Gareth Fraser

Our latest: Investigating the morphogenesis and replacement of lamprey toothlets using synchrotron imaging, led by Madleen Grohganz @bristolpalaeo.bsky.social, just out in Journal of Morphology. onlinelibrary.wiley.com/doi/epdf/10....

Multicolored CT model of a fossil cichlid skeleton. Image credit: Austin Babut (project technician).

Do you like cichlids? Fossils? Fossil cichlids? Would you like to study them as part of a graduate degree at the University of Michigan, joining an NSF-funded project? Get in touch.

Get to Know the Ratfish and the Forehead Teeth It Uses During Sex

Last week I had my mind blown by the tenaculum,
a fleshy club-like appendage growing out of a male ghost shark's forehead. The structure is studded with teeth and used to keep females close during mating.

Latest for @nytimes.com explores the structure's evolution: www.nytimes.com/2025/09/06/s...

Get to Know the Ratfish and the Forehead Teeth It Uses During Sex

Excellent article on our latest ghost shark forehead "jaw" paper @pnas.org; written by @jack-tamisiea.bsky.social
@nytimes.com - "Get to Know the Ratfish and the Forehead Teeth It Uses During Sex" 👻🦈🦷 @karlycohen.bsky.social @ufresearch.bsky.social

www.nytimes.com/2025/09/06/s...

brightfield images of three lizard embryos of approximately the same developmental stage. Below each embryo image is an immunofluorescence image labeling E-cadherin (green) and alpha-smooth muscle actin (magenta) of their developing lungs

New preprint from some of my postdoc work on lungs! Co-led with Kaleb Hill, we studied smooth muscle and epithelial development in lizard lungs. Stay tuned for more!
www.biorxiv.org/content/10.1...

Teeth outside the jaw: Evolution and development of the toothed head clasper in chimaeras | PNAS Chimaeras (Holocephali) are an understudied group of mostly deep-ocean cartilaginous fishes (Chondrichthyes) with unique characteristics that disti...

Super excited to share our new paper, out today @pnas.org 'Teeth outside the jaw: Evolution and development of the toothed head clasper in chimaeras' @karlycohen.bsky.social 👻🦈 🦷 www.pnas.org/doi/10.1073/...

The metamorphic transition of the frog mouth: from tadpole keratinized mouthparts to adult teeth | Royal Society Open Science Teeth have been a prominent feature of most vertebrates for 400 million years, and the core regulatory network underlying embryonic tooth formation is deeply conserved. In frogs, however, odontogenesi...

Excited to share our new paper by @danpaluh.bsky.social out today in @royalsociety.org Open Science; with a great team, including undergraduate researchers! "The metamorphic transition of the frog mouth: from tadpole kertanized mouthparts to adult teeth" 🦷🐸
royalsocietypublishing.org/doi/10.1098/...

Shark tooth regeneration: RNAseq reveals genes for unlimited dental renewal Sharks are masters of tooth regeneration with a rapid and unlimited tooth supply. We present a comprehensive transcriptomic analysis across five distinct compartments from the embryonic shark mouth, c...

Ever wondered how #sharks produce an unlimited supply of teeth? Our new preprint uncovers the genes within the dental stem cell niche driving lifelong tooth development. "Shark tooth regeneration: RNAseq reveals genes for unlimited dental renewal" 🦈🦷
bit.ly/47kkRHL

Our new paper is out in Royal Society Open Science! The metamorphic transition of the frog mouth: from tadpole keratinized mouthparts to adult teeth doi.org/10.1098/rsos...

Shark tooth regeneration: RNAseq reveals genes for unlimited dental renewal https://www.biorxiv.org/content/10.1101/2025.08.26.672487v1

Sandbar Shark, Carcharhinidae - 3D model by FloridaMuseum A fluid preserved Sandbar Shark, Carcharhinus plumbeus, from the Florida Museum of Natural History Ichthyology Collection (UF 108719). This specimen is a fetus that has a spinal column deformity. O...

Check out this "donut" Sandbar #Shark (Carcharhinidae) embryo in #3D, #VR or #AR via @sketchfab.bsky.social, photogrammetry by Kayla Evans @floridamuseum.bsky.social. This specimen is from a set of embryos with spinal deformations. @ufresearch.bsky.social

skfb.ly/pAqxN

50 years after ‘Jaws’ the man-eater myth has been retired - Australian Geographic In the half a century since Jaws was released we know so much more about sharks’ amazing biology.

An article I wrote on the legacy of JAWS for the 50th anniversary was picked up by Australian Geographic! 🦈🦈 ausgeo.co/jaws

Here's a tortoise embryo developing inside its egg. Check out our new article in @cp-iscience.bsky.social to learn how molecular and mechanical systems sculpt their intricate head scales 🐢🧪
www.cell.com/iscience/ful...

First case of parthenogenesis in an intersexual zebra shark (Stegostoma tigrinum) having incomplete claspers onlinelibrary.wiley.com/doi/10.1111/...

It's been 50 years since the blockbuster movie ‘Jaws,’ but there's more to be revealed about shark biology A shark expert, whose own curiosity about these fascinating fish was sparked by the movie "Jaws," explains some of their unique features and the many discoveries made in the decades after its release.

In 1975, “Jaws” – the tale of a killer great white shark that terrorizes a coastal tourist town – captured people’s imaginations and simultaneously created a widespread fear of the water. (via @us.theconversation.com)

PBS News @pbsnews.org posted my article with @theconversation.com on the progress of shark science and the evolving perception of sharks since the release of 'JAWS', 50 years ago! 🦈🦈🦈 #jaws #jaws50 #sharks

50 years after ‘Jaws,’ researchers have retired the man-eater myth and revealed more about sharks’ amazing biology A shark expert whose own curiosity about these fascinating fish was sparked by the movie explains some of their unique features. Many discoveries came in the decades after ‘Jaws.’

50 years after ‘Jaws,’ researchers have retired the man-eater myth and revealed more about sharks’ amazing biology theconversation.com/50-years-aft...

The "Tooth Hurty" Joke Has Its Origins In Ancient, Armored Fish | Defector Whenever Yara Haridy, a paleontologist at the University of Chicago, shows off the fossils she works with, people are often disappointed. Unlike the statuesque bones of dinosaurs or even the small spi...

The “Tooth Hurty” Joke Has Its Origins In Ancient, Armored Fish - defector.com/the-tooth-hu...

Transparent shark egg case showing an embryonic small-spotted Catshark.

Cool shot of a super clear Catshark (Scyliorhinus canicula) egg. These shark egg cases vary in their transparency. This one is particularly see through. 🦈🦈🦈

The first teeth were sensory organs on the skin of ancient fish Teeth are good for chewing and biting, but they are also sensitive – and that may have been their original function hundreds of millions of years ago

Toothache may be hundreds of millions of years old. Teeth first evolved as sensory organs, not for chewing, according to a new analysis of animal fossils.

That look!! 👀 Our resident Bobcat came to visit this morning; captured on the backyard trail-cam! Such an awesome sight. I wonder if we'll have bob-kittens soon. 🐆 #bigcat #bobcat #backyardwildlife

Tooth development in frogs: Implications for the re-evolution of lost mandibular teeth and the origin of a morphological innovation - preLights The tooth, the whole tooth and nothing but the… frog? – the not-so bite-sized mystery of frog tooth re-evolution 🐸🦷

The tooth, the whole tooth and nothing but the… frog? – the not-so bite-sized mystery of frog tooth re-evolution 🐸🦷

Check out this really fun post by @ryanharrison13.bsky.social, covering recent work from @danpaluh.bsky.social & team #preprint

#preLight ⬇️ 👀
prelights.biologists.com/highlights/t...

CT scan of the head clasper (tenaculum) from the Spotted Ratfish (Hydrolagus colliei), compete with its rows of shark-like teeth!

Our paper features fossil reconstruction art (of Helodus simplex) by Ray Troll - https://www.trollart.com/

New Pre-Print Alert! "Teeth Outside the Jaw: Evolution and Development of the Toothed Head Clasper in Chimaeras." We use fossil evidence, development and CT scans through ghost shark ontogeny to describe the emergence of the tenaculum! 👻🦈🦷 @karlycohen.bsky.social
www.biorxiv.org/content/10.1...

🚨Registration for the UK #EvoDevo meeting is open! Join us on July 11th in London to enjoy an exciting day of talks, posters, friends, and superb science!
-Registration (only £5!): shorturl.at/9cQGL
-More info: londonevodevo.ac.uk

Exciting news! @wcratcliff.bsky.social and I published an essay last week in @nature.com reviewing the substantial contributions of 'long-term' studies to evolutionary biology
www.nature.com/articles/s41...

1/n

Morphogenesis and regeneration during shark odontode development

#DBfeature 🦈🦷

Evolution, development, and regeneration of tooth-like epithelial appendages in sharks

by Ella Nicklin, Gareth Fraser et al @ellanicklin.bsky.social @garethjfraser.bsky.social
www.sciencedirect.com/science/arti...

Check out this "donut" shark! From the @floridamuseum.bsky.social - malformed embryos of the sandbar shark (Carcharhinus plumbeus). @ellanicklin.bsky.social CT scanned this specimen to show very odd development of the vertebral column, with no division of the centra and odd mineralization! 🍩🦈 #shark

Excited to share our new preprint, Tooth development in frogs: Implications for the re-evolution of lost mandibular teeth and the origin of a morphological innovation doi.org/10.1101/2025...

Tooth development in frogs: Implications for the re-evolution of lost mandibular teeth and the origin of a morphological innovation Teeth have been a prominent feature of most vertebrates for 400 million years, and the core regulatory network underlying embryonic tooth formation is deeply conserved from fishes to amniotes. In frog...

New preprint alert. Ever wondered why frogs only have upper jaw teeth? @danpaluh.bsky.social investigates this conundrum and asks if frogs ever form lower jaw tooth rudiments and what the relationship is between tadpole keratodonts (keratin mouthparts) and teeth! 🐸🦷🔥

www.biorxiv.org/content/10.1...

zebrafish pigment cells

New NIH funded research from our group now out. We are interested in development and evolution of cell types and adult phenotypes. In this paper, postdoc Dylan Huang and collaborators asked how a pigmentary ornament of bright white cells develops on the fin of zebrafish. www.pnas.org/doi/10.1073/...