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Deep-Sea Ghost Sharks Grow Teeth on Their Foreheads, and Scientists Finally Know Why
Scitech Daily ^ | September 21, 2025 | Eric Hamilton, University of Florida

Posted on 09/22/2025 5:50:58 AM PDT by Red Badger

Caught male Spotted Ratfish (Hydrolagus colliei) showing the [extended/erect] frontal clasper (tenaculum) on the front of the head. Credit: Gareth J. Fraser, University of Florida

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Male ghost sharks use tooth-studded rods on their foreheads for mating. Fossil and genetic evidence prove they are true teeth, showcasing evolutionary flexibility.

Male “ghost sharks,” eerie deep-sea fish known as chimaeras and closely related to sharks and rays, have a strange rod that projects from their foreheads and is covered with sharp, retractable teeth. New research shows these are not simple imitations but actual rows of teeth that develop outside the mouth.

The unusual structure, called a tenaculum, is found only in males and is thought to play a role in reproduction. It represents the species’ only set of distinct teeth and appears to help males hold onto females during mating, much like sharks use their mouths and teeth for the same purpose.

“If these strange chimaeras are sticking teeth on the front of their head, it makes you think about the dynamism of tooth development more generally,” said Gareth Fraser, Ph.D., a professor of biology at the University of Florida and senior author of the study. “If chimaeras can make a set of teeth outside the mouth, where else might we find teeth?”

Fossil and modern evidence of tooth rods Researchers from the University of Washington and the University of Chicago examined both fossilized remains and living ghost sharks to unravel the mystery. One fossil, dating back 315 million years, revealed a tenaculum connected to the upper jaw that carried teeth strikingly similar to those found inside the mouth. Modern specimens taken from Puget Sound displayed the same head-based tooth development observed in the jaws of present-day sharks. Genetic analysis further confirmed that these structures activated the same genes responsible for producing oral teeth.

Juvenile Spotted Ratfish (Hydrolagus colliei) sits in the palm of the hand. Credit: Gareth J. Fraser, University of Florida

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“What we found is that the teeth on this strange appendage look very much like rows of shark teeth. The ability to make teeth transferred onto that appendage, likely from the mouth,” Fraser said. “Over time, the tenaculum shortened but retained the ability to make oral teeth on this forehead appendage.”

Fraser collaborated with Washington’s Karly Cohen, Ph.D., and Michael Coates, Ph.D., from Chicago on the study, which was published this week in the Proceedings of the National Academy of Sciences.

Distinguishing teeth from skin denticles Specialists in shark evolution and anatomy were fascinated by the tooth-covered rods emerging from the foreheads of ghost sharks. Their main question was whether the tenaculum contained genuine teeth connected to those in the mouth, or if it more closely resembled the tooth-like scales that cover the skin of sharks and some ghost sharks.

CT Scan of an Adult Male Spotted Ratfish Frontal Clasper

CT (computed tomography) scan of the adult male Spotted Ratfish frontal clasper (Tenaculum) covered in rows of teeth (rainbow colors). Credit: Specimen scanned by Karly Cohen; rendering and image by Ella Nicklin

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CT scans of the fossils and modern chimaeras gave the scientists unprecedented, detailed insights into the development of the tenaculum teeth, which looked remarkably similar to the teeth of today’s sharks. The nail in the coffin came from genetic evidence. The tenaculum teeth express genes found only in true teeth, never in shark skin denticles.

Evolutionary tinkering and surprising adaptation

“What I think is very neat about this project is that it provides a beautiful example of evolutionary tinkering or ‘bricolage,’” said Coates, a professor of biology at the University of Chicago. “We have a combination of experimental data with paleontological evidence to show how these fishes co-opted a preexisting program for manufacturing teeth to make a new device that is essential for reproduction.”

Cohen, a postdoctoral researcher at the University of Washington’s Friday Harbor Labs and first author of the paper, said scientists had never spotted teeth outside the mouth in this way before.

“The tenaculum is a developmental relic, not a bizarre one-off, and the first clear example of a toothed structure outside the jaw,” she said.

The bizarre path from a mouth full of teeth to forehead teeth used for mating demonstrates the impressive flexibility of evolution, the researchers say, always ready to repurpose structures for strange and unexpected new uses.

“There are still plenty of surprises down in the ocean depths that we have yet to uncover,” Fraser said.

Reference:

“Teeth outside the jaw: Evolution and development of the toothed head clasper in chimaeras”

by Karly E. Cohen, Michael I. Coates and Gareth J. Fraser, 4 September 2025, Proceedings of the National Academy of Sciences.

DOI: 10.1073/pnas.2508054122


TOPICS: Education; Outdoors; Pets/Animals; Weird Stuff
KEYWORDS: cryptobiology; ghostsharks; godsgravesglyphs; hickeys
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1 posted on 09/22/2025 5:50:58 AM PDT by Red Badger
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To: Red Badger

What about lasers?


2 posted on 09/22/2025 5:51:55 AM PDT by dfwgator ("I am Charlie Kirk!")
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To: dfwgator

That didn’t take long.....................😎


3 posted on 09/22/2025 5:52:25 AM PDT by Red Badger (Homeless veterans camp in the streets while illegals are put up in 5 Star hotels....................)
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To: Red Badger

I once and thankfully only once had over 1000 ratfish in my bottom cod fish set net. Took 6 hours to get them all out and finally retrieve the net.

One rat fish dropped out of the net, as it came aboard in a cluster of them, and fell to the deck - the spine on its dorsal pieced my boot went through my foot and into the deck. So yes, I rightfully hate them.

The net was trashed had had to undergo major repairs dockside in the 38 degree weather.


4 posted on 09/22/2025 6:02:11 AM PDT by PIF (They came for me and mine ... now its your turn)
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To: Red Badger; dfwgator
I dated a woman like that...


5 posted on 09/22/2025 6:02:31 AM PDT by DannyTN
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To: Red Badger

Must be where Bill Clinton got the idea from.


6 posted on 09/22/2025 6:03:42 AM PDT by ryderann
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To: Red Badger

Tried deep frying a fillet - but it came out like tissue paper and tasted of nothing. The teeth are for breaking shellfish, small crabs etc - what they eat.


7 posted on 09/22/2025 6:05:39 AM PDT by PIF (They came for me and mine ... now its your turn)
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To: Red Badger

probablya good time to review the terrifying reality of mutant chicken teeth.

https://www.scientificamerican.com/article/mutant-chicken-grows-alli/

Mutant Chicken Grows Alligatorlike Teeth

(this is all part of the Creator’s unfathomable plans)


8 posted on 09/22/2025 6:18:32 AM PDT by epluribus_2 (!)
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To: epluribus_2

“Oh, yeah. Oooh, ahhh, that’s how it always starts. Then later there’s running and screaming”

Dr. Ian Malcolm


9 posted on 09/22/2025 6:23:18 AM PDT by epluribus_2 (!)
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To: Red Badger

Rather than an aid to clasping, there is wide agreement that the Tenacula have the spike for foreplay


10 posted on 09/22/2025 6:24:27 AM PDT by bert ( (KE. NP. +12) Where is ZORRO when California so desperately needs him?)
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To: Red Badger

11 posted on 09/22/2025 6:31:30 AM PDT by Magnum44 (...against all enemies, foreign and domestic... )
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To: StayAt HomeMother; Ernest_at_the_Beach; 1ofmanyfree; 21twelve; 24Karet; 2ndDivisionVet; 31R1O; ...
Someday this information will be taught in, yes, you guessed it, *school*.

12 posted on 09/22/2025 6:32:14 AM PDT by SunkenCiv (NeverTrumpin' -- it's not just for DNC shills anymore -- oh, wait, yeah it is.)
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To: bert

ONE individual fish that evolved with those teeth are the ones that carried forward the species.

Not surprised...


13 posted on 09/22/2025 6:36:36 AM PDT by Does so ("Things will now change in Minneapolis AND AT HOME"....Dem☭¢rat... ∅ ™ ¿ ¡ ☞ ½¼)
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To: DannyTN

Nice claspers on that one!!


14 posted on 09/22/2025 6:43:11 AM PDT by tet68 ("We would not die in that man's company that fears his fellowship to die with us." Henry V.)
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To: epluribus_2

Alligators should reciprocate and grow wings.

Flying alligators! How cool would that be. (At least in a movie.)


15 posted on 09/22/2025 6:43:24 AM PDT by Moltke (Reasoning with a liberal is like watering a rock in the hope to grow a building.)
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To: Red Badger

This wouldn’t be near as strange as finding teeth around their butt holes.


16 posted on 09/22/2025 6:54:37 AM PDT by antidemoncrat
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To: Red Badger
“One fossil, dating back 315 million years, revealed a tenaculum connected to the upper jaw that carried teeth..." "We have a combination of experimental data with paleontological evidence to show how these fishes co-opted a preexisting program for manufacturing teeth to make a new device that is essential for reproduction.” "showcasing evolutionary flexibility."

So teeth "essential for reproduction' developed over millions (?) of years, thus explaining how they reproduced over millions of years.

Perfectly logical. Given enough time, such evolutionists can develop of form of logic essential for supporting this.

17 posted on 09/22/2025 6:57:39 AM PDT by daniel1212 (Turn 2 the Lord Jesus who saves damned+destitute sinners on His acct, believe, b baptized+follow HIM)
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To: Magnum44
For home protection, we have The Bear Cavalry:


18 posted on 09/22/2025 7:08:52 AM PDT by Diana in Wisconsin (I don't have, 'Hobbies.' I'm developing a robust Post-Apocalyptic skill set.)
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To: Red Badger
“If chimaeras can make a set of teeth outside the mouth, where else might we find teeth?”

Teeth

19 posted on 09/22/2025 7:16:59 AM PDT by null and void (The only man in all of Scotland is a 14 year old girl...)
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To: null and void

I think I dated her .................


20 posted on 09/22/2025 7:27:35 AM PDT by Red Badger (Homeless veterans camp in the streets while illegals are put up in 5 Star hotels....................)
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