According to Roderick S. Bucknell, in his Conditioned Arising Evolves: Variation and Change in Textual Accounts of the Paticca-samuppada Doctrine, there are four versions of dependent origination formulations, i.e., the standard version of 12 nidanas, looped version of Mahanidana Sutta (DN 15 and it’s parallel in the Chinese Agamas), a Sutta-nipata version found in Snp 3.12, and branched version (origination of consciousness depends on sense-bases and its objects) in many other suttas (such as SN 12.43 = SN 35.106 and MN 148).
He said that the loop version is a faulty form of branched version because of oral transmission of the teaching (with assuming that nama-rupa is a totality of six sense objects). The Snp version is an earlier form of standard version which omitted nama-rupa and salayatana. Finally, he concluded that the early version of dependent origination is an ancestor formulation which includes consciousness as sense-consciousness depended on sense-bases and its objects (from branched version) as well as consciousness as rebirth consciousness depended on volitional activities (from Snp version):
In this postulated earlier form of the standard version the arising of vinnana is traced to two different sources: on one hand to the sense organs and their objects (salayatana and nama-rupa), and on the other hand to activities (sankhara), which in their turn are conditioned by ignorance (avijja). The branched version represents the former source, and the Sn version is now seen to represent the other source (activities and ignorance).