Laosaurus

Key takeaways

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

Reference excerpt

Laosaurus (meaning "stone or fossil lizard") is a genus of neornithischian dinosaur. The type species, Laosaurus celer, was first described by O.C. Marsh in 1878 from remains discovered in the Upper Jurassic (Kimmeridgian) Morrison Formation of Wyoming. The validity of this genus is doubtful because it is based on fragmentary fossils. A second species also from the Morrison Formation, L. gracilis, and a species from the Upper Cretaceous Allison Formation of Alberta, Canada, L. minimus, are also considered dubious.

History and taxonomy Marsh (1878a) named his new genus from vertebrae (YPM 1874) found by Samuel Wendell Williston at Como Bluff, Wyoming, from rocks of the Morrison Formation. The type material includes nine partial and two complete tail vertebral centra, which he concluded came from a "fox-sized" animal. In the same year, he named two other species: L. gracilis, originally based on a back vertebral centrum, a tail vertebral centrum, and part of an ulna; and L. altus, originally based on a pelvis, hindlimb, and tooth (YPM 1876). A review by Peter Galton in 1983 found the type of L. gracilis to consist of thirteen back and eight tail centra, and portions of both hindlimbs. Charles Gilmore had assigned additional remains, including a partial skeleton (CM 11340), to L. gracilis based on size, but Galton transferred the remains to other taxa, assigning the skeleton to Dryosaurus. Marsh returned to the genus in 1894, when additional remains convinced him that L. altus deserved its own genus (Dryosaurus), and that there was another species present: L. consors, based on YPM 1882, a partial skeleton also from Como Bluff. In 1895, he coined the family Laosauridae for his genus, but this was eventually considered synonymous with Hypsilophodontidae.

Charles Gilmore in 1909 assigned a juvenile femur (USNM 5808) to L. gracilis, and in 1925 added partial skeleton CM 11340 to L. gracilis, based on size, but Galton transferred the femur to Othnielia (now Nanosaurus) and the skeleton to Dryosaurus in 1983. Gilmore also described the fifth and final species, L. minimus (species name for its small size), based on NMC 9438, a partial left hindlimb and vertebral bits from the Late Cretaceous (late Campanian) Allison Formation of Alberta, Canada. At the time, though, the discovery locality was thought to be in the Early Cretaceous Blairmore Group, but fieldwork at the L. minimus type locality in the early 1930s showed it to be within the Belly River Group, and Loris Russell published a paper in 1949 recognizing this new geologic information, while finding it generically distinct from Laosaurus proper. Russell found this taxon to be most like Hypsilophodon, from the Early Cretaceous Wessex Formation of southern England. The next major publications which mentioned Laosaurus prominently were by Galton. In 1977, he assigned L. consors and L. gracilis to his new taxon Othnielia rex; and in 1983 he redescribed most of the material and reassigned some of it, as described above. Galton (1983) is also one of the sources for the "Troodon as carnivorous ornithopod" hypothesis of the early 1980s, because it assigns L. minimus to Troodon, based on unpublished evidence. This would tie in with the Orodromeus/Troodon egg confusion of a few years later, which was eventually settled as Troodon individuals eating Orodromeus individuals at their nesting site (the troodontid embryoes were confused with hypsilophodont embryoes). L. celer was assessed as dubious by Galton, a status it has kept through the last major reviews. Two further developments have occurred. First, L. minimus is seen as a possible second species or specimen of Orodromeus (Sues and Norman, 1990), although the remains are too meager to be certain. Second, Galton, in a 2007 review, declared Othnielia rex to be based on undiagnostic remains, and shifted diagnostic referred remains to new taxon Othnielosaurus consors, a new combination based on the original L. consors partial skeleton.

Taxonomic summary L. celer (type species) = dubious ornithischian L. altus = Dryosaurus altus L. consors = Othnielosaurus consors, now considered a junior synonym of Nanosaurus agilis L. gracilis = dubious ornithishian L. minimus = dubious ornithischian, possibly orodromine

References

External links More on the taxonomy of Nanosaurus, Othnielia, and Laosaurus Archived 2021-03-04 at the Wayback Machine, from the Dinosaur Mailing List First page and abstract of Russell, 1949

Illustrations

Worked examples

Example 1 — a first encounter with Laosaurus

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

In research: Laosaurus 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 Laosaurus 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: Laosaurus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dinosaur genera, Dinosaurs of the Morrison Formation, Fossil taxa described in 1878, so understanding it makes those chapters shorter.
In everyday life: Look for Laosaurus 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 Laosaurus in 20 minutes

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

Frequently asked questions

What is Laosaurus in simple terms?

Laosaurus (meaning "stone or fossil lizard") is a genus of neornithischian dinosaur. The type species, Laosaurus celer, was first described by O.C.

Why does Laosaurus 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 Laosaurus?

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 Laosaurus.