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Three and Four-Dimensional Visualization and Analysis Approaches to Study Vertebrate Axial Elongation and Segmentation
Published on: February 28, 2021
Variability and constraint in the mammalian vertebral column
R J Asher1, K H Lin, N Kardjilov
1Department of Zoology, University of Cambridge, Downing Street, Cambridge, UK. r.asher@zoo.cam.ac.uk
Journal of Evolutionary Biology
|February 23, 2011
Summary
Mammalian vertebral counts vary, with monotremes, xenarthrans, afrotherians, and primates showing high thoracolumbar variation. Rodents exhibit the least variation, suggesting developmental constraints influence vertebral patterns.
Area of Science:
- Evolutionary biology
- Developmental biology
- Comparative anatomy
Background:
- Vertebral variation patterns in mammals are poorly quantified, hindering studies on axial skeleton covariation and conservatism.
- Understanding vertebral development mechanisms is crucial for evolutionary insights.
Purpose of the Study:
- To quantify vertebral count variation across diverse mammal species.
- To test hypotheses regarding covariation within the axial skeleton.
- To investigate mechanisms driving vertebral conservatism and anomalies.
Main Methods:
- Examined vertebral counts in 42 mammal species, including monotremes, marsupials, and placental clades.
- Analyzed meristic deviations from species' median series counts.
- Investigated correlations between sacral position, rib cage length, and sternebrae number.
Main Results:
- Xenarthrans and afrotherians show high proportions of individuals with meristic deviations.
- Monotremes, xenarthrans, afrotherians, and primates exhibit significant thoracolumbar vertebral count variation.
- Rodents display the least variation; most mammals correlate sacral position with rib cage length, not sternebrae number.
- No increased frequency of vertebral anomalies was found in embryos or neonates compared to adults.
Conclusions:
- Vertebral skeletal structures are modular and covary, particularly the sacral position and rib cage length.
- Variable correlations suggest non-uniform boundaries of axial skeleton precursors across species.
- Stabilizing selection may not be the primary driver of vertebral patterning frequency in mammals.
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