SVP meeting abstracts by Mary Schweitzer's lab...

[David Marjanovic <david.marjanovic@gmx.at>]

...on soft-tissue preservation inside Late Cretaceous bones.

Timothy Cleland & Mary Schweitzer (2008): Preliminary investigation of 
microscopic integrity and molecular preservation in newly excavated 
dinosaurs, Journal of Vertebrate Paleontology 28 (supplement to issue 3), 
64A

"Soft tissue has been recovered from [L]ate Cretaceous dinosaurs of Montana, 
indicating the presence of a depositional facies conducive to preserving 
organic material on the molecular level. The mode of preservation is 
unknown; however, iron-induced crosslinking has been proposed as a possible 
mechanism for preservation of these components. To test the hypothesis that 
iron is part of the chemical pathway of preservation of these tissues that 
may be responsible for the persistence of these soft tissues, additional 
dinosaur bony elements were collected without preservatives, using a field 
collection protocol designed to reduce chances of contamination or artifact. 
These specimens were demineralized within days of collection to verify the 
presence of soft tissues, and either embedded and sectioned, or chemically 
extracted, then subjected to multiple analyses to characterize these 
components. Histochemical [analysis?] and immunostaining were performed to 
detect and identify remnant endogenous organics preserved within the soft 
tissues. The sections were examined using analytical transmission electron 
microscopy (TEM) to determine the presence and elemental compositions of 
high-density minerals associated with the preserved tissues. The 
microstructures preserved within the dinosaur were then chemically compared 
to extant ostrich vessels derived from long bone elements. The vessels were 
incubated in a concentrated solution of hemoglobin, as a proxy for naturally 
occurring processes proposed to occur during death and degradation. 
Comparing the chemical changes in ostrich vessel[s], including resultant 
mineral precipitation in vessel walls, provides a model for early diagenetic 
chemical pathways that may have assisted in the preservation of dinosaur 
soft tissue structure. Developing testable models of rates and processes 
that may result in the preservation of cells and vessels is critical because 
current understanding of fossilization and/or degradation does not allow for 
the persistence of these soft tissue structures across geological time."

Elizabeth Johnson & Mary Schweitzer (2008): The microbial role in early 
diagenetic mineralization of vertebrate soft tissue within bone, Journal of 
Vertebrate Paleontology 28 (supplement to issue 3), 97A

"Microbial processes assist in preserving soft tissues by inducing anoxia, 
chemically altering the pH of local microenvironments, and acting as passive 
nucleation sites through either cell bodies or biofilm secretions to induce 
mineral precipitation. These microbially mediated processes greatly increase 
the rate of mineral precipitation compared to abiotic conditions, and 
therefore, [sic] may play a role in early diagenetic mineralization 
correlated with exceptional preservation. Here, we report the results of 
actualistic experiments designed to test the hypothesis that microbes play 
an important role in early diagenesis to preserve vertebrate remains. Extant 
chicken tibiae were de-fleshed and either chemically degreased (simulating 
pre-burial exposure) or untreated (simulating rapid burial). Bones were 
subsequently buried in pure quartz, medium grained sand and allowed to 
degrade for approximately four weeks. This process resulted in differential 
sand cementation directly adjacent to bone fragments. Cemented and 
unconsolidated sediments were examined for authigenic minerals and microbial 
biomarkers, supporting the hypothesis of microbial involvement in early 
diagenesis and forming the basis for a predictive model for vertebrate bone 
entrance into the fossil record. To test this model, we examined sediments 
associated with dinosaur remains from which soft tissues (vessels and cells) 
were recovered. Scanning electron microscopy (SEM) was used to test for the 
presence of microbial morphotypes in sediments, and X-ray diffraction (XRD) 
was used to identify authigenic mineral phases in sandstone cements and/or 
microbial bodies to verify these were mineralized, and not recent 
contaminants. Finally, chemical extracts of sediments surrounding 
exceptionally preserved dinosaur bones were examined by mass spectrometry 
for the presence of muramic acid, a biochemical fingerprint of microbes [ = 
bacteria and archaea], and other biomarkers to verify the role of microbes 
in early cementation resulting in exceptional preservation."

Mary Schweitzer, Chris Organ, Zheng Wenxia, John Asara & Timothy Cleland 
(2008): Exceptional preservation of *Brachylophosaurus canadensis* 
(Campanian, Judith River Formation, USA), Journal of Vertebrate Paleontology 
28 (supplement to issue 3), 139A

"The presence of apparently original soft tissues in demineralized 
*Tyrannosaurus rex* bone (MOR 1125) was unexpected. We demonstrated the 
persistence of these components (transparent vessel-like structures, two 
populations of cell-like microstruc[t]ures, and flexible, fibrous matrix) in 
a variety of fossils spanning several continents, time periods, and taxa, 
and we showed, using immunochemistry, amino acid sequence data, and a 
variety of other methods, that collagen fragments were preserved in matrix 
tissues and chemical extracts of bone fragments in extremely low 
concentrations. Recently we showed that sufficient molecular signal was 
retained in these sequences to generate phylogenetic hypotheses that are 
consistent with other lines of evidence supporting the close relationship of 
birds and dinosaurs. Here, we present the results of multiple analyses 
conducted on the femur of an ~80 Ma [old] hadrosaur (*Brachylophosaurus 
canadensis*, MOR 2598). Hind limb elements of this dinosaur were collected 
specifically for molecular analyses, using a protocol designed to optimize 
the chances of such recovery, while minimizing introduction of contamination 
or artifact. We show preservation of the above endogenous components in 
skeletal elements of this dinosaur, and present evidence for the presence of 
proteins, including collagen, osteocalcin, hemoglobin, and elastin. Multiple 
phylogenetic analyses of amino acid sequence data place this hadrosaur well 
within Archosauria, closer to birds than crocodylians."

I'd have loved to hear this talk, but it was at the same time as my own...