science

Plagiomenidae

Plagiomenidae 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 Plagiomenidae rather than just read about it. In short: Plagiomenidae is an extinct family of mammals from the Paleocene–Eocene of North America. Mainly known from teeth and jaw bones, plagiomenids are often regarded as early members of Dermoptera, the order which contains the modern colugos or "flying lemurs" of southeast Asia.

Key takeaways

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

Reference excerpt

Plagiomenidae is an extinct family of mammals from the Paleocene–Eocene of North America. Mainly known from teeth and jaw bones, plagiomenids are often regarded as early members of Dermoptera, the order which contains the modern colugos or "flying lemurs" of southeast Asia. Some studies argue that plagiomenids are too specialized to be close relatives of colugos, though others continue to uphold a relationship between the two groups. No fossils are known beyond the skull, so it is unknown whether plagiomenids could glide like their potential modern relatives. Plagiomenids were sometimes suggested to be descendants of mixodectids or ancestors to tarkadectines, two other extinct groups of primate-like North American mammals. A direct line of ancestry is no longer supported for either. Mixodectids are a distinct family of non-gliding euarchontans (mammals in the vicinity of the split between colugos and primates). Tarkadectines are probably a subfamily of Omomyidae (early relatives of tarsiers).

Description Plagiomenid teeth and skull fossils are similar to colugos in some respects, as well as more distant mammals such as desmans and elephant shrews. The two to three lower incisors are large, with the first being the largest. The lower incisors split into mitten-shaped crowns akin to some elephant shrews. By comparison, colugo incisors split further into toothcombs with many small tines. Plagiomenids have four premolars and three molars on each side of the jaw, though the last two premolars are molarized (acquiring a similar shape to the molars). The molars and molarized premolars are together known as molariform teeth. Like colugos, the molariforms are crenulated (strongly wrinkled) and partially split by a sideways furrow down the middle of each tooth. The upper molariforms lack hypocones, while the lower molariforms have particularly large cusps in the talonid region (the rear "heel" of the tooth). Like colugos, plagiomenids were probably herbivores relying on sideways shearing and grinding motions in their teeth. Plagiomenids also have a few unique traits not present in colugos. For example, the upper molariforms have many stylar cusps (small cusps along the outer rim of the tooth), alongside enlarged paraconules and metaconules. Each molariform tooth has a skewed profile, where the inner half of each tooth is shifted forwards relative to its outer half. The snout is narrow, and the back of the jaw has a deep coronoid process and small gonial area, opposite from colugos. Apart from teeth and jaws, Plagiomene also preserves a fragmentary braincase which is very different in structure compared to colugos. The auditory bulla (a bony dome which protects the middle and inner ear) is unusually complex, with up to seven components encasing a porous tympanic cavity.

References

Worked examples

Example 1 — a first encounter with Plagiomenidae

Start with the simplest possible case. Write down what Plagiomenidae 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 Plagiomenidae 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 Plagiomenidae 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 Plagiomenidae

In research: Plagiomenidae 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 Plagiomenidae 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: Plagiomenidae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Colugos, Eocene extinctions, Eocene mammals of North America, so understanding it makes those chapters shorter.
In everyday life: Look for Plagiomenidae 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 Plagiomenidae in 20 minutes

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

Frequently asked questions

What is Plagiomenidae in simple terms?

Why does Plagiomenidae 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 Plagiomenidae?

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 Plagiomenidae.