The Antiarchi ("Opposite anus") were the 2nd most successful order of placoderms known, after the Arthrodira. The order`s name was coined by Edward Drinker Cope, who, when examining some fossils that he thought were armored tunicates related to Chelysoma, mistakenly thought that the eye-hole was the mouth, and that the opening for the anal siph...
Found on http://en.wikipedia.org/wiki/Antiarchi
Antiarchs (the Antiarchi) were a type of (mosty) small placoderms that were abundant during mid- to late-Devonian. These armored fish ranged from 8-12 inches (20-30 cm) long. Instead of the pectoral fins that other fish have, these unusual tetrapods had segmented 'arms' that were covered by hard dermal bone, but these arms lacked an internal skelet
Found on http://www.enchantedlearning.com/subjects/dinosaurs/glossary/
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