science

Hexanchus microdon

Hexanchus microdon 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 Hexanchus microdon rather than just read about it. In short: Hexanchus microdon is an extinct species of sixgill shark that was found worldwide from the mid-Cretaceous to the Paleocene. Taxonomy One of the earliest known sixgill sharks in the fossil record, it was described by Louis Agassiz in 1835, but was originally identified by Gideon Mantell in 1822 as a Squalus tooth.

Key takeaways

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

Reference excerpt

Hexanchus microdon is an extinct species of sixgill shark that was found worldwide from the mid-Cretaceous to the Paleocene.

Taxonomy One of the earliest known sixgill sharks in the fossil record, it was described by Louis Agassiz in 1835, but was originally identified by Gideon Mantell in 1822 as a Squalus tooth. The name has been often applied to any shark teeth from the Late Cretaceous of Europe with a small morphology reminiscent of the modern bigeye sixgill shark, and taxonomic revisions are likely necessary, especially due to the non-informative nature of the type specimens. Teeth from as late as the Early Eocene of Morocco have also been referred to this species, even while concurrent Hexanchus species in other regions are known by different names. In contrast, at some areas such as the Late Cretaceous of Germany, it appears to be the only Hexanchus species confidently present. Hexanchus gracilis, a species known from complete fossil skeletons from the Sahel Alma site in Lebanon, may be potentially synonymous with it.

Occurrences Based on the Paleobiology Database:

Early Cretaceous ?Aptian of Iwate, Japan (Hiraiga Formation)

Late Cretaceous

Europe Cenomanian of Germany (Hesseltal Formation) Cenomanian of England (Cambridge Greensand) Cenomanian of Lithuania (Labguva Formation) Turonian of Germany (Salder Formation) Coniacian of France (Lezennes Chalk) Santonian of Germany (Burgsteinfurt Formation) Campanian of England (upper English Chalk) Campanian of Belgium (Trivières Chalk) Campanian of Germany (Beckum Formation) Maastrichtian of Saratov, Russia (Karsun Formation) Maastrchtian of Austria (Gerhartsreit Formation)

North America Campanian of British Columbia, Canada (Northumberland Formation)

Asia Cenomanian of Hokkaido, Japan Coniacian of Fukushima, Japan (Ashizawa Formation) Santonian of Kumamoto, Japan (Hinoshima Formation) Campanian of Ehime, Japan (Izumi Group) Campanian of Israel (Mishash Formation) Maastrichtian of Israel (Ghared Formation)

Africa Coniacian of Angola (Itombe Formation) Campanian of Angola Maastrichtian of Egypt Maastrichtian of Morocco (Ganntour Basin)

Paleogene

Europe Danian of Denmark (Rødvig Formation)

North America Danian of New Jersey, US (Hornerstown Formation) ?Thanetian of California, US (Lodo Formation)

References

Worked examples

Example 1 — a first encounter with Hexanchus microdon

Start with the simplest possible case. Write down what Hexanchus microdon 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 Hexanchus microdon 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 Hexanchus microdon 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 Hexanchus microdon

In research: Hexanchus microdon 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 Hexanchus microdon 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: Hexanchus microdon is common in secondary-school and first-year university syllabi. It links to neighbouring topics Campanian life, Cenomanian first appearances, Coniacian life, so understanding it makes those chapters shorter.
In everyday life: Look for Hexanchus microdon 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 Hexanchus microdon in 20 minutes

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

Frequently asked questions

What is Hexanchus microdon in simple terms?

Hexanchus microdon is an extinct species of sixgill shark that was found worldwide from the mid-Cretaceous to the Paleocene. Taxonomy One of the earliest known sixgill sharks in the fossil record, it was described by Louis Agassiz in 1835, but was originally identified by Gideon Mantell in 1822 as…

Why does Hexanchus microdon 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 Hexanchus microdon?

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 Hexanchus microdon.