Beautiful biology illustrations? Don't mind if we do. This 'Top 10' features images from the Biodiversity Heritage Library, an organisation dedicated to making biodiversity literature openly available to everyone.

Polar what?

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Image: Biodiversity Heritage Library

In 1774, German naturalist Johann Christian Daniel von Schreber began writing a multi-volume set of books entitled Die Säugethiere in Abbildungen nach der Natur mit Beschreibungen ('Mammals Illustrated after Nature with Descriptions'). The project featured many animals previously unknown to science – his illustration of a polar bear is considered the first one ever recorded!

Chlorine green

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Image: Biodiversity Heritage Library

This drawing from the Zoological Society of London (published in 1872) portrays two beautifully drawn sloths, though it was the Hoffman's two-toed sloth (shown on the right) and its 'swimmer's green' hairdo that caught the authors' eye as an observation worth noting. We now know the animal's luscious green locks come from colonies of algae that commonly encrust the fur on the head and neck. This provides the sloth with extra camouflage and an easy snack on the go.

Fancy feathers 

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Image: The Biodiversity Heritage Library. Click for detail.

This beautiful bird comes from American zoologist Daniel Giraud Elliot's 1873 work on the birds of paradise. The collection is one of the most prized bird works in history – in 2007 a copy of his book sold at auction for $45,924! Not only does the collection carry a hefty price tag, but also a note of admiration: the work is dedicated to British naturalist and explorer Alfred Russel Wallace, to whom Elliot expresses his indebtedness for uncovering the secrets of so many species. 

Heading in the wong direction 

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Image: The Biodiversity Heritage Library

There's nothing like a good ol' fashioned rivalry to speed up the scientific process ... In a rush to publish his findings ahead of a rival, palaeontologist Edward Drinker Cope made just the tiniest of errors in his reconstruction of the large marine reptile Elasmosaurus: the plesiosaur's head was drawn on the wrong end of its body! Copes allegedly attempted to buy back published copies featuring the cranium catastrophe in a desperate attempt to hide his mistake ... lucky for us, some survived to tell the tale!

And you can tell everyone this is your jelly

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Image: Wikimedia Commons

We couldn't make a natural history list without Ernst Haeckel, now could we? Haeckel's geometric blend of colour and biology inspired artists long after his time (and of course made him the Pinterest superstar we all know and love) ... but who inspired him? This 1904 print features the lion's mane jellyfish Desmonema annasethe (now Cyanea annasethe). It's thought that the species was named after Haeckel's late wife Anna Sethe, because of the similarity between its tentacles and her flowing hair. 

1700s girl power

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Image: The Biodiversity Heritage Library

Maria Sibylla Merian may have been the original 'bug girl.' During her career, she described the life cycles of 186 insect species (especially impressive given how few women were working in science at the time)! Because of her documentation of how "caterpillars produced beautiful butterflies" (the process of metamorphosis) she is now considered among the most significant contributors to the field of entomology. This work also helped overturn the idea held at the time that insects were generated from rotting mud.

Skeletons in the closet

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Image: Wikimedia Commons

Dutch apothecary Albertus Seba's hyrda (1734) was included in a presentation of his curiosities cabinet – a room of 'wonders' (natural history specimens collected throughout his career). Seba doubted the mythical serpent's existence, but firsthand accounts from sailors kept its image fresh in his mind and sketchbook.

For the long haul

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Image: The Biodiversity Heritage Library

In 1876, two men by the names of Frederick Godman and Osbert Salvin began work on the most detailed account of the flora and fauna of Mexico and Central America ever undertaken. It took 36 years to publish the full work, entitled Biologia Centrali-Americana, which described over 50,000 species (over 19,000 of them new) and included over 1,600 printing plates!

Gone forever

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Image: The Biodiversity Heritage Library

Last month marked a century since Martha, the world's last surviving passenger pigeon, died at the Cincinnati Zoo. Passenger pigeons went extinct just 160 years after naturalist Mark Catesby published the first-ever illustration of one.  

Rhino of a different colour 

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Image: The Biodiversity Heritage Library

It seems only fitting to end our list with this incredible image, just as the World Youth Rhino Summit comes to an end. The rhinoceros in the illustration is known as Dürer's rhinoceros. It depicts a woodcut executed by German painter and printmaker Albrecht Dürer in 1515. The image was based on a written description of an Indian rhinoceros that had arrived in Portugal earlier that year. According to lore, the Portuguese king sent the rhino by ship as a gift to the Pope, hoping to gain an ally ... but an unexpected storm sank the ship and the rhino with it. Dürer was commissioned to recreate the mighty beast, but never actually saw it.