Rocks of the Rio Turbio Formation, exposed in southern Patagonia, Argentina, represent one of very few occurrences of Eocene rocks in the region. Decapod crustaceans collected from the unit include one species of thalassinidean mud shrimp; Turbiocheir minutospinata, new genus, new species; and three species of brachyurans; Raninoides rioturbiensis, new species; Megokkos patagoniensis, new species; and Nitotacarcinus antipodes, new species. The three brachyuran genera are also known from species in the Northeast Pacific, suggesting an amphitropical distributional pattern.

A new species of the cylindrodontid rodent Tuscahomys Dawson and Beard, 2007, is very well represented by maxillary, mandibular, and dental remains from the late early Wasatchian Smiley Draw local fauna in the Great Divide Basin of Sweetwater County, Wyoming. Tuscahomys walshi, new species, is more derived than earlier Wasatchian members of the genus in showing greater lingual hypsodonty on its upper cheek teeth and a more discrete hypocone on P⁴, but less derived than its Bridgerian relative Mysops Leidy, 1871, in having less lingually hypsodont upper cheek teeth and a less trenchant protoloph on P⁴. Tuscahomys walshi thus partly fills a previously existing gap in the early fossil record of cylindrodontids. Tuscahomys shows an unusual pattern of faunal association and relative abundance. It typically occurs as a surprisingly common element of some, but by no means all, early Wasatchian faunas, and it frequently co-occurs with the “condylarths” Meniscotherium Cope, 1874, and Haplomylus Matthew, 1915. This highly selective pattern of relative abundance and faunal association suggests some form of niche specificity for early cylindrodontids, the details of which remain unknown. Phylogenetic analysis supports a relatively basal position for Tuscahomys (and Cylindrodontidae) within the Rodentia, rendering any direct derivation of earliest Wasatchian Tuscahomys from older North American paramyids suspect. An Asian origin for Cylindrodontidae, with subsequent dispersal of Tuscahomys into North America at or near the Clarkforkian-Wasatchian boundary, cannot be dismissed.

Short term surveys for small mammals in Guatemala and Honduras during 1992–2009 provided important new records for 12 taxa of shrews from 24 localities. These locality records expand the known geographic distributions for five species and for the genus Sorex Linnaeus, 1758: the geographic range of Cryptotis goodwini Jackson, 1933, now includes the Sierra de las Minas, Guatemala, and several isolated highlands in western Honduras; the known distribution of Cryptotis mayensis (Merriam, 1901) is increased with the first definite modern record for this shrew from Guatemala; Cryptotis merriami Choate, 1970, is now known to occur in the Sierra de las Minas and the Sierra del Merendón, Guatemala, as well as the isolated Sierra de Omoa and Montana de La Muralla in Honduras, and its documented elevational range (600–1720 m) is expanded; records of Sorex veraepacis Alston, 1877, expand the known distribution of this species to include the Sierra de Yalijux, Guatemala; and discovery of Sorex salvini Merriam, 1897, at Celaque, Honduras (1825–3110 m), represents a considerable extension of the geographic range of the species, and it is the first record of the genus Sorex from Honduras. In addition, the first record of potential syntopy among C. goodwini, C merriami, and Cryptotis orophilus (J.A. Allen, 1895), is reported at an elevation of 1430 m in the Sierra de Celaque, Honduras. Information associated with these records contributes substantially to knowledge of habitat use, elevational distributions, reproductive patterns, diet, and parasites of the species encountered. General patterns include the first evidence that Neotropical species of soricids have smaller litters than their temperate congeners.

Four fossil rodent taxa are described from a new locality in the Oligocene Continental and Transitional Marine Deposits outcropping in the vicinity of Zallah, Sirt Basin, central Libya. These rodents belong to the infraorder Hystricognathi Tullberg, 1899, and are distributed amongst four genera (Metaphiomys Osborn, 1908; Phiocricetomys Wood, 1968; Talahphiomys Jaeger et al., 2010; and Neophiomys , new genus) that include one new species, Phiocricetomys atavus, and one new combination, Neophiomys paraphiomyoides (Wood, 1968), formerly Phiomys paraphiomyoides Wood, 1968. The specimens described here have profound implications for the phylogenetic and systematic status of early hystricognathous rodents and paleogeographical debates regarding their origin. Based on a cladistic analysis, Waslamys attiai Sallam et al, 2009, is transferred to the genus Protophiomys Jaeger et al., 1985, as Protophiomys attiai (Sallam et al, 2009), new combination. That species is the type species of the monobasic genus Waslamys Sallam et al., 2009, and the new combination places Waslamys Sallam et al., 2009, as a new synonym of Protophiomys Jaeger et al., 1985. The genus Protophiomys (including Waslamys) is classified in Protophiomyinae, new subfamily.

Some of the Libyan species reported here are morphologically close to hystricognathous rodent taxa described from the latest Eocene—early Oligocene Jebel Qatrani Formation of the Fayum in Egypt, suggesting a similar age for the Zallah rodent-bearing stratum. Correlation of the Zallah magnetic polarity stratigraphic section to the Geomagnetic Polarity Time Scale relies on biostratigraphic data. The preferred correlation with Chron C13 implies an earliest Oligocene age for the Zallah fauna. The Zallah assemblage of Oligocene hystricognathous rodents considerably improves our knowledge of the evolutionary history of African rodents. Likewise, positioning the Zallah fauna within a consistent chronological framework constitutes an important advance toward the goal of achieving a comprehensive network correlating Paleogene Afro-Arabian mammal localities.