Stegosauria

Galton, Peter M.; Upchurch, Paul

doi:10.1525/california/9780520242098.003.0019

Cited by 109 publications

(162 citation statements)

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“…The humeral head is restricted to the caudal shaft, suggesting that protraction of the humerus past the vertical would have been impossible, and that the forelimb was flexed to a similar degree. Hoof-like unguals are restricted to the medial two digits [17], suggesting that the elbows were abducted to a similar degree to those of ceratopsids ( figure 3a,c).…”

Section: Discussion (A) Hind Limb Functionmentioning

confidence: 97%

“…Ankylosaurs, stegosaurs and ceratopsids are widely accepted as being obligate quadrupeds [17][18][19] and to our knowledge quadrupedal stance in these taxa has never been questioned seriously in the literature. Although some earlier works considered hadrosaurs to be bipedal [20,21], recent studies have concluded that they were facultative [22] or obligate [23] quadrupeds.…”

Section: Methodsmentioning

confidence: 99%

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Does morphological convergence imply functional similarity? A test using the evolution of quadrupedalism in ornithischian dinosaurs

2012

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Convergent morphologies are thought to indicate functional similarity, arising because of a limited number of evolutionary or developmental pathways. Extant taxa displaying convergent morphologies are used as analogues to assess function in extinct taxa with similar characteristics. However, functional studies of extant taxa have shown that functional similarity can arise from differing morphologies, calling into question the paradigm that form and function are closely related. We test the hypothesis that convergent skeletal morphology indicates functional similarity in the fossil record using ornithischian dinosaurs. The rare transition from bipedality to quadrupedality occurred at least three times independently in this clade, resulting in a suite of convergent osteological characteristics. We use homology rather than analogy to provide an independent line of evidence about function, reconstructing soft tissues using the extant phylogenetic bracket and applying biomechanical concepts to produce qualitative assessments of muscle leverage. We also optimize character changes to investigate the sequence of character acquisition. Different lineages of quadrupedal ornithischian dinosaur stood and walked differently from each other, falsifying the hypothesis that osteological convergence indicates functional similarity. The acquisition of features correlated with quadrupedalism generally occurs in the same order in each clade, suggesting underlying developmental mechanisms that act as evolutionary constraints.

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Section: Discussion (A) Hind Limb Functionmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Does morphological convergence imply functional similarity? A test using the evolution of quadrupedalism in ornithischian dinosaurs

2012

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“…7). As noted above, this shape differs markedly from the tube-shaped, linear endocranial casts of basally diverging theropods (e.g., Brochu, 2000;Sampson and Witmer, 2004) and ornithischians (e.g., Stegosaurus; Marsh, 1877;Galton, 2001;Galton and Upchurch, 2004), indicating that the evolution of these flexures is independently derived along the prosauropod-sauropod branch of the saurischian tree. The endocranial casts of Plateosaurus, Shunosaurus, and Camarasaurus exhibit marked cerebral and pontine flexures relative to the above outgroups (Galton, 1985;Zheng, 2002, 2005;Ostrom and McIntosh, 1966).…”

Section: Cerebral and Pontine Flexuresmentioning

confidence: 89%

The Braincase of Apatosaurus (Dinosauria: Sauropoda) Based on Computed Tomography of a New Specimen with Comments on Variation and Evolution in Sauropod Neuroanatomy

Balanoff¹,

Bever²,

Ikejiri³

2010

American Museum Novitates

105

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We describe a previously unreported braincase of the sauropod dinosaur Apatosaurus from the Cactus Park Quarry, Morrison Formation of western Colorado using high-resolution X-ray computed tomography. The digital nature of these data allowed us to prepare and describe the first three-dimensional rendering of the endocranial space in this historically important dinosaur species. Results are compared with a range of taxa drawn from across the sauropod tree revealing previously underappreciated variation in the sauropod neurocranium. Examples of variable characters include the degree of cerebral and pontine flexure, the morphology of the parietal body and superior sagittal sinus and their relationship with the overlying dermal roof, and the conformation of several cranial nerve foramina. We provide preliminary evolutionary hypotheses and discussion for many of these features. The recognition that considerable variation is present in the sauropod neurocranium hopefully will encourage more detailed descriptions of this anatomically complex region, as well as facilitating a synthetic review of the sauropodomorph braincase as these descriptions become available.

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“…Stegosauria is a clade of ornithischian dinosaurs characterized by an array of elaborate postcranial osteoderms (Galton & Upchurch 2004;Maidment et al 2008). Stegosauria achieved a wide distribution during the Late Jurassic and members of the clade are abundant in faunas of this age (Europe, North America, Africa and Asia; see Galton & Upchurch 2004;Maidment et al 2008 and references therein).…”

Section: Introductionmentioning

confidence: 99%

A new long-necked ‘sauropod-mimic’ stegosaur and the evolution of the plated dinosaurs

2009

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Stegosaurian dinosaurs have a quadrupedal stance, short forelimbs, short necks, and are generally considered to be low browsers. A new stegosaur, Miragaia longicollum gen. et sp. nov., from the Late Jurassic of Portugal, has a neck comprising at least 17 cervical vertebrae. This is eight additional cervical vertebrae when compared with the ancestral condition seen in basal ornithischians such as Scutellosaurus. Miragaia has a higher cervical count than most of the iconically long-necked sauropod dinosaurs. Long neck length has been achieved by 'cervicalization' of anterior dorsal vertebrae and probable lengthening of centra. All these anatomical features are evolutionarily convergent with those exhibited in the necks of sauropod dinosaurs. Miragaia longicollum is based upon a partial articulated skeleton, and includes the only known cranial remains from any European stegosaur. A well-resolved phylogeny supports a new clade that unites Miragaia and Dacentrurus as the sister group to Stegosaurus; this new topology challenges the common view of Dacentrurus as a basal stegosaur.

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Stegosauria

Cited by 109 publications

References 0 publications

Does morphological convergence imply functional similarity? A test using the evolution of quadrupedalism in ornithischian dinosaurs

Does morphological convergence imply functional similarity? A test using the evolution of quadrupedalism in ornithischian dinosaurs

The Braincase of Apatosaurus (Dinosauria: Sauropoda) Based on Computed Tomography of a New Specimen with Comments on Variation and Evolution in Sauropod Neuroanatomy

A new long-necked ‘sauropod-mimic’ stegosaur and the evolution of the plated dinosaurs

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