Elephant 'shark'?

The species Callorhinchus milii is often referred to as 'elephant shark', but it does not belong to the bona fide taxonomic group of sharks, a part of the class Elasmobranchii that also includes rays, torpedoes, sawfishes, and skates.

Panel H is elephant fish Callorhinchus milii

All photos were taken by S. Kuraku for this review

Of course, we all respect the choice of Callorhinchus milii, with a relatively small genome size as well as early efforts to make its genome sequences available. In one of our past publications, we included:

'More than a decade ago, the elephant fish, Callorhinchus milii, a member of the Holocephali that comprises approximately 50 species, was chosen for whole-genome sequencing because of its small genome size (Venkatesh et al., 2005). Since then, molecular comparative studies on vertebrates have largely relied on the C. milii genomic sequences as representative of cartilaginous fishes (Venkatesh et al., 2014), but the low fecundity and accessibility of live specimens have been a limitation. C. milii is often referred to as elephant 'shark' (or ghost 'shark'), but true sharks belong to the subclass Elasmobranchii that comprises approximately 1,200 species.'

(Hara et al., Nat Ecol Evol 2018)

So, how can we call them? A less confusing English common name for Callorhinchus milii should be 'elephant fish' or 'elephantfish' (without a hyphen). One of my collaborators in Australia insists on this common name because they locally call so. I respect a common way of calling the species in/near the species' natural habitats. In the case of Callorhinchus milii, the natural habitats are waters around Australia and New Zealand. You could also refer to the resourceful review by Dr. Brittany Finucci and her collaborators (Finucci et al., 2020) using the same English common name. You could say that it is still confusing that they collectively call species in Chimaeriformes 'ghost sharks', though. Likewise, they all do not belong to the taxon Elasmobranchii ... .

I happen to have found the name 'elephant fish' in the poster of the eggcase hunting project by Shark Trust (see below). Very importantly in this context, this poster was made for the general public in Australia for the identification of different species from the shape of eggcases. I suggest reconsidering the choice of English common names in your next scientific manuscripts about this species at least, if any.

A part of the poster mentioned above

Find more fascinating visual materials and stories at Shark Trust websites