Roses, known for their beauty and economic value, have been important to humans for thousands of years, and have been present in vegetation worldwide for much longer.  Based on research from the last decade, the crown age of Rosaceae is estimated to be between 95.09 - 101.6 Ma, and fossil occurrences indicate that the genus was present in North America by the late Eocene (55.8–48.6Ma). Today, there are more than 100 species of wild roses that can be found across the incredibly diverse temperate regions of the Northern Hemisphere. Arguably one of the most distinguishing features of the genus Rosa besides its showy flowers are the spiky emergences that grow from the stem. However, these emergences are not the thorns that have been used in popular metaphors for decades. They are actually prickles, projections containing no vascular tissue and can be broken off the stem fairly easily. Prickles are a distinctive characteristic of the genus and contain helpful morphological information to consider when trying to identify a fossil.  Often, fossil prickles are recovered as disarticulate individuals. They are often assigned to Rosa based on observation of overall morphology and presence of other reproductive or vegetative fossils indicative of Rosa, like the ‘rosehip’ accessory fruits and compound leaves. Other Rosaceous genera bear prickles as well, and of these, Rubus is often found in similar habitats to Rosa. However, fossil prickles are rarely if ever assigned to Rubus. Here, we address with observational study, ontological discussion, and landmark-based morphometrics the differences between the prickles of Rubus  and Rosa and how these differences may be applicable to fossil determinations in order to aid studies of ancient diversity and evolution of the Rosaceae.