Tag: fossils

Super Scanning Spills Stem-tetrapod Secrets

DrAliceClement

(Like the title? I do a love a touch of alliteration…) It’s been a while since I wrote, but our lab group have a couple of recent publications out based on scanning of stem-tetrapod (tetrapodomorph fish) fossils that I’d love to fill you in on.

Firstly, PhD candidate Corinne Mensforth led a study on an enigmatic fish from Antarctica called Koharalepis. This species was first described by Gavin Young and colleagues in the 90s, and in 2018, John Long, Brian Choo and I published a paper based on synchrotron scans of the holotype and only known specimen. However, this was a difficult specimen to image and it had kept many of it’s secrets from us … until now.

Koharalepis jarviki (AMF 54325) fossil specmen (left); being imaged using the ANSTO “Dingo” neutron beam (centre); and a digital segmentation of the skull bones from scan data made in Mimics software (right)

More recently, we have used neutron tomography to scan this fish, a technique which has finally revealed to us much more of the internal features preserved within this fossil that we had been able to see before. This led to Corinne’s paper, “New data on the sarcopterygian Koharalepis jarviki (Tetrapodomorpha; Canowindridae) from the Late Devonian of Antarctica, revealed via synchrotron and neutron tomography” published in the journal Frontiers in Ecology and Evolution in April this year.

It was great to see Koharalepis get a moment in the spotlight, with the media release getting picked up all over the world, including a mention in IFLScience! This was certainly helped by the stunning life reconstruction that our talented Honours student, Tom Turner, created. Just beautiful!!

Tom and Corinne (left), and life reconstruction of Koharalepis jarviki created by Tom Turner (right).

Read more: Remembering Tilly Edinger, the pioneering ‘brainy’ woman who fled Nazi Germany and founded palaeoneurology

NEXT, and keeping on with the theme of high powered scanning of stem-tetrapod fossils, today my long-awaited publication “Ethmosphenoid endocasts elucidate evolutionary braindivergences and interrelationships of stem tetrapods (Sarcopterygii, Tetrapodomorpha)” was published in Papers in Palaeontology, with a co-author list that truly spans the globe. Big thanks to all my co-authors, Richard Cloutier, Oleg Lebedev, Tom Challands, Jing Lu, Joseph Bevitt, Laurent Houle, Shaun Collin, & John Long. This one took a team effort and a long time…

Good times with great collaborators: Alice shown with John Long, Richard Cloutier, Tom Challands, Joseph Bevitt and Jing Lu.
Skull, endocast and sensory canal morphology in 13 Palaeozoic tetrapodomorph taxa. (Image: Alice Clement)

In this work we scaned 13 taxa of stem tetrapods across three families (‘Tristichopteridae’, ‘Osteolepididae’, Megalichthyidae) to examine skull and endocast morphology using Principal Components Analysis. Of note there are some particularly mysterious and otherwise poorly-known species included in this analysis, including some more from Antarctica (Mahalalepis, Platyethmoidia, and a new still unamed fossil), Australia (Owensia), and Russia (Megapomus), alongside other better known species such as Gogonasus and Eusthenopteron.

Our study shows that the internal cranial endocast can be useful to help identify phylogentic affinity (relationships to other species) in forms where that is otherwise difficult to discern. We also deduce that stem tetrapods were likely quite conservative in their palaeoneurology (brain shape), in contrast to what we see in lungfishes, for example.

The scanning data and resultant 3D digital models for both studies are online and can be viewed via their respective projects on MorphoSource: Koharalepis, and Ethmosphenoid endocasts of stem tetrapods.

The enigma from Gogo

DrAliceClement

ENIGMA /ɪˈnɪɡmə,ɛˈnɪɡmə/

noun, a person or thing that is mysterious or difficult to understand.

Since 2011, there has persisted a mysterious specimen known from the Late Devonian Gogo Formation in Australia. Dubbed Cainocara enigma by authors Ken Campbell and Dick Barwick, who first studied it, they published a work entitled “A new unusual Osteichthyan fish from the Gogo Formation, Western Australia“, but considered this single specimen so strange that they could not identify it any further than some kind of bony fish…

Fast forward to 2024, and enter my dedicated and hard-working 3rd year research student, Hannah Thiele, who used CT scans of this, well, BLOB of a fossil (there really is no other way to describe it!) and specialised 3D segmenting software to solve the mystery of just what the enigma really was!

A photo of the enigma from Gogo, housed in the Australian National University fossil collection.

By reconstructing the internal space of this mysterious fossil, Hannah was able to identify a cranial endocast, the space inside the skull that usually houses the brain. In doing so, we could identify features that helped us to orient the specimen correctly and interpret it accurately. This meant we could solve the mystery once and for all!

We deduced that the enigma from Gogo was most likely the poorly-preserved, and heavily-weathered braincase of a lungfish. Exactly which one we don’t know, but something similar to the short snouted forms such as Chirodipterus or Holodipterus.

Hannah, together with myself and colleagues John Long (Flinders) and Joseph Bevitt (ANSTO), published a paper detailing the results earlier this year in the Canadian Journal of Zoology, with “Deciphering Cainocara enigma from the Late Devonian Gogo Formation, Australia“.

Lead author, Hannah Thiele, presenting her results on the Gogo enigma at the CAVEPS meeting in 2025.

If you are keen to read more, see the news article “Missing pieces added to ancient global fish puzzle” published on Scimex. After this work, Hannah continued her study on fish brains at Flinders University, and has now commenced her PhD.

Hello Harajicadectes (is that you grannie?)

DrAliceClement

Meet Harajicadectes, your 380 million year old great, great, great (etc) Grannie.

This fish, which was given the full name Harajicadectes zhumini, was described by myself and other colleagues, published this week in the Journal of Vertebrate Paleontology “A new stem-tetrapod fish from the Middle–Late Devonian of central Australia“.

This is a tetrapodomorph, or tetrapod-like fish, from ancient rock deposits in central Australia. This means this fish is more closely related to tetrapods (amphibians, reptiles & mammals), than it is to a salmon, for example. It bears important features suggesting it was capable of air-breathing, among other things.

Bits and pieces of this fish have been found since the 70s by Gavin Young (ANU) and Alex Ritchie (Australian Museum), among others. However it wasn’t until a Flinders University field trip (with colleagues from ANU & MAGNT) to the area in 2016 uncovered the first complete specimen of Harajicadectes. Finally, all the little bits and pieces could confidently assigned to a single species.

Dr Brian Choo led this paper and is the artist behind the beautiful life reconstruction of this extinct predatory fish from an ancient central Australian river. No doubt there are many more treasures lying in wait to be discovered in the rocks of outback Australia!

Harajicadectes zhumini (Choo et al. 2024). Artwork by Brian Choo.

If you would like to red more about this beastie, find our article published in The Conversation, “A 380-million-year old predatory fish from Central Australia is finally named after decades of digging.”