Renous S
Gegenbaurs Morphol Jahrb. 1977;123(6):881-901.
When the dimensional reduction of the hind limb begins, a first caudal displacement of the lombar part of the lombo-sacral plexus - which involves the loss of the first root of the sacral part -- appears with a threshold in the increase in the number of presacral vertebrae. This a first indication of the serpentiform tendancy. Others thresholds can conduct to produce the disappearance of the sacral vertebrae and sacral root. The qualitative reduction only concerns the terminal branches of the plexus and does not seem to be associated with the vertebral elongation. If a caudo-proximal reduction of the brachial plexus occurs early in the lepidosaurian line and exists in all the Squamata, even in the Iguana which have well developed limbs, it is not the same for the reduction of the lombo-sacral plexus which does not appear in these Iguana. At last, if the reduction modalities of the both plexus are often differents, their supposed displacements facilitate the extension of the intermediate vertebral region.
当后肢开始发生尺寸减小时，腰骶丛腰段的首次尾向移位——这涉及骶段第一神经根的丧失——在骶前椎骨数量增加时达到一个阈值后出现。这是蛇形趋势的首个迹象。其他阈值可能导致骶椎和骶神经根消失。定性减少仅涉及神经丛的终末分支，似乎与椎体延长无关。如果在鳞龙类谱系中臂丛的尾近端减少在早期就已出现且存在于所有有鳞目动物中，甚至在四肢发达的鬣蜥中也存在，那么腰骶丛的减少情况则不同，在这些鬣蜥中并未出现。最后，如果两个神经丛的减少方式常常不同，那么它们假定的移位会促进中间椎体区域的延伸。
