Fauna petita amb closca

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El terme petita fauna dura (o petits fòssils de closca durs) s'aplica a un gran nombre de fòssils mineralitzats, en general de petites dimensions (pocs mil·límetres), distribuïts en el temps de les darreres fases de l'Ediacarià a la fi del Càmbric (548 a 500 milions d'anys enrere). La petita fauna dura (abreujada com SSF, de l'anglès "small shelly fauna" o "small shelly fossils") està molt diversificada i no hi ha una definició formal per indicar aquests tipus de fòssils.

Alguns d'aquests fòssils semblen representar tota la part esquelètica dels petits organismes com és el cas del misteriós Cloudina o alguns mol·luscs similars als llimacs. Am tot, la gran majoria dels fòssils són fragments o restes desarticulades d'organismes més grans, entre ells esponges, smol·luscs, braquiòpodes, equinoderms i animals similars als onicòfors (abans considerats artròpodes).

Els SSF són una provamolt important de l'evolució dels principals grups d'invertebrats marins en l'anomenada explosió del Càmbric.

Distribució geogràfica[modifica | modifica el codi]

Faunes riques de SSF s'han trobat a la Xina, Mongòlia, Rússia, Kazakhstan, Austràlia i Antàrtida. Lleugerament menys diversificades són les faunes d'Índia, Pakistan, Iran, Europa i Amèrica del Nord.



Bibliografia[modifica | modifica el codi]

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