Tylosaurus rex — and a lesson for India’s fossil heritage

Syllabus:  General Studies Paper III — Science & Technology  /  Environment (fossils and geo-heritage)

1. What happened

Scientists who study ancient life (palaeontologists) have identified a fearsome new prehistoric sea reptile, named Tylosaurus rex, in a study in the Bulletin of the American Museum of Natural History. 

       It ruled an ancient inland sea over North America about 80 million years ago in the Cretaceous Period — matching its famous land cousin, Tyrannosaurus rex, in both size and menace.

2. What it was — and what it was not

TYLOSAURUS REX — PLACING IT CORRECTLY IN THE TREE OF LIFE

THE DISCOVERY A new species of mosasaur — a group of large, extinct sea reptiles. Lived about 80 million years ago and was the top hunter of an inland sea over North America.

 

THE CRUCIAL POINT Mosasaurs were NOT dinosaurs. They were sea reptiles that evolved from land-living lizards during the last 30 million years of the dinosaur age — a completely separate branch of the family tree.

 

THEIR CLOSEST LIVING COUSINS Monitor lizards. This includes the Komodo dragon — the largest lizard alive today (about 3 metres), found in Indonesia.

 

HOW THEY DIED OUT Wiped out in the Cretaceous-Paleogene extinction, about 66 million years ago. Cause: a giant asteroid striking what is now the Chicxulub crater in Mexico  →  sudden global cooling and the collapse of ocean food chains.

 

THE INDIA CONNECTION India holds rich fossil beds of this era. The Narmada Valley region gave us Rajasaurus narmadensis (a genuine meat-eating dinosaur), and the Ariyalur–Tiruchirappalli belt of Tamil Nadu is world-famous for ancient sea fossils.

 

INTERESTING FACTS →  Mosasaur is NOT a dinosaur. It is a sea reptile from the lizard branch — the single most common mistake on this topic. →  Of the Big Five extinctions, the Permian-Triassic was the largest; the Cretaceous-Paleogene was the most recent and ended the dinosaurs. →  The Geo-heritage Sites Bill is still a Bill, not an Act. And the Komodo dragon is the largest living lizard, not the largest living reptile (that is the saltwater crocodile).

3. Why it matters for India

• The Geological Survey of India, under the Ministry of Mines, is the apex body that identifies and protects National Geo-heritage Sites (places of outstanding geological value).
• A proposed Geo-heritage Sites and Geo-relics (Preservation and Maintenance) Bill would give legal protection to fossil sites and curb illegal mining and the smuggling of fossils out of the country. (It is still a Bill — not yet a law.)
• The road ahead: dedicated national fossil museums and geo-tourism linked to village livelihoods, on the lines of the global ‘geoparks’ model.

UPSC VALUE BOX
Mosasaurs	Large, extinct sea reptiles of the Cretaceous Period. They evolved from land lizards; their closest living relatives are monitor lizards. They were not dinosaurs.
Convergent evolution	When unrelated animals separately evolve similar body shapes to suit the same lifestyle. Sea reptiles like mosasaurs, and much later whales, both became streamlined and flipper-driven — a textbook example.
The geological eras	Earth’s recent history splits into the Palaeozoic, Mesozoic and Cenozoic eras. The Mesozoic (Triassic + Jurassic + Cretaceous) is the ‘age of dinosaurs’.
The ‘Big Five’ mass extinctions	Five great die-offs in Earth’s history. The Permian-Triassic event (~252 million years ago) was the largest. The Cretaceous-Paleogene event (~66 million years ago), caused by an asteroid, was the most recent and ended the dinosaurs.
Rajasaurus narmadensis	An Indian meat-eating dinosaur from the Narmada Valley, formally described in 2003 from fossils found near Rahioli in Gujarat.
Geological Survey of India	Founded in 1851, it works under the Ministry of Mines and identifies and conserves the country’s National Geo-heritage Sites.

With reference to the recently described Tylosaurus rex and related species, consider the following statements:

1. Mosasaurs, including Tylosaurus rex, were a group of marine dinosaurs that died out in the Cretaceous-Paleogene extinction.
2. The closest living relatives of mosasaurs are present-day monitor lizards, including the Komodo dragon.
3. The Cretaceous-Paleogene extinction, about 66 million years ago, is widely linked to an asteroid impact at the Chicxulub crater in Mexico.

How many of the above statements are correct?

(a) Only one

(b) Only two

(c) All three

(d) None

ANSWER: (B) ONLY TWO