Keichousaurus
A gorgeous water dragon.
Found only in China, these reptiles were semi-aquatic and flourished in large populations. Scientists visualize thousands swimming in the shallow waters of an intercontinental sea. And while many think these reptiles are only small, some grew quite large.
Figure 1.
An interpreter introduces the fossil of a Keichousaurus which
measures 2.7 meters long and has two horns at a museum in Anshun,
east China's Anhui Province, June 10, 2007.
The Keichousaurs (Kay – Choo – soars) were thought to be able to make their way on land owing to strong limbs (note the robust ulna - outermost bone of the foreleg/forearm).
Figure 2.
Its four legs with fin shaped, semi-flattened hands, five-toed feet, and long digits – along with its strong limbs, powerful hips and shoulders, working in combination with its webbed feet – enabled Keichousaurus to move between land and water.
It probably used its tail for propulsion and legs to paddle, so that in such a beach-like environment, its diet probably consisted of small fish and crustaceans.
Here's a sample of a Keichousaurus hui, similar to the one we have in our collection. Look closely at its shoulder and hip bone groupings; you can see how sturdy it was, able to move in both air and water:
Figure 3.
Private specimen, approx 30cm long. Courtesy of Ken LeBlanc.
Also, look at the figures above. Note that each of these specimens do not show the top of the skull. These reptiles died on their backs, belly up. Because of this, the specimens that show the top of the skull are much move valued.
Here's a drawing that shows its large eye sockets.
Figure 4.
This group of reptiles derives its name from the 1957 location in Keichow Province where they were first discovered. Because of its strong limbs, scientists believe Keichousaurus lived in a marshy environment.
Here's a drawing by Gareth Monger, showing its stocky body, strong limbs, and large, clawed flipper-like feet.
Figure 5.
Keichousaurus were part of a group called the Pachypleurosaurs, believed to have evolved in China, making their way to Europe via the northern border of the Tethys Sea.
Figure 6.
A map of Pangaea, illustrating the Paleo-Tethys sea (Image:
Wikimedia Commons/Kieff)
None of the later European members of the family had the massive limb bones seen in Keichousaurus.
The Keichosaurs were related to their contemporaries the Nothosaurs, and were once grouped with them.
Here's an illustration of a Nothosaur.
Figure 7. Munster is a typical Nothosaur, and is found
most abundantly in the rocks of Southern Germany, although it is
found in other parts of Europe, North Africa, Russia & China.
So, let's take a closer look at the family tree that Keichousaurs were part of.
Side Trip – Where Keichousaurus Fits In
During the Mesozoic Era between 245 to 65 million years ago when dinosaurs dominated the land, the waters of the world were inhabited by an equally spectacular variety of reptiles.
Here's a simple geologic time stamp:
Paleozoic Era - 540 to 250 million years ago (mya)
Mesozoic Era - 251 to 65.5 mya
Triassic Period - 251 to 200 mya
Jurassic Period
Cretaceous Period
Cenozoic Era
Amongst the first fossil vertebrates to be discovered and recognized by scientists, these 'sea-dragons' occurred in all sorts of shapes and sizes.
But perhaps the most unusual of these extinct groups of fascinating prehistoric marine reptiles were the plesiosaurs and their kin.
Figure 8.
Pliosaurids are a family of short-necked plesiosaurs.
Figure 9.
The family Plesiosauridae consists of primitive long-necked
plesiosauroids.
These reptiles are carnivorous, with the most popular and widely recognized being the long-necked plesiosaurs.
They had four large flippers, short tails and barrel shaped bodies. The closely related pliosauroids (often just called 'pliosaurs') had shorter necks and large heads.
However, this large group of reptiles were very diverse, and there are many other interesting forms, such as:
Pachypleurosaurs
Figure 10. Pachypleurosaurs - Keichousaurus hui
Nothosaurs,
and an array of other intermediates.
Figure 11. Nothosaurs
In fact, here's the scientific “family tree” of this
awesome group of ancient reptiles:
Figure 12.
Note that at the top of the tree, is a group called Polycotylidae.
Here's what they looked like:
Figure 13. Polycotylids were believed to be pliosaurs
because of their short necks and large heads, but a number of
detailed analyses have revealed that they are in fact plesiosaurs,
more closely related to the long necked elasmosaurs and cryptoclidids,
than to true pliosaurs.
They had a worldwide distribution in the Cretaceous Period.
So, our Keichousaurus is part of an wide-ranging group of marine reptiles, ones that we wouldn't want to go swimming with, but ones which certainly excite our imaginations and our love of fierce, beautiful animals.
Just The Spec
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Family: Pachypleurisauridae
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Geologic Time: Early Triassic, Spathian Stage (about 242 m.y.a.)
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Size: From mm long (24.5 mm = 1 inch) to meters
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Location: Huxia Formation, Guanglin, Guizhou Province of China
Links
Here's a link to the wikipedia page about Keichousaurus:
http://en.wikipedia.org/wiki/Keichousaurus
Here's a wonder site about Plesiosaurs - The Plesiosaur Directory - one that we are indebted too.
http://www.plesiosauria.com/index.html
Here's another site that covers so much information that its mind bendingly beautiful:
http://universe-review.ca/R10-19-animals.htm
Here's a good reference dictionary:
http://www.lexic.us/
Figures & Acknowledgments
Figures
Figure 1. www.chinadaily.com.cn
Figure 2. www.fossilmall.com
Figure 3. www.plesiosauria.com
Figure 4. www.plesiosauria.com
Figure 5. www.plesiosauria.com
Figure 6. www.palaeos.com
Figure 7. www.palaeos.com
Figure 8. www.plesiosauria.com
Figure 9 www.plesiosauria.com
Figure 10 www.akcollectables.com
Figure 11 www.plesiosauria.com
Figure 12. www.plesiosauria.com
Figure 13. www.plesiosauria.com
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