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11-05-2020, 05:01 AM( This post was last modified: 12-28-2020, 08:18 AM by DinoFan83 )
Tratayenia is an extinct genus of megaraptoran tyrannosauroid theropod known from remains found in Neuquen, Argentina. The type and only species, Tratayenia rosalesi, was described in March 2018, but was unearthed in 2006, with a preliminary report on the remains being published by Juan Porfiri in a 2008 abstract suggesting that it may have been a large basal tetanuran related to carcharodontosaurids. The holotype (MUCPv-1162) consists of a fragmentary but well-preserved skeleton with an articulated series of dorsal and sacral vertebrae, two partial dorsal ribs, much of the right ilium, and pubis and ischium fragments. Tratayenia was a large to gigantic theropod, with the juvenile or subadult holotype being estimated at 8 to 11 meters in length and 1.8 to 4.7 tonnes in weight based on comparison to more complete relatives, and a much larger specimen that may have belonged to the genus (MCF-PVPH 416) potentially indicating sizes of up to 13.6 meters and 8.9 tonnes. Like most other megaraptorans, Tratayenia probably had large arms and claws as well as a large amount of skeletal pneumaticity. Tratayenia is one of the geologically youngest megaraptorans yet found, and is also the largest-bodied carnivorous animal named from the Bajo de la Carpa Formation, reinforcing the hypothesis that megaraptorids were apex predators in southern South America from the Turonian through to at least the Santonian or early Campanian, following the extinction or decline of carcharodontosaurids. If this hypothesis holds, this could show that more primitive tyrannosauroids went on a similarly evolutionary path to their Laurasian cousins after carcharodontosaurids went extinct or severely declined in both Laurasia and Gondwana, taking over the niche of apex predators and reaching sizes that made them among the largest theropods yet found. Tratayenia lived in the Bajo de la Carpa Formation alongside many lizards and turtles, the snake species Dinilysia patagonica, many birds such as Patagopteryx deferrariisi, a diverse amount of crocodylomorphs and many dinosaurs such as the abelisaurid Viavenator exxoni and the alvarezsaurid Alvarezsaurus calvoi, the former of which it was likely to be dominant over.
Size comparison of the holotypes of Tratayenia and Viavenator. Tratayenia taken from Porfiri et al. 2018 and Viavenator taken from Filippi et al. 2016.
11-07-2020, 01:26 AM( This post was last modified: 11-24-2020, 04:32 AM by DinoFan83 )
For anyone wondering about the large size estimate for Tratayenia in the OP, here's the methods behind how I got it that big, taken from the carnivorous dinosaurs thread.
Quote:In discussions about which theropods were among the largest known, megaraptorans are almost never present. With Siats possibly not being a member of the group, Osteoporosia being unreliable to the extreme, and Chilantaisaurus most likely not being much larger than 2-3 tonnes, even the largest members tend to be left out of discussions to make way for more famous giant theropods like giant tyrannosaurids, giant carcharodontosaurids, and giant spinosaurids. However, this is very likely unjustified given the size of some specimens that are thus far unnamed (but may belong to known species*); these are very likely elligible to be among the largest tyrannosauroids of all, right up there with the famous giant tyrannosaurids.
Case in point: MCF-PVPH 418.
Reported in Coria et al. 2004 as well as Baiano and Coria (2018), it is the centrum of an anterior dorsal vertebra, and is 11 cm long. The authors suggested this bone could belong to the biggest megaraptoran specimen ever found, and it seems that if the megaraptoran with the most complete series of dorsal vertebrae in 1 animal (Aerosteon) is anything to go by, they were right on the money. The Theropod Database lists the 4th dorsal (which is the most similar dorsal that Aerosteon preserves to the giant dorsal in question and is therefore most likely the best to size up the giant dorsal with) as 7.1 cm long - substantially smaller than that of MCF-PVPH 418. And Aerosteon itself is no slouch sizewise - it would have been anywhere from 8.3 meters (PWNZ3R-Dragon) to 9.5 meters (Sereno et al. 2008) and 1.8 tonnes (PWNZ3R-Dragon's skeletal) to 3 tonnes (Thomas Holtz, the estimation is rhino size giving a mean of 3 tonnes in a range of 2-4), giving us a mean of of 8.8 meters long and 2.4 tonnes.
So how gigantic exactly, you may ask, would this giant megaraptoran then be?
Going off of an Aerosteon this size having a 7.1 centimeter long anterior dorsal, MCF-PVPH 418 ends up 13.6 meters long and 8.9 tonnes in mass. That's definitely keeping pace with the large tyrannosaurids of the Late Cretaceous, and is in fact a serious contender to significantly outsize even the largest of them, being 2.9 tonnes larger than the average T. rex and a full tonne heavier than my mean estimation of 7.9 tonnes for Sue (which was, to my knowledge, previously tied with David Hone's T. zhuchengensis dorsal as the largest tyrannosauroid known thus far). It also stacks up favorably with other giant theropods from South America, being very similar in size to my estimations of the average sizes for known specimens of Giganotosaurus and Mapusaurus/Giganotosaurus roseae, and seems to be even larger than another giant carcharodontosaurid, the 7+ tonne Tyrannotitan, when going on known specimens. Finally, this giant dorsal seems to be significantly bigger than any abelisaurid or ceratosaur from South America so far, so with all the above in mind I think we can safely consider this specimen among the largest of South American theropods assuming geometric similarity with Aerosteon is a safe bet. Do note, however, that there is a lot of margin for error until a more complete skeleton is found - no estimation for this animal is to be taken as definitive for the time being given the sparse remains.
If this is anything to go by, it seems that, contrary to popular belief, the largest tyrannosauroids weren't necessarily just the derived tyrannosaurids.
*It should be noted that MCF-PVPH 418 comes from the Bajo de la Carpa Formation, the same rocks that produced another large-bodied megaraptoran, Tratayenia. The holotype of Tratayenia is similar in size to the holotype of Aerosteon going by the measurements at the Theropod Database, but the holotype was not fully grown so it could be that MCF-PVPH 418 is an adult specimen for Tratayenia. This cannot be confirmed or disproved until there is overlap in material (there is currently none given that Tratayenia preserves no anterior dorsals), but I find it likely to be the case given the already reasonably large size of the Tratayenia holotype, it not being fully grown, and the difficulty 2 species of megaraptoran would have coexisting. If this theory is correct, this would most likely make Tratayenia the largest known tyrannosauroid based on known specimens, seemingly larger than even the largest derived tyrannosaurids as was gone over above, and among the largest known theropods of all. To have very large megaraptorans in South America is not surprising in the least - they seem to have already been dominant over their major competitors (the abelisaurids) after the extinction or decline of carcharodontosaurids, and there was nothing stopping them to get big as the carcharodontosaurids had. I can only imagine what a fierce animal this megaraptoran have been - quite fast for its size, deadly jaws, and huge claws. And that's all on an animal the size of a large elephant.
