science

Plantigrade

Plantigrade 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 Plantigrade rather than just read about it. In short: In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals.

Key takeaways

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

Reference excerpt

In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals. The other options are digitigrade, walking on the toes and fingers with the heel and wrist permanently raised, and unguligrade, walking on the nail or nails of the toes (the hoof) with the heel/wrist and the digits permanently raised. The leg of a plantigrade mammal includes the bones of the upper leg (femur/humerus) and lower leg (tibia and fibula/radius and ulna). The leg of a digitigrade mammal also includes the metatarsals/metacarpals, the bones that in a human compose the arch of the foot and the palm of the hand. The leg of an unguligrade mammal also includes the phalanges, the finger and toe bones.

Among extinct animals, most early mammals such as pantodonts were plantigrade. A plantigrade foot is the primitive condition for mammals; digitigrade and unguligrade locomotion evolved later. Among archosaurs, the pterosaurs were partially plantigrade and walked on the whole of the hind foot and the fingers of the hand-wing. Out of the plantigrade animals, only a few, such as humans, kangaroos and certain rodents, are obligate bipeds, while most others are functional bipeds.

List of plantigrade animals Plantigrade animals species include (but are not limited to):

Mammals Several primates (including humans and lemurs) Carnivora: Ursidae: bears amphicyonids Musteloidea: skunks, raccoons, weasels, badgers, otters, and red pandas Nimravids: false saber-tooth cats Oxyaenids Rodents: mice, rats, porcupines Hedgehogs Hyraxes Marsupialia: kangaroos, opossums Nearly all basal mammals and non-mammalian synapsids were plantigrade Birds Loons, grebes and penguins Reptiles Nearly all reptiles (including pterosaurs but excluding dinosaurs (including most birds) which are digitigrade or semi-digitigrade) are plantigrade Amphibians All amphibians are plantigrade

Evolution The primary advantages of a plantigrade foot are stability and weight-bearing ability; plantigrade feet have the largest surface area. The primary disadvantage of a plantigrade foot is speed. With more bones and joints in the foot, the leg is both shorter and heavier at the far end, which makes it difficult to move rapidly. In humans and other great apes, another possible advantage of a plantigrade foot is that it may enhance fighting performance by providing a more powerful stance for striking and grappling. Plantigrade foot occurs normally in humans in static postures of standing and sitting. It should also occur normally in gait (walking). Hypertonicity, spasticity, clonus, limited range of motion, abnormal flexion neural pattern, and a plantar flexor (calf) muscle contracture, as well as some forms of footwear such as high heeled shoes may contribute to an individual only standing and/or walking on their toes. It would be evident by the observable heel rise.

See also Chebyshev lambda linkage, referred to as the plantigrade machine in its debut.

References

Illustrations

Plantigrade: Portion of a human skeleton, showing plantigrade habit — Portion of a human skeleton, showing plantigrade habit

Worked examples

Example 1 — a first encounter with Plantigrade

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

In research: Plantigrade 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 Plantigrade 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: Plantigrade is common in secondary-school and first-year university syllabi. It links to neighbouring topics Terrestrial locomotion, so understanding it makes those chapters shorter.
In everyday life: Look for Plantigrade 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 Plantigrade in 20 minutes

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

Frequently asked questions

What is Plantigrade in simple terms?

In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals.

Why does Plantigrade 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 Plantigrade?

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 Plantigrade.