Fossil mammals of Ecuador

Mammals are among the oldest vertebrates on the planet, with an evolutionary history dating back more than 300 million years (Rowe, 1988). Abundant fossil evidence from across the globe tells this long story; however, Ecuador is still a poorly known country in terms of its mammalian fossil record, and it is one of the least explored in this area in all South America. Notwithstanding the scarcity of this knowledge compared to that of other countries in the region, in the middle of the last century, a compendium on fossil mammals was published that has not been replicated by any other Neotropical country. I am referring to Les mammifères Pléistocènes de la République de l'Equateur [Pleistocene mammals of the Republic of Ecuador] (Hoffstetter, 1952), a volume of almost 400 pages that changed the history of paleontology in the country. However, after Hoffstetter’s 1952 publication, little progress was made in paleontology in Ecuador in the following fifty years. At present, the study of fossil mammals is still little-explored; for a century, active paleontologists working in the country have been counted on the fingers of one hand. Since the creation of Mammalia aequatorialis, we also set out to contribute to the knowledge of fossil mammals. Sometimes forgotten and separated from living forms, they share the same diagnostic features, the same ancestors, and in many cases are part of the same phylogenetic groups. For this reason, the central article of this issue is the “Catalog of the fossil mammals of the province of Santa Elena,” a review article that summarizes all the available knowledge on these vertebrates for a specific region of Ecuador. I hope that contributions such as the present one will encourage the development of new paleontological research and motivate the elaboration of similar articles for other provinces of the country or regions in Latin America. Our seventh year of circulation also brings another important novelty. In 2025, Mammalia aequatorialis has become a biannual journal. We receive a large amount of material, and our reach extends over a large part of Latin America, from Mexico to Argentina. Therefore, starting this year, we will publish an issue every six months: one in January and another in July.This issue also includes an article and several notes on one of the most emblematic groups of mammals: the felines. We present an article on the ingestion of grasses by jaguars in the Ecuadorian Amazon and short articles that contribute to the knowledge of three species of small cats, with data on distribution, diet, activity, and internal anatomy. The issue also contributes information on small mammals. One article extends the distribution of Marmosa perplexa, one of the least known marsupials in the Neotropics, and another discusses the taxonomic diversity of the genus Thomasomys, a highly diverse and no less complex group of Andean mice. We also include notes on the diet of a squirrel species of the genus Hadrosciurus and new records of the weasel Neogale frenata in southwestern Ecuador.