Fragmentary Fossils Research Articles

A new species of the Pleistocene furnariid Pseudoseisuropsis (Aves, Passeriformes)

ABSTRACTPseudoseisuropsis wintu sp. nov. is described from cranial material that had formerly been designated as a paratype of the extinct Pseudoseisuropsis nehuen. Thorough comparisons were made between the cranial specimens ascribed to Pseudoseisuropsis and many extant furnariid species. This new species is lower Pleistocene in age and increases the known diversity of Pseudoseisuropsis to three species. Cladistic analyses were performed using 43 cranial characters and a backbone constraint based on a well-supported phylogeny from a recent molecular analysis. In the most parsimonious tree, Pseudoseisuropsis was retrieved as a sister group of woodcreepers (Dendrocolaptinae) with low support. However, slightly suboptimal hypotheses, which could not be completely ruled out, suggest that this genus may be more closely related to other clades of Furnariidae. Hence, we agree with previous authors in regarding Pseudoseisuropsis as Furnariidae Incertae sedis. In addition, two fragmentary fossils ascribed to Pseudoseisuropsis were included in taxonomic comparisons: P. cuelloi, in order to assess the possibility that P. wintu sp. nov. belongs to that species, and another paratype of P. nehuen, to reassess its taxonomic identity.http://zoobank.org/urn:lsid:zoobank.org:pub:D26FF563-B9DB-48BD-BA9F-8C54CD13F03ESUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Stefanini, M. I., R. O. Gómez, and C. P. Tambussi. 2016. A new species of the Pleistocene furnariid Pseudoseisuropsis (Aves, Passeriformes). Journal of Vertebrate Paleontology. DOI: 10.1080–02724634.2016.1100630.

Contextualising primate origins--an ecomorphological framework.

Ecomorphology - the characterisation of the adaptive relationship between an organism's morphology and its ecological role - has long been central to theories of the origin and early evolution of the primate order. This is exemplified by two of the most influential theories of primate origins: Matt Cartmill's Visual Predation Hypothesis, and Bob Sussman's Angiosperm Co-Evolution Hypothesis. However, the study of primate origins is constrained by the absence of data directly documenting the events under investigation, and has to rely instead on a fragmentary fossil record and the methodological assumptions inherent in phylogenetic comparative analyses of extant species. These constraints introduce particular challenges for inferring the ecomorphology of primate origins, as morphology and environmental context must first be inferred before the relationship between the two can be considered. Fossils can be integrated in comparative analyses and observations of extant model species and laboratory experiments of form-function relationships are critical for the functional interpretation of the morphology of extinct species. Recent developments have led to important advancements, including phylogenetic comparative methods based on more realistic models of evolution, and improved methods for the inference of clade divergence times, as well as an improved fossil record. This contribution will review current perspectives on the origin and early evolution of primates, paying particular attention to their phylogenetic (including cladistic relationships and character evolution) and environmental (including chronology, geography, and physical environments) contextualisation, before attempting an up-to-date ecomorphological synthesis of primate origins.

First FossilAlligatorfrom the Late Eocene of Nebraska and the Late Paleogene Record of Alligators in the Great Plains

Abstract Fragmentary fossils have been tentatively attributed to Alligator from the Eocene of Wyoming, North Dakota, Saskatchewan, and Utah. The earliest definitive temporal and geographic range of Alligator has been limited to the late Eocene and early Oligocene Chadron and Brule Formations of the White River Badlands in South Dakota, represented by fossils of Alligator prenasalis. New fossils from the Chadron Formation in northwestern Nebraska expand the definitive geographic range of Alligator during the late Eocene. Results from a cladistic analysis of 28 alligatoroid species using 181 morphological characters support the identification of the new specimens as representing the most basally divergent taxon within Alligator, suggesting that they likely represent A. prenasalis; however, a lack of diagnostic features in the Nebraska specimens prevents a definitive assignment to this species. Limited occurrence data may indicate that Alligator experienced a reduction in biogeographic range following global...

New material of Moropus (Perissodactyla, Chalicotheriidae, Schizotheriinae) from the early Hemingfordian Rose Creek Member of the John Day Formation, Oregon, U.S.A.

ABSTRACTA juvenile maxilla of Moropus with DP3–M1, collected from the early Hemingfordian (He1) Picture Gorge 36 local fauna of the Rose Creek Member of the John Day Formation of Oregon, U.S.A., is the best-preserved chalicothere specimen yet collected from the John Day Basin. It also provides additional understanding of early Miocene Schizotheriinae (Perissodactyla, Chalicotheriidae) in western North America. Although Coombs et al. attributed all of the John Day chalicotheres to Moropus oregonensis, the new specimen resembles in size and morphology some of its early Hemingfordian contemporaries from the Runningwater Formation of the Great Plains and is referred to Moropus sp. Moropus sp. can thus be added to the oreodont Merycochoerus magnus, the amphicyonid Daphoenodon (Borocyon) robustum, the dromomerycid Barbouromeryx, the moschid Parablastomeryx schultzi, and the equid Parahippus pawniensis as John Day taxa with close relatives in the early Hemingfordian of the Great Plains. Further, the identification of the fragmentary chalicothere fossils from the John Day Formation is made more complex by the likely presence of more than one species there during the early Miocene.Citation for this article: Coombs, M. C., and R. M. Hunt Jr. 2015. New material of Moropus (Perissodactyla, Chalicotheriidae, Schizotheriinae) from the early Hemingfordian Rose Creek Member of the John Day Formation, Oregon, U.S.A. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1009992.

A new small pliopithecoid primate from the Middle Miocene of Thailand

Pliopithecoids represent a monophyletic group of putative stem catarrhines whose evolutionary history is incompletely known. They have been recorded from Europe and Asia, between the late Early Miocene and the Late Miocene. Asian pliopithecoids are less well documented than their European counterparts, often being represented by a fragmentary fossil record. New discoveries are therefore critical to reconstruct the evolutionary history of the whole group. Here, we describe two isolated molars from Ban San Klang, a late Middle Miocene locality in northern Thailand, which confirms the presence of pliopithecoids in Southeast Asia. The lower molar had originally been described as being that of a dendropithecoid, but it was later recognized as pertaining to a pliopithecoid. The discovery, in the same locality, of an additional upper molar attributed to the same species confirms the pliopithecoid status of this taxon and highlights its distinctiveness with respect to other known Asian pliopithecoids. However, the mosaic of primitive and autapomorphic features characterizing this Thai fossil, as well as its limited anatomical representation, preclude us from assigning it to either of the known pliopithecid subfamilies. Nevertheless, it represents the only pliopithecoid in Southeast Asia and displays a mosaic of unique characters which emphasizes the peculiarity of that province, as suggested previously with respect to its hominoid primate.

A Review of the Fossil Record of New World Turtles of the CladePan-Trionychidae

Abstract Turtles of the clade Pan-Trionychidae have a rich, but fragmentary fossil record in the New World, ranging from the Late Cretaceous to the Holocene. The clade immigrated to North America from Asia no later than the Cenomanian. From the Campanian to the middle Eocene, pan-trionychid diversity in the New World was higher than it is today. In the Neogene, pan-trionychids inhabited southern North America and coastal regions of northern South America. Their range subsequently contracted, and extant New World pan-trionychids are now limited to the eastern third of temperate North America. The ecology of extinct pan-trionychids was likely similar to that of extant pan-trionychids, although novel feeding ecology has been hypothesized for some morphologically derived taxa. Current phylogenies of crown Trionychidae recognize two major clades, Cyclanorbinae and Trionychinae, but the placement of most fossil taxa remains poorly resolved relative to these two primary clades. A taxonomic review of 101 named Ne...

Bovid ecomorphology and hominin paleoenvironments of the Shungura Formation, lower Omo River Valley, Ethiopia

The Shungura Formation in the lower Omo River Valley, southern Ethiopia, has yielded an important paleontological and archeological record from the Pliocene and Pleistocene of eastern Africa. Fossils are common throughout the sequence and provide evidence of paleoenvironments and environmental change through time. This study developed discriminant function ecomorphology models that linked astragalus morphology to broadly defined habitat categories (open, light cover, heavy cover, forest, and wetlands) using modern bovids of known ecology. These models used seven variables suitable for use on fragmentary fossils and had overall classification success rates of >82%. Four hundred and one fossils were analyzed from Shungura Formation members B through G (3.4–1.9 million years ago). Analysis by member documented the full range of ecomorph categories, demonstrating that a wide range of habitats existed along the axis of the paleo-Omo River. Heavy cover ecomorphs, reflecting habitats such as woodland and heavy bushland, were the most common in the fossil sample. The trend of increasing open cover habitats from Members C through F suggested by other paleoenvironmental proxies was documented by the increase in open habitat ecomorphs during this interval. However, finer grained analysis demonstrated considerable variability in ecomorph frequencies over time, suggesting that substantial short-term variability is masked when grouping samples by member. The hominin genera Australopithecus, Homo, and Paranthropus are associated with a range of ecomorphs, indicating that all three genera were living in temporally variable and heterogeneous landscapes. Australopithecus finds were predominantly associated with lower frequencies of open habitat ecomorphs, and high frequencies of heavy cover ecomorphs, perhaps indicating a more woodland focus for this genus.

Predicting euarchontan body mass: A comparison of tarsal and dental variables.

Multiple meaningful ecological characterizations of a species revolve around body mass. Because body mass cannot be directly measured in extinct taxa, reliable body mass predictors are needed. Many published body mass prediction equations rely on dental dimensions, but certain skeletal dimensions may have a more direct and consistent relationship with body mass. We seek to evaluate the reliability of prediction equations for inferring euarchontan body mass based on measurements of the articular facet areas of the astragalus and calcaneus. Surface areas of five astragalar facets (n = 217 specimens) and two calcaneal facets (n = 163) were measured. Separate ordinary least squares and multiple regression equations are presented for different levels of taxonomic inclusivity, and the reliability of each equation is evaluated with the coefficient of determination, standard error of the estimate, mean prediction error, and the prediction sum of squares statistic. We compare prediction errors to published prediction equations that utilize dental and/or tarsal measures. Finally, we examine the effects of taxonomically specific regressions and apply our equations to a diverse set of non-primates. Our results reveal that predictions based on facet areas are more reliable than most linear dental or tarsal predictors. Multivariate approaches are often better than univariate methods, but require more information (making them less useful for fragmentary fossils). While some taxonomically specific regressions improve predictive ability, this is not true for all primate groups. Among individual facets, the ectal and fibular facets of the astragalus and the calcaneal cuboid facet are the best body mass predictors. Since these facets have primarily concave curvature and scale with positive allometry relative to body mass, it appears that candidate skeletal proxies for body mass can be identified based on their curvature and scaling coefficients.

Variationin the ilium of central European water frogs Pelophylax (Amphibia, Ranidae) and its implications for species-level identification of fragmentary anuran fossils.

In the opinion of all field herpetologists and archaeozoologists, green frogs (living and sub-fossil specimens)are among the most difficult European amphibians to identify. Here, we examine the intra- and interspecific variation in both continuous and discrete iliac characters for refining the criteria for species-level identification among Europeangreen frogs Pelophylaxridibundus,Pelophylaxlessonae andtheir associated klepton Pelophylaxkl.P.esculentus (Amphibia,Ranidae). Atotal of 454 ilia of modern green frogs from the former German Democratic Republic have been studied: 168 for P.lessonae (86of males and 82 of females), 118 for P.ridibundus (44of males and 74 of females) and 168 for P.kl.P.esculentus (86of males and 82 of females). The origin, sex, population structure and phenotype are known for each of the studied specimens. Eight variables have been taken (one angle and seven measurements), mainly on the distal part of the element in order to be able to apply them to fragmentary fossil ilia. Interspecific variations, sexual dimorphism and population structure have been investigated. Results suggest that the secure determination of a single fossil ilium at species level is quite impossible, but that at population level, it may be possible to distinguish between a 'pure' species or a 'pure' species plus its cohabiting hybrid form, as some minor differences have been evidencedin particular in the angle of the tubersuperior inrelation to iliac's main axis (character 2) and the width of the parsascendens (character8); two parameters significantly non size-dependent. No sexual dimorphism has been detected, except for P.lessonae. We propose here a new biometrical method in order to differentiate between the fossil ilia of central European water frogs (genus Pelophylax) at population level.

New material and evaluation of the chronostratigraphic position of Daphoenictis tedfordi (Mammalia, Carnivora, Amphicyonidae), a cat-like carnivoran from the latest Eocene of northwestern Nebraska, USA

One of the most enigmatic amphicyonid carnivorans, the cat-like Daphoenictis tedfordi, is now known from 12 cranio-dental specimens from North America. The most recently recovered specimen, a partial right hemimandible (UNSM 27015) described herein, adds considerably to our knowledge of this taxon, and in completeness rivals the holotype of the species. Daphoenictis tedfordi is distributed from Saskatchewan to Montana, continuing to Nebraska, Colorado, and Wyoming, with nearly 50% of the specimens coming from northwest Nebraska. The chronostratigraphy and geographic locus of the Nebraska hypodigm is the focus of this report. UNSM 27015 links the fragmentary fossils of the Nebraska hypodigm to the holotype (Cypress Hills, Saskatchewan). Chronologic evidence indicates this species is restricted to the Chadronian (late Eocene) age. Recent astronomical calibration applied to late Eocene-Oligocene tuffs places the species entirely in the middle Chadronian with a single individual found in the late early Chadronian biochron. Grant S. Boardman. Department of Physics, Astronomy and Geology, Berry College, Mount Berry, Georgia 30149, USA, gboardman@berry.edu Robert M. Hunt, Jr. Department of Earth and Atmospheric Sciences, University of Nebraska, Lincoln, Nebraska 68588, USA, rhunt2@unl.edu

Feeding habits of extant and fossil canids as determined by their skull geometry

AbstractThe canids belong to one of the most prominent families of mammalian carnivores. Feeding adaptations of extant species is well documented by field observations; however, we are still missing palaeoecological insights for many enigmatic fossil specimens. We employ geometric morphometrics to quantify skull size and shape in extant and fossil members of the Canini tribe, inclusive of jackals and wolf‐like taxa. Skull data are tested to identify correlates of dietary adaptations in extant species for predicting adaptations in fossils. Main vectors of shape variation correlate with the relative skull‐palatal length, the position of the upper carnassial tooth and the anterior tip of the secondary palate. Allometry occurs in the palatal shape but size explains only a small fraction (about 4%) of shape variance. Although we quantified only palatal and tooth shape for the inclusion of fragmentary fossils, discriminant function analysis successfully classify extant Canini in dietary groups (small, medium and large prey specialist) with 89% of accuracy. The discriminant functions provide insights into many enigmatic specimens such as Eucyon adoxus (=small prey), fossil jackal‐like from Koobi Fora formation (=small prey) and the Plio‐Pleistocene Old World canid guild (Canis etruscus, C. arnensis and Lycaon falconeri). Clearly, both skull size and shape are excellent predictors of feeding habits in Canini thus also provide information about fossil taxonomic affinities.

Diverse barklice (Psocodea) from Late Cretaceous Vendean amber

The fossil psocodeans from Late Cretaceous (Cenomanian to Santonian) amber of Vendee, in northwestern France, are studied. Two new genera and three new species are described and illustrated, as Proprionoglaris axioperierga n. sp. (Archaeatropidae), Scocompus atelisus n. gen. and sp. (uncertain family within the Amphientometae), and Mesopsocoides dupei n. gen. and sp. (earliest fossil record of the Mesopsocidae). The new fossils are distinguished from their congeners, and their respective systematic placement is discussed. Other fragmentary fossil psocodeans from the same outcrop are illustrated and discussed.

Calculating hominin and nonhuman anthropoid femoral head diameter from acetabular size.

Femoral head size provides important information on body size in extinct species. Although it is well-known that femoral head size is correlated with acetabular size, the precision with which femoral head size can be estimated from acetabular size has not been quantified. The availability of accurate 3D surface models of fossil acetabular remains opens the possibility of obtaining accurate estimates of femoral head size from even fragmentary fossil remains [Hammond et al.,: Am J Phys Anthropol 150 (2013) 565-578]. Here we evaluate the relationship between spheres fit to surface models of the femoral head and acetabulum of a large sample of extant anthropoid primates. Sphere diameters are tightly correlated and scale isometrically. In spite of significant taxonomic and possibly functional differences in the relationship between femoral head size and acetabulum size, percent prediction errors of estimated femoral head size remain low regardless of the taxonomic composition of the reference sample. We provide estimates of femoral head size for a series of fossil hominins and monkeys.

Lauraceous Fossil Flowers from the Kamikitaba Assemblage (Coniacian, Late Cretaceous) of Northeastern Japan (Lauraceae)

A new genus and species of Lauraceae, Microlaurus perigynus gen. et sp. nov. is described based on fossil charcoalified flower buds recovered from the Kamikitaba assemblage (early Coniacian, Late Cretaceous; ca. 89 million years before present (myr BP)) in the Ashizawa Formation (Asamigawa Member) of the Futaba Group in northeastern Japan. Analysis of the internal structure of the fossil buds using synchrotron-radiation X-ray microtomography (SRXTM) at the 2-BM-B beamline of the Advanced Photon Source (APS), Argonne National Laboratory, shows that the flowers are small, pedicellate, bisexual, trimerous, and actinomorphic, with small outer tepals, larger inner tepals, three whorls of stamens, an innermost androecial whorl composed of staminodia, and a unicarpellate gynoecium containing a single ovule. Microlaurus perigynus is assigned to the Lauraceae based on the regular trimerous floral organization and other details of floral structure, but it is distinguished from most previously described lauraceous fossil flowers by the poorly differentiated filament and anther in the stamens of the third whorl and the marked size difference between the small outer tepals and the large inner tepals. Also unusual are the paired glandular appendages that appear to be associated with the first (outermost) whorl of stamens, rather than the stamens of the third whorl, although the precise position is not fully clear. The same feature occurs in Hernandiaceae, the sister group of Lauraceae, as well as in Powhatania connata, an earlier but fragmentary lauralean fossil flower from the Early to Middle Albian of Virginia. Microlaurus perigynus adds to the floral diversity of Lauraceae known from the Late Cretaceous, and its presence in the Kamikitaba assemblage from Japan underlines the broad geographic distribution and floristic significance of lauraceous plants during the Late Cretaceous.

Arctic plesiosaurs from the Lower Cretaceous of Melville Island, Nunavut, Canada

An expedition to Melville Island in Nunavut, Canada, recovered the fragmentary fossils of several plesiosaurs from non-marine deposits of the Hauterivian–Aptian Isachsen Formation. These plesiosaur fossils are some of the oldest Early Cretaceous records of the group in North America, and they likely predate the formation of a continuous Western Interior Seaway. The plesiosaurs from Melville Island appear to be primarily juveniles, and would have been living in a region that experienced at least seasonally cool temperatures. The presence of these fossils in a fluvial deposit support previous suggestions that juvenile plesiosaurs may have preferentially inhabited shallower waters rather than open marine environments. These fossils also show that polycotylid plesiosaurs were able to rapidly disperse and colonize high latitude coastal regions, as their occurrence in Arctic Canada only slightly postdates the first confirmed appearance of the group in Australia.

Osteological Histology of the Pan‐Alcidae (Aves, Charadriiformes): Correlates of Wing‐Propelled Diving and Flightlessness

ABSTRACTAlthough studies of osteological morphology, gross myology, myological histology, neuroanatomy, and wing‐scaling have all documented anatomical modifications associated with wing‐propelled diving, the osteohistological study of this highly derived method of locomotion has been limited to penguins. Herein we present the first osteohistological study of the derived forelimbs and hind limbs of wing‐propelled diving Pan‐Alcidae (Aves, Charadriiformes). In addition to detailing differences between wing‐propelled diving charadriiforms and nondiving charadriiforms, microstructural modifications to the humeri, ulnae and femora of extinct flightless pan‐alcids are contrasted with those of volant alcids. Histological thin‐sections of four species of pan‐alcids (Alca torda, †Alca grandis, †Pinguinus impennis, †Mancalla cedrosensis) and one outgroup charadriiform (Stercorarius longicaudus) were compared. The forelimb bones of wing‐propelled diving charadriiforms were found to have significantly thicker (∼22%) cortical bone walls. Additionally, as in penguins, the forelimbs of flightless pan‐alcids are found to be osteosclerotic. However, unlike the pattern documented in penguins that display thickened cortices in both forelimbs and hind limbs, the forelimb and hind limb elements of pan‐alcids display contrasting microstructural morphologies with thickened forelimb cortices and relatively thinner femoral cortices. Additionally, the identification of medullary bone in the sampled †Pinguinus impennis specimen suggests that further osteohistological investigation could provide an answer to longstanding questions regarding sexual dimorphism of Great Auks. Finally, these results suggest that it is possible to discern volant from flightless wing‐propelled divers from fragmentary fossil remains. Anat Rec, 297:188–199, 2014. © 2013 Wiley Periodicals, Inc.

Ecomorphology of radii in Canidae (Carnivora): application to fragmentary fossils from Plio-Pleistocene hominin assemblages

Fragmentary long bone material from fossil Carnivora is rarely considered to support palaeoenvironmental reconstructions. Here, we use morphometry of the radius in extant carnivorans of the dog family (Canidae) to reconstruct the palaeobiology of extinct canids from Olduvai Gorge, Tanzania (Bed I and II) and Koobi Fora, Kenya. We use radius morphometrics to predict adaptation to prey size and introduce a new method for quantifying canid habitat adaptations based on the geographic distributions of the extant species sampled. Linear Discriminant Function Analyses (DFA) and cluster neighbour-joining algorithms are employed to investigate radial morphometrics as described by 29 linear measurements. Results of our analyses suggest that a phylogenetic signal is present in radial morphometrics, even if it does not allow us to accurately discriminate among genera. A binary prey size categorisation of “small-medium” versus “large” prey can be more accurately predicted than a habitat categorisation scheme (Open, Mixed, Closed). The East African fossil specimens examined show morphometric affinities with the golden jackal (Canis aureus) and coyote (Canis latrans) and are likely attributable to the genus Canis. Fragmentary fossil specimens from Olduvai Gorge are predicted as habitat generalists (Open for Bed I and Mixed for Bed II) adapted for hunting small-medium prey, whereas the specimen from Koobi Fora was predicted as inhabiting mixed habitats and adapted for killing large prey. This study supports the inclusion of fossil Canidae in palaeoecological analyses attempting to clarify the palaeoenvironment of early hominin fossil sites.

Osteological Histology of the Pan‐Alcidae (Aves, Charadriiformes): Correlates of Wing‐Propelled Diving and Flightlessness

Although studies of osteological morphology, gross myology, myological histology, neuroanatomy, and wing-scaling have all documented anatomical modifications associated with wing-propelled diving, the osteohistological study of this highly derived method of locomotion has been limited to penguins. Herein we present the first osteohistological study of the derived forelimbs and hind limbs of wing-propelled diving Pan-Alcidae (Aves, Charadriiformes). In addition to detailing differences between wing-propelled diving charadriiforms and nondiving charadriiforms, microstructural modifications to the humeri, ulnae and femora of extinct flightless pan-alcids are contrasted with those of volant alcids. Histological thin-sections of four species of pan-alcids (Alca torda, †Alca grandis, †Pinguinus impennis, †Mancalla cedrosensis) and one outgroup charadriiform (Stercorarius longicaudus) were compared. The forelimb bones of wing-propelled diving charadriiforms were found to have significantly thicker (∼22%) cortical bone walls. Additionally, as in penguins, the forelimbs of flightless pan-alcids are found to be osteosclerotic. However, unlike the pattern documented in penguins that display thickened cortices in both forelimbs and hind limbs, the forelimb and hind limb elements of pan-alcids display contrasting microstructural morphologies with thickened forelimb cortices and relatively thinner femoral cortices. Additionally, the identification of medullary bone in the sampled †Pinguinus impennis specimen suggests that further osteohistological investigation could provide an answer to longstanding questions regarding sexual dimorphism of Great Auks. Finally, these results suggest that it is possible to discern volant from flightless wing-propelled divers from fragmentary fossil remains.

Skeletal Correlates for Body Mass Estimation in Modern and Fossil Flying Birds

Scaling relationships between skeletal dimensions and body mass in extant birds are often used to estimate body mass in fossil crown-group birds, as well as in stem-group avialans. However, useful statistical measurements for constraining the precision and accuracy of fossil mass estimates are rarely provided, which prevents the quantification of robust upper and lower bound body mass estimates for fossils. Here, we generate thirteen body mass correlations and associated measures of statistical robustness using a sample of 863 extant flying birds. By providing robust body mass regressions with upper- and lower-bound prediction intervals for individual skeletal elements, we address the longstanding problem of body mass estimation for highly fragmentary fossil birds. We demonstrate that the most precise proxy for estimating body mass in the overall dataset, measured both as coefficient determination of ordinary least squares regression and percent prediction error, is the maximum diameter of the coracoid’s humeral articulation facet (the glenoid). We further demonstrate that this result is consistent among the majority of investigated avian orders (10 out of 18). As a result, we suggest that, in the majority of cases, this proxy may provide the most accurate estimates of body mass for volant fossil birds. Additionally, by presenting statistical measurements of body mass prediction error for thirteen different body mass regressions, this study provides a much-needed quantitative framework for the accurate estimation of body mass and associated ecological correlates in fossil birds. The application of these regressions will enhance the precision and robustness of many mass-based inferences in future paleornithological studies.

Are characiform fishes Gondwanan in origin? Insights from a time-scaled molecular phylogeny of the Citharinoidei (Ostariophysi: Characiformes).

Fishes of the order Characiformes are a diverse and economically important teleost clade whose extant members are found exclusively in African and Neotropical freshwaters. Although their transatlantic distribution has been primarily attributed to the Early Cretaceous fragmentation of western Gondwana, vicariance has not been tested with temporal information beyond that contained in their fragmentary fossil record and a recent time-scaled phylogeny focused on the African family Alestidae. Because members of the suborder Citharinoidei constitute the sister lineage to the entire remaining Afro-Neotropical characiform radiation, we inferred a time-calibrated molecular phylogeny of citharinoids using a popular Bayesian approach to molecular dating in order to assess the adequacy of current vicariance hypotheses and shed light on the early biogeographic history of characiform fishes. Given that the only comprehensive phylogenetic treatment of the Citharinoidei has been a morphology-based analysis published over three decades ago, the present study also provided an opportunity to further investigate citharinoid relationships and update the evolutionary framework that has laid the foundations for the current classification of the group. The inferred chronogram is robust to changes in calibration priors and suggests that the origins of citharinoids date back to the Turonian (ca 90 Ma) of the Late Cretaceous. Most modern citharinoid genera, however, appear to have originated and diversified much more recently, mainly during the Miocene. By reconciling molecular-clock- with fossil-based estimates for the origins of the Characiformes, our results provide further support for the hypothesis that attributes the disjunct distribution of the order to the opening of the South Atlantic Ocean. The striking overlap in tempo of diversification and biogeographic patterns between citharinoids and the African-endemic family Alestidae suggests that their evolutionary histories could have been strongly and similarly influenced by Miocene geotectonic events that modified the landscape and produced the drainage pattern of Central Africa seen today.