A Juvenile Metatarsal of Cf. Daspletosaurus Torosus: Implications for Ontogeny in Tyrannosaurid Theropods

Yun, Chan-gyu

doi:10.35463/j.apr.2021.02.02

Cited by 4 publications

(2 citation statements)

References 28 publications

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“…Arctometatarsalian third metatarsals (MT III) are triangle-shaped in distal cross-sections (Holtz 1995), with a posterior constriction that forms a ridge (also called a plantar constriction; Snively et al 2004). UALVP 49310 is identifiable as Gorgosaurus MT III by its curving, distally extended posterior constriction., differing from the contemporaneous Daspletosaurus which has a straighter, broader, oblong, and less edge-like constriction distally (Yun 2021).…”

Section: Methodsmentioning

confidence: 74%

Consilient evidence affirms expansive stabilizing ligaments in the tyrannosaurid foot

Surring¹,

Burns²,

Snively

et al. 2022

Vert. Anat. Morph. Palaeo.

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Tyrannosaurid dinosaurs were ecologically unique vertebrates as the sole clade of large terrestrial carnivores (adults >400 kg) in their continent-spanning habitats. Expanded ligaments between metatarsals, inferred by gross morphology of attachment correlates, have been hypothesized to have strengthened their specialized arctometatarsus. We tested the hypothesis of ligament presence with scanning electron microscopy and histological thin sections of putative attachment sites in a third metatarsal of the tyrannosaurid Gorgosaurus libratus, compared with a thin section from the unspecialized metatarsals of the early theropod Coelophysis bauri. In the Gorgosaurus metatarsal, Sharpey´s fibers and rough, pitted surface textures consistent with ligament coalescence occur at expansive distal regions and localized rugosities are ideally located for resisting torsional loading on the foot. Sparser Sharpey’s fibers occur at expected locations in other arctometatarsus-bearing coelurosaurs. In contrast, the Coelophysis metatarsal lacked Sharpey’s fibers or rugosity at the sectioned location, acting as a definitive negative control for identifying these features in tyrannosaurids. With soft-tissue correlates confirmed as ligament entheses, we conclude that tyrannosaurids possessed distinctive and specific ligament attachments to the third metatarsal lacking in other large carnivorous dinosaurs. Histological evidence for extensive distal intermetatarsal ligaments is consistent with greater inferred agility in derived tyrannosaurid dinosaurs than in earlier lineages of large theropods.

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Section: Methodsmentioning

confidence: 74%

Consilient evidence affirms expansive stabilizing ligaments in the tyrannosaurid foot

Surring¹,

Burns²,

Snively

et al. 2022

Vert. Anat. Morph. Palaeo.

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“…Dinosaur fossils are much less common compared to these taxa, often very fragmentary, and typically not identifiable beyond the "family" level. While Demar and Breithaupt (2006) referred some theropod teeth to Daspletosaurus and Saurornitholestes, the referral of small, unserrated tyrannosaurid premaxillary teeth to Daspletosaurus is no longer justified (Yun 2021a), and the teeth of several other dromaeosaurids (e.g., Atrociraptor) are virtually indistinguishable from those of Saurornitholestes (Currie and Varricchio 2004). Consequently, the generic assignments made by Demar and Breithaupt (2006) are doubtful.…”

Section: Introductionmentioning

confidence: 99%

A caenagnathid oviraptorosaur metatarsal from the Mesaverde Formation (Campanian), Wyoming

Yun

Funston

2021

Vert. Anat. Morph. Palaeo.

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A well-preserved left theropod metatarsal I from the Campanian Mesaverde Formation of Wyoming is described and identified as belonging to a caenagnathid, representing the first occurrence of this clade from the formation. The specimen is unique in being relatively small, but featuring a suite of characters (triangular shaft, less constriction between the shaft and the distal condyle, spherical distal condyle) that are seen in larger examples of Caenagnathidae such as Anzu wyliei or “Macrophalangia canadensis”. This suggests that the previously-observed differences in metatarsal I between small and large caenagnathids are not solely the result of allometry, but may represent phylogenetically informative variation. Although limited, this new specimen lends some support to the hypothesis that “Macrophalangia canadensis” does not represent a large Chirostenotes pergracilis. Furthermore, the specimen is important in establishing the presence of caenagnathids within the Mesaverde Formation fauna, in which theropod remains are poorly known.

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Frontal Bone Anatomy of Teratophoneus Curriei (Theropoda: Tyrannosauridae) From the Upper Cretaceous Kaiparowits Formation of Utah

Yun¹

2021

Actapalrom

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A right frontal bone belonging to the tyrannosaurid theropod Teratophoneus curriei from the Campanian Kaiparowits Formation of Utah provides important anatomical information that is useful in understanding tyrannosaurid taxonomy and relationships. Many aspects of its anatomy indicate a subadult ontogenetic status of this individual, as they compare favorably with subadults of other tyrannosaurids such as Daspletosaurus torosus and Tyrannosaurus rex. This is consistent with the previous interpretation that this individual was subadult, based on different cranial bones such as lacrimal or maxilla. It is likely that a previous assessment of the body mass of this individual was underestimated, and it is presumed here that it was most likely around 1000 kg. This description of the frontal anatomy has several implications for previous works on tyrannosaurid cranial anatomy, and information that corrects aspects of our understanding on tyrannosaurid frontal anatomy is provided. Reanalysis of Nanuqsaurus hoglundi, a tyrannosaurid theropod that has similar frontal morphology with Teratophoneus curriei, implies that parts of its diagnosis are problematic and the proposed evidence for the supposed diminutive body size of this taxon is weak.

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A Juvenile Metatarsal of Cf. Daspletosaurus Torosus: Implications for Ontogeny in Tyrannosaurid Theropods

Cited by 4 publications

References 28 publications

Consilient evidence affirms expansive stabilizing ligaments in the tyrannosaurid foot

Consilient evidence affirms expansive stabilizing ligaments in the tyrannosaurid foot

A caenagnathid oviraptorosaur metatarsal from the Mesaverde Formation (Campanian), Wyoming

Frontal Bone Anatomy of Teratophoneus Curriei (Theropoda: Tyrannosauridae) From the Upper Cretaceous Kaiparowits Formation of Utah

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