Labocania aguillonae - Teratophonein tyrannosaurid from Mexico

[Kikokuryu]

"A New Tyrant Dinosaur from the Late Campanian of Mexico Reveals a Tribe of Southern Tyrannosaurs"

https://www.mdpi.com/2813-6284/2/4/12

 

Rivera-Sylva, H.E.; Longrich, N.R. A New Tyrant Dinosaur from the Late Campanian of Mexico Reveals a Tribe of Southern Tyrannosaurs. Foss. Stud. 2024, 2, 245-272. https://doi.org/10.3390/fossils2040012

[Kikokuryu]

Normally, a paper of a tyrannosaurid from Mexico, and from a clade that’s difficult to obtain in North American deposits is not going to be super relevant information to collectors. However, there is a curious bit in the phylogeny that includes indeterminate tyrannosaurid remains from both the Aguja and Two Medicine Formation that has affinities with Teratophoneini according to this study.

It’s a very cool discovery, but this effectively spells disaster for collectors where Campanian tyrannosaurid teeth are already neigh impossible to distinguish between the standard Gorgosaurus and Daspletosaurus. It may simply be a fool’s errand to try to distinguish tyrannosaur teeth if there are this many contemporary taxa living in close proximity to each other. However, we do have Labocania aguillonae teeth for comparison. They have a pinched base similar to that of teeth referred to Nanotyrannus lancensis, though a lot more pronounced.

Quote

The teeth are unusual in having deep grooves or fullers running up the crown. As a result, the base of the crown is distinctly pinched in ventral view, giving it a figure-8 shape. This feature is unusual among theropods. A slight pinching of the crown is seen in dromaeosaurids, but tyrannosaurids typically have either a rectangular section to the crown or, in the case of T. rex, an inflated, ovoid section. The strong pinching and fullers are uniquely shared with Labocania anomala (IGM 5307), consistent with the referral of these teeth to Labocania.

Rivera-Sylva, H.E.; Longrich, N.R. A New Tyrant Dinosaur from the Late Campanian of Mexico Reveals a Tribe of Southern Tyrannosaurs. Foss. Stud. 2024, 2, 245-272. https://doi.org/10.3390/fossils2040012

Edited Thursday at 12:34 AM by Kikokuryu

[North]

Interesting. Makes me think thing or two.

Do we have any information about teeth of L. anomala?

Edited Thursday at 07:50 AM by North

[Kikokuryu]

1 hour ago, North said:

Intwresting. Makes me think thing or two.

Do we have any information about teeth of L. anomala?

Yes? Well, the original paper that describes Labocania anomala in 1974 (which is a fairly long time ago) by Ralph E. Molnar, while it doesn't have any photos of the teeth, does describe them. Longrich himself I believe has gone to look at the original holotype of Labocania anomala, but I think there is a separate study being done on the type species which is why you don't see photos of it in this paper. Not having photos of the teeth kind of sucks.

 

The description of the teeth is on page 1013 of the Molnar paper. There is some ambiguity in this description. One of the reasons people thought Labocania was not a tyrannosauroids was that the teeth were not described as being the classic D-shape (specigically U-shape in tyrannosaurs), which is why some people suggested a carcharodontosaurian. I've heard abelisaurid as well, but I feel that is way off mark, and that abelisaurids convergently have vaguely similar D-shape premaxillary teeth.

Quote

Teeth of both maxillary and premaxillary form have been found associated with this material. One of the isolated teeth of premaxillary form (i.e. either a premaxillary or anterior dentary tooth) matches, except in size, the premaxillary tooth of Deinonychus antirrhophus... the teeth of premaxillary form of Labocania differ from the premaxillary teeth of typical tyrannosaurids in that those of Labocania are not so markedly U-shaped in cross-section. The teeth of maxillary form do not differ from those of the tyrannosaurids. There are ten to fourteen denticles per 0.5 cm on the anterior carinae of the isolated teeth (of maxillary aspect) and eleven to fourteen on the posterior carinae... posterior carina of one tooth in situ. This was one of the dentary teeth, and the figure is twelve denticles per 0.5cm.

https://www.jstor.org/stable/1303299

 

Molnar, Ralph E. “A Distinctive Theropod Dinosaur from the Upper Cretaceous of Baja California (Mexico).” Journal of Paleontology, vol. 48, no. 5, 1974, pp. 1009–17. JSTOR, http://www.jstor.org/stable/1303299. Accessed 26 Sept. 2024.

Edited Thursday at 04:12 AM by Kikokuryu

[North]

3 hours ago, Kikokuryu said:

Yes? Well, the original paper that describes Labocania anomala in 1974 (which is a fairly long time ago) by Ralph E. Molnar, while it doesn't have any photos of the teeth, does describe them. Longrich himself I believe has gone to look at the original holotype of Labocania anomala, but I think there is a separate study being done on the type species which is why you don't see photos of it in this paper. Not having photos of the teeth kind of sucks.

 

The description of the teeth is on page 1013 of the Molnar paper. There is some ambiguity in this description. One of the reasons people thought Labocania was not a tyrannosauroids was that the teeth were not described as being the classic D-shape (specigically U-shape in tyrannosaurs), which is why some people suggested a carcharodontosaurian. I've heard abelisaurid as well, but I feel that is way off mark, and that abelisaurids convergently have vaguely similar D-shape premaxillary teeth.

https://www.jstor.org/stable/1303299

 

Molnar, Ralph E. “A Distinctive Theropod Dinosaur from the Upper Cretaceous of Baja California (Mexico).” Journal of Paleontology, vol. 48, no. 5, 1974, pp. 1009–17. JSTOR, http://www.jstor.org/stable/1303299. Accessed 26 Sept. 2024.

Its always sad when there is no pictures from the material, but good that there is description.

[rocket]

37 minutes ago, North said:

Its always sad when there is no pictures from the material, but good that there is description.

 

I would never trust a description without pics, sometimes subjective what has been written...

As a reviewer, I have always rejected papers that had no photos but only descriptions or drawings.

You should only really trust the original photo, the description could be very good or..., very subjective

 

[North]

1 hour ago, rocket said:

 

I would never trust a description without pics, sometimes subjective what has been written...

As a reviewer, I have always rejected papers that had no photos but only descriptions or drawings.

You should only really trust the original photo, the description could be very good or..., very subjective

 

True. I would prefer to have my own conclusion from pictures. Its never same without.

[Kikokuryu]

Longrich's video on the Labocania aguillonae paper.

 

[DD1991]

Although the cladogram in the Labocania aguillonae shows Alioramini outside Tyrannosauridae and Nanotyrannus as a basal tyrannosaurid, those results contradict the tyrannosaurine nature of the clade Alioramini and the fact that the Nanotyrannus holotype and Jane are immature tyrannosaurine specimens. 

 

The recovery of Labocania as a member of the tyrannosaurine clade Teratophoneini basically settles questions over the systematic placement of this genus because a number of theropod experts noticed that Labocania was similar to abelisaurids in having thick frontals and a reclining quadrate, and the presence of thick frontals in members of Teratophoneini demonstrates that a few tyrannosaurine tyrannosaurids convergently evolved thick frontals with abelisaurids and the carcharodontosaurid Shaochilong.