science

Utatsusaurus

Utatsusaurus is a 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 Utatsusaurus rather than just read about it. In short: Utatsusaurus hataii is the earliest-known ichthyopterygian which lived in the Early Triassic period (c. 245–250 million years ago). It was nearly 2.5–3 metres (8.2–9.8 ft) long with a slender body.

Key takeaways

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

Reference excerpt

Utatsusaurus hataii is the earliest-known ichthyopterygian which lived in the Early Triassic period (c. 245–250 million years ago). It was nearly 2.5–3 metres (8.2–9.8 ft) long with a slender body. The first specimen was found in Utatsu-cho (now part of Minamisanriku-cho), Miyagi Prefecture, Japan. It is the only described species in the genus Utatsusaurus and the only member of the family Utatsusauridae. The name Utatsusaurus was given after the city. The fossils have been found from the Early Triassic Osawa Formation of Miyagi Prefecture, Japan and British Columbia, Canada. Utatsusaurus is one of the most primitive grades of ichthyosaurs, a basal ichthyosaur.

Description

Utatsusaurus was a relatively small ichthyopterygian, measuring 2.5–3 m (8.2–9.8 ft) long and weighing 57.8 kg (127 lb). Unlike the more advanced ichthyosaurs, Utatsusaurus has no dorsal fin and has a broad skull. The snout gently tapers, compared to the more rounded one of more derived ichthyopterygians. The postorbital underlaps the elongate posterior process of the postfrontal. This is an evident plesiomorphic condition for ichthyopterygians. For the size of the skull, the teeth are rather small, and arranged in a primitive groove. They have longitudinal grooves and were first thought to be longer and more acute than Grippia, which is a closely related ichthyosaur. But, after that, it was reported that they were rather bluntly pointed and robust by reexamining the holotype. Utatsusaurus had small fins, with five digits. In addition, those digits have up to five extra finger bones, which is referred to as hyperphalangy. The tail had a long low fin, suggesting that the animal swam by undulation, rather than using its paddles and tail. Utatsusaurus has transitional features between ancestral terrestrial amniotes and the more derived ichthyosaurs. First, the attachment of the pelvic girdle to the vertebral column was probably not robust enough to support the body on land unlike terrestrial amniotes. The pelvic girdle is attached to the vertebral column by the sacral ribs probably articulating with the ilium, but the ribs are not fused to the sacral vertebrae. Second, the humerus and femur of Utatsusaurus has the equal length. While all other ichthyosaurs have the longer humerus, terrestrial amniotes have the longer femur. Furthermore, the hindlimb of Utatsusaurus seems to be larger than the forelimb. They also used phylogenetic analyses and concluded that ichthyosaurs were a member of the Diapsida and the sister group of the Sauria.

Paleobiology Utatsusaurus fed on a diet of fish. It has approximately 40 presacral vertebrae which are cylindrical, suggesting that it probably swam with an eel-like motion.

Classification Ryosuke Motani from the University of California, Berkeley, and Nachio Minoura and Tatsuro Ando from Hokkaido University re-examined the fossils of Utatsusaurus in 1998 using computer imagery to reverse the distortion of the original skeleton. They found that Utatsusaurus was closely related to the lizard-like diapsid reptiles such as Petrolacosaurus, making ichthyopterygians a distant relative to lizards, snakes and crocodiles. They also used phylogenetic analyses and concluded that ichthyosaurs were a member of the Diapsida and the sister group of the Sauria.Additionally, in 2013, Cuthbertson and colleagues from the University of Calgary, Canada, using phylogenetic analyses, reported that Ichthyopterygia is a monophyletic group and Utatsusaurus and Parvinatator are a basal clade. Utatsusaurus in a cladogram after Huang et. al., 2019:

Destruction of the Gyoryū-kan Minamisanriku-cho, Japan is a renowned place which has yielded a number of fossils of ichthyosaurs and the holotype specimen of Utatsusaurus. A museum (called Gyoryū-kan (魚竜館), literally translating as "a house of fish-dragons") was built to keep and display those fossils, and over sixty thousand people had visited there a year. However, on Friday 11 March 2011, the museum was destroyed during the 2011 Tōhoku earthquake and tsunami. At the time of the earthquake, the fossils of Utatsusaurus were kept at another place, and the majority of the other fossils displayed at the museum were salvaged, but the museum, itself has not yet been restored and reopened.

Illustrations

Worked examples

Example 1 — a first encounter with Utatsusaurus

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

In research: Utatsusaurus appears in 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 Utatsusaurus 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: Utatsusaurus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Early Triassic reptiles of Asia, Early Triassic reptiles of North America, Fossil taxa described in 1978, so understanding it makes those chapters shorter.
In everyday life: Look for Utatsusaurus 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 Utatsusaurus in 20 minutes

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

Frequently asked questions

What is Utatsusaurus in simple terms?

Why does Utatsusaurus matter?

Because it connects several 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 Utatsusaurus?

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 Utatsusaurus.