649:
simple flatworms. This lineage lacks key bilaterian features, and if it truly does reside within the bilaterian "family", many of the features listed above are no longer common to all bilateria. Instead, some features — such as segmentation and possession of a heart — are restricted to a sub-set of the bilateria, the deuterostomes and protostomes. Their last common ancestor would still have to be large and complex, but the bilaterian ancestor could be much simpler. However, some scientists stop short of including the acoelomorph clade in the bilateria. This shifts the position of the
705:
50:
787:
906:
700:
to produce segments from the growing tip at the rear of the embryo. Further, both groups make use of "the obtuse process of 'resegmentation', whereby the phase of their metameres shifts by half a unit of wavelength, i.e. somites splitting to make vertebrae or parasegments splitting to form segments."
742:
As of 2018 there is still no consensus on whether the characteristics of the deuterostomes and protostomes evolved once or many times. Features such as a heart and a blood-circulation system may therefore not have been present even in the deuterostome-protostome ancestor, which would mean that this
1188:
Gostling, Neil J.; Thomas, Ceri-Wyn; Greenwood, Jenny M.; Dong, Xiping; Bengtson, Stefan; Raff, Elizabeth C.; Raff, Rudolf A.; Degnan, Bernard M.; Stampanoni, Marco; Donoghue, Philip C. J. (June 2008). "Deciphering the fossil record of early bilaterian embryonic development in light of experimental
680:
have genes which in bilateria control the development of a layer of cells that the cnidaria do not have. This means that even if a gene can be identified as present in the urbilaterian, we cannot necessary tell what the gene's function was. Before this was realised, genetic reconstructions implied
648:
However, as biologists' understanding of the major bilaterian lineages increases, it is beginning to appear that some of these features may have evolved independently in each lineage. Further, the bilaterian clade has recently been expanded to include the acoelomorphs — a group of relatively
589:
can generate expected dates of the divergence between the bilaterian clades, and thus an assessment of when the urbilaterian lived. These dates have huge margins of error, though they are becoming more accurate with time. More recent estimates are compatible with an
Ediacaran bilaterian, although
941:
is not a polyphyletic group as would have been proposed but rather is a paraphyletic grade from which several taxa derive that may or may not conserve the ancestral clonality of basal metazoans, but instead of cloudinids having an annelid-type gut, it would instead be a U-shaped digestive tube, in
718:
The absence of a fossil record gives a starting point for the reconstruction — the urbilaterian must have been small enough not to leave any traces as it moved over or lived in the sediment surface. This means it must have been well below a centimetre in length. As all
Cambrian animals are
708:
Two hypotheses of the different characters and organ systems of the urbilaterian: the "complex" and "planula-like" urbilaterian. It is important to note that none of these representations shows an animal which existed or exists, and different combinations of these two organisms can be proposed by
644:
Proponents of a complex urbilaterian point to the shared features and genetic machinery common to all bilateria. They argue that (1) since these are similar in so many respects, they could have evolved only once; and (2) since they are common to all bilateria, they must have been present in the
734:
to do the job of transporting compounds through the body. A small, narrow gut was probably present, which would have had only one opening — a combined mouth and anus. Functional considerations suggest that the surface of the bilaterian was probably covered with
817:
Consider that the urbilaterian is an organism whose adult life is sessile sedentary with a juvenile or free and pelagic larval phase. This hypothesis is a derivative of
Nielsen's larval hypothesis, but now also considering the homology of the adult forms of
636:, the c-type and r-type, are found in all bilaterians, the urbilaterian must have possessed both types - although they may not have been found in a centralised eye, but used to synchronise the body clock to daily or lunar variations in lighting.
583:), but none of these have bilaterian affinities. This may reflect a genuine absence of bilateria, however it is likely this is the case as bilateria may not have laid their eggs in sediment, where they would be likely to fossilise.
611:
varies, but in general eyes must have directional sensitivity, and thus have screening pigments so only light from the target direction is detected. Thus defined, they need not consist of more than one photoreceptor cell.
730:
was probably dispersed, but with a small central "brain". Since acoelomorphs lack a heart, coelom or organs, the urbilaterian probably did too — it would presumably have been small enough for
518:— long after the urbilaterian would have lived. This leads to suggestions of a small urbilaterian (around 1 mm) which is the supposed state of the ancestor of protostomes, deuterostomes and
759:
The proposal that bilaterals arose from the fusion between pennatulacean-like cnidarian zooids was granted by Dewel, implies that the body plans of bilaterals originated from a colonial ancestor.
857:
The current strong bias towards a mobile urbilaterian is considered to cause problems with palaeontological and morphological data in relation to groups within and outside
Bilateria.
762:
This proposal has little or no support in the existing data, and has been commonly used as a justification against the sedentary/semi-sedentary models of urbilaterians as a whole.
625:
genes) common to eye formation in all bilaterians suggests that this machinery - and hence eyes - was present in the urbilaterian. The most likely candidate eye type is the simple
722:
Furthermore, a reconstruction of the urbilateria must rest on identifying morphological similarities between all bilateria. While some bilateria live attached to a
709:
some authors (for example, an unsegmented urbilaterian with a centralized nervous system). These two representations are only two "extremes" of different hypotheses.
2027:"Morphology and paleoecology of the late Ediacaran tubular fossil Conotubus hemiannulatus from the Gaojiashan Lagerstätte of southern Shaanxi Province, South China"
811:
807:
953:
The hypothesis of annelid-like ancestor is rejected, due to the independent evolution of segmentation and complete metamerism of several groups of bilaterians (
590:
it is possible, especially if early bilaterians were small, that the bilateria had a long cryptic history before they left any evidence in the fossil record.
2119:
Schiffbauer, James D.; Selly, Tara; Jacquet, Sarah M.; Merz, Rachel A.; Nelson, Lyle L.; Strange, Michael A.; Cai, Yaoping; Smith, Emily F. (2020-01-10).
1061:
The common ancestor of modern bilaterals would then be more similar to modern pterobranchs, although they would not be completely identical to them.
1549:
938:
878:
826:). It also considers various phylogenetic, paleontological and molecular data, relates the adult and ancestral form of anthozoans (from which
926:
1119:
930:
872:
1584:
1068:) should not change the hypothesis since it has been left aside taking only into account the molecular and morphological development of
672:
common to all bilateria, but problems arise because very similar genes can be co-opted for different functions. For instance, the gene
1732:
Schultz, Darrin T.; Haddock, Steven H. D.; Bredeson, Jessen V.; Green, Richard E.; Simakov, Oleg; Rokhsar, Daniel S. (2023-06-17).
2187:
Solène Song, Viktor
Starunov, Xavier Bailly, Christine Ruta, Pierre Kerner, Annemiek J. M. Cornelissen, Guillaume Balavoine:
1797:
Zhao, Yang; Parry, Luke A.; Vinther, Jakob; Dunn, Frances S.; Li, Yu-jing; Wei, Fan; Hou, Xian-guang; Cong, Pei-yun (2021-12-24),
909:
Potential homology between nephrozoans through a sedentary-pelagic ancestor, among which the embryonic structure similar to a
2235:
1532:
1470:
1888:
860:
So members of
Proarticulata are an evolutionary dead end rather than the ancestors of nephrozoans. It is possible that the
985:, a semi-metamerism derived from the formation of mesoderm from the gastrovascular cavity of an anthozoan-like animal.
701:
Held comments that all this makes it difficult to imagine that their urbilaterian common ancestor was not segmented.
1010:
The basal location of priapulids among ecdysozoans. Followed by the zero similarity between the priapulids with the
802:, this structure along with other characteristics could have been present in the common ancestor of the bilaterals.
446:
Its appearance is a matter of debate, for no representative has been (or may or may not ever be) identified in the
263:
1032:
The qualities of the common ancestor of mollusks as an animal with a single shell rather than a qiton-like animal.
977:
among other groups conserve, a stolon that holds the organism inside a tube secreted from the embryonic form as a
1953:
1238:
1096:
2230:
2220:
210:
2188:
2189:
Globins in the marine annelid
Platynereis dumerilii shed new light on hemoglobin evolution in bilaterians
1518:
17:
1929:
1569:"Colonial origin for Eumetazoa: major morphological transitions and the origin of bilaterian complexity"
1524:
882:) are basal (and therefore bilateral) nephrozoans, because they have considerable similarity with the
626:
1798:
1691:
781:
138:
2225:
2073:
2026:
1980:"Life history and autecology of an Ediacaran index fossil: Development and dispersal of Cloudina"
1979:
697:
2121:"Discovery of bilaterian-type through-guts in cloudinomorphs from the terminal Ediacaran Period"
1187:
2192:
2074:"Taxonomy of the late Ediacaran index fossil Cloudina and a new similar taxon from South China"
568:
has been interpreted as a bilaterian, but may simply represent a fortuitously infilled bubble.
491:
2202:
1113:
776:
726:, this appears to be a secondary adaptation, and the urbilaterian was probably mobile. Its
2132:
2085:
2038:
1991:
1941:
1930:"Borings in Cloudina Shells: Complex Predator-Prey Dynamics in the Terminal Neoproterozoic"
1832:"A non-bilaterian perspective on the development and evolution of animal digestive systems"
1745:
1627:
1616:"Life cycle evolution: was the eumetazoan ancestor a holopelagic, planktotrophic gastraea?"
1359:
653:
which is being discussed; consequently the urbilaterian in this context is farther out the
451:
420:
256:
229:
81:
1978:
Cortijo, Iván; Cai, Yaoping; Hua, Hong; Schiffbauer, James D.; Xiao, Shuhai (2015-08-01).
992:
Smooths the transition between anthozoan-like polypoids and various groups of bilaterians.
754:
8:
723:
454:
can be considered: first, the less complex ancestral form forming the common ancestor to
2136:
2089:
2042:
1995:
1945:
1774:
1749:
1733:
1631:
1363:
2161:
2120:
1864:
1831:
1658:
1615:
1446:
1421:
1385:
1323:
1290:
1266:
1254:
1214:
1108:
435:
178:
71:
41:
668:
Genetic reconstructions are unfortunately not much help. They work by considering the
2166:
2148:
2101:
2054:
2007:
1957:
1910:
1869:
1851:
1779:
1761:
1711:
1663:
1645:
1596:
1588:
1528:
1482:
1451:
1377:
1328:
1310:
1258:
1206:
1202:
1069:
654:
514:
in which they moved, and evidence of such traces first appear relatively late in the
2097:
2050:
1389:
1270:
1218:
969:); On the other hand, the urbilaterian would be an animal with a U-shaped gut, with
49:
2156:
2140:
2093:
2046:
1999:
1949:
1900:
1859:
1843:
1804:
1769:
1753:
1703:
1653:
1635:
1580:
1441:
1433:
1367:
1318:
1302:
1250:
1198:
1089:
843:
510:
ought also to have been macroscopic. However, such large animals should have left
1800:
An early
Cambrian polyp reveals an anemone-like ancestor for medusozoan cnidarians
1490:
1054:
704:
676:
has a function in eye development, but is absent in some animals with eyes; some
586:
455:
300:
249:
99:
782:
Cloudinomorpha hypothesis: (Biphasic
Sedentary sessile adult and Pelagic larvae)
770:
2191:. In: BMC Evolutionary Biology Vol. 20, Issue 165. 29 December 2020.
2144:
1889:"Following the logic behind biological interpretations of the Ediacaran biotas"
1847:
1757:
1692:"Renewed perspectives on the sedentary-pelagic last common bilaterian ancestor"
1175:
1161:
1147:
914:
727:
569:
564:
507:
336:
130:
1905:
1808:
1707:
1372:
1347:
2214:
2152:
2105:
2058:
2011:
2003:
1961:
1914:
1855:
1765:
1715:
1649:
1640:
1592:
1514:
1314:
996:
974:
966:
958:
887:
839:
799:
751:
It is possible that the common ancestor of all bilaterals looked similar to:
495:
170:
76:
66:
2072:
Cai, Yaoping; Cortijo, Iván; Schiffbauer, James D.; Hua, Hong (2017-09-01).
1568:
842:
are derived), in turn derived from an ancestral organization shared between
2170:
2025:
Cai, Yaoping; Schiffbauer, James D.; Hua, Hong; Xiao, Shuhai (2011-11-01).
1873:
1783:
1667:
1600:
1486:
1455:
1437:
1381:
1332:
1306:
1262:
1210:
1082:
1018:
1004:
1000:
970:
658:
531:
519:
511:
479:
471:
375:
185:
121:
786:
1585:
10.1002/(SICI)1097-4687(200001)243:1<35::AID-JMOR3>3.0.CO;2-#
861:
851:
795:
503:
235:
107:
1520:
How the Snake Lost its Legs. Curious Tales from the
Frontier of Evo-Devo
765:
743:
too could have been small (hence explaining the lack of fossil record).
603:
Light detection (photosensitivity) is present in organisms as simple as
416:
1124:
1026:
1011:
982:
978:
910:
823:
791:
755:
Colonial-Pennatulacean hypothesis: (Colonialy fusion of cnidarian-like)
685:
650:
551:
475:
467:
323:
224:
157:
114:
1734:"Ancient gene linkages support ctenophores as sister to other animals"
1239:"A critical reappraisal of the fossil record of the bilaterian phyla"
1036:
835:
827:
819:
731:
689:
578:
557:
540:
535:
483:
459:
424:
351:
312:
152:
1102:
1065:
1050:
1043:
962:
899:
895:
883:
866:
831:
677:
163:
146:
1022:
1014:
that at the time were pointed out as ancestors of the arthropods.
954:
947:
719:
marine, one can reasonably assume that the urbilaterian was too.
604:
499:
487:
1099: – Most recent common ancestor of all current life on Earth
530:
The first evidence of bilateria in the fossil record comes from
1422:"Acoel development supports a simple planula-like urbilaterian"
918:
847:
515:
463:
447:
431:
1481:(7/8). University of the Basque Country Press; 1999: 479–490.
1690:
Martynov, Alexander V.; Korshunova, Tatiana A. (2022-08-11).
891:
771:
Panarticulata hypothesis: (Segmentated annelid-like ancestor)
736:
693:
633:
427:
1471:"The place of phylogeny and cladistics in Evo-Devo research"
905:
2118:
1954:
10.1669/0883-1351(2003)018<0454:BICSCP>2.0.CO;2
1731:
1426:
Philosophical Transactions of the Royal Society of London B
1295:
Philosophical Transactions of the Royal Society of London B
922:
902:, this taking into account the ontogeny of the cloudinids.
814:
revives the idea of a sessile sedentary biphasic ancestor.
673:
617:
474:, sometimes referred to as the "urnephrozoan". Since most
1550:"Évolution animale : les péripéties de la phylogénie"
1419:
1085: – Possible very early animal found in ancient rocks
608:
2071:
1977:
1127: – Hypothetical last common ancestor of all animals
1049:
The derived and non-ancestral position of the annelids,
1468:
661:
than the common ancestor of deuterostomes, protostomes
545:), and the first fully accepted fossil of a bilaterian
746:
739:, which it could have used for locomotion or feeding.
593:
2024:
766:
Larval Hypothesis (Pelagic larvae and adult ancestor)
1796:
1236:
629:, which is the most widespread among the bilateria.
2203:A single gene 'invented' haemoglobin several times
1116: – Overview of and topical guide to life forms
1928:Hua, H.; Pratt, B. R.; Zhang, L.-Y. (2003-10-01).
1689:
1039:with still conserved deuterostome characteristics.
713:
2212:
2205:. On: EurekAlert! 29 December 2020. Source: CNRS
1092: – Early bilaterian organism fossil species
790:Presence of an embryonic structure similar to a
1288:
1475:International Journal of Developmental Biology
1927:
1345:
257:
1509:
1507:
1415:
1413:
1411:
1409:
1407:
1405:
1403:
1401:
1399:
1284:
1282:
1280:
1120:Timeline of the evolutionary history of life
929:and potential derivatives (yellow), and the
562:. There are earlier, controversial fossils:
502:— that are useful only in relatively large (
1181:
696:use the oscillating mechanism based on the
1462:
1232:
1230:
1228:
1035:The location of basal polychaetes such as
1017:The hastily rejected possible homology of
525:
279:Phylogenetic position of the urbilaterian
264:
250:
2160:
1904:
1863:
1829:
1773:
1657:
1639:
1504:
1445:
1396:
1371:
1322:
1277:
684:The evolutionary developmental biologist
1886:
1291:"Reconstructing the eyes of Urbilateria"
904:
785:
703:
1830:Steinmetz, Patrick R. H. (2019-09-01).
1613:
1547:
1225:
615:The presence of genetic machinery (the
14:
2213:
1289:Arendt, D.; Wittbrodt, J. (Oct 2001).
1973:
1971:
1825:
1823:
1727:
1725:
1685:
1683:
1681:
1679:
1677:
1566:
1420:Hejnol, A.; Martindale, M.Q. (2008).
1348:"Eye Evolution: the Blurry Beginning"
995:Taking into account the paraphyly of
681:an implausibly complex urbilaterian.
639:
27:Possible simple urbilateran candidate
1513:
1346:Nilsson, E.; Arendt, D. (Dec 2008).
534:in sediments towards the end of the
1105: – Individual living life form
747:Possible models of the Urbilaterian
594:Characteristics of the urbilaterian
24:
1968:
1820:
1722:
1674:
1469:Telford, M.J.; Budd, G.E. (2003).
1255:10.1111/j.1469-185X.1999.tb00046.x
572:are known from around the time of
48:
25:
2247:
2181:
1174:Further details are available at
1159:Further details are available at
1145:Further details are available at
466:) urbilaterian ancestral to both
450:. Two reconstructed urbilaterian
1203:10.1111/j.1525-142X.2008.00242.x
462:; and second, the more complex (
419:'original') is the hypothetical
2112:
2098:10.1016/j.precamres.2017.05.016
2065:
2051:10.1016/j.precamres.2011.09.002
2018:
1921:
1880:
1790:
1607:
1560:
1541:
1237:Budd, G.E.; Jensen, S. (2000).
714:Reconstructing the urbilaterian
2193:doi:10.1186/s12862-020-01714-4
1887:Runnegar, Bruce (2021-07-12).
1339:
1168:
1153:
1139:
942:fact the relationship between
13:
1:
1614:Nielsen, Claus (2013-08-16).
1567:Dewel, R. A. (January 2000).
1132:
971:deuterostomic characteristics
645:ancestral bilaterian animal.
441:
211:Cambrian substrate revolution
2236:Most recent common ancestors
1064:The location of Ctenophora (
7:
1191:Evolution & Development
1075:
988:This form of urbilaterian:
607:; the definition of a true
10:
2252:
2145:10.1038/s41467-019-13882-z
1848:10.1007/s00441-019-03075-x
1758:10.1038/s41586-023-05936-6
1525:Cambridge University Press
774:
1906:10.1017/S0016756821000443
1809:10.1101/2021.12.24.474121
1708:10.1163/18759866-bja10034
1373:10.1016/j.cub.2008.10.025
1072:, Porifera and Cnidaria.
1042:The similarities between
373:
349:
334:
327:
317:
298:
291:
2004:10.1016/j.gr.2014.05.001
1836:Cell and Tissue Research
1696:Contributions to Zoology
1641:10.1186/1471-2148-13-171
1620:BMC Evolutionary Biology
1554:Encyclopædia Universalis
1548:Michaël, Manuel (2009).
973:that hemichordates and
698:Notch signaling pathway
598:
581: million years ago
560: million years ago
543: million years ago
526:Dating the urbilaterian
1438:10.1098/rstb.2007.2239
1307:10.1098/rstb.2001.0971
937:This implies that the
934:
890:, as well as with the
803:
710:
512:traces in the sediment
482:share features — e.g.
53:
2125:Nature Communications
1573:Journal of Morphology
1114:Outline of life forms
908:
812:Tatiana A. Korshunova
808:Alexander V. Martynov
789:
777:Articulata hypothesis
707:
198:Evolutionary concepts
52:
2231:Evolutionary biology
2221:Evolution of animals
2078:Precambrian Research
2031:Precambrian Research
806:The recent model by
794:(embryonic dome) in
587:Molecular techniques
421:last common ancestor
289:Urbilaterian ↓
230:Convergent evolution
2137:2020NatCo..11..205S
2090:2017PreR..298..146C
2043:2011PreR..191...46C
1996:2015GondR..28..419C
1946:2003Palai..18..454H
1893:Geological Magazine
1750:2023Natur.618..110S
1632:2013BMCEE..13..171N
1432:(1496): 1493–1501.
1364:2008CBio...18R1096N
1358:(23): R1096–R1098.
1301:(1414): 1545–1563.
1066:Myriazoa hypothesis
632:Since two types of
506:) organisms, their
34:Part of a series on
1243:Biological Reviews
1109:Outline of biology
935:
804:
711:
640:Complex or simple?
436:bilateral symmetry
179:Small shelly fauna
54:
42:Cambrian explosion
1984:Gondwana Research
1744:(7963): 110–117.
1534:978-1-107-62139-8
1070:Choanoflagellatea
844:choanoflagellates
655:evolutionary tree
486:(and the derived
409:
408:
404:
403:
395:
394:
386:
385:
362:
361:
274:
273:
61:Fossil localities
16:(Redirected from
2243:
2175:
2174:
2164:
2116:
2110:
2109:
2069:
2063:
2062:
2022:
2016:
2015:
1975:
1966:
1965:
1940:(4–5): 454–459.
1925:
1919:
1918:
1908:
1899:(7): 1093–1117.
1884:
1878:
1877:
1867:
1827:
1818:
1817:
1816:
1815:
1794:
1788:
1787:
1777:
1729:
1720:
1719:
1702:(4–5): 285–352.
1687:
1672:
1671:
1661:
1643:
1611:
1605:
1604:
1564:
1558:
1557:
1545:
1539:
1538:
1511:
1502:
1501:
1499:
1498:
1489:. Archived from
1466:
1460:
1459:
1449:
1417:
1394:
1393:
1375:
1343:
1337:
1336:
1326:
1286:
1275:
1274:
1234:
1223:
1222:
1185:
1179:
1172:
1166:
1157:
1151:
1143:
1090:Ikaria wariootia
1053:and perhaps the
1003:and potentially
688:notes that both
582:
561:
544:
536:Ediacaran period
330:
329:
320:
319:
294:
293:
286:
285:
276:
275:
266:
259:
252:
30:
29:
21:
2251:
2250:
2246:
2245:
2244:
2242:
2241:
2240:
2211:
2210:
2184:
2179:
2178:
2117:
2113:
2070:
2066:
2023:
2019:
1976:
1969:
1926:
1922:
1885:
1881:
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1546:
1542:
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1463:
1418:
1397:
1352:Current Biology
1344:
1340:
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1226:
1186:
1182:
1173:
1169:
1158:
1154:
1144:
1140:
1135:
1130:
1078:
1055:xenacoelomorphs
894:of semi-mobile
784:
779:
773:
768:
757:
749:
716:
642:
627:pigment-cup eye
601:
596:
577:
556:
539:
528:
508:common ancestor
456:Xenacoelomorpha
444:
405:
396:
387:
363:
301:Xenacoelomorpha
270:
241:
240:
199:
191:
190:
100:Ediacaran biota
95:
87:
86:
62:
28:
23:
22:
15:
12:
11:
5:
2249:
2239:
2238:
2233:
2228:
2226:Ediacaran life
2223:
2209:
2208:
2207:
2206:
2197:
2196:
2183:
2182:External links
2180:
2177:
2176:
2111:
2064:
2017:
1990:(1): 419–424.
1967:
1920:
1879:
1842:(3): 321–339.
1819:
1789:
1721:
1673:
1606:
1559:
1540:
1533:
1527:. p. 11.
1515:Held, Lewis I.
1503:
1461:
1395:
1338:
1276:
1249:(2): 253–295.
1224:
1197:(3): 339–349.
1180:
1176:Fossil embryos
1167:
1162:Vernanimalcula
1152:
1148:Ediacara biota
1137:
1136:
1134:
1131:
1129:
1128:
1122:
1117:
1111:
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1040:
1033:
1030:
1015:
1008:
993:
967:proarticulates
939:Cloudinomorpha
915:digestive tube
913:(violet), the
879:Multiconotubus
838:, and perhaps
783:
780:
772:
769:
767:
764:
756:
753:
748:
745:
728:nervous system
715:
712:
665:acoelomorphs.
651:cladistic node
641:
638:
600:
597:
595:
592:
574:Vernanimalcula
570:Fossil embryos
565:Vernanimalcula
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131:Vernanimalcula
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84:
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45:
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37:
36:
26:
9:
6:
4:
3:
2:
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2222:
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2186:
2185:
2172:
2168:
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2158:
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2079:
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2056:
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2036:
2032:
2028:
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2013:
2009:
2005:
2001:
1997:
1993:
1989:
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1981:
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1972:
1963:
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1951:
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1902:
1898:
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1837:
1833:
1826:
1824:
1810:
1806:
1802:
1801:
1793:
1785:
1781:
1776:
1771:
1767:
1763:
1759:
1755:
1751:
1747:
1743:
1739:
1735:
1728:
1726:
1717:
1713:
1709:
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1555:
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1521:
1516:
1510:
1508:
1493:on 2011-07-16
1492:
1488:
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1465:
1457:
1453:
1448:
1443:
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1208:
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1200:
1196:
1192:
1184:
1177:
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1164:
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1149:
1142:
1138:
1126:
1123:
1121:
1118:
1115:
1112:
1110:
1107:
1104:
1101:
1098:
1095:
1093:
1091:
1087:
1084:
1081:
1080:
1073:
1071:
1067:
1062:
1056:
1052:
1048:
1046:and mollusks.
1045:
1041:
1038:
1034:
1031:
1028:
1024:
1020:
1019:ambulacrarian
1016:
1013:
1009:
1006:
1005:Deuterostomia
1002:
998:
997:Cycloneuralia
994:
991:
990:
989:
986:
984:
980:
976:
975:lophophorates
972:
968:
964:
960:
959:panarthropods
956:
951:
949:
945:
940:
932:
928:
924:
920:
916:
912:
907:
903:
901:
897:
893:
889:
886:of sedentary
885:
881:
880:
875:
874:
869:
868:
863:
858:
855:
853:
852:parahoxozoans
849:
845:
841:
840:proarticulate
837:
833:
829:
825:
821:
815:
813:
809:
801:
800:Pterobranchia
797:
793:
788:
778:
763:
760:
752:
744:
740:
738:
733:
729:
725:
720:
706:
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687:
682:
679:
675:
671:
666:
664:
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656:
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628:
624:
620:
619:
613:
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606:
591:
588:
584:
580:
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571:
567:
566:
559:
554:
553:
548:
542:
537:
533:
532:trace fossils
523:
521:
517:
516:fossil record
513:
509:
505:
501:
497:
496:blood vessels
493:
489:
485:
481:
480:deuterostomes
477:
473:
472:deuterostomes
469:
465:
461:
457:
453:
449:
448:fossil record
439:
437:
433:
429:
426:
422:
418:
415:(from German
414:
400:
399:
391:
390:
382:
381:
378:
377:
376:Deuterostomes
371:
370:
367:
366:
358:
357:
354:
353:
347:
346:
343:
342:
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338:
332:
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321:
314:
311:
310:
307:
306:
303:
302:
296:
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288:
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283:
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278:
277:
267:
262:
260:
255:
253:
248:
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228:
226:
223:
222:
219:
216:
215:
212:
209:
208:
205:
202:
201:
195:
194:
187:
186:Helcionellids
184:
183:
180:
177:
176:
173:
172:
171:Odontogriphus
168:
166:
165:
161:
159:
156:
154:
151:
149:
148:
144:
143:
140:
137:
136:
133:
132:
128:
124:
123:
119:
118:
117:
116:
112:
110:
109:
105:
104:
101:
98:
97:
94:Key organisms
91:
90:
83:
80:
78:
77:Sirius Passet
75:
73:
70:
68:
67:Burgess Shale
65:
64:
58:
57:
51:
47:
46:
43:
39:
38:
35:
32:
31:
19:
2128:
2124:
2114:
2081:
2077:
2067:
2037:(1): 46–57.
2034:
2030:
2020:
1987:
1983:
1937:
1933:
1923:
1896:
1892:
1882:
1839:
1835:
1812:, retrieved
1799:
1792:
1741:
1737:
1699:
1695:
1623:
1619:
1609:
1579:(1): 35–74.
1576:
1572:
1562:
1556:(in French).
1553:
1543:
1519:
1495:. Retrieved
1491:the original
1478:
1474:
1464:
1429:
1425:
1355:
1351:
1341:
1298:
1294:
1246:
1242:
1194:
1190:
1189:taphonomy".
1183:
1170:
1160:
1155:
1146:
1141:
1088:
1083:Caveasphaera
1063:
1060:
1012:cephalozoans
1001:Lophophorata
987:
952:
943:
936:
925:(blue), the
888:pterobranchs
877:
871:
865:
859:
856:
816:
805:
761:
758:
750:
741:
721:
717:
683:
669:
667:
662:
657:and is more
647:
643:
631:
622:
616:
614:
602:
585:
573:
563:
555:, dating to
550:
546:
529:
520:acoelomorphs
492:through guts
452:morphologies
445:
430:, i.e., all
413:urbilaterian
412:
410:
374:
350:
335:
299:
236:crown groups
169:
162:
145:
139:Burgess-type
129:
122:Kimberichnus
120:
113:
106:
33:
2195:. See also:
2084:: 146–156.
1027:brachiozoan
950:is denied.
927:head shield
917:(red), the
898:and mobile
836:nephrozoans
820:choanozoans
796:Cloudinidae
504:macroscopic
476:protostomes
468:protostomes
324:Protostomes
108:Dickinsonia
18:Urbilateria
2215:Categories
2131:(1): 205.
1814:2024-08-31
1626:(1): 171.
1497:2011-07-16
1133:References
1125:Urmetazoan
1029:tentacles.
983:protoconch
931:oral lobes
911:protoconch
862:Cloudinids
832:placozoans
824:Ctenophora
792:protoconch
775:See also:
690:centipedes
686:Lewis Held
552:Kimberella
498:and nerve
442:Appearance
425:bilaterian
225:Cladistics
158:Halwaxiids
153:Radiodonts
115:Kimberella
82:Doushantuo
72:Chengjiang
2153:2041-1723
2106:0301-9268
2059:0301-9268
2012:1342-937X
1962:0883-1351
1915:0016-7568
1856:1432-0878
1766:1476-4687
1716:1875-9866
1650:1471-2148
1593:0362-2525
1315:0962-8436
1051:flatworms
1037:Oweniidae
963:chordates
884:tubariums
873:Conotubus
828:jellyfish
732:diffusion
724:substrate
484:nephridia
464:coelomate
460:Nephrozoa
434:having a
352:Ecdysozoa
313:Nephrozoa
234:Stem and
2171:31924764
1874:31388768
1784:37198475
1775:10232365
1668:23957497
1601:10629096
1517:(2014).
1487:14756323
1456:18192185
1390:11554469
1382:19081043
1333:11604122
1271:39772232
1263:10881389
1219:13233666
1211:18460095
1103:Organism
1076:See also
1044:hyoliths
1023:bryozoan
955:annelids
948:annelids
944:Cloudina
933:(green).
900:mollusks
896:hyoliths
867:Cloudina
822:(except
678:cnidaria
605:seaweeds
547:organism
315: ↓
164:Opabinia
147:Marrella
2162:6954273
2133:Bibcode
2086:Bibcode
2039:Bibcode
1992:Bibcode
1942:Bibcode
1934:PALAIOS
1865:6733828
1746:Bibcode
1659:3751718
1628:Bibcode
1447:2614228
1360:Bibcode
1324:1088535
848:sponges
659:derived
538:(about
500:ganglia
488:kidneys
432:animals
423:of the
2169:
2159:
2151:
2104:
2057:
2010:
1960:
1913:
1872:
1862:
1854:
1782:
1772:
1764:
1738:Nature
1714:
1666:
1656:
1648:
1599:
1591:
1531:
1485:
1454:
1444:
1388:
1380:
1331:
1321:
1313:
1269:
1261:
1217:
1209:
919:stolon
892:shells
694:snakes
217:Themes
203:Trends
1386:S2CID
1267:S2CID
1215:S2CID
737:cilia
670:genes
634:opsin
428:clade
2167:PMID
2149:ISSN
2102:ISSN
2055:ISSN
2008:ISSN
1958:ISSN
1911:ISSN
1870:PMID
1852:ISSN
1780:PMID
1762:ISSN
1712:ISSN
1664:PMID
1646:ISSN
1597:PMID
1589:ISSN
1529:ISBN
1483:PMID
1452:PMID
1378:PMID
1329:PMID
1311:ISSN
1259:PMID
1207:PMID
1097:LUCA
1025:and
979:dome
965:and
946:and
923:tail
921:and
876:and
850:and
810:and
798:and
692:and
674:Pax6
621:and
618:Pax6
599:Eyes
478:and
470:and
458:and
411:The
40:The
2157:PMC
2141:doi
2094:doi
2082:298
2047:doi
2035:191
2000:doi
1950:doi
1901:doi
1897:159
1860:PMC
1844:doi
1840:377
1805:doi
1770:PMC
1754:doi
1742:618
1704:doi
1654:PMC
1636:doi
1581:doi
1577:243
1442:PMC
1434:doi
1430:363
1368:doi
1319:PMC
1303:doi
1299:356
1251:doi
1199:doi
981:or
663:and
623:Six
609:eye
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558:555
549:is
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417:ur-
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2155:.
2147:.
2139:.
2129:11
2127:.
2123:.
2100:.
2092:.
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2045:.
2033:.
2029:.
2006:.
1998:.
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1986:.
1982:.
1970:^
1956:.
1948:.
1938:18
1936:.
1932:.
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
