Xinpusaurus

Key takeaways

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

Reference excerpt

Xinpusaurus is an extinct genus of thalattosaur from the Late Triassic of Guanling in Guizhou, China. Several species have been named since 2000: the type species X. suni along with the species X. bamaolinensis and X. kohi. A 2013 study proposed that all three species are synonymous with each other, in which case X. suni would be the only valid species, although a 2014 study argued that X. kohi was also valid. A fourth species, X. xingyiensis, was described in 2016.

Description Xinpusaurus is a thalattosaur, a group of triassic marine reptiles with long, paddle-like tails and short legs with independently movable digits. Specifically, it is a member of the group thalattosauroidea, which are characterized by their downturned premaxillae. Xinpusaurus had a short neck, a massive quadrate, and one of the few braincases preserved in thalattosaurs. The lower jaws of this genus show two different forms of dentary-surangular sutures, either a v-shaped suture with the surangular cutting into the dentary from the side (type 1) or an oblique suture with the surangular underlying the dentary (type 2). X. bamaolinensis preserves a type 2 suture while X. kohi has a type 1 suture. X. suni's suture differs between specimens while X. xingyiensis seems to have a type 2 suture. The dentary is also narrow and shorter than the snout, with robust, pointed teeth in the front of its jaws and broad crushing teeth in the back of its jaws, suggesting that it fed on hard-shelled prey, although these adaptations are not as extreme as those of Concavispina, which had exclusively short and blunt teeth. This genus also has a uniquely upward-curving maxilla, a wide proximal end of the humerus, and a radius with a convex lateral edge and concave medial edge. X. bamaolinensis and X. kohi had particularly elongated premaxillae, forming a narrow and pointed rostrum. However, the specimens with the longest snouts are also the smallest in other proportions, so this may be a juvenile trait and cannot be used to distinguish these species from X. suni. X. xingyiensis is the largest species known and is also probably the least advanced, as it does not have a posterior process of the jugal unlike the other species and shares some similarities with the genus Concavispina.

History Xinpusaurus suni was first described by Yin et al. in 2000 based on four specimens: Gmr 010, 011, 012, and 013, with only Gmr 010 (the holotype) receiving an informal description. Other specimens of this species have been found from 2001 to 2002 including GGSr 001 (a well-preserved skull and partial skeleton) IVPP V 11860 (an isolated skull), IVPP V 12673 (a partial skeleton), and IVPP V 14372 (an isolated skull). IVPP V 12673 is the only well described specimen. Xinpusaurus bamaolinensis was described in 2003 from SPCV 30015, a complete skeleton with a well-preserved skull and jaws found in two isolated slabs. These slabs may not represent the same individual, in which case only the front slab can be safely assigned to the genus. Inconsistencies within its description (such as reporting a quadratojugal, a feature unknown in thalattosaurs) have led to some confusion over its diagnosis, and a redescription would be necessary to resolve these issues and determine if it is a valid species or not. Xinpusaurus kohi was described in 2004 from GMPKU 2000/05, an incomplete skeleton. This specimen was also found in two slabs, with the rear slab missing most of the hindlimbs and possibly not belonging to the same individual as the first. In addition, there is evidence that some of the bone structure near the break has been tampered with and that most of the pelvic material has been lost. A 2013 analysis showed that many of the traits initially believed to differentiate X. kohi from X. suni were inaccurate, either due to incomplete data, misidentification, or poor preservation. However, a redescription in 2014 resurrected the legitimacy of the species. This redescription provided additional diagnostic features and argued that the alterations were relatively minimal and that the posterior slab was almost certainly from the same individual as the anterior one. Xinpusaurus xingyiensis was described in 2016 from XNGM WS-53-R3, a nearly complete articulated skeleton from the Zhuganpo member of the Falang formation.

Relationships A phylogenetic analysis of thalattosaurs published in 2013 found Concavispina to be the closest relative of Xinpusaurus. Below is a cladogram based on that analysis:

References

Illustrations

Worked examples

Example 1 — a first encounter with Xinpusaurus

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

In research: Xinpusaurus 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 Xinpusaurus 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: Xinpusaurus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Late Triassic reptiles of Asia, Prehistoric reptile genera, Thalattosauria, so understanding it makes those chapters shorter.
In everyday life: Look for Xinpusaurus 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.

How to study Xinpusaurus in 20 minutes

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

Frequently asked questions

What is Xinpusaurus in simple terms?

Xinpusaurus is an extinct genus of thalattosaur from the Late Triassic of Guanling in Guizhou, China. Several species have been named since 2000: the type species X. suni along with the species X. bamaolinensis and X. kohi.

Why does Xinpusaurus 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 Xinpusaurus?

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 Xinpusaurus.