Publications
73 results found
Maidment SCR, Woodruff DC, Horner JR, 2018, A NEW SPECIMEN OF THE ORNITHISCHIAN DINOSAUR <i>HESPEROSAURUS MJOSI</i> FROM THE UPPER JURASSIC MORRISON FORMATION OF MONTANA, USA, AND IMPLICATIONS FOR GROWTH AND SIZE IN MORRISON STEGOSAURS, JOURNAL OF VERTEBRATE PALEONTOLOGY, Vol: 38, ISSN: 0272-4634
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- Citations: 10
Barrett PM, Maidment SCR, 2017, The evolution of ornithischian quadrupedality, JOURNAL OF IBERIAN GEOLOGY, Vol: 43, Pages: 363-377, ISSN: 1698-6180
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- Citations: 22
Maidment SCR, Kirkpatrick C, Craik-Smith B, et al., 2017, A new ornithischian dinosaur and the terrestrial vertebrate fauna from a bone bed in the Wealden of Ardingly, West Sussex (vol 128, pg 332, 2017), PROCEEDINGS OF THE GEOLOGISTS ASSOCIATION, Vol: 128, Pages: 681-681, ISSN: 0016-7878
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- Citations: 1
Maidment SCR, Kirkpatrick C, Craik-Smith B, et al., 2017, A new ornithischian dinosaur and the terrestrial vertebrate fauna from a bone bed in the Wealden of Ardingly, West Sussex, PROCEEDINGS OF THE GEOLOGISTS ASSOCIATION, Vol: 128, Pages: 332-339, ISSN: 0016-7878
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- Citations: 4
Raven TJ, Maidment SCR, 2017, A new phylogeny of Stegosauria (Dinosauria, Ornithischia), Palaeontology, Vol: 60, Pages: 401-408, ISSN: 1475-4983
The stegosaurs are some of the most easily recognisable dinosaurs, but they are surprisingly rare as fossils. Consequently much remains unknown about their palaeobiology, and every new stegosaurian find contributes to understanding the evolution of the clade. Since the last attempt to examine the evolutionary relationships of Stegosauria, new specimens have come to light, including the most complete individual of Stegosaurus ever found, new taxa have been described and, perhaps most importantly, new methods for analysis of cladistic datasets have been produced. In the light of these new data and technological advances, the phylogenetic relationships of the stegosaurs and basal armoured dinosaurs are investigated. The inclusionof continuous data results in much better resolution than was previously obtained, and the resulting single most parsimonious tree supports re-erection of the genera Miragaia and Hesperosaurus, which had previously been synonymized with Dacentrurus and Stegosaurus respectively. The recently described genus Alcovasaurus is resolved as a basal thyreophoran, but this is likely to be due to a combination of a very high degree of missing data and the questionable ontogenetic stage of the specimen. Examination of the effects of continuous data on the analysis suggest that while it contains a phylogenetic signal congruent with that of discrete data and provides better resolution than discrete data alone, it can affect topologies in unpredictable ways, particularly in areas of the tree where there are large amounts of missing data. The phylogeny presented here will form the basis for future work on the palaeobiology of the plated dinosaurs.
Brassey CA, Maidment SCR, Barrett PM, 2017, MUSCLE MOMENT ARM ANALYSES APPLIED TO VERTEBRATE PALEONTOLOGY: A CASE STUDY USING <i>STEGOSAURUS</i> <i>STENOPS</i> MARSH, 1887, JOURNAL OF VERTEBRATE PALEONTOLOGY, Vol: 37, ISSN: 0272-4634
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- Citations: 19
Maidment SCR, Brassey C, Barrett PM, 2015, The postcranial skeleton of an exceptionally complete individual of the plated dinosaur Stegosaurus stenops (Dinosauria: Thyreophora) from the Upper Jurassic Morrison Formation of Wyoming, U.S.A., PLOS One, Vol: 10, ISSN: 1932-6203
Although Stegosaurus is one of the most iconic dinosaurs, well-preservedfossils are rare and as a consequence there is still much that remains unknownabout the taxon. A new, exceptionally complete individual affords theopportunity to describe the anatomy of Stegosaurus in detail for the first time inover a century, and enables additional comparisons with other stegosauriandinosaurs. The new specimen is from the Red Canyon Ranch Quarry, near ShellWyoming, and appears to have been so well preserved because it was buriedrapidly in a pond or body of standing water immediately after death. The quarryis probably located in the middle part of the Morrison Formation, which isbelieved to be Tithonian in age in this area. The specimen is referable toStegosaurus stenops based on the possession of an edentulous anterior portion ofthe dentary and elevated postzygapophyses on the cervical vertebrae. Newinformation provided by the specimen concerns the morphology of thevertebrae, the iliosacral block and dermal armor. Several aspects of itsmorphology indicate the individual was not fully skeletally mature at the time ofdeath, corroborating a previous histological study.
Bates K, Maidment SC, Schachner ER, et al., 2015, Comments and corrections on 3D modeling studies of locomotor muscle moment arms in archosaurs., PeerJ, Vol: 3, ISSN: 2167-8359
In a number of recent studies we used computer modeling to investigate the evolution of muscle leverage (moment arms) and function in extant and extinct archosaur lineages (crocodilians, dinosaurs including birds and pterosaurs). These studies sought to quantify the level of disparity and convergence in muscle moment arms during the evolution of bipedal and quadrupedal posture in various independent archosaur lineages, and in doing so further our understanding of changes in anatomy, locomotion and ecology during the group's >250 million year evolutionary history. Subsequent work by others has led us to re-evaluate our models, which revealed a methodological error that impacted on the results obtained from the abduction-adduction and long-axis rotation moment arms in our published studies. In this paper we present corrected abduction-adduction and long axis rotation moment arms for all our models, and evaluate the impact of this new data on the conclusions of our previous studies. We find that, in general, our newly corrected data differed only slightly from that previously published, with very few qualitative changes in muscle moments (e.g., muscles originally identified as abductors remained abductors). As a result the majority of our previous conclusions regarding the functional evolution of key muscles in these archosaur groups are upheld.
Bertazzo S, Maidment S, Kallepitis C, et al., 2015, Fibres and cellular structures preserved in 75-million–year-old dinosaur specimens, Nature Communications, Vol: 6, ISSN: 2041-1723
Exceptionally preserved organic remains are known throughout the vertebrate fossil record, and recently, evidence has emerged that such soft tissue might contain original components. We examined samples from eight Cretaceous dinosaur bones using nano-analytical techniques; the bones are not exceptionally preserved and show no external indication of soft tissue. In one sample, we observe structures consistent with endogenous collagen fibre remains displaying ~67 nm banding, indicating the possible preservation of the original quaternary structure. Using ToF-SIMS, we identify amino-acid fragments typical of collagen fibrils. Furthermore, we observe structures consistent with putative erythrocyte remains that exhibit mass spectra similar to emu whole blood. Using advanced material characterization approaches, we find that these putative biological structures can be well preserved over geological timescales, and their preservation is more common than previously thought. The preservation of protein over geological timescales offers the opportunity to investigate relationships, physiology and behaviour of long extinct animals.
Bates KT, Falkingham PL, Macaulay S, et al., 2015, Downsizing a giant: re-evaluating Dreadnoughtus body mass, Biology Letters, Vol: 11, ISSN: 1744-957X
Estimates of body mass often represent the founding assumption on which biomechanicaland macroevolutionary hypotheses are based. Recently, a scalingequation was applied to a newly discovered titanosaurian sauropod dinosaur(Dreadnoughtus), yielding a 59 300 kg body mass estimate for this animal.Herein, we use a modelling approach to examine the plausibility of this massestimate for Dreadnoughtus. We find that 59 300 kg for Dreadnoughtus ishighly implausible and demonstrate that masses above 40 000 kg requirehigh body densities and expansions of soft tissue volume outside the skeletonseveral times greater than found in living quadrupedal mammals. Similarresults from a small sample of other archosaurs suggests that lower-end massestimates derived from scaling equations are most plausible for Dreadnoughtus,based on existing volumetric and density data from extant animals. Althoughvolumetric models appear to more tightly constrain dinosaur body mass, thereremains a clear need to further support these models with more exhaustive datafrom living animals. The relative and absolute discrepancies in mass predictionsbetween volumetric models and scaling equations also indicate aneed to systematically compare predictions across a wide size and taxonomicrange to better inform studies of dinosaur body size.
Brassey CA, Maidment SCR, Barrett PM, 2015, Body mass estimates of an exceptionally complete Stegosaurus (Ornithischia: Thyreophora): comparing volumetric and linear bivariate mass estimation methods, Biology Letters, Vol: 11, ISSN: 1744-957X
Body mass is a key biological variable, but difficult to assess from fossils.Various techniques exist for estimating body mass from skeletal parameters,but few studies have compared outputs from different methods. Here, weapply several mass estimation methods to an exceptionally complete skeletonof the dinosaur Stegosaurus. Applying a volumetric convex-hullingtechnique to a digital model of Stegosaurus, we estimate a mass of 1560 kg(95% prediction interval 1082–2256 kg) for this individual. By contrast,bivariate equations based on limb dimensions predict values between 2355and 3751 kg and require implausible amounts of soft tissue and/or highbody densities. When corrected for ontogenetic scaling, however, volumetricand linear equations are brought into close agreement. Our results raise concernsregarding the application of predictive equations to extinct taxa withno living analogues in terms of overall morphology and highlight the sensitivityof bivariate predictive equations to the ontogenetic status of thespecimen. We emphasize the significance of rare, complete fossil skeletonsin validating widely applied mass estimation equations based on incompleteskeletal material and stress the importance of accurately determiningspecimen age prior to further analyses.
Balikova D, Maidment S, Muxworthy AR, 2015, The age of the Morrison Formation (Western Interior, USA): A Magnetostratigraphic Approach (poster), Magnetic Interactions 2015
Maidment SCR, Henderson DM, Barrett PM, 2014, What drove reversions to quadrupedality in ornithischian dinosaurs? Testing hypotheses using centre of mass modelling, Naturwissenschaften, Vol: 101, Pages: 989-1001, ISSN: 0028-1042
The exceptionally rare transition to quadrupedalismfrom bipedal ancestors occurred on three independent occasionsin ornithischian dinosaurs. The possible driving forcesbehind these transitions remain elusive, but several hypotheses—includingthe development of dermal armour and theexpansion of head size and cranial ornamentation—have beenproposed to account for this major shift in stance. Wemodelled the position of the centre of mass (CoM) in severalexemplar ornithischian taxa and demonstrate that the anteriorshifts in CoM position associated with the development of anenlarged skull ornamented with horns and frills for display/defence may have been one of the drivers promoting ceratopsianquadrupedality. A posterior shift in CoM position coincidentwith the development of extensive dermal armour inthyreophorans demonstrates this cannot have been a primarycausative mechanism for quadrupedality in this clade.Quadrupedalism developed in response to different selectivepressures in each ornithischian lineage, indicating differentevolutionary pathways to convergent quadrupedalmorphology.
McDonald AT, Maidment SCR, Barrett PM, et al., 2014, Osteology of the basal hadrosauroid Equijubus normani (Dinosauria, Ornithopoda) from the Early Cretaceous of China, Hadrosaurs, Editors: Eberth, Evans, Bloomington, Publisher: Indiana University Press, Pages: 44-72, ISBN: 9780253013903
Maidment SCR, Bates KT, Barrett PM, 2014, Three-dimensional computational modeling of pelvic locomotor muscle moment arms in Edmontosaurus (Dinosauria, Hadrosauridae) and comparisons with other archosaurs., Hadrosaurs, Editors: Eberth, Evans, Bloomington, Publisher: Indiana University Press, Pages: 433-448, ISBN: 9780253013903
Maidment SCR, Bates KT, Falkingham PL, et al., 2014, Locomotion in ornithischian dinosaurs: an assessment using three-dimensional computational modelling, BIOLOGICAL REVIEWS, Vol: 89, Pages: 588-617, ISSN: 1464-7931
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- Citations: 40
Maidment SCR, Barrett PM, 2014, Osteological correlates for quadrupedality in ornithischian dinosaurs, ACTA PALAEONTOLOGICA POLONICA, Vol: 59, Pages: 53-70, ISSN: 0567-7920
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- Citations: 60
Maidment SCR, Barrett PM, 2012, Does morphological convergence imply functional similarity? A test using the evolution of quadrupedalism in ornithischian dinosaurs, PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 279, Pages: 3765-3771, ISSN: 0962-8452
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- Citations: 43
Maidment SC, Linton DH, Upchurch P, et al., 2012, Limb-bone scaling indicates diverse stance and gait in quadrupedal ornithischian dinosaurs., PLOS One, Vol: 7, ISSN: 1932-6203
BACKGROUND: The most primitive ornithischian dinosaurs were small bipeds, but quadrupedality evolved three times independently in the clade. The transition to quadrupedality from bipedal ancestors is rare in the history of terrestrial vertebrate evolution, and extant analogues do not exist. Constraints imposed on quadrupedal ornithischians by their ancestral bipedal bauplan remain unexplored, and consequently, debate continues about their stance and gait. For example, it has been proposed that some ornithischians could run, while others consider that none were cursorial. METHODOLOGY/PRINCIPAL FINDINGS: Drawing on biomechanical concepts of limb bone scaling and locomotor theory developed for extant taxa, we use the largest dataset of ornithischian postcranial measurements so far compiled to examine stance and gait in quadrupedal ornithischians. Differences in femoral midshaft eccentricity in hadrosaurs and ceratopsids may indicate that hadrosaurs placed their feet on the midline during locomotion, while ceratopsids placed their feet more laterally, under the hips. More robust humeri in the largest ceratopsids relative to smaller taxa may be due to positive allometry in skull size with body mass in ceratopsids, while slender humeri in the largest stegosaurs may be the result of differences in dermal armor distribution within the clade. Hadrosaurs are found to display the most cursorial morphologies of the quadrupedal ornithischian cades, indicating higher locomotor performance than in ceratopsids and thyreophorans. CONCLUSIONS/SIGNIFICANCE: Limb bone scaling indicates that a previously unrealised diversity of stances and gaits were employed by quadrupedal ornithischians despite apparent convergence in limb morphology. Grouping quadrupedal ornithischians together as a single functional group hides this disparity. Differences in limb proportions and scaling are likely due to the possession of display structures such as horns, frills and dermal armor that may have affect
Bates KT, Maidment SCR, Allen V, et al., 2012, Computational modelling of locomotor muscle moment arms in the basal dinosaur Lesothosaurus diagnosticus: assessing convergence between birds and basal ornithischians, JOURNAL OF ANATOMY, Vol: 220, Pages: 212-232, ISSN: 0021-8782
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- Citations: 38
Thompson RS, Parrish JC, Maidment SCR, et al., 2012, Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora), Journal of Systematic Palaeontology, Vol: 10, Pages: 301-312
Barden HE, Maidment SCR, 2011, Evidence for sexual dimorphism in the stegosaurian dinosaur<i>Kentrosaurus aethiopicus</i>from the Upper Jurassic of Tanzania, Journal of Vertebrate Paleontology, Vol: 31, Pages: 641-651, ISSN: 0272-4634
Maidment SCR, 2011, Comment on Stegosaurus Marsh, 1877 (Dinosauria, Ornithischia): proposed replacement of the type species with Stegosaurus stenops Marsh, 1887 (Case 3536; see BZN 68: 127-133), Bulletin of Zoological Nomenclature, Vol: 68, Pages: 213-214
Maidment S, Bates K, Allen V, et al., 2011, 3D COMPUTATIONAL MODELLING OF LOCOMOTOR MUSCLE MOMENT ARMS IN <i>LESOTHOSAURUS DIAGNOSTICUS</i>: IMPLICATIONS FOR BASAL DINOSAUR LOCOMOTION, Publisher: SOC VERTEBRATE PALEONTOLOGY, Pages: 149-150, ISSN: 0272-4634
Barrett PM, Maidment SCR, 2011, Wealden armoured dinosaurs, English Wealden Fossils, Editors: Batten, London, Publisher: The Palaeontological Association, Pages: 391-406
Maidment SCR, Barrett PM, 2011, The locomotor musculature of basal ornithischian dinosaurs, Journal of Vertebrate Paleontology, Vol: 31, Pages: 1265-1291
Barrett PM, Maidment SCR, 2011, Dinosaurs of Dorset: part III, the ornithischian dinosaurs (Dinosauria: Ornithischia) with additional comments on the sauropods, Proceedings of the Dorset Natural History and Archaeological Society, Vol: 132, Pages: 145-163
Maidment SCR, Barrett PM, 2011, A new specimen of Chasmosaurus belli (Ornithischia: Ceratopsidae), a revision of the genus, and the utility of postcrania in the taxonomy and systematics of ceratopsid dinosaurs, Zootaxa, Vol: 2963, Pages: 1-47
Barden HE, Maidment SCR, 2011, Evidence for sexual dimorphism in the stegosaurian dinosaur Kentrosaurus aethiopicus from the Upper Jurassic of Tanzania., Journal of Vertebrate Paleontology, Vol: 31, Pages: 641-651
Maidment SCR, Porro LB, 2010, Homology of the palpebral and origin of the supraorbital ossifications in ornithischian dinosaurs, Lethaia, Vol: 43, Pages: 95-111
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