"It's been a mystery for very long time, why plesiosaur have these gastrous, the suggestions have been to help them grind up their food or just accident material accidentally ingested in them"
Gastroliths are stones of uncertain purpose that are commonly found inside the rib cages of plesiosaur fossils worldwide. Gastroliths from four Alberta (Canada) plesiosaurs were studied to determine both their shapes and masses, and their mass fractions relative to body mass.
“I realized I could use this Kepler hypothesis to estimate the mass of the stones, and it was such a tough, mathematical problem that a formal, rigorous solution wasn’t published until 400 years later in 2011, by mathematician Thomas Hales. He proved that the maximum density was about 0.74. and so I got a mass, a volume of this cluster of stones and I knew the density of the stones so with density times volume gives you a mass and then I applied this spherical packing correction factor to get the final value.“
Dr. Donald M Henderson (Royal Tyrrell Museum of Palaeontology)
For All Readers - AI Explainer
What is the focus of this research?
What is this research about?
This research focuses on plesiosaurs, large marine reptiles from the age of dinosaurs, and the gastroliths (stomach stones) found inside their rib cages. It looks at the shapes and weights of these stones and estimates how much mass they made up in relation to the plesiosaur’s body. The study examines how these stones might have been used by the animals and looks into the damage or missing stones in some fossils.
What are gastroliths, and why are they important?
Gastroliths are stones that some animals, including plesiosaurs, are thought to have swallowed. Scientists are still debating their purpose—whether they helped with digestion or acted as ballast to help with swimming. This study aims to learn more about these stones by studying their shapes and weights in plesiosaurs from Alberta, Canada.
Which plesiosaurs were studied?
The research studied four species:
- Albertonectes vanderveldei
- Fluvionectes sloanae
- Nichollssaura borealis
- Wapuskanectes betsynichollsae
These species lived in different types of water environments, including open marine, near-shore marine, and fluvial (river) systems.
How did the researchers study these gastroliths?
The researchers used four methods:
- Direct measurement of some visible stones and estimating the properties of the hidden or damaged ones.
- Calculating volume and mass of free stones based on their dimensions and density.
- For stones that were partially embedded, they estimated the missing dimension and calculated the volume and mass.
- For densely packed stones, they used geometrical calculations to estimate mass.
What did the research find about the mass of these stones?
The total mass of gastroliths in any plesiosaur never exceeded 0.2% of its body mass. This suggests that the amount of stone found would have been ineffective as ballast (meaning they probably didn’t help much with swimming or stabilizing the animals in water).
Were there any patterns in the shapes or types of stones?
Yes! The shapes of the gastroliths varied by environment, and the stones were mostly made of black chert, a type of rock. For two of the species—Nichollssaura and Wapuskanectes—which lived close to each other and during the same time period, the researchers think the gastroliths may have come from a common source.
What was the main takeaway from this research?
The study shows that plesiosaur gastroliths likely weren’t used for ballast due to their low mass. It also sheds light on how researchers can estimate missing or damaged parts of fossil finds, helping us better understand prehistoric animals and their environments.
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