396:
species were large and smooth-walled; by the mid-Ordovician a large and expanding variety of ornament, and of hollow appendages, was evident. While shorter appendages are generally solid, larger protrusions tend to be hollow, with some of the largest displaying a spongy internal structure. However, even hollow appendages leave no mark on the inner wall of the organisms: this may suggest that they were secreted or attached from the outside. There is some debate about the number of layers present in the organisms' walls: up to three layers have been reported, with the internal wall often ornamented; some specimens only appear to display one such wall layer. The multitude of walls may indeed reflect the construction of the organism, but could be a result of the
799:
pattern is also observed in modern-day tropical zooplankton. The diversity of living habits is also reflected by the depth of water and distance from the shore. Different species are found in highest abundance at different depths. While deeper waters around 40 km from the shoreline are generally the optimal environment, some species appear to prefer very shallow water. On the whole, chitinozoans are less abundant in turbulent waters or reef environments, implying an aversion to such regimes when alive, if it is not an effect of sedimentary focusing. Chitinozoans also become rarer in shallower waterâalthough the reverse is not necessarily true. They cannot survive freshwater input.
617:
fossils has been seized by both sides of the argument. Proponents suggest that the use of the same chemical framework is an indicator that the two may be related. However, this factor means that situations favouring the preservation of one will also tend to preserve the otherâand the preparation techniques used to extract the fossils will also favour or disfavour the two groups equally. Therefore, the apparent co-occurrence of the two fossils may merely be an artifact of their similar composition. The hypothesis struggles to explain the continuing abundance of chitinozoans after the middle
Devonian, when graptolites became increasingly rare.
547:
600:
129:
626:
832:, making correlation easier; better still, they can often be recognised in even quite strongly metamorphosed rocks. However, convergence of morphological form to similar environments sometimes leads to the mistaken identification of a species in several areas separated by vast differences in space and time, but sharing a similar depositional environment; clearly, this can cause major problems if the organisms are interpreted as being the same species. Aside from the
778:
496:
408:
642:, and it is not impossible that the chitinozoans are a convergent phenomenon laid by both groups. In fact, the spirally coiled nature of chitinozoan chains has been used to suggest that they were laid by a spirally coiled organism, such as the gastropods; were this inference true, uncoiled chains could be attributed to the (straight) annelid worms or other organisms.
575:
organisms more closely together. This was made possible as scientific advances permitted the identification of distinctive traits in organisms across
Eisenack's groups. Features of the base and neck, the presence of spines, and perforations or connections are now considered the most useful diagnostic features.
769:
The ornament of the chitinozoans may cast light on the question. Whilst in some cases a defensive roleâby making the vessel larger, and thus less digestible by would-be predatorsâseems probable, it is not impossible that the protrusions may have anchored the organisms to the sea floor. However, their
570:
in the 1970s allowed the improved detection of surface ornamentation which is hugely important in identificationâas can be appreciated by a comparison of the images on this page. Even the light microscope image here is of far greater quality than could have been achieved earlier in the century, using
827:
periods. Their utility is due to the rapidity of their morphological evolution, their abundanceâthe most productive samples bearing almost a thousand tests per gramâand the easy identification (due largely to the large variation in shapes) and short lifetimes (<10 million years) of most
320:
Chitinozoan ecology is also open to speculation; some may have floated in the water column, where others may have attached themselves to other organisms. Most species were particular about their living conditions, and tend to be most common in specific paleoenvironments. Their abundance also varied
395:
External ornamentation is often preserved on the surface of the fossils, in the form of hairs, loops or protrusions, which are sometimes as large as the chamber itself. The range and complexity of ornament increased with time, against a backdrop of decreasing organism size. The earliest
Ordovician
798:
with daily growth markings have been found in association with abundant chitinozoans, which allow the detection of seasonal variation in chitinozoan abundance. A peak in abundance during the late autumn months is observed, with the maxima for different species occurring on different dates. Such a
633:
The test of the
Chitinozoa was fixedâthere was no scope for any parts of it to move or rotate. This makes it seem likely that the tests were containers, to protect whatever was insideâwhether that was a "hibernating" or encysted organism, or a clutch of hatching eggs. There are several arguments
616:
stages of graptolitesâthe period between the colony's sexual reproduction, and the formation of a new colony. This hypothesis appears to be supported by the co-occurrence of graptolite and chitinozoan fossils, whose abundances appear to mirror one another. The similar chemical composition of the
574:
The original three families proposed by
Eisenack represented the best classification possible with available data, based largely on the presence or absence of chains of organisms and the chamber's shape. The orders were subsequently revised to conform better to Linnean taxonomy, placing related
774:(i.e. increasing the relative importance of water's viscosity)âit is therefore possible that at least the long-spined chitinozoans were planktonic "floaters". On the other hand, the walls of some chitinozoans were probably too thick and dense to allow them to float.
785:
Whilst little is known about their interactions with other organisms, small holes in the tests of some chitinozoans are evidence that they were hosts to some parasites. Although some forms have been reinterpreted as "pock-marks" caused by the disintegration of the
565:
grounds. Further genera were identified, at first on an annual basis, as time progressed. Since its publication in 1931, Eisenack's original classification has been much honed by these additional discoveries, as well as advances in microscopy. The advent of the
713:. However, as mentioned previously, spines and appendages are attached from the exterior of the vessel: only animals have the cellular machinery necessary to perform such a feat. Further, no analogy for the cocoon envelope can be found in this kingdom.
705:
members of this group. However, the chemistry of these tests differs from that of the fossils, and modern
Testacea are almost exclusively fresh-waterâan extremely different environment. Within a year, he had abandoned this initial idea.
611:
are colonial organic walled fossils which also occurred from the
Ordovician to the Devonian; only part of their life cycle is known and it is not clear how they reproduced. It has been suggested that the Chitinozoa may represent the
304:
affinities have all been entertained. The organisms have been better understood as improvements in microscopy facilitated the study of their fine structure, and it has been suggested that they represent either the
765:
An infaunal mode of life can be quickly ruled out, as the fossils are sometimes found in alignment with the depositing current; as nothing attached them to the bottom, they must have fallen from the water column.
1537:
Winchester-seeto, T.; Foster, C.; O'Leary, T. (2000). "The environmental response of Middle
Ordovician large organic walled microfossils from the Goldwyer and Nita Formations, Canning Basin, Western Australia".
1674:
657:, have yielded chitinozoans alongside a wide range of other organisms. It has been suggested that if whatever organism created the Chitinozoa was fossilisable, it would be present in the Soom
515:(unlikely), or that the fossilisable parts of the organism only formed after the developmental process was complete. However in 2019 a study found that morphological variation of specimens of
770:
low-density construction makes this unlikely: perhaps more plausible is that they acted to attach to other organisms. Longer spines also make the organisms more buoyant, by decreasing their
1071:
Gabbott, S.E.; Aldridge, R.J.; Theron, J.N. (1998). "Chitinozoan chains and cocoons from the Upper
Ordovician Soom Shale lagerstatte, South Africa; implications for affinity".
739:
It is not immediately clear what mode of life was occupied by these improbably shaped fossils, and an answer only becomes apparent after following several lines of reasoning.
794:, the clustering of cylindrical holes around the chamberâwhere the flesh of the organism was likely to be concentratedâis evidence for a biological cause. Corals in
742:
The fossils' restriction to marine sediments can be taken as sound evidence that the organisms dwelt in the PalĂŠozoic seasâwhich presents three main modes of life:
1681:
376:
of the chitinozoan lies at the opposite end from the aperture. The base may involve various ornamentation derived from the internal layer. The edge of the base (
869:, more than 20 million years before the group is found elsewhere in the Ordovician. Chitinozoans appear to have become extinct at the end of the Devonian; rare
709:
Arguments put forwards by Obut (1973) proposed that the organisms were one-celled "plants" similar to the dinoflagellates, which would now be grouped into the
1117:
Liang, Yan; Hints, Olle; Tang, Peng; Cai, Chenyang; Goldman, Daniel; NÔlvak, Jaak; Tihelka, Erik; Pang, Ke; Bernardo, Joseph; Wang, Wenhui (2020-12-01).
661:âfrom which gastropods and graptolites are notable in their absence. Most organisms present in the shale can be ruled out for a variety of reasons, but
866:
238:
218:
407:
579:
232:
212:
1992:
583:
226:
1346:
727:
In 2020, exceptionally preserved remains of chitinozoans were described, showing the remains of smaller tests within larger ones, suggesting
2050:
524:
Many chitinozoans are found as isolated fossils, but chains of multiple tests, joined from aperture to base, have been reported for all
511:"Immature" or juvenile examples of chitinozoans have not been found; this may suggest that either they did not "grow", that they were
1413:
Reid, P. C. and A. W. G. John: A possible relationship between chitinozoa and tintinnids. Rev. Paleobot. Palynol. 34, 251-262 (1981).
550:
Scanning electron microscope images, such as that in the taxobox, are far more illuminating than those taken in transmitted light.
678:
remain as likely candidates. However, further evidence connecting chitinozoans to any of these groups is circumstantial at best.
1667:
353:), though a circular plug prevents direct contact between the central cavity and its surroundings. This plug may be called an
997:
836:, chitinozoans were the only reliable means of correlating palĂŠozoic units until the late 1960s, when the detailed study of
1290:"Morphological variation suggests that chitinozoans may be fossils of individual microorganisms rather than metazoan eggs"
2035:
2055:
807:
Since Alfred
Eisenack first recognised and named the group in 1930, the Chitinozoa have proven incredibly useful as a
2040:
1521:
1264:
953:
388:. In chitinozoans which attach to substrates or each other in large chains, the center of the base is augmented with
333:. They appear dark to almost opaque when viewed under an optical microscope. Their anatomy is based around the broad
1021:
1288:
Liang, Yan; Bernardo, Joseph; Goldman, Daniel; NÔlvak, Jaak; Tang, Peng; Wang, Wenhui; Hints, Olle (2019-08-14).
503:
532:(spring-shaped) forms. Occasionally, clusters or condensed chains are found, packed in an organic "cocoon".
567:
136:
1605:
Shen, Cen; Aldridge, Richard J.; Williams, Mark; Vandenbroucke, Thijs R.A.; Zhang, Xi-guang (2013-02-01).
541:
17:
289:
1022:"Middle and upper Devonian chitinozoan biostratigraphy of the paranĂĄ basin in Brazil and Paraguay"
281:
across the globe. This wide distribution, and their rapid pace of evolution, makes them valuable
2010:
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2005:
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1979:
1960:
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1432:
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338:
8:
2045:
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1622:
1551:
1436:
1134:
1084:
911:
1580:
1448:
1374:
1322:
1289:
1196:
1096:
1041:
1003:
896:"A chitinozoan morphological lineage and its importance in Lower Silurian stratigraphy"
292:
and ecological reconstruction difficult. Since their discovery in 1931, suggestions of
152:
1559:
1181:
Proceedings of the Annual Meeting. American Association of Stratigraphic Palynologists
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1317:
1301:
1252:
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1138:
1088:
1033:
983:
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862:
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includes those with an operculum over the aperture and no distinct neck. The order
558:
282:
254:
109:
1487:
Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre, Bulletin
1485:
Martin, F. (197). "Palynofacies et microfacies du Silurien inférieur a Deerlijk".
1037:
613:
858:
812:
771:
686:
599:
554:
278:
195:
1256:
988:
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1945:
314:
313:. However, recent research has alternatively suggested that they represent the
258:
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1313:
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895:
746:
128:
1971:
1567:
1331:
1305:
848:
808:
654:
517:
758:
752:
625:
1954:
1119:"Fossilized reproductive modes reveal a protistan affinity of Chitinozoa"
495:
310:
262:
48:
702:
586:
includes those with a clearly discernable neck and an internal prosome.
1822:
1795:
1732:
1607:"Earliest chitinozoans discovered in the Cambrian Duyun fauna of China"
1444:
1378:
1200:
1070:
841:
816:
787:
777:
721:
675:
662:
646:
608:
330:
266:
93:
58:
1020:
Grahn, Yngve; Pereira, Egberto; Bergamaschi, Sergio (24 August 2010).
755:â dwelling upon the sea floor, perhaps anchored in placeâthe "sitters"
658:
384:. Alternatively, it could send out large spines or branches, known as
277:), the millimetre-scale organisms are abundant in almost all types of
1804:
1714:
1630:
1143:
1118:
833:
828:
species. They are also widely distributed and appear in a variety of
710:
667:
639:
397:
274:
163:
113:
98:
42:
1916:
1192:
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1786:
1777:
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1723:
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717:
698:
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671:
349:-like substance. The chamber narrows towards the main opening (the
270:
140:
117:
88:
83:
68:
63:
53:
1581:
Sutherland, S.J.E.; Palaeontographical Society Monographs (1994).
1423:
Eisenack, A. (1931). "Neue Mikrofossilien des baltischen Silurs".
506:
Morphological terms relating to chitinozoans, after Jenkins (1970)
1813:
1768:
1604:
1466:
Eisenack, A. (1968). "Uber Chitinozoen des baltischen Gebietes".
874:
795:
635:
557:'s original description of the chitinozoans placed them in three
293:
103:
78:
1984:
829:
791:
690:
346:
301:
982:, Springer Geology, New Delhi: Springer India, pp. 1â25,
1656:
Commission Internationale de Microflore du Paléozoique (CIMP)
529:
525:
512:
297:
253:(singular: chitinozoan, plural: chitinozoans) are a group of
943:
1655:
1583:
Ludlow Chitinozoans from the Type Area and Adjacent Regions
1395:
Kozlowski, R. (1963). "Sur la nature des chitinozoaires".
1287:
571:
poorly preserved specimens and less advanced microscopes.
978:
Jain, Sreepat (2020), Jain, Sreepat (ed.), "Chitinozoa",
877:
remains may represent reworked fossils or fungal spores.
1243:
Laufeld, S. (1974). "Silurian Chitinozoa from Gotland".
980:
Fundamentals of Invertebrate Palaeontology: Microfossils
701:, since similar chitin-based tests were produced by the
265:
produced by an as yet unknown organism. Common from the
1294:
Proceedings of the Royal Society B: Biological Sciences
1019:
724:
have been suggested to be affiliated to chitinozoans.
1658:, international commission for Palaeozoic palynology.
944:
Jansonius, J.; Jenkins, W.A.M. (1978). "Chitinozoa".
1530:
578:Chitinozoans are placed into two orders. The order
1505:
761:â free-floating in the water columnâthe "drifters"
329:Chitinozoa range in length from around 50 to 2000
317:of a group of protists with uncertain affinities.
1365:Tappan, H. (1966). "Chitinozoan Classification".
1116:
2027:
1390:
1388:
893:
1178:
939:
937:
935:
933:
931:
844:fully unleashed their stratigraphic potential.
689:'s original guess was that the Chitinozoa were
634:behind an association of the chitinozoans with
361:(if it lies deep within the narrowed region or
1574:
1238:
1236:
1234:
1232:
1230:
629:Chitinozoa might represent gastropod egg sacs.
603:Chitinozoa may have been immature graptolites.
1675:
1585:. Palaeontographical Society. pp. 1â124.
1394:
1385:
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357:(if it lies at the tip of the aperture) or a
1503:
1465:
1459:
1422:
1416:
928:
802:
749:â living within the sedimentâthe "burrowers"
380:) may extend into a sharp radial plate, the
1497:
1242:
847:The oldest known chitinozoans appear to be
369:, often has a distinctive form or texture.
1682:
1668:
1478:
1364:
1353:
1350:, is no longer recognised as a chitinozoan
1207:
1159:
1059:
851:remains tentatively referred to the genus
494:
127:
1508:Plankton & productivity in the oceans
1484:
1321:
1142:
987:
919:
392:which project down to assist attachment.
365:). The rim of the aperture, known as the
948:. Elsevier, New York. pp. 341â357.
946:Introduction to marine micropaleontology
776:
716:The cyst forms of a particular group of
624:
598:
545:
14:
2028:
1179:Jenkins, W.A.M. (1970). "Chitinozoa".
887:
485:
465:
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450:
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1921:
1920:
1540:Review of Palaeobotany and Palynology
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430:
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969:
967:
965:
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521:likely represented a growth series.
470:
418:
413:
24:
2051:Early Ordovician first appearances
1595:After "their chitinoid appearance"
1512:. Oxford: Pergamon Press. p.
781:Silurian fossil coral from Gotland
561:, spanning seven genera, based on
25:
2067:
1649:
1107:
1073:Journal of the Geological Society
962:
535:
406:
46:
1598:
1589:
1407:
1338:
1251:. Universitetsforlaget: 1â130.
857:. They were recovered from the
147:, showing its flask-like shape
1468:Palaeontographica, Abteilung A
1281:
528:. Very long chains twist into
13:
1:
1560:10.1016/S0034-6667(00)00060-9
1397:Acta Palaeontologica Polonica
1038:10.1080/01916122.2002.9989570
880:
589:
830:marine depositional settings
568:scanning electron microscope
288:Their bizarre form has made
137:Scanning electron micrograph
27:Group of marine microfossils
7:
1257:10.18261/8200093581-1974-01
989:10.1007/978-81-322-3962-8_1
681:
345:encased by two layers of a
10:
2072:
2036:Prehistoric marine animals
734:
649:, an Ordovician konservat-
645:Recent excavations of the
542:List of chitinozoan genera
539:
324:
2056:Pennsylvanian extinctions
1929:
1829:
894:Gary Lee Mullins (2000).
803:Stratigraphic application
208:
203:
153:Scientific classification
151:
135:
126:
34:
2041:Enigmatic eukaryote taxa
1093:10.1144/gsjgs.155.3.0447
1367:Journal of Paleontology
921:10.1111/1475-4983.00131
620:
309:or juvenile stage of a
1306:10.1098/rspb.2019.1270
782:
630:
604:
551:
398:preservational process
273:periods (i.e. the mid-
2006:Paleobiology Database
1910:Millions of years ago
1504:Raymont, JEG (1972).
809:stratigraphic markers
780:
628:
602:
549:
143:chitinozoan from the
1493:(10): 11â12 (of 26).
729:asexual reproduction
339:radially symmetrical
1623:2013Geo....41..191S
1552:2000RPaPa.113..197W
1437:1930NW.....18..880E
1425:Naturwissenschaften
1135:2020Geo....48.1200L
1085:1998JGSoc.155..447G
912:2000Palgy..43..359M
693:, specifically the
341:region involving a
1445:10.1007/BF01488901
1300:(1908): 20191270.
1245:Fossils and Strata
783:
631:
605:
552:
321:with the seasons.
2021:
2020:
1923:Taxon identifiers
1703:
1129:(12): 1200â1204.
999:978-81-322-3962-8
595:Young graptolites
390:apical structures
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16:(Redirected from
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1373:(6): 1394â1396.
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867:Gaotai Formation
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239:Lagenochitinidae
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38:Temporal range:
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1431:(42): 880â881.
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859:Middle Cambrian
813:biostratigraphy
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772:Rayleigh number
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687:Alfred Eisenack
684:
623:
597:
592:
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1955:Wikispecies
1347:Mirachitina
842:graptolites
815:during the
676:cephalopods
609:graptolites
467:Aboral pole
331:micrometres
35:Chitinozoan
2046:Palynology
2030:Categories
1961:Chitinozoa
1931:Chitinozoa
1823:Quaternary
1796:Cretaceous
1733:Ordovician
1051:8 November
1026:Palynology
881:References
834:acritarchs
817:Ordovician
788:diagenetic
722:tintinnids
663:polychaete
647:Soom Shale
640:gastropods
614:pre-sicula
590:Affinities
540:See also:
472:Transverse
442:â Shoulder
367:collarette
267:Ordovician
251:Chitinozoa
204:Subgroups
190:Chitinozoa
139:of a late
18:Chitinozoa
1805:Paleogene
1715:Ediacaran
1639:0091-7613
1474:: 137â98.
1403:: 425â45.
1314:0962-8452
1275:0300-9491
1153:0091-7613
1101:129236534
1046:128673881
1008:241650725
838:conodonts
711:Alveolata
672:conodonts
668:Promissum
481:ORAL TUBE
415:Oral pole
386:processes
355:operculum
285:markers.
275:Paleozoic
257:-shaped,
164:Eukaryota
114:Famennian
1969:BioLib:
1946:Q2468682
1940:Wikidata
1787:Jurassic
1778:Triassic
1751:Devonian
1742:Silurian
1724:Cambrian
1568:11164220
1453:23050887
1332:31362642
1187:: 1â21.
825:Devonian
821:Silurian
790:mineral
747:Infaunal
718:ciliates
699:Testacea
695:rhizopod
682:Protists
636:annelids
559:families
447:â Flanks
427:Aperture
351:aperture
271:Devonian
196:Eisenack
171:Phylum:
159:Domain:
141:Silurian
118:Devonian
1985:2912515
1972:1174512
1814:Neogene
1769:Permian
1619:Bibcode
1611:Geology
1548:Bibcode
1433:Bibcode
1379:1301963
1323:6710598
1201:3687298
1131:Bibcode
1123:Geology
1081:Bibcode
908:Bibcode
875:Permian
863:Stage 5
796:Gotland
759:Pelagic
753:Benthic
735:Ecology
691:amoebae
665:worms,
530:helical
488:CHAMBER
452:â Basal
359:prosome
335:chamber
325:Anatomy
294:protist
259:organic
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231:Family
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185:Class:
2011:379902
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526:genera
513:moults
462:â Base
457:Margin
437:â Neck
382:carina
347:chitin
302:fungal
300:, and
225:Order
211:Order
1993:IRMNG
1449:S2CID
1375:JSTOR
1197:JSTOR
1097:S2CID
1042:S2CID
1004:S2CID
659:biota
298:plant
255:flask
1998:1153
1893:â100
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1635:ISSN
1564:PMID
1518:ISBN
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1261:ISBN
1149:ISSN
1053:2022
994:ISBN
950:ISBN
873:and
840:and
823:and
621:Eggs
607:The
475:axis
422:axis
374:base
372:The
363:neck
337:, a
315:test
307:eggs
198:1931
49:Preê
1980:EoL
1899:â50
1627:doi
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