A team of researchers led by Gertrud Rößner, a paleontologist at the Bavarian State Collection of Paleontology and Geology (SNSB), has uncovered a significant prehistoric dolphin species, offering fresh insights into the evolution of toothed whales. The newly identified species, Romaleodelphis pollerspoecki, was discovered from a fossilized skull found in Upper Austria near Linz, and its inner ear structure suggests that it possessed remarkable hearing abilities, especially in the high-frequency range, similar to modern dolphins. The findings were published in the Journal of Vertebrate Paleontology.
The fossil dates back about 22 million years to the Miocene epoch, when the Paratethys Sea, a shallow inland sea, extended across much of Europe, including what is now Upper Austria. During this period, the area hosted a rich diversity of marine life, from microorganisms and algae to snails, mussels, squid relatives, and various fish species. This newly discovered dolphin, part of a coastal ecosystem, is believed to have been an adept predator within this environment.
The fossil itself is fragmentary, consisting only of a compressed and incomplete skull with an elongated snout and 102 uniform teeth. Despite the challenging condition of the fossil, which required advanced imaging techniques for proper analysis, the research team was able to assign it to a new genus and species, naming it Romaleodelphis pollerspoecki in honor of its discoverer, Jürgen Pollerspöck, who found the fossil in 1980 and later donated it for further study.
Detailed comparative analysis and computer modeling of the dolphin’s relationships to other fossil species revealed that Romaleodelphis is likely related to an extinct group of dolphins known as the Chilcacetus clade, which is mainly known from the northeastern Pacific and South America. This discovery significantly expands the geographic range of this lineage, suggesting that early toothed whales might have spread across diverse regions of the world much earlier than previously thought. According to Dr. Rößner, this new species could offer vital clues about the origin and evolution of the Chilcacetus lineage during the earliest Miocene.
One of the most exciting aspects of this discovery is the reconstruction of the dolphin’s inner ear, which was achieved using micro-computed tomography scans. This advanced imaging allowed the researchers to carefully examine the skull’s internal features despite its severe compression. The inner ear’s well-preserved bony labyrinth indicated that Romaleodelphis pollerspoecki had the ability to hear high-frequency sounds, a key feature for modern dolphins, such as porpoises. This suggests that, like today’s toothed whales, Romaleodelphis could have used echolocation for navigation and communication, abilities that would have helped it survive and thrive in its aquatic environment.
This discovery makes Romaleodelphis pollerspoecki one of the earliest known dolphins to exhibit advanced hearing capabilities, aligning it with modern dolphins that communicate in frequencies beyond the hearing range of their predators. The presence of high-frequency hearing in a dolphin from the early Miocene also hints at the early development of echolocation, an essential sensory adaptation in modern cetaceans for locating prey and navigating murky waters.
The fossil’s discovery and subsequent study provide crucial insights into the early evolution of toothed whales, showing that key adaptations in hearing, which would later define dolphins and other cetaceans, were already emerging millions of years ago. These findings reshape our understanding of how dolphins and their relatives evolved to become such highly specialized marine mammals.
The Romaleodelphis pollerspoecki fossil, now housed at the Bavarian State Collection of Paleontology and Geology, represents a significant leap forward in the study of prehistoric marine life. It provides a rare glimpse into the evolutionary development of one of the most intelligent and acoustically specialized animal groups on Earth, highlighting the long and complex evolutionary history of dolphins and their kin.