Phylloceras (Jurásico superior, Oxfordiense)

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Phylloceras (Oxfordian medium, Jurassic upper, approximately 155 million years). Sierra de Cazorla (Jaén). Class Cephalopods, Subclass Ammonoidea, Order Ammonitida, Family Phylloceratidae The phylloceratids were involuted ammonoideos with relatively flat shells, unornamented, and only in some cases observed growth lines. The suture lines (intersection between the external shell and the septa) are especially sinuous, which has been interpreted as a reinforcement of the casing against implosion when reaching deep zones. Possibly this group of ammonoideos performed migrations related to day-night cycles in the water column like many cephalopods today. Phylloceratids can be found from platform marine rocks to oceanic environments. This specimen, which is fragmented, clearly shows the septa and sedimentary filling of the chambers. CEACTierra-UJA. Institute of Giennesian Studies. Projects 2018