A skeleton left behind

Leaf Tail Gecko

© University Museum of Zoology, Cambridge 2013

© University Museum of Zoology, Cambridge 2013

Ann Charlton, Senior Museum Technician and Archivist at the Museum of Zoology, writes of the preparation of this tiny skeleton:

Skeletonisation depends on the condition of specimens. A method for small specimens such as birds and mammals: ‘Unzipped Pyjama Pelts’. First glove up. Gently lay your specimen on its back face up. Stroke a scalpel blade gently from under the chin of the specimen to just below the stomach. This separates the specimen pelt so a thin pink inner skin is found underneath. Scalpel down. Feel under the pink skin by pushing your gloved fingers between the skin and the flesh underneath. Work your way around the specimen so you begin to feel its whole body form along up and under its back. With practice you are able to turn the skin pelt inside out as the body comes away from the pelt. Cut the pelt at the ends of hands, feet and nose if you can manage pull the pelt over the head. That’s unzipped pyjamas, pink specimen in its birthday suit! The art and skill is to do this in one piece!

So I introduce you to Leaf Tail Gecko (Uroplatus aff.ebenaui), an exquisite, perfectly formed juvenile that died in captivity. Measuring 29.8mm in length, the Leaf Tail Gecko was a tiny juvenile with huge staring eyes and soft bones. The outstretched blobby fingers made all four feet look too big for boots and body! Appearance: skin almost transparent, dry, brown in colour with no imperfections, a challenging specimen if ever I saw one. There was one major problem: this tiny specimen could not be ‘unzipped from pyjamas’ to reveal its bones.

Solution: Microsurgery. Microscope, tweezers, pins,foam, dish and spray bottle were the instruments used. Assorted paint brushes, cotton wool buds and warm water finished the job. I pinned the Leaf Tail Gecko onto foam, using microscope to see. Ensured pins did not damage bones as gecko was fastened down. Filled dish to top with warm water to immerse gecko. Immersion ensured gecko floated upside down under the water. Left for 2 days. The water rehydrated the skin. Took the gecko from the water and placed onto a tray under the microscope. Skin was loose, bloated and the opaque bones were showing through. Carefully tweezered skin away from flesh working along from the head down to top of pelvis. Left skin on tail and blobby feet and toes. Lifted muscle bundles away from skeleton with tweezers. When small bones began to show, changed to a small, stiff paint brush. Flesh was glided carefully off the bones. Cotton wool bud cleaned moisture and remaining flesh from skeleton. Cut end off cotton wool buds, which were tubular and carefully cleaned out brain cavity and eye sockets. Skeletal specimen sprayed with warm water, left to air dry for two days. Skin shrunk and split around tail, feet and blobby toes. Lifted dried skin off feet with soft paint brush. Re-wet skin with soft paintbrush to remove remainder until skeleton appeared. Skeletal gecko left on foam with minimal pins and places into clear box. A beautiful skeleton left behind to add to the collection.

Heterodontosaurus tucki, the “different toothed lizard”

Heterodontosaurus

image by Dr Laura Porro

Dr Laura Porro, postdoctoral researcher, writes:

Dinosaurs capture our imaginations for many reasons: they dominated life on Earth for an extraordinary 130 million years; they evolved body shapes and lifestyles unlike those of any living animal; and some grew to immense sizes, including the largest creatures to ever walk on land.

Not all dinosaurs were enormous, however. Scurrying among the feet of such giants as Diplodocus and Stegosaurus was a cast of tiny dinosaurs. One such group was the heterodontosaurs, which form one aspect of my research.

Little known outside scientific circles, these dinosaurs were found in Africa, Asia, Europe, and North and South America. They lived from the Late Triassic until the Early Cretaceous – more than 80 million years. The largest species, Heterodontosaurus, grew only as big as a fox while the smallest species weighed less than a gray squirrel even when fully grown.

Heterodontosaurs are fascinating animals. Their name means “different toothed lizards”. Heterodontosaurs have a beak and flat, incisor-like teeth for nipping at the front of their mouths; behind these are long, sharp caniniform teeth; at the back of their jaws are large, molar-like teeth. These differently-shaped teeth are common in mammals (including humans) but unusual among lizards, crocodiles and other dinosaurs.

What did heterodontosaurs eat? Close examination of their teeth reveals heavy wear as in modern herbivores. Computer modeling of the Heterodontosaurus skull and jaw muscles have shown that it used complex jaw movements to chew food, again similar to living plant-eaters. However, the knife-like canine teeth and large, sharp claws on the hand of Heterodontosaurus resemble those of meat-eating dinosaurs. Many palaeontologists think that heterodontosaurs were omnivorous, feeding mostly on plants but occasionally eating insects or small vertebrates.

Heterodontosaurs are surprising for reasons other than their teeth. Since the mid-1990s, palaeontologists have discovered numerous dinosaurs with preserved feathers. Nearly all of these have been theropods, meat-eating dinosaurs such as Velociraptor and T. rex. Living birds evolved from theropods, and it was thought that only these carnivores possessed feathers. But the 2010 discovery of Tianyulong, a heterodontosaur from China, stunned scientists: the back, neck and tail of Tianyulong sported rows of long, primitive feathers. Tianyulong is only distantly related to birds, and the presence of feathers in this animal suggests that many plant-eating dinosaurs may have been rather ‘fuzzy’ as well!

image by Li Da Xing

Studying heterodontosaurs can be challenging. The delicate nature of such tiny bones means that specimens are often damaged during fossilization; preparing these fossils using traditional tools (such as drills, brushes or acids) risks further damage. In 2010, my colleagues and I described the heterodontosaur Fruitadens, the smallest adult dinosaur known from North America. I CT-scanned the specimen and then used computer software to ‘digitally’ prepare the specimen, producing detailed 3D models of the bones, teeth and even internal structures like blood vessels!

fruitadens

During our visits to museums, zoos and wild places we are awed by animal giants—looming tyrannosaurs, trumpeting elephants, and icons of conservation such as the tiger, whale and giant panda. These animals are magnificent, indeed, but it is also important to consider some of the tiny wonders of evolution—both extinct animals like Heterodontosaurus worthy of study and living creatures worthy of conservation.