A subadult maxilla of a Tyrannosauridae from the Two Medicine Formation, Montana, United States

Delcourt, Rafael

doi:10.11606/0031-1049.2017.57.09

Cited by 4 publications

(2 citation statements)

References 15 publications

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“…Fully ‘mature’ ceratopsian individuals exhibit either wrinkled or smooth frill textures with a complete absence of the striated texture (Brown et al ., 2009), and a combination of mottled and striated surface textures, with a clear line of contact between texture types, has been used to diagnose ‘subadult’ individuals (Sampson et al ., 1997; Brown et al ., 2009). Surface sculpturing of cranial dermal bone has also been used to distinguish ontogenetic stages among tyrannosaurids (Carr, 1999; Carr & Williamson, 2004; Carr, Williamson & Schwimmer, 2005; Carr et al ., 2011, 2017; Delcourt, 2017 a ), and an unfinished texture on skull elements has been used to diagnose a maniraptoran theropod individual as ‘juvenile’ (Elzanowski & Wellnhofer, 1993).…”

Section: Methods Of Assessing Maturitymentioning

confidence: 99%

Assessing ontogenetic maturity in extinct saurian reptiles

et al. 2020

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Morphology forms the most fundamental level of data in vertebrate palaeontology because it is through interpretations of morphology that taxa are identified, creating the basis for broad evolutionary and palaeobiological hypotheses. Assessing maturity is one of the most basic aspects of morphological interpretation and provides the means to study the evolution of ontogenetic changes, population structure and palaeoecology, life‐history strategies, and heterochrony along evolutionary lineages that would otherwise be lost to time. Saurian reptiles (the least‐inclusive clade containing Lepidosauria and Archosauria) have remained an incredibly diverse, numerous, and disparate clade through their ~260‐million‐year history. Because of the great disparity in this group, assessing maturity of saurian reptiles is difficult, fraught with methodological and terminological ambiguity. We compiled a novel database of literature, assembling >900 individual instances of saurian maturity assessment, to examine critically how saurian maturity has been diagnosed. We review the often inexact and inconsistent terminology used in saurian maturity assessment (e.g. ‘juvenile’, ‘mature’) and provide routes for better clarity and cross‐study coherence. We describe the various methods that have been used to assess maturity in every major saurian group, integrating data from both extant and extinct taxa to give a full account of the current state of the field and providing method‐specific pitfalls, best practices, and fruitful directions for future research. We recommend that a new standard subsection, ‘Ontogenetic Assessment’, be added to the Systematic Palaeontology portions of descriptive studies to provide explicit ontogenetic diagnoses with clear criteria. Because the utility of different ontogenetic criteria is highly subclade dependent among saurians, even for widely used methods (e.g. neurocentral suture fusion), we recommend that phylogenetic context, preferably in the form of a phylogenetic bracket, be used to justify the use of a maturity assessment method. Different methods should be used in conjunction as independent lines of evidence when assessing maturity, instead of an ontogenetic diagnosis resting entirely on a single criterion, which is common in the literature. Critically, there is a need for data from extant taxa with well‐represented growth series to be integrated with the fossil record to ground maturity assessments of extinct taxa in well‐constrained, empirically tested methods.

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Section: Methods Of Assessing Maturitymentioning

confidence: 99%

Assessing ontogenetic maturity in extinct saurian reptiles

et al. 2020

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“…As the only known juvenile skeleton of Daspletosaurus , TMP 1994.143.1 has long been a key specimen to help characterize the morphology of juvenile tyrannosaurines 4,9,11,12 (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Reassessment of a juvenile Daspletosaurus from the Late Cretaceous of Alberta, Canada with implications for the identification of immature tyrannosaurids

Voris

Zelenitsky

Therrien

et al. 2019

Sci Rep

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Daspletosaurus is a large tyrannosaurine found in upper Campanian deposits of Alberta and Montana. Although several large subadult and adult individuals of this taxon are known, only one juvenile individual, TMP 1994.143.1, has been identified. This specimen has played a key role in the idea that juvenile tyrannosaurid individuals are difficult to differentiate among species. Here the taxonomic affinity of TMP 1994.143.1 is reassessed in light of a juvenile tyrannosaurine postorbital recently discovered in the Dinosaur Park Formation of Alberta. Anatomical comparisons and phylogenetic analyses reveal that TMP 1994.143.1 is referable to the albertosaurine Gorgosaurus libratus, whereas the new postorbital belongs to a small juvenile Daspletosaurus. This taxonomic reassignment of TMP 1994.143.1 results in the juvenile ontogenetic stage of Daspletosaurus being known only from two isolated cranial elements. The new postorbital provides insights into early Daspletosaurus ontogeny, revealing that the cornual process developed earlier or faster than in other tyrannosaurids. Although some ontogenetic changes in the postorbital are found to be unique to Daspletosaurus, overall changes are most consistent with those of other large tyrannosaurines. Our results also show that diagnostic features develop early in ontogeny, such that juveniles of different tyrannosaurid species are easier to differentiate than previously thought.

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

Yun¹

2021

Actapalrom

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A well preserved, but isolated metatarsal III of a tyrannosaurid dinosaur, originating probably from the Dinosaur Park Formation of Alberta, Canada, is tentatively referred to Daspletosaurus torosus. The size of the specimen suggests that it likely comes from a large juvenile, since the width of the distal end is about 63 % of that of a much larger individual. The morphology of the specimen supports the recently suggested hypotheses that apomorphies of tyrannosaurid taxa may have developed at young growth stages, and that juveniles of albertosaurines and tyrannosaurines may be easier to distinguish from one another than previously thought. Additionally, the specimen reported here is important in that it provides an addition to the very poor juvenile fossil record of Daspletosaurus.

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A subadult maxilla of a Tyrannosauridae from the Two Medicine Formation, Montana, United States

Abstract: Daspletosaurus is a Campanian genus of

Cited by 4 publications

References 15 publications

Assessing ontogenetic maturity in extinct saurian reptiles

Assessing ontogenetic maturity in extinct saurian reptiles

Reassessment of a juvenile Daspletosaurus from the Late Cretaceous of Alberta, Canada with implications for the identification of immature tyrannosaurids

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

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