Definitions for osteostraci
os·teostraci

Princeton's WordNetRate this definition:0.0 / 0 votes

1. Osteostraci, suborder Osteostraci, Cephalaspida, suborder Cephalaspidanoun

   extinct group of armored fish-like vertebrates; taxonomy is not clear

WikipediaRate this definition:0.0 / 0 votes

1. Osteostraci

   The class Osteostraci (meaning "bony shells") is an extinct taxon of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian. Anatomically speaking, the osteostracans, especially the Devonian species, were among the most advanced of all known agnathans. This is due to the development of paired fins, and their complicated cranial anatomy. The osteostracans were more similar to lampreys than to jawed vertebrates in possessing two pairs of semicircular canals in the inner ear, as opposed to the three pairs found in the inner ears of jawed vertebrates. They are thought to be the sister-group to pituriaspids, and together, these two taxa of jawless vertebrates are the sister-group of gnathostomes. Several synapomorphies support this hypothesis, such as the presence of: sclerotic ossicles, paired pectoral fins, a dermal skeleton with three layers (a basal layer of isopedin, a middle layer of spongy bone, and a superficial layer of dentin), and perichondral bone.Most osteostracans had a massive cephalothorac shield, but all Middle and Late Devonian species appear to have had a reduced, thinner, and often micromeric dermal skeleton. This reduction may have occurred at least three times independently because the pattern of reduction is different in each taxon.They were probably relatively good swimmers, possessing dorsal fins, paired pectoral fins, and a strong tail. The shield of bone covering the head formed a single piece, and so presumably did not grow during adult life. However, the way in which the bone was laid down makes it possible to examine the imprints of nerves and other soft tissues. This reveals the presence of complex sensory organs and the sides and upper surface of the head, which may have been used to sense vibrations.

ChatGPTRate this definition:0.0 / 0 votes

1. osteostraci

   Osteostraci is a class of extinct, jawless, bony-armored fish that existed from the Silurian to the Devonian periods. These prehistoric marine vertebrates are notable for their heavy bony shields which covered their heads and gills. They are considered to be one of the earliest groups of fish to develop a bony skeleton.

WikidataRate this definition:0.0 / 0 votes

1. Osteostraci

   The class Osteostraci was a group of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian. Anatomically speaking, the osteostracans, especially the Devonian species, were among the most advanced of all known agnathans. This is due to the development of paired fins, and their complicated cranial anatomy. The osteostracans were more similar to lampreys than to jawed vertebrates in possessing two pairs of semicircular canals in the inner ear, as opposed to the three pairs found in the inner ears of jawed vertebrates. They are thought to be the sister-group of pituriaspids, and together, these two taxa of jawless vertebrates are the sister-group of gnathostomes. Several synapomorphies support this hypothesis, such as the presence of: sclerotic ossicles, paired pectoral fins, a dermal skeleton with three layers, and perichondral bone. Most osteostracans had a massive cephalothorac shield, but all Middle and Late Devonian species appear to have had a reduced, thinner, and often micromeric dermal skeleton. This reduction may have occurred at least three times independently because the pattern of reduction is different in each taxon.

Matched Categories

1. • Animal Order

How to pronounce osteostraci?

1. Alex

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   Mark

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   Daniel

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   Libby

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   Mia

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   Australian

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Numerology

1. Chaldean Numerology

   The numerical value of osteostraci in Chaldean Numerology is: 4

2. Pythagorean Numerology

   The numerical value of osteostraci in Pythagorean Numerology is: 9

References

1. ^ Princeton's WordNet
   http://wordnetweb.princeton.edu/perl/webwn?s=osteostraci
2. ^ Wikipedia
   https://en.wikipedia.org/wiki/Osteostraci
3. ^ ChatGPT
   https://chat.openai.com
4. ^ Wikidata
   https://www.wikidata.org/w/index.php?search=osteostraci