Thursday, March 19, 2026

I'm not touching Stygivenator.

So, Nanotyrannus is now a valid taxon. However, a weird new discussion seems to be. emerging. It's around Stygivenator. Now, I first heard of this taxonomic name in Longrich and Saitta (2024). Apparently, that paper suggested that some of the Nanotyrannus specimens were Stygivenator. This included BMRP 2002.4.1 (Jane"), NCSM 40000 (formerly the "Dueling Dinosaurs" specimen/"Bloody Jane"), LACM 28471, and a few others (pp. 50-51 Table 6). Paul (2025) regurgitated this argument (pp. 98, 118-119, and 128). Stygivenator was first named by Olshevsky and Ford (1995), and the holotype was LACM 28471 (p. 98). He also placed NCSM 40000 (formerly NCMNABM) as possibly being Stygivenator (pp. 118-119). Despite that, I believed that Stygivenator was a synonym of Nanotyrannus.

When I contacted Sebastian Dalman to get his opinion on Nanotyrannus being valid again, he told me to wait for a new paper that he was a part of to come out. Now, Longrich et al., (2026) came out. Dalman is one of the authors. They described a new Tyrannosaurinae specimen, which could've even been a specimen of Tyrannosaurus sp. Cool! The origin of Tyrannosaurus seems to have come from "the Campanian-Maastrichtian of southern Laramidia," (Abstract, Material: Comparisons and Phylogenetic analysis, Discussion, para. 8-10 and 13; Figure 5). However, the authors also believe that Stygivenator was valid. In fact, Stygivenator was two species: S. lethaeus (Nanotyrannus lethaeus) and S. molnari. Interestingly, Nanotyrannus is a sister taxon to Stygivenator and Khankhuulu. All of these taxa seem to be outside the tyrannosauridae clade, while the new tyrannosaurinae specimen is a sister taxon to Tyrannosaurus mcraensis and T. rex (Figure 5):
Longrich seems to be a huge fan of Stygivenator. I saw a blog post that he wrote stating that it was a valid taxon (Nick Longrich, Blog, 11/1/25, The Return[?] of Stygivenator). Aside from Stygivenator being definitively valid, there are other stuff in that post that I do agree with. 

Now, this is my blog so what is my opinion on this matter? To be honest, I don't want to touch Stygivenator. I'm perfectly fine with Nanotyrannus being a valid taxon, and an eutyrannosaur. IF Stygivenator is valid, then fine. IF not, then fine. However, I want more specimens to be discovered and a very in-depth description detailing the apomorphies that separate Stygivenator from Nannotyrannus. As of right now, I'm placing Stygivenator as a synonym of Nanotyrannus. Do I believe that "There's absolutely no way that Stygivenator exists," as other people have already stated? No. I'll keep an open mind. Plus, I think we might discover new tyrannosauroid taxa that existed in the Late Maastrichtian of North America. I'm cautious about Stygivenator because we only have one complete specimen of Nanotyrannus. It clearly displays characteristics seen in other Nanotyrannus specimens. Let's not place it as a separate taxon before we find more specimens. I'm more swayed by having two species of Nanotyrannus, or three species of Dryptosaurus, being valid for now. Maybe the future will prove Stygivenator to be valid, but I'm going to wait this one out. 

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