Sturgeon + Paddlefish = Sturddlefish?

Kaldy et al. 2020 bring us results of a mistake.
These gene scientists ‘accidentally’ mixed sturgeon (Figs. 1, 2) eggs with paddlefish (Fig. 3) sperm. Genetic hybrids (Figs. 4, 5 ) resulted.

From the abstract
“Two species from the families Acipenseridae and Polyodontidae, Russian sturgeon (Acipenser gueldenstaedtii, Brandt and Ratzeberg, 1833; functional tetraploid; Fig. 1) and American paddlefish (Polyodon spathula, Walbaum 1792, functional diploid; Fig. 2) were hybridized. The hybridization was repeated using eggs from three sturgeon and sperm from four paddlefish individuals.

Survival in all hybrid family groups ranged from 62% to 74% 30 days after hatching. This was the first successful hybridization between these two species and between members of the family Acipenseridae and Polyodontidae. Many individuals reached a size of approximately 1 kg by the age of one year under intensive rearing conditions.”

Figure 1. Acipenser, a sturgeon. I don’t see differences between the hybrids and this illustration created years ago.

Figure 2. Skull of Pseudoscaphorhynchus. Note the mouth is created by the lacrimal and surangular, not the maxilla and dentary, which are tooth-bearing bones in more derived fish.

Figure 3. Skull of Polyodon from a diagram published in Gregory 1938, plus a dorsal view and lateral photo. Note the real jaws here.

Figure 4. Photos from Kaldy et al. 2020, re-scaled to the scale bars. Note the growth of the snout with size/age. Note the hybrids really do look like sturgeons, not paddlefish. No

Chondrosteus nests between sturgeons and paddlefish
in the large reptile tree (LRT, 1709+ taxa). So the sturgeon and paddlefish are not sisters.

1. Sturgeons retain osteostracan armor. Paddlfeish lack armor.
2. Sturgeons lack jaws. Paddlefish have jaws.
3. Hybrids have armor and lack jaws, as in sturgeons, not paddlefish.

Figure 5. Principal component analysis (PCA) plot for morphometric characters from Kaldy et al. 2020. Note the strong skew toward sturgeon traits in the hybrids.

Kaldy et al. provided a principal component analysis
for sturgeon traits, paddlefish traits and hybrid traits (Fig. 5). Their PCA showed a strong tendency toward sturgeon traits in the hybrid juveniles, as reflected in the morphology of theiir photos (Fig. 4).

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References
Kaldy J et al. (12 co-authors) 2020. Hybridization of Russian Sturgeon (Acipenser gueldenstaedtii, Brandt and Ratzeberg, 1833) and American Paddlefish (Polyodon spathula, Walbaum 1792) and Evaluation of Their Progeny. Genes 2020, 11, 753. https://www.mdpi.com/2073-4425/11/7/753

Online NYTimes article (click to view):

The above photo looks weird, but this specimen is little to no different from typical sturgeons.
Article by Annie Roth, NY Times writer, July 15, 2020

Figure x. Subset of the LRT, focusing on fish for July 2020.