DOI: 10.5061/dryad.6m905qg0x
title: XYZ coordinates of middle lumbar vertebrae - 3D GM analysis for: A nearly complete lower back of Australopithecus sediba

description: Adaptations of the lower back to bipedalism are frequently discussed but
 infrequently demonstrated in early fossil hominins. Newly discovered
 lumbar vertebrae contribute to a near-complete lower back of Malapa
 Hominin 2 (MH2), offering additional insights into posture and locomotion
 in Australopithecus sediba. We show that MH2 demonstrates a lower back
 consistent with lumbar lordosis and other adaptations to bipedalism,
 including an increase in the width of intervertebral articular facets from
 the upper to lower lumbar column (“pyramidal configuration”). These
 results contrast with some recent work on lordosis in fossil hominins,
 where MH2 was argued to demonstrate no appreciable lordosis
 (“hypolordosis”) similar to Neandertals. Our three-dimensional geometric
 morphometric (3D GM) analyses show that MH2’s nearly complete middle
 lumbar vertebra is human-like in overall shape but its vertebral body is
 somewhat intermediate in shape between modern humans and great apes.
 Additionally, it bears long, cranially and ventrally oriented costal
 (transverse) processes, implying powerful trunk musculature. We interpret
 this combination of features to indicate that A. sediba used its lower
 back in both bipedal and ape-like arboreal positional behaviors, as
 previously suggested based on multiple lines of evidence from other parts
 of the skeleton and reconstructed paleobiology of A. sediba.
description: Data were collected on 3D models using AMIRA and analyzed in R
 Studio.
description: The 3D landmarks are as follows: 
 Superior vertebral body – ventral transverse midline
 Superior vertebral body – central transverse midline
 Superior vertebral body – dorsal transverse midline
 Superior vertebral body – lateral sagittal midline
 Superior vertebral body – ventro-lateral point
 Superior vertebral body – dorso-lateral point (at ventral
 pedicle base) Pedicle – superior midpoint
 Pedicle – superior dorsal point (at ventral base of
 prezygapophysis) Pedicle – medial midpoint
 Pedicle – lateral midpoint Pedicle –
 inferior midpoint <i>Pars
 interarticularis</i> – dorsal midpoint 
 <i>Pars interarticularis</i> – ventral midpoint
 Inferior vertebral body – ventral transverse midline
 Inferior vertebral body – central transverse midline
 Inferior vertebral body – dorsal transverse midline
 Inferior vertebral body – lateral sagittal midline
 Inferior vertebral body - ventro-lateral point
 Inferior vertebral body – dorso-lateral point
 Lumbar transverse process (LTP) – superior medial point (based
 of LTP at pedicle) Lumbar transverse process –
 inferior medial point (based of LTP at pedicle)
 Lumbar transverse process – superior mediolateral
 midpoint Lumbar transverse process – inferior
 mediolateral midpoint Lumbar transverse process –
 superior lateral point Lumbar transverse process –
 inferior lateral point Superior articular facet –
 cranial-most point Mammillary process – dorsal-most
 extension Superior articular facet –
 midpoint Superior articular facet – caudal-most
 point Spinous process – superior ventral point (at
 spinous process base) Spinous process – superior
 sagittal midpoint Spinous process – superior dorsal
 point (tip of spinous process) Spinous process –
 inferior dorsal point (tip of spinous process)
 Spinous process – inferior sagittal midpoint
 Spinous process – inferior ventral point (at spinous process
 base) Lamina – inferior midpoint
 Inferior articular facet – cranial-most point
 Inferior articular facet – midpoint
 Inferior articular facet – caudal-most point
 Inferior articular facet – medial-most point
 Inferior articular facet – lateral-most point
 Superior articular facet – medial-most point
 Superior articular facet – lateral-most point
 Vertebral body – ventral midpoint Vertebral
 body – lateral midpoint Lumbar transverse process –
 ventral extension of base at its midpoint Spinous
 process – lateral-most extension of the spinous process tip
 Lamina – superior midpoint