Fossil fish remains from Gona, Ethiopia, were recovered along with those of other vertebrates by the Gona Paleoanthropological Research Project team (GPRP) in the late 1990s and early 2000s from Pliocene and Pleistocene deposits. The early Pliocene fish were recovered from natural depositional contexts, whereas the early Pleistocene fish were associated almost completely with archeological contexts. Analysis of the fossils provides new information on the Pliocene and Pleistocene fish taxa from deposits associated with the Awash River system in the Afar Depression, Ethiopia. Six families are represented in the fossil assemblages, including one not previously reported from the Pliocene Awash River system. Based on the methodology of a previous study, we test the accuracy of using habitat preferences of modern fish taxa to infer the preferences of the same fossil taxon. Our findings contribute to the reconstruction of the paleoecology of the Pliocene Awash river and lakes. The presence of several hyperostotic cichlid bones in both the Gona and Middle Awash project areas indicates that periods of stability in the lakes and rivers of the Awash River system were punctuated by occasional periods of extreme changes in water levels and water chemistry, resulting in intense soda conditions, which would eradicate most fish taxa. Fish bones recovered from the localities with archeological contexts differed in taxonomic composition and diversity from the naturally deposited assemblages, suggesting the possibility that these remains were selected and accumulated by humans.

Fossils of drepanosauromorphs, a clade of non-saurian diapsids, were once considered relatively rare in the Chinle Formation of the southwestern United States as well as in Upper Triassic rocks globally. Recent discoveries have shown that there are at least four drepanosauromorph taxa present in the Chinle Formation including Dolabrosaurus aquatilis, Drepanosaurus sp., Ancistronychus paradoxus, and a new genus and species described here, Skybalonyx skapter. This new taxon is represented by disarticulated manual unguals and is preserved in a microvertebrate bearing bone-bed in the Blue Mesa Member (∼223–220 Ma) of the Chinle Formation at Petrified Forest National Park, which was deposited in a fluvio-lacustrine setting in equatorial Pangaea during the mid-Norian. Different types of substrate use have been hypothesized for the Drepanosauromorpha. By performing discriminant function analyses using the manual unguals of 173 mammal and 13 reptile species with known substrate use, we hope to infer the ecomorphology of drepanosauromorphs. We found that the enlarged second manual unguals of Drepanosaurus sp. are similar to hook-and-pull digging taxa (e.g., Tamandua mexicana and Cyclopes didactylus) although the smaller manual unguals referred to this taxon (likely pertaining to digits other than digit II) are similar to modern arboreal taxa. Our results support the inference of arboreality in some drepanosauromorph species. However, we found that the manual unguals of Ancistronychus paradoxus and Skybalonyx skapter fit within the range of variation of modern fossorial and subterranean taxa, which expands the functional diversity of the Drepanosauromorpha within the Chinle Formation.

A kannemeyeriiform dicynodont is described on the basis of an occipital plate from the upper Fremouw Formation (Middle Triassic) Gordon Valley locality in the Beardmore Glacier region of Antarctica. The Antarctic specimen is comparable in size to Kannemeyeria simocephalus from the well-known Cynognathus Assemblage Zone of the Beaufort Group of South Africa, and represents the largest therapsid currently known from the upper Fremouw Formation. The presence of an occipital condyle with distinct contributions from the exoccipital and the basioccipital; a wide, tri-radiate occipital condyle; and a well-developed tympanic process of the paroccipital, which is situated below the level of the occipital condyle, represent a combination of character states hitherto unknown among Kannemeyeriiformes. Combined with the possible autapomorphic feature of slender, dorsoventrally elongate basal tubera, this may suggest the Antarctic specimen represents a new kannemeyeriiform taxon. This specimen represents the most complete, and only the fourth definitive, dicynodont specimen known from the upper Fremouw Formation, and the contradictory phylogenetic character data from these specimens adds support for the presence of multiple (at least two) kannemeyeriiform taxa within the upper Fremouw tetrapod assemblage. Taken together, these kannemeyeriiform specimens provide additional support for a correlation with the Cynognathus Assemblage Zone, particularly the Trirachodon-Kannemeyeria or Cricodon-Ufudocyclops subzones (= subzones B or C), as well as an Anisian or younger age for the upper Fremouw tetrapod fauna.

Nonmammaliaform cynodonts were a diverse group of Permo-Triassic synapsids whose morphological evolution documented the beginning of many classic mammalian traits. Here, we describe a new basal cynodont from the upper Permian Madumabisa Mudstone Formation of Zambia's Luangwa Basin as Nshimbodon muchingaensis gen. et sp. nov. The holotype, a relatively complete and undistorted cranium and articulated mandible with associated postcranial elements, is interpreted as the most complete and well-preserved example of a charassognathid cynodont, and preserves hitherto unknown details of charassognathid endocranial and postcranial anatomy. A phylogenetic analysis of 111 morphological characters from 25 therapsid taxa (including 15 Permo-Triassic cynodonts) supports a sister-taxon relationship between Nshimbodon and Abdalodon, including them with Charassognathus in a monophyletic Charassognathidae, and placing the family near the base of Cynodontia. In addition to its phylogenetic importance, Nshimbodon provides evidence of correlated transformations in the feeding system, neck, and shoulder, which are consistent with novel mammal-like locomotor and feeding mechanics in the earliest cynodonts. Lastly, given previous reports of charassognathids in the Karoo Basin of South Africa, the occurrence of Nshimbodon indicates that charassognathids, like the basal cynodont Procynosuchus, were geographically widespread in southern Pangea by Lopingian times. Continued collecting in the Madumabisa Mudstone Formation will lead to a better understanding of the formation's Permian cynodont diversity and biostratigraphy, as well as the biogeographic structure of southern Pangean vertebrate assemblages prior to the Permo-Triassic mass extinction.

Terrestrial faunas of Turonian age are poorly known due to the paucity of the fossil record in North America and globally. The Smoky Hollow Member of the Straight Cliffs Formation, southern Utah, has yielded a rich assemblage of terrestrial vertebrates; among these, we herein recognize the geologically oldest members of Pediomyoidea. Two new species, Scalaria martini, gen. et sp. nov. and Scalaria aquilana, gen. et sp. nov., are recovered as members of Aquiladelphidae, sharing upper molar characters such as a subdivided B cusp, round and inflated cusps, and an anteroposteriorly expanded protocone. A fragmentary specimen is recognized as an indeterminate pediomyid with morphological similarities to Leptalestes. The occurrence of these distinctive groups in the Turonian prompted a reevaluation of possible antecedents from earlier faunas, and a review of specimens referred to Aquiladelphidae. A phylogenetic analysis suggests that the Cenomanian tribosphenidan Dakotadens may belong within Aquiladelphidae. Of specimens referred to Aquiladelphidae, we recognize Aquiladelphis laurae as a valid species within the genus, and describe a new species of Aquiladelphis from the Judith River Formation of Montana, Aquiladelphis analetris, sp. nov. Two specimens from the ‘Edmontonian’ Williams Fork Formation, previously identified as Aquiladelphis, are here referred to a new species of Glasbius, G. piceanus, sp. nov. The presence of dentally derived marsupialiforms in the Turonian suggests that ecological drivers credited with dietary specializations among later Cretaceous taxa, such as proliferation of angiosperms and pollinating insects, were at work earlier than previously thought.

Desmaninae (water-moles) are common elements in the late Miocene–Pleistocene mammal assemblages from Europe, but knowledge about this group is still scarce. Here we present the desmanines from several early Pliocene localities of the Granada Basin, southern Spain. The species Desmana marci, sp. nov. is described from the sites Calicasas-3 and 4A, characterized, among other traits, by its slightly molarized p4, enormous P2, strongly molarized P3 and P4, and very large metaconule in the M3. Desmana marci shows a typical Desmana i1, with the enamel extending further down anteriorly than posteriorly, but an Archaeodesmana-like I1, low-crowned and bilobed. Desmana marci is proposed as the oldest species of Desmana; its origin lies in Archaeodesmana baetica, and it is in turn interpreted as the ancestor of Desmana verestchagini. Besides, a desmanine of small size and ascribed to Archaeodesmana cf. getica is identified in Calicasas-5A and Purcal-13. This desmanine forms part of a lineage leading to Archaeodesmana elvirae and Archaeodesmana brailloni; this lineage is characterized by an increase in size and in the molarization of the upper premolars. Desmaninae are identified in all the latest Miocene and earliest Pliocene localities from the Granada Basin, evidencing the existence of permanent water bodies. On the contrary, they are not found in sites of similar age in the Guadix Basin, which would have had more arid conditions. The coincident appearance of A. cf. getica in both basins during the early Ruscinian indicates a change towards more humid conditions in the region, allowing the establishment of permanent water flows in the Guadix Basin.

The Paleogene–Neogene boundary is an important transitional time for the evolution of African fauna. Many taxa that evolved endemically in the Paleogene begin to wane in diversity, while new taxa, many of which will become exemplars of the modern African fauna, immigrate from Eurasia via newly opened terrestrial connections. The Paleogene–Neogene boundary is documented in the fossil record at Nakwai, in northern Kenya. Here we describe the mammalian carnivore fauna, which includes the earliest carnivoran records in Africa, and an interesting mix of Paleogene and Neogene hyaenodont taxa. The carnivoran fauna includes Jinomrefu lakwanza, gen. et sp. nov., the earliest barbourofelid in Africa, which has a transitional sabertooth morphology. An analysis of ecomorphological change in African mammalian carnivores across this boundary shows that hyaenodonts become more disparate in body size and more hypercarnivorous as they are displaced by invading carnivorans. This provides another test case for possible competition between carnivorans and hyaenodonts, a group that goes extinct in Africa and globally during the Neogene.

The oldest record of a carnivoran mammal in South America corresponds to the extinct procyonid Cyonasua (late Miocene–early Pleistocene). Up to now, this genus was recorded in Argentina, Uruguay, Bolivia, and Venezuela. In this contribution, we report the first occurrence of Cyonasua in the Pacific coast of Peru, recovered from the late Miocene marine deposits of the Pisco Formation. The fossil material comprises postcranial bones of two individuals (MNHN SAS 1625: left femur; MNHN PPI 262: axis, right talus, and left metatarsal III). The morphology and sizes of these new fossil specimens, allow us to refer them to Cyonasua sp. This record reaffirms that procyonids were the first North American carnivorans that arrived in South America prior to the full emergence of the Isthmus of Panama, as part of the proto-Great American Biotic Interchange. The presence of Cyonasua in marine deposits of the Pacific margin of Peru is further evidence for its affinity to coastal areas and water bodies, and provide clues to propose the arid coast of western South America as a route for dispersal to the southern lands.

Twelve new specimens of fossil walruses are described from four Miocene units in California. The new material represents five taxa: (1) a specimen from the Santa Margarita Formation referred to Imagotaria downsi; (2) a specimen from the Valmonte Diatomite Member of the Monterey Formation referred to cf. Pontolis magnus; (3) six specimens from the Monterey Formation referred to a new species of Pontolis (Pontolis barroni, sp. nov.); (4) one specimen from the Oso Member of the Capistrano Formation referred to a new species of Pontolis (Pontolis kohnoi, sp. nov.); (5) three specimens from the Oso Member referred to a new genus and species (Osodobenus eodon, gen. et sp. nov.). A phylogenetic analysis suggests that both the Dusignathinae and an expanded concept of the genus Pontolis represent monophyletic groups. We provide phylogenetic definitions for clade names of odobenids. Two of the new species are represented by specimens of males, females, and juveniles. Analysis of these specimens shows that the dental anatomy of later diverging basal odobenids is more variable than previously considered. The specific pattern of variation is lineage specific and likely corresponds to the intermediate dental morphology of late Miocene odobenids. Osodobenus eodon, gen. et sp. nov., is the first basal odobenid with tusk-like canines, a longitudinally arched palate, and an enlarged infraorbital foramen. These features are plausibly correlated with benthic suction feeding in the odobenins (Pliocene to Recent) and so Os. eodon may represent a case of convergent evolution of benthic feeding in the late Miocene.

During the land-to-water transition in the Eocene epoch, the cetacean skeleton underwent modifications to accommodate life in the seas. These changes are well-documented in the fossil record. The forelimb transformed from a weight-bearing limb with mobile joints to a flipper with an immobile carpus. We used micro-CT imaging to assess evolutionary changes in carpal size, orientation, and articulation within Eocene cetacean taxa associated with the transition from a terrestrial to amphibious niche. We compared Ambulocetus natans, a well-preserved amphibious archaeocete, with other archaeocetes, and with Eocene terrestrial artiodactyls, the sister group to Cetacea. A cylindrical carpus in terrestrial taxa evolved into a mediolaterally flattened, cambered carpus in the semi-aquatic and fully aquatic cetaceans. Specifically, the pisiform bone shifted from a ventral orientation in terrestrial taxa to a lateral orientation, in plane with the carpus, within semi-aquatic and fully aquatic taxa. Flattening of the carpus, including lateral rotation of the pisiform, likely relates to functional shifts from weight-bearing terrestrial locomotion to aquatic locomotion. This laterally projecting pisiform morphology is retained in all extant cetaceans. Our results suggest this shift, along with other modifications to the carpus, predominantly occurred during the middle Eocene and facilitated an obligatorily aquatic lifestyle in late Eocene cetaceans.

The two extant genera of strictly freshwater dolphins Inia and Platanista are the result of convergent evolution to freshwater environments with reduced visibility. Characterized by their long snout and small melon, these extant taxa are clustered into two clades, Iniidae in South America and Platanistidae in Southern Asia. Their evolutionary history leading to freshwater environments remains mostly unknown, because many of their related fossil species have been found in marine environments. Here, we report riverine dolphin remains (two rostral fragments and a periotic) from two stratigraphic levels of the late middle Miocene (ca. 12.5 Ma) from La Venta, Colombia. The periotic has a reduced cochlear aqueduct mediodorsally oriented, the anterior process is relatively thin, and the dorsal opening of the facial canal is located lateral to the spiral cribriform tract. The rostral fragments are dorsoventrally flattened; the mandible features two longitudinal ventral grooves, and the premaxilla-maxilla suture of the rostrum is located in a deep lateral groove. These characteristics indicate that the specimens belong to Platanistidae, the lineage of the Ganges river dolphin Platanista. Platanistids had also been recorded on coeval strata from the Fitzcarrald arch, Peru. The occurrence of middle Miocene platanistids in both the La Venta and Fiztcarrald localities suggests that members of this lineage moved into freshwater environments in South America earlier than the ancestors of the modern Amazon river dolphin Inia. The subsequent collapse of the Pebas ecosystem could have played a role in the extinction of non-marine Platanistoidea in South America.

We report on the Late Pleistocene (36–12 ka) mammals from Kibogo in the Nyanza Rift of western Kenya, providing (1) a systematic description of the mammal remains, (2) an assessment of their paleoenvironmental implications, and (3) an analysis of the biogeographic implications of non-analog species associations. Kibogo has yielded one of the largest paleontological assemblages from the Late Pleistocene of eastern Africa, and it is dominated by grassland ungulates (e.g., equids and alcelaphin antelopes), including an assortment of extralimital (e.g., Equus grevyi, Ceratotherium simum, Redunca arundinum) and extinct species (Syncerus antiquus, Damaliscus hypsodon, Megalotragus sp.). The composition of the fauna, in conjunction with the soils and topography of the region, indicate the local presence of edaphic grassland situated within a broader environment that was substantially grassier and likely drier than at present. In contrast to nonanalog faunas from higher latitudes (e.g., North America and western Eurasia), the climatic niches of non-analog species associations strongly overlap, indicating that non-analog climate regimes during the Late Pleistocene of eastern Africa are not necessary to account for the former association of presently allopatric species. The Kibogo faunas add to a growing body of evidence implying that the composition of present-day African herbivore communities is distinct from those of the geologically recent past.

We define 17 African land mammal ages, or AFLMAs, covering the Cenozoic record of the Afro-arabian continent, the planet's second largest land mass. While fossiliferous deposits are absent on the eroded plateau of the continent's interior, almost 800 fossil genera from over 350 locations have now been identified in coastal deposits, karst caves, and in the Neogene rift valleys. Given a well-developed geochronologic framework, together with continuing revision to the fossil record—both stimulated by the story of human evolution in Africa—and also to compensate for the variation in fossil ecosystems across such great distances, the AFLMAs are biochronological units defined by type localities, and not biozones to be recognized by the occurrence of certain genera. Disparities are notable: Africa is the highest of all continents, but almost every Paleogene locality was formed at sea level; the fossil record of its great rainforest ecosystem remains virtually unknown; and the Paleogene fauna is relatively isolated, whereas the Neogene begins with open exchange with Laurasia following the Tauride collision, with a simultaneous opening of the East African rift valleys in which the newly revolutionized fauna is abundantly preserved. Notably, the continent-wide and comprehensive documentation of the African mammalian record reveals an unparalleled rate of transformation in the hominin lineage, unmatched by any other group, in response to the Neogene expansion of the open-country ecosystem.