ammonoid


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Related to ammonoid: ammonite, Ammonoidea

ammonoid

(ăm′ə-noid′)
n.
An extinct cephalopod mollusk of the subclass Ammonoidea of the Devonian to Cretaceous Periods, having a straight or coiled chambered shell characterized by more or less intricate suture patterns where the septa between individual chambers join the outer shell wall.
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3) Ammonoids evolved to have more complex suture patterns--and, thus, stronger shells--through time.
The mean complexity of a substructure increased in ammonoids over the first part of their history, but declined after that.
During the Devonian Period, the ammonoid cephalopods radiated and diversified and they survived repeated episodes of mass extinction followed by rapid diversification.
The high diversity of one fossil group, the ammonoids, has fueled efforts to understand the functional morphology of their phragmocones.
This is the most prolific formation in terms of ammonoid content of all the lithostratigraphic units studied (e.
The high values of redox and palaeoproductivity proxies of the studied section are very well correlated by ammonoid biostratigraphy with condensed lithofacies from outer-shelf to upper slope environments of the Internal Prebetic (Oloriz et al, 2002; 2004).
2003): Integrated ammonoid, conodont and radiolarian zonation of the Triassic and some remarks to Stage/ Substage subdivision and the numeric age of the Triassic stages.
The age of the studied stratigraphic units is controversial due mainly to the scarcity or even lack of ammonoids and other pelagic fossils commonly used for establishing the chronostratigraphic ages in Global Time Scales (see Gradstein et al.
Geochronological constraints on postextinction recovery of the ammonoids and carbon cycle perturbations during the Early Jurassic.
The first section illustrates the differences between nautilids and ammonoids in respect to shell shape, ornamentation, body chamber, phragmocone, septa, the siphuncle and buoyancy regulation, apparatus, radula and diet, arms and tentacles, eyes, development, mode of life, reproduction, dimorphism, stability, swimming, pathology and teratology, taphonomy, biostratigraphy, mass extinctions, and more.