Spreite, meaning leaf-blade in German (or spreiten, the plural form in

German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ger ...

) is a stacked, curved, layered structure that is characteristic of certain

trace fossils A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...

. They are formed by invertebrate organisms tunneling back and forth through sediment in search of food. The organism moves perpendicularly just enough at the start of each back-and-forth pass so that it avoids reworking a previously tunneled area, thereby ensuring that it only makes feeding passes through fresh, unworked sediment. Two types of spreiten are generally recognized. Protrusive spreiten result from movement of the organism away from its

burrow An Eastern chipmunk at the entrance of its burrow A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of sh ...

entrance (i.e., a downward movement in vertical burrows), whereas retrusive spreiten result from movement towards the burrow entrance (i.e., an upward movement in vertical burrows). Vertical burrows with retrusive spreiten are also referred to as "escape burrows", as they represent attempts by the organism during periods of high sedimentation to prevent the burrow entrance from being buried, and at the same time keep the bottom of the burrow at the same distance from the sediment-water interface. In essence, the organism "escapes" from being buried too deeply by progressively tunneling upward, thereby leaving behind it a stacked vertical succession of concave-side-up spreite. ''

Diplocraterion ''Diplocraterion'' is an ichnogenus describing vertical U-shaped burrows having a spreite (weblike construction) between the two limbs of the U. The spreite of an individual ''Diplocraterion'' trace can be either protrusive (between the paired ...

'' is the classic example of a vertical burrow with spreite, whereas '' Rhizocorallium'' is an example of a horizontal burrow with spreite. Spreiten differ from menisci, which are flat to slightly curved, back-filling structures found in some tubular burrows. Menisci are formed when the organism packs sediment, and sometimes fecal material as well, behind itself as it moves through the burrow. Because spreiten and menisci represent different behaviors, the distinction between spreiten and meniscate burrows is an important criterion for the identification of certain

ichnotaxa An ichnotaxon (plural ichnotaxa) is "a taxon based on the fossilized work of an organism", i.e. the non-human equivalent of an artifact. ''Ichnotaxa'' comes from the Greek ίχνος, ''ichnos'' meaning ''track'' and ταξις, ''taxis'' meaning ...

. For example, generally parallel-sided, elongate, horizontal burrows with menisci are typically assigned to the ''

Muensteria ''Muensteria'' is the ichnogenus of a type of trace fossil that is found in sedimentary rocks, and is thought to represent the horizontal burrow of a marine invertebrate organism. It is a horizontal, non-branching, unlined, tube-like burrow char ...

ichnospecies An ichnotaxon (plural ichnotaxa) is "a taxon based on the fossilized work of an organism", i.e. the non-human equivalent of an artifact. ''Ichnotaxa'' comes from the Greek ίχνος, ''ichnos'' meaning ''track'' and ταξις, ''taxis'' meaning ...

, whereas similar burrows with spreite will generally be assigned to the '' Rhizocorallium'' ichnogenus.

References

{{Commons category, Trace fossils Burrow fossils Invertebrate paleozoology

See also

References