science

Proarticulata

Proarticulata is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Proarticulata rather than just read about it. In short: Proarticulata is a phylum of extinct, near-bilaterally symmetrical animals known from fossils found mainly in the Ediacaran (Vendian) marine deposits, with some few possible related specimen found through Cambrian until late Devonian, and dates to approximately 567 to 550 million years ago. The name comes from the Greek προ (pro-) = "before" and Articulata, i.e. prior to animals with true segmentation such as anneli…

Key takeaways

Proarticulata belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Proarticulata to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Proarticulata from memory before moving on to harder problems.

Reference excerpt

Proarticulata is a phylum of extinct, near-bilaterally symmetrical animals known from fossils found mainly in the Ediacaran (Vendian) marine deposits, with some few possible related specimen found through Cambrian until late Devonian, and dates to approximately 567 to 550 million years ago. The name comes from the Greek προ (pro-) = "before" and Articulata, i.e. prior to animals with true segmentation such as annelids and arthropods. This phylum was established by Mikhail A. Fedonkin in 1985 for such animals as Dickinsonia, Vendia, Cephalonega, Praecambridium and currently many other Proarticulata are described (see list). Due to their simplistic morphology, their affinities and mode of life are subject to debate. They are almost universally considered to be metazoans, and due to possessing a clear central axis have been suggested to be stem-bilaterians. In the traditional interpretation, the proarticulatan body is divided into transverse articulation (division) into isomers as distinct from the transverse articulation segments in annelids and arthropods, as their individual isomers occupy only half the width of their bodies, and are organized in an alternating pattern along the longitudinal axis of their bodies. In other words, one side is not the direct mirror image of its opposite (chirality). Opposite isomers of left and right side are located with displacement of half of their width. This phenomenon is described as the symmetry of gliding reflection. Some recent research suggests that some proarticulatans like Dickinsonia have genuine segments, and the isomerism is superficial and due to taphonomic distortion. However, other researchers dispute this. Displacement of left-right axis is known in bilaterians, notably lancelets.

Morphology

Vendiamorpha

The body is completely segmented, with all isomers curved towards the posterior, and the first isomer is normally much larger than the rest. The first two isomers at the anterior dorsal end are partly fused. (e.g., Vendia, Paravendia and Karakhtia).

Cephalozoa

These proarticulatans are incompletely segmented, as the anterior zone is free of isomers, often making a "hairband" like appearance (example cephalozoans include Yorgia, Praecambridium, Andiva, Archaeaspinus, Ivovicia, Podolimirus, Tamga, Spriggina, Marywadea and Cyanorus). Some cephalozoans from the family Yorgiidae demonstrate pronounced asymmetry of the left and right parts of the body. For instance, Yorgia's initial right isomer is the only one which spreads far towards the left side of the body. Archaeaspinus has an unpaired anterior lobe confined by the furrow to the left side only.

In Cephalonega stepanovi and Tamga hamulifera the zone containing the isomers is encircled by a peripheral, undivided zone. The Cephalonega's isomers are connected to each other, forming a body resembling a rubber raft; the Tamga's isomers are separated from each other, and do not touch. In Lossinia, the center undivided region has no visible isomers, instead having the lobe-like isomers emanate from the periphery of the undivided region as "transverse articulations."

Dipleurozoa

The dipleurozoan body is subradial, divided by isomers entirely (e.g., Dickinsonia and Phyllozoon). Dickinsonia juveniles show undivided anterior areas but these regions were reduced in the course of ontogeny, and in the adult stages Dickinsonia-like proarticulates changed so radically that they became almost indistinguishable from isomers.

List of proarticulates

Body fossils Armillifera Fedonkin, 1980 A. parva Fedonkin, 1980 Andiva Fedonkin, 2002 A. ivantsovi Fedonkin, 2002 Archaeaspinus Ivantsov, 2007 (=Archaeaspis Ivantsov, 2001) A. fedonkini Ivantsov, 2001 Cephalonega Ivantsov et al., 2019 C. stepanovi (Fedonkin, 1976) Chondroplon Wade, 1971 (possible =Dickinsonia) C. bilobatum Wade, 1971 Cyanorus Ivantsov, 2004 C. singularis Ivantsov, 2004 Dickinsonia Sprigg, 1947 D. costata Sprigg, 1947 D. menneri Keller 1976 (=Vendomia menneri Keller 1976) D. tenuis Glaessner & Wade, 1966 Ivovicia Ivantsov, 2007 I. rugulosa Ivantsov, 2007 Karakhtia Ivantsov, 2004 K. nessovi Ivantsov, 2004 Lossinia Ivantsov, 2007 L. lissetskii Ivantsov, 2007 Marywadea Glaessner, 1976 M. ovata Glaessner & Wade, 1966 Ovatoscutum Glaessner & Wade, 1966 O. concentricum Glaessner & Wade, 1966 Paravendia Ivantsov, 2004 P. janae Ivantsov, 2001 (=Vendia janae Ivantsov, 2001) Podolimirus Fedonkin, 1983 (=Valdainia Fedonkin, 1983) P. mirus Fedonkin, 1983 (Valdainia plumosa Fedonkin, 1983) Praecambridium Glaessner & Wade, 1966 P. siggilum Glaessner & Wade, 1966 Spriggina Glaessner, 1958 S. floundersi Glaessner, 1958 Tamga Ivantsov, 2007 T. hamulifera Ivantsov, 2007 Vendia Keller, 1969 V. sokolovi Keller, 1969 V. rachiata Ivantsov, 2004 ? Windermeria Narbonne, 1994 W. aitkeni Narbonne, 1994 Yorgia Ivantsov, 1999 Y. waggoneri Ivantsov, 1999

Trace fossils Epibaion Ivantsov, 2002 E. axiferus Ivantsov, 2002. E. waggoneris Ivantsov, 2011. This is a trace of Yorgia waggoneri E. costatus Ivantsov, 2011. This is a trace of Dickinsonia costata Phyllozoon Jenkins & Gehling, 1978 P. hanseni Jenkins & Gehling, 1978

See also Articulata List of Ediacaran genera

References

External links Database of Ediacaran Biota Advent of Complex Life

Illustrations

Worked examples

Example 1 — a first encounter with Proarticulata

Start with the simplest possible case. Write down what Proarticulata claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Proarticulata before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Proarticulata ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Proarticulata

In research: Proarticulata appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Proarticulata in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Proarticulata is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bilateria phyla, Proarticulata, Vendobionta, so understanding it makes those chapters shorter.
In everyday life: Look for Proarticulata outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Proarticulata in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Proarticulata means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Proarticulata out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Proarticulata in simple terms?

Why does Proarticulata matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Proarticulata?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Proarticulata.