Never name a new species of an existing dinosaur genus

I’m still making my way through Brian Curtice’s excellent and detailed post on Greg Paul’s (2025) recent erection of a new titanosaur genus (Curtice 2025), but I just want to comment on this one passing thought of Brian’s:

The species tells me where it was found if named by “Old Timers,” the genus almost can do that if named by “New Kids on the Block” as they almost never add species names to existing genera (recent tyrannosaur excepted ).

The new kids are right.

You should never[1] name a new species of an existing dinosaur genus. Here’s why. Suppose you have two genera, A and B, which are sister taxa in your phylogeny:

 Genus A /  Genus B

Now you discover a new specimen, X, which your phylogenetic analysis says is more closely related to Genus A than than to any other named genus:

 Genus A / / / Specimen X    Genus B

The smart play is to name it genus X. But suppose you say “Oh, but it’s really quite similar to genus A, it can’t be separated at the genus level”, and you instead name it as a new species, A. x. You go merrily on your way congratulating yourself on not being one of those filthy splitters, and all is well until someone else runs a different phylogenetic analysis with more characters, better taxon sampling, a better weighting algorithm, whatever. And it comes out like this:

 Genus A / / /  Specimen X /  Genus B

Now the new author has to say something like “The species x is hereby removed into the genus B yielding the new combination B. x.”

And now your taxon’s name has changed. That’s really bad. The whole purpose of a name is to be a fixed, permanent label that consistently refers to the same thing. But Linnaeus’s terrible mistake, the Linnean binomial, is a “name” that encodes a specific phylogenetic hypothesis, and which implodes when that hypothesis is considered false.

Naming a new species x of a genus A is a nomenclatural enshrining of your phylogenetic hypothethesis that specimen X is more closely related to the genoholotype of genus A than to that of any other genus. It’s a bet that has no upside if you turn out to be right, but makes you look like a dummy if you’re wrong. There is absolutely no need to make such a bet.

Names are for naming things. Phylogenetic analyses are for analysing things. Don’t confuse them. And don’t reify that confusion in nomenclature.,

Note 1. As so often when one writes “never”, we really mean “hardly ever”. I don’t discount the possibility that there may be some very special circumstances when a new species within an existing genus is warranted, but I bet that your example of such a very special circumstance doesn’t qualify.

References

• Curtice, Brian. 2025. Et Tu Ut Te (Titan)? Thoughts on Alamosaurus and more. Fossil Crates, December 12, 2025. https://www.fossilcrates.com/blogs/news/alamosaurus
• Paul, Gregory S. 2025. Stratigraphic and anatomical evidence for multiple titanosaurid dinosaur taxa in the Late Cretaceous (Campanian-Maastrichtian) of southwestern North America. Geology of the Intermountain West 12:201-220., doi: 10.31711/giw.v12.pp201-220.

Source: https://svpow.com/2026/01/16/never-name-a-new-species-of-an-existing-dinosaur-genus/