Collections Up Close
One of the Museum's star objects, Iggy the Iguanadon, has received some new attention recently, being made a part of the University of Cambridge Animal Alphabet Series and our curator Dr David Norman being interviewed by Cambridge TV. For more information click here. and for the interview click here.
In a reversal of Shakespeare’s famous finale to his melancholic monologue on the ‘Seven ages of Man - sans teeth, sans eyes…’ a most ancient fossil, appropriately named Hallucigenia has now been found to possess teeth and eyes, albeit of a primitive kind.
Coloured reconstruction of Hallucigenia showing the head with the newly discovered simple eyes (reconstruction by Danielle Dufault)
The flattened body of a 508 million year-old, 1.5cm long fossil of Hallucigenia is preserved on a rock surface from the Cambrian age Burgess Shale of Canada. A palaeontologist has carefully prepared the specimen to reveal as much detail as possible of the elongate soft body and legs along with the seven pairs of tougher protective spikes on the back and tiny claws at the end of the legs. The head is on the right and a faint trace of the gut can be seen extending along the body. (image courtesy of Jean-Bernard Caron)
In their latest detailed study of the 508 million year old fossil Hallucigenia (published in Nature June, 2015), Dr Martin Smith of the Department of Earth Science and his colleague Dr Jean-Bernard Caron of the Royal Ontario Museum have found some remarkable new anatomical details of the superficially caterpillar-like Hallucigenia. Smith and Caron have spotted microscopic arrays of hard tooth-like structures (10-60 microns in size) in Hallucigenia’s throat and foregut regions along with traces of simple eye-like structures (200 microns wide) on the head.
High magnification electron microscope image of the flattened head of a Hallucigenia specimen seen from above, showing the miniscule eyes, circum-oral ('round-the-mouth') teeth, and pharyngeal ('throat') teeth. Field of view is 1 mm. (image courtesy of Martin R. Smith and Jean-Bernard Caron)
This discovery has far reaching implications for the evolutionary history of a whole group of early arthropod relatives, known collectively as the Ecdysozoa, and especially its earliest history, which until now has been a matter of considerable argument and speculation. The new evidence supports a true evolutionary relationship between the two major groups that comprise the Ecdysozoa – panarthropods, such as the living velvet worms (onychophorans) and water bears (tardigrades), and cycloneuralian worms, such as the living nematodes and priapulids.
A ‘mind bending’ little fossil
Hallucigenia certainly is, as its name suggests, a mind bending little fossil. First discovered in the Cambrian age Burgess Shale deposits of British Columbia just over 100 years ago, it was initially described by the eminent American palaeontologist Charles Walcott as a polychaete worm. Finding new specimens over the intervening years has had scientists puzzled and the strange little beast has been at times turned upside down, back to front and on its side. Finally, Hallucigenia has come to rest and has been assigned to a living group of arthropod-related velvet worms or onychophorans as they are technically known.
From the 100 or so fossil specimens available to them, Martin Smith and Jean-Bernard Caron have also been able to clarify the body form of Hallucigenia. Growing to around 50 mm long, the essentially soft-bodied animal has an elongate tubular form, only 4 mm wide, supported by 7 pairs of legs, each of which ended in tiny claws, along with another 3 pairs of thinner and clawless front appendages. Along the back there was an array of thin sharply pointed and slightly curved spikes (up to 12 mm long) for protection from any would-be predator. Whilst some of Hallucigenia’s recently discovered characters have strengthened its links to the living onychophorans, the discovery of toothlike structures is more problematic as they are not found in the living forms. However similar structures are seen in other living panarthropods and cycloneuralians thus strengthening the evolutionary connection between the two within the larger grouping of the Ecdysozoa. Smith and Caron argue that the absence of toothlike structures in living onychophorans is most likely due to secondary loss over the hundreds of millions of years through which these living fossils have survived.
Apart from its taxonomic transformation over the last 100 years, Hallucigenia could hardly have had a more different lifestyle from its living relatives. From being seabed dwellers in Cambrian times, the onychophorans somehow became landlubbers, living amongst the leaf litter on tropical forest-floors. So far the evidence from the fossil record tells us that of this dramatic ecological shift and move from the seabed to freshwater swampy environments had happened by late Carboniferous times around 300 million years ago.
A display of fossils from the Burgess Shale including images of Hallucigenia is to be seen in the Sedgwick Museum.
Websites: Canada’s Royal Ontario Museum (http://www.rom.on.ca/en) has a website dedicated to the Burgess Shale and its fossils, see http://burgess-shale.rom.on.ca/
Also see http://www.nature.com/nature/index.html
Fortunately, the evidence for seasnakes living 50 miles from London in the Thames Estuary is not something to worry about. The single backbone recently found on the foreshore of the Isle of Sheppey is 50 million years old and was washed out of the local London Clay deposits, which are of Eocene age.
The fossil was found by the Curtin family on a fossil collecting trip to Sheppey, a locality which has been well known for its abundant fossils for over 300 years. A number of specimens from the Isle of Sheppey are held in the 18th century Woodward collection, which forms the basis of the Sedgwick Museum’s fossil holdings.
At present some 500 fossil plant species, dominated by tropical lianas and the mangrove palm Nipa, are known from Sheppey, along with another 350 fossil animal species, ranging from barnacles to birds, from a dog-sized primitive horse called Hyracotherium to turtles and a seasnake. Read more:
The Curtin family’s fossil finds
The Curtins brought two different fossil backbones into the Museum to be identified (see photographs).
The larger (some 40 mm long) and less well preserved of the two can be compared with that of a quite large scombrid fish, a group which includes fast swimming predators such as mackerel, bonito and tuna and was about the size of a tunafish. However, identification of fish species from their backbones is almost impossible and well preserved fossils of teeth jaws and skulls are required. However so many well preserved fossil fish have been found at Sheppey that some 150 fish species have been identified.
(3)The smaller and better preserved backbone (15 mm long) has a distinctive centrum, the main cylindrical articulating bone of the backbone. One end is concave (cotyle) and the other has a domed convex surface (condyle). In contrast fish and aquatic reptiles have concave ends to the centrum.
Our search for the identity of this fossil concentrated initially on fossil turtles, which after fish form the most common vertebrate remains at Sheppey. Turtle neck vertebrae also have a convex dome to the centrum, which helps flex the neck.
The Museum’s Matt Riley compared the Curtins little fossil backbone with turtle vertebrae (4) in the museum collection but could not find any close comparisons. I also double-checked the possible turtle connection with the fossil chelonian expert Professor Richard Moody of Kingston University, who agrees that the backbone does not belong to a turtle.
A seasnake called Palaeophis
Luckily, Matt also spotted some other fossil backbone material (5) amongst the Sedgwick’s abundant Sheppey material which does closely resemble the Curtins’ find. Named as Palaeophis toliapicus, these fossils belong to an extinct snake species, first described in 1841 from Sheppey specimens by the famous 19th century British anatomist Richard Owen.
The Sedgwick Museum specimens of Palaeophis toliapicus include articulated sections of the backbone with ribs, skull parts and toothed jaws. Their anatomy, especially of the backbone, shows adaptations for swimming. This aquatic habit is reinforced by their occurrence in the London Clay alongside numerous marine fossils. However, the additional presence of many land plants and other terrestrial animal remains shows that whilst marine these London Clay deposits were laid down close to the shore under subtropical conditions. The environment was probably similar to that of the modern coastal swamps of South-east Asia.
Giant relatives of Palaeophis
Recently, some backbones from a Moroccan species of Palaeophis have been described, which are larger than those belonging to the living reticulated pythons and green anacondas. These include the largest snakes, which can grow to some 9m in length. A direct size comparison suggests that some Palaeophis species may have been even bigger but there is no indication that any of the Sheppey seasnakes were so gigantic.
The Sedgwick Museum houses an historic collection of London Clay fossils, many of which are on display including a good selection from the Isle of Sheppey.
For a good website display of London Clay fossils from the Isle of Sheppey see www.sheppeyfossils.com
For SSSI notification see: http://www.english-nature.org.uk/citation/citation_photo/1001313.pdf
1.Curtfishvert: A heavily worn fossil backbone from Sheppey found by the Curtin family. Although much of the original detail has been lost, it almost certainly can be identified as the backbone of a large fish and perhaps a member of the scombrid family, which includes the living mackerel and tuna.
2.LondclayFishVert: the fossil backbones of a large fish from the London Clay at Sheppey. Although worn the vertebrae have the relatively simple shape and concave articulating surfaces to the centrum typical of fish backbones.
3.Curt.Pal.jpg: the small and heavily worn fossil backbone discovered by the Curtin Family. The central bony ‘core’ to the backbone is the centrum, whose end surfaces articulate with other backbones. Here we can clearly see the shape of the two articulating surfaces, one has a domed convex surface and the other a concave surface.
4.Turtlevert.: a selection of turtle vertebrae (Argillochelys antiqua) from the London Clay at Sheppey, showing domed centra but with a distinctive wide form.
5. Palvertnod: A stony carbonate nodule full of Palaeophis toliapicus vertebrae and some rib-bones whose length gives some idea of how big this snake was. The distinctive convex domed and concave hollowed articulating surfaces of several centra can be clearly seen.
Meteorite is 'hard drive' from space - by Simon Redfern
University of Cambridge Researchers have decoded ancient recordings from fragments of an asteroid dating back billions of years to the start of the Solar System.
The new picture of metallic core solidification in the asteroid provide clues about the magnetic field and iron-rich core of Earth.
Full press article here