallo.

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Área de la Ciencia:

  • Paleontología
  • Biología evolutiva
  • Anatomía comparada

Sus antecedentes:

  • Los análisis filogenéticos de la evolución temprana de los tetrápodos sugieren un grupo troncal homogéneo con adaptación terrestre gradual.
  • El grupo de coronas tetrápodas exhibe una importante diversidad morfológica.
  • Los aistópodos, como el Lethiscus stocki, se consideraban anteriormente miembros altamente especializados del grupo de la corona.

Objetivo del estudio:

  • Reevaluar la posición filogenética y la morfología craneal de los primeros tetrápodos, específicamente el aïstopod Lethiscus stocki.
  • Desafiar el consenso existente sobre la evolución temprana de los tetrápodos y la diversidad de los grupos madre.
  • Investigar las implicaciones de los nuevos datos morfológicos para los análisis filogenéticos y las calibraciones del reloj molecular.

Principales métodos:

  • Tomografía microcomputada (micro-TC) de la muestra de Lethiscus stocki.
  • La disección digital para revelar la morfología craneal y cerebral.
  • Análisis filogenético que incorpora nuevos datos morfológicos de los aistopodos.

Principales resultados:

  • Lethiscus stocki exhibe características craneales extremadamente primitivas, incluida una muesca espiral y un remanente de notocorda.
  • Los aisópodos se colocan profundamente dentro del grupo del tallo tetrápodo, no en el grupo de la corona.
  • Las relaciones filogenéticas previamente aceptadas son desafiadas, con un linaje lepospondilo potencialmente dentro de los amniotas.
  • El grupo de tetrápodos muestra una mayor diversidad de plan corporal de lo que se suponía anteriormente.

Conclusiones:

  • La diversidad de los tetrápodos del grupo madre fue subestimada.
  • Los aisópodos representan un linaje basal dentro del grupo de tetrápodos.
  • Los marcos filogenéticos actuales y las fechas de calibración para la evolución temprana de los tetrápodos requieren revisión.
  • El muestreo de caracteres es crucial para resolver las relaciones evolutivas tempranas de los tetrápodos.