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The study of tooth morphology is fundamental for the taxonomic and evolutionary comprehension of mammals. However, dental abnormalities can lead to misidentifications and species invalidations. We present two distinctive dental anomalies observed in Myotis riparius: (i) hypodontia, characterized by the absence of the second upper premolar (P3) on both sides of the dental arch in an adult male from Panama, and (ii) polyodontia, characterized by the presence of three upper incisors on one side of the dental arch in an adult male from Brazil. We discuss the genetic and ecological bases of these anomalies and the importance of these case reports for understanding the evolutionary developmental biology of bats. [ABSTRACT FROM AUTHOR]

The Caatinga is an exclusively Brazilian biome, and is the largest and most biodiverse Seasonal Tropical Dry Forest in the world. Despite that, the mammalian fauna, especially small mammals, is the least studied of all Brazilian biomes. In order to fill gaps and provide detailed information on small mammals (Didelphimorphia, Rodentia) in the Caatinga biome, we compiled reliable records focusing on richness, composition and some biometric data. These records came from mammal collections, papers, theses, books, and unpublished data, prioritizing records with vouchers housed in scientific collections. We compiled a total of 3133 records from 816 locations, resulting in a richness of 47 native species (12 marsupials and 35 rodents, plus three exotic rodents, Rattus rattus, Rattus norvegicus, and Mus musculus). This dataset includes records of three new species for the biome and its transition zone: the rodents Calomys mattevii, Holochilus oxe, and Nectomys squamipes. Of the total number of records, 1808 (57.71%) are from consulting activities, 95 (3.03%) are from zoonoses studies and 104 (3.32%) are from the National Plague Service (SNP). All nine Brazilian states with territory in the Caatinga have sampling data for small mammals, but the number of records and localities are unevenly distributed, with the state of Rio Grande do Norte having the lowest number of records and locations sampled. Our dataset is the first of its kind for the Caatinga biome and has considerable potential value for studies of habitat use, landscape ecology, macroecology, biogeography, and conservation. There are no copyright restrictions on the data. Please cite this data paper when the data are used in publications. We also request that researchers and teachers inform us of how they are using the data. [ABSTRACT FROM AUTHOR]

The taxonomy of the oryzomyine genus Neacomys currently is in a state of flux: systematic studies in the last 20 years increased its diversity from four to 16 species, with an additional several undescribed phylogenetic lineages. Despite this progress, morphological variation and species limits remain poorly known for several species groups and complexes within the genus, such as N. tenuipes , N. musseri , and N. dubosti. Here we analyze the variation of morphological characters and morphometric patterns of two new candidate species of Neacomys for northern Venezuela and Pará state, Brazil, that are characterized by the presence of derived carotid circulation, a rare character state for the genus. Analyzed material included holotypes, type series, and/or topotypes of almost all described species of Neacomys , including type series of N. musseri , the holotype of N. tenuipes , and sequenced specimens of N. xingu. Qualitative comparison showed that 25 characters are informative for the distinction of the two new forms, and morphometric analyses corroborated the morphological separation of the new species. Results also point that N. tenuipes might represent a species complex. The new forms are sympatric with other species, including N. tenuipes and N. xingu , and can be identified by a suite of morphological characters, including the presence of a derived carotid pattern and, for the Pará form, by a unique morphology of the first upper molar. We review the occurrence of carotid circulation patterns within Sigmodontinae and discuss its use for the systematics of the subfamily. Further studies involving the new Neacomys species will contribute to understanding the biogeographic patterns and evolutionary trends within this distinct and diverse genus. [ABSTRACT FROM AUTHOR]

Supernumerary teeth are common dental anomalies reported in rodents, mainly occurring distally to molars. We report the first case of mesial hyperdontia in wild-caught sigmodontine: a simplified tooth anterior to the right first lower molar in Neacomys amoenus. It affected the first molar morphology, which exhibits an underdeveloped mesial region with a reduced anterior conulid, a similar pattern observed in early known myomorph fossils, including lineages that still possess the last premolar. However, only lineages without premolar display an elongated first lower molar with a large anteroconid, as observed in extant Myomorpha. During the odontogenesis in myomorphs, the posteriormost vestigial diastemal tooth bud, located at the same locus of the last lower premolar, has its development arrested and merges with the cap of the first molar. This process might have contributed to the development of an increased anteroconid in this lineage. The abnormal Neacomys' atavistic phenotype corroborates the hypothesis that the absorption of the primordium of the last lower premolar had played an important role in the development of first molar's mesial region. Additionally, it also might have promoted the evolutionary transition from a reduced conulid into an enlarged anteroconid, as deduced from the fossil record and developmental evidence [ABSTRACT FROM AUTHOR]

The following text in the Discussion section should read: "Taxa with derived circulation patterns occur throughout most sigmodontine tribes, among Ichthyomyini ( I Anotomys i , I Ichtyomys i and I Rheomys i ), Euneomyini ( I Neotomys i ), Reithrodontini ( I Reithrodon i ), Sigmodontini ( I Sigmodon i ), Wiedomyini ( I Juliomys i ), and especially among the Thomasomyini ( I Chilomys i , I Rhagomys i , I Rhipidomys i , I Thomasomys i ) and Oryzomyini ( I Aegialomys i , I Cerradomys i , I Drymoreomys i , I Eremoryzomys i , I Holochilus i , I Hylaeamys i , I Lundomys i , I Melanomys i , I Microakodontomys i , I Neacomys i , I Nectomys i , I Nesoryzomys i , I Oecomys i , I Oligoryzomys i , I Oryzomys i , I Pseudoryzomys i , I Scolomys i , I Sooretamys i , I Tanyuromys i , I Zygodontomys i )" instead of "Taxa with derived circulation patterns occur throughout most sigmodontine tribes, among Ichthyomyini ( I Ichtyomys i , I Anotonomys i ), Euneomyini ( I Neotomys i ), Reithrodontini ( I Reithrodon i ), Sigmodontini ( I Sigmodon i ), Wiedomyini ( I Juliomys i ), and especially among the Thomasomyini ( I Chilomys i , I Rhagomys i , I Rhipidomys i , I Thomasomys i ) and Oryzomyini ( I Drymoreomys i , I Eremoryzomys i , I Holochilus i , I Hylaeamys i , I Melanomys i , I Microakodontomys i , I Neacomys i , I Nectomys i , I Nesoryzomys i , I Oryzomys i , I Pseudoryzomys i , I Sooretamys i , I Tanyuromys i , I Oligoryzomys i , I Oecomys i , I Zygodontomys i )". In addition, "derived circulation patterns (patterns 2 and 3 of Voss 1988) are present in 26 of the 87 genera included in the subfamily" should read: "derived circulation patterns (patterns 2 and 3 of Voss 1988) are present in 31 of the 87 genera included in the subfamily". [Extracted from the article]