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  1. ThePhysicist

    Juvenile T. rex

    From the album: Hell Creek / Lance Formations

    Tyrannosaurus rex Hell Creek Fm., Garfield Co., MT, USA This is from the right maxilla of a juvenile individual (note the lingual wear). Art by RJ Palmer
  2. Perhaps one of the most exciting scientific papers in a while about the genetic diversity of the Tyrannosaurid genus Tyrannosarus itself (the genus that includes the famous and well documented T-rex) was just announced and published (or at least the abstract of it)!!! Image Credit: Dalman et al. 2023 (abstract) and the Society for Vertebrate Paleontology (SVP). https://vertpaleo.org/wp-content/uploads/2023/10/2023_SVP_Program-Final-10032023.pdf At the Society for Vertebrate Paleontology's annual meeting for 2023, Paleontologists Dr. Sebastian Dalman, Dr. Philip J. Currie, and seven other experienced Paleontologists and experts on the Tyrannosaurid theropod dinosaurs published an abstract on October 21, 2023 about a new species of Tyrannosaurus (Tyrannosaurus mcraensis) from the Hall Lake Formation dating 72 Million Years ago to the Campanian-Maastrichtian Cretaceous of what is now New Mexico!!! This not only gives insights on the origins of the genus Tyrannosaurus, but validates previous hypothesis over the years (at least since 2013) that a unique giant Tyrannosaur from southern Larmidia (now Western North America) that lived during the Campanian-Maastrichtian Cretaceous!!! Names given to this animal over the years include Alamotyrannus brinkmani and Tyrannosaurus brinkmani. A Digital Reconstruction of the Tyrannosaurus species Tyrannosaurus mcraensis and it's size compared to an average Human, April 2022. Image Credit: Artist LancianIdolatry https://twitter.com/LancianIdolatry/status/1511016414252978182 This is especially true given for how long the debate has been raging on the Validity ofThe species Tyrannosaurus mcraensis was when fully grown the same size of the averaged size adults of the later Tyrannosaurus rex from the later Maastrichtian Cretaceous. By the look of things with the Paper and the experienced paleontologists and Tyrannosaur experts who authored it, it seems just by looking at its abstract it will be be far more through and accurate than the recent Gregory S. Paul Paper from 2022 and maybe even prove the validity of the debate Tyrannosaur species Tyrannosaurus vannus from the 70-66 Million Years ago dated Javelina Formation of what is now Texas. But I'm wondering if anyone has more information on this study and the potential of it's results?
  3. I want to show the first examples of tyrannosauridae teeth in my collection. They are on their way to me, so now I can show only seller's pics. First come a tyrannosauridae tooth from Bissekty formation (Timurlengia euotica) it's size - 7 cm
  4. Tyrannosaurus rex (Osborn, 1905) Late Cretaceous, c. 67 Ma Hell Creek Formation, Isabel, Dewey Co., South Dakota, USA. It has been a dream since childhood to own a Tyrannosaurus rex tooth and my dream came true with this recent acquisition of a gorgeous T. rex 1.5” dentary tooth.
  5. ThePhysicist

    Juvenile Tyrannosaurus rex Tooth

    Identification Though smaller than many imagine T. rex teeth to be, this is indisputably one. It is characteristically robust, and has chisel-shaped denticles with similar denticle densities on each carina.1 Those qualities support its identification as a Tyrannosaurid, and with the locality information confirming it originated from the Hell Creek formation, this must be T. rex. Comments Like most isolated theropod teeth, this is a shed tooth, likely lost during feeding.2 This specimen has exquisite preservation with the enamel texture sharply retained as in life. It however has minor weathering with possible feeding wear at the tip, light root etching, and the base of the tooth has been lightly smoothed possibly by tumbling in an ancient river (enamel is harder so it wouldn't have weathered as much as other portions of the tooth). References 1. Smith, Joshua B. “Heterodonty in Tyrannosaurus Rex: Implications for the Taxonomic and Systematic Utility of Theropod Dentitions.” Journal of Vertebrate Paleontology, vol. 25, no. 4, 2005, pp. 865–87. JSTOR, http://www.jstor.org/stable/4524513. 2. Fiorillo, Anthony R., and Philip J. Currie. “Theropod Teeth from the Judith River Formation (Upper Cretaceous) of South-Central Montana.” Journal of Vertebrate Paleontology, vol. 14, no. 1, 1994, pp. 74–80. JSTOR, http://www.jstor.org/stable/4523546.
  6. Tyrannosauridae Dinosaur diversity was unique in the Western and Eastern areas of the North American Continent during the Late Cretaceous era around 95-66 Million Years ago) as a result of a seaway the cut the continent in two (creating the continents of Laramidia (now Western North America) and Appalachia (now Eastern North America)). By the Maastrichtian stage of the Cretaceous 68 Million Years ago, the seaway decreased in size and a land bride formed between Laramidia and Appalachia. https://deeptimemaps.com/western-interior-seaway/ This is around the same time Tyrannosaurus rex emerged in Laramida and other Tyrannosauridae including the smaller Dryptosaurus lived in Appalachia. Map of the currently known Tyrannosaurus rex fossil discovery sites Maps of the currently known Maastricthian Tyrannosauridae fossil discovery sites in Eastern North America (not shown on the maps here are Late Cretaceous Tyrannosauridae fossil sites in South Carolina and North Carolina) https://paleobiodb.org/navigator/ What I'm wondering is even with this land bridge formed, what prevented Tyrannosaurus from colonizing the Eastern portion of North America during the Maastricthian Cretaceous? If it didn't prevent this, has there been any fossils found in the Eastern portion of North America that belong to the Tyrannosauridae genus Tyrannosaurus?
  7. Along with an interest in Pennsylvanian fish diversity, I've also had an interest (like many others studying Paleontology) in the diversity of Dinosaur genera during the Cretaceous era (particularly the Theropod diversity in North America during the Maastrichtian period 72.1-66 Million years ago). Compared to the preceding Campanian period (83.6-72.1 Million years ago), I've noticed there is a slightly less number of known Tyannosauridae genera in Western North America (at the time a separate continent known as Laramidia). I've come up with a list of confirmed known and possible Tyrannosauridae genera during the Maastrichtian period in Western North America and Eastern North America. Eastern North America (at the time a separate continent known as Appalachia) Dryptosaurus Donoho Creek Formation Tyrannosauridae genera (possibly Appalachiosaurus) https://palaeo-electronica.org/content/2018/2123-appalachia-biogeography Chronister well (Ripley Formation) Tyrannosauridae genera 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 Western North America (Laramidia) Tyrannosaurus Rex Nanuqsaurus (Prince Creek Formation) Albertosaurus (more early Maastrichtian to around 68 Million Years ago) ?"Alamotyrannus" (could also be a species of Tyrannosaurus - ?Tyrannosaurus brinkmani) ?"Daspletosaurus sp. (Horseshoe Canyon Formation) (specimen CMN 11315) (more early Maastrichtian to around 68 Million Years ago) https://cdnsciencepub.com/doi/10.1139/cjes-2014-0072 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7079176/ I'm wondering if this is an accurate list, why is there a dip in Tyrannosauridae diversity in Eastern and Western North America after the Campanian (was it a result of the Deccan Volcanic eruptions in India around the same time, at least for Western North America (if this theory is current) the Native Western North American Tyrannosaur genera being outcompeted by the Eurasian ancestors of Tyrannosaurus Rex arriving in North America via a land bridge during the late Campanian Early Maastrichtian, or both), the status on the taxonomic validity of Alamotyrannus, was Nanuqusaurus present during the later part of the Maastrichtian, and did Albertosaurus and Tyrannosaurus Rex ever come into direct contact with one another?
  8. Something that has been baffling me for a while is the fate of the European genera of Tyrannosauridae after the Mid Cretaceous. Multiple Tyrannosauridae genera including Proceratosaurus (Tyrannosauridae, England, Great Britain, Middle Jurassic (166 Million Years ago): ironically one of the earliest known Tyrannosauridae from the fossil record currently known), Eotyrannus (Tyrannosauridae, Wessex Formation, Isle of Wight, Early Cretaceous (136.4-125.45 Million Years ago)) and an unnamed Tyrannosauridae genera from Germany (Early Cretaceous (130.0-122.5 Million Years ago)) are known from Mesozoic deposits in Europe dating from the Middle Jurassic up to the Early Cretaceous. Holtz, Thomas (December 1998). "A new phylogeny of the carnivorous dinosaurs". Gaia. 15: 5–61. https://www.geol.umd.edu/~tholtz/gaiaphyl.pdf Hutt, Stephen & Naish, Darren & Martill, David & Barker, Michael & Newbery, Penny. (2001). A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research. 22. 227-242. 10.1006/cres.2001.0252. https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=242e6d5f962a143900f3c8d2ff5eb20d6fe7482b K.-P. Lanser and U. Heinhofer. (2015). Evidence of theropod dinosaurs from a Lower Cretaceous karst filling in the northern Sauerland (Rhenish Massif, Germany). Palaeontologische Zeitschrift 89:79-94 https://www.semanticscholar.org/paper/Evidence-of-theropod-dinosaurs-from-a-Lower-karst-Lanser-Heimhofer/94860c34dedf8ac6d65759af9725ae76402eef59 But by the Late Cretaceous around 70-66 Million Years ago, they are absent from the fossil record in the region. Instead, the top predators of the region at the time seem to be Abelisaurs and large pterosaurs. Isasmendi, Erik & Torices, Angelica & Canudo, José & Currie, Philip & Pereda Suberbiola, Xabier. (2022). Upper Cretaceous European theropod palaeobiodiversity, palaeobiogeography and the intra‐Maastrichtian faunal turnover: new contributions from the Iberian fossil site of Laño. Papers in Palaeontology. 8. 10.1002/spp2.1419. https://onlinelibrary.wiley.com/doi/full/10.1002/spp2.1419 I’m curious on what could have caused this faunal turnover (especially since that between the Ealy Cretaceous (at the time of the known records of Tyrannosauridae from Europe) and the Late Cretaceous, Europe was basically a series of islands) or if they were still present in Europe during the Late Cretaceous and specimens have yet to be found or properly categorized? What do you guys think?
  9. The two most prominent hypothesizes on the direct evolutionary origin of perhaps the most famous Theropod Dinosaur from the fossil record, Tyrannosaurus Rex (Tyrannosauridae, Late Cretaceous (68-66 Million Years ago)) are what I call the Laramidia and Asian Origins. The Laramidia origin (named after the region of the Western North America which was a separate Continent during most of the Late Cretaceous and home to a vast amount of dinosaurs including Tyrannosaurus rex) hypothesizes that Tyrannosaurus rex is the direct descendent of and evolved from slightly older North American Tyrannosaurids like Daspletosaurus (Tyrannosauridae, Late Cretaceous (79.5-74 Million Years ago)). Warshaw, Elías & Fowler, Denver. (2022). A transitional species of Daspletosaurus Russell, 1970 from the Judith River Formation of eastern Montana. PeerJ. 10. e14461. 10.7717/peerj.14461. https://www.researchgate.net/publication/365746599_A_transitional_species_of_Daspletosaurus_Russell_1970_from_the_Judith_River_Formation_of_eastern_Montana The Asian origin hypothesizes that Tyrannosaurus’s direct ancestor was a Tyrannosaurid from Asia. This supported by how closely related the Asian Tyrannosaurid Tarbosaurus (Tyrannosauridae, Late Cretaceous (70 Million Years ago)). This hypothesis further elaborates that a that the Asian Tyrannosaurids arrived in Western North America via a land bridge between what is now Eastern Russia and Alaska around 73-72 Million Years ago. On arrival, theses Asian Tyrannosaurids outcompeted and caused the extinction of most of the Native Tyrannosaur species of Laramidia (including Albertosaurus (Tyrannosaurid, Late Cretaceous (71-68 Million Years ago)), creating conditions allowing for the emergence of the genus Tyrannosaurus. Brusatte, Stephen & Carr, Thomas. (2016). The phylogeny and evolutionary history of tyrannosauroid dinosaurs. Scientific Reports. 6. 20252. 10.1038/srep20252. https://www.nature.com/articles/srep20252 Takasaki R, Fiorillo AR, Tykoski RS, Kobayashi Y (2020) Re-examination of the cranial osteology of the Arctic Alaskan hadrosaurine with implications for its taxonomic status. PLoS ONE 15(5): e0232410. https://doi.org/10.1371/journal.pone.0232410 https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0232410 Both hypotheses have points that are supported by the fossil record, but still don’t fill all the gaps in answering the question of the direct origin of the genus Tyrannosaurus. There is however another hypothesis I have pondered over for at least the past few months which could fill in some (if not all) the gaps to this question. It is the Hybrid Speciation Origin hypothesis. The Hybrid Speciation Origin hypothesis basically states that after a land bridge formed between Eurasia and Laramidia during the Late Campanian stage of the Cretaceous (73-72 Million Years ago) and the Asian Tyrannosaurids arrived in Laramidia, certain individuals of a Asian Tyrannosaurid genus breed with a species of a genus of Native Laramidia Tyrannosaurid (likely a direct descendent of Daspletosaurus). Enough of these inter-genus breeding events occurred that a new Tyrannosaurid genus distinct from its parent species (and genuses) emerged around 68 Million Years ago, Tyrannosaurus. I will admit this would be extremely difficult to prove, but I do believe it could be a valid hypothesis. It corroborates the many similarities in skeletal structure Tyrannosaurus shares (and how closely related it is phylogenetically) with the Asian Tyrannosaurid Tarbosaurus and the skeletal structure similarities and general body shape it shares with Daspletosaurus. Image Credit: https://www.nature.com/articles/srep20252 Brusatte, Stephen & Carr, Thomas. (2016). The phylogeny and evolutionary history of tyrannosauroid dinosaurs. Scientific Reports. 6. 20252. 10.1038/srep20252. https://www.nature.com/articles/srep20252 Warshaw, Elías & Fowler, Denver. (2022). A transitional species of Daspletosaurus Russell, 1970 from the Judith River Formation of eastern Montana. PeerJ. 10. e14461. 10.7717/peerj.14461. https://www.researchgate.net/publication/365746599_A_transitional_species_of_Daspletosaurus_Russell_1970_from_the_Judith_River_Formation_of_eastern_Montana Stein, Walter W.; Triebold, Michael (2013). "Preliminary Analysis of a Sub-adult Tyrannosaurid Skeleton from the Judith River Formation of Petroleum County, Montana". In J. Michael Parrish; Ralph E. Molnar; Philip J. Currie; Eva B. Koppelhus (eds.). Tyrannosaurid Paleobiology. Bloomington: Indiana University Press. pp. 55–77. Currie, P.J. (2003). Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontologica Polonica 48 (2): pp. 191–226. https://www.app.pan.pl/archive/published/app48/app48-191.pdf I am interested in how the tyrannosaurid species Nanuqusaurus (Tyrannosaurid, Late Cretaceous (70-68 (likely also to 66) Million years ago), the Daspletosaur Tyrannosaurid specimen RMDRC 2002.MT-001 “Sir William”, and the Tyrannosaurid specimen CM 9401 could factor into the validity of the hybrid speciation hypothesis. I hold no illusions in thinking this hypothesis is not going to be controversial. But I do think it could be semi plausible. What do you guys think?
  10. ThePhysicist

    Juvenile T. rex tooth

    From the album: Hell Creek / Lance Formations

    Interesting blue color near the base, and some feeding wear at the tip of this immature Tyrannosaurid tooth.
  11. ThePhysicist

    Tyrannosaurid premaxillary tooth

    "That some of these teeth are mammalian incisors there can be but little doubt..." - O. C. Marsh1 This kind of incisor-like ("incisiform") tooth was originally thought to have belonged to a large, Cretaceous mammal. Later discoveries revealed that these teeth were actually the front teeth ("premaxillary teeth") of Tyrannosaurs - and are now known as a hallmark of their clade, Tyrannosauroidea (along with fused nasals). Closely-spaced, parallel grooves on bones suggest that Tyrannosaurs used these teeth to selectively scrape meat from bone2. Identification Tyrannosaurid premaxillary teeth have a "D"-shaped cross section, with the lingual face flattened, and often have an apicobasal ridge on the midline of the lingual face. In more technical language, "...premaxillary teeth bear lingually rotated mesial and distal carinae forming a salinon cross-section at mid-crown height, and a highly convex labial aspect as in tyrannosauroids generally. In mesial/distal views carinae are sinuous, transitioning from lingually convex near the base to lingually concave approaching the occlusal surface. Carinae terminate prior to reaching the root/crown juncture. Mesial and distal aspects of the crown are depressed, yielding a weakly hourglass-shaped cross-section at the crown base... The carinae lack serrations [likely ontogenetically variable]... As in other tyrannosauroids, teeth exhibit a pronounced lingual ridge"3. Most of the current literature supports only one Tyrannosaurid species in the Hell Creek formation, Tyrannosaurus rex, a hypothesis subject to change in light of new evidence. Comments This tooth has no discernible antemortem wear. The collector appears to have applied some preservative coating, giving the enamel a slightly sharper gloss. Given the size, this is from a very young animal (smaller than "Jane", BMRP 2002.4.1). References 1. Marsh, O.C., 1892, "Notes on Mesozoic vertebrate fossils", American Journal of Science, 44: 170-176 2. David W.E. Hone and Mahito Watabe, "New information on scavenging and selective feeding behaviour of tyrannosaurs", Acta Palaeontologica Polonica 55 (4), 2010: 627-634 doi: http://dx.doi.org/10.4202/app.2009.0133 3. Zanno, L., Tucker, R.T., Canoville, A. et al. Diminutive fleet-footed tyrannosauroid narrows the 70-million-year gap in the North American fossil record. Commun Biol 2, 64 (2019). https://doi.org/10.1038/s42003-019-0308-7
  12. ThePhysicist

    Tyrannosaurid premaxillary tooth

    "That some of these teeth are mammalian incisors there can be but little doubt..." - O. C. Marsh1 This kind of incisor-like ("incisiform") tooth was originally thought to have belonged to a large, Cretaceous mammal. Later discoveries revealed that these teeth were actually the front teeth ("premaxillary teeth") of Tyrannosaurs - and are now known as a hallmark of their clade, Tyrannosauroidea (along with fused nasals). Closely-spaced, parallel grooves on bones suggest that Tyrannosaurs used these teeth to selectively scrape meat from bone2. Identification Tyrannosaurid premaxillary teeth have a "D"-shaped cross section, with the lingual face flattened, and often have an apicobasal ridge on the midline of the lingual face. In more technical language, "...premaxillary teeth bear lingually rotated mesial and distal carinae forming a salinon cross-section at mid-crown height, and a highly convex labial aspect as in tyrannosauroids generally. In mesial/distal views carinae are sinuous, transitioning from lingually convex near the base to lingually concave approaching the occlusal surface. Carinae terminate prior to reaching the root/crown juncture. Mesial and distal aspects of the crown are depressed, yielding a weakly hourglass-shaped cross-section at the crown base... The carinae lack serrations [likely ontogenetically variable]... As in other tyrannosauroids, teeth exhibit a pronounced lingual ridge"3. Most of the current literature supports only one Tyrannosaurid species in the Hell Creek formation, Tyrannosaurus rex, a hypothesis subject to change in light of new evidence. Comments This tooth exhibits some antemortem wear at the apex (pictured), on the carinae, and near the base of the lingual apicobasal ridge. Given the size, this is from a juvenile animal (smaller than "Jane", BMRP 2002.4.1). References 1. Marsh, O.C., 1892, "Notes on Mesozoic vertebrate fossils", American Journal of Science, 44: 170-176 2. David W.E. Hone and Mahito Watabe, "New information on scavenging and selective feeding behaviour of tyrannosaurs", Acta Palaeontologica Polonica 55 (4), 2010: 627-634 doi: http://dx.doi.org/10.4202/app.2009.0133 3. Zanno, L., Tucker, R.T., Canoville, A. et al. Diminutive fleet-footed tyrannosauroid narrows the 70-million-year gap in the North American fossil record. Commun Biol 2, 64 (2019). https://doi.org/10.1038/s42003-019-0308-7
  13. ThePhysicist

    Tyrannosaur premaxillary tooth

    From the album: Hell Creek / Lance Formations

    This kind of incisor-like ("incisorform") tooth was originally thought to have belonged to a large, Cretaceous mammal. Later discoveries revealed that these teeth were actually the front teeth ("premaxillary teeth") of Tyrannosaurs - and are now known as a hallmark of their clade, Tyrannosauroidea. Closely-spaced, parallel grooves on bones suggest that Tyrannosaurs used these teeth to scrape meat from bone. Given the size, this is from a very young animal. Should Nanotyrannus be valid, then this should be considered an indeterminate Tyrannosaurid.
  14. ThePhysicist

    Tyrannosaur premaxillary tooth

    From the album: Hell Creek / Lance Formations

    This kind of incisor-like ("incisorform") tooth was originally thought to have belonged to a large, Cretaceous mammal. Later discoveries revealed that these teeth were actually the front teeth ("premaxillary teeth") of Tyrannosaurs - and are now known as a hallmark of their clade, Tyrannosauroidea. Closely-spaced, parallel grooves on bones suggest that Tyrannosaurs used these teeth to scrape meat from bone. Given the size, this is from a juvenile animal (smaller than "Jane"). Should Nanotyrannus be valid, then this should be considered an indeterminate Tyrannosaurid.
  15. ThePhysicist

    T. rex tooth

    From the album: Hell Creek / Lance Formations

    It's remarkable that the minute features of this tooth can be preserved with such clarity after 66 million years!
  16. ThePhysicist

    Tyrannosaurid vs Dromaeosaurid

    From the album: Hell Creek / Lance Formations

    As a theropod tooth aficionado, I thought it useful to compare two families present in the Hell Creek Formation. They become increasingly difficult to distinguish as they get smaller, but this graphic presents some features which may be used to differentiate them on two similarly-sized exceptional specimens. Keep in mind there is some variability due to position, ontogeny, etc., so it's beneficial to study more than one tooth for each family.
  17. ThePhysicist

    Worn T. rex tooth (annotated)

    From the album: Hell Creek / Lance Formations

    Not the prettiest tooth, but I very much enjoy fossils like this that demonstrate behavior and tell a story. T. rex and other Tyrannosaurs were unusual among theropods in that they consumed the entire carcass of an animal - bones and all. Most theropod dinosaurs have ziphodont teeth, thin and knife-like, good for cutting muscle from bone. The thick and robust teeth of adult Tyrannosaurs, coupled with their incredible bite force, allowed them to shatter and pulverize bone - even those of the large, formidable herbivores they hunted. Despite the robustness of their teeth, Tyrannosaurs often broke them in the process of biting. It may have been a while before the broken tooth was replaced by a new one, so in the meantime, the broken tooth would continue to accumulate wear. This is one such tooth, a large portion of the tooth was broken off when the animal bit into another dinosaur, and it was still used afterwards for some time before it was replaced. Based on the placement and extension of the carinae to the base of the tooth, and the size, this was an anterior tooth (at the front of the mouth, probably the first dentary tooth) of an adult individual. See Schubert & Ungar (2005) for a discussion on Tyrannosaur tooth wear features (open-access).
  18. ThePhysicist

    Worn T. rex tooth

    From the album: Hell Creek / Lance Formations

    Not the prettiest tooth, but I very much enjoy fossils like this that demonstrate behavior and tell a story. T. rex and other Tyrannosaurs were unusual among theropods in that they consumed the entire carcass of an animal - bones and all. Most theropod dinosaurs have ziphodont teeth, thin and knife-like, good for cutting muscle from bone. The thick and robust teeth of adult Tyrannosaurs, coupled with their incredible bite force, allowed them to shatter and pulverize bone - even those of the large, formidable herbivores they hunted. Despite the robustness of their teeth, Tyrannosaurs often broke them in the process of biting. It may have been a while before the broken tooth was replaced by a new one, so in the meantime, the broken tooth would continue to accumulate wear. This is one such tooth, a large portion of the tooth was broken off when the animal bit into another dinosaur, and it was still used afterwards for some time before it was replaced. Based on the placement and extension of the carinae to the base of the tooth, and the size, this was an anterior tooth (at the front of the mouth, probably the first dentary tooth) of an adult individual. See Schubert & Ungar (2005) for a discussion on Tyrannosaur tooth wear features (open-access).
  19. ThePhysicist

    Juvenile T. rex tooth

    From the album: Hell Creek / Lance Formations

    A young T. rex tooth. The preservation of the enamel is fantastic, and I like the dark hues. The serrations are also in great shape. There is some minor feeding wear on the tip.
  20. ThePhysicist

    Juvenile Tyrannosaur tooth

    From the album: Hell Creek / Lance Formations

    Sold by the BHI as Nanotyrannus lancensis. However, given the uncertain status of Nanotyrannus' validity, I chose to label it as Tyrannosaurid for now. It is interesting to compare to my other small Tyrannosaur teeth of the same/similar position. The base is clearly more compressed than my baby rex tooth (which is also smaller).
  21. ThePhysicist

    Juvenile Tyrannosaur tooth

    From the album: Hell Creek / Lance Formations

    A Tyrannosaur tooth from Eastern Montana. Given the basal "pinching," this would be Nanotyrannus lancensis if it's valid (otherwise it's T. rex). Interesting to compare it to my other small Tyrannosaur teeth. The tip was probably broken after fossilization, but the gouges on the labial face may be inflicted while the tooth was in use. Note that the enamel is well-preserved with sharply resolved texture and is still clear.
  22. ThePhysicist

    T. rex tooth

    Identification This is a classic T. rex tooth. It's clearly Tyrannosaurid by its robusticity, similar serration densities on each carina (mesial carina counted by the "roots" of the denticles as they are completely worn off), and chisel-shaped serrations. Those qualities with its locality and formation mean it must be the one and only. Notes The Crown Height Ratio (CHR) suggests a posterior position (it's short and stout). There's evidence of wear on the tip and mesial carina.
  23. ThePhysicist

    Tyrannosaur tooth

    Identification Tyrannosaur teeth characteristically have similar serration densities on each carina, with chisel-shaped denticles. Though small, this tooth matches those qualities, and doesn't resemble other smaller theropods like Dromaeosaurids. Identified as Cf. T. rex based on its similarity to another, larger tooth in my collection. Notes This tooth is from a juvenile individual. Serration densities illustrated in the above photos. There is a slight pathology (bend) near the tip.
  24. ThePhysicist

    Tyrannosaur

    From the album: Hell Creek / Lance Formations

    Tyrannosauridae (Nanotyrannus-morph) Hell Creek Fm., Powder River Co., MT, USA A classic Nanotyrannus Tyrannosaur tooth: compressed and blade-like. Exceptional preservation, with a minor wear facet near the tip on the lingual side (indicating it's from the left maxilla). I really like the color.
  25. ThePhysicist

    T. rex posterior

    From the album: Hell Creek / Lance Formations

    Tyrannosaurus rex Hell Creek Fm., Fallon Co., MT, USA The CHR suggests a posterior position for this somewhat beat-up T. rex tooth.
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