There should have existed transitional forms, which exhibit at least some typical features of basal snake anatomy.
Instead of a reasonable and fair scientific debate, McMenamin’s hypothesis has been ridiculed by other scientists and science journalists.
The breaking of the conserved number of cervical vertebrae is hard to reconcile with an unguided evolutionary mechanism.
This is not how good science is supposed to work but is rather typical for pseudoscience that shields itself against empirical falsification.
This phenomenon could rightfully be called a Tertiary Butterfly Explosion analogous to the Cambrian Explosion of animal phyla.