Prehistoric plesiosaur filter-fed like a whale

New research shows that a prehistoric marine reptile fed by filtering small animals out of the water using their long ‘needle-like’ teeth. A team of scientists from South America and the USA re-examined the fossilised skull of the plesiosaur Morturneria seymourensis and uncovered the first known case of filter feeding in a marine reptile. This research has been published in the Journal of Vertebrate Palaeontology.

“This fossil has puzzled me since I first saw it in 1997. The morphology is so bizarre. I couldn’t figure out what the parts were and how they fit together” said the lead researcher Robin O’Keefe.

Morturneria  seymourensis was first described from fossil skull fragments discovered on Seymour Island in Antarctica in the early 1980’s. By referencing new fossil material from closely related plesiosaur species, scientists were finally able to piece the fragments together and reveal how this extinct creature once looked.

Morturneria
Life reconstructions of what Morturneria seymourensis may have looked like. Sculpted by S.J. Godfrey

In doing so they made the surprising discovery that the teeth of Morturneria did not meet end to end like other plesiosaurs. Instead they pointed outwards to form a network of interocking spines.

“I think the teeth really tell the story; they are oriented at such a strange angle. But the angle makes sense if you are dragging the mandible through the sediment… It’s an adaptation for benthic feeding, straining invertebrates from the mud at the bottom,” said O’Keefe.

Unlike other fossil plesiosaurs that had narrow skulls Morturneria had rounded ‘hoop-like’ jaws that hinged far back at the base of the skull. This combined with an arched palate meant that the oral cavity of Morturneria could filter large amounts of water.

“The oral cavity is big, particularly in comparison with other elasmosaurs… We can’t make a quantitative estimate because we don’t know how stretchy the floor of the mouth was,” said O’Keefe.

Furthermore, the structure of Morturneria’s snout have lead researchers to think that it could have closed off its nostrils with a small muscular valve, thus allowing them to push water forwards through their delicate teeth to filter out food particles.

A similar method is used by modern day crabeater seals (Lobodon carcinophaga) whose specialised lobed-teeth form a sieve-like network. Whilst crabeater seals can still use their jaws to tackle bigger prey, such as fish and squid, most of their diet consists of small crustaceans filtered out of the water with their teeth.

crabeater-seal-541832_1920
Crabeater seal (Lobodon carcinophaga). Image: Pixabay

Despite being reliant on small food items, filter feeding is such an effective feeding method that is sustains the largest animals to have ever existed on our planet. Whales feed by filtering krill out of the water using large ‘baleen’ plates that hang from their upper jaws.

Morturneria probably also relied on small crustaceans as a major food source. The researchers found that the Morturneria skull shares similar features with modern day grey whales (Eschrichtius robustus), such as an arched palate with a midline-keel, showing a remarkable case of convergent evolution between these two unrelated animals.

Morturneria  seymourensis existed over 66 million years ago during the Late Cretaceous period. The researchers believe that these fossil fragments are from a juvenile and ongoing research on additional Mortuneria fossil fragments will allow researchers to estimate how big these creatures could have been.

Dr Robin O’Keefe is an Associate Professor at Marshall University, West Virginia, USA.

 


IMG_8491Article by James O’Hanlon

James is a research scientist and science communicator currently based at the University of New England, Armidale. He hosts the In Situ Science podcast and is sick of hearing people say bad things about spiders.

Advertisements

Democracy: It’s for the dogs

An international team of researchers has uncovered that African wild dogs behave in an unusual way: voting by sneezing to determine when the pack is ready to move out for the hunt.

While it is common for certain animals to reach a consensus before partaking in a particular activity, the fact that the dogs used sneezing to vote and that not all votes are equal within the pack are both unique aspects to the dogs’ behaviour.

Research such as this into communication methods amongst African wild dogs may play a larger role in conservation management as well as offering some exciting pure research outcomes in general.

The research group, which consisted of Dr Neil Jordan, Reena Walker and Dr Andrew King, recorded details of 68 social rallies from five African wild dog packs living in the Okavango Delta in Botswana. Their results have been published in the Proceedings of the Royal Society B.

Jordan noticed that African wild dogs performed energetic greeting ceremonies called ‘social rallies’ after rest periods before moving off to hunt again.

“I wanted to better understand this collective behaviour, and noticed the dogs were sneezing while preparing to go.”

Jordan said at first he couldn’t quite believe what the analyses revealed.

“The more sneezes that occurred, the more likely it was that the pack moved off and started hunting. The sneeze acts like a type of voting system.”

He speculated that the dogs originally sneezed to clear the airways prior to departure and that the action became a reliable sign of this intent.

The findings identified a further twist: that the dominant pair’s votes had more weight amongst the group, Walker said.

“We found that when the dominant male and female were involved in the rally, the pack only had to sneeze a few times before they would move off.

“However, if the dominant pair were not engaged, more sneezes were needed – approximately 10 – before the pack would move off.”

King said that while quorums are used by other social carnivores such as meerkats, the finding that each dog’s vote was not equal made this example more unusual.

Meerkats were important in the context of the wild dog study because they also have vocal mechanisms underlying their quorum decisions, he added.

“They call to indicate they are about to move and when enough of them have called they move. So, one behaviour (calling) is used as a signal or cue regarding the other behaviour (moving). The dogs do something similar with their sneezes.”

Andrew King 1
African wild dog Lycaon pictus. Copyright: Andrew King

Quorums may be widespread because they produce a consensus quickly, he said. Aside from vertebrates, social such as ants and bees also use quorums as do certain types of bacteria.

“In the case of bees, which dance to direct one another to new sites – once the number of bees at a site reaches a quorum the bees begin an additional recruitment strategy to dancing, known as piping. Many species of bacteria also use quorums to coordinate gene expression according to the density of their local population.”

Jordan said that while the sample size of five African wild dog packs was already “pretty good,” there was still a lot to learn in terms of their communication in general.

“We are working with the Botswana Predator Conservation Trust here and a major part of our collective work is in studying carnivore communication and attempting to apply this knowledge in conservation management.

“Getting a deeper understanding of how they communicate opens up the potential for us to direct their movements or behaviour for conservation benefit, for example by deterring them from entering farmland or from killing livestock when they are there.”

Dr Neil Jordan is a research fellow at the Centre for Ecosystem Science, University of New South Wales and Taronga Conservation Society Australia, Reena Walker was an undergraduate research technician at Brown University in the US at the time of the research and Dr Andrew King is an associate professor at Swansea University in the UK.

The study was conducted with assistance from the Botswana Predator Conservation Trust which received grants from Wild Entrust International, Tusk Trust and various private donors.


Miklos
Article by Miklos Bolza
Miklos Bolza graduated with an honours degree in science from UNSW (majoring in maths and physics), now works as a freelance science journalist, and can’t wait until space tourism really ramps up

Life vs Science

Life vs Science: Live Podcast Recording

When: Wednesday, 16th of August, 7pm

Where: Camelot Lounge, Railway Parade, Marrickville NSW

Bookings Online Now!

It is the searing agony you feel when you find inaccuracies in science fiction movies. It is checking your pedometer hourly, not because you have to, but because you want to. Being a scientist is not just a profession, it is a way of life.

Join us in celebrating the Sydney Science Festival with a live podcast recording.  A panel of Sydney scientists and podcasters will take us on a comedic journey through the passions and pitfalls a life in science. It will cover important topics such as the imminent uprising of introverts, and why you shouldn’t refer to your first born as a ‘pilot study’ in public.

Featuring Shane Hengst (UNSW, STEMpunk), Leigh Nicholson (USyd), Alice Williamson (USyd, Dear Science) and James O’Hanlon (UNE, In Situ Science).

Book online now!

Keep up to date by liking the In Situ Science Facebook page.

SSF17_Logo_Colour_CMYK