Three skeletons collected from the late Oligocene Kokoamu Greensand of New Zealand are among the most complete Paleogene penguins known. These specimens, described here as Kairuku waitaki, gen. et sp. nov., and Kairuku grebneffi, sp. nov., reveal new details of key elements of the stem penguin skeleton associated with underwater flight, including the sternum, flipper, and pygostyle. Relative proportions of the trunk, flippers, and hind limbs can now be determined from a single individual for the first time, offering insight into the body plan of stem penguins and improved constraints on size estimates for ‘giant’ taxa. Kairuku is characterized by an elongate, narrow sternum, a short and flared coracoid, an elongate narrow flipper, and a robust hind limb. The pygostyle of Kairuku lacks the derived triangular cross-section seen in extant penguins, suggesting that the rectrices attached in a more typical avian pattern and the tail may have lacked the propping function utilized by living penguins. New materials described here, along with re-study of previously described specimens, resolve several long-standing phylogenetic, biogeographic, and taxonomic issues stemming from the inadequate comparative material of several of the first-named fossil penguin species. An array of partial associated skeletons from the Eocene—Oligocene of New Zealand historically referred to Palaeeudyptes antarcticus or Palaeeudyptes sp. are recognized as at least five distinct species: Palaeeudyptes antarcticus, Palaeeudyptes marplesi, Kairuku waitaki, Kairuku grebneffi, and an unnamed Burnside Formation species.

This study identifies three new neoselachian tooth taxa from the Middle and Upper Triassic. On the basis of morphological and histological characters, Rhomaleodus budurovi, nov. gen. et sp. (Anisian of Bulgaria), is resolved as stem selachimorph, with an additional specimen from the same stratigraphic level assigned to Synechodus sp. Selachimorph grade of enameloid microstructural organization (crystalline bundles) was also identified during examination of the dental tissues of “Polyacrodus” holwellensis (Rhaetian of England), necessitating its transfer to the new genus Duffinselache. The present data reveal several levels of increasing architectural complexity in the arrangement of the enameloid crystalline bundles of stem selachimorphs, which are argued to convey a phylogenetic signal that can be used to establish relationships within the group. It is suggested that the evolution of the hypermineralized enameloid cover of neoselachian teeth progressed from a plesiomorphic single crystalline state, through amalgamation of individual crystals into loosely defined bundles (marking the appearance of Selachimorpha), and their subsequent differentiation into a highly ordered parallel bundles, followed by the development of an inner layer of haphazardly oriented bundles. The superficial shiny-layered enameloid of Neoselachii is interpreted as remnant of a much reduced single crystalline layer.

New material of the “porolepidid” Heimenia ensis (Porolepiformes, Dipnomorpha, Sarcopterygii), sheds light on the evolution of scale morphology in sarcopterygian fishes. This material consists of an articulated, nearly complete body and numerous isolated scales from the Emsian-Eifelian (upper Lower Devonian) of Spitsbergen. Heimenia squamation can be described as ‘transitional’ between that of Porolepis and the more derived Holoptychiidae. The cosmoid scales of Heimenia are divided into three morphotypes: (1) rhombic, (2) intermediate, and (3) rounded. The rounded scales are present in the anterior third of the trunk, intermediate scales occupy its middle third, and rhombic scales extend in the rear and all over the ventral region. The transition between scale morphotypes is progressive along the body. All scales bear traces of a cosmine covering, regardless of their overall shape. Paleohistological study shows that the relative thickness of the cosmine layer decreases whereas the relative thickness of the bony basal layer increases from the rhombic to rounded scales. This unique squamation provides new information about the evolutionary transition from thick/rhombic scales covered with cosmine to thin/rounded scales lacking cosmine in the Porolepiformes. Such morphological and histological changes also occurred by convergence among different groups of Middle—Late Devonian sarcopterygians (e.g., lungfishes and “osteolepiforms”). In Heimenia, the presence of rounded scales in the anterior part of the body is here regarded as an adaptation to a dynamic and agile life style and constitutes a new example to support the hypothesis of the anteroposterior spread of derived characters in fishes.

New material of the dipnoan genus Sagenodus is described from the Carboniferous Lagerstätte of Montceau-les-Mines, Massif Central, France. This is the first occurrence of this lungfish in France, thus enlarging its worldwide distribution; and the first occurrence of a lungfish in Montceau-les-Mines, thus increasing the vertebrate taxa list of this Lagerstätte. This material is Stephanian B in age, the previously established geological range of this Euramerican genus. Remains consist of skull, lower jaw, operculum, and shoulder girdle elements closely set together with several ribs. This material, here considered as belonging to a single disarticulated specimen, shows strong affinities with the material of Sagenodus sp. from Germany and appears significantly different from all other known species of Sagenodus by the shape and ridge pattern of the upper tooth plate. However, this new material can only be attributed to Sagenodus sp. due to its incompleteness. In the literature, Montceau-les-Mines is either interpreted as a freshwater environment or as a coastal marine to marine-influenced environment. As Sagenodus is a euryhaline genus; its presence in this locality does not bring arguments to one or the other assumption. The strong affinities, existing between the material from France and Germany, indicate that there were solid hydrographic links between both basins during the Stephanian B—Upper Rotliegend period.

A new locality sampling Oligocene marine deposits of the Tethys is located in Eastern Anatolia, Turkey. Among the vertebrate remains recovered from the site are two specimens representing previously undescribed fishes. Each specimen represents a different taxon, but only one is preserved well enough to describe. We here describe that fish as a new genus and species of elopiform, Echinelops ozcani. The Elopiformes are basal teleost fishes that first appear in the fossil record in the Jurassic. The living diversity of the order is much reduced, with few genera reported from the Cenozoic. Whereas many of the elopiforms are large fishes, the Anatolian specimen is fairly small. Although there is a report of an elopid in the Paratethys region during the Oligocene, the new genus and species of elopiform reported here is the first record of this order in the Tethys Sea during this time.

Pipids are odd-looking frogs with a derived morphology that has been considered to be the result of a successful adaptation to a fully aquatic lifestyle. This monophyletic group comprises 33 extant species arranged in three clades mainly distributed in tropical regions of northern South America (Pipa) and sub-Saharan Africa (Xenopodinae and Hymenochirini). Their fossil record, however, documents greater diversity and wider distribution in South America in the Cretaceous and Paleogene. Recently, isolated postcranial bones bearing distinctive pipid features have been collected from Pleistocene beds in Argentina, nearly 2000 km farther south than their present distribution on the continent. Here, we describe a well-preserved pipid ilium possessing features unknown in the living taxa. The fossil is from a new Lujanian (late Pleistocene) locality of the Pampean Region, thereby confirming the intriguing presence of this group in southern South America. We provide a detailed anatomical evaluation of the adult iliac morphology of pipimorphs and use these data, along with molecular data, in a parsimony analysis of living and extinct pipoid taxa to estimate the relationships of the new material. This analysis places the fossil as a stem xenopodine in an unresolved polytomy together with “Xenopus” romeri from the upper Paleocene—lower Eocene of Brazil and two taxa from the Eocene of Patagonia. These Pleistocene pipid records in the Pampean region and subsequent disappearance may reflect latitudinal shifts owing to the rapid climate changes related to the glacial/interglacial cycles.

Evolutionary changes in lifestyle (e.g., terrestrial vs. aquatic habits) influence tetrapod limb morphology. Similar evolutionary trends in osteogenetic sequences (order of bone ossification) and bone microstructure are often shared in extant tetrapods with similar habit preferences: such data are sometimes available from extinct taxa. The pachypleurosaurids from Monte San Giorgio (Switzerland, Italy) are Triassic marine reptiles with high quality, complete ontogenetic series. We studied osteogenesis and bone histology in the four species from this locality, comparing these with data from Recent terrestrial lizards and secondarily aquatic reptiles in order to determine if the osteogenetic sequences of pachypleurosaurids were similar to either the hypothesized plesiomorphic condition for terrestrial eureptilians or those of Recent aquatic reptiles. Pachypleurosaurian limb osteogenesis occurs in two steps: (1) developmental sequences of ossification during embryology and/or in early neonates, (2a) additional primary periosteal compaction processes, and (2b) additional primary and secondary endosteal compaction processes during neonate ontogeny. Taphonomic patterns reveal information on the order of the initiation and termination of these steps, which are (A) onset of ossification, (B) onset of additional compaction processes (early phase), and (C) termination of additional compaction processes (final phase). An event pairing analysis found that ossification of forelimb elements in pachypleurosaurids precedes that of the hind limb elements in all osteogenetic stages except for initiation of ossification (A). The order of their early phase compaction processes is similar to the hypothesized plesiomorphic eureptilian condition, whereas their final phase compaction processes varies among pachypleurosaurids, with S. mirigiolensis showing minor heterochronic shifts and N. edwardsii showing many heterochronic shifts relative to the hypothesized ancestral condition. Pachypleurosaurids from Monte San Giorgio increase the number of heterochronic shifts with decreasing stratigraphic age, showing a transition from more ‘terrestrial’ to more ‘aquatic’ osteogenetic sequences in comparison to data on ossification sequences of Recent aquatic reptiles.

We describe postcranial remains of new specimens referred to Sebecus icaeorhinus found in the lower section of the Sarmiento Formation at Cañadón Hondo (central Patagonia, Argentina), commonly regarded as part of the Casamayoran South American Land Mammal Age (middle Eocene). The new specimens include a partially articulated postcranium associated with teeth and fragmentary remains of the mandible that allows their identification as S. icaeorhinus. This taxon was almost exclusively known from skull remains from the same stratigraphic unit and was characterized by unique cranial features such as a long, high, and narrow rostrum bearing serrated teeth. The new material reveals numerous details on the postcranial anatomy of this crocodyliform, including the presence of proportionately long limbs and 10 autapomorphies in the vertebrae, forelimb, and pelvic girdle (some of which are interpreted as adaptations to terrestriality and an erect limb posture). These features depict a highly modified postcranial anatomy for S. icaeorhinus in comparison with that of neosuchian crocodyliforms, paralleling the uniqueness of its skull anatomy. The new information is also phylogenetically informative and incorporated into a cladistic analysis that corroborates not only the close affinities of Sebecidae with Baurusuchidae (sebecosuchian monophyly), but also the deeply nested position of this clade within Notosuchia. The incorporation of postcranial characters to the phylogenetic analysis also results in a novel arrangement of the basal mesoeucrocodylians recorded in the Cretaceous—Cenozoic of Gondwana, clustering all of these species into a large monophyletic clade.

Here we present the bone histology of Gasparinisaura cincosaltensis, a basal ornithopod from the Late Cretaceous of Patagonia, and discuss its biological implications. The sample includes axial and appendicular elements from several specimens of different ontogenetic stages. The cortex of most bones consists of fibro-lamellar tissue, with mainly longitudinally oriented vascular spaces, which suggests rapid osteogenesis and fast growth. However, the fibro-lamellar bone is commonly interrupted by lines of arrested growth and/or annuli composed of parallel-fibered bone that indicates that the rapid growth was periodic. Although a true outer circumferential layer was not recorded in any of the sampled elements, in several of the larger samples the woven-fibered matrix of the inner and middle cortex grades into a parallel-fibered tissue, which suggests that the attainment of sexual maturity occurred before skeletal maturity. The growth dynamics of Gasparinisaura are similar to those reported in other basal ornithopods. Inter-elemental, as well as intraspecific, variations in histology were observed in Gasparinisaura. Such variation could be the result of sexual dimorphism, or the effect of localized conditions of growth, or perhaps plasticity in growth in response to local environmental conditions.

Rhoetosaurus brownei is the only known named pre-Cretaceous sauropod from Australia. It is therefore a potentially important taxon for understanding global paleobiogeographic and phylogenetic patterns among early sauropods. Despite its obvious significance, Rhoetosaurus has been too poorly understood to be included in most recent analyses of early sauropod evolution. With this in mind, we evaluated the osteology and phylogeny of undescribed materials of Rhoetosaurus, in order to attempt to close the gap in this understanding. The lower hind limb of Rhoetosaurus highlights a plethora of differences from other sauropods, supporting the distinctiveness of Rhoetosaurus even in the absence of other materials. Some unique traits include prominent crests and sulci on the tibia medially, a narrow metatarsal articular bridge, and pedal claws with an accessory groove or fossa. The pes plesiomorphically retains four claws where most sauropods have three, and bears superficial similarity to that of Shunosaurus. Preliminary cladistic analysis confirms that Rhoetosaurus is a non-neosauropod gravisaurian, although weak support for the most parsimonious topology suggests further findings are required to improve upon incompleteness in the character data. Examination of alternative phylogenetic hypotheses rules out a close relationship between Rhoetosaurus and East Asian Jurassic sauropods, and indicates a closer examination of the potential relationships between Rhoetosaurus and other contemporaneous Middle Jurassic Gondwanan sauropods is necessary.

Deposits from the Fossil Butte Member of the Green River Formation preserve exceptional fossils from one of the most diverse Paleogene avifaunas worldwide. Stem lineage parrots are well represented in this avifauna. Here we report a new species of Pan-Psittaciformes (crown clade parrots and their stem lineage relatives). The new species shares several features with extant parrots that are not present in the contemporaneous clades Halcyornithidae and Messelasturidae, including a wider pelvis, deeper trochlea cartilaginis tibialis, and larger pygostyle. Morphology of the foot suggests strong grasping ability and an arboreal ecology. Phylogenetic analysis of a combined data set of morphological and molecular sequence data resulted in limited support for a sister-group relationship between the new taxon and Quercypsittidae as well as a previously unrecognized clade including Vastanavidae, Halcyornithidae, and Messelasturidae. Regardless of whether this phylogeny or alternate hypotheses are preferred, a complex history of character evolution is inferred for key features related to the zygodactyl grasping foot within Pan-Psittaciformes.

A new species of Pseudoloris (Primates, Microchoerinae, Omomyidae) is described from the middle Eocene (Robiacian) locality of Mazaterón (Almazán Basin, Spain). Pseudoloris cuestai is characterized by its medium size, high and thick paracristid and absence of a distinct paraconid in the lower molars, large hypoconulid in the m3, well-developed protocone in the P3 and P4, reduced hypocone and presence of a weak postprotocingulum in the M1–2, and especially by the lower incisor, with a buccolingually enlarged crown and a very wide, anteroposteriorly compressed root. The material from Mazaterón constitutes the only record of the subfamily Microchoerinae in the Western Iberian Bioprovince, and is clearly different from the species of Pseudoloris that appear in the middle and late Eocene in the Pyrenean basins (P. isabenae from Capella, P. parvulus from Sossís, and the recently described P. pyrenaicus from Sant Jaume de Frontanyà). This discovery reinforces the endemic nature of the mammal faunas from this bioprovince, already observed in other groups such as Perissodactyla, Artiodactyla, Rodentia, and also evidenced in adapoid primates, with the recent description of the genus Mazateronodon.

The White River Formation at Flagstaff Rim in central Wyoming is a key sequence for understanding the biochronology and chronostratigraphy of the Chadronian North American Land Mammal Age. The lower part of this section represents early Chadronian time, an interval whose fauna has not been well known. From these early Chadronian levels 15 species of rodents are discussed and/or described. Of these, three are new species, all belonging to the Eomyidae: Namatomys erythrus, Metanoiamys paradoxus, Cristadjidaumo skinneri. These rodent assemblages add substantially to our knowledge of early Chadronian faunas, and show successional changes in the rodent taxa from the earliest Chadronian through middle Chadronian.

Asymmetry of the knee (distal femur), where the medial trochlear ridge is larger than the lateral one, has been observed in certain ungulates, but until now there has not been a comprehensive study of this anatomy across a range of extant and extinct mammals. A degree of knee asymmetry is present in most ungulates: this asymmetry increases in extent with increasing body size, and is also more prominent in taxa with a preference for open habitats, independent of body size. However, camelids and proboscideans have symmetrical knees, regardless of size. We propose that the correlation of degree asymmetry with habitat type, as can be observed in extant ruminants, is related to the preferred type of locomotion, with the gallop gait being preferred in open habitats. Neither camelids nor proboscideans employ the gallop as a habitual gait. The allometric increase observed in knee asymmetry, in combination with the correlation with locomotor preference, likely reflects anatomy that resists muscular forces pulling the patella medially when the animal is supporting its weight on a single hind leg during fast locomotion. Inclusion of fossil taxa leads to interesting interpretations about the behavior of extinct ungulates: extinct brachydont equids of presumed closed habitat preference have less asymmetric knees than extant equids, or extinct hypsdont equids of presumed open habitat preference; the knee anatomy of giant deer, Megaloceros, indicates a preference for open habitats, whereas the knee anatomy of the brontothere Megacerops indicates a proboscidean (versus rhino-like) type of fast locomotion.

New rhinocerotid remains from the early middle Miocene site of Príncipe Pío-2, Madrid Basin (Madrid, Spain), are described and identified as belonging to Hispanotherium matritense. They constitute the first complete cranial remains recorded for this species, permitting the description of its cranial morphology and updating the species diagnosis. New remains show H. matritense as a middle-sized hornless elasmotheriine rhinoceros, contrary to previous studies. Phylogenetic analysis places the Western European Hispanotherium matritense close to the coeval Spanish species Hispanotherium corcolense and more distantly related to the French species Hispanotherium beonense. The late middle Miocene “H.” tungurense from Inner Mongolia is placed near later diverging elasmotheres, and its belonging to the genus Hispanotherium is questioned.

Early Miocene floridatraguline camels are characterized by having an elongate snout, shallow and narrow symphysial area, and relatively primitive dentitions. Their fossil record is restricted to subtropical assemblages including the Hemingfordian Thomas Farm Local Fauna (L. F.) in Florida, the Zoyotal L. F. in Mexico, and the Arikareean Castolon L. F. in Texas. Here we describe the first floridatraguline camels from the early Miocene Las Cascadas Formation, Panama Canal area, Central America. We describe two new species that are similar to Aguascalientia wilsoni from the Zoyotal L. F. in having (1) a primitive lower dental formula, (2) brachydont teeth, (3) an unusually elongate jaw with caniniform c1 and p1 that are well separated by a diastema, (4) a long and narrow mandibular symphysis, (5) lower molars with small intercolumnar pillars, (6) an m3 hypoconulid divided by lingual and labial selenes, and (7) no diastema between p2 and p3. Aguascalientia panamaensis, sp. nov., and Aguascalientia minuta, sp. nov., are represented by partial lower dentitions and isolated upper molars. Both new species are distinct from A. wilsoni in having (1) p1 and c1 similar in size, (2) less inflected paraconids on lower premolars, and (3) less reduced premolars. Interpreted primitive characters are similar to a small, unnamed camel from the earliest Miocene Buda L. F. of Florida (middle late Arikareean NALMA). The Las Cascadas fossil assemblage probably constitutes a distinctive Arikareean (Ar3–Ar4) faunal province characterized by the arrival of northern immigrants into a small continental basin connected with North American continental terrains.

Here we describe Bohaskaia monodontoides, a new taxon of beluga-like odontocete cetacean from the early Pliocene Yorktown Formation of Virginia and North Carolina. Among odontocetes, Bohaskaia shares key characteristics of the rostrum and face with belugas (Delphinapterus leucas), narwhals (Monodon monoceros), and Denebola brachycephala from the late Miocene of Baja California, thus placing it as a member of the Monodontidae. It also displays autapomorphies that merit its placement in a new genus and species. Both Denebola and Bohaskaia occurred in warmer latitudes than those of extant monodontids, even accounting for extralimital records. Such data from the fossil record of Monodontidae indicates that putative cold climate adaptations of living monodontids might have appeared under different environmental conditions and that their Holarctic and sub-Arctic distribution is a relatively recent phenomenon.