Agathaeromys
Agathaeromys is an extinct genus of oryzomyine rodents from the Pleistocene of Bonaire, Netherlands Antilles. Two species are known, which differ in size and some details of tooth morphology. The larger A. donovani, the type species, is known from hundreds of teeth that are probably 900,000 to 540,000 years old, found in four localities. A. praeuniversitatis, the smaller species, is known from 35 teeth found in a single fossil site, which is probably 540,000 to 230,000 years old.
Although material of Agathaeromys was first described in 1959, the genus was not formally named and diagnosed until 2010. It probably belongs to "clade D" within the oryzomyine group, together with many other island-dwelling species. The molars of both species possess several accessory crests in addition to the main cusps. In addition to some differences in features of the chewing surface of the molars, A. donovani has more roots on its lower molars than does A. praeuniversitatis.
The name Agathaeromys combines the Greek words ἀγαθός agathos "good", ἀήρ aêr "air", and μυς mys "mouse", referring to the name of the island of Bonaire and to the "fresh air" that contributions by Marcelo Weksler and colleagues brought to the classification of Oryzomyini.[1] The name donovani honors Stephen Donovan for his contributions to the scientific knowledge of the Caribbean[2] and praeuniversitatis refers to Leiden University's Pre-University College, which provided an opportunity for Zijlstra to participate in the project that led to the identification of Agathaeromys.[3]
Material of Agathaeromys was first described by Dirk Hooijer in 1959 in the same paper that first named the extinct giant rat of Curaçao, Megalomys curazensis. Hooijer described a few fossil teeth and jaws from Fontein, Bonaire, as an indeterminate species of Thomasomys ("Thomasomys sp.") and considered them to be similar to species now placed in Delomys.[4] In his 1974 monograph on the geology of the ABC islands (Aruba, Bonaire, and Curaçao—three Dutch islands off northwestern Venezuela), Paul Henri de Buisonjé listed Thomasomys sp. from additional fossil sites on Bonaire and additionally mentioned Oryzomys sp. from a different Bonaire site, Seroe Grandi.[5] Although the Bonaire material represented one of the few fossil records of Thomasomys, it was only rarely mentioned in the literature.[6]
In 2010, Jelle Zijlstra, Anneke Madern, and Lars van den Hoek Ostende reviewed the material. They considered it unlikely that the Bonaire "Thomasomys" would belong to the southern Brazilian genus Delomys or to Thomasomys, which occurs only in the mountains of the Andes.[6] Using a cladistic analysis of the Sigmodontinae, they provided evidence that the Bonaire material belonged to the tribe Oryzomyini, rather than Thomasomyini (which includes Thomasomys).[7] They carried out another cladistic analysis focused on Oryzomyini, which suggested that the Bonaire "Thomasomys" and the material from Seroe Grandi (De Buisonjé's "Oryzomys sp.") were closely related, but distinct from any recognized oryzomyine genus.[8] Therefore, they named a new oryzomyine genus, Agathaeromys, with two species: Agathaeromys donovani (type species) for the material previously identified as Thomasomys; and Agathaeromys praeuniversitatis for the material from Seroe Grandi.[9]
