Fossil discovery: Extraordinary 'big-mouthed' fish from Cretaceous Period

February 8, 2016, DePaul University
An international team of scientists have discovered two new plankton-eating fossil fish species, of the genus called Rhinconichthys, which lived 92 million years ago in the oceans of the Cretaceous Period. Credit: Robert Nicholls

An international team of scientists have discovered two new plankton-eating fossil fish species of the genus called Rhinconichthys (Rink-O-nik-thees) from the oceans of the Cretaceous Period, about 92 million years ago, when dinosaurs roamed the planet.

One of the authors of the study, Kenshu Shimada, a paleobiologist at DePaul University, said Rhinconichthys are exceptionally rare, known previously by only one from England. But a new skull from North America, discovered in Colorado along with the re-examination of another skull from Japan have tripled the number of species in the genus with a greatly expanded geographical range. According to Shimada, who played a key role in the study, these species have been named R. purgatoirensis and R. uyenoi, respectively.

"I was in a team that named Rhinconichthys in 2010, which was based on a single species from England, but we had no idea back then that the genus was so diverse and so globally distributed," said Shimada.

The new study, "Highly specialized suspension-feeding bony fish Rhinconichthys (Actinopterygii: Pachycormiformes) from the mid-Cretaceous of the United States, England and Japan," will appear in the forthcoming issue of the international scientific journal Cretaceous Research.

The research team includes scientists from government, museum, private sector and university careers. They include Bruce A. Schumacher from the United Sates Forest Service who discovered the new specimen. It also includes researchers, Jeff Liston from the National Museum of Scotland and Anthony Maltese from the Rocky Mountain Dinosaur Resource Center.

Rhinconichthys was estimated to be more than 6.5 feet and fed on plankton. It had a pair of bones called hyomandibulae, which formed a massive oar-shaped lever to protrude and swing the jaws open extra wide, like a parachute, in order to receive more plankton-rich water into its mouth. Credit: Kenshu Shimada

Rhinconichthys belongs to an extinct bony fish group called pachycormids, which contains the largest bony fish ever to have lived. The new study specifically focuses on highly elusive forms of this fish group that ate plankton.

Rhinconichthys was estimated to be more than 6.5 feet and fed on plankton. It had a highly unusual specialization for . According to Shimada, one pair of bones called hyomandibulae formed a massive oar-shaped lever to protrude and swing the jaws open extra wide, like a parachute, in order to receive more plankton-rich water into its mouth, similar to the way many sharks open their mouth.

A planktivorous diet, also called suspension-feeding, is known among some specialized aquatic vertebrates today, including the Blue Whale, Manta Ray and Whale Shark. The name Rhinconichthys means a fish like the Whale Shark, Rhincodon. Suspension-feeding in the dinosaur era is a new emerging area of research.

"Based on our new study, we now have three different species of Rhinconichthys from three separate regions of the globe, each represented by a single skull," Shimada noted. "This tells just how little we still know about the biodiversity of organisms through the Earth's history. It's really mindboggling."

Explore further: Researchers discover new lineage of prehistoric, plankton-eating sharks

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Whydening Gyre
5 / 5 (1) Feb 08, 2016
Wouldn't they have been a lot closer together inasmuch current continents are the result of supercontinent (Pangea) breakup?
Since that breakup began approx. 175mya, that would put continents 92mya about half-way to their current positions, wouldn't it?
khperkins
not rated yet Feb 09, 2016
@Whydening Gyre
Wouldn't they have been a lot closer together inasmuch current continents are the result of supercontinent (Pangea) breakup?
Since that breakup began approx. 175mya, that would put continents 92mya about half-way to their current positions, wouldn't it?

That's like saying all the trout in a stream should be in one pool. They swam in the ocean(s) and there were probably millions (and millions) of them, so fossils found in various places around the world isn't really a stretch.
bluehigh
1 / 5 (2) Feb 09, 2016
Crikey, at first look of the title pic I thought it might be an artists impression.

But No, it's likely Anti-Thinking and Phys1 actually photographed !

'Mind' you .. What's an 'impression' anyway?

promile
Feb 09, 2016
This comment has been removed by a moderator.
Whydening Gyre
5 / 5 (2) Feb 09, 2016
'Mind' you .. What's an 'impression' anyway?

I get the impression you're not sure...
bluehigh
not rated yet Feb 09, 2016
"It's really mind boggling" - Kenshu Shimada
Whydening Gyre
5 / 5 (2) Feb 10, 2016
"It's really mind boggling" - Kenshu Shimada

Welcome to MY world...:-)
Lex Talonis
not rated yet Feb 14, 2016
No it's actually Satanic trickery, to deceive the world into thinking that life on earth evolved before the god of the jews did.
Captain Stumpy
5 / 5 (2) Feb 15, 2016
but what this finding (from 2015 year) could mean?
@ZEPH
for starters, i would like to see a link to a more reputable site before even trying to expound on the subject - so find one and link it
for two - just because there isn't an immediate answer doesn't mean "The mainstream science ignores all findings, which don't fit the established paradigm consequentially"

that is all your conspiracist ideation and fanatic devotion to falsified hypothesis talking

... but still interested in the "sea wolf" if you want to find something more scientific to link

.

No it's actually Satanic trickery
@Lex
is that hyperbole or are you just being satirical (or even sarcastic)?

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