Analyzing the family tree of goby fish: The oldest on the island

Fossilized skeleton of †Paralates chapelcornerensis, the oldest representative of the Odontobutidae family
© Reichenbacher Group

Gobies are one of the most diverse and species-rich groups of fish in the world today. Around the globe, these diminutive fish can be found in virtually any and every habitat. Their family (or phylogenetic) tree is made up of nine families with a total of over 2,000 species. The basal families – Odontobutidae and Rhyacichthyidae – comprise only 32 species and are native to Southeast Asia. Within the family tree, they constitute the sister group to the other goby families. Yet, only three species of these two families were hitherto known from the fossil record; they werde found in Japan, China and New Zealand. Now, however, new finds of the goby †Paralates chapelcornerensis and the newly described species †Paralates simpsoni (named after Martin Simpson, who discovered the new fossil) from the Isle of Wight in the English Channel – dating back some 36 million years to the Late Eocene – have yielded an astonishing discovery: The shape of the fossils’ otoliths matched those of the Odontobutidae. “That surprised us, because today you only find these fish in Southeast Asia, not off the coast of Britain,” says Elena Bauer, a doctoral researcher in paleontology at LMU and lead author of the study. Bauer notes that we do not yet have a cogent explanation for this phenomenon, which shows that the evolution and the paleogeographical history of the gobies is far more complex than the biogeography of today’s fish might suggest.

An atlas of bone models

In contrast, no definitive conclusions could initially be drawn from its fossilized skeletons of †Paralates. To date, too little research has been done into the osteology of the Odontobutidae, nor has their osteology been clearly distinguished from the Rhyacichthyidae, the most closely related family. Therefore, there were no defined characters that could be used for the phylogenetic placement of the fossil. Earlier publications have placed †Paralates close to the Odontobutidae and Rhyacichthyidae but were unable to be more precise. In collaboration with colleagues from the Bavarian State Collection of Zoology (SNSB-ZSM) the researchers have now been able to produce an elaborate set of 3D bone models (based on microCT scans) for all available representatives of the two families and compile them in an atlas of images available in open access. “Fossils usually preserve only a fraction of all the bones, so for the purposes of our study we restricted ourselves to the bones that were preserved best in the fossils of †Paralates: bones of the skull and the upper jaw, but also the first vertebra and the pelvic girdle,” says Bettina Reichenbacher, Professor of Paleontology at LMU.

Artist’s impression of †Paralates simpsoni (at left) and †Paralates chapelcornerensis (at right) near the Isle of Wight in the late Eocene, around 36 million years ago | © Elena Bauer

To be able to assign †Paralates to one of the two families, characteristics that distinguish Odontobutidae from Rhyacichthyidae have now been identified based on these bone models. The findings were compared with the fossils of †Paralates and the resultant information was incorporated into the latest character matrix, which contains characters for the analysis of the phylogenetic tree of all goby families. According to the new family tree analysis, the new skeletal characteristics now also identify †Paralates as a member of the Odontobutidae. “We have thus made a groundbreaking contribution to identifying fossils in these basal families,” Bauer asserts. “Our family tree shows that †Paralates belongs to the Odontobutidae, making it the oldest representative of this family.”

Elena Bauer, Alexander F. Cerwenka, Ulrich K. Schliewen, and Bettina Reichenbacher: New osteological characteristics identify the first stem sleeper goby (Gobioidei, Odontobutidae) from the Upper Eocene. Papers in Palaeontology, 2025