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The recently discovered mass mortality of fishes from the Tanis Site in the North Dakota portion of the Late Cretaceous Hell Creek Formation contains many well-preserved, three-dimensional skeletons. Among these are representatives of two acipenseriform families, Acipenseridae (sturgeons) and Polyodontidae (paddlefishes). This paper describes two new monotypic polyodontid genera, expanding our knowledge of polyodontid diversity. The first of the new species described here is †Parapsephurus willybemisi n. gen. n. sp. It is distinguished from all other known species by having a combination of posteriorly elongate parietals, the middle fenestra longitudinalis bordered medially by the parietal and frontal and laterally by the dermopterotic, slender and numerous dorsal caudal fulcra, an elongate hyomandibula that is not hourglass shaped, and gill rakers that are short and widely spaced. The second polyodontid species described here is †Pugiopsephurus inundatus n. gen. n. sp. It is diagnosed by a combination of having stellate bones that are exceptionally poorly developed or absent and having a dermopalatine with a medial expansion and lacking an ectopterygoid process. The two species of paddlefishes described in this paper add to the morphological and taxonomic diversity of Polyodontidae. The presence of these taxa within the Hell Creek Formation hints at substantial diversity of polyodontids at this stage of their evolutionary history. UUID: http://zoobank.org/08cbf8c5-59ba-41fa-9265-8cb762cf7b13

Although the Cretaceous is widely regarded as a time of great evolutionary transition for the freshwater fish fauna of North America, the fossil record of this period is notoriously poor, consisting mostly of fragments and isolated skeletal elements. Exceptions include the acipenseriforms, discussed in this paper, and some exceedingly rare teleosts. Here we describe two new species of well-preserved sturgeons (Acipenseridae) from the Tanis site in the Late Cretaceous Hell Creek Formation of North Dakota. The type and referred materials were preserved in a loosely consolidated matrix. †Acipenser praeparatorum n. sp. is represented by multiple body fossils (including the head and relatively complete postcranial remains) and a specimen of an intact, three dimensionally preserved skull and pectoral girdle. This taxon can be diagnosed based on features of the opercular elements (exceptionally tall and narrow branchiostegal). The second species, †Acipenser anisinferos n. sp., is represented by a partially preserved skull, and can be diagnosed by a relatively elongate preorbital region (i.e., snout) and the absence of thorn-like spines on the skull roofing bones. Most known sturgeon fossils from the Cretaceous are represented only by undiagnosable fragmentary remains (i.e., scutes and pectoral-fin spines) or poorly preserved partial skeletons (e.g., †Protoscaphirhynchus), with †Priscosturion and †Anchiacipenser (both monotypic) being rare exceptions. Therefore, the newly discovered Tanis fossils give a rare glimpse into the evolution of Acipenseridae at a critical time in the phylogenetic history of acipenseriforms, and suggest significant morphological and taxonomic diversity early in the evolution of this group.UUID: http://zoobank.org/375b586a-2dd8-4a31-b6c4-42151e6e8fc8

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The family †Peipiaosteidae contains the genera †Peipiaosteus, †Stichopterus, †Spherosteus, †Yanosteus, and †Liaosteus, all from Late Jurassic to Early Cretaceous deposits of China, Russia, Kazakhstan, and Mongolia. Although the family has taxonomically expanded since it was first established for †P. pani Liu and Zhou, 1965, the amount of detailed comparative data for many of the taxa involved is lacking. In this paper, we describe the osteology of the monotypic genus †Yanosteus from the Yixian Formation (Early Cretaceous) of China largely on the basis of a newly prepared, well-preserved specimen. †Yanosteus is characterized by a series of infraorbital ossicles (a characteristic of the family), a broad, rounded palatopterygoid, a robust dentary, an extremely small opercle and a subopercle with distinctly long and rounded anterior process and a posteriorly scalloped margin, a broad and weakly forked caudal fin, an elongate dorsal fin with more than 160–178 fin rays (diagnostic for the genus), and a short but well-formed pectoral fin spine. We use the results of this study to discuss the characters of the †Peipiaosteioidei and the diversity of †peipiaosteioids.

Summary Beak shape plays a key role in avian radiations and is one of the most intensely studied aspects of avian evolution and ecology [ 1 , 2 , 3 , 4 ]. Perhaps no other group is more closely associated with the study of beak shape than Passeriformes (passerines or perching birds), the most species-rich ordinal clade of modern birds. However, despite their extraordinary present-day diversity, our understanding of early passerine evolution has been hindered by their sparse fossil record [ 5 , 6 ]. Here, we describe two new species of early Eocene stem passerines from the Green River Formation of the United States and the Messel Formation of Germany. These species are the oldest fossil birds to exhibit a finch-like beak and provide the earliest evidence for a diet focused on small, hard seeds in crown birds. Given that granivory is a key adaptation that allows passerines to exploit open temperate environments, it is notable that both species occurred in subtropical environments [ 7 , 8 ]. Phylogenetic analyses place both species within the Psittacopedidae, an extinct Eocene clade of zygodactyl stem passeriforms that also includes the slender-beaked nectarivorous Pumiliornis, the short-beaked Psittacopes, and the thrush-beaked Morsoravis. Our results reveal that stem passerines attained a diversity of beak shapes paralleling many of the morphotypes present in extant passerine finches, thrushes, and sunbirds, more than 35 million years before these morphotypes arose in the crown group. Extinction of these ecologically diverse fossil taxa may be linked to more sophisticated nest construction in anisodactyl crown passerines versus cavity-nesting in Eocene zygodactyl stem passerines [ 9 ].

A new subadult partial skeleton of a pantolestid is reported from the late early Eocene Fossil Butte Member of the Green River Formation. Although the specimen displays a full permanent dentition, the presence of unfused elbow epiphyses (typically the first epiphyses to close), together with a short skull, shallow dentaries, and incompletely erupted third molars, indicates that it was a young juvenile. This adds to evidence that pantolestids had relatively early eruption of permanent premolars and late epiphyseal closure. Based on molar size and morphology, including presence of a well-developed paraconid, the specimen is attributed to Palaeosinopa didelphoides. Despite differences in skeletal size and robustness among the three known Fossil Butte pantolestid skeletons, all of which are skeletally subadult, similarity in molar size (and morphology, to the extent that it is visible) suggests that the three skeletons represent three growth stages of P. didelphoides. If this interpretation is correc...

Paleogene sedimentary rocks of the Arkose Ridge Formation (Talkeetna Mountains, Alaska) preserve a record of a fluvial–lacustrine depositional environment and its forested ecosystem in an active basin among the convergent margin tectonic processes that shaped southern Alaska. An ~ 800 m measured succession at Box Canyon indicates braid-plain deposition with predominantly gravelly deposits low in the exposure to sandy and muddy facies associations below an overlying lava flow sequence. U–Pb geochronology on zircons from a tuff and a sandstone within the measured section, as well as an Ar/Ar date from the overlying lava constrain the age of the sedimentary succession to between ~ 59 Ma and 48 Ma. Fossil plant remains occur throughout the Arkose Ridge Formation as poorly-preserved coalified woody debris and fragmentary leaf impressions. At Box Canyon, however, a thin lacustrine depositional lens of rhythmically laminated mudrocks yielded fish fossils and a well-preserved floral assemblage including foliage and reproductive organs representing conifers, sphenopsids, monocots, and dicots. Leaf physiognomic methods to estimate paleoclimate were applied to the dicot leaf collection and indicate warm temperate paleotemperatures (~ 11–15 ± ~ 4 °C MAT) and elevated paleoprecipitation (~ 120 cm/yr MAP) estimates as compared to modern conditions; results that are parallel with previously published estimates from the partly coeval Chickaloon Formation deposited in more distal depositional environments in the same basin. The low abundance of leaf herbivory in the Box Canyon dicot assemblage (~ 9% of leaves damaged) is also similar to the results from assemblages in the meander-plain depositional systems of the Chickaloon. This new suite of data informs models of the tectonostratigraphic evolution of southern Alaska and the developing understanding of terrestrial paleoecology and paleoclimate at high latitudes during the Late Paleocene–Early Eocene greenhouse climate phase.

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Five anurans have been previously reported from the Eocene Green River Formation, of which only two, a nearly complete skeleton and a tadpole,have been described. The skeleton has been identified as either Eopelobates Parker, 1929, or a pelobatid close to Eopelobates and PelobatesWagler, 1830, but the tadpole is indeterminate. Another specimen has been figured but not described, another is a skin impression that is probablyindeterminate, and the other is presumably lost. A sixth specimen is reported here. It represents a new genus and species,Aerugoamnis paulus,which is the first anuran to be reported from the Wasatchian (early Eocene) Fossil Butte Member of the Green River Formation. It consists of asingle specimen that is dorsoventrally flattened and exposed primarily in dorsal view on one slab of rock, with a poor impression of the skull anda few bone fragments representing the counterpart. The specimen is nearly complete and the bones are preserved in articulation or in close association.The presence of a spiral groove of the iliac shaft suggests affinity with Anomocoela, a hypothesis that was tested through a phylogeneticanalysis including representatives of the major clades of Costata, Xenoanura, Neobatrachia, and Anomocoela. The analyzed data set consists of 66osteological characters scored for six fossil and 20 extant taxa. Results of the analysis place Aerugoamnis as a member of the stem of Pelodytidae.This placement is based on possession of two synapomorphies: presence of a distinct otic ramus of the squamosal and the crista parotica is poorlydeveloped. Unlike extant pelodytids, Aerugoamnis has nasals that are separated by a narrow gap, a ventral flange on the pterygoid, and unfusedtibiale and fibulare. Prior to the discovery of Aerugoamnis, fragmentary remains from the middle Eocene of Europe, the earliest of which areLutetian (MP 13), have been questionably referred to the family. Aerugoamnis now is the earliest known occurrence of the anomocoelan lineagerepresented today by Pelodytidae. Fil: Henrici, Amy C.. Carnegie Museum of Natural History; Estados Unidos de América; Fil: Baez, Ana Maria. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Geologia. Cat.de Paleontologia; Argentina; Fil: Grande, Lance. The Field Museum; Estados Unidos de América

A new species of the genus Amia of the family Amiidae, A. godai is described based on a parasphenoid and many isolated bones and scales found from the Early Miocene Nakamura Formation of the Mizunami Group along the Kiso River in Kani City, Gifu Prefecture, Central Japan. Amia godai sp. nov. is distinguished by having a V-shaped edentulous area in the posterior part of the tooth patch of the parasphenoid. This is the first record of the genus from the Early Miocene in the world and the first record of the family from the Cenozoic in Japan.

Recent commentary by Costello and collaborators on the current state of the global taxonomic enterprise attempts to demonstrate that taxonomy is not in decline as feared by taxonomists, but rather is increasing by virtue of the rate at which new species are formally named. Having supported their views with data that clearly indicate as much, Costello et al. make recommendations to increase the rate of new species descriptions even more. However, their views appear to rely on the perception of species as static and numerically if not historically equivalent entities whose value lie in their roles as "metrics". As such, their one-dimensional portrayal of the discipline, as concerned solely with the creation of new species names, fails to take into account both the conceptual and epistemological foundations of systematics. We refute the end-user view that taxonomy is on the rise simply because more new species are being described compared with earlier decades, and that, by implication, taxonomic practice is a formality whose pace can be streamlined without considerable resources, intellectual or otherwise. Rather, we defend the opposite viewpoint that professional taxonomy is in decline relative to the immediacy of the extinction crisis, and that this decline threatens not just the empirical science of phylogenetic systematics, but also the foundations of comparative biology on which other fields rely. The allocation of space in top-ranked journals to propagate views such as those of Costello et al. lends superficial credence to the unsupportive mindset of many of those in charge of the institutional fate of taxonomy. We emphasize that taxonomy and the description of new species are dependent upon, and only make sense in light of, empirically based classifications that reflect evolutionary history; homology assessments are at the centre of these endeavours, such that the biological sciences cannot afford to have professional taxonomists sacrifice the comparative and historical depth of their hypotheses in order to accelerate new species descriptions. Fil: de Carvalho, María Rosa. Universidade de Sao Paulo; Brasil Fil: Ebach, Malte C.. University of New South Wales; Australia Fil: Williams, David M.. Natural History Museum; Reino Unido Fil: Nihei, Silvio S.. Universidade de Sao Paulo; Brasil Fil: Rodrigues, Miguel Trefaut. Universidade de Sao Paulo; Brasil Fil: Grant, Taran. Universidade de Sao Paulo; Brasil Fil: Silveira, Luís F.. Universidade de Sao Paulo; Brasil Fil: Zaher, Hussam. Universidade de Sao Paulo; Brasil Fil: Gill, Anthony C.. University of Sydney; Australia Fil: Schelly, Robert C.. American Museum of Natural History; Estados Unidos Fil: Sparks, John S.. American Museum of Natural History; Estados Unidos Fil: Bockmann, Flávio. Universidade de Sao Paulo; Brasil Fil: Séret, Bernard. Muséum National d'Histoire Naturelle; Francia Fil: Ho, Hsuan-Ching. National Museum of Marine Biology and Aquarium; China Fil: Grande, Lance. Field Museum Of Natural History; Estados Unidos Fil: Rieppel, Olivier. Field Museum Of Natural History; Estados Unidos Fil: Dubois, Alain. Muséum National d'Histoire Naturelle; Francia Fil: Ohler, Annemarie. Muséum National d'Histoire Naturelle; Francia Fil: Faivovich, Julián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Assis, Leandro C.S.. Universidade Federal de Minas Gerais; Brasil Fil: Wheeler, Quentin D.. Arizona State University; Estados Unidos Fil: Goldstein, Paul Z.. University of Maryland; Estados Unidos Fil: De Almeida, Eduardo A.B.. Universidade de Sao Paulo; Brasil Fil: Valdecasa, A.G.. Museo Nacional de Ciencias Naturales; España Fil: Nelson, Gareth. University of Melbourne; Australia

A new avian species from the late early Eocene Fossil Butte Member of the Green River Formation is described based on a nearly complete postcranial skeleton. The new species, Vadaravis brownae, gen. et sp. nov., can be diagnosed by a unique combination of characters, including the following autapomorphies, which are unique among Aves: two (cranial and caudal) small and discrete pneumatopores on the lateral sides of the caudal-most thoracic centra; and a caudoventrally located pisiform process of the carpometacarpus that projects only weakly cranially. Phylogenetic analyses recover Vadaravis as a member of the waterbird assemblage (including, e.g., penguins, storks, pelicans), closely related to taxa traditionally placed within the avian order Ciconiiformes (storks, flamingos, herons, the hamerkop, ibises, and spoonbills). Additional morphological features and a phylogenetic analysis constrained by a recently recovered waterbird topology suggest close affinities between Vadaravis and Threskiornith...

To determine the quality of fossil preservation in the early Eocene Fossil Butte Member (FBM) of the Green River Formation in Fossil Basin, Wyoming, we excavated 1,133 fishes from the upper 30 cm of the 45.7-cm-thick FBM. Each fossil was evaluated for its relative skeletal articulation, ranging from near perfect articulation to almost complete disarticulation, and placed into one of four stages. About 70% of the fishes have near-perfect articulation of the skeleton. Ninety-seven percent of the specimens in the sample belong to five of 19 genera known from the FBM: †Knightia, †Diplomystus, †Cockerellites, †Mioplosus, and †Priscacara. Finally, 97% of the specimens belong to four of 15 families known to be present in the FBM: †Paraclupeidae, Clupeidae, Latidae, and Moronidae.

A new species of stem parrot is reported from the early Eocene Fossil Butte Member of the Green River Formation. Well-preserved specimens including a complete skeleton and referred partial postcranial skeleton reveal new osteological details of the clade Halcyornithidae and expand the known diversity of the Green River avifauna. Cyrilavis colburnorum n. sp. shares key morphologies with the smaller Green River halcyornithid Cyrilavis olsoni. A combined phylogenetic analysis of Pan-Psittaciformes using 101 morphological characters and sequence data from three genes (RAG-1, Z-chromosomal spindlin and cytochrome b) supports the placement of 1) Halcyornithidae, 2) a small clade uniting the Messel fossil taxon Psittacopes lepidus and an unnamed London Clay species, and 3) Quercypsittidae on branches successively closer to the crown clade Psittaciformes. Analysis of the morphological dataset alone yields a similar strict consensus tree with slightly less resolution (one additional branch collapsed). Relationships within the crown clade agree well with recent hypotheses in supporting a basal divergence between the New Zealand Nestoridae and all other extant parrots, and a second major divergence between Cacatuidae and Psittacidae. When fossils are taken into account, many previously proposed synapomorphies of extant parrots are instead optimized as synapomorphies of more inclusive groups including both stem fossil taxa and living taxa. Fossil evidence is consistent with a more recent origin of crown clade Psittaciformes than predicted from divergence dating analyses, and supports environmental shifts and dispersal as key drivers in parrot biogeography.

Sturgeons of the family Acipenseridae comprise 25 extant species, making it the most species-rich extant family of basal (i.e., nonteleostean) actinopterygians. Because of their basal position within Actinopterygii, the anatomical study of sturgeons has a long and rich history, although there remains much to be discovered. Here we describe and illustrate the skeletal anatomy of the shortnose sturgeon, Acipenser brevirostrum, as a representative of the family Acipenseridae. Acipenser brevirostrum, which is distributed along the east coast of North America, is a relatively small species of sturgeon, reaching a maximum of just over 1 m in total length. Our study is based on 105 skeletal and 147 alcohol-stored specimens representing a broad range of ontogenetic stages (ca. 18 to 1000+ mm TL). This study emphasizes the bony portions of the skeleton, their ontogeny, and parts of the skeleton that persist as cartilaginous elements into the adult stage; the earliest stages of development of the chondrocr...

A new species of Amiidae, †Cratoamia gondwanica gen. et sp. nov., is here described from the Early Cretaceous Crato Formation of the Araripe Basin, northeast Brazil. The new species, based on complete and nearly complete articulated specimens, includes synapomorphies of the subfamily †Vidalamiinae and the tribe †Vidalamiini. The presence of †Cratoamia in Brazil increases the geographical distribution of the tribe †Vidalamiini into the Southern Hemisphere.

†Notogoneus osculus Cope, the type species for the geographically widespread Upper Cretaceous to Upper Oligocene genus †Notogoneus (Gonorynchidae), is redescribed in detail based on much new material. This species is known from the Early Eocene Fossil Butte Member of the Green River Formation, southwestern Wyoming. It is geologically the youngest known species of the family Gonorynchidae in North America, although the family is known from Oligocene and Miocene lacustrine deposits of Europe and Australia and is extant today in tropical marine environments of the Pacific (Gonorynchus spp.). In this paper we also correct a number of mistakes in previously published morphological descriptions of †N. osculus (e.g., in skull and caudal skeleton) based on a large, new sample of well-preserved, well-prepared specimens. Accurate description of this species is important because it is the type for the genus and it is also by far the best preserved of all known species of †Notogoneus. In addition, it may she...

Marcelo R. de Carvalho AE Flavio A. Bockmann AE Dalton S. Amorim AE Carlos Roberto F. Brandao AE Mario de Vivo AE Jose L. de Figueiredo AE Heraldo A. Britski AE Mario C. C. de Pinna AE Naercio A. Menezes AE Fernando P. L. Marques AE Nelson Papavero AE Eliana M. Cancello AE Jorge V. Crisci AE John D. McEachran AE Robert C. Schelly AE John G. Lundberg AE Anthony C. Gill AE Ralf Britz AE Quentin D. Wheeler AE Melanie L. J. Stiassny AE Lynne R. Parenti AE Larry M. Page AE Ward C. Wheeler AE Julian Faivovich AE Richard P. Vari AE Lance Grande AE Chris J. Humphries AE Rob DeSalle AE Malte C. Ebach AE Gareth J. Nelson

A pleurodontan iguanian from the Green River Formation (Eocene) is described in detail and named. The new taxon is known only from a single specimen preserving all areas of the body. Although many of the bone surfaces are eroded, almost all of the skeleton is present and some cartilaginous elements are preserved. The new taxon shares important characteristics with the extant anisolepines and leiosaurines, including the morphology and placement of the caudal autotomy planes, the postxiphisternal inscriptional ribs, and notched or fenestrated clavicles that are expanded proximally. This is the earliest complete iguanian known from the Americas and the earliest known iguanian that may be confidently referred to an extant “family.” A phylogenetic analysis including this taxon and other fossil and extant iguanians offers some support for the monophyly of Polychrotidae sensu lato, Tropiduridae sensu lato, and non-acrodont iguanians (Pleurodonta).

The skeleton of a newly discovered, exceptionally preserved specimen of Saniwa ensidens is described in detail. The fossil consists of a complete articulated skeleton exposed in dorsal view. It adds important additional information to our knowledge of the anatomy of this fossil varanoid taxon, including a detailed description of the dermatocranium in dorsal view, complete vertebral counts, and a detailed account of the appendicular skeleton. Cartilage preservation allows the identification of treacheal rings, sternum, inscriptional ribs, epicoracoid and suprascapula. Patches of skin are preserved on dermal skull bones, and scattered scales surround the entire skeleton. Incomplete ossification of carpal and tarsal elements, as well as of epiphyses, indicate that the specimen is not fully mature.

A new species of sturgeon (Acipenseridae), †Psammorhynchus longipinnisn. gen. and sp., is described based on a single well-preserved specimen from the Upper Cretaceous Judith River Formation of Montana. Although based on only a single individual, the osteological detail we are able to describe for this species is extensive because of the completeness of the specimen, the relatively three-dimensional preservation, and the soft, loosely consolidated sandstone matrix in which it was contained (allowing some dissection of the specimen to reveal the internal bones of the head region). We prepared the specimen completely out of the matrix, and described the head region in stages of “dissection.” †Psammorhynchus longipinnisis the only fossil sturgeon to date that provides a relatively complete, reliable look at its osteology. Although there have previously been numerous and widespread reports of fossil sturgeons, the material is notoriously fragmentary and poorly preserved, consisting mostly of isolated scutes or pectoral spines (summarized here in an appendix) and it is of very limited use to phylogenetic studies of living sturgeon taxa. The only other described articulated skeleton of a fossil sturgeon is †Protoscaphirhynchus squamosusWilimovsky from the Upper Cretaceous Hell Creek Formation of Montana. That specimen (the only one known for the species) is a badly preserved, very poorly prepared skeleton showing little detail of the head region. It is interesting to note that the only known articulated fossil sturgeon skeletons (†Psammorhynchus longipinnisn. gen. and sp.; †Protoscaphirhynchus squamosusWilimovsky; and a third, yet undescribed specimen) were apparently each independently discovered in the abdominal regions of hadrosaurian dinosaurs (as was the Cretaceous paddlefish †Paleopsephurus wilsoniMacAlpin). Perhaps hadrosaur carcasses provided the right combination of taphonomic factors to protect acipenseriform carcasses from damage in high energy aquatic environments predominantly preferred by sturgeons. In any case, based on known specimens, sediments within hadrosaurs appear to have been the main preservational medium for articulated fossil sturgeon skeletons in North America.†Psammorhynchus longipinnisappears to be the sister taxon to the rest of Acipenseridae based on our preliminary analysis here. We will reevaluate this relationship elsewhere in our (Hilton, Grande, and Bemis) ongoing study of fossil and living Acipenseridae.

The pre-Pleistocene fossil record of sturgeons (family Acipenseridae) from North America is reviewed based on a survey of reports in the literature and firsthand examination of specimens in museum collections. We provide a redescription of the only known specimen of † Protoscaphirhynchus squamosus(Late Cretaceous, Montana), a very poorly preserved specimen for which few morpho- logical details can be determined. Three taxa described as species of the genus Acipenser from North America († A. albertensis ,† A. eruciferus, and † A. ornatus) were described based on isolated and fragmentary remains, and are here considered to be nomina dubia. The earliest reported remains of North American sturgeons are from the Late Cretaceous (Santonian to Campanian Milk River For- mation). There is a relatively continuous record, with the exception of the Eocene and Oligocene, in which there are few (potentially in the Eocene) or no (Oligocene) known specimens available in collections. We have found that nearly all specimens are best regarded as Acipenseridae indeterminate genus and species due to their fragmentary preservation and lack of preserved diagnostic characters.

We describe methods for preparing dry skeletons of virtually any osteichthyan species with a well-ossified skeleton, including very large specimens (e.g., > 1 m Megalops atlanticus). Our approach differs from those conventionally used to prepare skeletons of tetrapods in that (1) fairly complete dissection of the specimen is required at the outset of processing; and (2) we use an alcohol dehydration step to rapidly dry the specimen. Similar techniques can be used to prepare well-calcified chondrichthyan skeletons. We also outline the steps for making Ridewood dissections of the skull. Dry, partially articulated skeletons prepared by these methods can be stored indefinitely in acid-free containers in an environmentally controlled space (21 C ± 3 C; Rh = 40% ± 5%) in pest-proof specimen cases. Although a truism of anatomical research is that you cannot learn everything from studying one specimen or one type of preparation, partially articulated dry skeletons are useful for research ranging from phy...

Freshwater stingrays from the Fossil Butte Member of the late early Eocene Green River Formation of Wyoming are reviewed, and a new genus and species of fossil stingray is described. †Asterotrygon maloneyi, n.gen., n.sp. is remarkably well preserved and is known from articulated skeletons of juveniles and adults, both males and females. It is distinguished from all Recent and fossil stingrays, including †Heliobatis radians from the same formation, by the unique presence of a dorsal fin covered with dermal denticles directly anterior to the caudal stings. Other characters that in combination distinguish the new fossil genus from all other stingrays include: retention of separate, individual vertebrae extending to the tail extremity instead of a cartilaginous rod posterior to caudal stings; dorsal surface of disc and tail covered by numerous, closely packed, minute denticles; tail relatively stout at base; and relative proportions of disc and tail. †Asterotrygon, n.gen. shares with certain stingray...

†Protopsephurus liui Lu, 1994, from the Lower Cretaceous Yixian Formation of China, is both the oldest and the most primitive paddlefish (polyodontid) known. It was originally described based on a partial skeleton, a partial skull, and two partial trunk regions, leaving much of the species' osteology unknown. Here, based on the type specimens and many newly discovered well-preserved skeletons, we describe this species in detail. †Protopsephurus is clearly a polyodontid based on several characters including: (1) the presence of stellate bones; (2) the presence of a series of long median dorsorostral and ventrorostral bones; (3) extreme elongation of the snout; (4) the presence of anterior, middle and posterior divisions of the fenestra longitudinalis; and (5) the presence of “microctenoid” scales (defined here). Within Polyodontidae, †Protopsephurus (which forms the monotypic series †Protopsephuri) lacks several characters derived for all other Polyodontidae (=Polyodonti). In contrast to †Protopse...

A well-prepared anterior half of an amiid skull from the Late Paleocene Paskapoo Formation of south-central Alberta is described. The specimen is either very closely related to, or conspecific with, Amia pattersoni Grande and Bemis, 1998, from the Early Eocene Green River Formation of Wyoming. We leave the specimen as Amia cf. pattersoni until additional material is found to further clarify its relationships. Amia cf. pattersoni is the oldest known specimen clearly identifiable as belonging to the genus Amia (sensu Grande and Bemis, 1998), and the Paskapoo species extends the known geographic range of Amia both northward and westward. The fish assemblage of the Paskapoo Formation represents the most diverse freshwater Paleocene fish fauna known from North America. Based on comparisons of sample size and relative taxonomic diversity to the better known Green River Formation localities of Wyoming, we predict that further collecting will substantially increase the known diversity of the Paskapoo fauna. The Paskapoo Formation, therefore, has great potential to continue adding to the meager knowledge of pre-Eocene freshwater teleost diversity in North America.

†Notogoneus montanensis, sp. nov. (Teleostei: Ostariophysi: Gonorynchidae) is described from Late Cretaceous freshwater deposits of the Two Medicine Formation of Montana. The species is represented by one articulated skeleton and a partial trunk region of a second individual. Articulated freshwater fish fossils are almost unknown in Early Cretaceous through Middle Paleocene age deposits of North America. Localities such as the Two Medicine fish locality are extremely important to a better understanding of the biodiversity of early North American freshwater teleosts. †Notogoneus montanensis, sp. nov. is the earliest known occurrence of the genus †Notogoneus, and it is the earliest known freshwater gonorynchiform from North America. The distribution of †Notogoneus and other gonorynchid species is briefly reviewed. Additional fragmentary fish fossils found associated with †N. montanensis, sp. nov. include a number of teleost scales, which appear to belong to at least two different taxa other than †N...

A new species of esocid, †Esox (Kenoza) kronneri sp. nov., is described from the early Eocene Fossil Butte Member of the Green River Formation, southwestern Wyoming. This is the first member of the order Esociformes reported from the Green River Formation. It is also the first articulated fossil esocid from North America identified as a pickerel (=subgenus Kenoza). The new species is known by only a single specimen. Consequently, it was probably not a normal resident of Fossil Lake, considering the hundreds of thousands of fishes that have been excavated from this locality over the last 140 years. Although small (118 millimeters long), the specimen is one of the best-preserved fossil esociforms ever reported. The new species appears to be closely related to the extant species †Esox americanus (which includes two extant subspecies, †E. americanus americanus and †E. americanus vermiculatus), but much work is yet needed to adequately resolve the interrelationships of living and well-preserved fossil...

A well-preserved primitive amphiumid skeleton from the Eocene Green River Formation in Wyoming is described as †Paleoamphiuma tetradactylum, gen. et sp. nov. This species differs from extant and known fossil amphiumids by the retention of a number of plesiomorphic features: separate ossification of the first hypobranchial and first ceratobranchial; no more than 35 presacral vertebrae; rib-bearers that are directed posterolaterally, taper to a blunt tip, and lack a posteroventral flange; and the presence of four digits in the manus (and probably in pes). Characterized so far only by the absence of derived characters, this new fossil amphiumid is currently a metaspecies.

A second species of the genus †Hypsidoris is described from the primitive catfish family †Hypsidoridae. The new species is from Eocene freshwater deposits of the Clamo Formation of central Oregon and is known by numerous well-preserved skeletons. Like the type species from the Green River Formation of Wyoming, the Oregon species has a well-developed toothed maxilla, a feature thought to be primitive among catfishes. Among the more than 35 nominal families containing over 2,200 species of catfishes, only Diplomystidae and †Hypsidoridae have well-developed toothed maxillae. The relationships of †Hypsidoridae to other catfishes are briefly reviewed. The associated ichthyofauna is also briefly discussed in context with other Eocene faunas of western North America.

A new species of amiid fish, Calamopleurus africanus sp. nov., is described on the basis of fragmentary material from? Albian Kem Kem beds of southern Morocco. The new species shows several derived characters of the genus Calamopleurus such as ossified dermopterotic ribs, an inferred loose association between the dermosphenotic and the skull roof, a gular plate with a scalloped posterior margin, and a hyomandibular with a very long posterior (opercular) process. It differs from the type species in the proportions of the frontals, supramaxilla and gular. The distribution of Calamopleurus and some other Lower Cretaceous fishes is discussed in the context of the presumed adjacency of west Africa and eastern Brazil during much of the Mesozoic.

The comparative osteology, phylogenetic relationships, and historical biogeography of all known taxa of fossil and living amiid fishes (Halecomorphi: Amiidae) are investigated in detail. Previously, the detailed osteology of nearly all fossil amiids was unknown. We present the first well-supported comprehensive phylogeny for fossil and living amiid fishes. We synthesize clearly documented phylogenetic data on amiids and other halecomorph fishes with other historical phenomena such as ontogeny, historical biogeography, stratigraphic paleontology, and paleoecology (both “stationary” and “historical”). We also use our study of halecomorph fishes as a platform to explore several fundamental methodological and theoretical concepts important to phylogenetic/evolutionary investigations. These concepts pertain mainly to (1) the use of comparative empirical data to interpret various historical patterns and (2) the practice of integrating fossil and living species together in original (i.e., non-literature...

Review of recently collected material ofEohiodonfrom North America suggests that there are two valid species,E. rosei(Hussakof) andE. woodroffiWilson.Eohiodon falcatusGrande is identical toE. woodruffiin known skeletal features and nearly all meristic features and is treated as a junior synonym of the latter. The fossil genusEohiodonCavender differs fromHiodonLesueur, which is known from both fossil and extant species, in numerous meristic and osteological features. The caudal skeleton inEohiodonis nearly identical to that inHiodon.The traditionally accepted Notopteroidei, containing Lycopteridae, Hiodontidae, and Notopteridae, is a polypheletic group. The Asian fossil family Lycopteridae is not more closely related to Hiodontidae than it is to other taxa in the Osteoglossomorpha, but is sister to all other Osteoglossomorpha. The Hiodontiformes sensu stricto, including only the family Hiodontidae, is the sister-group of the Osteoglossiformes. This family is not more closely related to notopterids than to other taxa in Osteoglossiformes. The Notopteridae are most closely related to the Mormyroidea; together they and the fossil family Ostariostomidae constitute the sister-group of the Osteoglossoidei.Fossil records of Hiodontiformes sensu stricto and Notopteroidei indicate a widespread pre-Neogene biogeographic range of these freshwater teleosts, suggesting that extinction must have been involved in the Cenozoic evolution of these two osteoglossomorph sublineages.

A large sample of embryological material of the North American paddlefish Polyodon spathula (Acipenseriformes: Polyodontidae) confirms that early development in Polyodon is very similar to that reported for the sister group of Polyodontidae, the sturgeons (Acipenseridae). Polyodon illustrates many basic aspects of acipenseriform (and actinopterygian) head development that have not been adequately described. In this paper, we provide an overview of external features of cranial development using scanning electron microscopy. The observations are correlated with staging schemes previously proposed for paddlefishes and other acipenseriforms. Events that occur after the start of neurulation (stage 19) to the start of feeding (stage 46) are emphasized. New information on the structure and folding of the mandibular and hyoid segments permits an understanding of the early development of the pharyngeal region. In addition, we offer new descriptions of the hatching gland, the olfactory organ, the sensory barbel, and the initiation of paddle outgrowth. We also comment on the mode of origin of the hypophysis, and refute the notion that it is derived from the lips of the anterior neuropore as suggested in older literature. This information sets the stage for future comparative and experimental studies of the embryology of basal actinopterygians. © 1992 Wiley-Liss, Inc.

The monotypic family †Ostariostomidae Schaeffer, 1949 is represented by a single specimen †Ostariostoma wilseyi Schaeffer, 1949. This unique and enigmatic fossil is the impression of the left side of a complete, articulated skeleton from Upper Cretaceous or lower Paleocene freshwater deposits of the Livingston Group in Montana. It was originally described based on the incompletely prepared type specimen and identified as a clupeoid. Based on a more complete preparation of the holotype, we redescribe †O. wilseyi in previously unknown detail and reexamine its phylogenetic relationships. It clearly is not a clupeoid because it lacks all known derived characters of Clupeomorpha. Unfortunately, even based on the additional morphological information available to us, we were unable to clearly identify †Ostariostoma even to superorder. Our questionable assignment of †Ostariostoma to Osteoglossomorpha (possibly a hiodontoid) is not strongly supported and needs to be further tested with additional material...

Ischyodus dolloi Leriche 1902, the youngest record of the species, and Chimaera seymourensis sp. nov. are described from the La Meseta Formation, Late Eocene of Seymour Island, Antarctic Peninsula.

On the basis of a skull from the late Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, a gadiform fish is reported from the Antarctic region for the first time. This specimen, the most completely preserved fossil teleost cranium yet described from Antarctica, provides convincing evidence for the presence of Gadiformes in a far southerly location under temperate climatic conditions 40 m.y. ago. The exoccipital condyles, supraoccipital and lambdoidal crests, and post-temporal and supratemporal fossae are well preserved, as are the roofing bones on the posterior half of the skull. Comparative osteological study indicates that these features are very similar in appearance to those of merlucciids (hakes) and gadids (cods).

Saniwa ensidens is a pivotal taxon for understanding varanid evolution. A complete specimen of Saniwa ensidens was recently described, offering important new insights into the morphology of this taxon. We apply these new data to a broader-scale study of squamate relationships in order to understand the phylogenetic position of Saniwa ensidens and of varanids more generally. Among the other fossils included in our analysis were the Eocene taxon ‘‘Saniwa’’ feisti, the Miocene Varanus rusingensis, and the giant Pleistocene varanid Megalania prisca. We compare the phylogenetic hypothesis from our analysis of morphology with a recent molecular-based hypothesis and find numerous differences in the phylogenetic relationships within Varanus .W e constrained our morphological data set to the phylogenetic pattern presented by the molecular data to further analyze the possible phylogenetic relationships of the fossil taxa. Our analyses show that Saniwa ensidens is the sister taxon to crown-group Varanus and that ‘‘Saniwa’’ feisti is a basal member of the varanid lineage, not closely related to Saniwa ensidens. Both Varanus rusingensis and Megalania prisca are members of the crown radiations of Varanus.

Acipenseriformes occupy a special place in the history of ideas concerning fish evolution, but in many respects, phylogenetic studies of the group remain in their infancy. Even such basic questions as the monophyly of Acipenser (the largest genus) are unanswered. We define relationships based on comparative osteology, which allows us to incorporate well-preserved fossils into analyses. Acipenseriformes has existed at least since the Lower Jurassic (approximately 200 MYBP), and all fossil and recent taxa are from the Holarctic. Phylogenetic relationships among Paleozoic and Early Mesozoic actinopterygians are problematic, but most workers agree that Acipenseriformes is monophyletic and derived from some component of ‘paleonisciform’ fishes. (‘Paleonisciformes’ is a grade of primitive non-neopterygian actinopterygians, sensu Gardiner 1993.) Taxa discussed in comparison here are: †Cheirolepis, Polypterus, †Mimia. †Moythomasia, †Birgeria, †Saurichthys, Lepisosteus and Amia. We review generic diversity within the four nominal families of fossil and recent Acipenseriformes (†Chondrosteidae, †Peipiaosteidae, Polyodontidae, and Acipenseridae), and provide a cladogram summarizing osteological characters for those four groups. Monophyly of the two extant families is well-supported, but there are no comprehensive studies of all of the known species and specimens of †Chondrosteidae and †Peipiaosteidae. As a result, sister-group relationships among †Chondrosteidae, †Peipiaosteidae, and Acipenseroidei (= Polyodontidae + Acipenseridae)are unresolved. We discuss five features fundamental to the biology of acipenseriforms that benefit from the availability of our new phylogenetic hypothesis: (1) specializations of jaws and operculum relevant to jaw protrusion, feeding, and ram ventilation; (2) anadromy or potamodromy and demersal spawning; (3) paedomorphosis and evolution of the group; (4) the biogeography of Asian and North American polyodontids and scaphirhynchines; and (5) the great abundance of electroreceptive organs in the rostral and opercular regions. Finally, we summarize our nomenclatural recommendations.

The feeding mechanism of gars (Ginglym- odi : Lepisosteidae) is characterized by cranial elevation and lower jaw rotation but minimal cranial kinesis. Gar jaws have numerous, sharply pointed, elongate teeth for capture of evasive prey. Their mandibles range from rel- atively short to extremely long depending on the species. Jaw length and lever dimensions were hypothesized to affect the biomechanics of force and motion during feed- ing, according to simple mechanical models of muscles exerting force through first- or third-order levers. A mor- phometric protocol was used to measure the jaw structure of seven living and five fossil species of gar and these data were used to calculate the mechanical advantage (a mea- sure of force transmission) for both opening and closing of the mandible. Gars were found to possess low mechanical advantage (MA) and high transmission of motion, al- though gars occupy a range of biomechanical states across the continuum of force vs. velocity transmission. The long- nose gar, Lepisosteus osseus, has one of the lowest jaw closing MAs (0.05) ever measured in fishes. Intraspecific lever mechanics were also calculated for a developmental series (from feeding larvae to adults) of L. osseus and Atractosteus spatula. A characteristic ontogenetic curve in MA of the lower jaw was obtained, with a large decrease in MA between larva and juvenile, followed by a steady in- crease during adult growth. This curve correlates with a change in prey type, with the small, robust-jawed individ- uals feeding mainly on crustaceans and insects and the large, long-jawed individuals of all species becoming mainly piscivorous. Principal components analysis of functionally important morphometrics shows that several gar species occupy different regions of functional morpho- space. Some fossil gar species are also placed within func- tional morphospace using this approach. J. Morphol. 000: 000 - 000, 2005. © 2004 Wiley-Liss, Inc.