biology

Redfieldius

Redfieldius 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 Redfieldius rather than just read about it. In short: Redfieldius is an extinct genus of freshwater ray-finned fish that inhabited eastern North America during the Early Jurassic period. It contains a single species, R. gracilis, known from the Hettangian to the Sinemurian of the northeastern United States.

Key takeaways

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

Reference excerpt

Redfieldius is an extinct genus of freshwater ray-finned fish that inhabited eastern North America during the Early Jurassic period. It contains a single species, R. gracilis, known from the Hettangian to the Sinemurian of the northeastern United States. It is the type genus and was the last surviving member of the order Redfieldiiformes, which was widespread and diverse throughout the preceding Triassic period. It is notable for representing possibly the first fossil bony fish collected from North America, with a specimen from Middletown collected in 1816 by Benjamin Silliman.

Taxonomy

It was initially described in the genus Catopterus by naturalist John Howard Redfield, but later taxonomic revisions found Catopterus to already be a synonym for the early lungfish Dipterus. Due to this, Oliver Perry Hay reclassified it into the new genus Redfieldius, named in honor of Redfield. Previously, many other species were classified into Catopterus/Redfieldius, but most of these have either been synonymized with R. gracilis or (in the case of former Triassic species classified into this genus) moved into their own genera.

Distribution Redfieldius appears to have been widespread in the rift lakes of the upper Newark Supergroup, with fossils known from Connecticut (East Berlin, Portland & Shuttle Meadow Formations), New Jersey (Boonton Formation), and Virginia (Midland Formation). There have also been reports from Massachusetts, but no specimens have been identified.

Description

Redfieldius was of medium size, and usually did not exceed 20 centimeters in length. The body was slightly robust, oval in shape; the snout was rounded, the eyes large and the mouth was equipped with small teeth. Like all its close relatives, Redfieldius also had a single triangular dorsal fin set far back, practically mirroring the anal fin, which was very similar in shape and size. The ventral fins were small, while the pectoral fins were slightly larger. The caudal fin was slightly heterocercal, while there was a single branchiostegal reduced to a plate-shaped bone. All the fins were equipped with extremely thin fulcrums. The scales were rhomboid, and those in the anterior part of the body were larger, arranged in diagonal rows. The external nasal opening was enclosed by a premaxillary bone, a nasal, a rostral and an adnasal bone. Redfieldius, unlike other closely related fish, had a skull heavily ornamented with tubercles, particularly the area around the orbit and the tip of the snout.

References

Illustrations

Worked examples

Example 1 — a first encounter with Redfieldius

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

In research: Redfieldius 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 Redfieldius 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: Redfieldius is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fossil taxa described in 1899, Fossils of New Jersey, Fossils of the United States, so understanding it makes those chapters shorter.
In everyday life: Look for Redfieldius 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 Redfieldius in 20 minutes

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

Frequently asked questions

What is Redfieldius in simple terms?

Why does Redfieldius 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 Redfieldius?

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 Redfieldius.