Loggerhead sea turtle turtle is debated, but most authors consider it a single polymorphic species. Molecular genetics has confirmed hybridization of the loggerhead sea turtle with the Kemp's ridley sea turtle, hawksbill sea turtle, and green sea turtles. The extent of natural hybridization is not yet determined; however, second-generation hybrids have been reported, suggesting some hybrids are fertile. Although evidence is lacking, modern sea turtles probably descended from a single common ancestor during the Cretaceous period. Like all other sea turtles except the leatherback, loggerheads are members of the ancient family Cheloniidae, and appeared about 40 million years ago. Of the six species
Varieties of Chinese dialect of northern Fujian is a minimal example. With the exception of , which is often merged with the zero initial, the initials of this dialect are present in all Chinese varieties, although several varieties do not distinguish from . However, most varieties have additional initials, due to a combination of innovations and retention of distinctions from Middle Chinese: Chinese finals may be analysed as an optional medial glide, a main vowel and an optional coda. Conservative vowel systems, such as those of Gan dialects, have high vowels , and , which also function as medials, mid vowels and ,