Collecting Middle Triassic fish near Sydney

[izak_]

We were recently granted access to a terrific site south of Sydney. This quarry extracts Ashfield Shale for the manufacturing of bricks and has been operating for many decades, some fossils from here housed in the Australian Museum were collected in the 1960s. To my knowledge, nobody has collected here for quite a long time, so we were excited to have a look!

The area is mapped as Bringelly Shale, but I think the lower section of the pit is actually Ashfield Shale. The upper section of the pit is a finely bedded sandstone and shale rather than the black shale characteristic of the Ashfield Shale. Our focus was in this lower black shale where we looked for ironstone nodules which can contain fish, temnospondyl amphibians, sharks, bivalves, etc. 

 

Here is a nodule where the cross section of a fish can be seen (the thin line just above my pick):

 

As can be seen in this photo, the pit is huge! Much more of it is out of view. My dad and some cars in the background for reference.

 

The back section of the quarry was actively being worked so a lot of fresh and unweathered shale was exposed. This made it hard to spot the nodules we were after since they often split through the middle and blend in with the surrounding shale. Our best luck was in a section alongside the road where a huge wall of shale was presumably exposed many decades ago, allowing the shale to weather away leaving protruding nodules. Unfortunately, many of the nodules had been split through the middle and broken up. 

 

Extracting these nodules from the sheer rock face was very difficult! Fortunately, the quarry manager was super generous and helped us remove some with an excavator. 

 

The next problem was actually removing the nodules in one piece. They aren't like the beautiful ammonite nodules found on the Jurassic Coast, these are filled with vertical fractures and are a nightmare to remove and split open, even when unweathered. A real nightmare to work with! 

 

This rock face yielded some great finds. Lots of smaller nodules contained fish, but one contained a xenacanthid shark and two contained temnospondyl amphibians! The xenacanthid nodule was already mostly gone (probably for many decades) but the characteristic spines and cartilage texture was unmistakeable.

 

Xenacanthid bits:

 

One of the temnospondyl skulls freshly cracked open. This specimen and the other temnospondyl skull are at the Australian Museum currently, will prepare them soon! 

 

On our next visit (yestderday) we came much better prepared. We hired a jackhammer which made short work of the shale, much better than scraping away the surface with the bucket of an excavator. Here is dad working on exposing the rest of one of the temnospondyl nodules (note the markings to help us put it back together when it inevitably broke during the extraction):

 

Here is the same nodule BEFORE we started with the jackhammer (photo taken on the first visit)!

 

Once we got that nodule out, we had a bit of spare time before we had to leave. I had a look in the freshly dug section of the quarry for any nodules we might've missed and found nothing of much interest other than a nodule containing a bivalve coquina. That was until I noticed one more tiny nodule, which was empty. But upon exposing the surrounding shale I noticed some fish! This is highly unusual considering that most of the vertebrate fossils here are found in nodules. The small section of shale I exposed had quite a few fish, all stacked on top of each other. In the same chunk of shale was also a few horsetail stems and a (conifer?) cone. 

 

Here are some in-situ photos of the fish and some after I put them back together at home. The shale is very fragmentary so it was difficult to extract them.

 

Will update soon with better photos of some of our finds!

 

 

[Ludwigia]

You sure are a bunch of lucky ducks being allowed to dig up such treasures! Now I'm looking forward to seeing the end result on that temnospondyl nodule.

[Tidgy's Dad]

Great thread!

Thanks for sharing.

[Fossildude19]

Great report and finds!

Triassic fish are amazing!

Any ID's on these yet?

[RJB]

Absolutely fascinating!!!

 

RB

[jpc]

wow.. great fishes!!!  

 

[Pagurus]

Thanks for sharing your rewarding adventure. All your planning and hard work is paying off with some awesome fish!

[Jeffrey P]

Great! Fantastic finds. Awesome report! Congratulations. Like the rest, I would love to see those prepped. Thanks for sharing.

[Xiphactinus]

Awesome finds! Lots and lots of work. Congrats!

[Notidanodon]

Always love seeing your finds !

[Paul1719]

Those are amazing!!  I was just looking at an article in JVP about Temnospondyls from Terrigal formation ,NSW. In fact they have a picture on the cover of it about to eat one of those fish!!!

[jpc]

3 hours ago, Paul1719 said:

Those are amazing!!  I was just looking at an article in JVP about Temnospondyls from Terrigal formation ,NSW. In fact they have a picture on the cover of it about to eat one of those fish!!!

I just got that in the mail yesterday.  It made me think of this post.

[izak_]

Thank you all! 

 

On 11/14/2023 at 11:38 PM, Fossildude19 said:

Great report and finds!

Triassic fish are amazing!

Any ID's on these yet?

The two species I have names for from here so far Elonichthys armatus and Myriolepis pectinata, not sure on the smaller fish from the black shale. The Ashfield Shale fish were described by Woodward in 1908 so are likely in need of revision!

 

It turns out one of the two temnospondyls we found is actually an Elonichthys. It is about 110cm long, huge when compared to the type of E. armatus which is 65cm. I've never heard of any bony fish this large from the Sydney Basin which is why we first assumed it was a temnospondyl!

I must emphasise how frustrating this was to prepare, hopefully it will explain the poor looking results. It seems to have been preserved in a huge septerian nodule (note the white powdery veins thoughout the specimen), and the rock fractures *everywhere*. Even if a section of the nodule splits nicely, countless small chips of rock often containing parts of the fossil fall away. I managed to keep track of most bits but some are still missing which is super frustrating. The head end is another story entirely, with this part of the nodule exploding into the bucket of the excavator. Many pieces are missing. I'm still working on it but I think the result will be satisfactory despite all these issues! 

 

The front portion of the head split away from the rock so you can see the slightly better preserved 'bottom' side. Note the orbit towards the front of the skull in the second photo.

 

The full specimen. Still need to glue it all together of course! 

 

Edited November 23, 2023 by izak_

[izak_]

Today we brought the big fish into the Australian Museum, the staff seemed quite excited!  

 

 

Nyrie for scale

 

Note the faint impressions of vertebrae in the middle sections. This is better seen with the light at a shallower angle

 

A closeup of the skull

 

The cross sections of teeth can faintly be made out

[Jeffrey P]

That's one big awesome looking fish. Big congratulations. I agree it will look good once fully prepped. Thanks for sharing.

[Paul1719]

Wow! That was one big nodule! I can not even imagine the challenges of prepping that. ….very slowly! Thanks for your posting

[mr.cheese]

Thank you for sharing!

I think the quarry manager has earned a couple of beers for his kindness!

Good work and I enjoyed learning the finer points of seeing a fossil in the rockface to start with.

You have a good eye!

[sixgill pete]

Very nice. Congrats on the fish.