aptychusn.
/ˈaptɪkəs/ Palaeontology.
A calcareous plate or pair of plates found in the terminal chamber of some ammonites.
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the world > animals > invertebrates > subkingdom Metazoa > grade Triploblastica or Coelomata > class Cephalopoda > [noun] > order Tetrabranchiata > family Ammonitidae > member of > calcareous plate
aptychus1877
1877 T. H. Huxley Man. Anat. Invertebrated Animals 536 The Aptychi..occupy the middle of the posterior wall or terminal chamber of the Ammonite, and have their bases towards its mouth.
1893 H. Woods Elem. Palæontol. vii. 176 In the last chamber of some Ammonites and a few other genera, a pair of calcareous or horny plates, known as the Aptychus, are occasionally found.
This entry has not yet been fully updated (first published 1972; most recently modified version published online March 2021).
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