Tag Archives: science

Identification – Sea urchin fossil

Did you know we identify items for free? Whether it’s a rock from a field or a mystery something from the back of the shed, just bring it in to the Museum and we’ll take care of the rest! (If it’s too big or heavy, just send us an email with a photo).

This piece of flint with a strange marking on it was found in Wethersfield, near Braintree.

The flint nodule has preserved the impression of part of a sea urchin, or echinoid (pronounced ek-in-oid).

The shape you see is the external mould of a single plate of the echinoid’s ‘test’, or shell. When a sea urchin dies or is eaten, the test will often break apart into the individual plates.
Flint is formed from a silica-rich goo which hardens over time, and must have formed on top of this echinoid plate and taken its shape. The plates are made from calcium carbonate and this one will have dissolved away over time, leaving the impression behind.

The shape of the plate suggests it belongs to a species in the genus Cidaris. Saffron Walden Museum has a similar echinoid, Stereocidaris sceptrifera, fossilised in chalk, on display as no. 23 in the How Did They Live display in the geology gallery (below, top). In life, the club-like spines would have been attached to the plates. One of the Museum’s volunteers took this photo of a similar echinoid found at a chalk pit in Grays, Essex (below, bottom).

Fossil in chalk of the extinct sea urchin Stereocidaris sceptrifera, on display in the Museum’s geology gallery. SAFWM : 2020.42.23

The plate in the flint nodule (and the plates in the photos) is an interambulacral plate, which make up most the test of a sea urchin. They fill the space between the ambulacral zones, which are the areas where the urchin’s tube feet pass through the test. Tube feet are used for movement and to exchange oxygen and carbon dioxide with the water for respiration. Sea urchins have 5 ambulacra arranged in a star shape, showing that they are related to starfish.

The Natural History Museum has a good page showing the structure of a sea urchin test: https://www.nhm.ac.uk/our-science/data/echinoid-directory/morphology/regulars/intro.html

The British Geological Survey has an interesting page with good photos of similar fossil echinoids – look out for Temnocidaris (Stereocidaris) sceptrifera about halfway down, and Heterocidaris wickense at the bottom: https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/echinoids/

Another link to the NHM with photos of Stereocidaris fossils: https://www.nhm.ac.uk/our-science/data/echinoid-directory/taxa/taxon.jsp?id=1115

 

 

 

Object of the Month – February 2022

February’s Objects of the Month are minerals with connections to love and relationships, in honour of St Valentine’s Day on 14 February.

4 mineral specimens on a white background. Lines of shade cross the image.

Amethyst geode (top left), sapphire (bottom left), ruby crystals in sheet of mica (middle), lapis lazuli (right).

Amethyst is the birthstone for February, but as a symbol of love, St Valentine is said to have worn an amethyst ring so Christian couples in Ancient Rome could identify him. Valentine was a priest who carried out forbidden Christian marriages and married young couples, when the Roman empire persecuted Christians and preferred their soldiers to be unmarried men.

Lapis lazuli can represent truth and friendship, and in Christianity represents the Virgin Mary. With the blue of the sky and gold of the sun, it represents success in Jewish traditions, while beads found in the ancient town of Bhirrana from 7500 BCE are its oldest known use by people. The remains of Bhirrana are in the Indian state of Haryana.

The deep red colour of high-quality rubies means it is associated with love and passion in modern societies. Throughout history it has been popular in Burma (Myanmar), Hindu culture and China as a protective gem in battle or to secure good fortune when put beneath a building’s foundations. In the UK, it is the traditional gift for a 40th wedding anniversary.

Sapphires are popular for engagement rings, as used for Lady Diana’s engagement ring from Prince Charles. Sapphire is the traditional gift in the UK for a 45th wedding anniversary and can symbolise truth and faithfulness. Ruby and sapphire are actually the same mineral (corundum), with different colours depending on small amounts of other metal atoms included in the crystal. Chromium makes the ruby red, while blue sapphires are coloured by iron and titanium.

Object of the Month – October 2020

New Zealand Kiwi

We’ve been busy over the last few weeks moving the bird taxidermy from a temporary home back to their usual store. October’s object of the month is a mounted kiwi skin, probably of a little spotted kiwi (Apteryx owenii), the smallest of the five kiwi species.

A stuffed Little spotted kiwi sking, facing left, mounted on a 'naturalistic' base.

The little spotted kiwi in Saffron Walden Museum. © SWM

With strong, heavy legs and no wings, kiwis have evolved for life on the ground. They are nocturnal, dig burrows to nest in, and have stiff, hair-like outer feathers to withstand pushing through leaves and twigs. Unlike most birds they have keen hearing and a good sense of smell to help them find food, mostly earthworms and insects.

A page from a book with drawings showing the head, wing and strong feet of a kiwi.

Kiwis have ‘whiskers’ around their beak, stiff feathers and tiny wings, and strong feet for digging.
[Internet Archive Book Images / No restrictions]

Kiwi numbers have plummeted since Europeans arrived in New Zealand, bringing rats, stoats, pigs, cats, dogs, trophy hunting and habitat destruction. Kiwis grow and reproduce slowly and only thrive today on protected reserves, with intensive work to remove these threats. The indigenous Maori regard the kiwi as a taonga (treasure), and actively protect the birds across 230,000 hectares of land, about the same area as the national government’s Department of Conservation. Altogether, an area of land bigger than Essex is managed for kiwi conservation.

Coloured map of New Zealand showing distribution of kiwis at present day and before European colonisation.

Light green, current location of kiwis; Dark green, location of kiwis before European colonisation; Dark grey, kiwis never known here. [© New Zealand Department of Conservation]

Map with numbers and letters showing locations of Little spotted kiwi populations across New Zealand.

Little spotted kiwi reserves – Predator-free islands: 1, Hen Island; 2, Tiritiri Matangi; 3. Red Mercury Island; 4, Motuihe Island; 5, Kapiti Island; 6, Long Island; 7, Anchor Island; 8, Chalky Island
Mainland: A, Shakespear Open Sanctuary; B, Cape Sanctuary; C, Zealandia.
Michal Klajban / CC BY-SA 4.0

See the little spotted kiwi and find out more about kiwi species in our Object of the Month display when the museum re-opens soon.

More information
New Zealand Department of Conservation (DoC) –  Facts about kiwi: https://www.doc.govt.nz/nature/native-animals/birds/birds-a-z/kiwi/facts/
New Zealand DoC – Little Spotted Kiwi: https://www.doc.govt.nz/nature/native-animals/birds/birds-a-z/kiwi/little-spotted-kiwi/
New Zealand DoC – Kiwi: https://www.doc.govt.nz/nature/native-animals/birds/birds-a-z/kiwi/
Science Learning Hub – Conserving our native kiwi: https://www.sciencelearn.org.nz/resources/2784-conserving-our-native-kiwi
WWF New Zealand – Kiwi: https://www.wwf.org.nz/what_we_do/species/kiwi/

References

Internet Archive Book Images. ‘Features of kiwis’ Transactions and proceedings of the New Zealand Institute (1870). Internet Archive Book Images / No restrictions. Available from commons.wikimedia.org [Accessed 29.9.2020]

Michal Klajban. ‘Apteryx owenii – distribution map. CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0). Available from commons.wikimedia.org [Accessed 29.2.2020]

New Zealand Department of Conservation. Kiwi Recovery Plan Summary Document 2018-2028. New Zealand Government, 2018. Available from https://www.doc.govt.nz/nature/native-animals/birds/birds-a-z/kiwi/docs-work/ [Accessed 29.9.2020]

Object of the Month – August 2018

Red squirrel - August object of the month

August’s Object of the Month is a red squirrel. The mammal was chosen as Object of the Month by Sarah Kenyon, Natural Sciences Officer.

This red squirrel was found dead at Saffron Walden, Essex in August 2003. It had been run over by a car in Landscape View. A member of the Uttlesford group of Essex Wildlife Trust gave it to Saffron Walden Museum to be preserved. The body was mounted, or stuffed, by a taxidermist. This red squirrel has russet red fur on its body and tail, with white fur on its chest and belly. Male and female squirrels look identical.

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