A Unique Window Into Early Animal Life
Soft-tissue fossils are very rare because skin, eyes, guts, and brains are much more difficult to preserve than skeletons. There are only a few deposits worldwide where the mineralogy of the rocks supports the preservation of these soft tissues.
These types of fossils from the Cambrian period give clues about the earliest years of animal life and the largest diversification of life on Earth, called the Cambrian explosion.
A Toast To The Proteins In Dinosaur Bones
Burnt toast and dinosaur bones have a common trait, according to a new, Yale-led study. They both contain chemicals that, under the right conditions, transform original proteins into something new. Its a process that may help researchers understand how soft-tissue cells inside dinosaur bones can survive for hundreds of millions of years.
A research team from Yale, the American Museum of Natural History, the University of Brussels, and the University of Bonn announced the discovery Nov. 9 in the journal Nature Communications.
Fossil soft tissue in dinosaur bones has been a controversial topic among researchers for quite some time. Hard tissues, such as bones, eggs, teeth, and enamel scales, are able to survive fossilization extremely well. Soft tissues, such as blood vessels, cells, and nerves which are stored inside the hard tissue are more delicate and thought to decay rapidly after death. These soft tissues are composed mainly of proteins, which are believed to completely degrade within about four million years.
Yet dinosaur bones are much older, roughly 100 million years old, and they occasionally preserve organic structures similar to cells and blood vessels. Various attempts to resolve this paradox have failed to provide a conclusive answer.
Tissues And Proteins Identified In Dinosaur Bones
These remarks pertain mainly to thigh bones from two dinosaur specimens, a T. rex and a duckbill hadrosaur . In both cases, the fossils had been buried in sandstone and the fossils were analyzed within a relatively short time after excavation, which minimized degradation from sudden exposure to a new set of environmental conditions.
After dissolving away the mineral portion of the bone with weak acid, various types of flexible structures were recovered. They conform to the microscopic pores of the bone in which they had resided, so they are mainly viewed under a microscope. These structures include transparent, branching hollow vessels corresponding to the blood vessels found in modern animals , and also what look like modern osteocyte cells. Various biochemical tests have indicated that these structures are composed of animal protein, showing that they derive from the original dinosaur tissue, as opposed to being merely biofilms produced by microbes which invaded the bone pores.
The proteins which have been identified include collagen, actin, and tubulin. These are known to have structures which are resistant to degradation, especially when they are crosslinked. Tests indicate that these proteins from the dinosaur bones are indeed highly crosslinked, which appears to be a key aspect of their longevity.
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Jellies Combs Sponges And Tentacles
Researchers found that the Qingjiang fossils are in a more pristine condition than those from Burgess Shale and Chengjiang.
This is where the Qingjiang biota is truly remarkable, and certainly worthy of attention, by how it presents its members with amazing detail of shapes, antennas or eyes, Hammarlund said. The rocks are much less weathered than at Chengjiang and less cooked than at Burgess Shale.
As if that wasnt enough, she continued, the biota has also preserved its flimsy ones, so both jellyfish, sometimes even with tentacles, and comb jellies appear preserved. This contribution from the Qingjiang will certainly add to our understanding of the evolution, and resilience, of also the most primitive animals..
Whats more, the biota includes fossils of the same taxa spanning larval, juvenile, and adult developmental stages. This discovery could give an unprecedented look into the development of individual species, the team wrote.
More than a third of the Qingjiang biota are cnidarian fossilsstinging creatures like jellyfish, box jellies, and anemones that are thought to have been abundant during the early Cambrian but are underrepresented in the fossil record.
The array of cnidarians provide the tantalizing prospect of illuminating some of the lowest branches of the animal tree, according to Ross Anderson, a paleobiologist at All Souls College at the University of Oxford in the United Kingdom, who was not involved with this study.
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Explainer: How a fossil forms
Susannah Maidment is a paleontologist at Imperial College London in England. She was part of a team that has just found residues of soft tissue in slivers of eight dinosaur bones. These included a toe claw from a theropod. There also was a rib from a duckbilled dinosaur. All had been found about a century ago, mostly in Alberta, Canada. Since then, the bones had been stashed in drawers at the Natural History Museum in London.
The team used a scanning electron microscope to study the bones. This special microscope can highlight features that are just a few billionths of a meter across. The dinosaur bone images revealed what appeared to be red blood cells. A second type of powerful microscope probed the structure of some bone features. These images showed bands similar to patterns formed by collagen in animal bones today. Collagen is a fibrous protein. It is found not only in bones, but also in cartilage, tendons and other connective tissues.
Those results tell us that there are actual original components of blood and collagen preserved in the fossil bones, Maidment says.
The size of a blood cell can tell scientists a lot. For example, smaller red blood cells indicate its host had a faster metabolism. Faster metabolisms are typical of warm-blooded animals.
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Immunohistochemistry Of T Rex Vessels
T. rex tissues exhibit positive antibody binding to protein components of extant vascular tissue. Are composite images in which fluorescence corresponding to antibody-antigen complexes is overlain upon VLM images of vessel sections, with adjacent images captured using a fluorescent filter. No spurious binding was observed for negative controls in which vessels were exposed to secondary antibodies raised against the host species of all other antibodies used, i.e., mouse and rabbit . Positive binding of dinosaur vessels to actin antibodies can be seen in thin, evenly distributed layers, and more broadly distributed binding is apparent for muscle tropomyosin antibodies. Antibodies to both type I collagen and elastin bind positively to these T. rex vessels. Antibodies raised against ostrich haemoglobin exhibit comparatively lower binding intensity. No reactivity of dinosaur vessels to antibodies against bacterial peptidoglycan was observed.
Investigation Of Possible Crosslinking Mechanisms In T Rex Vessel Structures
We previously demonstrated that the treatment of extant microvascular tissue with haemoglobin, an Fe-coordinating protein, can significantly enhance stability over multi-year time frames, in effect acting as a preserving agent. Here, we extend this experimental observation to propose that enhanced resistance to degradation is due in part to Fe-catalysed non-enzymatic crosslinking of molecules comprising structural tissues, with haemoglobin suggested as the primary source of such Fe in vessels undergoing diagenesis.
Using transmission SR-FTIR, the maximum absorption intensity of the Amide I band of the T. rex tissue was observed at 1657cm1 . Sub-band analysis indicated that this band location was due to increased relative intensities of the triple-helix , and intermolecular , sub-bands, as observed in both samples of crosslinked chicken vessels. The maximum absorption intensity of theT. rex Amide I band fell between the Amide I bands recorded for chicken type I collagen crosslinked using Fenton chemistry and Fe-catalysed glycation , suggesting that both mechanisms could have contributed to post mortem crosslinking in this tissue.
Figure 5Figure 6
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Characterisation Of T Rex Vessel Structures And Evidence For Endogenous Structural Proteins
Three types of vessels were liberated from demineralised T. rex cortical bone , characterised as: extensive, brown-hued, pliable vessel networks , fragmented, opaque structures , and fragmented, semi-translucent structures under visible light microscopy . The pliable vessels were hollow, ranged from 1040µm in width, and demonstrated branching networks consistent in size and morphology with microvascular tissues in extant bone. Energy-dispersive X-ray spectroscopy coupled with scanning electron microscopy and, separately, µ-XRF spectroscopy confirmed that the differences observed in VLM between the soft, transparent and opaque and/or semi-translucent vessels arose from compositional variation between these samples. The opaque vessels were dominated by iron oxide, while the semi-translucent fragments were composed of barium, sulphur, and oxygen. We focused all further analyses on the pliable vessel networks, because they appeared most similar to those observed in extant bone tissue, and thus were presumably less altered.
These combined features are consistent with those seen in extant vessels liberated from cortical bone , and with fibrillar collagen , which shows striations with an accepted d-spacing of 67 nm. Similar features have been observed in vessels and mineralised fibrils recovered from other fossil specimens. Importantly, these vessel networks are too large, and not consistent in morphology, with fungal hyphae.
Neighboring Fossils Different Paleoenvironments
The Qingjiang and Chengjiang biotas are the same age and from the same paleogeographic region but have only an 8% overlap in their taxa. That distinction could suggest that the two deposits developed in response to different paleoenvironmental conditions, the team wrote.
The Qingjiang biota might just be the best yet discovered.
The differences in the biological composition of Qingjiang versus the neighboring Chengjiang biota really highlight the ecological diversity of early animal ecosystems, Anderson said. Burgess Shaletype deposits are of vital importance to our understanding of early animal evolution. The Qingjiang biota might just be the best yet discovered.
With two very different fossil deposits discovered so close together, Zhang and his team continue to hunt for more.
I have been working on Burgess Shaletype fossils for many years and keep searching for good fossil localities and collecting fossils every year, Zhang said. If we can find Burgess Shaletype preservation in the first 20 million years of the Cambrian anywhere in the world, Zhang said, it would be great!
Kimberly M. S. Cartier , Staff Writer
Cartier, K. M. S. , Scientists discover pristine collection of soft-tissue fossils, Eos, 100, . Published on 21 March 2019.
Text © 2019. AGU. CC BY-NC-ND 3.0Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
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Proposed Hypothesis Regarding Mechanisms Of Preservation
Data show that contrary to proposed degradation models , osteocytes may remain intact in extant bone for relatively long post-mortem time periods, without major morphological change. TEM reveals intact cell membranes, organelles and chromatin in osteocytes preserved in untreated bone after 23 years of natural degradation or longer. Likewise, endothelial cell nuclei are identified on intact and aldehyde-fixed vessel surfaces from untreated 14+ year post-mortem specimens . Therefore, for at least a significant initial period, no chemical modification may be required to protect cells, tissues and vessels beyond the intimate association with mineral found in bone .
The vessels and the cells in fossil material might have avoided initial degradative reactions owing to sequestration within bone matrices and protective association with minerals . Additionally, breakdown of haemoglobin and myoglobin after death may have contributed to this initial preservation, as free haem has been shown to inhibit enzymatic degradation and cellular autolysis . However, at some point beyond this initial phase, a mechanism must exist for continued preservation of these labile components. Pending the verification of endogeneity of the cells and the tissues described herein, a hypothesis is presented outlining two possible mechanisms that may combine to facilitate preservation of original organic material.
Scientists Find Soft Tissue In 75
- Original: Jun 16, 2015
In a pile of unpromising dinosaur fossils dug up in Canada a century ago, British scientists find soft tissue materials preserved for some 75 million years.
Unlike bones and teeth, which can survive for hundreds of millions of years, soft tissues are among the first materials to disappear during the fossilization process. Even so, scientists have found intact soft tissue in dinosaur bones before. The most famous case dates to 2005, when Mary Schweitzer of North Carolina State University found collagen fibers in the fossilized leg bone of a Tyrannosaurus rex. But such discoveries are rare, and have previously occurred only with extremely well preserved fossils. The most extraordinary thing about the new find, which scientists from Imperial College London reported this week in the journal Nature Communications, is that the fossils they examined are of relatively poor condition .
As Susannah Maidment, an Imperial paleontologist and one of the lead researchers on the new study, told the Guardian: Its really difficult to get curators to allow you to snap bits off their fossils. The ones we tested are crap, very fragmentary, and they are not the sorts of fossils youd expect to have soft tissue.
Samples of the mineralized collagen fibers extracted by the team.
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Controversial T Rex Soft Tissue Find Finally Explained
The controversial discovery of 68-million-year-old soft tissue from the bones of a Tyrannosaurus rex finally has a physical explanation. According to new research, iron in the dinosaur’s body preserved the tissue before it could decay.
The research, headed by Mary Schweitzer, a molecular paleontologist at North Carolina State University, explains how proteins and possibly even DNA can survive millennia. Schweitzer and her colleagues first raised this question in 2005, when they found the seemingly impossible: soft tissue preserved inside the leg of an adolescent T. rex unearthed in Montana.
“What we found was unusual, because it was still soft and still transparent and still flexible,” Schweitzer told LiveScience.
T. rex tissue?
The find was also controversial, because scientists had thought proteins that make up soft tissue should degrade in less than 1 million years in the best of conditions. In most cases, microbes feast on a dead animal’s soft tissue, destroying it within weeks. The tissue must be something else, perhaps the product of a later bacterial invasion, critics argued.
Then, in 2007, Schweitzer and her colleagues analyzed the chemistry of the T. rex proteins. They found the proteins really did come from dinosaur soft tissue. The tissue was collagen, they reported in the journal Science, and it shared similarities with bird collagen which makes sense, as modern birds evolved from theropod dinosaurs such as T. rex.
Searching for soft tissue
Is Soft Tissue Common In Dinosaur Bones
In early June, an extraordinary paper was published in the journal Nature Communications. The paper is free to read, so I encourage you to take a look at it. The authors of the paper begin by offering a summary of the various discoveries of soft tissue in dinosaur bones. They then make this important point:
Models proposed to account for such preservation indicate that it should be the exception rather than the rule. In particular, it has long been accepted that protein molecules decay in relatively short periods of time and cannot be preserved for longer than 4 million years. Therefore, even in cases where organic material is preserved, it is generally accepted that only parts of original proteins are preserved and that the full tertiary or quaternary structure has been lost.
If you arent familiar with the terms, tertiary and quaternary structure refer to details that determine the three-dimensional shape of a protein, which is very important for its chemical function. Essentially, the authors of the paper are saying that the individual chemicals that make up the protein might still be around after 4 million years or so, but the protein will be highly degraded.
Theyre very scrappy, individual broken bones. I cant even tell you what dinosaur they come from.
What they found in these scrappy bones is surprising, at least if you think they are 75 million years old.
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Specimen Description And Methods
The specimens used in this study range in age from immediately post-mortem to Triassic and derive from multiple environments, different continents and varied taxa, as provided by cooperating colleagues and institutions. Some yielded all four components , and some, few or none of these. For methods, see Appendix A in the electronic supplementary material. For the description of additional specimens not presented in the main text, see table 1 and Appendix B in the electronic supplementary material.
Alternative Hypotheses For Source Of Soft Tissue/cellular Structures
The possibility remains that despite morphological and functional similarity of fossil cell and tissue components to extant material, no original molecular components may remain . The structures may be the result of an as yet unidentified abiotic or geomicrobiological process that could explain their presence in thousand- to million-year-old fossil remains. Therefore, alternatives to the hypothesis that these structures are remnants of the original material are presented below.
The vessels could be composed of kerogen, operationally defined as organic constituents of sedimentary rocks that is neither soluble in aqueous alkaline solvents nor in common organic solvents , or in other words, organic material remaining after dissolution of surrounding material. The relatively high carbon content of these vessels may fit this definition, but vessel carbon is reduced relative to extant material . Additionally, most described kerogen is not transparent or translucent, as are these vessels, and we have found that at least in some cases, the vessels are easily solubilized in some polar solvents, indicating the possible presence of lipids. Because phospholipids are a significant component of cell membranes, further testing may demonstrate an early stage in polymerization.
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