Tag: Dinosaur-era shark fossil

January Science Snapshots

  • In order to take these mesmerizing microscopy images, the team carefully demineralized small bits of T. rex bone to liberate the preserved vessel tissue inside. The sample used in this study came from the femur of the famous, nearly complete fossil specimen known as “the Nation’s T. rex,” which is currently on display at the Smithsonian National Museum of Natural History.
  • Credit: Zosia Rostomian/Berkeley Lab
  • Credit: ClaudioVentrella/iStock
  • Photo by Stephen Leonardi on Unsplash
  • Credit: Boatman et al. and Smithsonian InstituteIn order to take these mesmerizing microscopy images, the team carefully demineralized small bits of T. rex bone to liberate the preserved vessel tissue inside. The sample used in this study came from the femur of the famous, nearly complete fossil specimen known as “the Nation’s T. rex,” which is currently on display at the Smithsonian National Museum of Natural History.

Berkeley Lab Helps Reveal How Dinosaur Blood Vessels Can Preserve Through the Ages

–By Aliyah Kovner 

A team of scientists led by Elizabeth Boatman at the University of Wisconsin Stout used X-ray imaging and spectromicroscopy performed at Berkeley Lab’s Advanced Light Source (ALS) to demonstrate how soft tissue structures may be preserved in dinosaur bones – countering the long-standing scientific dogma that protein-based body parts cannot survive more than 1 million years.

In their paper, now published in Scientific Reports, the team analyzed a sample from a 66-million-year-old Tyrannosaurus rex tibia to provide evidence that vertebrate blood vessels – collagen and elastin structures that don’t fossilize like mineral-based bone – may persist across geologic time through two natural, protein-fusing “cross-linking” processes called Fenton chemistry and glycation.

First, the scientists used imaging, diffraction, spectroscopy, and immunohistochemistry to establish that structures present in the sample are indeed the animal’s original collagen-based tissue. Then, Berkeley Lab co-authors Hoi-Ying Holman and Sirine Fakra respectively performed synchrotron radiation-based Fourier-transform infrared spectromicroscopy (SR-FTIR) to examine how the cross-linked collagen molecules were arranged, and X-ray fluorescence (XRF) mapping to analyze the distribution and types of metal present in T. rex vessels.

“SR-FTIR takes images and spectra of the same sample, and so you can reveal the distribution of protein-folding patterns, which helps to identify the possible cross-linking mechanisms,” said Holman, a senior scientist in the Molecular Biophysics & Integrated Bioimaging Division.

Fenton chemistry and glycation are both non-enzymatic reactions – meaning they can occur in deceased organisms – that are driven by the iron present in the body. “The XRF microprobe revealed the presence of finely crystalline goethite, a very stable iron oxyhydroxide mineral, on the vessels that likely contributed to the preservation of organic molecules,” said Fakra, an ALS research scientist.

The authors believe that the cross-linking reactions they found evidence of, combined with the protection offered from being surrounded by dense mineralized bone, can explain how original soft tissues persist.

Dinosaur-Era Shark Fossil Discovered in Kansas

Credit: (Image provided by Kenshu Shimada/DePaul University and Sternberg Museum of Natural History)

The shark is estimated to be nearly 17 feet or over 5 meters long

CHICAGO — A 91-million-year-old fossil shark newly named Cretodus houghtonorum discovered in Kansas joins a list of large dinosaur-era animals. Preserved in sediments deposited in an ancient ocean called the Western Interior Seaway that covered the middle of North America during the Late Cretaceous period (144 million to 66 million years ago), Cretodus houghtonorum was an impressive shark estimated to be nearly 17 feet or slightly more than 5 meters long based on a new study appearing in the Journal of Vertebrate Paleontology.

The fossil shark was discovered and excavated in 2010 at a ranch near Tipton, Kansas, in Mitchell County by researchers Kenshu Shimada and Michael Everhart and two central Kansas residents, Fred Smith and Gail Pearson. Shimada is a professor of paleobiology at DePaul University in Chicago. He and Everhart are both adjunct research associates at the Sternberg Museum of Natural History, Fort Hays State University in Hays, Kansas. The species name houghtonorum is in honor of Keith and Deborah Houghton, the landowners who donated the specimen to the museum for science.

Although a largely disarticulated and incomplete skeleton, it represents the best Cretodus specimen discovered in North America, according to Shimada. The discovery consists of 134 teeth, 61 vertebrae, 23 placoid scales and fragments of calcified cartilage, which when analyzed by scientists provided a vast amount of biological information about the extinct shark. Besides its estimated large body size, anatomical data suggested that it was a rather sluggish shark, belonged to a shark group called Lamniformes that includes modern-day great white and sand tiger sharks as distant cousins, and had a rather distinct tooth pattern for a lamniform shark, the researchers said.

“Much of what we know about extinct sharks is based on isolated teeth, but an associated specimen representing a single shark individual like the one we describe provides a wealth of anatomical information that in turn offers better insights into its ecology,” said Shimada, the lead author on the study.

“As important ecological components in marine ecosystems, understanding about sharks in the past and present is critical to evaluate the roles they have played in their environments and biodiversity through time, and more importantly how they may affect the future marine ecosystem if they become extinct,” he said.

During the excavation, Shimada and Everhart believed they had a specimen of Cretodus crassidens, a species originally described from England and subsequently reported commonly from North America. However, not even a single tooth matched the tooth shape of the original Cretodus crassidens specimen or any other known species of Cretodus, Shimada said.

“That’s when we realized that almost all the teeth from North America previously reported as Cretodus crassidens belong to a different species new to science,” he noted.

The growth model of the shark calibrated from observed vertebral growth rings indicates that the shark could have theoretically reached up to about 22 feet (about 6.8 meters).

“What is more exciting is its inferred large size at birth, almost 4 feet or 1.2 meters in length, suggesting that the cannibalistic behavior for nurturing embryos commonly observed within the uteri of modern female lamniforms must have already evolved by the late Cretaceous period,” Shimada added.

Furthermore, the Cretodus houghtonorum fossil intriguingly co-occurred with isolated teeth of another shark, Squalicorax, as well as with fragments of two fin spines of a yet another shark, a hybodont shark, the researchers said.

“Circumstantially, we think the shark possibly fed on the much smaller hybodont and was in turn scavenged by Squalicorax after its death,” said Everhart.

Discoveries like this would not be possible without the cooperation and generosity of local landowners, and the local knowledge and enthusiasm of amateur fossil collectors, according to the authors.

“We believe that continued cooperation between paleontologists and those who are most familiar with the land is essential to improving our understanding of the geologic history of Kansas and Earth as a whole,” said Everhart.

The new study, “A new large Late Cretaceous lamniform shark from North America with comments on the taxonomy, paleoecology, and evolution of the genus Cretodus,” will appear in the forthcoming issue of the Journal of Vertebrate Paleontology and is online at https://doi.org/10.1080/02724634.2019.1673399.

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Sources:
Kenshu Shimada
kshimada@depaul.edu
773-325-3697

Michael J. Everhart
mike@oceansofkansas.com
316-788-1354

Media Contact:
Russell Dorn
rdorn@depaul.edu
312-362-7128