tagma

Noun

tagma (plural tagmata)

1. A specialized, structured, grouping of functionally related segments, or analogous subunits, into units such as the head, the thorax, and the abdomen, particularly in various Arthropoda and Vertebrata.
   • This group of four neuromeres constituting the procephalic lobes is further marked off from the rest of the plate by its height, and also by its darker color as in previous stages. These distinctive characters make it convenient to apply the term "tagma" suggested by Lankester for a more or less...1910 Leland Griggs. Early Stages in the Development of the Central Nervous System of Amblystoma Punctatum. Journal of Morphology Volume 21 page 458
   • The existing Arachnida, like the higher Crustacea, are "nomomeristic", that is to say, have a fixed typical number of somites to the body. Further, they are like the higher Crustacea, "somatotagmic," that is to say, they have this limited set of somites grouped in three (or more) "tagmata" or...1911 The Encyclopaedia Britannica: A to Aus. "Arachnida" p.298
2. (dated) A specialized, structured, grouping of functionally related molecules, forming the basis the physiology and structure of larger units such as cells and tissues.
   • His view is that certain well-known properties of organized bodies require for their explanation the admission that the simplest visible structure is itself made up of an arrangement of units of a far inferior order of minuteness. It is these hypothetical units that Nägeli has called Micellae.
     Now...1889 Prof. J. S. Burdon Sanderson: Elementary Problems in Physiology. In: Annual Report of the Board of Regents of the Smithsonian Institution, 1890.
3. (historical) A military unit of battalion or regiment size, in the Byzantine empire of the 8th–11th centuries.