The phrase "are extremely variable in" is correct and usable in written English.
You can use it to describe a wide range of differences or fluctuations in a particular context or subject matter.
Example: "The results of the experiment are extremely variable in their outcomes, indicating a need for further investigation."
Alternatives: "are highly inconsistent in" or "exhibit significant variation in".
Snake-eyed skinks are extremely variable in colour and are the only skinks with a fixed plate (spectacle) on their eyes instead of a movable eyelid.
Sclereids are extremely variable in shape and are present in various tissues of the plant such as the periderm, cortex, pith, xylem, and phloem.
Exon 12 mutations on the other hands are extremely variable in sequence [10] and so far restricted to polycythaemia patients.
The analysis of the secretome is the method of choice for covering the entity of extracellular virulence factors which are extremely variable in different S. aureus strains.
In general, it is assumed that abnormalities in HLA expression are extremely variable in human cancers ranging from 0 to 90% [12].
Human spinal cord injuries are extremely variable in their extent and pathology [17], therefore a reproducible method of producing spinal trauma is required, otherwise potentially useful therapies will be lost in the haze of variability.
On the one hand, seasonal influenza is extremely variable in its actual characteristics (cf. e.g. the enormous variability in the age-dependent attack rates shown in Figure 5a), hence, findings reported in older studies can only serve as heuristics and not as precise parameter estimates.
Due to the fracture network, the flow velocity is extremely variable in different regions and it can be described by the temporal scale analysis.
We know for example that colour is extremely variable in many species and some occasional colour types keep recurring (like all black forms or albinos) so using this to help define a species is a bad idea, but something more consistent and less variable (like the number of vertebrae or number of toes) is likely to form a good character.
The hemipenis is extremely variable in its overall appearance and structure; the cloaca of the female is often similarly constructed, which thus prevents cross-fertilization by males of related species.
In contrast, alluvium beneath the tread of a depositional terrace can be extremely variable in thickness and usually exceeds any reasonable scouring depth of the associated river; moreover, the eroded surface in the bedrock beneath the fill can be very irregular even though the surface of the terrace tread is flat.
