10 years of Rhinodipterus

Let me tell you about my favourite fossil lungfish.

Rhinodipterus is a long-snouted, tooth-plated lungfish known from the Mid-Late Devonian Period (roughly 390-360 million years ago). There were a handful of species of Rhinodipterus known from throughout Europe described during the mid 20th Century. However, a new specimen unearthed in 2008 from the Gogo Formation in Australia sparked my involvement and interest in this lungfish.

The Gogo Formation is particularly rich in lungfish fossils and this new find represented the 11^th described species from this one locality. Most equivalent deposits may have just one or sometimes two species present, but clearly the lungfish were very diverse on the ancient Gogo reef! And interestingly, this European genus (Rhinodipterus) had for the first time appeared in a different part of the world, all the way over in Australia. This is something we refer to as ‘palaeobiogeographic distribution’. I named the new species Rhinodipterus kimberleyensis, to reflect the location where this fossil was found (the Kimberley region of northern Western Australia).

* CLEMENT, A. M. (2012) A new species of long-snouted lungfish from the Late Devonian of Australia, and its functional and biogeographic implications. Palaeontology 55, 51-71.

Alice at Gogo in 2008.

Tim Sendon, who scanned the specimen at the ANU CT Lab.

Aside from being a new species, the most interesting thing about Rhinodipterus are certain features of its skeleton that are missing from other lungfish at Gogo. Rhinodipterus has cranial ribs which suggests it may have been able to breathe air! Cranial ribs are mobilized during the air gulping action in living lungfish and so their presence (as well as a suite of other features) are used to infer this ability in fossil forms. While we know all living lungfish can breathe air, it is finds such as these that help us pinpoint when this feature first evolved in the fossil lineage.

* CLEMENT, A. M. and Long, J. A. (2010a) Air-breathing adaptation in a marine Devonian lungfish. Biology Letters 6, 509-512.

* CLEMENT, A. M., Long, J. A., Tafforeau, P. and Ahlberg, P. E. (2016b) The dipnoan buccal pump reconstructed in 3D and implications for air breathing in Devonian lungfishes. Paleobiology, 42(2), 289-304.

Rhinodipterus skull and jaw in side view.

The lower jaw of Rhinodipterus.

Furthermore, the specimen of Rhinodipterus that I described was so well preserved and uncrushed, it contained a near complete part of the skull called the braincase. As it’s name suggests, the braincase houses the brain inside the skull. Most lungfish fossils younger than the Devonian become more cartilaginous and don’t tend to fossilise particularly well (unlike bone, which is a harder and more durable material), so this is one of the most advanced fossil lungfish braincases known. Via CT-scanning and computer 3D-modelling I was able to create a virtual ‘endocast’ (mould of the internal cavity) of the braincase. These endocasts can give a lot of information about the early brain evolution in this most wonderful group of fishes (I’m not biased at all!) and help us to reconstruct brain morphology in extinct animals.

* CLEMENT, A. M., and Ahlberg, P. E. (2014) The First Virtual Cranial Endocast of a Lungfish (Sarcopterygii: Dipnoi). PloS One, 19 pp.

* CLEMENT, A. M., Strand, R., Nysjö, J., Long, J. A. and Ahlberg, P. E. (2016c) A New Method for Reconstructing Brain Morphology: Applying The Brain-Neurocranial Spatial Relationship In An Extant Lungfish To A Fossil Endocast. Royal Society Open Science, 8 pp.

As you can see, this single specimen of Rhinodipterus has been very valuable to my research over the years so I thought the least I could do was commemorate it with a blog post. Thank you, Rhino!