Chitinozoan

Chitinozoan; Temporal range: 510–358 Ma PreꞒ Ꞓ O S D C P T J K Pg N Cambrian Stage 5 - Famennian (latest Devonian);
	Scanning electron micrograph of a late Silurian chitinozoan from the Burgsvik beds, showing its flask-like shape
Scientific classification
Domain:	Eukaryota
Phylum:	incertae sedis
Class:	Chitinozoa; Eisenack 1931
Subgroups
	Order Operculatifera Family Desmochitinidae ; ; Order Prosomatifera Family Conochitinidae ; Family Lagenochitinidae ; ;

Last updated September 03, 2024

Chitinozoa (singular: chitinozoan, plural: chitinozoans) are a group of flask-shaped, organic walled marine microfossils produced by an as yet unknown organism.^[1] Common from the Ordovician to Devonian periods (i.e. the mid-Paleozoic), the millimetre-scale organisms are abundant in almost all types of marine sediment across the globe.^[2] This wide distribution, and their rapid pace of evolution, makes them valuable biostratigraphic markers.^[3]^[4]

Their bizarre form has made classification and ecological reconstruction difficult. Since their discovery in 1931, suggestions of protist, plant, and fungal 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 eggs or juvenile stage of a marine animal.^[5] However, recent research has alternatively suggested that they represent the test of a group of protists with uncertain affinities.^[6]

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 with the seasons.

Anatomy

Chitinozoa range in length from around 50 to 2000 micrometres.^[2] They appear dark to almost opaque when viewed under an optical microscope. Their anatomy is based around the broad chamber, a radially symmetrical region involving a central cavity encased by two layers of a chitin-like substance. The chamber narrows towards the main opening (the aperture), though a circular plug prevents direct contact between the central cavity and its surroundings. This plug may be called an operculum (if it lies at the tip of the aperture) or a prosome (if it lies deep within the narrowed region or neck). The rim of the aperture, known as the collarette, often has a distinctive form or texture.^[3]

The base 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 (basal margin) may extend into a sharp radial plate, the carina. Alternatively, it could send out large spines or branches, known as processes. In chitinozoans which attach to substrates or each other in large chains, the center of the base is augmented with apical structures which project down to assist attachment.^[3]

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 species were large and smooth-walled;^[7] 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.^[8] 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.^[8] 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 preservational process.^[8]

Oral pole

Longitudinal
axis

Aperture

← Collarette

← Neck

← Shoulder

← Flanks

← Basal
0Margin

← Base

Aboral pole

Transverse

axis

ORAL TUBE

CHAMBER

Morphological terms relating to chitinozoans, after Jenkins (1970)

"Immature" or juvenile examples of chitinozoans have not been found; this may suggest that either they did not "grow", that they were moults (unlikely), or that the fossilisable parts of the organism only formed after the developmental process was complete.^[7] However in 2019 a study found that morphological variation of specimens of Desmochitina likely represented a growth series.^[9]

Many chitinozoans are found as isolated fossils, but chains of multiple tests, joined from aperture to base, have been reported for all genera.^[7] Very long chains twist into helical (spring-shaped) forms. Occasionally, clusters or condensed chains are found, packed in an organic "cocoon".

Classification

Alfred Eisenack's original description of the chitinozoans placed them in three families, spanning seven genera,^[10] based on morphological grounds. Further genera were identified, at first on an annual basis, as time progressed.^[11] 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 scanning electron microscope in the 1970s allowed the improved detection of surface ornamentation which is hugely important in identification—as 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 poorly preserved specimens and less advanced microscopes.^[11]

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 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.^[7]^[11]

Chitinozoans are placed into two orders. The order Operculatifera includes those with an operculum over the aperture and no distinct neck. The order Prosomatifera includes those with a clearly discernable neck and an internal prosome.^[3]

Affinities

Young graptolites

The graptolites 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 pre-sicula stages of graptolites—the period between the colony's sexual reproduction, and the formation of a new colony.^[7] 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 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 other—and 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.^[7]^[8] The hypothesis struggles to explain the continuing abundance of chitinozoans after the middle Devonian, when graptolites became increasingly rare.^[8]

Eggs

The test of the Chitinozoa was fixed—there 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 inside—whether that was a "hibernating" or encysted organism, or a clutch of hatching eggs.^[8] There are several arguments behind an association of the chitinozoans with annelids or gastropods,^[12] 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.^[8]

Recent excavations of the Soom Shale, an Ordovician konservat-lagerstätten in South Africa, 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 biota—from which gastropods and graptolites are notable in their absence. Most organisms present in the shale can be ruled out for a variety of reasons,^[5] but polychaete worms, Promissum conodonts and orthocone cephalopods remain as likely candidates. However, further evidence connecting chitinozoans to any of these groups is circumstantial at best.^[5]

Protists

Alfred Eisenack's original guess was that the Chitinozoa were amoebae, specifically the rhizopod order Testacea, since similar chitin-based tests were produced by the extant members of this group. However, the chemistry of these tests differs from that of the fossils, and modern Testacea are almost exclusively fresh-water—an extremely different environment. Within a year, he had abandoned this initial idea.^[2]

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 Alveolata. 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.^[8] Further, no analogy for the cocoon envelope can be found in this kingdom.^[12]

The cyst forms of a particular group of ciliates, the tintinnids have been suggested to be affiliated to chitinozoans.^[13]

In 2020, exceptionally preserved remains of chitinozoans were described, showing the remains of smaller tests within larger ones, suggesting asexual reproduction.^[6]

Ecology

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.

The fossils' restriction to marine sediments can be taken as sound evidence that the organisms dwelt in the Palæozoic seas—which presents three main modes of life:

Infaunal – living within the sediment—the "burrowers"
Benthic – dwelling upon the sea floor, perhaps anchored in place—the "sitters"
Pelagic – free-floating in the water column—the "drifters"

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.^[8]

The ornament of the chitinozoans may cast light on the question. Whilst in some cases a defensive role—by making the vessel larger, and thus less digestible by would-be predators—seems probable, it is not impossible that the protrusions may have anchored the organisms to the sea floor. However, their low-density construction makes this unlikely:^[8] perhaps more plausible is that they acted to attach to other organisms.^[8] Longer spines also make the organisms more buoyant, by decreasing their Rayleigh number (i.e. increasing the relative importance of water's viscosity)—it 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.^[8]

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.^[8]^[14]^[15] Although some forms have been reinterpreted as "pock-marks" caused by the disintegration of the diagenetic mineral pyrite,^[16] the clustering of cylindrical holes around the chamber—where the flesh of the organism was likely to be concentrated—is evidence for a biological cause.^[8] Corals in Gotland 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.^[8] Such a pattern is also observed in modern-day tropical zooplankton.^[17] 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.^[2] Chitinozoans also become rarer in shallower water—although the reverse is not necessarily true.^[18] They cannot survive freshwater input.^[19]

Stratigraphic application

Since Alfred Eisenack first recognised and named the group^[20] in 1930, the Chitinozoa have proven incredibly useful as a stratigraphic markers in biostratigraphy during the Ordovician, Silurian and Devonian periods. Their utility is due to the rapidity of their morphological evolution, their abundance—the most productive samples bearing almost a thousand tests per gram^[2]—and the easy identification (due largely to the large variation in shapes) and short lifetimes (<10 million years) of most species. They are also widely distributed and appear in a variety of marine depositional settings, 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 acritarchs, chitinozoans were the only reliable means of correlating palæozoic units until the late 1960s, when the detailed study of conodonts and graptolites fully unleashed their stratigraphic potential.^[7]

The oldest known chitinozoans appear to be phosphatized remains tentatively referred to the genus Eisenackitina . They were recovered from the Middle Cambrian (Stage 5)–age Gaotai Formation, more than 20 million years before the group is found elsewhere in the Ordovician.^[21] Chitinozoans appear to have become extinct at the end of the Devonian; rare Carboniferous and Permian remains may represent reworked fossils or fungal spores.^[3]

Related Research Articles

Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian through the Lower Carboniferous (Mississippian). A possible early graptolite, Chaunograptus, is known from the Middle Cambrian. Recent analyses have favored the idea that the living pterobranch Rhabdopleura represents an extant graptolite which diverged from the rest of the group in the Cambrian.

<span class="mw-page-title-main">Acritarch</span> Microfossils

Acritarchs are organic microfossils, known from approximately 1800 million years ago to the present. The classification is a catch all term used to refer to any organic microfossils that cannot be assigned to other groups. Their diversity reflects major ecological events such as the appearance of predation and the Cambrian explosion.

<span class="mw-page-title-main">Choreotrich</span> Subclass of single-celled organisms

The choreotrichs are a group of small marine ciliates. Their name reflects the impression that they appear to dance. The group includes the tintinnids, which produce species-specific loricae (shells), and are important because these may be preserved as microfossils. The cyst forms have been suggested to be affiliated to Chitinozoans, although other studies suggest Chitinozoans to have affinities to larger marine animals, and not tintinnids. Often they have been included among the oligotrichs. Tintinnids seem to be an excessively specious group as over 400 living species have been described, based on characteristics of the lorica or shell.

Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. The group is likely to have appeared first either during the Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic chelicerate order. Following their appearance during the Ordovician, eurypterids became major components of marine faunas during the Silurian, from which the majority of eurypterid species have been described. The Silurian genus Eurypterus accounts for more than 90% of all known eurypterid specimens. Though the group continued to diversify during the subsequent Devonian period, the eurypterids were heavily affected by the Late Devonian extinction event. They declined in numbers and diversity until becoming extinct during the Permian–Triassic extinction event 251.9 million years ago.

<span class="mw-page-title-main">Microfossil</span> Fossil that requires the use of a microscope to see it

A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, such as a hand lens, is referred to as a macrofossil.

Megalograptus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Megalograptus have been recovered in deposits of Katian age in North America. The genus contains five species: M. alveolatus, M. ohioensis, M. shideleri, M. welchi and M. williamsae, all based on fossil material found in the United States. Fossils unassigned to any particular species have also been found in Canada. The generic name translates to "great writing" and originates from the mistaken original belief that Megalograptus was a type of graptolite, often given names ending with -graptus.

<span class="mw-page-title-main">Stromatoporoidea</span> Extinct clade of sponges

Stromatoporoidea is an extinct clade of sea sponges common in the fossil record from the Middle Ordovician to the Late Devonian. They can be characterized by their densely layered calcite skeletons lacking spicules. Stromatoporoids were among the most abundant and important reef-builders of their time, living close together in flat biostromes or elevated bioherms on soft tropical carbonate platforms.

In the geological timescale, the Llandovery Epoch occurred at the beginning of the Silurian Period. The Llandoverian Epoch follows the massive Ordovician-Silurian extinction events, which led to a large decrease in biodiversity and an opening up of ecosystems.

Chasmataspidids, sometime referred to as chasmataspids, are a group of extinct chelicerate arthropods that form the order Chasmataspidida. Chasmataspidids are probably related to horseshoe crabs (Xiphosura) and/or sea scorpions (Eurypterida), with more recent studies suggest that they form a clade (Dekatriata) with Eurypterida and Arachnida. Chasmataspidids are known sporadically in the fossil record through to the mid-Devonian, with possible evidence suggesting that they were also present during the late Cambrian. Chasmataspidids are most easily recognised by having an opisthosoma divided into a wide forepart (preabdomen) and a narrow hind part (postabdomen) each comprising 4 and 9 segments respectively. There is some debate about whether they form a natural group.

Drepanopterus is an extinct genus of eurypterid and the only member of the family Drepanopteridae within the Mycteropoidea superfamily. There are currently three species assigned to the genus. The genus has historically included more species, with nine species having been associated with the genus Drepanopterus. Five of these have since been proven to be synonyms of pre-existing species, assigned to their own genera, or found to be based on insubstantial fossil data. The holotype of one species proved to be a lithic clast.

<i>Nanahughmilleria</i> Extinct genus of arthropods

Nanahughmilleria is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Nanahughmilleria have been discovered in deposits of Devonian and Silurian age in the United States, Norway, Russia, England and Scotland, and have been referred to several different species.

Onychopterella is a genus of predatory eurypterid, an extinct group of aquatic arthropods. Fossils of Onychopterella have been discovered in deposits from the Late Ordovician to the Late Silurian. The genus contains three species: O. kokomoensis, the type species, from the Early Pridoli epoch of Indiana; O. pumilus, from the Early Llandovery epoch of Illinois, both from the United States; and O. augusti, from the Late Hirnantian to Early Rhuddanian stages of South Africa.

Echinognathus is a genus of eurypterid, an extinct group of aquatic arthropods. The type and only species of Echinognathus, E. clevelandi, is known from deposits of Late Ordovician age in the United States. The generic name is derived from the Neo-Latin echino- ("spiny") and the Greek gnáthos ("jaw"), in reference to a spiny endognathary appendage part of the fossil type material.

The Rhenopteridae are a family of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". The family is the only family currently contained in the superfamily Rhenopteroidea, one of four superfamilies classified as part of the suborder Stylonurina.

Alfred Eisenack was a German paleontologist. He was a pioneer of micropaleontology and palynology. His botanical and mycological author abbreviation is "Eisenack".

Paleontology in Wisconsin refers to paleontological research occurring within or conducted by people from the U.S. state of Wisconsin. The state has fossils from the Precambrian, much of the Paleozoic, some a parts of the Mesozoic and the later part of the Cenozoic. Most of the Paleozoic rocks are marine in origin. Because of the thick blanket of Pleistocene glacial sediment that covers the rock strata in most of the state, Wisconsin’s fossil record is relatively sparse. In spite of this, certain Wisconsin paleontological occurrences provide exceptional insights concerning the history and diversity of life on Earth.

Angochitina is an extinct genus of chitinozoans. It was described by Alfred Eisenack in 1931.

Adelophthalmidae is a family of eurypterids, an extinct group of aquatic arthropods. Adelophthalmidae is the only family classified as part of the superfamily Adelophthalmoidea, which in turn is classified within the infraorder Diploperculata in the suborder Eurypterina.

Eurypterina is one of two suborders of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". Eurypterine eurypterids are sometimes informally known as "swimming eurypterids". They are known from fossil deposits worldwide, though primarily in North America and Europe.

Panderodus Is an extinct genus of jawless fish belonging to the order Conodonta. This genus had a long temporal range, surviving from the middle Ordovician to late Devonian. In 2021, extremely rare body fossils of Panderodus from the Waukesha Biota were described, and it revealed that Panderodus had a more thick body compared to the more slender bodies of more advanced conodonts. It also revealed that this conodont was a macrophagous predator, meaning it went after large prey.

References

↑ Gary Lee Mullins (2000). "A chitinozoan morphological lineage and its importance in Lower Silurian stratigraphy". Palaeontology. 43 (2): 359–373. Bibcode:2000Palgy..43..359M. doi: 10.1111/1475-4983.00131 .
1 2 3 4 5 Jansonius, J.; Jenkins, W.A.M. (1978). "Chitinozoa". Introduction to marine micropaleontology. Elsevier, New York. pp. 341–357. ISBN 0-444-00267-7.
1 2 3 4 5 Jain, Sreepat (2020), Jain, Sreepat (ed.), "Chitinozoa", Fundamentals of Invertebrate Palaeontology: Microfossils, Springer Geology, New Delhi: Springer India, pp. 1–25, doi: 10.1007/978-81-322-3962-8_1 , ISBN 978-81-322-3962-8, S2CID 241650725
↑ Grahn, Yngve; Pereira, Egberto; Bergamaschi, Sergio (24 August 2010). "Middle and upper Devonian chitinozoan biostratigraphy of the paraná basin in Brazil and Paraguay". Palynology. 26 (1): 135–165. doi:10.1080/01916122.2002.9989570. S2CID 128673881 . Retrieved 8 November 2022.
1 2 3 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". Journal of the Geological Society. 155 (3): 447–452. Bibcode:1998JGSoc.155..447G. doi:10.1144/gsjgs.155.3.0447. S2CID 129236534.
1 2 Liang, Yan; Hints, Olle; Tang, Peng; Cai, Chenyang; Goldman, Daniel; Nõlvak, Jaak; Tihelka, Erik; Pang, Ke; Bernardo, Joseph; Wang, Wenhui (2020-12-01). "Fossilized reproductive modes reveal a protistan affinity of Chitinozoa". Geology. 48 (12): 1200–1204. Bibcode:2020Geo....48.1200L. doi: 10.1130/G47865.1 . ISSN 0091-7613.
1 2 3 4 5 6 7 Jenkins, W.A.M. (1970). "Chitinozoa". Proceedings of the Annual Meeting. American Association of Stratigraphic Palynologists. 1: 1–21. doi:10.2307/3687298. JSTOR 3687298.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Laufeld, S. (1974). "Silurian Chitinozoa from Gotland". Fossils and Strata. 5. Universitetsforlaget: 1–130. doi:10.18261/8200093581-1974-01. ISBN 82-00-09358-1. ISSN 0300-9491.
↑ Liang, Yan; Bernardo, Joseph; Goldman, Daniel; Nõlvak, Jaak; Tang, Peng; Wang, Wenhui; Hints, Olle (2019-08-14). "Morphological variation suggests that chitinozoans may be fossils of individual microorganisms rather than metazoan eggs". Proceedings of the Royal Society B: Biological Sciences. 286 (1908): 20191270. doi:10.1098/rspb.2019.1270. ISSN 0962-8452. PMC 6710598 . PMID 31362642.
↑ one of which, Mirachitina , is no longer recognised as a chitinozoan
1 2 3 Tappan, H. (1966). "Chitinozoan Classification". Journal of Paleontology. 40 (6): 1394–1396. JSTOR 1301963.
1 2 Kozlowski, R. (1963). "Sur la nature des chitinozoaires". Acta Palaeontologica Polonica. 8: 425–45.
↑ Reid, P. C. and A. W. G. John: A possible relationship between chitinozoa and tintinnids. Rev. Paleobot. Palynol. 34, 251-262 (1981).
↑ Eisenack, A. (1931). "Neue Mikrofossilien des baltischen Silurs". Naturwissenschaften (in German). 18 (42): 880–881. Bibcode:1930NW.....18..880E. doi:10.1007/BF01488901. S2CID 23050887.
↑ Eisenack, A. (1968). "Uber Chitinozoen des baltischen Gebietes". Palaeontographica, Abteilung A (in German). 131: 137–98.
↑ Martin, F. (197). "Palynofacies et microfacies du Silurien inférieur a Deerlijk". Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre, Bulletin (in French). 47 (10): 11–12 (of 26).
↑ Raymont, JEG (1972). Plankton & productivity in the oceans . Oxford: Pergamon Press. p. 489. ISBN 0-08-021551-3.
↑ 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". Review of Palaeobotany and Palynology. 113 (1–3): 197–212. Bibcode:2000RPaPa.113..197W. doi:10.1016/S0034-6667(00)00060-9. PMID 11164220.
↑ Sutherland, S.J.E.; Palaeontographical Society Monographs (1994). Ludlow Chitinozoans from the Type Area and Adjacent Regions. Palaeontographical Society. pp. 1–124.
↑ After "their chitinoid appearance"
↑ Shen, Cen; Aldridge, Richard J.; Williams, Mark; Vandenbroucke, Thijs R.A.; Zhang, Xi-guang (2013-02-01). "Earliest chitinozoans discovered in the Cambrian Duyun fauna of China". Geology. 41 (2): 191–194. Bibcode:2013Geo....41..191S. doi:10.1130/G33763.1. ISSN 0091-7613.

External links

Commission Internationale de Microflore du Paléozoique (CIMP), international commission for Palaeozoic palynology.

Fossil range

Chitinozoans

Permian

Neogene

│

−600

│

−550

│

−500

│

−450

│

−400

│

−350

│

−300

│

−250

│

−200

│

−150

│

−100

│

−50

│

0

Millions of years ago

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[Mullins-1] Gary Lee Mullins (2000). "A chitinozoan morphological lineage and its importance in Lower Silurian stratigraphy". Palaeontology. 43 (2): 359–373. Bibcode:2000Palgy..43..359M. doi: 10.1111/1475-4983.00131 .

[Jansonius1978-2] 1 2 3 4 5 Jansonius, J.; Jenkins, W.A.M. (1978). "Chitinozoa". Introduction to marine micropaleontology. Elsevier, New York. pp. 341–357. ISBN 0-444-00267-7.

[:1-3] 1 2 3 4 5 Jain, Sreepat (2020), Jain, Sreepat (ed.), "Chitinozoa", Fundamentals of Invertebrate Palaeontology: Microfossils, Springer Geology, New Delhi: Springer India, pp. 1–25, doi: 10.1007/978-81-322-3962-8_1 , ISBN 978-81-322-3962-8, S2CID 241650725

[GrahnPereiraBergamaschi2010ChitinozoanBiostrat-4] Grahn, Yngve; Pereira, Egberto; Bergamaschi, Sergio (24 August 2010). "Middle and upper Devonian chitinozoan biostratigraphy of the paraná basin in Brazil and Paraguay". Palynology. 26 (1): 135–165. doi:10.1080/01916122.2002.9989570. S2CID 128673881 . Retrieved 8 November 2022.

[Gabbott1998-5] 1 2 3 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". Journal of the Geological Society. 155 (3): 447–452. Bibcode:1998JGSoc.155..447G. doi:10.1144/gsjgs.155.3.0447. S2CID 129236534.

[:0-6] 1 2 Liang, Yan; Hints, Olle; Tang, Peng; Cai, Chenyang; Goldman, Daniel; Nõlvak, Jaak; Tihelka, Erik; Pang, Ke; Bernardo, Joseph; Wang, Wenhui (2020-12-01). "Fossilized reproductive modes reveal a protistan affinity of Chitinozoa". Geology. 48 (12): 1200–1204. Bibcode:2020Geo....48.1200L. doi: 10.1130/G47865.1 . ISSN 0091-7613.

[Jenkins1970-7] 1 2 3 4 5 6 7 Jenkins, W.A.M. (1970). "Chitinozoa". Proceedings of the Annual Meeting. American Association of Stratigraphic Palynologists. 1: 1–21. doi:10.2307/3687298. JSTOR 3687298.

[Laufeld1974-8] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Laufeld, S. (1974). "Silurian Chitinozoa from Gotland". Fossils and Strata. 5. Universitetsforlaget: 1–130. doi:10.18261/8200093581-1974-01. ISBN 82-00-09358-1. ISSN 0300-9491.

[9] Liang, Yan; Bernardo, Joseph; Goldman, Daniel; Nõlvak, Jaak; Tang, Peng; Wang, Wenhui; Hints, Olle (2019-08-14). "Morphological variation suggests that chitinozoans may be fossils of individual microorganisms rather than metazoan eggs". Proceedings of the Royal Society B: Biological Sciences. 286 (1908): 20191270. doi:10.1098/rspb.2019.1270. ISSN 0962-8452. PMC 6710598 . PMID 31362642.

[10] which, Mirachitina , is no longer recognised as a chitinozoan

[Tappan1966-11] 1 2 3 Tappan, H. (1966). "Chitinozoan Classification". Journal of Paleontology. 40 (6): 1394–1396. JSTOR 1301963.

[Kozlowski1963-12] 1 2 Kozlowski, R. (1963). "Sur la nature des chitinozoaires". Acta Palaeontologica Polonica. 8: 425–45.

[13] Reid, P. C. and A. W. G. John: A possible relationship between chitinozoa and tintinnids. Rev. Paleobot. Palynol. 34, 251-262 (1981).

[Eisenack1931-14] Eisenack, A. (1931). "Neue Mikrofossilien des baltischen Silurs". Naturwissenschaften (in German). 18 (42): 880–881. Bibcode:1930NW.....18..880E. doi:10.1007/BF01488901. S2CID 23050887.

[Eisenack1968-15] Eisenack, A. (1968). "Uber Chitinozoen des baltischen Gebietes". Palaeontographica, Abteilung A (in German). 131: 137–98.

[Martin1971-16] Martin, F. (197). "Palynofacies et microfacies du Silurien inférieur a Deerlijk". Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre, Bulletin (in French). 47 (10): 11–12 (of 26).

[Raymont1972-17] Raymont, JEG (1972). Plankton & productivity in the oceans . Oxford: Pergamon Press. p. 489. ISBN 0-08-021551-3.

[Winchester-seeto2000-18] 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". Review of Palaeobotany and Palynology. 113 (1–3): 197–212. Bibcode:2000RPaPa.113..197W. doi:10.1016/S0034-6667(00)00060-9. PMID 11164220.

[Sutherland1994-19] Sutherland, S.J.E.; Palaeontographical Society Monographs (1994). Ludlow Chitinozoans from the Type Area and Adjacent Regions. Palaeontographical Society. pp. 1–124.

[20] After "their chitinoid appearance"

[21] Shen, Cen; Aldridge, Richard J.; Williams, Mark; Vandenbroucke, Thijs R.A.; Zhang, Xi-guang (2013-02-01). "Earliest chitinozoans discovered in the Cambrian Duyun fauna of China". Geology. 41 (2): 191–194. Bibcode:2013Geo....41..191S. doi:10.1130/G33763.1. ISSN 0091-7613.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[14]

[15]

[16]

[17]

[18]

[19]

[20]

[21]