Transposed one roundish division about the object, an early fossil (9)

I believe the answer is:

trilobite

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'an early fossil' is the definition.
'trilobite' can be an answer for 'fossil' (extinct creatures represented in the fossil record). I am unsure of the 'an early' bit.

'transposed one roundish division about the object' is the wordplay.
'transposed one roundish division' becomes 'trilobe' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'about' is an insertion indicator.
'the object' becomes 'it' (I've seen this in other clues).
'trilobe' placed around 'it' is 'TRILOBITE'.

Can you help me to learn more?

(Other definitions for trilobite that I've seen before include "Extinct animal" , "Bitter oil (anag.)" , "find on Lyme Regis beach?" , "Extinct arthropod" , "Abundant fossil" .)

I've seen this clue in the Sydney Morning Herald.

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