Jurassic Welsh mammals were picky eaters, study finds

Aug 20, 2014

For most people, mere mention of the word Jurassic conjures up images of huge dinosaurs chomping their way through lush vegetation – and each other. However, mammals and their immediate ancestors were also around in the Jurassic period (201-145 million years ago), albeit as rather less spectacular creatures.

These shrew-sized, early Jurassic mammals were thought to have been confined to the ecological margins, eating whatever insects they could find. However, this was also the time when new mammal characteristics – such as better hearing and capable of precise chewing – were developing. So, if the earliest mammals were all small generalized insectivores, where was the competition driving the evolution of such features?

To answer this question, the researchers studied fossils of these early mammals found in Glamorgan, South Wales which 200 million years ago consisted of a series of small islands in a shallow continental sea.

By analysing jaw mechanics and fossil teeth, the team were able to determine that two of the earliest mammals, Morganucodon and Kuehneotherium, were not generalized 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."

This video is not supported by your browser at this time.
A video of a reconstructed right lower jaw of the Early Jurassic mammal Morganucodon. The reconstruction was made by scanning three partial jaws and "digitally stitching" them together. (Some teeth are missing from the specimens). Credit: Pamela Gill

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.

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.

Professor Mark Purnell of the University of Leicester said: "This is the first time that tooth wear patterns have been used to analyse the diet of mammals this old. That their tooth wear compares so closely to bats that specialise on different kinds of insects gives us really strong evidence that these early mammals were not generalists when it came to diet, but were quite definite in their food choices."

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 beginning to specialise their teeth and jaws to eat different things."

Explore further: How teeth explain the tree of life

More information: Dietary specializations and diversity in feeding ecology of the earliest stem mammals, Nature, dx.doi.org/10.1038/nature13622

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JVK
1 / 5 (2) Aug 20, 2014
Excerpt: 1) "Our results confirm that the diversification of mammalian species at the time was linked with differences in diet and ecology."

The conserved molecular mechanisms that enable this link from ecological variation to nutrient-dependent amino acid substitutions and cell type differentiation manifested in the morphological and behavioral phenotypes of species from microbes to man are detailed in:

Nutrient-dependent/pheromone-controlled adaptive evolution: a model.
http://www.ncbi.n...24693353

Excerpt 2) "... 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."

A Cluster of Olfactory Receptor Genes Linked to Frugivory in Bats http://mbe.oxford...abstract links vitamin C to the de novo Creation of olfactory receptor genes, which links adaptive radiation from nematodes to modern human populations.
animah
5 / 5 (3) Aug 20, 2014
It's simple really: An animal with a teeth configuration that allows it to feed slightly more effectively has statistically more chances of surviving long enough to reproduce than others of the same species. Its offspring resembles it with some variation (like your kids resemble you) including, sometimes, even more adapted teeth and advantages. Rinse, repeat and over time, these changes accumulate into the species' evolution.

It is a strong selector because all animals are particularly vulnerable when feeding, when their eyes are occupied on the food in front of them.

So no Mr. JVK / James V Kohl spammer extraordinaire, this demonstrably has nothing to do with pheromones. Why you continue to deny evolution despite the evidence - especially this type of research is just beyond everyone else on this board.
JVK
1 / 5 (2) Aug 20, 2014
The link below show that teeth are examples of how ecological variation leads to ecological adaptations in species from microbes to man via conserved molecular mechanisms, which I detailed in my model of nutrient-dependent pheromone-controlled ecological adaptations. The model was built from a series of published works beginning in 1995. Most of the published works were peer-reviewed, and two won awards.

Non‐coding RNAs as the bridge between epigenetic mechanisms, lineages and domains of life
http://jp.physoc....abstract
Starvation-Induced Transgenerational Inheritance of Small RNAs in C. elegans
http://www.cell.c...)00806-X
Feeding plasticity in the nematode Pristionchus pacificus is influenced by sex and social context and is linked to developmental speed
http://onlinelibr...abstract
System-wide Rewiring Underlies Behavioral Differences in Predatory and Bacterial-Feeding Nematodes
animah
5 / 5 (2) Aug 20, 2014
published works were peer-reviewed, and two won awards

Many, many published works are used all the time to "justify" the crank theories of presumptuous creationist clowns like you, James V Kohl. You're still a snake oil peddler and a spammer.
JVK
1 / 5 (2) Aug 21, 2014
Our 1996 Hormones and Behavior review article "From Fertilization to Adult Sexual Behavior" is available for free http://www.hawaii...ion.html

See the section on molecular epigenetics "Small intranuclear proteins also participate in generating alternative splicing techniques of pre-mRNA and, by this mechanism, contribute to sexual differentiation in at least two species, Drosophila melanogaster and Caenorhabditis elegans (Adler and Hajduk, 1994; de Bono, Zarkower, and Hodgkin, 1995; Ge, Zuo, and Manley, 1991; Green, 1991; Parkhurst and Meneely, 1994; Wilkins, 1995; Wolfner, 1988). That similar proteins perform functions in humans suggests the possibility that some human sex differences may arise from alternative splicings of otherwise identical genes (p. 337)."

The details of cell type differentiation have not changed and we linked them from species of microbes to man.

JVK
1 / 5 (2) Aug 21, 2014
"Studies on the functional morphology of insect mandibles have identified their ecological relevance [20], including in Orthoptera more generally, where their chewing ability appears to be under selection [21]. Likewise, genitalia are a good proxy for sexual selection [13]; genitalic characters not only show species-level divergence in Amphiacusta but have also been shown to mediate reproductive success in other taxa [13,14]."
http://dx.doi.org...ure13622

This study of mammalian teeth links cell type differentiation from nutrient-dependent sex differences in pheromone production to nutrient-dependent pheromone-controlled morphological and behavioral traits associated with ecological adaptation in the jaw and genitals via an insect model. There are are clear similarities that link what is known about the conserved molecular mechanisms of cell type differentiation via amino acid substitutions in species from microbes to man.

Yet, anonymous fools claim I am making this up.
animah
5 / 5 (2) Aug 22, 2014
This study of mammalian teeth links organ differentiation -partially related to sex differences- to morphological and behavioral traits

Here, fixed that for you.
JVK
1 / 5 (2) Aug 22, 2014
Modelling biological behaviours with the unified modelling language: an immunological case study and critique http://rsif.royal...704.full

There's a model for that: http://f1000.com/.../1089879

Stress-induced mutagenesis and complex adaptation
http://rspb.royal...act?etoc

There is no model for that. Mutated teeth, for example, do not initiate natural selection and the evolution of biodiversity in nematodes. The limited supply of nutrients links ecological variation and starvation to transgenerational epigenetic inheritance of teeth as ecological adaptations that enable more efficient nutrient uptake.

http://www.cell.c...)00806-X
http://linkinghub...12015000
animah
5 / 5 (2) Aug 24, 2014
Word salad clown confuses mammals and nematodes. Priceless!
Vietvet
5 / 5 (2) Aug 24, 2014
Word salad clown confuses mammals and nematodes. Priceless!


And no one is surprised.
JVK
1 / 5 (2) Aug 24, 2014
Advances in Ecological Speciation: an integrative approach
http://dx.doi.org...ec.12616

"....the 'rush to genomes' must not make us lose sight of one of the most important components of ecological speciation: ecology."

http://www.ncbi.n...3960065/
"This model details how chemical ecology drives adaptive evolution via: (1) ecological niche construction, (2) social niche construction, (3) neurogenic niche construction, and (4) socio-cognitive niche construction. This model exemplifies the epigenetic effects of olfactory/pheromonal conditioning, which alters genetically predisposed, nutrient-dependent, hormone-driven mammalian behavior and choices for pheromones that control reproduction..."

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