 Teiidae

Teiidae is a family of lizards within Lacertoidea, including the whiptails of Aspidoscelis. It is a separate lineage from Gymnophthalmidae. Beyond their place in reptile classification, some whiptails offer a striking example of parthenogenesis: females produce offspring without fertilization.^[ref]

In a 2010 study of parthenogenetic Aspidoscelis, investigators asked how eggs could retain the parental complement of chromosomes and preserve heterozygosity. Chromosome imaging and fluorescent probes showed an extra premeiotic doubling, followed by pairing of genetically identical chromosome copies. The cells still underwent meiosis and chromosomal crossover; reproduction did not simply bypass the entire meiotic program.^[ref]

A simplified genetic example explains the significance. Begin with distinguishable chromosome versions $A$ and $B$. After copying, matching $A$ with another $A$ and $B$ with another $B$ permits exchange between equivalent copies while retaining both parental versions in the unreduced egg. This differs from mechanisms that discard one version and thereby lose heterozygosity. The finding concerns particular parthenogenetic species; it does not make every member of Teiidae an asexual animal.