110:
138:
463:
319:
421:
Agnostina and a few other trilobites also have very few thorax segments. All
Agnostina lack eyes and only have two thorax segments, characters they share with some of the later Eodiscina. Eodiscina however always have an articulating half-ring. This seals the opening in the axis between cephalon and
387:
Many characters that are divergent from other trilobites may be explained by paedomorphosis, such as the small number of thorax segments and proparian facial sutures, that occur in all trilobites during larval development, while the
Eodiscoid abatochroal eye is not unlike early development stages of
329:
The
Eodiscina are mostly considered the more primitive suborder of the Agnostida, and the Agnostina the more advanced. Some scholars do not consider the Agnostina true trilobites, and consequently rejected the idea that they were related to the Eodiscina. Consequently, these scientists have proposed
509:
suborder, and has up to several hundreds of relatively large lenses (0.05-0.5 mm), that do not touch either, but the corneal membrane extends into the sclera outside the lens, and the sclera is deeper than the lens. The most usual type of trilobite eye, called holochroal, has usually thousands
500:
If present, the eyes of
Eodiscina are unique among trilobites. They have up to 70 small lenses per eye, not touching but separated from each other by the so-called interlensar sclera. Each lens has an individual cornea, that is limited to the lens surface. The interlensar sclera is not deeper than
475:
Like all
Agnostida, members of the Eodiscina are relatively small and isopygous with the cephalon and pygidium of approximately similar size and outline. Thorax consisting of two or three fulcrate segments. Cephalon strongly parabolic in outline with maximum width (tr.) usually anterior to genal
400:
Three lineages are thought to have evolved from the monotypical family
Tsunyidiscidae. First the Calodiscidae. Second the Yukoniidae, who sprouted the Eodiscidae. And finally the Hebediscidae, that themselves gave rise to the Weymouthiidae, which contain
492:. Outline of the pygidium closely matches that of the cephalon, is usually segmented, with axis almost extending to the border, and in some species the pleural region is segmented. Examples of the protaspid growth stage are known in a few species.
422:
the anterior thorax segment that is created when the animal was enrolled. Agnostida do not have an articulating half-ring, resulting in an opening between the thorax and the cephalon when enrolled, called cephalothoracic aperture.
510:
of small hexagonal lenses without an interlensar sclera, and a common cornea. Many later
Eodiscina however, lost their visual organs altogether, and this may have resulted from living in an environment with very low visibility.
368:
rather than an eodiscoid. This is because of the dominant palpebroocular ridges, extremely long librigenae, and free pleural tips on the pygidium of variable numbers of segments. In short:
295:
period (late
Atdabanian) and became extinct at the end of the Middle Cambrian. Species are tiny to small, and have a thorax of two or three segments. Eodiscina includes six
432:) has only two thoracic segments at maturity, but has a very wide subquadrate glabella that touches the frontal border along its entire width and lacks a pygidial border.
537:
Whittington, H. B. et al. Part O, Treatise on
Invertebrate Paleontology. Revised, Volume 1 β Trilobita β Introduction, Order Agnostida, Order Redlichiida. 1997
889:
488:
is lacking or uncalcified. Facial sutures are present in early
Eodiscina, but are lost in some later representatives. When present, the facial sutures are
727:
Zhou, Z.; Webby, B.D.; Yuan, W. (1995). "Ordovician trilobites from the Yingan Formation of northwestern Tarim, Xinjiang, northwestern China".
894:
637:"Lower Cambrian (Branchian) eodiscoid trilobites from the lower Brigus formation, Avalon Peninsula, Newfoundland, Canada"
884:
137:
119:
636:
578:(2005). "5. Comparative morphology and relationships of the Agnostida". In Koenemann, S.; Jenner, R. (eds.).
786:
846:
303:
123:, 8mm in length. collected from the lower part of the Menevia Formation (Mid Cambrian Drumian Stage),
736:
671:
609:
502:
109:
879:
874:
687:
596:
Shergold, John H. (1991). "Protaspid and early meraspid growth stages of the eodiscoid trilobite
132:
851:
462:
547:
Jell, P.A. (1975). "Australian Middle Cambrian Eodiscoids with a review of the superfamily".
744:
679:
617:
296:
450:) have 3 thorax segments, but with subtriangular cephalon and pygidium, genal spines, and
331:
300:
824:
740:
675:
613:
575:
447:
410:
389:
373:
261:
868:
485:
429:
266:
67:
691:
434:
406:
348:
318:
256:
251:
833:
818:
424:
42:
325:
of the relations between the families of the Eodiscina, according to Jell, 1975
748:
683:
621:
271:
246:
87:
52:
809:
506:
489:
477:
322:
285:
198:
182:
169:
149:
92:
17:
127:
Biozone, of Dwrhyd near Nine Wells on the St David's Peninsula, SW Wales.
803:
292:
288:
82:
77:
62:
57:
47:
706:
467:
97:
72:
838:
763:
481:
159:
780:
461:
317:
476:
angle and either occulate or lacking eyes. The border is convex.
784:
505:. A second type of eye, called schizochroal, is unique to the
364:
is thought to represent an immature stage of the redlichioid
641:
Memoirs of the Association of Australasian Palaeontologists
580:
Crustacean Issues 16, Crustacea and Arthropod Relationships
384:
has been considered the most primitive of the Eodiscina.
561:
Treatise on Invertebrate Paleontology, Part O., Revised
729:
Alcheringa: An Australasian Journal of Palaeontology
658:
Naimark, E.B. (2012). "Hundred species of the Genus
602:
Alcheringa: An Australasian Journal of Palaeontology
291:. The Eodiscina first developed near the end of the
793:
600:Jell, and their implications for classification".
417:Differences with some other simplified trilobites
8:
559:W.B. Wittington; et al., eds. (1993).
781:
591:
589:
533:
531:
529:
527:
525:
523:
360:, and distinct from all other eodiscoids.
108:
28:
519:
501:the lenses. This type of eye is called
7:
890:Cambrian Series 2 first appearances
707:"Evolutionary Trends in Trilobites"
635:Westrop, S.R.; Landing, E. (2012).
392:, where lenses are also separated.
25:
471:, 3mm, from Kaili, Guizhou, China
413:, the earliest of the Agnostina.
454:with a frontal glabellar spine.
356:is extremely similar to that of
136:
405:, the probable ancestor of the
372:has probably developed through
396:Relations within the Agnostida
346:The oldest known eodiscoid is
1:
549:Palaeontographica Abteilung A
334:, which would thus be called
120:Eodiscus punctatus scanicus
911:
749:10.1080/03115519508619098
684:10.1134/S0031030112090018
622:10.1080/03115519108619010
382:Sinodiscus changyangensis
243:
238:
133:Scientific classification
131:
116:
107:
38:Lower and Middle Cambrian
31:
582:. Boca Raton: CRC Press.
330:to elevate the group to
895:Miaolingian extinctions
664:Paleontological Journal
662:Hawle et Corda, 1847".
472:
326:
847:Paleobiology Database
468:Pagetia taijiangensis
465:
321:
885:Cambrian trilobites
764:"The Trilobite Eye"
741:1995Alch...19...47Z
676:2012PalJ...46..945N
614:1991Alch...15...65S
125:Mawddachites hicksi
473:
352:. The glabella of
327:
117:Internal mould of
862:
861:
787:Taxon identifiers
338:Kobayashi, 1939.
299:classified under
279:
278:
234:
217:
16:(Redirected from
902:
855:
854:
842:
841:
829:
828:
827:
814:
813:
812:
782:
775:
774:
772:
770:
759:
753:
752:
724:
718:
717:
715:
713:
702:
696:
695:
655:
649:
648:
632:
626:
625:
598:Pagetia ocellata
593:
584:
583:
571:
565:
564:
556:
544:
538:
535:
380:. Alternatively
232:
227:
215:
210:
197:
186:
181:
141:
140:
112:
102:
39:
35:Temporal range:
29:
21:
910:
909:
905:
904:
903:
901:
900:
899:
865:
864:
863:
858:
850:
845:
837:
832:
823:
822:
817:
808:
807:
802:
789:
779:
778:
768:
766:
761:
760:
756:
726:
725:
721:
711:
709:
704:
703:
699:
670:(9): 945β1057.
657:
656:
652:
634:
633:
629:
595:
594:
587:
573:
572:
568:
558:
546:
545:
541:
536:
521:
516:
498:
460:
419:
398:
358:Dipharus clarki
344:
316:
231:
225:
216:Kobayashi, 1939
214:
208:
195:
184:
179:
135:
103:
101:
100:
95:
90:
85:
80:
75:
70:
65:
60:
55:
50:
45:
37:
36:
33:
23:
22:
15:
12:
11:
5:
908:
906:
898:
897:
892:
887:
882:
877:
867:
866:
860:
859:
857:
856:
843:
830:
815:
799:
797:
791:
790:
785:
777:
776:
754:
719:
705:S.M. Gon III.
697:
650:
627:
585:
574:Cotton, T.J.;
566:
539:
518:
517:
515:
512:
497:
494:
459:
456:
448:Raphiophoridae
418:
415:
411:Archaeagnostus
397:
394:
390:holochroal eye
374:paedomorphosis
343:
340:
315:
312:
293:Lower Cambrian
277:
276:
275:
274:
269:
264:
262:Tsunyidiscidae
259:
254:
249:
241:
240:
236:
235:
223:
219:
218:
206:
202:
201:
193:
189:
188:
177:
173:
172:
167:
163:
162:
157:
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147:
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142:
129:
128:
114:
113:
105:
104:
96:
91:
86:
81:
76:
71:
66:
61:
56:
51:
46:
41:
40:
34:
24:
14:
13:
10:
9:
6:
4:
3:
2:
907:
896:
893:
891:
888:
886:
883:
881:
878:
876:
873:
872:
870:
853:
848:
844:
840:
835:
831:
826:
820:
816:
811:
805:
801:
800:
798:
796:
792:
788:
783:
765:
762:Sam Gon III.
758:
755:
750:
746:
742:
738:
734:
730:
723:
720:
708:
701:
698:
693:
689:
685:
681:
677:
673:
669:
665:
661:
654:
651:
646:
642:
638:
631:
628:
623:
619:
615:
611:
607:
603:
599:
592:
590:
586:
581:
577:
570:
567:
562:
554:
550:
543:
540:
534:
532:
530:
528:
526:
524:
520:
513:
511:
508:
504:
495:
493:
491:
487:
486:Rostral plate
483:
479:
470:
469:
464:
457:
455:
453:
449:
445:
441:
440:Pseudampyxina
437:
436:
431:
430:Corynexochida
427:
426:
416:
414:
412:
408:
404:
395:
393:
391:
385:
383:
379:
375:
371:
367:
363:
359:
355:
351:
350:
341:
339:
337:
333:
332:ordinal level
324:
320:
313:
311:
309:
305:
302:
298:
294:
290:
287:
283:
273:
270:
268:
267:Weymouthiidae
265:
263:
260:
258:
255:
253:
250:
248:
245:
244:
242:
237:
233:Raymond, 1913
230:
224:
222:Superfamily:
221:
220:
213:
207:
204:
203:
200:
194:
191:
190:
187:
178:
175:
174:
171:
168:
165:
164:
161:
158:
155:
154:
151:
148:
145:
144:
139:
134:
130:
126:
122:
121:
115:
111:
106:
99:
94:
89:
84:
79:
74:
69:
64:
59:
54:
49:
44:
30:
27:
19:
794:
767:. Retrieved
757:
735:(1): 47β72.
732:
728:
722:
710:. Retrieved
700:
667:
663:
659:
653:
644:
640:
630:
608:(1): 65β86.
605:
601:
597:
579:
576:Fortey, R.A.
569:
560:
552:
548:
542:
503:abathochroal
499:
474:
466:
452:Taklamakania
451:
444:Nanshanaspis
443:
439:
435:Taklamakania
433:
423:
420:
402:
399:
386:
381:
377:
370:Tsunyidiscus
369:
365:
361:
357:
354:Tsunyidiscus
353:
349:Tsunyidiscus
347:
345:
335:
328:
307:
281:
280:
257:Hebediscidae
252:Calodiscidae
228:
211:
124:
118:
26:
834:iNaturalist
819:Wikispecies
769:16 November
712:14 February
458:Description
425:Thoracocare
403:Tannudiscus
308:Eodiscoidea
304:superfamily
229:Eodiscoidea
18:Eodiscoidea
869:Categories
660:Peronopsis
647:: 209β262.
514:References
407:peronopsid
378:Bulaiaspis
366:Bulaiaspis
272:Yukoniidae
247:Eodiscidae
205:Suborder:
170:Arthropoda
880:Agnostida
875:Eodiscina
825:Eodiscina
795:Eodiscina
557:cited in
507:Phacopina
490:proparian
478:Hypostome
362:D. clarki
336:Eodiscida
323:Cladogram
286:trilobite
282:Eodiscina
239:Families
212:Eodiscina
199:Agnostida
185: (?)
183:Trilobita
156:Kingdom:
150:Eukaryota
32:Eodiscina
804:Wikidata
692:85130465
314:Taxonomy
297:families
289:suborder
166:Phylum:
160:Animalia
146:Domain:
810:Q149391
737:Bibcode
672:Bibcode
610:Bibcode
555:: 1β97.
192:Order:
176:Class:
839:333891
690:
482:natant
409:genus
342:Origin
852:90401
688:S2CID
376:from
771:2012
714:2013
442:and
388:the
43:Preκ
745:doi
680:doi
618:doi
553:150
496:Eye
480:is
301:one
284:is
871::
849::
836::
821::
806::
743:.
733:19
731:.
686:.
678:.
668:46
666:.
645:42
643:.
639:.
616:.
606:15
604:.
588:^
551:.
522:^
484:.
438:,
310:.
306:,
93:Pg
773:.
751:.
747::
739::
716:.
694:.
682::
674::
624:.
620::
612::
563:.
446:(
428:(
226:β
209:β
196:β
180:β
98:N
88:K
83:J
78:T
73:P
68:C
63:D
58:S
53:O
48:κ
20:)
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