Level 1 — Absolute Beginner
Scientists find a new animal from the time of the dinosaurs. It is a small mammal. It lived in China about 125 million years ago.
The animal swam in water. Its hands and feet were like the feet of a platypus. A platypus is an animal from Australia.
The animal also grew new teeth many times. Most mammals grow teeth only two times.
The scientists call it Dongoconodon platycauda. It was about the size of a water vole.
- mammal
- an animal that feeds its babies with milk
- dinosaur
- a very large animal that lived long ago
- platypus
- an Australian animal with a flat bill and webbed feet
- swim
- to move through water
- tooth
- a hard white part in the mouth
- fossil
- the old remains of an animal in rock
- scientist
- a person who studies nature
- China
- a big country in Asia
Level 2 — Elementary
Scientists have described a small mammal that lived alongside the dinosaurs about 125 million years ago. It was found in Liaoning province in northeastern China. Its name is Dongoconodon platycauda.
The animal was about the size of a water vole and weighed between 115 and 190 grams. Its hands and feet were flat and long, with small ridges on the finger bones where webbing could attach, just like on a platypus.
It also had a wide tail like a coypu, a water rodent. The tail probably helped it steer and stay stable in the water.
CT scans of the nearly complete skeleton showed something else. The animal replaced its teeth many times, with up to three sets in some places. Most modern mammals grow only two sets. The study was published in Nature Communications.
- province
- a large region of a country
- webbing
- skin between the toes that helps an animal swim
- rodent
- a small gnawing animal such as a rat
- skeleton
- all the bones of a body
- CT scan
- a special X-ray that shows the inside of something
- steer
- to control the direction of movement
- stable
- steady and not easily tipped over
- describe
- to give a full scientific account of something new
Level 3 — Intermediate
A fossil from the Early Cretaceous of northeastern China has revealed the earliest confirmed swimming mammal of its kind. Described in Nature Communications as Dongoconodon platycauda, the animal lived about 125 million years ago and was roughly the size of a water vole, weighing an estimated 115 to 190 grams.
Its limbs give it away. The hand and foot bones are flattened and elongated, and small flanges on the finger bones match the places where webbing attaches in the modern platypus. A broad tail, comparable to that of the coypu, probably worked as a rudder, giving the animal a combination of paddling feet and a steering tail not seen before in the fossil record.
The skeleton, collected in 2016 at the Changzigou locality of the Jiufotang Formation in Liaoning, is nearly complete, with a well preserved skull. CT scans exposed teeth at several stages of growth, including replacement teeth beneath other replacements. At some positions there were three generations of teeth across all four tooth types.
The finding suggests that early mammals experimented with lifestyles that are surprisingly familiar today, and that repeated tooth replacement, now rare in mammals, was once more common.
- confirmed
- proved to be true
- elongated
- made longer than normal
- flange
- a flat rim that sticks out from a bone or object
- rudder
- a flat part used to steer a boat
- locality
- a particular place where something is found
- generation
- one set in a series of repeated replacements
- experiment
- to try new things to see what works
- fossil record
- the history of life shown by preserved remains
Level 4 — Advanced
A near complete skeleton from the Early Cretaceous of northeastern China has given palaeontologists the earliest confirmed mammal built for swimming in this lineage. Described in Nature Communications as Dongoconodon platycauda, the creature lived roughly 125 million years ago, was comparable in size to a water vole, and weighed an estimated 115 to 190 grams.
Its anatomy is a mosaic of familiar adaptations. The hand and foot bones are flattened and elongated, and small flanges on the phalanges coincide with the sites where webbing attaches in the modern platypus. A broad tail akin to that of a coypu would have served as a rudder, an assemblage of propulsion and steering that has not previously been documented in the fossil record.
The specimen, excavated in 2016 at Changzigou in the Jiufotang Formation of Liaoning, preserves a well articulated skull and jaws. Computed tomography exposed teeth in several stages of eruption and development, including replacements beneath replacements, with up to three tooth generations at certain positions across incisors, canines, premolar-like and molar-like teeth.
That last detail is the provocative one. Most living mammals are diphyodont, replacing their teeth only once, and the authors' description of this animal as polyphyodont underlines how varied early mammals were, and how much remains to be learned from the Jehol fossil beds.
- palaeontologist
- a scientist who studies ancient life through fossils
- lineage
- a line of descent from a common ancestor
- mosaic
- a combination of many different elements
- phalanges
- the small bones of the fingers and toes
- assemblage
- a collection of things gathered together
- diphyodont
- having two sets of teeth in a lifetime
- polyphyodont
- having many sets of teeth in a lifetime
- provocative
- likely to cause interest or debate
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