biology

Sanxiasaurus

Sanxiasaurus 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 Sanxiasaurus rather than just read about it. In short: Sanxiasaurus (meaning "Sanxia lizard", after the Three Gorges, Chinese Sanxia, of the Yangtze River) is a genus of neornithischian dinosaur from the Middle Jurassic Xintiangou Formation in the Chongqing Municipality of China. The type and only species is S. modaoxiensis.

Key takeaways

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

Reference excerpt

Sanxiasaurus (meaning "Sanxia lizard", after the Three Gorges, Chinese Sanxia, of the Yangtze River) is a genus of neornithischian dinosaur from the Middle Jurassic Xintiangou Formation in the Chongqing Municipality of China. The type and only species is S. modaoxiensis. The holotype is a partial postcranial skeleton consisting of 55 bones including two cervical vertebrae, 11 dorsal vertebrae, 4 sacral vertebrae, 18 caudal vertebrae, both humeri, radii, and ulnas, partial right ilium, partial right ischium, both femora and tibiae, left fibula, 3 metatarsi and 4 phalanges. In a phylogenetic analysis, it was found to be a basal neornithischian, more derived than Lesothosaurus and less derived than Hexinlusaurus.

History of naming In 2016 a field team from the Chongqing Bureau of Geological and Mineral Resource Exploration and Development discovered a new fossil-bearing bed in the Xintiangou Formation of Laojun Village, Yunyang County. Excavations showed that the bed was rich in fossils with multiple outcrops around Laojun Village with many vertebrate remains found. Among these was 55 bones of a partial skeleton of an early ornithischian from a 5 m (16 ft) exploratory trench, 240 m (790 ft) away from the Fossil Wall of the Lower Shaximiao Formation. The Xintiangou Formation lies between the younger Lower Shaximiao and older Ziliujing Formation, with preliminary Uranium-lead dating giving it an Aalenian to Toarcian age of between 180 and 170 million years ago, during the Middle Jurassic. The ornithischian was the first of its kind from this formation and would be the oldest yet known from Asia. These remains, CLGPR V00003, were described in 2019 as the holotype of the new taxon by Chinese palaeontologist Ning Li and colleagues: Sanxiasaurus modaoxiensis. The genus name refers to Sanxia, the Three Gorges of the Yangtze River that covers the area where the taxon was found, while the species name refers to the Yangtze tributary Modaoxi. Multiple vertebrae, both forelimbs and hindlimbs, and parts of the feet are known.

Classification Upon its description Sanxiasaurus was included in a phylogenetic analysis to assess its relationships to other early ornithischians, where it was found to group between Lesothosaurus and Hexinlusaurus and in a polytomy with Agilisaurus as a member of Neornithischia. Both of the latter genera are also from China, but from the younger Lower Shaximiao Formation making Sanxiasaurus both the oldest and most primitive neornithischian from Asia. Sanxiasaurus was found in a similar position by the analysis of Brazilian palaeontologist André Fonseca and colleagues in 2024, where it was consistently recovered more derived than Agilisaurus and either in a clade with Hexinlusaurus or unresolved, making Agilisaurus the most primitive neornithischian. Their implied-weights results are shown below.

References

Illustrations

Worked examples

Example 1 — a first encounter with Sanxiasaurus

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

In research: Sanxiasaurus 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 Sanxiasaurus 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: Sanxiasaurus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dinosaur genera, Dinosaurs of China, Fossil taxa described in 2019, so understanding it makes those chapters shorter.
In everyday life: Look for Sanxiasaurus 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Sanxiasaurus” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Sanxiasaurus in 20 minutes

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

Frequently asked questions

What is Sanxiasaurus in simple terms?

Why does Sanxiasaurus 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 Sanxiasaurus?

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 Sanxiasaurus.