Regionalization of the axial skeleton predates functional adaptation in the forerunners of mammals

Jones, Katrina E.; Gonzalez, Sarah Koopman; Angielczyk, Kenneth D.; Pierce, Stephanie E.

doi:10.1038/s41559-020-1094-9

Cited by 53 publications

(112 citation statements)

References 71 publications

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“…The convergent shape thus represents a case of parallel evolution from similar ancestors rather than classic convergence. A cervical-like angle of the zygapophyses has also been documented in carnivorans (Jones et al 2020) and perissodactyls (Jones 2016). This C7 morphology is accompanied by a more vertical posture of the neck in giraffe (Danowitz and Solounias 2015) and the gerenuk (Gunji and Endo 2019), but not within the Camelidae, and seems to have evolved convergently within the long-necked lineages.…”

Section: Evolutionary Trends Within Ruminantia and Camelidaementioning

confidence: 88%

Pushing the boundary? Testing the “functional elongation hypothesis” of the giraffe's neck

2021

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Although giraffes maintain the usual mammalian cervical number of seven vertebrae, their first thoracic vertebra (T1) exhibits aberrant anatomy and has been hypothesized to functionally elongate the neck. We test this "functional elongation hypothesis" by combining phylogenetically informed analyses of neck length, three-dimensional (3D) vertebral shape, and of the functional significance of shape differences across a broad sample of ruminants and camelids. Digital bone models of the cervicothoracic transition were subjected to 3D geometric morphometric analysis revealing how the shape of the seventh cervical (C7) has converged in several long-necked species. However, we find a unique "cervicalization" of the giraffe's T1. In contrast, we demonstrate a "thoracalization" of C7 for the European bison. Other giraffids (okapi and extinct Sivatherium) did not exhibit "cervicalized" T1 morphology. Quantitative range of motion (ROM) analysis at the cervicothoracic transition in ruminants and camelids confirms the "functional elongation hypothesis" for the giraffe in terms of increased mobility, especially with regard to dorsoventral flexion/extension. Additionally, other factors related to the unique morphology of the giraffe's cervicothoracic transition such as neck posture and intervertebral stability are discussed and should be considered in future studies of giraffe neck evolution.

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Section: Evolutionary Trends Within Ruminantia and Camelidaementioning

confidence: 88%

Pushing the boundary? Testing the “functional elongation hypothesis” of the giraffe's neck

2021

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“…In case of sprawling limb posture and trot‐like locomotion, maneuvering would be rather based on asymmetric LB. This may explain the fact that the sprawlers, for example, reptiles, have only zygapophysial joints of radial type with some variation, but entirely lack AR‐capable Tf joints (Jones et al ., 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Calculated aROM is shown by the white line (average) with the colored zone (range from maximum to minimum) around it [Colour figure can be viewed at wileyonlinelibrary.com] has long been predicted theoretically by the facets' orientation relative to the vertebra center (Rockwell et al, 1938;Gregersen and Lucas, 1967). Also, a number of experimental in vitro studies indicates a several-fold decrease in AR aROM when shifting from Tf to RfL joints (Townsend et al, 1983;Yamamoto et al, 1989;White and Panjabi, 1990;Panjabi et al, 1994;Wilke et al, 1997aWilke et al, , 1997c2011;Haussler et al, 2001;Busscher et al, 2010;Jones et al, 2020). In the final formulae developed for AR (Table 5) Figure 3a), that is, in the first case, the facets slide out from each other for almost a quarter of the arc length of the smaller one, and in the second case they do not slide at all beyond the margins of each other.…”

Section: Vertebral Column Differentiationmentioning

confidence: 99%

A mechanistic approach for the calculation of intervertebral mobility in mammals based on vertebrae osteometry

2020

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In this paper, we develop and validate an osteometry-based mechanistic approach to calculation of available range of motion (aROM) in presacral intervertebral joints in sagittal bending (SB), lateral bending (LB), and axial rotation (AR). Our basic assumption was the existence of a mechanistic interrelation between the geometry of zygapophysial articular facets and aROM. Trigonometric formulae are developed for aROM calculation, of which the general principle is that the angle of rotation is given by the ratio of the arc length of motion to the radius of this arc. We tested a number

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“…Exceptional are the prediaphragmatic thoracic vertebrae of mammals, which orientation is tangential (also called horizontal). In mammals, this tangential facet orientation is known to enhance the axial rotation in the intervertebral joints (Rockwell et al, 1938;Gregersen & Lucas, 1967;Jones et al, 2020), and it could probably have the same effect in pareiasaurians. This is just what is needed for decoupling of the ipsilateral fore and hind limbs in a passive-dynamic walk.…”

Section: Developing and Testing Predictionsmentioning

confidence: 99%

Passive-Dynamic Walkers of the Late Paleozoic

Kuznetsov

2020

Ameghiniana

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Two upper Permian trackways attributed to the ichnogenus Sukhonopus, which were originally interpreted as produced by pareiasaurians, have been studied. Based on the statistical analysis of dimensions of the longer trackway representing 15.5 locomotor cycles, the Sukhonopus gait was defined as a lateral-sequence walk shifted by ipsilateral limb synchronization towards the slow pace. This conclusion gained additional support through comparison of dimensions of the two trackways with the glenoacetabular-to-pes length ratio measured on the skeletons of the pareiasaur Deltavjatia. With the sprawling limb posture typical to lower tetrapods, including pareiasaurians, the pace can be only performed with body rocking from side to side, according to the principles of passive-dynamic walking. A natural-sized (185 cm long) model of the Sukhonopus producer was built. This model reproduces the passive-dynamic rocking pace, being driven manually by children pulling it forward by the rope and simultaneously pushing it from side to side. The passive-dynamic rocking pace of pareiasaurs, proved to be feasible by the model, requires functional differentiation of the hindlimbs and the forelimbs. The former were more appropriate for 22 propulsion, while the latter were more efficient in generation of the transverse forces required 23 to pump the rocking motion. It is hypothesized that this walking mechanism was associated 24 with archaic deficiency of nervous and muscular supply of the limbs. Possibly, it was also 25 2 employed by some other Paleozoic tetrapods. The ichnological evidence of this locomotion technique is the inward turn of the forelimb footprints, and the histological evidence is the extensive development in the long limb elements of spongy bone tissue in place of the superficial compact bone layer and marrow cavity.

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Regionalization of the axial skeleton predates functional adaptation in the forerunners of mammals

Cited by 53 publications

References 71 publications

Pushing the boundary? Testing the “functional elongation hypothesis” of the giraffe's neck

Pushing the boundary? Testing the “functional elongation hypothesis” of the giraffe's neck

A mechanistic approach for the calculation of intervertebral mobility in mammals based on vertebrae osteometry

Passive-Dynamic Walkers of the Late Paleozoic

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