Diplochaetetes mexicanus is an extinct species of cirratulid polychaete within the genus Diplochaetetes from the Pacific coasts of the Americas, found mostly in Oligocene and Miocene sedimentary rocks.

[1] Later findings have extended its paleogeographic distribution up to Peru.

[2] Initially described as a sponge, the similarity of these aggregates with present-day Dodecaceria bioconstructions from the exact same areas has led researchers to classify these fossils as cirratulid bioconstructions.

[3][4] Both fossil Diplochaetetes and recent Dodecaceria bioconstructions retain identical double-phased biomineralization characteristics, but the possible synonymity of these species is currently subject to debate.

[5] Up until the discovery of Diplochaetetes mexicanus, fossil cirratulid bioconstructions were only known from Eocene sediments in Namibia.