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The articulation of sauropod necks: methodology and mythology.

ABSTRACT: Sauropods are often imagined to have held their heads high atop necks that ascended in a sweeping curve that was formed either intrinsically because of the shape of their vertebrae, or behaviorally by lifting the head, or both. Their necks are also popularly depicted in life with poses suggesting avian flexibility. The grounds for such interpretations are examined in terms of vertebral osteology, inferences about missing soft tissues, intervertebral flexibility, and behavior. Osteologically, the pronounced opisthocoely and conformal central and zygapophyseal articular surfaces strongly constrain the reconstruction of the cervical vertebral column. The sauropod cervico-dorsal vertebral column is essentially straight, in contrast to the curvature exhibited in those extant vertebrates that naturally hold their heads above rising necks. Regarding flexibility, extant vertebrates with homologous articular geometries preserve a degree of zygapophyseal overlap at the limits of deflection, a constraint that is further restricted by soft tissues. Sauropod necks, if similarly constrained, were capable of sweeping out large feeding surfaces, yet much less capable of retracting the head to explore the enclosed volume in an avian manner. Behaviorally, modern vertebrates generally assume characteristic neck postures which are close to the intrinsic curvature of the undeflected neck. With the exception of some vertebrates that can retract their heads to balance above their shoulders at rest (e.g., felids, lagomorphs, and some ratites), the undeflected neck generally predicts the default head height at rest and during locomotion.

SUBMITTER: Stevens KA

PROVIDER: S-EPMC3812995 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:This study compares short-term (30 days) and intermediate term (3 years) clinical outcomes in patients with large (?31 mm) versus small aortic neck diameters (?28 and ?31 mm). METHODS:Prospectively collected data from 741 patients who underwent endovascular aortic aneurysm repair were analyzed. Some surgeons have reported the threshold for a large aortic neck for endovascular aortic aneurysm repair to be 28 mm, whereas for others it is 31 mm. Therefore, we classified aortic neck diameter into less than or equal to 28 versus greater than 28 mm; and less than or equal to 31 versus greater than 31 mm. Logistic regression and Kaplan-Meier analyses were used to compare outcomes. RESULTS:There were 688 patients who had a defined aortic neck diameter: 592 with less than or equal to 28 mm, 96 with greater than 28 mm, 655 with less than or equal to 31 mm, and 33 with greater than 31 mm. The mean follow-up was 25.2 months for less than or equal to 31 mm versus 31.8 months for greater than 31 mm. Clinical characteristics were similar in all groups, except that there were more patients outside the instructions for use in the greater than 31 mm versus less than or equal to 31 mm group (94% vs 44%; P < .0001). There was a significant increase in early type I endoleak for patients with an aortic neck diameter of greater than 31 versus less than or equal to 31 mm (9 [27%] vs 74 [11%]; P = .01); late type I endoleaks (4 [14%] vs 18 [3%]; P = .01); sac expansion (5 [17%] vs 28 [5%]; P = .01); late intervention (5 [17%] vs 23 [4%]; P = .01); and death (9 [31%] vs 48 [8%]; P < .0001). There were no differences in outcomes between the patients with greater than 28 mm aortic neck diameters and the less than or equal to 28 mm diameters. Freedom from late type I endoleak at 1, 2, and 3 years were 96%, 88%, and 88% for patients with a neck diameter of greater than 31 mm versus 97%, 97%, and 97% for a diameter less than or equal to 31 mm (P = .19). The rate of freedom from sac expansion for patients with a diameter greater than 31 mm was 88%, 81%, and 81% at 1, 2, and 3 years versus 99%, 97%, and 92% for a diameter less than or equal to 31 mm (P = .02). Freedom from late intervention for 1, 2, and 3 years for patients with a diameter greater than 31 mm were 91%, 91%, and 91% versus 99%, 97%, and 96% for those with a diameter less than or equal to 31 mm. Survival rates at 1, 2, and 3 years for a diameter greater than 31 mm were 83%, 74%, and 68% versus 96%, 92%, and 90% for a diameter less than or equal to 31 mm (P < .001). Multivariate logistic regression analysis showed that patients with a diameter greater than 31 mm had an odds ratio of 6.1 (95% confidence interval [CI], 2.2-16.8) for mortality, 4.7 (95% CI, 1.4-15.5) for sac expansion, and 4.9 (95% CI, 1.4-17.4) for late type I endoleak. CONCLUSIONS:Patients with large aortic neck diameters (>31 mm) had higher rates of early and late type I endoleak, sac expansion, late intervention, and mortality.

Project description:Four isolated sauropod axial elements from the Oxford Clay Formation (Callovian, Middle Jurassic) of Peterborough, UK, are described. Two associated posterior dorsal vertebrae show a dorsoventrally elongated centrum and short neural arch, and nutrient or pneumatic foramina, most likely belonging to a non-neosauropod eusauropod, but showing ambiguous non-neosauropod eusauropod and neosauropod affinities. An isolated anterior caudal vertebra displays a ventral keel, a 'shoulder' indicating a wing-like transverse process, along with a possible prespinal lamina. This, together with an overall high complexity of the anterior caudal transverse process (ACTP) complex, indicates that this caudal could have belonged to a neosauropod. A second isolated middle-posterior caudal vertebra also shows some diagnostic features, despite the neural spine and neural arch not being preserved and the neurocentral sutures being unfused. The positioning of the neurocentral sutures on the anterior one third of the centrum indicates a middle caudal position, and the presence of faint ventrolateral crests, as well as a rhomboid anterior articulation surface, suggest neosauropod affinities. The presence of possible nutrient foramina are only tentative evidence of a neosauropod origin, as they are also found in Late Jurassic non-neosauropod eusauropods. As the caudals from the two other known sauropods from the Peterborough Oxford Clay, Cetiosauriscus stewarti and an indeterminate non-neosauropod eusauropod, do not show the features seen on either of the new elements described, both isolated caudals indicate a higher sauropod species diversity in the faunal assemblage than previously recognised. An exploratory phylogenetic analysis using characters from all four isolated elements supports a basal neosauropod placement for the anterior caudal, and a diplodocid origin for the middle caudal. The dorsal vertebrae are an unstable OTU, and therefore remain part of an indeterminate eusauropod of uncertain affinities. Together with Cetiosauriscus, and other material assigned to different sauropod groups, this study indicates the presence of a higher sauropod biodiversity in the Oxford Clay Formation than previously recognised. This study shows that it is still beneficial to examine isolated elements, as these may be indicators for higher species richness in deposits that are otherwise poor in terrestrial fauna.

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The articulation of sauropod necks: methodology and mythology.

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