: Natural History

The eurypterid from Radnor Forest (x1.5)

The reconstruction of the eurypterid from Radnor Forest

The small specimen from the Woolhope district (x3.5). Note that the headshield is displaced to the left.

Numerous specimens are brought in to the Department of Geology every year by the general public for identification. In most cases, these are common fossils or minerals, but from time to time something more unusual turns up, as happened in December 1989 when Mr Stephen Jenkins of Brecon produced a strange-looking fossil that he had found on the side of a forestry road in Radnor Forest.

A large scorpion-like animal

Although it superficially resembled a fish jaw with a series of pointed teeth of different sizes, careful examination led us to dismiss this possibility, and we eventually succeeded in tracking down what it was - half a pincer of an extinct, aquatic, scorpion-like animal called a eurypterid. A remarkable aspect of this specimen is its size - 64mm (2.5 inches) long, which indicates that it belonged to an individual that must have been around 70cm (27 inches) long. The rocks in which it was found in Radnor belong to the Ludlow Series of the Silurian System - about 420 million years old.

Despite their superficial resemblance to scorpions, eurypterids are not closely related to them, although they belong to the same general division of the arthropods - invertebrate animals with jointed legs that include spiders, crabs, lobsters and insects.

Flourishing from about 480 million years ago until their extinction 250 million years ago, most eurypterids are found in rocks that were deposited in fresh or brackish (mix of salt and fresh) water; only a few, including the Radnor Forest specimen, are from rocks of truly marine origin. It is possible, however that the specimen was washed out to sea from shallower waters that lay to the east of Radnor Forest.

Gigantic carnivores of the sea

The pincer belongs to a eurypterid genus named Pterygotus, which was an active swimmer. We can only speculate what might have been its prey, but it probably included primitive fish. The largest known specimens from other parts of the world are almost 3m (10 feet) long, and are the largest arthropods known. The specimen in Amgueddfa Cymru is not quite of those gigantic dimensions! The majority of eurypterids did not reach such a large size.

By coincidence, a short while after the pincer was brought into the Museum, another eurypterid was presented, this time with the 'body' section preserved. It was collected from slightly younger (400 million years old) Silurian rocks exposed near Woolhope (Herefordshire) by Dr. Paul Selden, formerly of Manchester University, and measuring only 0.9cm (0.3 inches) long, it is at the other end of the size scale. This is probably an immature specimen, and the full-grown animal might have been in the region of 10cm (4 inches) long.

Both specimens are now in the Museum collections, thanks to the generosity of their finders. Over the years the general public and academic colleagues have constantly enriched our collections, and donations of this kind remain an important source of material. You never can tell what might be brought in tomorrow...

Few visitors to National Museum Cardiff, and indeed few staff outside the Department of Geology, are aware that the spectacular duckbilled dinosaur Edmontosaurus, is known affectionately as 'Ruth'.

The logo for the Black Hills institute of Geological Research featuring Ruth the duck billed dinosaur from Amgueddfa Cymru

This name would seem to suggest that we know the sex of the 8-metre long specimen, although in fact there is no evidence to determine whether it is a male or female. Such evidence is not often available in fossils of this kind. So why 'Ruth'? The answer is quite simple and without any hidden scientific mysteries. It's because the specimen was found in a quarry in the Black Hills of South Dakota, USA, belonging to Mrs Ruth Mason.

The pet name was first used by the staff of the Black Hills Institute of Geological Research when they were excavating the dinosaur in 1986-7, in recognition of the many kindnesses shown to them by Mrs Mason. Following our purchase of the specimen, we learned very quickly of the name from the people who came over to reconstruct the skeleton for us, and we have continued to use this affectionate name in informal reference to the specimen.

The Black Hills Institute, based in Hill City, South Dakota is one of the leading companies in the world engaged in the collection, preparation and supply of fine quality mineral and fossil specimens, which are particularly attractive to museums for display purposes.

The Edmontosaurus on display in Cardiff is one of the finest examples of a 'duckbilled' dinosaur ever excavated, and was mounted by the Black Hills Institute in a wonderfully life-like pose based on our own particular design requirements. Such is the aesthetic beauty and dynamic realism of the specimen that the Black Hills Institute has incorporated the skeletal drawing into its logo: it forms both a striking image and a fine testament to the skill of the preparators.

From humble beginnings over 65 million years ago, Ruth has now achieved world-wide recognition in promoting the availability of geological display specimens, while also providing a unique experience for all those who visit her at National Museum Cardiff.

The oldest objects in the Museum's collections are 4,500 million year-old meteorites from space. However, the oldest objects from Wales are rock specimens from the Old Radnor district, Powys, which formed about 700 million years ago, when Wales as we know it today had yet to take shape.

Molten rock from Avalonia

These rocks form the three small distinctive conical hills of Hanter, Stanner and Worsel Wood, and are composed of gabbro, dolerite, and granite — igneous rocks that were once molten. When these formed, around 700 million years ago, Wales lay deep in the southern hemisphere. Along with England and parts of Newfoundland, New Brunswick and New England it formed part of the mico-continent Avalonia, which lay on the margin of the vast continent of Gondwana.

At this time Scotland was close to the equator, attached to the North American continent of Laurentia, and it was hundreds of millions of years later that it separated and merged with southern Britain.

Very old rocks are also found in Anglesey and the Lleyn Peninsula, and similar rocks probably underlie the whole of Wales. Typically we only see these ancient rocks where they have been brought to the surface by upward movement along major fault zones.

How do we know that these are the oldest rocks in Wales?

These rocks contain no fossils. So how do we know that those from the Old Radnor district are the oldest, and what age they are? The answer lies in the minerals from which a rock is made, and the chemical elements that these minerals contain.

Radioactive decay

Rocks are aggregates of minerals, which in turn are composed of chemical elements. Many elements occur in different forms, or isotopes, and some of these are naturally unstable and change spontaneously into a different element by the process of radioactive decay. This process provides a natural clock that measures the time that has elapsed since the minerals formed. The clock starts to 'tick' as soon as the mineral crystallises.

By using high precision equipment — a mass spectrometer — the proportion of radioactive decay products can be measured. As these accumulate at a constant rate, we can calculate the time necessary for them to have formed. This is typically many millions of years.

The Stanner-Hanter rocks have been dated using two different sets of isotopes. The decay of rubidium into strontium gave an age of 702 ± 8 million years whereas the uranium-lead system provided a slightly more precise age of 710 ± 1.5 million years.

The oldest rocks in Wales, although 700 million years old, are significantly younger than the oldest rocks found in the British Isles and Europe. These are metamorphic rocks from the Isle of Lewis, Scotland, dated at 3,300 million years old.

The oldest rocks in the world

The oldest dated rocks known in the world are 3,962 million years old, and come from Acasta, north-west Canada. Even these were formed from older, as yet undated, rocks.

Samples of the oldest rocks from Wales, the British Isles and the world can be seen in the Evolution of Wales exhibition at National Museum Cardiff.

A specimen of Paradoxides davidis from Porth-y-rhaw, x 0.75. Amgueddfa Cymru collection

Stage one in the evolution of the north Atlantic area. Triangles indicate areas yielding 'Welsh' trilobites, with dots showing 'North American' forms.

Stage two in the evolution of the north Atlantic area. Triangles indicate areas yielding 'Welsh' trilobites, with dots showing 'North American' forms.

Stage three in the evolution of the north Atlantic area. Triangles indicate areas yielding 'Welsh' trilobites, with dots showing 'North American' forms.

Fossil collecting around the St. David's Peninsula, Pembrokeshire

In 1862 the well-known palaeontologist J W. Salter was collecting fossils in south-west Wales as part of his duties for the British Geological Survey. While examining coastal exposures by boat around the rocky St David's peninsula, Salter one day landed in a small inlet called Porth-y-rhaw, in the mistaken belief that it was Solva Harbour, only a short distance to the east.

His mistake turned out to be extremely lucky, because in the rocks of Porth-y-rhaw, he discovered the remains of one of the largest trilobites ever found (over 50 cm long), and this discovery ensured that the locality became established as a classic and well-known source of fossils.

Life in the sea hundreds of millions of years ago

The dark mudstones exposed there were deposited in an ancient sea some 510 million years ago, during what is now called the Cambrian Period - the name reflecting the fact that rocks of this age were first recognised and named in Wales by the early 19th-century geologists.

Porth-y-rhaw is one of a small number of sites in Wales where Cambrian fossils are reasonably well-preserved and easy to find, and in addition to Salter's giant trilobite it also yields many other kinds of these extinct marine arthropods of more usual dimensions (2-3 cm long).

A National fossil for Wales

The formal scientific name given by Salter to the giant trilobite is Paradoxides davidis, named after his friend David Homfray, an amateur fossil collector from Porth-madog. This trilobite is now one of the best-known from Britain, and is illustrated in numerous publications; choice specimens are among the prize possessions of many of our major museums, including the National Museum of Wales. Indeed, if there were to be a 'national fossil' for Wales, Paradoxides davidis would be the prime contender.

Worldwide Fame

Many specimens of Paradoxides davidis also occur in the Avalon Peninsula of south-east Newfoundland, in rocks of exactly the same age as those exposed in Porth-y-rhaw.

In this context, it is important to understand that in the Cambrian Period, the distribution of continents and oceans was quite different from that of the present day. At that time, Wales, England and south-east Newfoundland all lay on the southern side of an ancient ocean, called Iapetus, and were separated from Scotland and north-west Newfoundland, as shown on the accompanying map.

While the same kinds of trilobites occur in Wales and south-east Newfoundland, quite different ones are common to Scotland and north-west Newfoundland, providing evidence that they once formed parts of different continents.

Snowdon is born

Around 480 million years ago, movements in the Earth's interior caused the ancient Iapetus Ocean to narrow gradually and finally to disappear as two continental masses collided, leading to the formation of a high mountain range of which the Welsh, Scottish, Scandinavian and Appalachian mountains are the present day remnants.

The new Atlantic Ocean

Much later in Earth history, between 200 and 65 million years ago, the two continents began to pull apart again, leading to the formation of a new ocean that was to become the present day Atlantic. However, the new split was not along quite the same line as that along which Iapetus had closed, and left south-east Newfoundland with its 'Welsh' trilobites anchored to the rest of Newfoundland and North America, with Scotland and its 'North American' trilobites attached to the rest of the British Isles.

The occurrence of these same trilobites in areas that today are geographically remote emphasises the need for geologists to study fossils far afield if they are to interpret fully the ancient history of their own local pieces of the Earth's crust.

The oldest objects at Amgueddfa Cymru are in the collections of the Department of Geology. The most familiar are the fossils, ranging in age from approximately 550 million years old down to a little over 10,000 years old.

The Beddgelert meteorite, cut to reveal its internal structure. The dimensions are approximately 9cm x 7cm.

However, there are a group of objects that are considerably older than our most ancient fossils. Unlike fossils, they come not from the Earth, but from outer space.

Many of these extraterrestrial objects fell from space and landed in distant regions of our planet, but one of particular interest was witnessed falling to Earth in north Wales.

Bright lights and shattering slates

In the early hours of 21 September 1949, many people in north Wales and Cheshire saw a brilliant light travelling rapidly across the sky. At 1.45 am a guest at the Prince Llewelyn Hotel, Beddgelert heard a series of dull explosions, followed by three or four seconds' silence, ending with a buzzing sound 'like a light aeroplane' which grew in intensity until a sound of shattering roof slates was heard.

The hotel manager was woken by the barking of his dog, and heard a series of irregularly spaced bangs 'like a naval broadside', but then went back to sleep. The next morning, in an upstairs lounge, his wife found a jagged hole in the ceiling, with plaster and a dark-coloured stone about the size of a cricket ball on the floor. Neither the manager nor his wife knew what this was, nor if it was to do with the sounds heard during the night. However, it was recognised as a meteorite by an old miner in the bar that evening, who had seen some in a museum. A neat, round hole was later found in the slates of the hotel roof.

Meteorites

A meteorite is a natural object that survives its fall to Earth from space. As it passes through the atmosphere the outer layers are heated by friction, causing it to glow brightly and giving rise to the visual phenomena of a shooting star. Meteorites can fall anywhere, at any time, but the chances of being hit by one are (fortunately!) very, very remote indeed.

The Beddgelert meteorite is only the second ever known to come from Wales - the other fell at Pontlyfni, near Caernarfon in 1931. The majority of meteorites probably originate from a cloud of small rocky objects called the Asteroid Belt, which lies between the orbits of the planets Mars and Jupiter in our solar system. Collisions or gravitational forces alter some of their orbits, putting them on a collision course with Earth.

Once found, nearly all meteorites are passed to scientists for examination and analysis, although the Pontlyfni specimen apparently resided under someone's bed for over forty years before being acquired by the Natural History Museum in London!

Both the Beddgelert and Pontlyfni meteorites have been examined by being carefully cut up and distributed between various museums, universities and research institutes. As a result, Amgueddfa Cymru is lucky to have a small piece of the Beddgelert meteorite that fell to Earth in September 1949. This can be seen in the exhibition Evolution of Wales at National Museum Cardiff.

Extraterrestrial rocks older than Earth itself

By dating radioactive isotopes of chemical elements contained in them, the ages of most meteorites, including those from Beddgelert and Pontlyfni, have been determined at approximately 4,560 million years old. This is close to the calculated age of the Earth and the rest of the Solar System. In comparison, the oldest-known rocks formed on the Earth itself are roughly 3,800 million years old (in Wales the oldest rocks are about 700 million years old).

For this reason meteorites are of great scientific interest and importance in studying the earliest history of the Earth and the Solar System, and in giving clues to their primitive condition and how they might have been formed.

One particular class of meteorites (but not Beddgelert), of which there is also an example in the Museum, contains chemicals that were generated with the explosion of huge stars; these include samples of some of the chemical elements that form the 'building blocks' of life, and from which all life - including ourselves - ultimately developed.

Seen a fireball / have you found something which might be a meteorite?

Seen a fireball? Visit:

https://www.ukfall.org.uk/

If you have found something which might be a meteorite, then contact us at: 

https://museum.wales/enquiries/