Hippocampus sarmaticus
Temporal range: Lower Miocene
Hippocampus slovenicus
A restoration of Hippocampus slovenicus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Syngnathiformes
Family: Syngnathidae
Subfamily: Hippocampinae
Genus: Hippocampus
Species: H. slovenicus
Binomial name
Hippocampus slovenicus
Žalohar, Hiti, Križnar, 2009

Hippocampus slovenicus is an extinct species of seahorse found in 2005 in the coprolitic horizon of the Tunjice hills Lagerstätte in Slovenia along with remains of the related species Hippocampus sarmaticus. The horizon dates 13 million years back to the lower Sarmatian during the middle Miocene period, making the two species the earlier known seahorse fossils in the world. The remains consist mostly of juvenile specimens and of head and backbones of adults.

The animals are believed to have lived among seagrasses and macroalgae in the temperate shallow coastal waters of the western part of the central Paratethys.