Welsh Jurassic mammals feeding, new study

This video says about itself:

There Are No Transitional Fossils?

19 April 2011

Long-sought fossil mammal with transitional middle ear found in China.

Palaeontologists have announced the discovery of Liaoconodon hui, a complete fossil mammal from the Mesozoic found in China that includes the long-sought transitional middle ear.

The specimen was found by palaeontologists from the American Museum of Natural History and the Chinese Academy of Sciences.

It shows the bones associated with hearing in mammals, the malleus, incus, and ectotympanic, decoupled from the lower jaw, as had been predicted, but were held in place by an ossified cartilage that rested in a groove on the lower jaw.

People have been looking for this specimen for over 150 years since noticing a puzzling groove on the lower jaw of some early mammals,” Jin Meng, curator in the Division of Palaeontology at the Museum and first author of the paper, said.

“Now we have cartilage with ear bones attached, the first clear paleontological evidence showing relationships between the lower jaw and middle ear,” Meng revealed

The transition from reptiles to mammals has long been an open question, although studies of developing embryos have linked reptilian bones of the lower jaw joint to mammalian middle ear bones.

The new fossil, Liaoconodon hui, fills the gap in knowledge between the basal, early mammaliaforms like Morganucodon, where the middle ear bones are part of the mandible and the definitive middle ear of living and fossil mammals.

Liaoconodon hui is a medium-sized mammal for the Mesozioc (35.7 cm long from nose to tip of tail, or about 14 inches) and dates from 125 to 122 million years.

It is named in part for the bountiful fossil beds in Liaoning, China, where it was found.

The species name, hui, honours palaeontologist Yaoming Hu who graduated from the American Museum of Natural History-supported doctoral program and recently passed away.

The fossil is particularly complete, and its skull was prepared from both dorsal and ventral sides, allowing Meng and colleagues to see that the incus and malleus have detached from the lower jaw to form part of the middle ear.

These bones remain linked to the jaw by the ossified Meckels cartilage that rests in the groove on the lower jaw. The team hypothesizes that in this early mammal, the eardrum was stabilized with the ossified cartilage as a supporting structure.

“Before we did not know the detailed morphology of how the bones of the middle ear detached, or the purpose of the ossified cartilage,” Meng said.

“Liaoconodon hui changes previous interpretations because we now know the detailed morphology of the transitional mammal and can propose that the ossified cartilage is a stabilizer.

“I”ve always dreamed of a fossil with a good ear ossicle. Now, we have had this once in a lifetime discovery,” Meng added.

From the University of Southampton in England:

Jurassic mammals were picky eaters, new study finds

August 20, 2014

Summary:

New analyses of tiny fossil mammals from Glamorgan, South Wales are shedding light on the function and diets of our earliest ancestors, a team reports. Mammals and their immediate ancestors from the Jurassic period (201-145 million years ago) developed new characteristics – such as better hearing and teeth capable of precise chewing.

New analyses of tiny fossil mammals from Glamorgan, South Wales are shedding light on the function and diets of our earliest ancestors, a team including researchers from the University of Southampton report today in the journal Nature. Mammals and their immediate ancestors from the Jurassic period (201-145 million years ago) developed new characteristics — such as better hearing and teeth capable of precise chewing.

By analysing jaw mechanics and fossil teeth, the team were able to determine that two of the earliest shrew-sized mammals, Morganucodon and Kuehneotherium, were not generalised insectivores but had already evolved specialised diets, feeding on distinct types of insects.

Lead author, Dr Pamela Gill of the University of Bristol, said: “None of the fossils of the earliest mammals have the sort of exceptional preservation that includes stomach contents to infer diet, so instead we used a range of new techniques which we applied to our fossil finds of broken jaws and isolated teeth. Our results confirm that the diversification of mammalian species at the time was linked with differences in diet and ecology.”

The team used synchrotron X-rays and CT scanning to reveal in unprecedented detail the internal anatomy of these tiny jaws, which are only 2cm in length. As the jaws are in many pieces, the scans were ‘stitched together’ to make a complete digital reconstruction. Finite element modelling, the same technique used to design hip joints and bridges, was used to perform a computational analysis of the strength of the jaws. This showed that Kuehneotherium and Morganucodon had very different abilities for catching and chewing prey.

Study co-author, Dr Neil Gostling from the University of Southampton, said: “The improvement in CT scanning, both in the instrumentation, at Light Source at the Paul Scherrer Institute in Switzerland where we scanned or even the µ-VIS Centre at Southampton, along with access for research of this kind, allows us to make inroads into understanding the biology and the ecology of animals long dead. The questions asked of the technology do not produce ‘speculation’, rather the results show a clearly defined answer based on direct comparison to living mammals. This would not be possible without the computational techniques we have used here.”

Using an analysis previously carried out on the teeth of present-day, insect-eating bats, the researchers found that the teeth of Morganucodon and Kuehneotherium had very different patterns of microscopic pits and scratches, known as ‘microwear’. This indicated they were eating different things with Morganucodon favouring harder, crunchier food items such as beetles while Kuehneotherium selected softer foods such as scorpion flies which were common at the time.

Team leader, Professor Emily Rayfield from the University of Bristol, added: “This study is important as it shows for the first time that the features that make us unique as mammals, such as having only one set of replacement teeth and a specialised jaw joint and hearing apparatus, were associated with the very earliest mammals beginning to specialise their teeth and jaws to eat different things.”