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Most heterostracans had two plates which form a large dorsal shield and a large ventral shield, and had series of scales arranged in various patterns on the sides of their bodies, the exact pattern differing from one group to another. In a few primitive forms, such as
1005:
958:
Pernegre, Vincent N., and David K. Elliott. "Phylogeny of the
Pteraspidiformes (Heterostraci), Silurian–Devonian jawless vertebrates." Zoologica Scripta 37.4 (2008): 391-403.
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are monophyletic: Protopteraspididae has recently been determined to be paraphyletic within
Pteraspidiformes, and thus, no longer valid, while
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891:"Discriminating signal from noise in the fossil record of early vertebrates reveals cryptic evolutionary history"
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The scales of heterostracans are histologically distinct from other vertebrates, having three layers composed of
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553:), is regarded as being a sister group of the Cyathaspids and Pteraspidids, while the Early Devonian
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As with many agnathan groups, heterostracans had no fins besides the tail or
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Sansom, Robert S.; Randle, Emma; Donoghue, Philip C. J. (February 7, 2015).
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and aspidine, an acellular bony tissue unique to animals of this class and
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386:(top right). Most heterostracans are pteraspidiforms, such as the
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398:(top left), which are the youngest known members of the group.
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409:, ἕτερος+ὄστρακον "those a different shell" ) is an
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57:. Unsourced material may be challenged and removed.
459:The Heterostracans differed from other Paleozoic
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565:, possibly close to the original basal forms.
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547:Tolypelepidida (the best known member being
382:Among the most primitive heterostracans are
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515:, including the two most diverse orders,
117:Learn how and when to remove this message
634:), grouped together with their relative
576:is divided into two main subgroups: the
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602:, grouped together with their relative
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511:Heterostraci are divided into several
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692:Based on the work of Mikko Haaramo.
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55:adding citations to reliable sources
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896:Proceedings of the Royal Society B
129:Extinct subclass of jawless fishes
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523:("Wing Shields"), as well as the
463:taxa both in the arrangement and
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42:needs additional citations for
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652:is divided up into five
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431:that lived primarily in
968:Haaramo, Mikko (2007).
455:Description and anatomy
909:10.1098/rspb.2014.2245
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1115:Vertebrate subclasses
1082:Paleobiology Database
559:is regarded as being
519:("Cup Shields"), and
443:existed from the mid-
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734:Traquairaspidiformes
543:. The predominantly
541:Traquairaspidiformes
499:, especially in the
369:Traquairaspidiformes
51:improve this article
903:(1800): 20142245.
756:Tolypelepidiformes
711:Tesseraspidiformes
658:Anchipteraspididae
580:of Early Devonian
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1022:Taxon identifiers
972:†Pteraspidomorphi
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467:of their scales.
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354:Lepidaspidida
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107:February 2024
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68: –
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62:Find sources:
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52:
46:
45:
40:This article
38:
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29:
28:
19:
18:Heterostracan
1110:Heterostraci
1060:Heterostraci
1030:Heterostraci
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1011:geol.lsu.edu
981:. Retrieved
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944:Heterostraci
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849:Astraspidida
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637:Nahanbiaspis
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529:Corvaspidida
525:Cardipeltida
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501:psammosteids
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441:Heterostraci
440:
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403:Heterostraci
402:
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396:psammosteids
392:doryaspidids
388:pteraspidids
384:tolypelepids
339:Corvaspidida
334:Cardipeltida
316:Heterostraci
315:
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137:Heterostraci
131:
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80:
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61:
49:Please help
44:verification
41:
1054:Wikispecies
983:30 December
864:Osteostraci
612:), and the
593:Gabreyaspis
423:Ostracoderm
1104:Categories
1001:tolweb.org
877:References
870:Lepidaspis
859:Galeaspida
854:Thelodonti
619:Cyathaspis
599:Edaphaspis
587:Amphiaspis
556:Lepidaspis
550:Athenaegis
539:, and the
497:pteraspids
495:. In some
493:caudal fin
486:Thelodonti
474:Lepidaspis
445:Ordovician
429:vertebrate
309:Subclass:
77:newspapers
688:Phylogeny
631:Anglaspis
605:Ctenaspis
465:histology
266:Kingdom:
260:Eukaryota
1045:Q2309785
1039:Wikidata
927:25520359
843:See also
654:families
625:Poraspis
545:Silurian
507:Taxonomy
461:agnathan
449:Devonian
427:jawless
414:subclass
280:Chordata
276:Phylum:
270:Animalia
256:Domain:
1074:3014431
942:(1997)
918:4298210
616:(i.e.,
584:(i.e.,
582:Siberia
482:dentine
437:estuary
411:extinct
326:Orders
296:Class:
290:Agnatha
144:–
142:Wenlock
91:scholar
1087:117963
925:
915:
668:, and
628:, and
610:Canada
596:, and
513:orders
433:marine
93:
86:
79:
72:
64:
98:JSTOR
84:books
985:2016
923:PMID
648:The
435:and
159:PreꞒ
70:news
1069:EoL
913:PMC
905:doi
901:282
608:of
416:of
53:by
1106::
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451:.
420:,
209:Pg
153:Ma
148:,
987:.
974:"
970:"
949:.
929:.
907::
732:†
425:,
405:(
313:†
300:†
214:N
204:K
199:J
194:T
189:P
184:C
179:D
174:S
169:O
164:Ꞓ
120:)
114:(
109:)
105:(
95:·
88:·
81:·
74:·
47:.
20:)
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