Thursday, 15 October 2015

Oldest Mammal Skin, Hair and Internal Organs.

Spinolestes xenarthrosus, 125 million-year-old remains, found in Cuenca, in what was the Las Hoyas wetland area of central Spain.

Photograph: Georg Oleschinski.
Source: The Guardian.
A Cretaceous eutriconodont and integument evolution in early mammals | Nature.

Like the stunning early bird fossil from Spain which I wrote about a few days ago, another fossil from Spain, this time of an early mammal from about the same period, demands some answers from creationists. Like the bird fossil, this one sheds a lot of light on the early evolution of this order as they diversified from their reptilian ancestors in an environment still dominated by the dinosaurs.

The thing about this fossil, apart from its age, is the amazing detail of the hair, skin and internal organs which has been preserved. The belief is that the body of this small, rat-sized, insect-eating mammal probably ended up in a bog where it became coated with a bacterial sheet soon after death which offered a degree of protection. It extends the earliest fossil record of mammalian skin back 60 million years to 125 million years.

The Mesozoic era (252–66 million years ago), known as the domain of dinosaurs, witnessed a remarkable ecomorphological diversity of early mammals. The key mammalian characteristics originated during this period and were prerequisite for their evolutionary success after extinction of the non-avian dinosaurs 66 million years ago. Many ecomorphotypes familiar to modern mammal fauna evolved independently early in mammalian evolutionary history. Here we report a 125-million-year-old eutriconodontan mammal from Spain with extraordinary preservation of skin and pelage that extends the record of key mammalian integumentary features into the Mesozoic era. The new mammalian specimen exhibits such typical mammalian features as pelage, mane, pinna, and a variety of skin structures: keratinous dermal scutes, protospines composed of hair-like tubules, and compound follicles with primary and secondary hairs. The skin structures of this new Mesozoic mammal encompass the same combination of integumentary features as those evolved independently in other crown Mammalia, with similarly broad structural variations as in extant mammals. Soft tissues in the thorax and abdomen (alveolar lungs and liver) suggest the presence of a muscular diaphragm. The eutriconodont has molariform tooth replacement, ossified Meckel’s cartilage of the middle ear, and specialized xenarthrous articulations of posterior dorsal vertebrae, convergent with extant xenarthran mammals, which strengthened the vertebral column for locomotion.

A Cretaceous eutriconodont and integument evolution in early mammals
Thomas Martin, Jesús Marugán-Lobón, Romain Vullo, Hugo Martín-Abad, Zhe-Xi Luo & Angela D. Buscalioni
Nature 526, 380–384 (15 October 2015) doi:10.1038/nature14905

Copyright © 2015, Rights Managed by Nature Publishing Group. Reprinted with permission under licence #3730151296413

Although the position of internal organs is interesting - liver, the fine structure of lungs, and the diaphragm could all be identified - the really interesting thing about this specimen is that the hair shows evidence of defensive adaptation to form spines and small armadillo-like plates on its lower back. The structure of these spines was very similar to that of existing spiny mammals such as hedgehogs. There was also evidence of a fungal skin infection.

The preservation of its soft parts is stunning. The hairs have the same structure and diversity as those seen on modern mammals.

Thomas Martin,
Professor of Paleontology, University of Bonn
(interviewed by the Guardian).
So, the early mammals were already diversifying and becoming specialised and adapted to their environments 125 million years ago. But, unlike the birds which had moved into a niche not previously exploited by the dinosaurs, these early mammals shared the land with dinosaurs and other reptiles so the available niches and opportunities for rapid diversification were limited.

Once the dinosaurs were exterminated however, like the birds, the warm-blooded mammals which survived the cataclysmic climate change were set to radiate into the terrestrial niches formerly occupied by dinosaurs and to move into the trees and even into water.

But, what creationists need now to address, apart from the obvious problem of explaining a 125 million-year-old mammal fossil on a 6000 year-old Earth, is why, if this mammal's astonishing level of preservation of even soft tissues is because it died in water, why don't we find masses of these well-preserved fossils following the mythical biblical flood which creationists believe killed off what would have been hundreds of millions of individuals of all species, all of which had been created just about a thousand years earlier so would all have co-existed with modern animals?

There should be great beds of these jumbled fossils from all over the world with extinct species such as this one together with modern species, yet what we see is a sorted series of fossils with extinct and more primitive species occupying the older rocks and the modern ones not appearing until we reach the young rocks at the top of the geological column. We also see a geographical distribution of fossils entirely consistent with geographical distribution of species and with plate tectonic evidence.

More importantly, whereas we should expect the level of preservation seen in this mammal fossil to be commonplace if they all drowned, it is, in fact, exceedingly rare.

No doubt a few of the more knowledgeable creationists will point out that, during this mythical flood, their imaginary creator supposed killed every living substance, including the bacteria which could have formed this assumed protective sheet. However, this simply compounds their problem since they will then need to explain why even more fossils from this flood extermination aren't found, since there would have been no bacteria to dispose of the bodies, all of which should then have been preserved in the resulting silt, along with wood and other plant materials. So where is this fossil evidence?

Any creationist brave enough to think about these things and give a considered explanation, or is the infantile superstition to be maintained in the face of contrary evidence and a pathological level of denialism and intellectual dishonesty still?

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