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As a freshmen in College, I did a little extra credit report for my geology class about a controversial topic - Tyrannosauroidea diversity in the Southern Hemisphere during the Jurassic-Early Late Cretaceous periods. I was quite surprised at the amount of specimens I found. This diversity likely was the result of an early spread of the early tyrannosaur group Pantyrannosauria into Africa, Eurasia, and North America during the Jurassic and diversified once the land connecting these continents spread out more. Most of these species lived during the Early Cretaceous, though one or two exceptions might have lasted into the Early Late Cretaceous. I've created a list of known of the species and specimens which I would like to share on the forum (let me if there are any examples I'm missing or should add): South America Santanaraptor (Romualdo Member of the Santana Formation) (Early Albian, Cretaceous period 112.6-109.0 million years ago) Specimen: MN 4802-V (partial skeleton) http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=67712 Tyrannosauroidea indet. (Rio do Peixe Group of the Sousa Formation) (Berriasian to the Berriasian, Cretaceous period 145.5-130.0 million years ago) Specimen: NA http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=58791 https://www.researchgate.net/publication/309717524_As_localidades_com_rastros_fosseis_de_Tetrapodes_na_America_Latina Tyrannosauroidea indet. (Serra da Galga Member of Marília Formation) (Late Maastrichtian, Cretaceous Period, 70.0-66.0 million years ago) Specimen: CPP 449 (partial tooth) https://www.researchgate.net/publication/270524259_Theropod_teeth_from_the_Marilia_Formation_late_Maastrichtian_at_the_paleontological_site_of_Peiropolis_in_Minas_Gerais_State_Brazil (above paper initially described specimen, identification as possible Tyrannosauroidea in science direct paper) https://www.sciencedirect.com/science/article/abs/pii/S0031018220303151 Africa (Madagascar) Tyrannosauroidea indet. (Isalo Illb Formation) (Bathonian, Jurassic period 167.7-164.7 million years ago) Specimen: MSNM V5819 (partial tooth) http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=55391 https://www.researchgate.net/publication/257651210_First_description_of_theropod_remains_from_the_Middle_Jurassic_Bathonian_of_Madagascar Australia Timimus hermani (Otway Group of Eumeralla Formation) (Late Aptian, Cretaceous period 122.5-109.0 million years ago) Specimens: NMV P186303 (limb: left femur), NMV P186323 (limb: left femur of juvenile individual), QM F34621 (Pedal phalanx III-1) http://www.paleofile.com/Dinosaurs/Theropods/Timimus.asp http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=57099 Tyrannosauroidea indet. (Otway Group of Eumeralla Formation) (Late Aptian, Cretaceous period 110.0 million years ago) Specimen: NMV P186069 (Pubis bone) Possible Specimen: ?NMV P186046 (Pubis bone) https://www.researchgate.net/publication/42589187_A_Southern_Tyrant_Reptile https://www.sciencedaily.com/releases/2010/03/100325143045.htm

So, after watching a video that Peter Larson posted on Instagram about nanotyrannus, I was pretty convinced that it is a valid genus. That got me wondering. Where does it fit in the tyrannosaur family tree? Is it more related to Tyrannosaurus rex, or another tyrannosaur? I saw an article that was trying to prove that Nanotyrannus was, instead of being in tyrannosauridae with animals like tyrannosaurus and tarbosaurus, it was in dryptosauridae with dryptosaurus and appalachiosaurus. I'm very curious about everyone else's opinions but I myself am rather convinced. links: Pete's post: https://www.instagram.com/tv/CjoNNdojfjp/?igshid=YmMyMTA2M2Y= Nanotyrannus article: http://psdinosaurs.blogspot.com/2021/08/evidence-of-subadult-nanotyrannus.html?m=1

I recently read that the only skeleton currently known of Appalachiosaurus was of a juvenile, and the adult animal was significantly bigger. The juvenile skeleton was about 21 feet long, and the animal likely weighed 1,300 pounds. This skeleton is about the size of a juvenile Tyrannosaurus rex (using the "Jane" specimen for scale, BMRP 2002.4.1) and, this raises a question in my mind. Is it possible that Appalachiosaurus montgomeriensis would have attained adult sizes close to what we see in adult specimens of Tyrannosaurus rex? And as such, could we classify it as a megatheropod? Of course there are several other factors in this, such as age, growth stages, and environmental pressure that the animal may have experienced in life.

In a previous post, I discussed if Tyrannosaurus rex (Tyrannosaur, Western North America) (Late Cretaceous 68-66 Million Years ago) was able to colonize Eastern North America as the Western Interior Seaway retreat by the early Maastrichtian (I received excellent feedback from other four members, notably @Troodon, that this was prevented by the KT Mass Extinction event 66 Million Years ago). As a result, I don't believe Tyrannosaurus rex was able to effectively colonize Eastern North America (as far as I'm currently aware). However, looking over some records of Late Cretaceous Tyrannosaur fossils, I do believe that a Tyrannosaurid (Yes a Tyrannosaurid) was able to colonize part of Eastern North America in the area of what is today Chronister well, Bollinger County, Missouri! Not much is known about this Tyrannosaur genera, but here is the info I could find on it! Unnamed Tyrannosauroidea genus (Tyrannosaur) (McNair Sand Member of the Ripley Formation-Missouri, US, North America) (Late Cretaceous, 70-66 Million Years ago) (Size unknown) http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&taxon_no=38606&max_interval=Cretaceous&country=United States&state=Missouri&is_real_user=1&basic=yes&type=view&match_subgenera=1 https://www.lakeneosho.org/Ozarks/Chronister2.html https://www.sos.mo.gov/CMSImages/Publications/symbols/dinosauressay.pdf Photographs of the Chonister well Tyrannosaur specimens have also been tricky to find, the only ones I've found were shown during an August 2016 Science in St. Louis Seminar series lecture by Geologist Dr. Micheal Fix, Ph.D., Associate Teaching Professor, Department of Physics of University of Missouri-St.Louis titled Monster in the Hollow: The Story of Missouri's Ozark Dinosaurs. The presentation also showed a photograph of a decent sized Dromeaosaurid tooth from the same site in Missouri!

The Tyrannosaur Dinosaurs (Tyrannosauroidea) inhabited North America from 152 Million Years ago during the Late Jurassic era up until 66 Million Years ago during the Late Cretaceous era. https://www.app.pan.pl/article/item/app20110141.html However, there is a relatively large geologic gap between the time of the Late Jurassic to the Santonian-Campanian stages of the Cretaceous (when the the oldest known Tyrannosaurid Lythronax (Late Creteaceous, 81.9-81.5 Million Years ago) emerged) in terms of the number of Tyrannosauroidae confirmed in North America. However, this doesn't mean they were completely absent from the Continent. Rather, they remained small to mid sized predators under the shadow of Large Carnosaurs up until the Cenomanian-Turnonian extinction event 93-94 Million years ago, which the tyrannosaurs filled the role of Apex Predator in most terrestrial ecosystems by the Campanian stage of the Cretaceous. The Tyrannosaur geologic gap between the Late Jurassic and Santonian Cretaceous is also not completely empty and several confirmed Tyrannosauroidea are known from this time period in North America. I've created a list of known Tyrannosauroidea species and specimens from the Aptian-Santonian Cretaceous of North America which I would like to share on the fourtm (let me know if there are any examples I'm missing or should add): Unnamed Cloverly Formation Tyrannosauroid (Tyrannosaur – Cloverly Formation, Wyoming, US, North America) (Early Cretaceous, 108 Million Years ago) (Based on Specimen FMNH PR 2750, likely grew up to 1.2 meters (3.9 feet) in length) https://www.tandfonline.com/doi/abs/10.1080/08912963.2010.543952 https://www.researchgate.net/profile/Lindsay- Zanno/publication/229287579_On_the_earliest_record_of_Cretaceous_tyrannosauroids_in_western_North_America_Implications_for_an_Early_Cretaceous_Laurasian_interchange_event/links/0fcfd50089dd8f3955000000/On-the-earliest-record-of-Cretaceous-tyrannosauroids-in-western-North-America-Implications-for-an-Early-Cretaceous-Laurasian-interchange-event.pdf Unnamed Wayan Formation Tyrannosauroid (Tyrannosaur – Wayan Formation, Idaho, US, North America) (Early Late Cretaceous, 100.6-97.8 Million Years ago) (Based on Specimen IMNH 2251/53975, grew up to 1.2 meters (3.9 feet) in length) https://bioone.org/journals/journal-of-paleontology/volume-96/issue-6/jpa.2022.42/A-partial-tyrannosauroid-femur-from-the-mid-Cretaceous-Wayan-Formation/10.1017/jpa.2022.42.full Unnamed Lewisville Formation Tyrannosauroid (Tyrannosaur - Woodbine Group Lewisville Formation, Texas US, North America) (Late Cretaceous (100-95 Million Years ago)) (Based on Specimens DMNH 2013-0701701 and SMU 77218, grew up to 2.7-4.8 meters (8.8-15 feet) in length) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8796713/ Moros intrepidus (Tyrannosaur – Cedar Mountain Formation, Utah, US, North America) (Early Cretaceous (96.4 Million Years ago)) (Grew up to 1.2 meters (3.9 feet) in length) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6385174/ Suskityrannus hazelae (Tyrannosaur – Moreno Hill Formation, New Mexico, US, North America) (Early Cretaceous, 93.5-89.3 Million Years ago) (grew up to 3 meters (9.8 feet) in length) https://www.pure.ed.ac.uk/ws/files/82474043/82473554._Brusatte._AAM.pdf

A while back, I was researching the number of likely Tyrannosauroidea dinosaurs that inhabited the Southern Hemisphere (I know this is a very controversial subject) in the Early Cretaceous for an extra credit research paper I was doing for my freshmen year college geology class. As I was looking for data for the paper, I found an unusual data entry on the paleontological database website fossilworks.org - It lists Tyrannosauridae remains from Jurassic Madagascar. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=55391 The specimen MSNM V5819 (consisting of a partial tooth) was apparently found in Mahajanga, Madagascar at the Bathonian aged Isalo Illb Formation (dating 167.7-164.7 million years ago) in 2003. S. Maganuco, A. Cau, and G. Pasini (2005) First description of theropod remains from the Middle Jurassic (Bathonian) of Madagascar. Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, 146(2):165-202 https://www.researchgate.net/publication/257651210_First_description_of_theropod_remains_from_the_Middle_Jurassic_Bathonian_of_Madagascar (You can read the actual paper with this above link). Here is also two photographs from the paper of the specimen MSNM V5819 The authors of the paper (which I must say did a really good job with the research and paper itself) state that a healthy degree of caution must be given in assigning MSNM V5819 to Tyrannosauroidea. Still, if this is indeed correct, It would be one of the earliest members of Tyrannosauroidea, with the only currently known older Tyrannosauroidea taxon being Proceratosaurus of England. The Specimen MSNM V5819 is maybe even older than Kileskus of Russia, Guanlong of China, and Aviatyrannus of Portugal. Still, the only currently known specimen is a single tooth, MSNM V5819, and I'm not 100% certain this represents a member of Tyrannosauroidea? What do you guys think?