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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
994:
947:
Pernegre, Vincent N., and David K. Elliott. "Phylogeny of the
Pteraspidiformes (Heterostraci), Silurian–Devonian jawless vertebrates." Zoologica Scripta 37.4 (2008): 391-403.
466:, the dorsal and ventral shields are composed of a mosaic of tiny scales. In most other known forms, though, these tiny scales have fused together to form the shield-plates.
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669:," as the sister taxon of the most basal family, Anchipteraspidae. Pteraspididae, Gigantaspididae and Protaspididae, in turn form the suborder
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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Pteraspidiformes, and thus, no longer valid, while
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492:, the ends of the branchial plates (the plates that covered the gills) is drawn out to form wing-like extensions.
880:"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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542:), 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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375:(top right). Most heterostracans are pteraspidiforms, such as the
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387:(top left), which are the youngest known members of the group.
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673:, with various genera of Protopteraspididae as sister taxa.
398:, ἕτερος+ὄστρακον "those a different shell" ) is an
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46:. Unsourced material may be challenged and removed.
448:The Heterostracans differed from other Paleozoic
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554:, possibly close to the original basal forms.
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536:Tolypelepidida (the best known member being
371:Among the most primitive heterostracans are
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504:, including the two most diverse orders,
106:Learn how and when to remove this message
623:), grouped together with their relative
565:is divided into two main subgroups: the
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591:, grouped together with their relative
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500:Heterostraci are divided into several
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681:Based on the work of Mikko Haaramo.
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44:adding citations to reliable sources
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885:Proceedings of the Royal Society B
118:Extinct subclass of jawless fishes
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512:("Wing Shields"), as well as the
452:taxa both in the arrangement and
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31:needs additional citations for
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383:(bottom left) and the huge
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436:to the conclusion of the
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232:Scientific classification
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420:that lived primarily in
957:Haaramo, Mikko (2007).
444:Description and anatomy
898:10.1098/rspb.2014.2245
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1104:Vertebrate subclasses
1071:Paleobiology Database
548:is regarded as being
508:("Cup Shields"), and
432:existed from the mid-
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723:Traquairaspidiformes
532:. The predominantly
530:Traquairaspidiformes
488:, especially in the
358:Traquairaspidiformes
40:improve this article
892:(1800): 20142245.
745:Tolypelepidiformes
700:Tesseraspidiformes
647:Anchipteraspididae
569:of Early Devonian
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1011:Taxon identifiers
961:†Pteraspidomorphi
929:Janvier, Philippe
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767:Cyathaspidiformes
645:, four of which,
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558:Cyathaspidiformes
506:Cyathaspidiformes
456:of their scales.
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379:(bottom right),
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343:Lepidaspidida
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96:February 2024
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57: –
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51:Find sources:
45:
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35:
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29:This article
27:
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1099:Heterostraci
1049:Heterostraci
1019:Heterostraci
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1000:geol.lsu.edu
970:. Retrieved
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838:Astraspidida
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626:Nahanbiaspis
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518:Corvaspidida
514:Cardipeltida
499:
490:psammosteids
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430:Heterostraci
429:
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392:Heterostraci
391:
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385:psammosteids
381:doryaspidids
377:pteraspidids
373:tolypelepids
328:Corvaspidida
323:Cardipeltida
305:Heterostraci
304:
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126:Heterostraci
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83:
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69:
62:
50:
38:Please help
33:verification
30:
1043:Wikispecies
972:30 December
853:Osteostraci
601:), and the
582:Gabreyaspis
412:Ostracoderm
1093:Categories
990:tolweb.org
866:References
859:Lepidaspis
848:Galeaspida
843:Thelodonti
608:Cyathaspis
588:Edaphaspis
576:Amphiaspis
545:Lepidaspis
539:Athenaegis
528:, and the
486:pteraspids
484:. In some
482:caudal fin
475:Thelodonti
463:Lepidaspis
434:Ordovician
418:vertebrate
298:Subclass:
66:newspapers
677:Phylogeny
620:Anglaspis
594:Ctenaspis
454:histology
255:Kingdom:
249:Eukaryota
1034:Q2309785
1028:Wikidata
916:25520359
832:See also
643:families
614:Poraspis
534:Silurian
496:Taxonomy
450:agnathan
438:Devonian
416:jawless
403:subclass
269:Chordata
265:Phylum:
259:Animalia
245:Domain:
1063:3014431
931:(1997)
907:4298210
605:(i.e.,
573:(i.e.,
571:Siberia
471:dentine
426:estuary
400:extinct
315:Orders
285:Class:
279:Agnatha
133:–
131:Wenlock
80:scholar
1076:117963
914:
904:
657:, and
617:, and
599:Canada
585:, and
502:orders
422:marine
82:
75:
68:
61:
53:
87:JSTOR
73:books
974:2016
912:PMID
637:The
424:and
148:PreꞒ
59:news
1058:EoL
902:PMC
894:doi
890:282
597:of
405:of
42:by
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198:Pg
142:Ma
137:,
976:.
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959:"
938:.
918:.
896::
721:†
414:,
394:(
302:†
289:†
203:N
193:K
188:J
183:T
178:P
173:C
168:D
163:S
158:O
153:Ꞓ
109:)
103:(
98:)
94:(
84:·
77:·
70:·
63:·
36:.
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