[5] Tetracarpaea has an odd mix of characters, and during the nineteenth and twentieth centuries, its affinities remained obscure.

A placenta runs along each side of the suture and bears 1 to 3 rows of numerous, tiny ovules.

[10] At that time, he wrote: This beautiful little shrub is altogether new to me: but much as it differs in certain characters, both of the foliage and fructification, from the Order Cunoniaceae, I think it may safely be referred to it.

The 4 carpels, which have suggested the Generic name, are perfectly free even in the earliest state of the ovary.Hooker did not use the modern system of suffixes for taxonomic ranks.

From that time, until the end of the twentieth century, most authors put it in either Cunoniaceae, Escalloniaceae, or Saxifragaceae.

[12] Escalloniaceae is even more distant from Tetracarpaea, being a member of an asterid group called the campanulids.

[6] In 1865, George Bentham and Joseph Hooker moved Tetracarpaea from Cunoniaceae to Escalloniaceae.

[16] Adolf Engler put Tetracarpaea in Saxifragaceae, but defined the latter so widely that it included what is now Escalloniaceae as a subfamily.

Armen Takhtajan has at different times put Tetracarpaea in Escalloniaceae and in Tetracarpaeaceae.

[8] In 1988, Matthew H. Hils, et alii, did a detailed study of the anatomy of the wood and leaves of Tetracarpaea.

The first molecular phylogenetic studies of the order Saxifragales were inconclusive because their results had only weak statistical support.

In 2008, by comparing DNA sequences of the entire invert repeat region of the chloroplast genome, Shuguang Jian et alii were able to determine the position of Tetracarpaea within Saxifragales.