Talk:Ostracoderm

Untitled
Article states: "The gills of osrtacoderms were used not for feeding, but for respiration." Isn't this the normal use for gills? What am I missing? Jeffrey L. Whitledge 22:09, 2004 Oct 20 (UTC)

This is the first time "gills" were used solely for respiration. Previously they were part of the feeding apparatus. At least that is what's meant. If I'm wrong, please LMK.--DanielCD 12:12, 21 Oct 2004 (UTC)


 * That's a lot clearer now, thanks. (I just hope that it's true! :) ) Jeffrey L. Whitledge 21:06, 2004 Oct 22 (UTC)

Ostracoderm polyphyly
Ostracoderms are not a good evolutionary taxon.

"There is a number of taxa of fossil jawless vertebrates which were formerly referred to as the "ostracoderms" ("shell-skinned") because most of them possess an extensive, bony endo- and exoskeleton. The "ostracoderms" lived from the Early ordovician (about 480 million years ago) to the Late Devonian (about 370 million years ago). The relationships of the various groups of "ostracoderms" has been the subject of considerable debate since the mid-nineteenth Century, and the theory of relationship proposed here is far from definitive, yet the best supported by the currently available data. The "ostracoderms" are represented by five major groups, four of which are almost certainly clades: the Heterostraci, Osteostraci, Galeaspida, Anaspida, and Thelodonti (the monophyly of the latter being debated, Thelodonti page). In addition, there are minor groups which only include a few species: the Arandaspida, Astraspida, Eriptychiida, and Pituriaspida. The Arandaspida, Astraspida, Eriptychiida, and Heterostraci are regarded as forming a clade, the Pteraspidomorphi. Some monospecific genera, Jamoytius, Endeiolepis, and Euphanerops, formerly referred to the Anaspida, are now removed from that clade and may be more closely related to lampreys (see Hyperoartia)."

From http://tolweb.org/Vertebrata


 * Yes, it is an excellent evolutionary taxon, but it is not a phylogenetic taxon. The grpup is most certainly ancestral to the jawed vertebrates, and thus form an evolutionary grade of advanced jawless fishes. Petter Bøckman (talk) 08:47, 12 October 2011 (UTC)

Fishes
Should the first line not be 'fish' not 'fishes' ? —Preceding unsigned comment added by Pureferret (talk • contribs) 11:02, 10 May 2011 (UTC)

The illustration
The illustration are shwoing to fishes, but only the one on the top is an Ostracoderm, the other one is a jawed Placoderm.84.210.60.115 (talk) 22:20, 27 September 2011 (UTC)
 * Yes, it seems to be so. I tried to clear this question; the best prooflink that I found is this. Stas000D (talk) 14:09, 9 November 2012 (UTC)
 * (update): the best candidate is Pterichthyodes, an antiarch placoderm. Stas000D (talk) 19:32, 9 November 2012 (UTC)

Contradiction?
There seem to be two contradictory statements on whether we will find ostracoderms as a group in the classification system:

"The term does not often appear in classifications today because it is paraphyletic or polyphyletic, and has no phylogenetic meaning."

and

"The Subclass Ostracodermi has been placed in the division Agnatha along with the extant Subclass Cyclostomata, which includes lampreys and hagfishes."

I doubt that these can both be true. Felsenst (talk) 00:27, 9 May 2014 (UTC)

Early fossils?
I removed 'The first fossil fishes that were discovered were ostracoderms", referring to 1830s, as it is clearly wrong (e.g. fossil sardine-like fish were known by Xenophanes (c. 570 – c. 478 BC). But if there is there perhaps a different, correct statement that was meant? Perhaps something closer to "the earliest known fossil fish were ostracoderms"? However, that doesn't seem quite accurate either as other Agnatha seem to be earlier. If anyone knows and can provide a reference, please consider a suitable edit. SciberDoc (talk) 14:12, 23 February 2021 (UTC)