biology

Psiloceras

Psiloceras is a biology 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 Psiloceras rather than just read about it. In short: Psiloceras is an extinct genus of ammonite. Psiloceras is among the earliest known Jurassic ammonites, and the appearance of the earliest Psiloceras species form the definition for the base of the Jurassic.

Key takeaways

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

Reference excerpt

Psiloceras is an extinct genus of ammonite. Psiloceras is among the earliest known Jurassic ammonites, and the appearance of the earliest Psiloceras species form the definition for the base of the Jurassic. Unlike most earlier ammonites, which had complex shell shapes and ornamentation, Psiloceras had a smooth shell.

Taxonomy Almost all ammonites, with the sole exemption of a few members of the family Psiloceratidae, including Psiloceras were wiped out at the Triassic–Jurassic extinction event (201.3 million years ago). Most authors assume that Psiloceras descended from the Phyllocerataceae. P. spelae is probably the earliest species of Psiloceras.

Biostratigraphic significance The International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of the Psiloceras spela-group as the defining biological marker for the start of the Hettangian, 201.3 ± 0.2 million years ago, the earliest stage of the Jurassic, with the Global Boundary Stratotype Section and Point (GSSP) located at Kuhjoch pass, Karwendel Mountains, Northern Calcareous Alps, Austria, which was ratified in 2010. The base of the Jurassic in Britain was historically defined by the first appearance of the ammonite Psiloceras planorbis.

Distribution Jurassic of Argentina, Austria, Canada, China, France, Germany, New Zealand, Spain, the United Kingdom, United States Psiloceras fossils are commonly found at Watchet, Somerset, England. Here smooth-shelled Psiloceras planorbis (along with other species) are to be found as usually flattened fossils in the Blue Lias.

References

Illustrations

Worked examples

Example 1 — a first encounter with Psiloceras

Start with the simplest possible case. Write down what Psiloceras claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 Psiloceras 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 Psiloceras 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 Psiloceras

In research: Psiloceras appears in biology 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 Psiloceras 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: Psiloceras is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ammonites of North America, Ammonitida genera, Ammonitina stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Psiloceras 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.

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How to study Psiloceras in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Psiloceras 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 Psiloceras out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Psiloceras in simple terms?

Why does Psiloceras matter?

Because it connects several biology 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 Psiloceras?

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 Psiloceras.