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I have adopted the moniker of TheDinosaurHeretic after Robert T. Bakker's influential 1988 book titled The Dinosaur Heresies. As such, I have a particular interest in dinosaurs and I'd like to expand the information about them. I am particularly interested in tyrannosaurid dinosaurs, and as such, will edit the members of that clade accordingly if necessary. I currently run a YouTube channel and Instagram account under the same name.
Larson (2005; 2013) lists the following characteristics as substantial in separating Nanotyrannus from Tyrannosaurus[1][2] (subsequent studies have suggested that these characteristics are simply ontogenetic [3][4][5]).
Glenoid features lateral component, similar to that of Ornithomimus velox (BHI 1266) and a dissociated scapula attributed to Albertosaurus sarcophagus (TMP 86.144.1) (the lateral component of the glenoid is not present in LACM 28471).
Peculiar phalanx I-1 anatomy and presence of phalanx III-1 on both hands, the former character similar to Dryptosaurus aquilunguis, and the latter character being unique to Nanotyrannus if it's not a fractured metacarpal.
Disproportionately large manual unguals, larger than that of adult Tyrannosaurus rex.
Arms in juvenile specimens significantly larger than adult T. rex.
Cervical vertebrae proportionately longer in Nanotyrannus than adult T. rex.
Strongly curved furculae, which is dorsoventrally compressed.
Antorbital fossa dips slightly below the lateral surface of the maxilla, forming a shallow depression.
Ventral antorbital maxillary ridge (VAMR) rises along the dorsal margin of the posteroventral extension of the maxilla, above the posterior alveoli. VAMR is half of the dorsoventral dimensions of the posteroventral maxillary extension. VAMR extends past the last alveolus and under the jugal as it articulates to the maxilla. Constriction at the base of the VAMR forms the ventral border of the antorbital fossa (similar to a condition seen in G. sp. [TCM 2001.89.1]) (In T. rex, the antorbital fossa is very deep and is representative of the youngest individuals; the VAMR disappears before the maxilla/jugal suture; ventral borders of the antorbital fossa and antorbital fenestra are only partially bound by the antorbital maxillary ridge, an identical condition in Tarbosaurus bataar and is replicated in juvenile specimens).
Maxillary fenestra does not touch anterior or posterior borders of antorbital fossa and is centered in the shelf bounded by the dorsal, ventral, and anterior edge, and posteriorly by the antorbital fenestra, closely resembling one of the defining characteristics of G. sp. (TCM 2001.89.1) and Appalachiosaurus montgomeriensis (RMM 6670) (this is contrasted by the condition seen in T. rex and T. bataar, where the maxillary fenestra contacts the anterior and posterior borders of the antorbital fossa. This is true of juvenile T. bataar as well).
Vomer resembles that of G. sp. (TCM 2001.89.1).
In lateral view, the dorsal edge of the ascending process of the quadratojugal preserves a central and posterior notch (a central notch is present in G. sp. [TCM 2001.89.1] but not T. rex. TCM 2001.89.1 doesn't preserve the posterior notch, however, detailed illustrations of the G. sp. specimen show that a posterior notch is present. A posterior notch is absent in T. rex).
Lacrimal is T-shaped with pronounced cornual process (preserved in G. sp., A. sarcophagus, and Daspletosaurus torosus, but a character not present in T. rex or T. bataar, which possess a 7-shaped lacrimal with no cornual process).
The dorsal articular surface of the quadrate is ball-shaped, resembling that of D. torosus and A. sarcophagus (BHI 6234) (The quadrate of T. rex [BHI 3033] has a double articular surface, adjoined by a saddle, corresponding to the double sockets of the squamosal, similar to that of G. sp.).
Teeth incisiform, with a small first maxillary tooth (as is in G. sp. and A. sarcophagus, but not present in T. rex).
Mediolaterally compressed tooth rows.
Maxillary tooth positions in N. lancensis varies from 15 (present in CMNH 7541 and right maxilla of BMRP 2002.4.1 [BMRP 2006.4.4 doesn't preserve a skull; LACM 28471 and Bloody Mary are inconclusive]) to 16 (left maxilla of BMRP 2002.4.1), 17 tooth positions in both preserved dentaries (T. rex preserves from 11-12 maxillary tooth positions and 12-13 dentary tooth positions, and Tyrannosaurus "x" preserves 12-13 maxillary tooth positions and 13-14 dentary tooth positions).
Dentary tooth row of BMRP 2002.4.1, with 17 tooth positions, is approximately the same length as BHI 6439, with 13 tooth positions.
Subnarialis foramen, the opening for V-2 cranial nerve (sensory nerve for the upper lip, showing enhanced tactile sensory ability), is bounded completely by the maxilla and is associated with a deep fossa projecting anteroventrally from the foramen, a similar condition seen in Sinraptor dongi and G. sp., the latter possessing a large exit foramen at approximately the same site as N. lancensis, accompanied by a deep anteroventrally facing fossa (the exit foramen is bounded by both the premaxilla and maxilla in T. rex. This condition is similarly seen in Allosaurus fragilis and proposed to be in Alligator mississippiensis, however, the exit foramen in the later is bound completely by the maxilla).
Diverticula of the respiratory system may be represented by a deep central depression in the medial aspect of the postorbital. A similar depression can be seen in G. sp. and D. torosus. A. sarcophagus has a less developed depression, and the fossa is absent in T. rex and T. bataar.
Large pneumatic foramina on the central portion of the quadratojugal, and is unique to N. lancensis.
Central portion of the anterior aspect of the squamosal has pleurocoel-like fossa, a condition similarly seen in D. torosus and A. sarcophagus (central portion of the anterior aspect of the squamosal in T. rex is perforated by large pneumatophore, which is completely absent in N. lancensis. T. bataar closely resembles the pneumatophore in T. rex, as does in G. sp., except much smaller.
Lateral lacrimal pneumatopore in N. lancensis is large, encompassing half the width of the vertical ramus and half the height of the dorsal ramus; there are multiple perforations, the number increasing with age. This increase in the number of perforations is consistent with the ontogeny of Struthio camelus (the lateral lacrimal pneumatophore is small, approximately a quarter of the width of the vertical ramus and a quarter the height of the dorsal ramus).
In medial view, a dorsal margin of a thin ridge that descends the vertical ramus diagonally, and terminates at the ventral anterior border of the vertical ramus is present in N. lancensis (a similar ridge is seen in T. rex, with evidence of a medial lacrimal pneumatophore).
The ventral surface at the edge of a large pneumatopore located at the ectopterygoid is not bound by a thick lip. This is similarly demonstrated in A. montgomeriensis and A. sarcophagus (a thick lip is preserved in T. rex, T. bataar, and D. torosus).
The anterolateral jugal pneumatopore, located at the posterior ventral corner of the antorbital fossa, and is a defining characteristic of tyrannosaur taxa, is open dorsally in N. lancensis (in T. rex, it opens anterolaterally).
Nanotyrannus lancensis (article started by User:Dinoguy2) - article that has been expanded upon via slight corrections; inclusion of Possibly valid characteristics chapter.
^Larson (2005). "A case for Nanotyrannus." In "The origin, systematics, and paleobiology of Tyrannosauridae", a symposium hosted jointly by Burpee Museum of Natural History and Northern Illinois University.
^Larson P (2013), "The validity of Nanotyrannus Lancensis (Theropoda, Lancian - Upper Maastrichtian of North America", Society of Vertebrate Paleontology: 73rd annual meeting, Abstracts with Programs, p. 159.
^Yun, C (2015). "Evidence points out that "Nanotyrannus" is a juvenile Tyrannosaurus rex"". PeerJ PrePrints. 3: e1052. doi:10.7287/peerj.preprints.852v1.{{cite journal}}: CS1 maint: unflagged free DOI (link)
^Carr, T.D. (1999). "Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria)". Journal of Vertebrate Paleontology. 19 (3): 497–520. doi:10.1080/02724634.1999.10011161.
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