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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References in periodicals archive ?
(3) Ammonoids evolved to have more complex suture patterns--and, thus, stronger shells--through time.
Fascination with "the story behind the story" led Tim to produce The Trias and its Ammonoids: The Evolution of a Time Scale (Tozer, 1984), an engrossing account of the development of Triassic biochronology in the 19th and 20th centuries, laced with fascinating character sketches of the main protagonists.
The distance between the aperture and the axis (D) measures how rapidly the coil spirals away from the center of the ammonoid. Raup (1967) used illustrations from the Treatise on Invertebrate Paleontology (Arkell et al., 1957) to obtain nonrandom samples for analysis.
The high diversity of one fossil group, the ammonoids, has fueled efforts to understand the functional morphology of their phragmocones.
The revision of this specimen for the present work indicates that the determination was probably wrong and this ammonoid is most likely an Argvethites sp.
(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.
Geologically oldest oysters were epizoans on Early Triassic ammonoids. J.
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., 2012 and references therein).
Geochronological constraints on postextinction recovery of the ammonoids and carbon cycle perturbations during the Early Jurassic.