The Elasmosaurid Shoulder‐girdle and Fore‐limb.

Watson, D. M. S.

doi:10.1111/j.1096-3642.1924.tb03320.x

Cited by 51 publications

(92 citation statements)

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“…The relationships of the closely related millerettids have also been recently reevaluated (Cisneros in press). Another enigmatic group, the bolosaurids had long been known from Texas (Cope 1878), Russia (Ivakhnenko et al 1997) and China (Li & Cheng 1995), but due to the prevalence of the temporal fenestration classification scheme, they were variously considered to be synapsids (Watson 1917) or closely related to eureptilian taxa (von Huene 1956;Romer 1956). Berman et al (2000) described a new taxon of bolosaurid from the Lower Permian of Germany, Eudibamus cursoris Berman et al, 2000.…”

Section: The Impact Of Phylogenetic Systematics and The Turtle Debatementioning

confidence: 99%

Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade

Tsuji

Müller²

2009

Fossil Record

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Section: The Impact Of Phylogenetic Systematics and The Turtle Debatementioning

confidence: 99%

Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade

Tsuji

Müller²

2009

Fossil Record

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“…By reconstructing musculature and based on morphological observations of the pectoral girdle, Carroll and Gaskill [22], Watson [25], and v. Huene [26] hypothesized that Nothosauroidea independently evolved paraxial locomotion, where the front limbs were employed in a “rowing flight”, combining lift- and drag-based elements of propulsion, like recent sea lions [27], while the hind limbs were used for maneuvering.…”

Section: Introductionmentioning

confidence: 99%

Evolutionary implications of the divergent long bone histologies of Nothosaurus and Pistosaurus (Sauropterygia, Triassic)

2013

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BackgroundEosauropterygians consist of two major clades, the Nothosauroidea of the Tethysian Middle Triassic (e.g., Nothosaurus) and the Pistosauroidea. The Pistosauroidea include rare Triassic forms (Pistosauridae) and the Plesiosauria of the Jurassic and Cretaceous. Long bones of Nothosaurus and Pistosaurus from the Muschelkalk (Middle Triassic) of Germany and France and a femur of the Lower Jurassic Plesiosaurus dolichodeirus were studied histologically and microanatomically to understand the evolution of locomotory adaptations, patterns of growth and life history in these two lineages.ResultsWe found that the cortex of adult Nothosaurus long bones consists of lamellar zonal bone. Large Upper Muschelkalk humeri of large-bodied Nothosaurus mirabilis and N. giganteus differ from the small Lower Muschelkalk (Nothosaurus marchicus/N. winterswijkensis) humeri by a striking microanatomical specialization for aquatic tetrapods: the medullary cavity is much enlarged and the cortex is reduced to a few millimeters in thickness. Unexpectedly, the humeri of Pistosaurus consist of continuously deposited, radially vascularized fibrolamellar bone tissue like in the Plesiosaurus sample. Plesiosaurus shows intense Haversian remodeling, which has never been described in Triassic sauropterygians.ConclusionsThe generally lamellar zonal bone tissue of nothosaur long bones indicates a low growth rate and suggests a low basal metabolic rate. The large triangular cross section of large-bodied Nothosaurus from the Upper Muschelkalk with their large medullary region evolved to withstand high bending loads. Nothosaurus humerus morphology and microanatomy indicates the evolution of paraxial front limb propulsion in the Middle Triassic, well before its convergent evolution in the Plesiosauria in the latest Triassic. Fibrolamellar bone tissue, as found in Pistosaurus and Plesiosaurus, suggests a high growth rate and basal metabolic rate. The presence of fibrolamellar bone tissue in Pistosaurus suggests that these features had already evolved in the Pistosauroidea by the Middle Triassic, well before the plesiosaurs radiated. Together with a relatively large body size, a high basal metabolic rate probably was the key to the invasion of the Pistosauroidea of the pelagic habitat in the Middle Triassic and the success of the Plesiosauria in the Jurassic and Cretaceous.

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“…Figure 17 depicts all previously published plesiosaurian pectoral girdle reconstructions (Watson, 1924;Tarlo, 1958;Robinson, 1975;LinghamSoliar, 2000;Carpenter et al, 2010). None of the previous reconstructions included ligaments, the coracoid origin of part of the triceps, the trapezius or the costocoracoideus.…”

Section: Comparison With Previous Reconstructionsmentioning

confidence: 99%

“…Eosauropterygians present secondary adaptations to a marine lifestyle unparalleled in other marine groups. For instance, the subaqueous locomotory mode of plesiosaurians possessing four long, sub-equal paddles remains a functional riddle (e.g., Connybeare, 1824;Watson, 1924;Robinson, 1975Robinson, , 1977Carpenter et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Soft-tissue anatomy of the Plesiosaur pectoral girdle inferred from basal Eosauropterygia taxa and the extant phylogenetic bracket

Araújo

Correia

2015

Palaeontologia Electronica

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Plesiosaurians are highly derived secondarily-adapted organisms (if fishes are primarily-adapted) with a long evolutionary history, and they are closely related with basal eosauropterygians. Attempts to reconstruct soft-tissue anatomy can be complicated due to the lack of extant closely-related species, thus various lines of evidence must be considered. This study aims to reconstruct the pectoral girdle myology of eosauropterygians. Information derived from the extant phylogenetic bracket method was not sufficient to clarify muscle attachments in the pectoral girdle of plesiosaurians. To correctly infer muscle homologies, the extant phylogenetic bracket information had to be complemented with developmental and osteological information, and osteological transformations had to be traced back to Permian basal neodiapsids. The reconstructed pectoral girdle musculature presented here is, thus, significantly different from previous attempts. As in secondarily-adapted aquatic modern analogues, several muscles atrophied (e.g., pectoralis, episternocleidomastoideus) and others specialized (e.g., coracobrachialis, clavodeltoideus) in order to attain a more influential role to the stringent conditions of subaquatic locomotion. The subcoracoscapularis, scapulodeltoideus, scapulohumeralis and supracoracoideus are inferred to be glenohumeral stabilizers. The clavodeltoideus acted as the main protractor muscle and the coracobrachialis as a major retractor muscle, possibly in conjunction with the latissimus dorsi. Several heads of the triceps possibly atrophied, as in whales, serving mainly as a cubital joint stabilizer. The trapezius, serratus and levator scapulae served as pectoral girdle stabilizers.

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The Elasmosaurid Shoulder‐girdle and Fore‐limb.

Cited by 51 publications

References 0 publications

Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade

Assembling the history of the Parareptilia: phylogeny, diversification, and a new definition of the clade

Evolutionary implications of the divergent long bone histologies of Nothosaurus and Pistosaurus (Sauropterygia, Triassic)

Soft-tissue anatomy of the Plesiosaur pectoral girdle inferred from basal Eosauropterygia taxa and the extant phylogenetic bracket

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