Alleged cross between a sturgeon and a paddlefish

[Peter Nyikos]

These two fish are among the most primitive of extant ray-finned fishes,
and are covered in books about vertebrate paleontology for that reason.

In Carroll's gold-standard book, _Vertebrate Paleontology and Evolution_.,
they are in two different Linnean families, *Acipenseridae* for the sturgeon
and *Polydontondidae* for the paddlefish. They look very different on the outside,
and have different feeding habits and apparatuses.

Nevertheless, in Quora, the following item appeared:

"What is a weird case of 2 separate species that can breed together?"
https://qr.ae/pKBOal

In 2019 a Hungarian lab mixed sperm from an American paddlefish (Polyodon spathula) and eggs from a Russian sturgeon (Acipenser gueldenstaedtii), hoping that the presence of the sperm would induce parthenogenesis in the eggs without fertilising them. As far as we know the lines leading to these two fish diverged in the Jurassic, 184 million years ago.

To the researchers’ amazement the eggs and sperm combined, and some of the eggs developed into living hybrid fish they’ve called sturddlefish. We don’t know if they’re fertile yet, as they take a long time to reach maturity.


The accompanying picture looks like a sturgeon to me -- no features of a paddlefish that I can see.

Possibly a case of parthenogenesis, is my tentative assessment.


Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
https://people.math.sc.edu/nyikos

[erik simpson]

I don't have a copy of Carrol (1990), but Linnean classification is very
out of date. both paddlefish and sturgeons are members of the clades
Actinopterygii -> Actinopteri -> Chondrostei.

https://en.wikipedia.org/wiki/Actinopterygii

[Peter Nyikos]

On Friday, January 26, 2024 at 2:01:22 PM UTC-5, erik simpson wrote:
> On 1/26/24 10:34 AM, Peter Nyikos wrote:
> > These two fish are among the most primitive of extant ray-finned fishes,
> > and are covered in books about vertebrate paleontology for that reason.
> >
> > In Carroll's gold-standard book, _Vertebrate Paleontology and Evolution_.,
> > they are in two different Linnean families, *Acipenseridae* for the sturgeon
> > and *Polydontondidae* for the paddlefish.

Pardon the "hiccup": that should simply be *Polyodontidae*.

>> They look very different on the outside,
> > and have different feeding habits and apparatuses.
> >
> > Nevertheless, in Quora, the following item appeared:
> >
> > "What is a weird case of 2 separate species that can breed together?"
> > https://qr.ae/pKBOal
> >
> > In 2019 a Hungarian lab mixed sperm from an American paddlefish (Polyodon spathula) and eggs from a Russian sturgeon (Acipenser gueldenstaedtii), hoping that the presence of the sperm would induce parthenogenesis in the eggs without fertilising them. As far as we know the lines leading to these two fish diverged in the Jurassic, 184 million years ago.
> >
> > To the researchers’ amazement the eggs and sperm combined, and some of the eggs developed into living hybrid fish they’ve called sturddlefish. We don’t know if they’re fertile yet, as they take a long time to reach maturity.
> >
> >
> > The accompanying picture looks like a sturgeon to me -- no features of a paddlefish that I can see.
> >
> > Possibly a case of parthenogenesis, is my tentative assessment.

Or it could just be a case of ignorant reporters garbling the description
of what was told to them -- or embellishing it to get a big "scoop."
I've seen some egregious cases in the past.

> I don't have a copy of Carrol (1990), but Linnean classification is very
> out of date.

So is Usenet, it seems. Yet we are sticking with it.

The Linnean classification has an extra dimension that is lacking
in the clades-only classification: a rough "ballpark" measure of the
degree of disparity within them and between them.

> both paddlefish and sturgeons are members of the clades
> Actinopterygii -> Actinopteri -> Chondrostei.

That says nothing about degree of disparity. We are members of the
sister group of {Tiktaallik, Elpistostege}, but their disparity is of the
Linnean family level, whereas the disparity of its sister group is that of a superclass.

> https://en.wikipedia.org/wiki/Actinopterygii

I am comparing it to something within the other branch
of Osteichthyes:

https://en.wikipedia.org/wiki/Sarcopterygii

Specifically, it has to do with the subclade Stegocephali:

"Contrary to the old usage of this term, the Stegocephali refers to a clade in this scheme. This concept of the clade Stegocephali was chosen to substitute for the name Tetrapoda by those who sought to restrict Tetrapoda to the crown group.[8] As such, it encompasses all presently living land vertebrates as well as their early amphibious ancestors."
--https://en.wikipedia.org/wiki/Stegocephali

The first phylogenetic tree in the linked article has some nice pictures
of the animals at the base of Stegocephali, and you can make out
our group and its sister group {Tiktaalik, Epistostege} at a glance.

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

Univ. of South Carolina at Columbia
http://people.math.sc.edu/nyikos