The Echiura, or spoon worms, are a small group of marine animals. They are often considered to be a group of annelids, although they lack the segmented structure found in other members of that group, and so may also be treated as a separate phylum. The Echiura fossilise poorly and the earliest known specimen is from the Pennsylvanian (called the Upper Carboniferous outside North America). However, U-shaped fossil burrows that could be Echiuran have been found dating back to the Cambrian. Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms (as opposed to folk taxonomy). ... Phyla Animals are a major group of organisms, classified as the kingdom Animalia or Meta­zoa. ... Stephen, or Steven, generally pronounced IPA , is a male first name, originating from the Greek term Στέφανος (Stephanos), Latinized Stephanus. ... [[Image:http://www. ... Phyla Animals are a major group of organisms, classified as the kingdom Animalia or Meta­zoa. ... Classes and subclasses Class Polychaeta      (paraphyletic?) Class Clitellata    Oligochaeta-      (Earthworms, etc. ... Phylum (plural: phyla) is a taxon used in the classification of life, adopted from the Greek phylai the clan-based voting groups in Greek city-states. ... A fossil Ammonite Fossils (from Latin fossus, literally having been dug up) are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms. ... The Pennsylvanian is a geologic (sub)period lasting from roughly 325 million years before the present (BP) to 286 million years BP. As with most other geologic periods, the rock beds that define the period are well identified, but the exact date of the start and end are uncertain by... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... World map showing North America A satellite composite image of North America. ... The Cambrian is a major division of the geologic timescale that begins about 542 Ma (million years ago) at the end of the Proterozoic eon and ended about 488. ...

Echiurans are marine worms similar in size and habit to siphunclans. Many species, such as Echiurus, Urechis, and Ikeda, live in burrows in sand and mud; others live in rock and coral crevices. Thalassema mellita, which lives off the southeastern coast of the US, inhabits the tests (exoskeleton) of dead sand dollars. When the worm is very small, it enters the test and later becomes too large to leave. Ikeda may refer to: Ikeda, Osaka Ikeda, Hokkaido This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

The majority of echiurans live in shallow water, but there are also deep sea forms. About 140 species have been described.

External Structure

The body of an echiuran is composed of a sausage-shaped, cylindrical trunk and an anterior proboscis. They are usually a drab gray or brown color, but some such as Bonellia, are green, and others are red or rose. A few are transparent. The proboscis is large, flattened projection of the head and cannot be retracted into the trunk. In general, a proboscis (from Greek pro before and baskein to feed) is an elongated appendage from the head of an animal. ...

Reproduction & Defense

Poorly studied, with the exception of the species Bonellia viridens. Bonellia produces a vivid green pigment in its skin, known as bonellin. Planktonic Bonellia larva are very sensitive to the presence of this chemical, and develop into males that the adult female then inhales. They survive as a semi-parasitic and minute sperm-producing organism, living within a specialised chamber within her body.

In the presence of light, bonellin is a very effective biocide, killing bacteria, larva of other organisms, and red blood cells in laboratory tests. It is currently being investigated as a possible model for novel antibiotics.