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

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. 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
>
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