Hemichordata

=**Phylum Hemichordata (means "half cord") **= Hemichordata is a small, unusual phylum of worm-like creatures closely related to the phylums Chordata and Echinodermata. They vary widely in size, from the 8 ft (2.5 m) lengths of the acorn worms to the 1/25 in (1 mm) lengths of the pterobranchs. The two living classes also vary in appearance and habits. Acorn worms are large individuals that burrow through sediment like an earthworm, digesting any organic material in the soil, or feeding on suspended particles in the water. Pterobranchs, on the other hand, form large colonies in which each individual is connected to another by stems. These creatures create their own homes, a series of tubes composed of collagen secreted by glands on their bodies.

Hemichordates do have several features that, despite the other differences, link the classes together. First off, all hemichordates have a 3-fold division of the body, with the preoral lobe, the collar, and the trunk. All hemichordates have pharyngeal slits, or gill slits, that open into the pharynx. Acorn worms have up to 200 of these; pterobranchs have only 1.

An interesting feature in the hemichordates is the stomochord located in the collar. This stomochord closely resembles the notochord of the chordates. Another feature that resembles that of chordates are the presence of the two nerve chords, a dorsal nerve chord and a smaller ventral nerve chord. Due to these similarities to the phylum Chordata, Hemichordata was once placed in this phylum, but DNA studies have shown that hemichordates are closer to the echinoderms than the chordates, and so they were placed in their own phylum. There are three recognized classes, one of which is extinct. //**Enteropneusta-**// acorn worms //**Graptolithina-**// graptolites (extinct) //**Pterobranchia-**// pterobranchs 20 species
 * Classes of Hemichordata:**

**Student ZooKeeper Pages of Species: (Enter Your Species Pages Below)**
Balanoglossus clavigerus (Zookeeper: Sidney Baker) Acorn Worm; Balanoglossus carnosus (Zookeeper: Taylor Cebuly) Hawaiian Acorn Worm (Zookeeper: Shaiann Etwara) Acorn Worm (Zookeeper: Erin Holbert) Saccogolossus Apatensis (Zookeeper:Syed Islam) //Cephalodiscus agglutinans(//Zookeeper: Marissa Jenkins//)// //﻿﻿////Cephalodiscus nigrescens// (Zookeeper: Hannah Jones) Rhabdopleura normani(Zookeeper: James K. Kanthachack) Balanoglossus gigas! (Zookeeper: Tori Lopez) Saccoglossus kowalevskii (Zookeeper: Heath McGregor) //Yunnanozoon lividum// (Zookeeper: Ramon Prieto) Deep Sea Acorn Worm (Zookeeper: Lindsey Rafus) Stink Worm ( Zookeeper: Sarah Reimer) Acorn Worm (//Harrimania planktophilus//) (Zookeeper: Paco Rodriguez) Tongue Worm (Zookeeper: Paige Ryder) __Cephalodiscus densus__ (Zookeeper: Jeffrey Slape) Balanoglossus gigas (Zookeeper: Riley Stewart) Acorn Worm- Balanoglossus Apertus (Zookeeper: Jessica Tolliver) //Cephalodiscus gracilis// (Zookeeper Rachel Tolliver) balanoglossus aurantiacus (zookeeper: Ashley Veilleux) Acorn Worm; Saccoglossus Bromophenolosus King (Zookeeper: Hannah WIlliams) Stereobalanus Canadensis (Zookeeper: Johnta Williams) Hawaiian acorn worms (Zookeeper: Katie Woolen)

http://www.angelfire.com/mo2/animals1/phylum/hemichord.html jumpinjacksmonroe.com biog1105-1106.org
 * Information and Photo References:**