Proboscidean Mitogenomics: Chronology and Mode of Elephant Evolution Using Mastodon as Outgroup

Abstract: We have sequenced the complete mitochondrial genome of the extinct American mastodon (Mammut americanum) from an Alaskan fossil that is between 50,000 and 130,000 y old, extending the age range of genomic analyses by almost a complete glacial cycle. The sequence we obtained is substantially different from previously reported partial mastodon mitochondrial DNA sequences. By comparing those partial sequences to other proboscidean sequences, we conclude that we have obtained the first sequence of mastodon DNA ever reported. Using the sequence of the mastodon, which diverged 24–28 million years ago (mya) from the Elephantidae lineage, as an outgroup, we infer that the ancestors of African elephants diverged from the lineage leading to mammoths and Asian elephants approximately 7.6 mya and that mammoths and Asian elephants diverged approximately 6.7 mya. We also conclude that the nuclear genomes of the African savannah and forest elephants diverged approximately 4.0 mya, supporting the view that these two groups represent different species. Finally, we found the mitochondrial mutation rate of proboscideans to be roughly half of the rate in primates during at least the last 24 million years.

elephant
mastodon
outgroup
elephantidae lineage
mammoth


Dental Microwear and Diet of the Plio-Pleistocene Hominin Paranthropus boisei

Abstract: The Plio-Pleistocene hominin Paranthropus boisei had enormous, flat, thickly enameled cheek teeth, a robust cranium and mandible, and inferred massive, powerful chewing muscles. This specialized morphology, which earned P. boisei the nickname “Nutcracker Man”, suggests that this hominin could have consumed very mechanically challenging foods. It has been recently argued, however, that specialized hominin morphology may indicate adaptations for the consumption of occasional fallback foods rather than preferred resources. Dental microwear offers a potential means by which to test this hypothesis in that it reflects actual use rather than genetic adaptation. High microwear surface texture complexity and anisotropy in extant primates can be associated with the consumption of exceptionally hard and tough foods respectively. Here we present the first quantitative analysis of dental microwear for P. boisei. Seven specimens examined preserved unobscured antemortem molar microwear. These all show relatively low complexity and anisotropy values. This suggests that none of the individuals consumed especially hard or tough foods in the days before they died. The apparent discrepancy between microwear and functional anatomy is consistent with the idea that P. boisei presents a hominin example of Liem's Paradox, wherein a highly derived morphology need not reflect a specialized diet.

morphology
food
dental microwear
microwear feature


Neoichnology of the desert scorpion Hadrurus arizonensis: burrows to biogenic cross lamination

Abstract: Bioturbation by terrestrial animals is common in arid and semi-arid continental environments. Scorpions have comprised a significant portion of the diversity of predatory arthropods in these environments from the Late Paleozoic to the Recent. Many scorpions are active burrowers and likely have a substantial, if rarely recognized, ichnofossil record. This project involved the study of the burrowing behaviors and trace morphologies of the scorpion Hadrurus arizonensis (Scorpiones: Caraboctonidae). Individual animals were placed into sediment-filled terrariums for two-to three-week periods after which burrows were cast, excavated, and described. Descriptions of the subsurface structures included architecture, dimensions, bioglyphs, complexity, and tortuosity. Additional experiments were run with differing sediment composition, density, and moisture to evaluate the animal's behavioral response to altering environmental conditions. Specimens of H. arizonensis burrowed by scratching and kicking loose sediment from the subsurface with the first two to three pairs of walking legs. The subsurface biogenic structures produced consisted of subvertical ramps, U-shaped burrows, helical burrows, and mazeworks. In the process of excavating the burrows, the desert scorpions also produced a hummocky surface topography as well as structures in dry, sandy sediment that resembled lamination and ripple cross-lamination. Increasing clay content and sediment density increased the complexity of burrow architectures produced. Reducing these variables limited the complexity of the burrows, reduced their likelihood of preservation, and increased the abundance of biogenic cross-lamination. Data collected from these and similar experimental studies can be applied to terrestrial ichnofossil assemblages in order to better interpret the paleoecology of ancient soil ecosystems.

scorpion
burrow
biogenic structure
variable


Actualización sistemática y filogenia de los proterotheriidae (Mammalia, litopterna) del “Mesopotamiense” (mioceno tardío) de Entre Ríos, Argentina

Abstract: A systematic update of the species of Proterotheriidae (Litopterna) from the “Mesopotamiense” of Entre Rios Province (Argentina) is performed, and their phylogenetic relationships with other members of the family are tested. Brachytherium cuspidatum Ameghino is validated (considered nomen dubium hitherto) and a sexual dimorphism is proposed for this species. This idea is based on metric, but not morphological, differences among the specimens included in it, which is supported by a discriminant analysis. Neobrachytherium ameghinoi Soria and Proterotherium cervioides Ameghino are also valid, and Epitherium? eversus (Ameghino) is assigned to the genus Diadiaphorus. Detailed descriptions of the specimens are presented for each taxon, and their diagnosis are revised.

proterotheriidae litopterna mesopotamiense argentina


Gigantism of the Australian Diprotodon Owen 1838 (Marsupialia, Diprotodontoidea) through the Pleistocene

Abstract: Diprotodon Owen, 1838 was one of the first fossil mammals described from Australia and has the distinction of being the largest ever marsupial. However, until recently its taxonomy was unclear and knowledge of its continental distribution, palaeoecology and evolution was poorly known. This paper describes cranial elements from an unusually small‐bodied Diprotodon from the Early Pleistocene Nelson Bay Formation, Portland, Australia. It is intermediate in size between the smaller‐bodied Pliocene ancestor, Euryzygoma dunense de Vis 1895 and the larger‐bodied Late Pleistocene D. optatum Owen, 1838 . However, it is morphologically inseparable from Late Pleistocene Diprotodon and is here referred to as D. ?optatum. A temporal morphocline most parsimoniously explains the medium body size of the Nelson Bay taxon; thus we provide the first evidence of a transitional form within Diprotodon. The cause(s) of gigantism of the E. dunense–D. ?optatum–D. optatum lineage through the late Cainozoic is unclear but most likely involved the physiological response to changes in the physical and/or biotic environment. Although the size changes within the lineage may have been initially advantageous, they were most likely disadvantageous when the optimum body size was obtained. Our results suggest that Diprotodon was at its largest ever body size during the Late Pleistocene – the time period that coincided with its extinction. Copyright © 2009 John Wiley & Sons, Ltd.


The First Known Asian Hispanomeryx (Mammalia, Ruminantia, Moschidae)

Abstract: The first known Asian Hispanomeryx (Mammalia, Ruminantia, Moschidae) Israel M. Sanchez a , Daniel Demiguel b , Victoria Quiralte a & Jorge Morales a a Departamento de Paleobiologia, Museo Nacional de Ciencias Naturales-CSIC, C/ Jose Gutierrez Abascal 2, 28006, Madrid, Spain b Institut Catala de Paleontologia, Universitat Autonoma de Barcelona, Edifici ICP, Campus de la UAB s/n, 08193, Cerdanyola del Valles, Barcelona, Spain


Microbes and mass extinctions: paleoenvironmental distribution of microbialites during times of biotic crisis

Abstract: Widespread development of microbialites characterizes the substrate and ecological response during the aftermath of two of the ‘big five’ mass extinctions of the Phanerozoic. This study reviews the microbial response recorded by macroscopic microbial structures to these events to examine how extinction mechanism may be linked to the style of microbialite development. Two main styles of response are recognized: (i) the expansion of microbialites into environments not previously occupied during the pre‐extinction interval and (ii) increases in microbialite abundance and attainment of ecological dominance within environments occupied prior to the extinction. The Late Devonian biotic crisis contributed toward the decimation of platform margin reef taxa and was followed by increases in microbialite abundance in Famennian and earliest Carboniferous platform interior, margin, and slope settings. The end‐Permian event records the suppression of infaunal activity and an elimination of metazoan‐dominated reefs. The aftermath of this mass extinction is characterized by the expansion of microbialites into new environments including offshore and nearshore ramp, platform interior, and slope settings. The mass extinctions at the end of the Triassic and Cretaceous have not yet been associated with a macroscopic microbial response, although one has been suggested for the end‐Ordovician event. The case for microbialites behaving as ‘disaster forms’ in the aftermath of mass extinctions accurately describes the response following the Late Devonian and end‐Permian events, and this may be because each is marked by the reduction of reef communities in addition to a suppression of bioturbation related to the development of shallow‐water anoxia.

mass extinction
microbialite
biotic crisis
slope setting
nearshore ramp


Fossil and Genetic Evidence for the Polyphyletic Nature of the Planktonic Foraminifera "Globigerinoides", and Description of the New Genus Trilobatus

Abstract: Planktonic foraminifera are one of the most abundant and diverse protists in the oceans. Their utility as paleo proxies requires rigorous taxonomy and comparison with living and genetically related counterparts. We merge genetic and fossil evidence of “Globigerinoides”, characterized by supplementary apertures on spiral side, in a new approach to trace their “total evidence phylogeny” since their first appearance in the latest Paleogene. Combined fossil and molecular genetic data indicate that this genus, as traditionally understood, is polyphyletic. Both datasets indicate the existence of two distinct lineages that evolved independently. One group includes “Globigerinoides” trilobus and its descendants, the extant “Globigerinoides” sacculifer, Orbulina universa and Sphaeroidinella dehiscens. The second group includes the Globigerinoides ruber clade with the extant G. conglobatus and G. elongatus and ancestors. In molecular phylogenies, the trilobus group is not the sister taxon of the ruber group. The ruber group clusters consistently together with the modern Globoturborotalita rubescens as a sister taxon. The re-analysis of the fossil record indicates that the first “Globigerinoides” in the late Oligocene are ancestral to the trilobus group, whereas the ruber group first appeared at the base of the Miocene with representatives distinct from the trilobus group. Therefore, polyphyly of the genus "Globigerinoides" as currently defined can only be avoided either by broadening the genus concept to include G. rubescens and a large number of fossil species without supplementary apertures, or if the trilobus group is assigned to a separate genus. Since the former is not feasible due to the lack of a clear diagnosis for such a broad genus, we erect a new genus Trilobatus for the trilobus group (type species Globigerina triloba Reuss) and amend Globoturborotalita and Globigerinoides to clarify morphology and wall textures of these genera. In the new concept, Trilobatus n. gen. is paraphyletic and gave rise to the Praeorbulina / Orbulina and Sphaeroidinellopsis / Sphaeroidinella lineages.

planktonic foraminifera
globigerinoides
new genus trilobatus
descendant
sphaeroidinella


Patterns of animal dispersal, vicariance and diversification in the Holarctic

Abstract: We analysed patterns of animal dispersal, vicariance and diversification in the Holarctic based on complete phylogenies of 57 extant non-marine taxa, together comprising 770 species, documenting biogeographic events from the Late Mesozoic to the present. Four major areas, each corresponding to a historically persistent landmass, were used in the analyses: eastern Nearctic (EN), western Nearctic (WN), eastern Palaeoarctic (EP) and western Palaeoarctic (WP). Parsimony-based tree fitting showed that there is no significantly supported general area cladogram for the dataset. Yet, distributions are strongly phylogenetically conserved, as revealed by dispersalvicariance analysis (DIVA). DIVA-based permutation tests were used to pinpoint phylogenetically determined biogeographic patterns. Consistent with expectations, continental dispersals (WP↔EP and WN↔EN) are significantly more common than palaeocontinental dispersals (WN↔EP and EN↔WP), which in turn are more common than disjunct dispersals (EN↔EP and WN↔WP). There is significant dispersal asymmetry both within the Nearctic (WN→EN more common than EN→WN) and the Palaeoarctic (EP→WP more common than WP→EP). CrossBeringian faunal connections have traditionally been emphasized but are not more important than cross-Atlantic connections in our data set. To analyse changes over time, we sorted biogeographic events into four major time periods using fossil, biogeographic and molecular evidence combined with a ‘branching clock’. These analyses show that trans-Atlantic distributions (EN–WP) were common in the Early–Mid Tertiary (70–20 Myr), whereas transBeringian distributions (WN–EP) were rare in that period. Most EN–EP disjunctions date back to the Early Tertiary (70–45 Myr), suggesting that they resulted from division of cross-Atlantic rather than cross-Beringian distributions. Diversification in WN and WP increased in the Quaternary (< 3 Myr), whereas in EP and EN it decreased from a maximum in the Early–Mid Tertiary.  2001 The Linnean Society of London


Asymmetric geographic range expansion explains the latitudinal diversity gradients of four major taxa of marine plankton

Abstract:
Abstract.
 Extensive investigation of the close association between biological diversity and environmental temperature has not yet yielded a generally accepted, empirically validated mechanism to explain latitudinal gradients of species diversity, which occur in most taxa. Using the highly resolved late Cenozoic fossil records of four major taxa of marine plankton, we show that their gradients arise as a consequence of asymmetric geographic range expansion rather than latitudinal variation in diversification rate, as commonly believed. Neither per capita speciation nor extinction rates trend significantly with temperature or latitude for these marine plankton. Species of planktonic foraminifera and calcareous nannoplankton that originate in the temperate zone preferentially spread toward and arrive earlier in the tropics to produce a normal gradient with tropical diversity peaks; by contrast, temperate-zone originating species of diatoms and radiolarians preferentially spread toward and arrive earlier in polar regions to produce reversed gradients with high-latitude diversity peaks. Our results suggest that temperature affects latitudinal diversity gradients chiefly by its effect on species' range limits rather than on probabilities of speciation and extinction. We show that this mechanism also appears to operate in various multicellular taxa, thus providing a widely applicable explanation for the origin of latitudinal diversity gradients.

geographic range expansion
latitudinal diversity gradient
marine plankton


A gigantic nothosaur (Reptilia: Sauropterygia) from the Middle Triassic of SW China and its implication for the Triassic biotic recovery

Abstract: The presence of gigantic apex predators in the eastern Panthalassic and western Tethyan oceans suggests that complex ecosystems in the sea had become re-established in these regions at least by the early Middle Triassic, after the Permian-Triassic mass extinction (PTME). However, it is not clear whether oceanic ecosystem recovery from the PTME was globally synchronous because of the apparent lack of such predators in the eastern Tethyan/western Panthalassic region prior to the Late Triassic. Here we report a gigantic nothosaur from the lower Middle Triassic of Luoping in southwest China (eastern Tethyan ocean), which possesses the largest known lower jaw among Triassic sauropterygians. Phylogenetic analysis suggests parallel evolution of gigantism in Triassic sauropterygians. Discovery of this gigantic apex predator, together with associated diverse marine reptiles and the complex food web, indicates global recovery of shallow marine ecosystems from PTME by the early Middle Triassic.

gigantic nothosaur
middle triassic
biotic recovery
mass extinction
marine reptile


The position of Hippopotamidae within Cetartiodactyla.

Abstract: The origin of late Neogene Hippopotamidae (Artiodactyla) involves one of the most serious conflicts between comparative anatomy and molecular biology: is Artiodactyla paraphyletic? Molecular comparisons indicate that Cetacea should be the modern sister group of hippos. This finding implies the existence of a fossil lineage linking cetaceans (first known in the early Eocene) to hippos (first known in the middle Miocene). The relationships of hippos within Artiodactyla are challenging, and the immediate affinities of Hippopotamidae have been studied by biologists for almost two centuries without resolution. Here, we compare opposing hypotheses implicating several "suiform" families. This morphological analysis of a comprehensive set of taxa and characters offers a robust solution to the origins of Hippopotamidae. This family appears to be deeply nested within the otherwise extinct artiodactyl family Anthracotheriidae, most precisely within the most advanced selenodont forms. The proposed sister group of hippos is the middle to late Miocene African semiaquatic Libycosaurus. Any close relationships of hippos with suoids, particularly with Tayassuidae, are rejected. Furthermore, the clade (Hippopotamidae, Anthracotheriidae) is proposed as the sister group of the Cetacea, offering broad morphological support for a molecular phylogeny, such support being also consistent with the fossil record. Corroboration of this relationship requires an exploration of anthracothere affinities with other Paleogene artiodactyls. Among those, the position of Ruminantia is a central question, still to be solved. Further progress in this debate is likely to come from morphological studies of paleontological data, whether known or still to be discovered.


A Hirnantian holdover from the Late Ordovician mass extinction: phylogeny and biogeography of a new anthracocrinid crinoid from Estonia

Abstract: Relatively few Hirnantian (Late Ordovician) crinoids are known, and none has been previously described from the palaeocontinent of Baltica. This has impaired our ability to understand the patterns of extinction and biogeographic dispersal surrounding the Late Ordovician mass extinction, which triggered a major turnover in crinoid faunas. Here, we describe Tallinnicrinus toomae gen. et sp. nov., an anthracocrinid diplobathrid from the Hirnantian of northern Estonia. Tallinnicrinus is the youngest member of the Anthracocrinidae and the first representative of the family to occur in Baltica. Morphologically, Tallinnicrinus is unusual in that the radial and basal plates are in a single circlet of 10 plates, similar to the anthracocrinid Rheocrinus Haugh, 1979 from the Katian of Laurentia. Phylogenetic analysis further confirms a close relationship between Tallinnicrinus and Laurentian anthracocrinids, suggesting biogeographic dispersal of the lineage from Laurentia to Baltica during the late Katian or early Hirnantian. The occurrence of this new taxon establishes that the family Anthracocrinidae survived the first pulse of the Late Ordovician mass extinction. However, the lineage remained a ‘dead clade walking’ because it failed to diversify in the wake of the end‐Katian extinction and ultimately went extinct itself by the end of the Ordovician.

ordovician mass extinction
crinoid
estonia
crinoid faunas


Alleged Cnidarian Sphenothallus in the Late Ordovician of Baltica, Its Mineral Composition and Microstructure

Abstract: Sphenothallus is a problematic fossil with possible cnidarian affinities. Two species of Sphenothallus, S. aff. longissimus and S. kukersianus, occur in the normal marine sediments of the Late Ordovician of Estonia. S. longissimus is more common than S. kukersianus and has a range from early Sandbian to middle Katian. Sphenothallus had a wide paleobiogeographic distribution in the Late Ordovician. The tubes of Sphenothallus are composed of lamellae with a homogeneous microstructure. The homogeneous microstructure could represent a diagenetic fabric, based on the similarity to diagenetic structures in Torellella (Cnidaria?, Hyolithelminthes). Tubes of Sphenothallus have an apatitic composition, but one tube contains lamellae of diagenetic calcite within the apatitic structure. Sphenothallus presumably had originally biomineralized apatitic tubes. Different lattice parameters of the apatite indicate that biomineralization systems of phosphatic cnidarians Sphenothallus and Conularia sp. may have been different.

sphenothallus
late ordovician
microstructure
apatite


Forum The Restaurant At The End Of The Universe: Modelling the colonisation of Sahul

Abstract: Abstract Elsewhere we have developed a speculative model of the early human colonisation of Sahul (Pleistocene Australia-New Guinea). Here we elaborate it, using theory from behavioural ecology, and data from palaeoclimatology and modern hunter-gatherer ethnography. We argue that colonisers focused mainly on coastal ecotones while crossing Wallacea, but spread more widely across favourable habitats after landing on Sahul. Movement was archaeologically instantaneous, driven primarily by serial depletion of high-ranked prey. Human populations subsequently remained far smaller than sometimes imagined, probably because of difficult climatic and environmental conditions. Archaeological data are generally consistent with these expectations. These findings challenge the frequent assertion that human colonisation alone led to significant changes in Sahul ecology, and may help explain the simplicity of its Pleistocene lithic technology.

colonisation
sahul
wallacea
human population


Structure of the Nasal Region of Non-Mammalian Cynodonts and Mammaliaforms: Speculations on the Evolution of Mammalian Endothermy

Abstract: ABSTRACT Nasal regions of the non-mammalian cynodonts Massetognathus, Probainognathus, and Elliotherium were reconstructed from micro-computed tomography scans and compared with scans and published accounts of more derived forms, including Brasilitherium, Morganucodon, Haldanodon, and extant mammals. The basic structure of the modern mammalian nose, already present in non-mammalian cynodonts of the Early Triassic, underwent little modification during the Triassic. A respiratory chamber opened into a nasopharyngeal passage through an enlarged primary choana bordered posteriorly by a transverse lamina that formed the floor to a more posterior olfactory chamber. Cartilaginous respiratory turbinals initially provided a surface for evaporative cooling during periods of increased activity in the exceptionally high ambient temperatures of the Triassic. A similar mechanism for heat loss is present in extant crocodilians, squamates, and mammals. In the Late Triassic and Early Jurassic non-mammaliaform cynodonts (Elliotherium) and mammaliaforms (Morganucodon), the pterygopalatine ridges behind the hard secondary palate extended ventrally and formed the lateral walls to a narrow nasopharynx, as pterygoid hamuli do in extant mammals. Ridges in this position suggest the presence of a palatopharyngeus muscle in late non-mammaliaform cynodonts that could hold the larynx in an intranarial position during rest or low activity levels to prevent inhaled air from entering the oral cavity, thus allowing cartilaginous respiratory turbinals to assume an additional role as temporal countercurrent exchange sites for heat and water conservation. Ossification of respiratory turbinals in mammals enhanced their efficiency for conserving heat and water at rest, as well as their ability to dissipate heat during thermal stress.

nasal region
mammaliaform
mammalian endothermy
morganucodon
respiratory turbinal


Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

Abstract: A decrease in the rate of cephalic shape change late in ontogeny has been documented for several species of trilobites, possibly associated with the cessation of segment release into the thorax. Qualitative descriptions of the ontogeny of Cryptolithus tesselatus Green, 1832, suggest that shape change in the cephalon was strongly influenced by the progressive accommodation of large funnel-shaped perforations (“fringepits”) over several molts. The number and arrangement of fringe-pits was established early in ontogeny, however, before thoracic segment release was completed. Due to the unusual and highly convex shape of the cephalon, we use three-dimensional (3D) geometric morphometrics to quantify shape change in this species and determine if there is a rate shift, and at what point in development this shift occurred. Three-dimensional morphometrics was made possible by extracting fixed and semi-landmarks from surface reconstructions of C. tesselatus rendered from CT scans of silicified specimens. Results show that the cephalon continued to change shape into adulthood, but that a threshold model with a rate shift associated with the cessation of new fringe-pits is best supported. 2D landmarks taken from the dorsal view fail to capture the dramatic change in convexity of the cephalon during development, but model comparison results are consistent with those based on the 3D landmark dataset, allowing comparison of this aspect of ontogenetic change with other species. Based on these comparisons, it appears that 1) trajectories are often better characterized by threshold models than simple linear regression models; 2) the timing of shifts may not be phylogeneti-


Neandertal cannibalism and Neandertal bones used as tools in Northern Europe

Abstract: Almost 150 years after the first identification of Neandertal skeletal material, the cognitive and symbolic abilities of these populations remain a subject of intense debate. We present 99 new Neandertal remains from the Troisième caverne of Goyet (Belgium) dated to 40,500–45,500 calBP. The remains were identified through a multidisciplinary study that combines morphometrics, taphonomy, stable isotopes, radiocarbon dating and genetic analyses. The Goyet Neandertal bones show distinctive anthropogenic modifications, which provides clear evidence for butchery activities as well as four bones having been used for retouching stone tools. In addition to being the first site to have yielded multiple Neandertal bones used as retouchers, Goyet not only provides the first unambiguous evidence of Neandertal cannibalism in Northern Europe, but also highlights considerable diversity in mortuary behaviour among the region’s late Neandertal population in the period immediately preceding their disappearance.

cannibalism
neandertal bone
northern europe
belgium
stable isotope


Scott Rogers on dinosaur behavior, in: The Annals of Morphology

Abstract: It is sad but true that you cannot have everything in life, a yardwithoutweeds,Utah summerswithout paperwasps, dogs without accidents, or dinosaur boneswith fossilized soft tissue. But, for just a brief moment though I thought I had one of the latter. This is a beautifully polished section of vertebral body from a dinosaur, most likely Allosaurus, from the Grand Junction, Colorado Morrison formation of the upper Jurassic, some 150million years old. To judge by its size, it was one of the last of the over 40 postsacral vertebrae of the animal lacking the dorsal portion of the medullary canal and the transverse and spinous processes. What appears at first glance to be fossilized spinal cord (some 31 mm in length are present) is nothing more than an endocast of a very fine-grained gray silt filling the medullary cavity. A 2 mm (on the average) darkercolored cortex of the endocastmayhave been themeninges, but then, wishful thinking can afflict even the toughest of old medical school professors. In any event, the minute space between the ventral surface of the endocast and dorsal rim of themedullary cavity is linedwith beautifulmicroscopic quartz crystals which also fill the cracks in the vertebral body. So, what is an endocast? For that the gracious reader is referred to the wonderful essay by Scott Rogers in this issue of the Journal. He is a fellow faculty member—Professor of Neurobiology and Anatomy at this University, birth citizen of Utah (a state with a superabundance of well-preserved fossils) whose first words could not possibly have been mamma or dadda but Campsognathus and Heterodontosaurus (with a somewhat toothless lisp).Which is to say that Dr. Rogers is not only a distinguished anatomist and neurobiologist with particular expertise in the molecular biology of addictions and the auto-immune disorders of the brain but also a phenomenal paleontologist whose reconstruction of brain endocasts of Allosaurus have indeed made it possible to infer (some of) their behaviors. It is a never-forgotten experience to be privileged to accompany Scott and his equally accomplished neurobiologist wife Lorise Gahring and their dog ‘‘Buck Rogers’’ (also a neuroscientist) on a fossil-digging field trip, for example, to the Cambrian trilobite beds of Delta, Utah. Initial attempts to relate form and function in fossils goes back to the very beginning of 19th century comparative anatomy and the pioneer paleontologists of that era [q.v. Russell, 1916]. Like them, Scott does so on the basis of two lines of evidence, namely, the structure of the part under consideration in relationship to the structure of the rest of the beast (or whatever is preserved of it), and, most importantly, and with greatest sophistication, an analysis of phylogenetic homology. In this particular case, the comparison between theAllosaurus andAlligator vestibular systems is compelling and beautifully illustrated. Thus, to some extent Scott Rogers follows in the footsteps of Cuvier [1769–1832], born a German Protestant working all of his life in Catholic France, the founder of paleozoology, most outstanding comparative anatomist ofhis day (until theadvent of theYoungerMeckel), and founder of the ‘‘law of correlation,’’ formulated as follows [Outram, 1984]. ‘‘Every living being constitutes a whole, a closed unit, in which all parts correspond to each other and contribute reciprocally to the same function. None of these parts can be changed without change in all the others; consequently, each part, taken as its own, designates and identifies all the others [Cuvier, 1812].’’ He went so far as to say, ‘‘. . .the smallest bone, plane or apophysis, relates in a definite way to the class order, species, and genus towhich it belongs, and this goes so far, that with appropriate skill, clever application of the methods of analogy [nowadays homology], and actual comparison, each well-preserved piece of a bone is capable of determining all the other parts, as if the animal were before one [Cuvier, 1842].’’ At this endeavor Cuvier was spectacularly successful, but he failed in recognizing analogy as evidence for descent, and constrained all life forms into only four embranchements immutably created by God; and he represented the present diversity of organisms as remnants of catastrophic prior extinctions reducing the full palette of life intended by God. Thus, Cuvier not only, categorically, rejected the (somewhat inchoate) ideas on descent by his in-house colleague Lamarck but, far more aggressively, those of his other, in-house coworker (and previous co-author) Etienne Geoffroy StHilaire, whose notions on homologizing the dorso-ventral axis of vertebrates and invertebrates seemed to him the apotheosis of stultitude [Appel, 1987]. No such difficulties have beset Dr. Rogers. At a time when evolutionism is not only the normal mode of western biological thinking, but the dominant mode of framing testable hypotheses about homology and development, Scott has taken advantage of the extraordinary treasure of dinosaur fossils available in this state to use the venerable methods of morphology (aided by extremely sophisticated imaging techniques) to think about dinosaur behavior. Those clinician colleagues of mine who sneer ‘‘who cares’’ about this kind of work have not learned the elementary lesson that everything that develops, whether normal or abnormal, has evolved, and that nothing can occur in development that evolution has not made possible. A lesson to be learned daily in clinic and at bedside when dealing with, for example, cleft palate, agenesis of corpus callosum, penoscrotal inversion, etc. Dinosaurs [Gr. deinos: terrible, sauros: lizard. R. Owen, 1841] evidently are members of the vertebrate class reptilia, specifically the subclass diapsida (characterized by two temporal fenestra); thus, they had a scaly skin and laid eggs with shells. This subclass is made up of two infraclasses: the archosauria (dinosaurs, sphenodontid reptiles, and crocodiles) and the lepidosauria (snakes and lizards). The two orders of *Correspondence to: John M. Opitz, 2C412 SOM, University of Utah, 50 N. Medical Drive, SLC, UT 84132. E-mail: john.opitz@hsc.utah.edu

dinosaur behavior
morphology
scott rogers


Shell bone histology indicates terrestrial palaeoecology of basal turtles

Abstract: The palaeoecology of basal turtles from the Late Triassic was classically viewed as being semi-aquatic, similar to the lifestyle of modern snapping turtles. Lately, this view was questioned based on limb bone proportions, and a terrestrial palaeoecology was suggested for the turtle stem. Here, we present independent shell bone microstructural evidence for a terrestrial habitat of the oldest and basal most well-known turtles, i.e. the Upper Triassic Proterochersis robusta and Proganochelys quenstedti. Comparison of their shell bone histology with that of extant turtles preferring either aquatic habitats or terrestrial habitats clearly reveals congruence with terrestrial turtle taxa. Similarities in the shell bones of these turtles are a diploe structure with well-developed external and internal cortices, weak vascularization of the compact bone layers and a dense nature of the interior cancellous bone with overall short trabeculae. On the other hand, ‘aquatic’ turtles tend to reduce cortical bone layers, while increasing overall vascularization of the bone tissue. In contrast to the study of limb bone proportions, the present study is independent from the uncommon preservation of appendicular skeletal elements in fossil turtles, enabling the palaeoecological study of a much broader range of incompletely known turtle taxa in the fossil record.

terrestrial palaeoecology
basal turtle
shell bone histology


Early Cretaceous "symmetrodont" mammal Gobiotheriodon from Mongolia and the classification of "Symmetrodonta"

Abstract: The "symmetrodont" mammal, Gobiotheriodon infinitus (Trofimov, 1980), from the Early Cretaceous (Aptian-Albian) of Mongolia, is redescribed. The species is restricted to the holotype only (dentary with three last molars), the referred maxillary fragment with M3? is considered here as cf. Gobiconodon sp. The dental formula of G. infinitus is reinterpreted as i1-3 c1 p1-3 m1-4. G. infinitus is characterized by a short dentary symphysis; long, well-developed Meckel's groove; small, triangular-shaped pterygoid fossa; weakly developed pterygoid crest; i3 enlarged; p1-3 two-rooted; lower molars acute-to obtuse-angled, labial cingulids lacking, lingual cingulids very short, well developed mesial and distal cingulid cuspules ("e" and "d") and prominent wear surface on the paracristid. Gobiotheriodon is similar to Tinodon (Late Jurassic, USA; Early Cretaceous, Great Britain and Portugal) in postcanine dental formula and structure of the pterygoid fossa; it is provisionally assigned to Tinodontidae Marsh, 1887. Some taxa previously assigned to (or suggested as possible relatives of) "Symmetrodonta" are reviewed. Amphidontidae Simpson, 1925 is considered as nomen dubium. A new classification for "Symmetrodonta" is proposed.

symmetrodont gobiotheriodon mongolia spalacotheriid


Phylogeny of the Notoungulata (Mammalia) based on cranial and dental characters

Abstract: The Notoungulata is the richest order of South American endemic placentals, but phylogenetic relationships within this order are unclear. This work provides short descriptions of new cranial characters useful for phylogenetic research on notoungulates, argues for a redefinition of some characters on the dental cristae, and provides a long overdue treatment of notoungulate relationships – the most complete thus far – via a cladistic phylogenetic analysis comprising 50 notoungulate genera and 133 morphological characters of the skull and teeth. The monophyly of the Notoungulata (including Pyrotherium) is well supported by numerous cranial and dental apomorphies. The validity of most traditional notoungulates suprageneric taxa is tested, and the monophyly of the two traditional notoungulate suborders Toxodontia and Typotheria is supported. These two taxa are united in a clade supported by an original character on the morphology of the ectopterygoid crests. The Henricosborniidae, Isotemnidae and Oldfieldthomasiidae are paraphyletic, reflecting the fact that these families are mostly defined by plesiomorphic characters. The monophyly of Notohippidae is questioned, as well as the possibility of a close relationship between leontiniids and toxodontids on the basis of cranial arguments. It is observed that two major subclades diverge early within the Typotheria: the Interatheriidae and the clade Archaeohyracidae + Mesotheriidae + Hegetotheriidae. This new phylogeny of the notoungulates from cranial and dental anatomy is an essential step towards reconstructing the ancestral morphotype of the Notoungulata, and is crucial for research on the origin and phylogenetic affinities of these South American ungulates within the Placentalia.

notoungulata typotheria interatheriidae phylogeny


Unveiling rare diversity by integrating museum, literature, and field data

Abstract: Abstract Estimates of taxonomic richness and abundance are complicated by sampling biases. The failure to sample rare taxa is most often attributed to inadequate sampling and to removal during the process of sample-size standardization. Here I present two methods for unveiling rare diversity by integrating species presence/absence data from museum collections and the literature with quantitative estimates of species richness and abundance gathered from field-based bulk samples. Combining museum, literature, and field data can provide a more comprehensive estimate of taxonomic richness and abundance without substantial increase in current sampling effort. First, in a given bulk sample, the lowest proportional abundance value observed can be used to estimate the maximum abundance of rare species known to have occurred at the locality at least once but not recorded in the current sample. Second, a model-selection approach can be used, in which a set of relative abundance distribution models are fit to the bulk-sample abundance data and the parameter estimates for the best model used to calculate the abundance distribution for all species known from the locality. The Paleogene marine fossil record of the U.S. Gulf Coastal Plain is suitable for applying these methods, because (1) the molluscan fauna is well represented in museum collections and the literature, (2) the molluscan fauna has been taxonomically standardized, and (3) many classic localities remain accessible for standardized bulk sampling. I introduce these methods by applying them to a single locality and then, using the faunas of the Gosport, Moodys Branch, and Red Bluff Formations, I demonstrate how the model-fitting approach can be used to compare taxonomic richness among multiple localities. A substantial fraction of the molluscan richness known from each locality is not captured in bulk samples and much of this unobserved richness may be attributed to the rarity of species. The multiple-locality comparison suggests that the greatest Paleogene decline in standing richness occurred in the middle Eocene and that the recovery of richness following the Eocene-Oligocene extinction was quite rapid despite substantial loss of taxa. These analyses underscore the magnitude of veiled diversity in marine fossil assemblages and the potential of existing sources of data to unveil rare taxa, allowing them to be incorporated into quantitative diversity studies.


Whale-fall ecosystems: recent insights into ecology, paleoecology, and evolution.

Abstract: Whale falls produce remarkable organic- and sulfide-rich habitat islands at the seafloor. The past decade has seen a dramatic increase in studies of modern and fossil whale remains, yielding exciting new insights into whale-fall ecosystems. Giant body sizes and especially high bone-lipid content allow great-whale carcasses to support a sequence of heterotrophic and chemosynthetic microbial assemblages in the energy-poor deep sea. Deep-sea metazoan communities at whale falls pass through a series of overlapping successional stages that vary with carcass size, water depth, and environmental conditions. These metazoan communities contain many new species and evolutionary novelties, including bone-eating worms and snails and a diversity of grazers on sulfur bacteria. Molecular and paleoecological studies suggest that whale falls have served as hot spots of adaptive radiation for a specialized fauna; they have also provided evolutionary stepping stones for vent and seep mussels and could have facilitated speciation in other vent/seep taxa.

habitat island
great-whale carcass
microbial assemblage
deep sea
whale-fall ecosystem


Abstract: Pecharová, M., Ren, D. & Prokop, J., 29.01.2015. A new palaeodictyopteroid (Megasecoptera: Brodiopteridae) from the Early Pennsylvanian of northern China reveals unique morphological traits and intra-specific variability. Alcheringa 39, XXX–XXX. ISSN 0311-5518 Evaluation of abundant insect fossils from the Early Pennsylvanian (Namurian) Tupo Formation of northern China (Xiaheyan locality, Ningxia Hui Autonomous Region) enabled description of a new megasecopteran, i.e., Brodioptera sinensis sp. nov. and emendation of Brodiopteridae. Brodioptera sinensis is defined principally on wing venation characters and darkly pigmented wing apices, but a few have hyaline wing membranes possibly reflecting freshly emerged imagoes or subimagoes without fully developed coloration. The large assemblage of 54 specimens enabled documentation of intra-specific variability in wing venation. In addition, the new species reveals the detailed morphology of the haustellate mouthparts with conspicuous elongated stylets, and external copulatory organs that, previously, were poorly documented or unknown. The male and female external genitalia are similar to members of Protohymenidae (Megasecoptera) and Asthenohymenidae (Diaphanopterodea). Brodioptera sinensis is related to Brodioptera stricklani and Brodioptera cumberlandensis both known from localities in Euramerica suggesting faunal exchange occurred during the Bashkirian. Moreover, based on our analysis of veinal characters and re-examination of the holotype of Sylvohymen pintoi Brauckmann known from Namurian of Hagen-Vorhalle (Germany), we propose transferring this taxon to Brodiopteridae as Brodioptera pintoi comb. nov. Despite the different palaeoclimatic conditions in Euroamerica and Gondwanaland, we assume that Brodiopteridae are closely related to Xenopteridae (type genus: Xenoptera) known solely from South America because these groups have similar venation patterns and were contemporaneous. Martina Pecharová [martina.pecharova@natur.cuni.cz] Charles University in Prague, Faculty of Science, Department of Zoology, Viničná 7, CZ-128 44, Praha 2, Czech Republic; Dong Ren [rendong@mail.cnu.edu.cn] Key Lab of Insect Evolution & Environmental Changes, College of Life Science, Capital Normal University, Beijing 100048, PR China; Jakub Prokop [jprokop@natur.cuni.cz] Charles University in Prague, Faculty of Science, Department of Zoology, Viničná 7, CZ-128 44, Praha 2, Czech Republic.

new palaeodictyopteroid
brodiopteridae
unique morphological trait


Morphological Evolution Is Accelerated among Island Mammals

Abstract: Dramatic evolutionary changes occur in species isolated on islands, but it is not known if the rate of evolution is accelerated on islands relative to the mainland. Based on an extensive review of the literature, I used the fossil record combined with data from living species to test the hypothesis of an accelerated morphological evolution among island mammals. I demonstrate that rates of morphological evolution are significantly greater—up to a factor of 3.1—for islands than for mainland mammal populations. The tendency for faster evolution on islands holds over relatively short time scales—from a few decades up to several thousands of years—but not over larger ones—up to 12 million y. These analyses form the first empirical test of the long held supposition of accelerated evolution among island mammals. Moreover, this result shows that mammal species have the intrinsic capacity to evolve faster when confronted with a rapid change in their environment. This finding is relevant to our understanding of species' responses to isolation and destruction of natural habitats within the current context of rapid climate warming.

mainland
literature
environment
morphological evolution


Ecological interactions on macroevolutionary time scales: clams and brachiopods are more than ships that pass in the night.

Abstract: Competition among organisms has ecological and evolutionary consequences. However, whether the consequences of competition are manifested and measureable on macroevolutionary time scales is equivocal. Marine bivalves and brachiopods have overlapping niches such that competition for food and space may occur. Moreover, there is a long-standing debate over whether bivalves outcompeted brachiopods evolutionarily, because brachiopod diversity declined through time while bivalve diversity increased. To answer this question, we estimate the origination and extinction dynamics of fossil marine bivalve and brachiopod genera from the Ordovician through to the Recent while simultaneously accounting for incomplete sampling. Then, using stochastic differential equations, we assess statistical relationships among diversification and sampling dynamics of brachiopods and bivalves and five paleoenvironmental proxies. None of these potential environmental drivers had any detectable influence on brachiopod or bivalve diversification. In contrast, elevated bivalve extinction rates causally increased brachiopod origination rates, suggesting that bivalves have suppressed brachiopod evolution.

macroevolutionary time scale
brachiopod
bivalve
extinction rate
ecological interaction


Using paleo-archives to safeguard biodiversity under climate change

Abstract: Using the past to inform the future The late Quaternary paleorecord, within the past ∼130,000 years, can help to inform present-day management of the Earth's ecosystems and biota under climate change. Fordham et al. review when and where rapid climate transitions can be found in the paleoclimate record. They show how such events in Earth's history can shape our understanding of the consequences of future global warming, including rates of biodiversity loss, changes in ecosystem structure and function, and degradation in the goods and services that these ecosystems provide to humanity. They also highlight how recent developments at the intersection of paleoecology, paleoclimatology, and macroecology can provide opportunities to anticipate and manage the responses of species and ecosystems to changing climates in the Anthropocene. Science, this issue p. eabc5654 BACKGROUND Effects of recent global warming have been documented in every biome on Earth. Safeguarding biodiversity and ecosystem services against future impacts requires reliable predictions of climate-driven biological responses and effective solutions. Integrated research in paleoecology, paleogenomics, paleoclimatology, and macroecology offers new prospects for projecting and managing current biotic responses to climate change. By revealing mechanisms that shaped past and present biodiversity patterns, this interdisciplinary intersection provides an empirical foundation for anticipating responses to accelerated climate change. New insights are coming from developments in high-throughput sequencing, computational technologies, ecological simulation models, and increased spatiotemporal resolution of paleoenvironmental data from late Quaternary paleo-records (the past ~130,000 years). Although these advances reveal biodiversity responses to past global change, benefits for improving forecasting of biodiversity impacts and refining conservation policies are lagging. Abundant opportunities exist for using the late Quaternary paleo-record to inform conservation practices and policies in the context of climate change. ADVANCES The threat of anthropogenic climate change demands that conservationists seek more effective ways of improving management of biodiversity and ecosystems. Analytical approaches that combine high-resolution paleoclimate proxy and simulation data, precisely dated fossils, and genetic diversity estimates from ancient DNA are unveiling biotic responses to various rates and magnitudes of natural climate warming, some comparable with 21st century projections. Reference periods in Earth’s history provide natural laboratories for testing fundamental ecological theory and offer opportunities to identify ecological processes that influence the likelihood of extinction and ecosystem change, to test efficacy of threatened-species assessments and resilience of biota during periods of abrupt warming, and to locate biogeographic areas that remain stable under shifting climates. Refinement of essential biodiversity variables by using past biodiversity dynamics will improve our understanding of climate-driven shifts in species populations, community composition, and ecosystem structure and function. From this, biodiversity early-warning systems, conservation strategies, and decision-making tools can be tested at fine-grain spatiotemporal scales, providing an evidence base for understanding and improving projections of species- and ecosystem-level collapse. OUTLOOK As paleo-archives become more routinely integrated into conservation science, guidelines for the management of nature will benefit from understanding how different spatiotemporal scales of past climate change affected species and ecosystems across the planet. This will require global initiatives to harmonize vast numbers of paleoclimate-proxy and paleoecological records with high-resolution paleoclimate projections from Earth system models. Paleoecological data offer a means to disentangle climate and nonclimate drivers of biodiversity and ecosystem function, particularly in concert with simulation models and integrated analytical techniques that compare biotic change across regions with contrasting histories of human colonization and land use. Moreover, developments in paleogenomics that pinpoint adaptation across and within species will identify microevolutionary processes that lend resilience to biodiversity in shifting climates. Incorporating paleo-archives in conservation policies will equip decision-makers with improved strategies for mitigating biodiversity loss from climate change in the Anthropocene. Paleo-archives offer new prospects for benchmarking and maintaining future biodiversity. Integrated research using paleo-archives provides empirical foundations for contextualizing climate-driven changes in species populations, community composition, and ecosystem structure and function. These observations can inform conservation strategies under anthropogenic climate change. CREDITS: HUNG CHUNG CHIH, WANG LIQIANG, ANDREI STEPANOV, AUSTRALIANCAMERA, ALHOVIK, BLUERING MEDIA, NAZARII M, ANDERS SVENSSON/ SHUTTERSTOCK Strategies for 21st-century environmental management and conservation under global change require a strong understanding of the biological mechanisms that mediate responses to climate- and human-driven change to successfully mitigate range contractions, extinctions, and the degradation of ecosystem services. Biodiversity responses to past rapid warming events can be followed in situ and over extended periods, using cross-disciplinary approaches that provide cost-effective and scalable information for species’ conservation and the maintenance of resilient ecosystems in many bioregions. Beyond the intrinsic knowledge gain such integrative research will increasingly provide the context, tools, and relevant case studies to assist in mitigating climate-driven biodiversity losses in the 21st century and beyond.

paleo-archive
biodiversity
climate change


Freshwater input and abrupt deglacial climate change in the North Atlantic

Abstract:
Greenland ice-core records indicate that the last deglaciation (~7 - 21 ka) was punctuated by numerous abrupt climate reversals, involving temperature changes
of up to 5-10oC within decades. However the cause behind many of these events is uncertain. A likely candidate may have been the input of deglacial meltwater, from the Laurentide ice sheet (LIS), to the high latitude North Atlantic, which disrupted ocean circulation and triggered cooling. Yet the direct evidence of meltwater input for many of these event has so far remained undetected. In this study, we use the geochemistry (paired Mg/Ca-δ18
O) of planktonic foraminifera from a sediment core south of Iceland to reconstruct the input of freshwater to the
northern North Atlantic during abrupt deglacial climate change. Our record can be placed on the same timescale as ice-cores and therefore provides a direct comparison between the timing of freshwater input and climate variability. Meltwater events coincide with the onset of numerous cold intervals, including the Older Dryas (14.0 ka), two events during the Allerod (at ~13.1 and 13.6 ka), the Younger Dryas (12.9 ka), and the 8.2 ka event, supporting a causal link between these abrupt climate changes and meltwater input. During the Bolling-Allerod
warm interval, we find that periods of warming are associated with an increased meltwater flux to the northern North Atlantic, which in turn induces abrupt cooling, a cessation in meltwater input, and eventual climate recovery. This implies that feedback between climate and meltwater input produced a highly variable climate. A comparison to published data sets suggests that this feedback likely included fluctuations in the southern margin of the LIS causing rerouting of LIS meltwater between southern and eastern drainage outlets, as proposed by Clark et al. [Science, 2001, v293, 283-287].

deglacial climate change
north atlantic
freshwater input


Bone Surface Modifications, Reasonable Certainty, and Human Antiquity in the Americas: The Case of the Arroyo Del Vizcaίno Site

Abstract: Abstract Modifications on bone surfaces are taphonomic features that allow, among other aspects of environmental reconstruction, the assessment of human presence. The agents that cause such marks are diverse and of both biotic and abiotic origin. Among the former, marks made by human tools are of paramount importance for archaeologists and paleontologists to identify. Although it is possible to erroneously assign trampling marks to cut marks, several criteria have been recently developed so as to avoid such risks. These methods are applied here to the 30,000-year-old site of Arroyo del Vizcaíno (Uruguay), where over one thousand megafaunal remains have been collected. Some of them show marks that have been interpreted to be the result of the action of human tools. Using a database built up from previous studies of experimentally made marks as an actualistic model, it was concluded that the marks in the Arroyo del Vizcaíno site are unlikely to have been made by trampling, hence leaving human agency as the most feasible cause. This has important consequences for the debate on the human peopling of the Americas and on the process of extinction of the Pleistocene megafauna.


Inferences of Diplodocoid (Sauropoda: Dinosauria) Feeding Behavior from Snout Shape and Microwear Analyses

Abstract: Background As gigantic herbivores, sauropod dinosaurs were among the most important members of Mesozoic communities. Understanding their ecology is fundamental to developing a complete picture of Jurassic and Cretaceous food webs. One group of sauropods in particular, Diplodocoidea, has long been a source of debate with regard to what and how they ate. Because of their long lineage duration (Late Jurassic-Late Cretaceous) and cosmopolitan distribution, diplodocoids formed important parts of multiple ecosystems. Additionally, fortuitous preservation of a large proportion of cranial elements makes them an ideal clade in which to examine feeding behavior. Methodology/Principal Findings Hypotheses of various browsing behaviors (selective and nonselective browsing at ground-height, mid-height, or in the upper canopy) were examined using snout shape (square vs. round) and dental microwear. The square snouts, large proportion of pits, and fine subparallel scratches in Apatosaurus, Diplodocus, Nigersaurus, and Rebbachisaurus suggest ground-height nonselective browsing; the narrow snouts of Dicraeosaurus, Suuwassea, and Tornieria and the coarse scratches and gouges on the teeth of Dicraeosaurus suggest mid-height selective browsing in those taxa. Comparison with outgroups (Camarasaurus and Brachiosaurus) reinforces the inferences of ground- and mid-height browsing and the existence of both non-selective and selective browsing behaviors in diplodocoids. Conclusions/Significance These results reaffirm previous work suggesting the presence of diverse feeding strategies in sauropods and provide solid evidence for two different feeding behaviors in Diplodocoidea. These feeding behaviors can subsequently be tied to paleoecology, such that non-selective, ground-height behaviors are restricted to open, savanna-type environments. Selective browsing behaviors are known from multiple sauropod clades and were practiced in multiple environments.

diplodocoid
behavior
snout shape
sauropod
ecosystem


Cancellous bone and theropod dinosaur locomotion. Part II—a new approach to inferring posture and locomotor biomechanics in extinct tetrapod vertebrates

Abstract: This paper is the second of a three-part series that investigates the architecture of cancellous bone in the main hindlimb bones of theropod dinosaurs, and uses cancellous bone architectural patterns to infer locomotor biomechanics in extinct non-avian species. Cancellous bone is widely known to be highly sensitive to its mechanical environment, and therefore has the potential to provide insight into locomotor biomechanics in extinct tetrapod vertebrates such as dinosaurs. Here in Part II, a new biomechanical modelling approach is outlined, one which mechanistically links cancellous bone architectural patterns with three-dimensional musculoskeletal and finite element modelling of the hindlimb. In particular, the architecture of cancellous bone is used to derive a single ‘characteristic posture’ for a given species—one in which bone continuum-level principal stresses best align with cancellous bone fabric—and thereby clarify hindlimb locomotor biomechanics. The quasi-static approach was validated for an extant theropod, the chicken, and is shown to provide a good estimate of limb posture at around mid-stance. It also provides reasonable predictions of bone loading mechanics, especially for the proximal hindlimb, and also provides a broadly accurate assessment of muscle recruitment insofar as limb stabilization is concerned. In addition to being useful for better understanding locomotor biomechanics in extant species, the approach hence provides a new avenue by which to analyse, test and refine palaeobiomechanical hypotheses, not just for extinct theropods, but potentially many other extinct tetrapod groups as well.

locomotor biomechanic
tetrapod vertebrate
cancellous bone


Cats in the forest: predicting habitat adaptations from humerus morphometry in extant and fossil Felidae (Carnivora)

Abstract: Abstract Mammalian carnivores are rarely incorporated in paleoenvironmental reconstructions, largely because of their rarity within the fossil record. However, multivariate statistical modeling can be successfully used to quantify specific anatomical features as environmental predictors. Here we explore morphological variability of the humerus in a closely related group of predators (Felidae) to investigate the relationship between morphometric descriptors and habitat categories. We analyze linear measurements of the humerus in three different morphometric combinations (log-transformed, size-free, and ratio), and explore four distinct ways of categorizing habitat adaptations. Open, Mixed, and Closed categories are defined according to criteria based on traditional descriptions of species, distributions, and biome occupancy. Extensive exploratory work is presented using linear discriminant analyses and several fossils are included to provide paleoecological reconstructions. We found no significant differences in the predictive power of distinct morphometric descriptors or habitat criteria, although sample splitting into small and large cat guilds greatly improves the stability of the models. Significant insights emerge for three long-canine cats: Smilodon populator, Paramachairodus orientalis, and Dinofelis sp. from Olduvai Gorge (East Africa). S. populator and P. orientalis are both predicted to have been closed-habitat adapted taxa. The false “sabertooth” Dinofelis sp. from Olduvai Gorge is predicted to be adapted to mixed habitat. The application of felid humerus ecomorphology to the carnivoran record of Olduvai Gorge shows that the older stratigraphic levels (Bed I, 1.99–1.79 Ma) included a broader range of environments than Beds II or V, where there is an abundance of cats adapted to open environments.

habitat adaptation
felidae
mammalian carnivore
morphological variability
cat


Devonian actinopterygian phylogeny and evolution based on a redescription of Stegotrachelus finlayi

Abstract: Basal actinopterygian phylogeny is in a state of flux. Discoveries of new Devonian and Carboniferous taxa have not only contributed to our knowledge of these animals, but have also complicated our understanding of their interrelationships. Over the preceding 50 years, there have been several new discoveries and redescriptions of early actinopterygians; however, Tegeolepis clarki, Kentuckia hlavini, and Stegotrachelus finlayi have never been fully redescribed. Although previous authors have re-examined the skull of S. finlayi, new material has recently been collected, in 1973 and 2002. This study synthesizes information from original and new material to fully redescribe S. finlayi, and incorporates these data into a cladistic analysis that examines the interrelationships of early actinopterygians. Phylogenetic systematic data returned support for a monophyletic Stegotrachelidae – an evolutionary systematic hypothesis generated over 40 years ago. Previous palaeoenvironmental and biogeographic hypotheses were tested, with results supporting the independent freshwater origins of several Devonian actinopts, although a regional endemic grade of Gondwanan taxa is not confirmed.

actinopterygian phylogeny
redescription
stegotrachelus finlayi


The Ontogenetic Method for Determining Character Polarity and its Relevance to Phylogenetic Systematics

Abstract: In an attempt to clarify the relevance of ontogenetic transformations for system atics, the ontogenetic method for determining character polarity (the biogenetic law of Nelson, 1978) is analyzed from the perspective of phylogenetic systematics. In phylogenetic systematics, as defined here, the relationships sought are those of common ancestry and, thus, the concept of phylogeny is taken as an axiom from which systematic methods are deduced. This perspective has a number of consequences concerning the role of ontogenetic transformations in system atics, among which are the following: (1) Von Baer's second law, which states that less general characters are developed from the most general, is not universally true. (2) The validity of Nelson's biogenetic law (not to be confused with other concepts of similar name) does not depend on the validity of von Baer's law. (3) As a theory about the relationship between on togeny and phylogeny, Nelson's biogenetic law can only be tested by known character phylog enies. However, outgroup, paleontological, and ontogenetic methods of polarity determination need not be interpreted as scientific theories; instead, they can be interpreted as theorems deduced from the axiom of phylogeny and certain auxiliary assumptions. (4) The usefulness of the ontogenetic method rests on an assumption of ancestral character retention. If ancestral characters are retained in descendant ontogenies, then ancestral characters will be more general than their phylogenetic derivatives. (5) The sequence of ontogenetic transformation is irrelevant to the usefulness of the ontogenetic method; generality is the critical factor. (6) An "ontoge netic" method based on generality may be useful for determining evolutionary polarity when characters are instantaneous morphologies, but ontogenetic transformations rather than instan taneous morphologies are more appropriately considered characters when attempting to deter mine phylogenetic relationships among organisms. When ontogenetic transformations are viewed as characters, there can be no ontogenetic method for determining evolutionary character po larity; however, the comparative phylogenetic method properly involves a comparison of on togenetic transformations. (7) Ontogenetic polarities are different than phylogenetic polarities; the two have the relationship of part to whole, respectively. (8) For characters that exhibit ontogenetic transformation, homology is distinct from synapomorphy. (9) Finally, there is no threefold parallelism in phylogenetic systematics. Comparative anatomy, paleontology, and em bryology are not three separate disciplines within systematics; rather, the three form a single comparative method unified in the organism by the concept of evolution. (Biogenetic law; von Baer's law; cladistics; character; evolution; generality; homology; ontogenetic method; ontogeny; outgroup method; paedomorphosis; parsimony; paleontological method; phylogenetic system atics; phylogeny; polarity; semaphoront; synapomorphy; threefold parallelism.)

ontogenetic method
relevance
phylogenetic systematic


Diversity and disparity of sparassodonts (Metatheria) reveal non-analogue nature of ancient South American mammalian carnivore guilds

Abstract: This study investigates whether terrestrial mammalian carnivore guilds of ancient South America, which developed in relative isolation, were similar to those of other continents. We do so through analyses of clade diversification, ecomorphology and guild structure in the Sparassodonta, metatherians that were the predominant mammalian carnivores of pre-Pleistocene South America. Body mass and 16 characters of the dentition are used to quantify morphological diversity (disparity) in sparassodonts and to compare them to extant marsupial and placental carnivores and extinct North American carnivoramorphans. We also compare trophic diversity of the Early Miocene terrestrial carnivore guild of Santa Cruz, Argentina to that of 14 modern and fossil guilds from other continents. We find that sparassodonts had comparatively low ecomorphological disparity throughout their history and that South American carnivore palaeoguilds, as represented by that of Santa Cruz, Argentina, were unlike modern or fossil carnivore guilds of other continents in their lack of mesocarnivores and hypocarnivores. Our results add to a growing body of evidence highlighting non-analogue aspects of extinct South American mammals and illustrate the dramatic effects that historical contingency can have on the evolution of mammalian palaeocommunities.

sparassodont
mammalian carnivore guild
metatherian
body mass


Neurotrichus skoczeni, New Name for Neurotrichus minor Skoczen, 1993, Preoccupied

Abstract: Skoczen (1993) described the fossil shrew-mole Neurotrichus minor on the basis of an Ml and a humerus from the Pliocene (MN 15/16) Polish locality of Weze 2. Popov (2004) has since transferred this species to Quyania, but Rzebik-Kowalska (2005) retained it in Neurotrichus. However, Dalquest and Burgner (1941) had already described the extant subspecies Neurotrichus gihhsii minor from western Washington; this form is still consid ered a valid subspecies found in coastal Washington and nearby British Columbia (Carraway and Verts, 1991; Hutterer, 2005). Regardless of the generic placement of N. minor Skoczen, the name is a primary homonym and permanently invalid (ICZN 1999:art. 57.2). Therefore, I propose the replacement name Neu rotrichus skoczeni, new name, for Neurotrichus minor Skoczen, 1993, preoccupied by Neurotrichus gibbsii minor Dalquest and Burgner, 1941. The specific name honors Stanislaw Skoczen, the original describer of the species, who passed away in 2007. The diagnosis, type locality, and holotype are as given by Skoczen (1993). I discovered the homonymy during work on the Neogene Old World (NOW) paleontological database.


Global change across the Oligocene-Miocene transition : High-resolution stable isotope records from IODP Site U1334 (equatorial Pacific Ocean)

Abstract: The Oligocene-Miocene transition (OMT) (~23?Ma) is interpreted as a transient global cooling event, associated with a large-scale Antarctic ice sheet expansion. Here we present a 2.23?Myr long high-resolution (~3?kyr) benthic foraminiferal oxygen and carbon isotope (?18O and ?13C) record from Integrated Ocean Drilling Program Site U1334 (eastern equatorial Pacific Ocean), covering the interval from 21.91 to 24.14?Ma. To date, five other high-resolution benthic foraminiferal stable isotope stratigraphies across this time interval have been published, showing a ~1‰ increase in benthic foraminiferal ?18O across the OMT. However, these records are still few and spatially limited and no clear understanding exists of the global versus local imprints. We show that trends and the amplitudes of change are similar at Site U1334 as in other high-resolution stable isotope records, suggesting that these represent global deep water signals. We create a benthic foraminiferal stable isotope stack across the OMT by combining Site U1334 with records from ODP Sites 926, 929, 1090, 1264, and 1218 to best approximate the global signal. We find that isotopic gradients between sites indicate interbasinal and intrabasinal variabilities in deep water masses and, in particular, note an offset between the equatorial Atlantic and the equatorial Pacific, suggesting that a distinct temperature gradient was present during the OMT between these deep water masses at low latitudes. A convergence in the ?18O values between infaunal and epifaunal species occurs between 22.8 and 23.2?Ma, associated with the maximum ?18O excursion at the OMT, suggesting climatic changes associated with the OMT had an effect on interspecies offsets of benthic foraminifera. Our data indicate a maximum glacioeustatic sea level change of ~50?m across the OMT.

oligocene-miocene transition
stable isotope record
equatorial pacific ocean


OSL and AMS 14C Age of the Most Complete Mammoth Fossil Skeleton from Northeastern China and its Paleoclimate Significance

Abstract: ABSTRACT Applying radiocarbon (14C) dating using accelerator mass spectrometry (AMS) to the skeleton of a mammoth and the associated plant remains have been dated. The fossil of Zhalai Nur mammoth was dated to 43,500 +1000/–900 14C yr BP. The results of optically stimulated luminescence (OSL) dating, which show that a fluvially deposited gravel layer, from that the mammoth fossils were excavated, formed between 51,300±2100 and 26,600±1200 yr BP, place the new AMS 14C dates in a well-developed chronological framework. Through this study, it can be summarized that, firstly, using suitable sample material, it is possible to obtain reliable AMS 14C results, even when the ages of the target materials approach the upper limits of the method. Second, it reveals that a depositional hiatus exists during the Late Pleistocene, between ca. 26,000 yr BP and ca. 13,000 yr BP. Finally, large rivers and widely distributed areas of alluvial-fluvial deposits existed in this present-day desert area between ca. 51,000 and 26,000 yr BP. These results may shed new light on the study of the Mammuthus-Colelodonta-Bubalus fauna, the most important and fully developed fauna during the Late Pleistocene in northeastern China. They also deepen our understanding about the eco-environments of the region.


Factors controlling the depth habitat of planktonic foraminifera in the subtropical eastern North Atlantic

Abstract: Abstract. Planktonic foraminifera preserved in marine sediments archive the physical and chemical conditions under which they built their shells. To interpret the paleoceanographic information contained in fossil foraminifera, the recorded proxy signals have to be attributed to the habitat and life cycle characteristics of individual species. Much of our knowledge on habitat depth is based on indirect methods, which reconstruct the depth at which the largest portion of the shell has been calcified. However, habitat depth can be best studied by direct observations in stratified plankton nets. Here we present a synthesis of living planktonic foraminifera abundance data in vertically resolved plankton net hauls taken in the eastern North Atlantic during 12 oceanographic campaigns between 1995 and 2012. Live (cytoplasm-bearing) specimens were counted for each depth interval and the vertical habitat at each station was expressed as average living depth (ALD). This allows us to differentiate species showing an ALD consistently in the upper 100 m (e.g., Globigerinoides ruber white and pink), indicating a shallow habitat; species occurring from the surface to the subsurface (e.g., Globigerina bulloides, Globorotalia inflata, Globorotalia truncatulinoides); and species inhabiting the subsurface (e.g., Globorotalia scitula and Globorotalia hirsuta). For 17 species with variable ALD, we assessed whether their depth habitat at a given station could be predicted by mixed layer (ML) depth, temperature in the ML and chlorophyll a concentration in the ML. The influence of seasonal and lunar cycle on the depth habitat was also tested using periodic regression. In 11 out of the 17 tested species, ALD variation appears to have a predictable component. All of the tested parameters were significant in at least one case, with both seasonal and lunar cyclicity as well as the environmental parameters explaining up to > 50 % of the variance. Thus, G. truncatulinoides, G. hirsuta and G. scitula appear to descend in the water column towards the summer, whereas populations of Trilobatus sacculifer appear to descend in the water column towards the new moon. In all other species, properties of the mixed layer explained more of the observed variance than the periodic models. Chlorophyll a concentration seems least important for ALD, whilst shoaling of the habitat with deepening of the ML is observed most frequently. We observe both shoaling and deepening of species habitat with increasing temperature. Further, we observe that temperature and seawater density at the depth of the ALD were not equally variable among the studied species, and their variability showed no consistent relationship with depth habitat. According to our results, depth habitat of individual species changes in response to different environmental and ontogenetic factors and consequently planktonic foraminifera exhibit not only species-specific mean habitat depths but also species-specific changes in habitat depth.

depth habitat
planktonic foraminifera
eastern north atlantic


The Endocranial Anatomy of Therizinosauria and Its Implications for Sensory and Cognitive Function

Abstract: Background Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare. Methodology/Principal Findings Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon. Conclusion/Significance This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaurians had developed the neural pathways for a well developed sensory repertoire. In particular olfaction and hearing may have played an important role in foraging, predator evasion, and/or social complexity.

endocranial anatomy
anatomy
therizinosauria
theropod
labyrinth


Diabloroter bolti, a short-bodied recumbirostran ‘microsaur’ from the Francis Creek Shale, Mazon Creek, Illinois

Abstract: The Carboniferous (Pennsylvanian; 309–307 Mya) ‘Mazon Creek’ Lagerstätte produces some of the earliest tetrapod fossils of major Palaeozoic lineages. Previously, the Mazon Creek record of ‘microsaurs’ was known from a single specimen. However, the lack of key anatomy, such as the skull, precluded a confident taxonomic assignment, thus only a suggested affinity to the microbrachimorph ‘microsaur’ Hyloplesion was determined. Recently several new tetrapod specimens collected from Mazon Creek have come to light, of which some have recumbirostran ‘microsaur’ affinity. Here we describe a new genus and species of short-bodied recumbirostran, Diabloroter bolti, on the basis of a unique combination of autapomorphies. Both parsimony and Bayesian phylogenetic methods recover the new taxon in the Brachystelechidae clade, as sister to a clade including Carrolla and Batropetes. We determine Diabloroter to be the earliest known member of Brachytelechidae and thus establishing a Carboniferous origin of the family. We also provide an updated diagnosis for Brachystelechidae. Finally, we comment on the evolutionary trends in the clade, including dental adaptations for a proposed algivorous diet in derived clade members.

short-bodied recumbirostran
recumbirostran
microsaur
tetrapod fossil


Sulci 3D mapping from human cranial endocasts: A powerful tool to study hominin brain evolution

Abstract: Key questions in paleoneurology concern the timing and emergence of derived cerebral features within the human lineage. Endocasts are replicas of the internal table of the bony braincase that are widely used in paleoneurology as a proxy for reconstructing a timeline for hominin brain evolution in the fossil record. The accurate identification of cerebral sulci imprints in endocasts is critical for assessing the topographic extension and structural organisation of cortical regions in fossil hominins. High‐resolution imaging techniques combined with established methods based on population‐specific brain atlases offer new opportunities for tracking detailed endocranial characteristics. This study provides the first documentation of sulcal pattern imprints from the superolateral surface of the cerebrum using a population‐based atlas technique on extant human endocasts. Human crania from the Pretoria Bone Collection (South Africa) were scanned using micro‐CT. Endocasts were virtually extracted, and sulci were automatically detected and manually labelled. A density map method was applied to project all the labels onto an averaged endocast to visualise the mean distribution of each identified sulcal imprint. This method allowed for the visualisation of inter‐individual variation of sulcal imprints, for example, frontal lobe sulci, correlating with previous brain‐MRI studies and for the first time the extensive overlapping of imprints in historically debated areas of the endocast (e.g. occipital lobe). In providing an innovative, non‐invasive, observer‐independent method to investigate human endocranial structural organisation, our analytical protocol introduces a promising perspective for future research in paleoneurology and for discussing critical hypotheses on the evolution of cognitive abilities among hominins.


A geochemical study of the Ediacaran discoidal fossil Aspidella preserved in limestones: Implications for its taphonomy and paleoecology

Abstract: The Ediacara biota features the rise of macroscopic complex life immediately before the Cambrian explosion. One of the most abundant and widely distributed elements of the Ediacara biota is the discoidal fossil Aspidella, which is interpreted as a subsurface holdfast possibly anchoring a frondose epibenthic organism. It is a morphologically simple fossil preserved mainly in siliciclastic rocks, which are unsuitable for comprehensive stable isotope geochemical analyses to decipher its taphonomy and paleoecology. In this regard, three‐dimensionally preserved Aspidella fossils from upper Ediacaran limestones of the Khatyspyt Formation in the Olenek Uplift of northern Siberia offer a rare opportunity to leverage geochemistry for insights into their taphonomy and paleoecology. To take advantage of this opportunity, we analyzed δ13Ccarb, δ18Ocarb, δ13Corg, δ34Spyr, and iron speciation of the Khatyspyt Aspidella fossils and surrounding sediment matrix in order to investigate whether they hosted microbial symbionts, how they were fossilized, and the redox conditions of their ecological environments. Aspidella holdfasts and surrounding sediment matrix show indistinguishable δ13Corg values, suggesting they did not host and derive significant amount of nutrients from microbial symbionts such as methanogens, methylotrophs, or sulfide‐oxidizing bacteria. δ13Ccarb, δ18Ocarb, and δ34Spyr data, along with petrographic observations, suggest that microbial sulfate reduction facilitated the preservation of Aspidella by promoting early authigenic calcite cementation in the holdfasts before matrix cementation and sediment compaction. Iron speciation data are equivocal, largely because of the low total iron concentrations. However, consideration of published sulfur isotope and biomarker data suggests that Aspidella likely lived in non‐euxinic waters. It is possible that Aspidella was an opportunistic organism, colonizing the seafloor in large numbers when paleoenvironments were favorable. This study demonstrates that geochemical data of Ediacaran fossils preserved in limestones can offer important insights into the taphonomy and paleoecology of these enigmatic organisms living on the eve of the Cambrian explosion.


Sum things are not what they seem: Problems with point-wise interpretations and quantitative analyses of proxies based on aggregated radiocarbon dates

Abstract: Radiocarbon-date assemblages are commonly used as proxies for past human and environmental phenomena. Prominent examples of target phenomena include past population levels and sea level fluctuations. These processes are thought to have affected the amount of organic carbon deposited into the archaeological and/or palaeoenvironmental record. Time-series representing through-time fluctuations in the frequency of radiocarbon samples are, therefore, often used as proxies for such processes. However, there are critical problems with using radiocarbon “dates-as-data” in point-wise comparisons and these problems have gone largely underappreciated. The key problem is that the established proxies are easily misinterpreted. They conflate process variation and chronological uncertainty, which makes them unsuitable for point-wise comparisons aimed at identifying rates of change, comparing variables directly, or estimating parameters in regression models. Here we explore the interpretive and analytical problems in detail in an effort to raise awareness and promote skepticism about the use of the established proxies in point-wise comparisons. We also provide suggestions for future research and point to potential methodological alternatives that may improve the viability of dates-as-data approaches.

problem
process variation
chronological uncertainty


Using Phylogenomic Data to Explore the Effects of Relaxed Clocks and Calibration Strategies on Divergence Time Estimation: Primates as a Test Case

Abstract: Primates have long been a test case for the development of phylogenetic methods for divergence time estimation. Despite a large number of studies, however, the timing of origination of crown Primates relative to the K-Pg boundary and the timing of diversification of the main crown groups remain controversial. Here we analysed a dataset of 372 taxa (367 Primates and 5 outgroups, 61 thousand base pairs) that includes nine complete primate genomes (3.4 million base pairs). We systematically explore the effect of different interpretations of fossil calibrations and molecular clock models on primate divergence time estimates. We find that even small differences in the construction of fossil calibrations can have a noticeable impact on estimated divergence times, especially for the oldest nodes in the tree. Notably, choice of molecular rate model (auto-correlated or independently distributed rates) has an especially strong effect on estimated times, with the independent rates model producing considerably more ancient estimates for the deeper nodes in the phylogeny. We implement thermodynamic integration, combined with Gaussian quadrature, in the program MCMCTree, and use it to calculate Bayes factors for clock models. Bayesian model selection indicates that the auto-correlated rates model fits the primate data substantially better, and we conclude that time estimates under this model should be preferred. We show that for eight core nodes in the phylogeny, uncertainty in time estimates is close to the theoretical limit imposed by fossil uncertainties. Thus, these estimates are unlikely to be improved by collecting additional molecular sequence data. All analyses place the origin of Primates close to the K-Pg boundary, either in the Cretaceous or straddling the boundary into the Palaeogene.

divergence time estimation
primate
test case
fossil calibration
node


An exceptionally well-preserved skeleton of Thomashuxleya externa (Mammalia, Notoungulata), from the Eocene of Patagonia, Argentina

Abstract: We describe one of the oldest notoungulate skeletons with associated craniodental and postcranial elements: Thomashuxleya externa (Isotemnidae) from Canadon Vaca in Patagonia, Argentina (Vacan subage of the Casamayoran SALMA, middle Eocene). We provide body mass estimates given by different elements of the skeleton, describe the bone histology, and study its phylogenetic position. We note differences in the scapulae, humerii, ulnae, and radii of the new specimen in comparison with other specimens previously referred to this taxon. We estimate a body mass of 84 ± 24.2 kg, showing that notoungulates had acquired a large body mass by the middle Eocene. Bone histology shows that the new specimen was skeletally mature. The new material supports the placement of Thomashuxleya as an early, divergent member of Toxodontia. Among placentals, our phylogenetic analysis of a combined DNA, collagen, and morphology matrix favor only a limited number of possible phylogenetic relationships, but cannot yet arbitrate between potential affinities with Afrotheria or Laurasiatheria. With no constraint, maximum parsimony supports Thomashuxleya and Carodnia with Afrotheria. With Notoungulata and Litopterna constrained as monophyletic (including Macrauchenia and Toxodon known for collagens), these clades are reconstructed on the stem to Euungulata (i.e., Perissodactyla and Artiodactyla). Unconstrained, Bayesian analysis weakly supports the possibility that Thomashuxleya is a stem xenarthran; with Notoungulata and Litopterna constrained as monophyletic, the two clades are recovered as sister to Perissodactyla. Anatomical data sampled thus far for Thomashuxleya, combined with collagen amino acids for Pleistocene meridiungulates, substantially limit the number of possible affinities for endemic South American species among mammals, although ambiguity still remains.

thomashuxleya externa
notoungulata
litopterna


The trouble with trilobites: classification, phylogeny and the cryptogenesis problem

Abstract: Abstract Trilobites are an iconic group of extinct arthropods that lived in Palaeozoic oceans for c. 270 Ma, before their demise at the end of the Permian Period. Despite their considerable diversity (> 22 000 species) and abundance, particularly in Cambrian and Ordovician rocks, as well as intensive study for well over 200 years, trilobite systematics remains in a state of flux. In this contribution, the complex history of trilobite classification over the last century is briefly reviewed, including the seminal scheme published by Henry Swinnerton in 1915. The cryptogenesis problem, which relates to the supposedly obscure phylogenetic links between major post-Cambrian trilobite clades and their Cambrian sister taxa, is also discussed. Previous studies have suggested that the cryptogenesis problem is largely a taxonomic artefact, but the Cambrian origins of some post-Cambrian groups, such as the orders Proetida and Odontopleurida, are still unclear. Future directions for research on trilobite systematics are outlined, from taxonomic studies involving comprehensive documentation and extensive illustration of morphology at the species level, through to broad-scale phylogenetic analyses that initiate or test hypotheses about relationships across the major groups. Other ongoing issues to be addressed include identifying the sister group of Trilobita, and determining whether certain taxa, such as the suborder Agnostina and Cambrian family Burlingiidae, represent trilobites.

trilobite
classification
cryptogenesis problem


New model to explain tooth wear with implications for microwear formation and diet reconstruction

Abstract: Significance Dental microwear is among the most common proxies paleontologists use for diet reconstruction. Recent models have suggested that while quartz grit adherent to food produces wear of tooth enamel, softer particles, such as silica phytoliths found in many plants, do not. Some have therefore suggested that microwear patterns better reflect habitat than diet. This is important to paleobiologists because reconstructions of species from the earliest vertebrates to human ancestors have relied on dental microwear as a proxy for diet. Here we present an in vitro study demonstrating that softer particles produce microwear under conditions mimicking chewing. Enamel wear occurs not because an abrasive is hard but because it exceeds the binding force of proteins that hold together hydroxyapatite crystallites. Paleoanthropologists and vertebrate paleontologists have for decades debated the etiology of tooth wear and its implications for understanding the diets of human ancestors and other extinct mammals. The debate has recently taken a twist, calling into question the efficacy of dental microwear to reveal diet. Some argue that endogenous abrasives in plants (opal phytoliths) are too soft to abrade enamel, and that tooth wear is caused principally by exogenous quartz grit on food. If so, variation in microwear among fossil species may relate more to habitat than diet. This has important implications for paleobiologists because microwear is a common proxy for diets of fossil species. Here we reexamine the notion that particles softer than enamel (e.g., silica phytoliths) do not wear teeth. We scored human enamel using a microfabrication instrument fitted with soft particles (aluminum and brass spheres) and an atomic force microscope (AFM) fitted with silica particles under fixed normal loads, sliding speeds, and spans. Resulting damage was measured by AFM, and morphology and composition of debris were determined by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Enamel chips removed from the surface demonstrate that softer particles produce wear under conditions mimicking chewing. Previous models posited that such particles rub enamel and create ridges alongside indentations without tissue removal. We propose that although these models hold for deformable metal surfaces, enamel works differently. Hydroxyapatite crystallites are “glued” together by proteins, and tissue removal requires only that contact pressure be sufficient to break the bonds holding enamel together.

tooth wear
microwear
diet reconstruction
food
aluminium


Ups and downs of belemnite diversity in the Early Jurassic of Western Tethys

Abstract: Although belemnites form a major clade of extinct cephalopods, the early stage of their diversification remains poorly known in time and space. Here we investigate the first diversification episodes of belemnites (order Belemnitida) using a new species‐level database encompassing the Hettangian–Aalenian interval (Early Jurassic – earliest Middle Jurassic) and covering the Western Tethys. Rarefied richness shows a four‐fold increase from the Planorbis chronozone to the Ibex chronozone, a strong decrease between the Margaritatus and Spinatum chronozones, followed by a drop in the Spinatum–Serpentinum interval that is coeval with the second‐order Toarcian biological crisis. The Bifrons chronozone records a high richness that departs significantly from those of the surrounding chronozones. A last richness peak in the Dispansum chronozone precedes a decrease towards the Aalenian. Biogeographical analyses do not reveal any clear large‐scale provincialism for belemnites, in sharp contrast with ammonoids. Such a long‐term homogeneous spatial distribution of belemnites is probably due to: (1) the relatively poorly‐documented fossil record of belemnites, especially in Mediterranean localities; and (2) contrasted dispersal abilities of belemnites compared to ammonoids over the studied time interval.

belemnite
jurassic
western tethys
margaritatus


A new crown-group salamander from the Middle Jurassic of Western Siberia, Russia

Abstract: A new crown-group salamander, Kiyatriton krasnolutskii sp. nov., from the Middle Jurassic (Bathonian) Itat Formation of the Berezovsk Quarry locality in Western Siberia, Russia, is described on the basis of new material and a dentary fragment previously referred to the undescribed salamander taxon BBerezovsk salamander B^(sensu Skutschas 2013). Kiyatriton krasnolutskii sp. nov. differs from K. leshchinskiyi (type species of the genus Kiyatriton) in that the ventrolateral ridges on the atlas are sharper anteriorly, more ventrally oriented and reach the anterior cotylar rims and that the dentary has a relatively taller dental parapet. Kiyatriton krasnolutskii sp. nov. is one of the oldest salamanders in the fossil record. The finding of Kiyatriton krasnolutskii sp. nov. in Berezovsk Quarry is significant for: (1) clarifying that the previously reported BBerezovsk salamander B^is a crown-group salamander of the genus Kiyatriton; (2) extending the stratigraphic range of the genus Kiyatriton backward some 40 million years into the Bathonian, from the previously youngest record in the Aptian-Albian; (3) indicating that K. leshchinskiyi from the Aptian-Albian Shestakovo locality in Western Siberia, Russia, survived as a relic into the Early Cretaceous of present-day Western Siberia; (4) supporting the hypothesis that Bathonian vertebrate faunas of Europe and Western Siberia were homogeneous; and (5) suggesting that all Bathonian crown-group salamanders in Asia could be members of one cryptobranchoid clade and could represent the first radiation of Cryptobranchoidea.

new crown-group salamander
western siberia
berezovsk quarry locality