When was the last day of dinosaurs on the Earth?

Bhumika Goel / March 2022

Dinosaurs lived on the Earth, for 175 million years, before their extinction. 66 million years ago an asteroid impact wiped out the specie completely from Earth.

What was the season of catastrophic extinction? Was it summer, winter, rains or spring?

It was springtime when dinosaurs last breathed on Earth.

A global team of researchers examined the fossil fishes from the Cretaceous era. The research team find out that it was springtime, when asteroid impact occurred.

How did the scientist conclude the season of dinosaur’s extinction?

The researchers studied selected fish bones. Seasonal growth of these bones was found similar to the growth of trees. Researchers also traced the bone cell density and volumes. And found them to be on a rising level, yet to reach the peak, at the time of death.

The team analysed the annual feeding pattern of paddlefishes using stable carbon isotope analysis. 13C carbon isotope presence in the fossils revealed zooplankton, an important food source, consumption. With the help of the carbon isotope signal, the researchers concluded that the feeding season had not reached its peak at the time of asteroid impact.

Since the zooplankton community peaks between spring and summer, spring was the unfortunate season of the selective historical extinction.

The availability of zooplankton, its prey of choice, oscillated seasonally and peaked between spring and summer. “This temporary increase of ingested zooplankton enriched the skeleton of its predator with the heavier 13C carbon isotope relative to the lighter 12C carbon isotope,” explains Suzan Verdegaal-Warmerdam of the VU Amsterdam. “The carbon isotope signal across the growth record of this unfortunate paddlefish confirms that the feeding season had not yet climaxed — death came in spring,” infers Melanie During from Uppsala University and the VU Amsterdam and lead author of the publication. Source
The research is published in the journal Nature.
Uppsala University. “The last day of the dinosaurs.” ScienceDaily

Conclusions

The asteroid impact brought the most selective historical extinction of various species. While dinosaurs, ammonites and pterosaurs vanished completely, the other marine reptiles including turtles and crocodiles survived.

The season identification of the most horrific asteroid impact, further helps us, to understand the reason of the other species survival on the Earth.

As the sudden extinction must have begun at some stage in northern-hemisphere spring. And the southern-hemisphere autumn happens at the same time. The survival’s winter preparations in the southern hemisphere gave them protection from the mass extinction.

Important Words:

Catastrophic Extinction:

The mass extinction of organisms on Earth that occurs due to catastrophic event such as volcano eruption or asteroid collision with Earth.

Cretaceous era:

The period between the Jurassic and Tertiary periods. It was the last period of the Mesozoic Era.

Zooplankton:

Animals of the planktonic community. They float or drift in the ocean water and may range from microscopic to large organisms. They are heterotrophic and cannot produce their own food. Example: Jellyfish

Carbon Isotope:

Stable carbon atoms with equal atomic number of carbon element, and different atomic weight. C-13 is a stable carbon isotope.