Jump to content

Recommended Posts


A couple days ago I embarked on an adventure to a site I was never expecting to visit. The setting was a family vacation to the Hawaiian islands of Maui and Oahu and I initially had no intention of crawling around in gravel bars as I so often do at home. Nevertheless one thing led to another and I ended up going on a hunt that was perhaps the most unforgettable outing of my fossil career and I came away with some amazing specimens impossible to find anywhere else.






Our trip started on the lesser populated island of Maui which is a bit younger than its sibling Oahu. The landmass can be described as a valley where two large volcanoes form the east and west edges. The Hawaiian islands get older as you travel westward and this trend is true for Maui. The western half of the island is about 1.3 million years old whereas the eastern is only about 0.75 million. To my knowledge, there isn't any fossil bearing strata on the shores, but that doesn't mean a fossil hunter will be left with nothing to do on their visit.


Snorkeling was my main activity throughout the trip. Of course there are tons of interesting sea creatures to admire on the visit, but I think my recent fossil interests have given me an extra sense of appreciation for the ocean life. I don't have any underwater equipment, so there's sadly no photos from beneath the waves, but I captured some neat stuff from out of the water.



Horn-eyed Ghost Crab catching a wave (Ocypode ceratophthalmus)



Little green crab washed out of the water



Had no idea what this was at first (between starfish or urchin). Turned out to be a helmet urchin which is adapted for attaching strongly to rocky surfaces. Colobocentrotus atratus


I was surprised to find that the beach sand contained millions of tiny urchin spines mostly from the rock boring urchins living just beneath the waves. I didn't take any home, but occasionally a large red spine from a pencil slate urchin would wash up as well.



Rock boring urchin spines


Most of the beaches on Maui weren't all that great for combing. It wasn't until I took a closer look in the waters that I finally came across a spot with gravelly deposits. As I snorkeled it was impossible to keep my eyes away from them and I kept hallucinating various fossils showing up. Eventually, one hallucination actually proved to be the real deal, so I held my breath and dove down a few meters to retrieve what I had spotted.



Echinometra mathaei


While technically not a fossil, these recently-deceased oblong urchins were too cool to leave alone. They belong to the species Echinometra mathaei which is the most common urchin in Hawaii. When it comes to fossils, understanding the original animal's behavior is a difficult task. In this instance, it's actually very easy as the living counterparts are literally all over the place. They are a burrowing urchin that use their spines and teeth to carve out rocky holes for hiding during the day. At night they leave to graze on algae. Makes me wonder what sort of neat behaviors are hidden amongst our local Cretaceous urchins here in Texas :zzzzscratchchin:.


Besides urchins, I also came across some beautiful Hawaiian Snakehead Cowries (Monetaria caputophidii) as well as one Granulated Cowry (Nucleolaria granulata). Both of which are endemic to Hawaii.



Monetaria caputophidii



Nucleolaria granulata


That about sums up the Maui finds. This pushed me to do a little research on fossils in Hawaii and I was surprised to find on FF that Oahu was actually known to possess some Pleistocene reef. @hemipristis has a lot of great stuff on the island! I saw him mention finding teeth on one of Oahu's coasts in the Waimanalo Fm. I did a little satellite searching on that particular coast and found 3 potential spots to later check out.






For those interested in the geology, the Waimanalo Formation is Pleistocene-aged limestone resting atop basalt at various points around the island. While the island is 3-4 million years in age, the Waimanalo Formation is only about 130 thousand. This age is significant because it aligns with the latest interglacial period known as the Eemian or Sangamonian Stage. Despite being nestled within glacial periods, this point in time was actually quite warm and sea levels were accordingly raised. The ocean was about 8 meters higher compared to today. It's fascinating to observe fossils from such a unique time period. 


Of the three potential sites, I was only able to find access to two. Of the two, one site was a bust and had no sign of the Waimanalo being completely volcanic. Thankfully, I found one amazing site. I made a brief initial visit where I hunted mostly the exposure itself. The finds were only invertebrate in nature consisting of gastropods, bivalves, and crab claws. These were cool, but they didn't meet my highest goal of finding a Hawaiian shark tooth. My family was waiting on me, so I didn't get the chance to browse the gravel talus underneath. On the last day of the trip, after some begging and various concessions, I was granted just one hour to hunt which I gladly took. I sprinted out to the site so as to not waste any time. It was hot and humid. The black lava rocks absorbed a lot of the heat and were uncomfortable to navigate, but that didn't dissuade me. In all the gravel there had to be at least one shark tooth.


The first vertebrate find turned out to be bony fish. I've never found one of these before, but I've seen similar stuff across the web from around the world. These are usually referred to as pufferfish mouth plates, but they are actually from the family Diodontidae or porcupinefish/burrfish. This particular specimen was burnt orange and possessed partial jaw elements as well as fossilized worms tubes on its surface. I was leaping up and down! After reading more on the topic, it seems that this belongs to the genus Chilomycterus and perhaps the species C. reticularus commonly known as the Spotfin Burrfish (the only Chilomycterus species found in Hawaii today).



Chilomycterus reticulatus jaw fragment


Not too long after I found a couple more mouth plates, but this time not from a burrfish. Whereas burrfish (Chilomycterus) only have about 1-4 sheets exposed on their crushing dentition, porcupinefish (Diodon) have much more at 10-18 according to a conversation I found on ResearchGate. In Hawaii, the genus Diodon is represented by two species: the larger D. hystrix and smaller D. halocanthus. It's difficult for me to make a distinction between the two species, so I'll just have to stick with Diodon sp. for now. The first porcupinefish specimen was only a large broken half. The second specimen, however, is quite a beauty and one of my favorite fossils of all time!



Diodon sp. in original matrix with volcanic inclusions


This piece is about as Hawaiian as a fossil can get. The ancient reef bed the mouth plate is preserved in also features numerous small volcanic inclusions.


After some time collecting the gastropods not already picked up from the prior visit, I stumbled upon what I had been dreaming of the entirety of my visit. Sitting plainly atop the rubble was a tan shark tooth in nice condition. I tried to milk the moment a little, picking it up slowly and soaking in every second. I was at a total loss for words and more or less silently slipped it into my pouch. It is likely from the species Carcharhinus melanopterus also known as the Blacktip Reef Shark and the most common shark in Hawaii today. I suppose there are many other Carcharhinus species present in the area, but I think Blacktip is the most likely. Before this tooth, my youngest shark was from the Eocene strata at the Whiskey Bridge. This was quite the temporal extension to my collection :default_clap2:.



Carcharhinus melanopterus


At the very end of the hunt, I picked up a fragment of a shark tooth with fine serrations. I think it is likely also Carcharhinus melanopterus, but it's hard to say. Its size is very small.



Carcharhinus melanopterus?


So that about wraps up this unforgettable hunt! It's crazy to think that the second state I'd ever find a fossil on wasn't some place like Oklahoma. It's a surreal feeling to look at these various finds and imagine their lives 5 timezones away and 130 thousand years into the past. Hopefully you enjoyed reading this post almost as much as I enjoyed writing it!


Here's the overview of the rest of the finds from Oahu:

The species are based off of what I can find from modern Hawaiian waters



Various crab bits



Tellinella crucigera



Quidnipagus palatam



Unknown bivalve



Ctena bella






Monoplex nicobaricus?



Cypraea sp.



Nerita picea



Peristernia sp.?



Conus aff. spiceri




Canarium sp.?



Canarium sp.?



Littoraria sp.



Amplustrum amplustre? (Look up "Bubble snail")



Morula lepida



Ceritherium sp.



Drupa aperta



Cellana sp.







Thanks for reading!



Monachus schauinslandi

  • Enjoyed 18
Link to post
Share on other sites



Nice to see recent species !



  • Thank You 1
Link to post
Share on other sites

Great report! I just so happen to be in Maui right now. I didn’t consider any fossil hunting, but I too enjoy snorkeling and scuba diving. I did a dive yesterday off the coast of Lanai, called The Cathedrals. About 70 feet down inside a partially collapsed lava tube the sunlight beams down and reminds one of being in a cathedral with stained glass windows. Snorkeling today with sea turtles was very cool also!

  • Enjoyed 5
Link to post
Share on other sites

@garyc enjoy your trip! Scuba sounds really fun. Might have to look into it myself one day. 70 feet down sounds pretty risky  but I’m guessing only the pros get to do it :D. Keep an eye out for some aquatic souvenirs ;) 


Link to post
Share on other sites
Tidgy's Dad

Very interesting report, I rather enjoyed that. 

Your last 'unknown' photograph is a gastropod operculum. 

  • I found this Informative 2
Link to post
Share on other sites

Spot on Adam. Good find, gastropod opercula tend to get lost in the fossil record.

  • I Agree 1
Link to post
Share on other sites

That was a great report. Did your family appreciate your findings? My eyes and mind would have to be traveling a mile a second to hunt only for one hour! :heartylaugh:

  • Enjoyed 1
Link to post
Share on other sites
6 hours ago, EPIKLULSXDDDDD said:




This is a gastropod operculum. Many gastropods have chitinous opercula but some have nice ones made out of more sturdy aragonite. I know the turbin snails in the genus Turbo are well known for these but I've never researched if other types of gastropods have these as well.






I picked up a number of "cat's eye/dead-man's eye opercula" from the Tapestry Turban (Turbo petholatus) when I was doing coral reef research in the Indo-Pacific. Since we were usually quite remote, many hours or even days from the nearest hospital, we had medical crew on the research vessel and one was always on the dive boat when we were doing research dives. We got to know the doctors and nurses well over the months and I decided to have some fun with one of the doctors. I had found a large opercula similar to those pictured above with a dark green center and rusty white borders. It was large enough (probably 3 cm or so) that I closed one eye and held it in place like a monacle. I turned to the doc pointing to my eye and said that my eye hurt and I thought there was something wrong with it. The momentary confusion and panic was well worth the practical joke. I explained about these opercula and gave it to him as a reminder of my prank. :P


I also encountered a beach on one of the smaller islands in the Jardines de la Reina (Queen's Gardens) along the southern coast of Cuba where the beach was made up of coarse pebbly "sand" that was mainly shell hash, weathered coral pebbles, and about 40% tiny white opercula the size of split peas. I've never seen a beach like that anywhere else again. There must have been an impressive quantity of some gastropods just offshore to produce this density of opercula.






  • I found this Informative 2
Link to post
Share on other sites

@Tidgy's Dad wow I probably would’ve never figured that out on my own :headscratch:. No idea those could fossilize… thanks!


@digit I enjoyed that doctor story :D. This could be turbo. I didn’t find a fossil shell but they’re out there most definitely! Wish mine had that nice green like the opercula you have pictured. 

@automech it went by in a blur! After I found the shark tooth things at least cooled down a bit bc I accomplished the central mission lol. My fam isn’t into fossils unless it’s a mosasaur or megalodon :ironic:. That being said they took interest in these since anything Hawaiian is a little extra special  

  • Enjoyed 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

  • Create New...