- Suture (anatomical)
In
anatomy , a suture is a fairly rigid joint between two or more hard elements of an animal, without significant overlap. Sutures are found in a wide range of animals, from theCambrian period to the present day. Hence they are formed by several methods and between hard parts made of various materials.Vertebrate skeletons
These are made of
bone , in which the main rigid ingredient iscalcium phosphate .Cranial sutures
The crania (brain cases) of most
vertebrates consist of sets of bony plates held together bycranial sutures . These sutures are held together mainly bySharpey's fibers which grow from each bone into the adjoining one.utures in ankles of land vertebrates
[
crurotarsal ankle. Theastragalus (pink) is fixed to thetibia (green) by a suture. Adapted with permission from [http://www.palaeos.com/Vertebrates/Units/270Archosauromorpha/270.500.html Palaeos] ] In the type ofcrurotarsal ankle which is found incrocodilians and some otherarchosaurs , theastragalus is fixed to thetibia by a suture and the joint bends around a peg on the astragalus which fits into a socket in thecalcaneum . [ [http://www.palaeos.com/Vertebrates/Units/270Archosauromorpha/270.500.html Archosauromorpha: Archosauria - Palaeos] ]utures in the shells of
cephalopods In
cephalopod mollusks which have external shells (e.g. "Nautilus ",ammonites ), the shell is divided into compartments by septa ("partitions"). The septa are joined to the external shell by sutures formed by "repeated invagination" (they interlock like pieces of ajigsaw puzzle ). The sutures are visible from the outside and often form complex and elaborate patterns. [ [http://www.palaeos.com/Invertebrates/Molluscs/Cyrtosoma/Cephalopoda/Cephalopoda.Glossary.html#suture Cephalopoda Glossary - Palaeos] ] The shells of mollusks are mainly made ofcalcium carbonate (which is also the main constituent oflimestone andchalk ).Gastropodsanchor|Gastropod
Nearly all snails consist, in effect, of a tube of increasing diameter, closed at the small end, and spirally wrapped around a central axis.
Each complete rotation of this spirally-arranged tube is called a whorl. The whorls of a snail shell usually overlap one another forming a spire. Where the whorls overlap, there is usually a clear indentation. This indentation forms a visible line which reaches from the apex to the
body whorl ; this line is the suture.Details of the suture are often useful in discriminating one species from another. The suture also provides a sort of geographic marker from which one can refer to the positioning of patterning or sculpture where that is relevant: for example some species have a darker or lighter subsutural band on the shell.
utures in the carapaces of trilobites
Many
trilobites had sutures which divided the cephalon (head section) into 3 pieces. The sutures in trilobites' cephalons were unusual because it seems their main function was to create "weaknesses" which made it easy for this part of thecarapace ("armor") to split when the animal needed to molt. A trilobite's carapace consisted ofcalcite andcalcium phosphate deposited on a lattice (framework) ofchitin (a complex sugar). [ cite book | author=Fortey, R.A. | title=Trilobite! | publisher=Knopf | date=2000]References
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