Wednesday, 29 July 2015

Five bizarre fossil discoveries that got scientists excited

By Liam Herringshaw

From trilobites to tyrannosaurs, most fossils are of creatures with hard shells or bones. These materials don’t easily biodegrade and sediment has time to build up around them and turn them into a record of the creature that is still with us millions of years after it has died. Soft-bodied organisms like worms, on the other hand, decay rapidly and their fossil record is decidedly patchy.
In exceptional circumstances, however, their remains are preserved and sometimes in the most unusual places. With the right detective skills, palaeontologists can use such discoveries to open up whole new windows on the history of life on Earth. A recent discovery found in 50-million-year-old rocks from Antarctica has yielded a particularly incredible example: fossilised worm sperm.
It’s a great reminder that there are far stranger fossils out there than dinosaur bones. Here are some of the most bizarre specimens ever found.

1. Ancient sperm

A seminal discovery Department of Palaeobiology, Swedish Museum of Natural History

This remarkable find of fossilised spermatozoa from a clitellate or “collared” worm represents the oldest animal sperm ever discovered, beating the previous record holder – springtail sperm found in Baltic amber – by at least ten million years.
The sperm preservation was made possible because such worms reproduce by releasing their eggs and sperm into protective cocoons. In this case, a tough shell kept the cocoons intact until scientists discovered them in shallow marine gravels on the Antarctic Peninsula. Even then, it required high-powered microscopic analysis for the sperm to be spotted.
The sperm most resemble those of a leech-like group of worms that attach themselves to crayfish, even though today these live only in the northern hemisphere. But the researchers think the technique could be applied to other cocoon fossils, and help us learn more about previously cryptic creatures.

2. A well-endowed Silurian shrimp

Old todger?

If 50-million-year-old spermatozoa are surprising, what about a 425-million-year-old penis? Discovered in a ditch near the Anglo-Welsh border in the early 2000s, a tiny ostracod, or seed shrimp, proved to be quite clearly male. Preserved in three-dimensions with all its soft tissues fossilised, it was proportionally well-endowed. “Old Todger” was the headline in the The Sun newspaper.
During the Silurian period (443-419 million years ago), the Welsh borderlands lay on the shelf of a tropical sea. Marine animals were occasionally smothered, entombed and petrified by the ash of distant volcanoes. The ostracod – and countless other small fossils – cannot be seen adequately using microscopes, however, so their mineral tomb has to be gradually ground away and the fossil recreated with 3D digital imaging.

3. Ancient reptile poo and puke

It’s amazing what passes for a fossil. Poozeum/Wikimedia Commons, CC BY-SA

The notion that where there’s muck there’s brass is perhaps best shown by coprolites: petrified dung that can be found in many palaeontological shops. Beyond the novelty, such specimens are “trace fossils” of tremendous palaeoecological value. This means they can tell scientists precisely what an extinct creature was eating.
Coprolites are actually just one element of a richer broth, that of bromalites or “stink rocks”. The term was coined in the early 1990s to encompass all matter of excreta preserved in the rock record, and in the last few years, bromalites have been popping up everywhere.
In Australia, they show that Cretaceous plesiosaurs were bottom feeders. In Poland the regurgitated dinners of shell-crushing fish help us work out how life recovered from the biggest mass extinction in Earth history. And in Jurassic shales from Peterborough and Whitby, pavements of squid-like belemnites have been interpreted as ichthyosaur vomit.

4. Yorkshire rhinos

Buckland in the hyaena’s cave

One very odd fossil discovery was made in Kirkdale Cave, near Kirkbymoorside, North Yorkshire in 1821. Workman quarrying for roadstone found a cliffside hollow full of large animal bones. They were at first thought to be cattle, but a local naturalist saw that they were more exotic-looking, and the remains eventually made their way to Oxford University’s Professor William Buckland.
A man who claimed to have eaten his way through the entire animal kingdom, Buckland was the most marvellous experimental scientist. He recognised that the bones were mainly of large herbivores, such as elephants and rhinos. They showed signs of having been gnawed, and fossilised faeces found on the cave floor resembled those of hyaenas. Conveniently being in possession of one as a pet, Buckland proved Kirkdale Cave had been a hyaena den, and founded the science of palaeoecology. Almost two hundred years on, we know that “African” megafauna roamed the Vale of Pickering about 125,000 years ago, in a warm phase between ice ages.

5. A mystery monster

Slice of history. Ghedoghedo/Wikimedia Commons, CC BY-SA

The fossils of Mazon Creek in Illinois, USA, were first encountered during coal mining in the 19th Century. But it wasn’t until the 1950s that the site became fossiliferously famous, thanks to Francis Tully’s discovery of an exceptionally weird beast: a beautifully preserved soft-bodied animal revealed in a naturally split mineral nodule.
Specimens turned out to be quite abundant but unique to Mazon Creek, and the beast was given the name of Tullimonstrum gregarium. It is now the state fossil of Illinois. Trouble is, no-one knows what Mr Tully’s Common Monster really is. A few inches long, it has a long snout with toothy pincers at the end, two eyes on stalks, a segmented body, and a finned tail. It was probably a predator, and the rocks it was found in suggest that it lived in tropical, shallow seas.
Beyond that, after more than half a century, we’re not much the wiser. It cannot be satisfactorily united with any other invertebrate group, living or extinct. Even with exceptional preservation, the fossil record always has the capacity to surprise.

The Conversation
Liam Herringshaw is Lecturer in Geology & Physical Geography at University of Hull.
This article was originally published on The Conversation. Read the original article.

Wednesday, 15 July 2015

Past climate in the north Atlantic: a new paper on old mud

by Jane Bunting (@DrMJBunting)

Almost twenty-five years ago, in the late Autumn of 1990, I travelled to Orkney with my supervisor Keith Bennett to collect the first sediment cores for my PhD research project. Results from analysis of one of the core sequences have just been published in the journal Quaternary Science Reviews (Whittington et al. 2015 - can be accessed here if you have a subscription, or email/tweet me).  This isn’t quite as bad as it sounds – I published my PhD findings from the site in 1994, focusing on what the pollen preserved in the sediments could tell us about the vegetation history of the islands since the last Ice Age (see here for Michelle's post on pollen analysis) – but rather reflects how long it can take to acquire data and write up collaborative research which is not supported by a single, comprehensive research grant, just by interested academics. 

Location of Orkney in the North Atlantic (bad screengrab from google maps)

Orkney is an archipelago situated to the north of mainland Scotland, and has a hyperoceanic climate (see map left: the google marker shows the location of Crudale Meadow, my study site, on the west of Mainland, the largest island). This means that the environment is very strongly affected by north Atlantic weather systems, and therefore that sediments accumulating in basins on the islands potentially contain a sensitive record of past climate oscillations. This latest paper focuses on the record of past climate, and particularly on abrupt changes in climate, recorded by sediments spanning the period from about 14000 years ago to about 8000 years ago. This covers the end of the last ice age and the beginning of the current warm period. 

Crudale Meadow is today a valley mire, a low point in the landscape supporting a waterlogged plant community of reeds, sedges and other fen species. However, coring down into the sediments showed that this wasn’t always the case. Under about two metres of tough, fibrous peat full of the preserved stems of the reeds and sedges, we found a pale cream-coloured mud, containing obvious fragments of shells. This was lime mud, which forms in shallow lakes and ponds when the water flowing in is alkaline – it’s closely related to the flaky stuff that clogs up kettles in a hard-water area. In Orkney, most former and present lakes deposit acidic muds with minimal carbonate content, but in some places the till left behind by the retreating glaciers contains lumps of chalk, which dissolve in rainwater filtering through the soil, raise its pH, and lead to the formation of lime mud through chemical reactions within the lakes and ponds. 

As a beginner pollen analyst, I was not very fond of those lime muds –they don’t preserve pollen as well as acidic lake muds – but for researchers looking to reconstruct the palaeoclimate of the North Atlantic they were actually very useful. This is because of a process called isotopic fractionation (click on this link for more information about isotopes and climate reconstruction). Oxygen naturally occurs in two forms, one lighter (oxygen-16) and one heavier (oxygen-18), and the ratio between these forms in the water that arrives through rainfall varies according to factors such as the source of the rain and the regional temperature. The carbonate part of the chemical structure of lime muds includes oxygen molecules from the lake water, and therefore locks in a record of the ratio of isotopes in the water. ‘Reading’ this record allows us to reconstruct past temperature, so when towards the end of my PhD I was asked to share my core with a larger team who had the capacity to carry out the analyses, I was interested to see what they’d find. We didn’t realise it would be quite such a long wait…

 The figure below is redrawn from the article, and summarises the reconstructed temperature trends. Looking from left to right, we’re moving back in time. The dashed black line shows a smoothed long term trend and the jagged blue line shows the underlying data. The blue boxes identify periods which are statistically unusually cold, and seem to reflect short-lived climate changes. 
Redrawn from Whittington et al. 2015. Oxygen isotope ratios from Crudale Meadow (see post for details)

Most of these can be found elsewhere in the North Atlantic, in sediment records and even in the Greenland ice cap record, but one is apparently not yet described from other records, and the record is one of the best demonstrations of abrupt events early in the current warm period yet found in Britain. By looking at the remains of molluscs preserved in the alkaline sediments, at the pollen record, and at other sedimentological evidence, we are also able to explore the extent to which these shorter climate episodes affected life in and around the basin.  Climate is the longer-term average of the weather, and in Orkney, you can often literally see changes in the weather blowing in across the sea. Locals say ‘if you don’t like the weather, wait half an hour’ or ‘there is one season a year, but four seasons a day’. Climate records like the one presented in this new paper show long term trends – the proportions of rain and sun, the mean of temperatures over multiple years, the natural variability of the complex and dynamic dance of atmosphere and ocean that creates climate and weather. Twenty five years is roughly equivalent to one sample in the results presented here, even if it seems a long time from a human perspective, or a publishing one!
View from Yesnaby, looking west (photo M. Farrell 2007)

After a long, wet, muddy day in 1990 collecting sediment cores from Crudale, Keith and I drove a mile or so to the nearby cliffs at Yesnaby and ate a very late packed lunch watching the dusk settle over the rolling Atlantic, nothing but ocean between us and north America. At the time I had no idea that there was a record of 6000 years of the climate over that ocean in the core-box, just a hope that there was enough data for a chapter in a PhD. As I write this, a PhD student at Royal Holloway (Rhys Timms) is analysing a new core from another of my PhD sites, Quoyloo Meadow, using the remains of non-biting midges along with other methods to further investigate the climate changes at the end of the last ice age. I wonder what new techniques will have come along by 2040, another 25 years in the future? 

Bunting, M.J 1994.  Vegetation history of Orkney, Scotland: pollen records from two small basins in west Mainland.  New Phytologist 128 771-792
Whittington, G., Edwards, K.J., Zanchetta, G., Keen, D.H., Bunting, M.J., Fallick, A.E. and Bryant, C.L. (2015). Lateglacial and early Holocene climates of the Atlantic margins of Continental Europe: stable isotope, mollusc and pollen studies from Orkney, Scotland. Quaternary Science Reviews 122, 112-130