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Why do different scientific sources sometimes use different classifications for the same group of lizards?

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A diagram showing the hierarchy of animal classification in taxonomy, with colored boxes arranged from broadest to most specific: domain, kingdom, phylum, class, order, family, genus, and species. — taxonomy Animals and other organisms are classified within a succession of nested groups that ranges from the general to the particular.

Different scientific sources often use varying classifications for the same group of lizards because the field of taxonomy is currently undergoing a significant transition.1

Historically, classification relied on the Linnean approach, which groups organisms based on visible anatomical structures. However, modern biology is shifting toward a phylogenetic (or cladistic) approach, which categorizes organisms based on their evolutionary relationships and common ancestry. This shift is driven by rapid advances in gene sequencing and DNA analysis, which frequently reveal that traditional groupings do not accurately reflect evolutionary history.123

Because this research is ongoing, several factors contribute to the lack of a single, standardized classification:

New Data: The discovery of new fossil specimens and the application of new analytical techniques, such as computed tomography, constantly provide fresh insights that may contradict previous findings.3
Methodological Debate: Systematists continue to debate how to best represent these relationships, with some abandoning formal Linnean ranks (like family or order) in favor of hierarchical lists that better reflect branching evolutionary events.13
Scientific Process: In science, facts are treated as hypotheses that are subject to reexamination. As new evidence emerges, classifications are updated, leading to a period of instability until a broader consensus is reached.3