The ancestral morphology of lumbar vertebrae and its diversification in early Cenozoic mammals

Kort, Anne E.

doi:10.1007/s10914-023-09676-2

Cited by 2 publications

(2 citation statements)

References 66 publications

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“…Revolute zygapophyses appear to a unique, derived feature, which stabilized the spine against disarticulation while still allowing flexion. Among Paleogene mammals, revolute zygapophyses appear widespread in taxa thought to fall under Ferungulata, the superorder that includes living ungulates and carnivorans, while many other groups, including those more basal to Placentalia, have relatively flat zygapophyses (Argot, 2013;Kort, 2023;Kort et al, 2022;Rose et al, 2019;Wood et al, 2010;Zhou et al, 1992). Paleogene mammals that have revolute zygapophyses include some of the largest mammals for the time period, like mesonychids, but many large mammals, like uintatheriids, lacked this feature.…”

Section: Evolution Of Lumbar Vertebrae Functionmentioning

confidence: 99%

“…Many morphological changes can affect the relative mobility of lumbar vertebrae, like shortening of the centra or widening of the transverse processes (Boszczyk et al, 2001). Though many of these changes have evolved multiple times across Mammalia, revolute zygapophyses, articulations with an interlocking S-shape appear to have only evolved once (Kort, 2023). In most mammals, lumbar zygapophyses are relatively planar, with a slight overall curve to the surface.…”

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Function of revolute zygapophyses in the lumbar vertebrae of early placental mammals

Kort,

Jones

2023

The Anatomical Record

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The unique morphology of mammalian lumbar vertebrae allows the spine to flex and extend in the sagittal plane during locomotion. This movement increases stride length and allows mammals to efficiently breathe while running with an asymmetric gait. In extant mammals, the amount of flexion that occurs varies across different locomotor styles, with dorsostable runners relying more on movement of long limbs to run and dorsomobile runners incorporating more flexion of the back. Although long limbs and a stabilized lumbar region are commonly associated with each other in extant mammals, many “archaic” placental mammals with short limbs had lumbar vertebrae with revolute zygapophyses. These articulations with an interlocking S‐shape are found only in artiodactyls among extant mammals and have been hypothesized to stabilize against flexion of the back. This would suggest that archaic placental mammals may not have incorporated dorsoventral flexion into locomotion to the same extent as extant mammals with similar proportions. We tested the relative mobility of fossil lumbar vertebrae from two early placental mammals, the creodonts Patriofelis and Limnocyon, to see how these vertebrae may have functioned. We compared range of motion (ROM) between the original vertebrae, with revolute morphology and digitally altered vertebrae with a flat morphology. We found that the revolute morphology had relatively little effect on dorsoventral flexion and instead that it likely prevented disarticulation due to shear forces on the spine. These results show that flexion of the spine has been an important part of mammalian locomotion for at least 50 million years.

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Section: Evolution Of Lumbar Vertebrae Functionmentioning

confidence: 99%

mentioning

confidence: 99%

Function of revolute zygapophyses in the lumbar vertebrae of early placental mammals

Kort,

Jones

2023

The Anatomical Record

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Remarks on the functional morphology of the earliest mammals

Preuschoft,

Martin,

Werneburg

2024

Mamm Biol

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The earliest mammals are characterized by a series of derived characters when compared to their synapsid predecessors. In comparison to non-mammalian synapsids, these features include highly efficient teeth, a small body size, a parasagittal limb posture, as well as a reduced number of ribs and girdle elements and light-weighted tails. We argue that the mammalian body construction and its functionality are constituted by a set of partially interrelated morphological traits, including akinetic skulls, tooth anatomy, and food processing; body size, locomotor speed, and tail reduction; the posture of the body and the construction of the girdle elements; as well as body torsion and rib reduction. By discussing these features from a biomechanical view, we demonstrate that high speed was the most important evolutionary advantage of the small earliest mammals over their larger synapsid ancestors, as well as over dinosaurs at the end of the Mesozoic.

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The ancestral morphology of lumbar vertebrae and its diversification in early Cenozoic mammals

Cited by 2 publications

References 66 publications

Function of revolute zygapophyses in the lumbar vertebrae of early placental mammals

Function of revolute zygapophyses in the lumbar vertebrae of early placental mammals

Remarks on the functional morphology of the earliest mammals

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