earth science

Triassic land vertebrate faunachrons

Triassic land vertebrate faunachrons is a earth 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 Triassic land vertebrate faunachrons rather than just read about it. In short: Land vertebrate faunachrons (LVFs) are biochronological units used to correlate and date terrestrial sediments and fossils based on their tetrapod faunas. First formulated on a global scale by Spencer G.

Key takeaways

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Reproduce the core statement of Triassic land vertebrate faunachrons from memory before moving on to harder problems.

Reference excerpt

Land vertebrate faunachrons (LVFs) are biochronological units used to correlate and date terrestrial sediments and fossils based on their tetrapod faunas. First formulated on a global scale by Spencer G. Lucas in 1998, LVFs are primarily used within the Triassic Period (252 - 201 Ma), though Lucas later designated LVFs for other periods as well. Eight worldwide LVFs are defined for the Triassic. The first two earliest Triassic LVFs, the Lootsbergian and Nonesian, are based on South African synapsids and faunal assemblage zones estimated to correspond to the Early Triassic. These are followed by the Perovkan and Berdyankian, based on temnospondyl amphibians and Russian assemblages estimated to be from the Middle Triassic. The youngest four Triassic LVFs, the Otischalkian, Adamanian, Revueltian, and Apachean, are based on aetosaur and phytosaur reptiles common in the Late Triassic of the southwestern United States. The LVF system, though widely used, is also a controversial application of biostratigraphy, as many Triassic tetrapods are rife with complications which endanger their utility as index fossils. Limited occurrences, inaccurate age estimates, overlapping LVF faunas, or taxonomic disagreement may jeopardize global correlations between Triassic tetrapods. This could render some LVFs as misleading assessments of Triassic faunal change through time. Regardless, Late Triassic phytosaurs are considered to have strong biostratigraphic utility even among detractors of Lucas's system.

Lucas's LVFs Tetrapod biostratigraphy has been used for the Triassic of South Africa since 1906 and Argentina since 1966, but without much connection to global faunas. Starting in 1993, New Mexico Museum of Natural History and Science paleontologist Spencer G. Lucas and his colleagues began to define tetrapod biostratigraphy intervals in the Triassic of China and eastern and western North America. These named biostratigraphic intervals were inspired by the Land Mammal Age (LMA) system already in use for Cenozoic faunal assemblages. Triassic tetrapod biozones, under the term "land vertebrate faunachrons" (LVFs) were formalized on a global level by Lucas in 1998. They were diagnosed by a primary index fossil (a particular genus of widespread time-constrained tetrapod) and characterized by a faunal type assemblage (distinguishing collection of taxa) from a fossiliferous geological formation. Together, the defining index fossil and assemblage could be used to correlate fossil assemblages worldwide. Updates to this system have been published continuously for Triassic LVFs, which remain a heavily-discussed topic in the study of Triassic chronology. Lucas has also defined LVFs for the Permian, Jurassic, and Carboniferous, though these are not as widely used as his Triassic LVFs. Later authors characterized Lucas's LVFs as "interval eubiochrons". This means that they correspond to a segment of time (and strata) between two paleobiological events: the first appearance datum (FAD) of one index taxon and the FAD of another. A first appearance datum is a point in the geological record with the earliest known fossil of a given animal, which can estimate when that animal speciates or evolves into existence. As an example, the Lootsbergian LVF is defined as the period of time between the FAD (estimated speciation) of Lystrosaurus and the FAD (estimated speciation) of Cynognathus. Some taxa which are index fossils for one stage may persist into a later stage.

List of Triassic LVFs LVFs of the Triassic Period from youngest to oldest:

Criticism Several paleontologists have independently questioned the validity of Lucas’s system, criticizing its inconsistent and often contradictory approach to taxonomy and faunal correlations.

Endemic index taxa Many index taxa are very rare or endemic to a single continent, and have no relevance to a global biostratigraphy system. These include Doswellia, Longosuchus, Typothorax, “Pseudopalatus” (Machaeroprosopus), Redondasaurus, and Redondasuchus, among others. For the Berdyankian LVF, very few species are shared between the index assemblage (the Bukobay Formation of Russia) and other correlated assemblages. Direct relationships between Russian, German, and South American dicynodonts are conjectural and based on undiagnostic European fragments.

Imprecise or inaccurate time scales

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Triassic land vertebrate faunachrons

Start with the simplest possible case. Write down what Triassic land vertebrate faunachrons claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth 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 Triassic land vertebrate faunachrons 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 Triassic land vertebrate faunachrons 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 Triassic land vertebrate faunachrons

In research: Triassic land vertebrate faunachrons appears in earth 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 Triassic land vertebrate faunachrons 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: Triassic land vertebrate faunachrons is common in secondary-school and first-year university syllabi. It links to neighbouring topics Biochronology, Regional geologic time scales, Triassic geochronology, so understanding it makes those chapters shorter.
In everyday life: Look for Triassic land vertebrate faunachrons 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 Triassic land vertebrate faunachrons in 20 minutes

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

Frequently asked questions

What is Triassic land vertebrate faunachrons in simple terms?

Why does Triassic land vertebrate faunachrons matter?

Because it connects several earth 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 Triassic land vertebrate faunachrons?

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 Triassic land vertebrate faunachrons.