Fossilized Fish Reveal Earliest Known Prequel of ‘Jaws’

Author: Yuvi September 29, 2022

Fossilized Fish Reveal Earliest Known Prequel of 'Jaws'


Mention the ocean, and it’s hard not to think of jaws. The deep waters contain many tooth-lined mouths: the bear-trap maws of sharks and dolphins, the slack lips of shoaling and reef fish, the baleen-filter gape of enormous whales. Jawed fish eventually crawled out of the seas millions of years ago and gave rise to the jawboning vertebrates we are today.

But when did such an evolutionary innovation arise? A pair of fossil beds discovered in Southern China suggest that the answer may lie tens of millions of years deeper into the past than previously thought. The findings — which include beautifully preserved new species of early fish, the oldest-known vertebrate teeth and a lot of fish with armor — were published Wednesday across four papers in Nature.

“This is a step change in where we’re thinking about these events in the chronology of vertebrate evolution,” said Matt Friedman, a paleontologist at the University of Michigan who was not involved in the research but wrote a perspective article that accompanied the Nature papers.

Jawed fish explode into the fossil record 419-359 million years ago during a period known as the age of fish, or the Devonian. Fish of this era all have “their identities clearly written on their bodies,” said Michael Coates, a paleobiologist at the University of Chicago who was not involved in the new papers. They include ancient groups like jawless fish, lineages of early jawed fish called placoderms, ascendant newcomers like cartilaginous and bony fish and the first fishes to hop onto land.

This sudden diversity of jawed fish — also called gnathostomes — has long led scientists to suspect that their origins must lie deeper in the fossil record, a period known as the Silurian, said Per Ahlberg, a paleontologist at Uppsala University in Sweden and an author on one of the papers. But until recently, the number of useful Silurian gnathostome fossils could be counted on one hand.

A decade ago, researchers set out to systematically survey the 425-million-year-old rocks of the late Silurian period in China, said Gai Zhikun, a paleontologist at the Chinese Academy of Sciences and an author on one of the papers. They were rewarded with complete fossils of early jawed fish.

Encouraged, they delved into older rocks. In 2020 these fishing expeditions got a bite: a pair of deposits outside of Chongqing.

The two fossil beds are separated by a few million years in time, each with a different complement of species.

The 436-million-year-old bed contains “little fishtank-sized fishes,” Dr. Ahlberg said, only a few centimeters long, which represent the oldest-known complete jawed fish. Most are of a flat, armored placoderm species named Xiushanosteus mirabilis, which most likely lived on the seafloor. Also present is Shenacanthus vermiformis, a cartilaginous fish related to sharks and rays, but with armor plates resembling those of unrelated placoderms — a find that suggests early sharklike species retained the armor-plates present in earlier branches of the fish family tree.

Philip Donoghue, a paleontologist at the University of Bristol and an author on one of the papers, says the most remarkable specimen from the site is a jawless fish called Tujiaaspis vividus. Thousands of head shields from the species’ family are known from the fossil record, but Tujiaaspis preserves the first known body. It comes with a surprise: a set of paired fins jutting out from the skull, which Dr. Donoghue and his colleagues suggest is a likely precursor of the pectoral and pelvic fins found in gnathostomes, which for fish that moved onto land gave rise to arms and legs. Previously, researchers believed the two sets of fins evolved separately between jawless and jawed fish.

“It overturns conventional wisdom on how paired appendages originated,” Dr. Donoghue said.

The second site, at 439 million years old, preserved more important fossils. One paper describes a collection of spines, scales and head-plates from an animal named Fanjingshania renovata, all of them dead-ringers for later examples of cartilaginous fish. Another records a whirl of connected teeth — the oldest yet known from a vertebrate — from a fish named Qianodus duplicis. Both animals belong firmly to the branch of jawed fish called the chondrichthyans, the group of cartilaginous fish that include modern sharks, rays and ratfish. (Bony fish like salmon and humans are the other branch.)

The presence of shark relatives at the site suggests that the split between cartilaginous and bony fish had already occurred by the early Silurian, Dr. Friedman said. Taken together, both sites push the origin of vertebrate jaws and teeth back by almost 14 million years.

“It’s a big shift from the consensus chronology,” Dr. Friedman said, which will force a drastic reconsideration of early marine ecosystems.

Jawed fish now seem to have originated as early as the Great Ordovician Biodiversification, a period around 485 million to 445 million years ago when marine invertebrates ruled. The few known fish from that period are jawless and generally unprepossessing, Dr. Coates said. “They look like armor-plated tadpoles,” he said. “So the last thing you’d expect is for proto-sharks and proto-bony fish to be swanning around at the same time.”

As paleontologists continue to dig deeper into early Silurian rocks in China, they’ve uncovered even more fish species. When it comes to the earliest jawed fish, researchers may soon find that they’ll need a bigger boat.

“It’s highly likely that there will be more discoveries,” Dr. Ahlberg said. “It’s an overused phrase, but I mean it: This promises to completely revolutionize our understanding of the earliest phase of jawed vertebrate evolution.”

29 September, 2022, 1:21 am

News Cinema on twitter News Cinema on facebook

Thursday, 29th September 2022

More Stories
NATO Nations Grow More Receptive to US Pleas to Confront China
New York Police Name a Chief Who Has Faced Internal Discipline
South Africa’s President, Cyril Ramaphosa, Faces Impeachment Hearing
Elon Musk’s Neuralink to share progress of its brain chip tonight
Sam Brinton: Biden’s nuclear waste guru spoke at a spanking seminar weeks after bag theft
Could Theatrical Movies Shut Out Streamers for the Top Oscars?
17 Public Employees Charged in Schemes to Steal Covid Relief Funds
Deaths From Substance Abuse Rise Sharply Among Older Americans in 2020
White House ‘deeply concerned’ about Paul Whelan
‘Philadelphia is a war zone’: thug strolls up to parking official and shoots him in the head
Indian-origin doc slams ‘racist joke’ at British Curry Awards
Argentina’s World Cup Hangs in the Balance Against Poland
China completes world’s largest solar telescope array with 1.9-mile-wide ring of 313 dishes
Bigg Boss 16 Day 60 Updates: Housemates call Nimrit unfair for favoring Shiv and Soundarya in ranking task
FIFA World Cup 2022: Defending champion France lost to Tunisia
Mariah Carey offers fans opportunity to stay in her apartment BUT the star won’t even be there
House PASSES bill to stop a rail strike on December 9 after Biden asked Congress to step in
In Georgia, Walker’s Pace in the Finish Worries Republican Allies
Hiroshi Miyamura, Given Medal of Honor in Korean War, Dies at 97
Cops kill Illinois man and his grandpa while trying to stop younger man from stabbing his relative
A Resonant Topic in Georgia’s Senate Runoff: Insulin Prices
Spotify Wrapped drops but Apple Music Replay fans have it trending
The five ‘saboteurs’ trying to derail Kevin McCarthy’s Speaker bid: GOP leader’s allies push back
Biden gives 11 tribes $135M to move coastal buildings to higher ground due to climate change
FIFA World Cup 2022: Lionel Messi’s Argentina qualification scenario ahead of must-win clash vs Poland
MDMA could be approved for PTSD in the US by 2024
Moment Litvinenko said he’d been poisoned recreated for ITVX drama widow says keeps his voice alive
Layoffs Hit CNN as Cost-Cutting Pressure Mounts
In a Show of Unity, House Democrats Elect Hakeem Jeffries Minority Leader
Hit by sanctions over Ukraine war, Russia turns to India for products in its key sectors
Abhishek Banerjee, on Amitabh Bachchan as his role model, says ‘I want to do what he did in Deewar’
Verdict in Trump Organization Trial Could Come Down to 3 Little Words
Twitter’s former head of security says platform is LESS safe under Elon Musk and decries layoffs
Some Rail Workers, Seeking Sick Days, Say Biden Betrayed Them
NYU Putting $1 Billion Into Its Engineering School in Brooklyn
Joe Root gives big update on health of England cricket team hit by viral infection in Pakistan, says THIS
Covid now mainly disease of elderly: NIne in 10 deaths are over-65
Vijay Hazare Trophy 2022: Swaroopam Purkayastha, Sibshankar Roy help Maharashtra beat Assam by 12 runs to enter final
Spotify Wrapped 2022 LIVE STATS: View the top artists and songs
Job Openings Ease, But Layoffs Are Little Changed
Solar storm could launch 1.8 million mph solar winds at Earth TOMORROW
Shooting Suspect’s Video Adds to Questions About University’s Investigation