trituberculy

English

Noun

trituberculy (uncountable)

(zoology, obsolete) A theory of the development of mammalian molar teeth.

Usage notes

The primitive stage is that of simple cones, as in reptiles. The simple cone then developed a smaller cone in front and another behind, and then a cingulum, and the three cones became arranged in a triangle (the trigon or trigonid; this stage is called the tritubercular or trigonodont), the two smaller cusps having moved to the outer side in upper and to the inner in lower molars. The trigon being a cutting apparatus, an extension of the posterior part of the crown was developed in lower molars for crushing, and a smaller corresponding part appeared in upper molars. Another large cone then arose, usually from the cingulum. In more complex forms, smaller intermediate cusps appeared.

Part or all of this entry has been imported from the 1913 edition of Webster’s Dictionary, which is now free of copyright and hence in the public domain. The imported definitions may be significantly out of date, and any more recent senses may be completely missing.
(See the entry for trituberculy in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913.)

单词	trituberculy
释义	trituberculy English Noun trituberculy (uncountable) (zoology, obsolete) A theory of the development of mammalian molar teeth. Usage notes The primitive stage is that of simple cones, as in reptiles. The simple cone then developed a smaller cone in front and another behind, and then a cingulum, and the three cones became arranged in a triangle (the trigon or trigonid; this stage is called the tritubercular or trigonodont), the two smaller cusps having moved to the outer side in upper and to the inner in lower molars. The trigon being a cutting apparatus, an extension of the posterior part of the crown was developed in lower molars for crushing, and a smaller corresponding part appeared in upper molars. Another large cone then arose, usually from the cingulum. In more complex forms, smaller intermediate cusps appeared. Part or all of this entry has been imported from the 1913 edition of Webster’s Dictionary, which is now free of copyright and hence in the public domain. The imported definitions may be significantly out of date, and any more recent senses may be completely missing. (See the entry for trituberculy in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913.)
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