biology

Thiornis

Thiornis 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 Thiornis rather than just read about it. In short: Thiornis is a fossil genus of Middle Miocene grebe known from a nearly complete specimen from Libros, Spain. Originally classified as a type of moorhen, Thiornis has since been classified as a species of grebe.

Key takeaways

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

Reference excerpt

Thiornis is a fossil genus of Middle Miocene grebe known from a nearly complete specimen from Libros, Spain. Originally classified as a type of moorhen, Thiornis has since been classified as a species of grebe. The overall anatomy of the bird is identical to modern grebes. It contains a single species, T. sociata.

History The specimen was described by the Spanish Jesuit priest and entomologist Longinos Navás. Despite being of such distinction, Navás had described several vertebrates from the locality. For a while the whereabouts since its description was unknown, but unbeknownst to the scientific community, the slab was on display in the Paris Museum at least since 1930 where it was finally reexamine for a 1995 redescription by American biologist and ornithologist Storrs L. Olson.

Description

The holotype of Thiornis is known from a virtually completed specimen that majority of it consists of postcranial material and even feather impressions (MNHN 1930-1). Parts missing from the bird are the cranial remains, some cervical bones and the toe-bones of the right foot. Based on the dimensional measurement of the bones, Thiornis was closer in size to the horned grebe (Podiceps auritus). The coracoid is similar to genera Tachybaptus and Poliocephalus, as the head does not project as far ventrally as seen in other extant genera of grebes. The furcula is also similar to Tachybaptus and Poliocephalus for the clavicle in lateral view is much less curved, but the shaft is more robust than any of the extant genera. Features in the sternum is identical to modern grebes. The pectoral crest of the humeri is not incised, but rounded and greatly expanded. The shaft of the ulna is also more robust than seen in Podiceps. Wingbones are the same in other grebes being straight, slender and narrower in comparison to other diving birds. The pelvis is compressed laterally, with the posterior portion being broad as the ilia flares outward. The ischia are very long and narrow and extend posteriorly well beyond the sacrum and place oriented towards the point of the ilium. This is another featured that is shared with Tachybaptus and Poliocephalus. The femur is identical in all extant genera except Podilymbus, where the femur of Podilymbus is more slender and elongated. The tibiotarsus is relatively short and wide, a featured shared with Podiceps though in Thiornis the femur has an enlarged cnemial crest. The tarsometatarsus is, however, more similar to the smaller grebe genera like Tachybaptus.

Classification Navás (1922) had initially classified Thiornis as a rallid in the Fulicini tribe with the moorhens, a classification that was supported by subsequent authors until Olson (1995) found the bird to be a grebe instead. While Olson does note the overall similarity between Tachybaptus and Thiornis, postulating there might be some relationship between the two, he recommended classifying the specimen as a species of Podiceps (Podiceps sociatus) due how much larger the specimen is to the extant species of Tachybaptus as well as using Podiceps as placeholder given how morphologically diverse members of Podiceps are. However this view is not supported by other scientists. Storer (2000) argued that the size and dimensions of the bones are not good at determining phylogenetic relationships among grebes alone, thus Thiornis should either be considered a valid genus or at least a species of Tachybaptus. This viewpoint was supported by Ksepka et al. (2013) finding two placements for Thiornis. One being in a massive polytomy with several of the smaller species of grebe and the other being part of a subclade grebes that also includes Tachybaptus and Poliocephalus in a polytomy of their own. Alternatively Fjeldså (2004) treated Thiornis as an ancestral stem-grebe instead.

Paleobiology The holotype specimen was found in Libros, Province of Teruel from the Libros Basin dating to the Vallesian. Despite the age of the fossil, the anatomy of Thiornis suggests an ecology that is not unlike that of those of modern grebes as the group as a whole are homogeneous at the osteological level.

References

Illustrations

Worked examples

Example 1 — a first encounter with Thiornis

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

In research: Thiornis 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 Thiornis 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: Thiornis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Monotypic prehistoric bird genera, Podicipediformes, so understanding it makes those chapters shorter.
In everyday life: Look for Thiornis 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 Thiornis in 20 minutes

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

Frequently asked questions

What is Thiornis in simple terms?

Why does Thiornis 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 Thiornis?

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 Thiornis.