Earliest known unequivocal rhinocerotoid sheds new light on the origin of Giant Rhinos and phylogeny of early rhinocerotoids

Abstract:
Forstercooperiines are a group of primitive rhinocerotoids with a relatively large body size in the Eocene, and normally considered to be closely related to Giant Rhinos. Here we report a new forstercooperiine, Pappaceras meiomenus sp. nov., from the late Early Eocene Arshanto Formation, Erlian Basin, Nei Mongol, China. Pappaceras is the earliest known unequivocal rhinocerotoid, and the holotype of the new species, represented by the most complete cranium of forstercooperiines known to date, shows the earliest evidence of reduction of the first upper premolar in rhinocerotoids, and resembles paraceratheriine Juxia in basicranial features, supporting the interpretation that the forstercooperiine clade is ancestral to paraceratheriines. The new species also displays some similarities with amynodontids in craniodental structures. Phylogenetic analysis identifies P. meiomenus as a basal taxon of the monophyletic forstercooperiines. It also reveals
novel phylogenetic relationships of early rhinocerotoids that indicates Uintaceras is the sister group of paraceratheriids, to which amynodontids are more closely related than to any other group of rhinocerotoids. Furthermore, the eggysodontid clade is excluded from hyracodontids and placed as the sister group of rhinocerotids. Hyracodontidae, excluding paraceratheriids and eggysodontids, is placed as the most basal group of the rhinocerotoids.

rhinocerotoid forstercooperiine pappaceras holotype asia


Low elbow mobility indicates unique forelimb posture and function in a giant extinct marsupial

Abstract: Joint mobility is a key factor in determining the functional capacity of tetrapod limbs, and is important in palaeobiological reconstructions of extinct animals. Recent advances have been made in quantifying osteological joint mobility using virtual computational methods; however, these approaches generally focus on the proximal limb joints and have seldom been applied to fossil mammals. Palorchestes azael is an enigmatic, extinct ~1000 kg marsupial with no close living relatives, whose functional ecology within Australian Pleistocene environments is poorly understood. Most intriguing is its flattened elbow morphology, which has long been assumed to indicate very low mobility at this important joint. Here, we tested elbow mobility via virtual range of motion (ROM) mapping and helical axis analysis, to quantitatively explore the limits of Palorchestes' elbow movement and compare this with their living and extinct relatives, as well as extant mammals that may represent functional analogues. We find that Palorchestes had the lowest elbow mobility among mammals sampled, even when afforded joint translations in addition to rotational degrees of freedom. This indicates that Palorchestes was limited to crouched forelimb postures, something highly unusual for mammals of this size. Coupled flexion and abduction created a skewed primary axis of movement at the elbow, suggesting an abducted forelimb posture and humeral rotation gait that is not found among marsupials and unlike that seen in any large mammals alive today. This work introduces new quantitative methods and demonstrates the utility of comparative ROM mapping approaches, highlighting that Palorchestes' forelimb function was unlike its contemporaneous relatives and appears to lack clear functional analogues among living mammals.

forelimb posture
marsupial
freedom
low elbow mobility


Abstract: This is the third and last of a series of reports that provide detailed descriptions and taxonomic revisions of the fauna from the Turtle Bluff Member (TBM) of the middle Eocene Bridger Formation of southwestern Wyoming. The TBM has been designated as the stratotype section for biochron Ui1a (earliest Uintan) of the Uintan North American Land Mammal age and here we document new faunal elements along with new UPb geochronologic and paleomagnetic data for the TBM. Prior to these reports, detailed systematic accounts of the taxa from the TBM were unavailable with the exception of one primate (Hemiacodon engardae). Here we document the occurrence of the following didelphimorphian marsupials from the TBM: Herpetotherium knighti, Herpetotherium marsupium, Peradectes chesteri, and Peradectes californicus. New UPb dates of 47.31 ± 0.06 Ma and 46.94 ± 0.14 Ma from the TBM provide precise constraints on the age of the fauna. These dates plus new paleomagnetic data further support the existing evidence that the TBM Fauna and the boundary between the Bridgerian and Uintan North American Land Mammal ages occurs within the lower part of Chron C21n of the Geomagnetic Polarity Time Scale. The only other fauna from North America that can confidently be assigned to biochron Ui1a is the Basal Tertiary Local Fauna from the Devil's Graveyard Formation of Texas. Revisions of the faunal characterizations of biochrons Ui1a (earliest Uintan) and Ui1b (early Uintan) of the Uintan North America Land Mammal age are proposed to further clarify their differences. Paul C. Murphey. Research Associate, Department of Paleontology, San Diego Museum of Natural History, 1788 El Prado, San Diego, California 92101, USA. pmurphey@sdnhm.org Thomas S. Kelly. Research Associate, Vertebrate Paleontology Department, Natural History Museum of Los Angeles County, 900 Exposition Blvd., Los Angeles, California 90007, USA. tom@tskelly.gardnerville.nv.us Kevin R. Chamberlain. Research Professor, Department of Geology and Geophysics, University of Wyoming, 1000 E. University Ave., Laramie, Wyoming 82071, USA and Faculty of Geology and Murphey, Paul C., Kelly, Thomas S., Chamberlain, Kevin R., Tsukui, Kaori, and Clyde, William C. 2018. Mammals from the earliest Uintan (middle Eocene) Turtle Bluff Member, Bridger Formation, southwestern Wyoming, USA, Part 3: Marsupialia and a reevaluation of the Bridgerian-Uintan North American Land Mammal Age transition. Palaeontologia Electronica 21.2.25A 1-52. https://doi.org/

middle eocene
southwestern wyoming
marsupialia


New insights into the Upper Palaeolithic of the Caucasus through the study of personal ornaments. Teeth and bones pendants from Satsurblia and Dzudzuana caves (Imereti, Georgia)

Abstract: The region of western Georgia (Imereti) in the Southern Caucasus has been a major geographic corridor for human migrations during the Middle and Upper Paleolithic. Data of recent research and excavations in this region display its importance as a possible route for the dispersal of anatomically modern humans (AMH) into northern Eurasia. Nevertheless, within the local research context, bone-working and personal ornaments have yet contributed but little to the Upper Palaeolithic (UP) regional sequence’s characterization. Here we present an archaeozoological, technological and use-wear study of pendants from two local UP assemblages, originating in the Dzudzuana Cave and Satsurblia Cave. The ornaments were made mostly of perforated teeth, though some specimens were made on bone. Both the manufacturing marks made during preparation and use-wear traces indicate that they were personal ornaments, used as pendants or attached to garments. Detailed comparison between ornament assemblages from northern and southern Caucasus reveal that they are quite similar, supporting the observation of cultural bonds between the two regions, demonstrated previously through lithic techno-typological affinities. Furthermore, our study highlights the importance attributed to red deer (Cervus elaphus) by the UP societies of the Caucasus in sharing aesthetic values and/or a symbolic sphere.


Quantifying foraminiferal growth with high-resolution X-ray computed tomography: New opportunities in foraminiferal ontogeny, phylogeny, and paleoceanographic applications

Abstract: The latest generation of high-resolution X-ray computed tomography (HRXCT), with a submicron resolution, enables for the first time three-dimensional (3D) imaging and bio-metric quantification of foraminiferal interiors. Here we exemplify the basic possibilities and opportunities of this new technique by means of an analysis on a fossil specimen of Pseudouvigerina sp. from the basal Paleocene of the Brazos River, Texas. The total scan consists of 1200 X-ray radiographs generated during stepwise rotation (0.3 degrees) of the specimen. These radiographs were processed and reconstructed to build cross-sectional images of the object. After 3D rendering of the data, the specimens' chambers could be segmented, showing an exponential ontogenetic growth rate. From the second chamber onward (i.e., after the megalospheric proloculus with a volume of 10(4) mu m(3)), the size of the chambers steadily increases by a factor of similar to 1.5. Various other dimensions can also be calculated from the scan, such as the total volume of shell calcite or the size of the foramen. The technological improvements with HRXCT could open up a new era in fundamental biometric-evolutionary research and provide a means of morphologic evaluation of phylogenies based on molecular data. Eventually, the accuracy of paleoceanographic and paleoclimatic reconstructions could also benefit from the possibility of morphological differentiation between cryptic planktic species.

high-resolution x-ray
tomography
opportunity


Abstract: Travouillon, K.J., Archer, M. & Hand, S.J., 21.01.2015. Revision of Wabularoo, an early macropodid kangaroo from mid-Cenozoic deposits of the Riversleigh World Heritage Area, Queensland, Australia. Alcheringa 39, xxx–xxx. ISSN 0311-5518 Since its original description, the phylogenetic relationships of the macropodoid Wabularoo naughtoni Archer, 1979, from the Riversleigh World Heritage Area have remained a mystery. We have recovered new material representing the upper dentition previously unknown for this late Oligocene taxon, and new early Miocene specimens representing the upper and lower dentition of a second species, W. prideauxi sp. nov. We assessed their phylogenetic relationships using matrices from two previous studies, and recovered both species of Wabularoo as basal macropodids. Wabularoo is characterized by having bilophodont molars, large sectorial P3/p3 with coarse ridges, presence of a forelink, neometaconule and postlink on M1–3, well-developed anterior cingulum, precingulum, postparacrista and premetacrista on all upper molars, and retention of StC on M1–2. Although the subfamilial affinities of Wabularoo are unresolved, we propose that several morphological features of the dentary and the upper and lower third premolar suggest affinity with Sthenurinae. These features include short diastema, posteriorly positioned digastric eminence, presence of posterior mental foramen, and similar molar and premolar morphology. If our interpretations are correct, sthenurines arose from basal macropodids between the early and middle Miocene. Kenny J. Travouillon [kennytravouillon@hotmail.com] School of Earth Sciences, University of Queensland, St Lucia, Queensland 4072, Australia; Michael Archer [m.archer@unsw.edu.au] and Suzanne J. Hand [s.hand@unsw.edu.au] School of Biological, Earth and Environmental Sciences, University of New South Wales, New South Wales 2052, Australia.


Abstract: Emry, Robert J. Revised Tertiary Stratigraphy and Paleontology of the Western Beaver Divide, Fremont County, Wyoming. Smithsonian Contributions to Paleobiology, number 25, 20 pages, 6 figures, 1975.•In the western Beaver Divide area in west-central Wyoming, a lens of coarse Tertiary volcanic conglomerate and tuff disconfqrmably overlies Uintan rocks of the Wagon Bed Formation. The coarse volcaniclastic rocks were previously regarded as a faciès of the Beaver Divide Conglomerate Member of the Chadronian White River Formation, although fossil mammals from the volcaniclastic unit are species known otherwise only from Uintan rocks. Reexamination of field relations has shown that the White River Formation disconformably overlies the volcaniclastic unit. The "lower Uinta C" temporal equivalence indicated by the fossils from the volcaniclastic unit is no longer anomalous; the underlying Wagon Bed Formation has fossil mammals indicating "Uinta B" equivalence, and the overlying White River Formation has a fairly diverse Chadronian fauna. The Uintan volcaniclastic unit is assigned to the Wiggins Formation. The Beaver Divide Conglomerate Member is restricted to conglomerate in the lower part of the White River Formation. It is composed predominantly of clasts of locally derived Precambrian crystalline rocks. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institutions annual report, Smithsonian Year. SI PRESS NUMBER 6013. SERIES COVER DESICN: The trilobite Phacops rana Green. Library of Congress Cataloging in Publication Data Emry, Robert J. Revised tertiary stratigraphy and paleontology of the Western Beaver Divide, Fremont County, Wyoming. (Smithsonian contributions to paleobiology, no. 25) 1. Geology, Stragraphic•Tertiary. 2. Paleontology•Wyoming•Fremont Co. 3. Paleontology• Tertiary. I. Title: Revised tertiary stratigraphy and paleontology of the Western Beaver Divide ... II. Series: Smithsonian Institution. Smithsonian contributions to paleobiology, no. 25. QE701.S56 no. 25 [QE691] 560'.8s [551.7'8'0978763] 75-8799

tertiary stratigraphy
paleontology
western beaver divide
white river formation


A new dustywing (Neuroptera: Coniopterygidae) from the Early Cretaceous amber of Spain

Abstract: A new Cretaceous dustywing, Soplaoconis ortegablancoi gen. et sp. nov. (Neuroptera: Coniopterygidae), is described from four specimens preserved in Early Cretaceous (Albian, ~105Ma) El Soplao amber (Cantabria, northern Spain). Two additional specimens are assigned to this new taxon. A crossvenational abnormality on an area of diagnostic significance from one of the holotype’s forewings provides a reminder of the importance of not ruling out character plasticity or teratoses when evaluating palaeodiversity. A comment on the possible palaeoecological significance of the co-occurrence as syninclusions of plant trichomes with the holotype of S. ortegablancoi and seven of the eleven described Burmese amber dustywing species is provided.


Three-dimensional geometric morphometric analysis of the skull of Protoceratops andrewsi supports a socio-sexual signalling role for the ceratopsian frill

Abstract: Socio-sexual selection is predicted to be an important driver of evolution, influencing speciation, extinction and adaptation. The fossil record provides a means of testing these predictions, but detecting its signature from morphological data alone is difficult. There are, nonetheless, some specific patterns of growth and variation which are expected of traits under socio-sexual selection. The distinctive parietal-squamosal frill of ceratopsian dinosaurs has previously been suggested as a socio-sexual display trait, but evidence for this has been limited. Here, we perform a whole-skull shape analysis of an unprecedentedly large sample of specimens of Protoceratops andrewsi using a high-density landmark-based geometric morphometric approach to test four predictions regarding a potential socio-sexual signalling role for the frill. Three predictions—low integration with the rest of the skull, significantly higher rate of change in size and shape during ontogeny, and higher morphological variance than other skull regions—are supported. One prediction, sexual dimorphism in shape, is not supported, suggesting that sexual differences in P. andrewsi are likely to be small. Together, these findings are consistent with mutual mate choice or selection for signalling quality in more general social interactions, and support the hypothesis that the frill functioned as a socio-sexual signal in ceratopsian dinosaurs.

skull
socio-sexual signalling role
frill


Trilobite ‘pelotons’: possible hydrodynamic drag effects between leading and following trilobites in trilobite queues

Abstract: Energy saving mechanisms in nature allow following organisms to expend less energy than leaders. Queues, or ordered rows of individuals, may form when organisms exploit the available energy saving mechanism while travelling at near‐maximal sustainable metabolic capacities; compact clusters form when group members travel well below maximal sustainable metabolic capacities. The group size range, given here as the ratio of the difference between the size of the largest and smallest group members, and the size of the largest member (as a percentage), has been hypothesized to correspond proportionately to the energy saving quantity because weaker, smaller, individuals sustain the speeds of stronger, larger, individuals by exploiting the energy saving mechanism (as a percentage). During migration, small individuals outside this range may perish, or form sub‐groups, or simply not participate in migratory behaviour. We approximate drag forces for leading and following individuals in queues of the late Devonian (c. 370 Ma) trilobite Trimerocephalus chopini. Applying data from literature on Rectisura herculea, a living crustacean, we approximate the hypothetical walking speed and maximal sustainable speeds for T. chopini. Our findings reasonably support the hypothesis that among the population of fossilized queues of T. chopini reported in the literature, trilobite size range was 75%, while the size range within queues was 63%; this corresponds reasonably with drag reductions in following positions that permit c. 61.5% energy saving for trilobites following others in optimal low‐drag positions. We model collective trilobite behaviour associated with hydrodynamic drafting.

hydrodynamic drag effect
queue
trilobite


Stereom microstructure of columnal latera: a character for assessing phylogenetic relationships in articulate crinoids

Abstract: The stereom microstructure of columnal latera in various articulate crinoids is examined to ascertain its potential application in phylogenetic studies. Most show either a poorly ordered labyrinthic stereom or a more regularly ordered perforate stereom with lumina arranged in an en echelon pattern. Labyrinthic stereom is taxonomically widespread and is interpreted here as the plesiomorphic state. Perforate stereom, typically with an en echelon arrangement of elliptical lumina, appears confined to the Isocrinina and is considered to be apomorphic for that group. The absence of any development of perforate stereom in the bourgueticrinid Democrinus suggests that the bourgueticrinids have affinities with the comatulids rather than with the isocrinids. A second type of perforate stereom, with sinuous or straight lines of circular to elongate lumina, has been found only in Pentacrinites and may be autapomorphic for that group. The shape and spacing of stereom lumina on the columnal latera of different genera of isocrinids displays minor variation that may have some value for assessing phylogenetic affinity at genus and family level in taxa known only from columnals.

columnal latera
crinoid
stereom microstructure


Carbon and oxygen isotopes of bulk carbonate in sediment deposited beneath the eastern equatorial Pacific over the last 8 million years

Abstract: To improve the understanding and utility of bulk carbonate stable carbon and oxygen isotope measurements, we examine sediment from cores in the eastern equatorial Pacific that span the last 8Ma. We measured C-13 and O-18 in 791 samples from Integrated Ocean Drilling Program Site U1338 and Deep Sea Drilling Project Site 573, both located close to the Pacific equator. In 100 samples, we measured C-13 and O-18 on isolated <63 mu m and <38 mu m fractions, which concentrates calcareous nannofossil carbonate and progressively excludes foraminiferal carbonate. Bulk carbonate C-13 and O-18 records are similar to published records from other sites drilled near the equator and seem to reflect mixed layer conditions, albeit with some important caveats involving the precipitation of calcite by coccolithophores. The comparatively lower C-13 and O-18 of the <63 mu m and <38 mu m fractions in sediments younger than 4.4Ma is attributed to an increase in deep-dwelling planktic foraminifera material in bulk carbonate, shifting the bulk isotopic signals toward higher values. Bulk carbonate C-13 is similar over 2500km along the Pacific equator, suggesting covarying concentrations and C-13 of dissolved inorganic carbon within surface waters since 8Ma. Greater bulk sediment C-13 and O-18, higher sedimentation rates, and low content of coarse material suggest intensified wind-driven upwelling and enhanced primary productivity along the Pacific equator between 8.0 and 4.4Ma, although a full understanding of bulk carbonate records will require extensive future work.

bulk carbonate
eastern equatorial pacific
carbon


Bumblebees take the high road: climatically integrative biogeography shows that escape from Tibet, not Tibetan uplift, is associated with divergences of present‐day Mendacibombus

Abstract: Many claims that uplift of the Qinghai-Tibetan plateau (QTP) drove the divergences of extant high-elevation biota have recently been challenged. For Mendacibombus bumblebees, high-elevation specialists with distributions centred on the QTP, we examine broader explanations. We extend integrative biogeography to cover multiple contributing factors by using a framework of sequential filters: 1) molecular evidence from four genes is used to estimate phylogenetic relationships, with time calibration from a published estimate; 2) spatial evidence from current distributions is combined with the phylogeny and constrained by a model of short-distance dispersal along mountain corridors to estimate ancestral distributions by both S-DIVA and S-DEC analysis; 3) geological evidence from the literature is used to constrain when high mountain ranges were uplifted to become potential corridors; and 4) climatological evidence from Mendacibombus niche-evolution reconstructions and from palaeoclimate simulations is used to constrain when habitat was suitable in key gaps within corridors. Explanations for Mendacibombus distributions can be identified that require only short-distance dispersal along mountain corridors, commensurate with the limited dispersal ability observed for bumblebees. These explanations depend on the timing of uplift of mountain ranges, regional climate change, and climate-niche evolution. The uplift of the QTP may have contributed to the initial Oligocene divergence of the common ancestor of Mendacibombus from other bumblebees, but for the first two thirds of the history of Mendacibombus, only a single lineage has present-day descendants. Divergence of multiple extant Mendacibombus lineages coincided with the Late Miocene–Pliocene uplift of externally connecting mountains, combined with regional climate cooling. These changes provided greater connectivity of suitable habitat, allowing these bumblebees to disperse out of the western QTP via new high bridges, escaping along the mountain corridors of the Tian Shan and Hindu Kush ranges, reaching eventually far to the west (Iberian Peninsula) and to the north-east (Kamchatka).


A new genus and species of marine catfishes (Siluriformes; Ariidae) from the upper Eocene Birket Qarun Formation, Wadi El-Hitan, Egypt

Abstract: Wadi El-Hitan, the UNESCO World Heritage Site, of the Fayum Depression in the northeast part of the Western Desert of Egypt, has produced a remarkable collection of Eocene vertebrates, in particular the fossil whales from which it derives its name. Here we describe a new genus and species of marine catfishes (Siluriformes; Ariidae), Qarmoutus hitanensis, from the base of the upper Eocene Birket Qarun Formation, based on a partial neurocranium including the complete left side, partial right dentary, left suspensorium, two opercles, left pectoral girdle and spine, nuchal plates, first and second dorsal spines, Weberian apparatus and a disassociated series of abdominal vertebrae. All of the elements belong to the same individual and some of them were found articulated. Qarmoutus gen. nov. is the oldest and the most complete of the Paleogene marine catfishes unearthed from the Birket Qarun Formation. The new genus exhibits distinctive features not seen in other African Paleogene taxa, such as different sculpturing on the opercle and pectoral girdle with respect to that on the neurocranium and nuchal plates, denticulate ornamentation on the skull bones arranged in longitudinal rows and forming a radiating pattern on the sphenotic, pterotic, extrascapular and the parieto-supraoccipital, indentations or pitted ornamentation on the nuchal plates as well as the parieto-supraoccipital process, strut-like radiating pattern of ornamentation on the opercle from the proximal articulation to margins, longitudinal, curved, reticulate ridges and tubercular ornamentations on the cleithrum, sinuous articulation between the parieto-supraoccipital process and the anterior nuchal plate, long, narrow, and arrowhead shaped nuchal shield, very small otic capsules restricted to the prootic. Multiple parsimony and Bayesian morphological phylogenetic analyses of Ariidae, run with and without “molecular scaffolds”, yield contradictory results for the placement of Qarmoutus; the genus is either a phylogenetically basal ariid, or it is deeply nested within the ariid clade containing New World species of Sciades.


A review of the lower actinopterygian phylogeny

Abstract: A review of lower actinopterygian phylogeny has led us to the conclusion that the Cladistia are the sister group of Recent actinopterygians (Actinopteri) and that the extinct Palaeonisciformes are a paraphyletic group, comprising stem-group actinopterygians (e.g. Cheirolepis), stem-group actinopterans (e.g. Moythomasia) and relatives of higher actinopterans such as Pteronisculus. Our analysis further concluded that the Acipenseriformes formed a clade together with Saurichthys and Birgeria, which was most parsimoniously resolved when the Acipenseriformes and Saurichthys were sister groups. (C) 2005 The Linnean Society of London.

review
low actinopterygian phylogeny
paleozoic


New evidence from the Palaeocene of Patagonia (Argentina) on the evolution and palaeo-biogeography of Meiolaniformes (Testudinata, new taxon name)

Abstract: Peligrochelys walshae gen. et sp. nov. is a new stem turtle closely related to the clade Meiolaniidae found in the Palaeocene levels of the Salamanca Formation (Maastrichtian–Danian) of central Patagonia, Chubut Province, Argentina. A phylogenetic analysis shows that Peligrochelys walshae forms a monophyletic group with Mongolochelys efremovi, a clade that, in return, is the sister group of a clade formed by Patagoniaemys gasparinae, Otwayemys cunicularius, Kallokibotion bajazidi and Meiolaniidae. Meiolaniidae is recovered deeply nested in a monophyletic group (Meiolaniformes, new taxon name) dominated by Gondwanan taxa (e.g. Chubutemys copelloi, Patagoniaemys gasparinae, Otwayemys cunicularius and Peligrochelys walshae), that also includes some notable Laurasian representatives (Mongolochelys efremovi and Kallokibotion bajazidi). The biogeographic scenario presented here supports the hypothesis that this group of turtles may have originated as early as the Early Cretaceous in the South American part of Gondwana. The long ghost lineage that extends below this clade suggests that it may have originated any time between the Early Jurassic and the Early Cretaceous, implying a Pangaean or Gondwanan origin for the clade, respectively. The phylogenetic scenario presented here shows that at least two lineages (Peligrochelys walshae and Meiolaniidae) of Meiolaniformes survived the K–P boundary extinction. Another interesting characteristic of meiolaniform turtles in the fossil record is their frequent association with another clade of strictly Gondwanan distribution, the pleurodiran clade Chelidae. This association is typically found in outcrops from the Early Cretaceous to the Eocene in central Patagonia, and in the Early Cretaceous and from the Miocene to the Pleistocene in Australia.


Tooth occlusal morphology in the durophagous marine reptiles, Placodontia (Reptilia: Sauropterygia)

Abstract:
Abstract.
 Placodontia were a group of marine reptiles that lived in shallow nearshore environments during the Triassic. Based on tooth morphology it has been inferred that they were durophagous, but tooth morphology differs among species: placodontoid placodonts have teeth described as hemispherical, and the teeth of more highly nested taxa within the cyamodontoid placodonts have been described as flat. In contrast, the sister taxon to the placodonts, Palatodonta bleekeri, like many other marine reptiles, has tall pointed teeth for eating soft-bodied prey. The goals of this paper are to quantify these different tooth morphologies and compare tooth shape among taxa and with a functionally “optimal” tooth. To quantify tooth morphology we measured the radius of curvature (RoC) of the occlusal surface by fitting spheres to 3D surface scans or computed microtomographic scans. Large RoCs correspond to flatter teeth, while teeth with smaller RoCs are pointier; positive RoCs have convex occlusal surfaces, and a negative RoC indicates that the occlusal surface of the tooth is concave. We found the placodontoid taxa have teeth with smaller RoCs than more highly nested taxa, and palatine teeth tend to be flatter and closer to the optimal morphology than maxillary teeth. Within one well-nested clade, the placochelyids, the rearmost palatine teeth have a more complex morphology than the predicted optimal tooth, with an overall concave occlusal surface with a small, medial cusp. These findings are in keeping with the hypothesis that placodonts were specialized durophagous predators with teeth modified to break hard prey items while resisting tooth failure.


New craniodental material of Pronothodectes gaoi Fox (Mammalia, "Plesiadapiformes") and relationships among members of Plesiadapidae.

Abstract: Plesiadapidae are a family of Paleogene mammals thought to have phylogenetic affinities with modern Primates. We describe previously unpublished dentitions and the first skull and isolated petrosals of the plesiadapid Pronothodectes gaoi, collected from middle Tiffanian localities of the Paskapoo Formation in Alberta. Other species of Pronothodectes, traditionally considered the most basal members of the Plesiadapidae, occur at earlier, Torrejonian horizons in Montana, Wyoming, and Alberta. Classification of P. gaoi as a species of Pronothodectes has proved controversial; accordingly, we use the newly available samples and the more extensively preserved specimens to re-evaluate the generic affinities of this species. Included in our study are comparisons with craniodental material known for other plesiadapids and plesiadapiforms. Cladistic analysis of craniodental characters is used to assess the hypothesis that P. gaoi and other species in this genus are basal members of the Plesiadapidae. The new dental evidence confirms that P. gaoi lacks derived character states of other plesiadapids except for a variably present fissuring of the m3 hypoconulid. Moreover, several aspects of the cranium seem to be more primitive in P. gaoi (i.e., more like nonplesiadapid plesiadapiforms) than in later occurring plesiadapids, such as Plesiadapis tricuspidens and Plesiadapis cookei. Cladistic analysis of craniodental morphology supports a basal position of P. gaoi among species of Plesiadapidae, with the exception of other species of Pronothodectes. The basicranium of P. gaoi preserves a laterally placed bony canal for the internal carotid neurovascular system, suggesting that this was the ancestral condition for the family.

craniodental material
pronothodectes
plesiadapidae


Climate variability and human impact in South America during the last 2000 years: synthesis and perspectives from pollen records

Abstract: An improved understanding of present-day climate variability and change relies on high-quality data sets from the past 2 millennia. Global efforts to model regional climate modes are in the process of being validated against, and integrated with, records of past vegetation change. For South America, however, the full potential of vegetation records for evaluating and improving climate models has hitherto not been sufficiently acknowledged due to an absence of information on the spatial and temporal coverage of study sites. This paper therefore serves as a guide to high-quality pollen records that capture environmental variability during the last 2 millennia. We identify 60 vegetation (pollen) records from across South America which satisfy geochronological requirements set out for climate modelling, and we discuss their sensitivity to the spatial signature of climate modes throughout the continent. Diverse patterns of vegetation response to climate change are observed, with more similar patterns of change in the lowlands and varying intensity and direction of responses in the highlands. Pollen records display local-scale responses to climate modes; thus, it is necessary to understand how vegetation–climate interactions might diverge under variable settings. We provide a qualitative translation from pollen metrics to climate variables. Additionally, pollen is an excellent indicator of human impact through time. We discuss evidence for human land use in pollen records and provide an overview considered useful for archaeological hypothesis testing and important in distinguishing natural from anthropogenically driven vegetation change. We stress the need for the palynological community to be more familiar with climate variability patterns to correctly attribute the potential causes of observed vegetation dynamics. This manuscript forms part of the wider LOng-Term multi-proxy climate REconstructions and Dynamics in South America – 2k initiative that provides the ideal framework for the integration of the various palaeoclimatic subdisciplines and palaeo-science, thereby jump-starting and fostering multidisciplinary research into environmental change on centennial and millennial timescales.

south america
pollen record
indicator
climate variability


?Brachychampsa sealeyi, sp nov., (Crocodylia, Alligatoroidea) from the Upper Cretaceous (lower Campanian) Menefee Formation, northwestern New Mexico

Abstract: ABSTRACT ?Brachychampsa sealeyi sp. nov. is a small alligatoroid based on a partial skull, associated partial mandible, and a dorsal? osteoderm from the Upper Cretaceous (lower Campanian) Menefee Formation, northwestern New Mexico. The holotype of ?B. sealeyi is the oldest of four documented Late Cretaceous alligatoroid skulls. ?Brachychampsa sealeyi differs from Brachychampsa montana, Albertochampsa langstoni, and other alligatoroids primarily in having an anteriorly tapering rostrum with a relatively reduced anterior dentition and smaller narial and incisive openings but relatively larger and more bulbous posterior teeth. The single associated osteoderm has a longitudinal keel and surfaces for articulation with overlapping osteoderms. Cladistic analysis suggests that ?B. sealeyi is a sister taxon to B. montana and supports the hypothesis that Brachychampsa and Albertochampsa form a monophyletic clade outside the Alligatoridae. Punctures on the mandible suggests that a bite was inflicted by another allig...

brachychampsa sealeyi
campanian
northwestern new mexico


Paleobiology and comparative morphology of a late Neandertal sample from El Sidrón, Asturias, Spain

Abstract: Fossil evidence from the Iberian Peninsula is essential for understanding Neandertal evolution and history. Since 2000, a new sample ≈43,000 years old has been systematically recovered at the El Sidrón cave site (Asturias, Spain). Human remains almost exclusively compose the bone assemblage. All of the skeletal parts are preserved, and there is a moderate occurrence of Middle Paleolithic stone tools. A minimum number of eight individuals are represented, and ancient mtDNA has been extracted from dental and osteological remains. Paleobiology of the El Sidrón archaic humans fits the pattern found in other Neandertal samples: a high incidence of dental hypoplasia and interproximal grooves, yet no traumatic lesions are present. Moreover, unambiguous evidence of human-induced modifications has been found on the human remains. Morphologically, the El Sidrón humans show a large number of Neandertal lineage-derived features even though certain traits place the sample at the limits of Neandertal variation. Integrating the El Sidrón human mandibles into the larger Neandertal sample reveals a north–south geographic patterning, with southern Neandertals showing broader faces with increased lower facial heights. The large El Sidrón sample therefore augments the European evolutionary lineage fossil record and supports ecogeographical variability across Neandertal populations.


Silurian thelodonts from the Niur Formation, central Iran

Abstract: Thelodont scales are described from the Silurian Niur Formation in the Derenjal Mountains, east central Iran. The material studied herein comes from four stratigraphic levels, composed of rocks formed in a shallow water, carbonate ramp environment. The fauna includes a new phlebolepidiform, Niurolepis susanae gen. et sp. nov. of late Wenlock/?early Ludlow age and a late Ludlow loganelliiform, Loganellia sp. cf. L. grossi, which constitute the first record of these thelodont groups from Gondwana. The phlebolepidiform Niurolepis susanae gen. et sp. nov. is diagnosed by having trident trunk scales with a raised medial crown area separated by two narrow spiny wings from the lateral crown areas; a katoporodidtype histological structure distinguished by a network of branched wide dentine canals. Other scales with a notch on a smooth rhomboidal crown and postero-laterally down-stepped lateral rims have many characters in common with Loganellia grossi. Associated with the thelodonts are indeterminable acanthodian scales and a possible dentigerous jaw bone fragment. This finding also provides evidence of a hitherto unknown southward dispersal of Loganellia to the shelves of peri-Gondwana.

niur formation
iran
unknown southward dispersal
peri-gondwana


Ediacaran discs from South America: probable soft-bodied macrofossils unlock the paleogeography of the Clymene Ocean

Abstract: The origin, affinity and paleoecology of macrofossils of soft-bodied organisms of the terminal Ediacaran Period have been highly debated. Previous discoveries in South America are restricted to small shelly metazoans of the Nama Assemblage. Here we report for the first time the occurrence of discoidal structures from the Upper Ediacaran Cerro Negro Formation, La Providencia Group, Argentina. Specimens are preserved in tabular sandstones with microbially-induced sedimentary structures. Flute marks and linear scours at the base of the sandstone layers indicate deposition under high energy, episodic flows. Stratigraphic, sedimentologic, petrographic and taphonomic analyses indicate that the origin of these structures is not related to abiotic process. Preservational and morphological features, as invagination and the presence of radial grooves, indicate that they resemble typical morphs of the Aspidella plexus. The large number of small-sized individuals and the wide range of size classes with skewed distribution suggest that they lived in high-density communities. The presence of Aspidella in the Cerro Negro Formation would represent the first reliable record of Ediacaran soft-bodied organisms in South America. It also supports the paleogeographic scenario of the Clymene Ocean, in which a shallow sea covered part of the southwest Gondwana at the end of the Ediacaran.

south america
clymene ocean
ediacaran disc


Dental homologies and evolutionary transformations in Caviomorpha (Hystricognathi, Rodentia): new data from the Paleogene of Peruvian Amazonia

Abstract: ABSTRACT Dental homologies and evolutionary transformations within caviomorph rodents have long been disputed. Here, we participate in these debates in providing new insights from the dental morphology of Paleogene caviomorphs from Peruvian Amazonia (Contamana and Shapaja). Their analyses and comparisons with many hystricognaths allow (1) to generalize some hypotheses previously proposed about occlusal morphology of caviomorph cheek teeth, and (2) to propose new ones. In caviomorphs, the third crest of upper teeth would correspond either to a mesoloph or to a mesolophule or to a combination of both. The transformation from a pentalophodont pattern to a tetralophodont pattern would be explained by the disappearance of the metaloph. Likewise, the transformation from a tetralophodont pattern to a trilophodont pattern is observed by the loss of the third crest. A direct transformation from a pentalophodont pattern to a trilophodont pattern is also observed. Concerning lower teeth, discrepancies of homologies are centered on the mesial cristids, which can be notably distinguished depending on their compositions and connections with other structures. The ancestral patterns of caviomorph lower molars and dp4s were likely tetralophodont and pentalophodont, respectively. However, schemes with five and four (even three) transverse cristids cannot be ruled out for the two loci, respectively.

evolutionary transformation
peruvian amazonia
dental homology


The Integrated Plant Record (IPR) analysis: Methodological advances and new insights into the evolution of European Palaeogene/Neogene vegetation

Abstract: The Integrated Plant Record (IPR) vegetation analysis serves as a proxy method to derive major types of zonal palaeovegetation based on the proportion of zonal key components. This paper pursues two goals: 1) to introduce two tools (Drudge 1 and Drudge 2) to statistically determine close modern proxies for fossil plant assemblages out of the reference set of currently 505 modern vegetation units. These range from closed forests to more open (steppe) environments from Europe and Asia and are based on the correspondence in the proportion of the zonal key components (IPR Similarity) and Taxonomic Similarity (TS, genus level); and 2) to present the extension of the calibration dataset of modern zonal vegetation using the natural vegetation of Europe, the Caucasus, China, and Mongolia. The tools are tested on six Central European plant assemblages from the late Eocene to the late Pliocene. For the late Eocene to early Miocene, the results indicate a close relationship to East Asian vegetation based both on IPR Similarity and TS. For the younger sites, IPR Similarity points towards European vegetation, whereas TS still indicates closer East Asian affinity. The summary results (as presented in the Results – Mix) derived by both tools deliver modern proxy vegetation units, which are in good agreement with modern vegetation analogues proposed by traditional empirical studies. The IPR Similarity results probably reflect climate change, which results in proportions of zonal key components, i.e., leaf physiognomy of zonal forests that are more similar to modern European than to Asian vegetation from the latest early/middle Miocene onwards. Vasilis Teodoridis. Department of Biology and Environmental Studies, Faculty of Education, Charles University, Prague, Czech Republic. vasilis.teodoridis@pedf.cuni.cz Petr Mazouch. Faculty of Informatics and Statistics, University of Economics, Prague, Czech Republic. mazouchp@vse.cz Johanna Kovar-Eder. State Museum of Natural History Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany. johanna.eder@smns-bw.de


Large‐scale evolutionary trends of Acrochordiceratidae Arthaber, 1911 (Ammonoidea, Middle Triassic) and Cope’s rule

Abstract: Abstract:  Directed evolution of life through millions of years, such as increasing adult body size, is one of the most intriguing patterns displayed by fossil lineages. Processes and causes of such evolutionary trends are still poorly understood. Ammonoids (externally shelled marine cephalopods) are well known to have experienced repetitive morphological evolutionary trends of their adult size, shell geometry and ornamentation. This study analyses the evolutionary trends of the family Acrochordiceratidae Arthaber, 1911 from the Early to Middle Triassic (251–228 Ma). Exceptionally large and bed‐rock‐controlled collections of this ammonoid family were obtained from strata of Anisian age (Middle Triassic) in north‐west Nevada and north‐east British Columbia. They enable quantitative and statistical analyses of its morphological evolutionary trends. This study demonstrates that the monophyletic clade Acrochordiceratidae underwent the classical evolute to involute evolutionary trend (i.e. increasing coiling of the shell), an increase in its shell adult size (conch diameter) and an increase in the indentation of its shell suture shape. These evolutionary trends are statistically robust and seem more or less gradual. Furthermore, they are nonrandom with the sustained shift in the mean, the minimum and the maximum of studied shell characters. These results can be classically interpreted as being constrained by the persistence and common selection pressure on this mostly anagenetic lineage characterized by relatively moderate evolutionary rates. Increasing involution of ammonites is traditionally interpreted by increasing adaptation mostly in terms of improved hydrodynamics. However, this trend in ammonoid geometry can also be explained as a case of Cope’s rule (increasing adult body size) instead of functional explanation of coiling, because both shell diameter and shell involution are two possible paths for ammonoids to accommodate size increase.


Biodiversity and terrestrial ecology of a mid-Cretaceous, high-latitude floodplain, Alexander Island, Antarctica

Abstract: The biodiversity and terrestrial ecology of the Late Albian Triton Point Formation (Fossil Bluff Group), Alexander Island, Antarctica is analysed to improve our understanding of polar biomes during the mid-Cretaceous thermal optimum. This formation was deposited on a high-latitude (75°S) floodplain and consists of two facies associations, a lower braided alluvial plain unit and an upper coastal meander-belt unit. Analysis of fossil plants in well exposed palaeosols reveals the existence of spatially complex plant communities. Braidplains supported patchy, low-density (91 trees/ha) stands of podocarp and taxodioid conifers on floodbasin substrates, and conifer–cycadophyte–fern–angiosperm thickets in riparian settings. Coastal meander-belts supported medium density (568 trees/ha) podocarp–araucarian conifer forests on mature floodbasin soils, and fern–angiosperm–ginkgo thickets in riparian settings. Growth-ring analysis indicates plants experienced stressful growing conditions on the braidplain characterized by high-frequency flood events, but more favourable growing conditions on the coastal plain. Additional vegetation disturbances were caused by arthropod–fungal attack, frost and wildfire. In terms of structure, composition, ecology and productivity these predominantly evergreen, broad-leafed conifer forests bear similarities to the extant temperate rainforests of New Zealand.

terrestrial ecology
floodplain
alexander island
temperate rainforest


Phylogenetic analysis reveals that Rhabdopleura is an extant graptolite

Abstract: A phylogenetic analysis of morphological data from modern pterobranch hemichordates (Cephalodiscus, Rhabdopleura) and representatives of each of the major graptolite orders reveals that Rhabdopleura nests among the benthic, encrusting graptolite taxa as it shares all of the synapomorphies that unite the graptolites. Therefore, rhabdopleurids can be regarded as extant members of the Subclass Graptolithina (Class Pterobranchia). Combined with the results of previous molecular phylogenetic studies of extant deuterostomes, these results also suggest that the Graptolithina is a sister taxon to the Subclass Cephalodiscida. The Graptolithina, as an important component of Early–Middle Palaeozoic biotas, provide data critical to our understanding of early deuterostome phylogeny. This result allows one to infer the zooid morphology, mechanics of colony growth and palaeobiology of fossil graptolites in direct relation to the living members of the clade. The Subdivision Graptoloida (nom. transl.), which are all planktic graptolites, is well supported in this analysis. In addition, we recognize the clade Eugraptolithina (nov.). This clade comprises the Graptoloida and all of the other common and well-known graptolites of the distinctive Palaeozoic fauna. Most of the graptolites traditionally regarded as tuboids and dendroids appear to be paraphyletic groups within the Eugraptolithina; however, Epigraptus is probably not a member of this clade. The Eugraptolithina appear to be derived from an encrusting, Rhabdopleura-like species, but the available information is insufficient to resolve the phylogeny of basal graptolites. The phylogenetic position of Mastigograptus and the status of the Dithecoidea and Mastigograptida also remain unresolved. □ Biodiversity, Cambrian, Hemichordata, Deuterostomia, Ordovician.

rhabdopleura
graptolite
extant member
phylogenetic analysis
fossil member


Discontinuity of Human Presence at Atapuerca during the Early Middle Pleistocene: A Matter of Ecological Competition?

Abstract: Increasing evidence suggests that the European human settlement is older than 1.2 Ma. However, there is a fierce debate about the continuity or discontinuity of the early human settlement of Europe. In particular, evidence of human presence in the interval 0.7−0.5 Ma is scarce in comparison with evidence for the previous and later periods. Here, we present a case study in which the environmental conditions at Sierra de Atapuerca in the early Middle Pleistocene, a period without evidence of human presence, are compared with the conditions in the previous period, for which a relatively intense human occupation is documented. With this objective in mind, the available resources for a human population and the intensity of competition between secondary consumers during the two periods are compared using a mathematical model. The Gran Dolina site TD8 level, dated to 0.7−0.6 Ma, is taken as representative of the period during which Atapuerca was apparently not occupied by humans. Conditions at TD8 are compared with those of the previous period, represented by the TD6-2 level, which has yielded abundant evidence of intense human occupation. The results show that survival opportunities for a hypothetical human population were lower at TD8 than they were at TD6-2. Increased resource competition between secondary consumers arises as a possible explanation for the absence of human occupation at Atapuerca in the early Middle Pleistocene.

human presence
atapuerca
middle pleistocene


Coupling of palaeontological and neontological reef coral data improves forecasts of biodiversity responses under global climatic change

Abstract: Reef corals are currently undergoing climatically driven poleward range expansions, with some evidence for equatorial range retractions. Predicting their response to future climate scenarios is critical to their conservation, but ecological models are based only on short-term observations. The fossil record provides the only empirical evidence for the long-term response of organisms under perturbed climate states. The palaeontological record from the Last Interglacial (LIG; 125 000 years ago), a time of global warming, suggests that reef corals experienced poleward range shifts and an equatorial decline relative to their modern distribution. However, this record is spatio-temporally biased, and existing methods cannot account for data absence. Here, we use ecological niche modelling to estimate reef corals' realized niche and LIG distribution, based on modern and fossil occurrences. We then make inferences about modelled habitability under two future climate change scenarios (RCP4.5 and RCP8.5). Reef coral ranges during the LIG were comparable to the present, with no prominent equatorial decrease in habitability. Reef corals are likely to experience poleward range expansion and large equatorial declines under RCP4.5 and RCP8.5. However, this range expansion is probably optimistic in the face of anthropogenic climate change. Incorporation of fossil data in niche models improves forecasts of biodiversity responses under global climatic change.

forecast
biodiversity response
climatic change


A multicoral calibration method to approximate a universal equation relating Sr/Ca and growth rate to sea surface temperature

Abstract: [1] Combining strontium-to-calcium ratios (Sr/Ca) with mean annual growth rates in Bermuda Diploria labyrinthiformis (brain corals) is shown to improve sea surface temperature (SST) calibrations relative to instrumental data. Growth-corrected Sr/Ca–SST calibrations based on single-coral colonies over the same calibration interval, however, are found to be poorly suited for application to data from different coral colonies. This raises concerns about the accuracy of SST reconstructions from fossil coral measurements that involve extrapolation beyond the range of values seen during the calibration period. Here we pursue a novel approach to this problem by incorporating data from multiple coral colonies into a single growth-corrected Sr/Ca–SST calibration equation, effectively expanding the range of modern values constraining the model. The use of a multiple-colony calibration model for reconstructing SST yields greater precision and accuracy relative to instrumental data than single-colony models, providing greater confidence for applications to fossil coral samples.

growth rate
sea surface temperature
application


An exceptional fossil skull from South America and the origins of the archosauriform radiation

Abstract: Birds, dinosaurs, crocodilians, pterosaurs and their close relatives form the highly diverse clade Archosauriformes. Archosauriforms have a deep evolutionary history, originating in the late Permian, prior to the end-Permian mass extinction, and radiating in the Triassic to dominate Mesozoic ecosystems. However, the origins of this clade and its extraordinarily successful body plan remain obscure. Here, we describe an exceptionally preserved fossil skull from the Lower Triassic of Brazil, representing a new species, Teyujagua paradoxa, transitional in morphology between archosauriforms and more primitive reptiles. This skull reveals for the first time the mosaic assembly of key features of the archosauriform skull, including the antorbital and mandibular fenestrae, serrated teeth, and closed lower temporal bar. Phylogenetic analysis recovers Teyujagua as the sister taxon to Archosauriformes, and is congruent with a two-phase model of early archosauriform evolution, in response to two mass extinctions occurring at the end of the Guadalupian and the Permian.


Mandibular shape correlates of tooth fracture in extant Carnivora: implications to inferring feeding behaviour of Pleistocene predators

Abstract: Percentages of tooth fracture and mandible shape are robust predictors of feeding habits in Carnivora. If these parameters co-vary above the species level, more robust palaeobiological inferences could be made on fossil species. A test of association is presented between mandible shape and tooth fracture in a subset of extant carnivorans together with large Pleistocene fossil predators from Rancho La Brea (Canis dirus, Panthera atrox, and Smilodon fatalis). Partial least square (PLS) and comparative methods are employed to validate co-variation of these two parameters in extant carnivorans. Association between mandible shape and percentage of tooth fracture is strongly supported, even if both blocks of data exhibit a phylogenetic signal to a different degree. Dietary adaptations drive shape/fracture co-variation in extant species, although no significant differences occur in the PLS scores between carnivores and bone/hard food consumers. The fossil species project into PLS morphospace as outliers. Their position suggests a unique feeding behaviour. The increase in the size of prey, together with consumption of skin and hair from carcasses in a cold environment, might have generated unusual tooth breakage patterns in large predators from Rancho La Brea. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 70–80.


Recent inner ear specialization for high-speed hunting in cheetahs

Abstract: The cheetah, Acinonyx jubatus, is the fastest living land mammal. Because of its specialized hunting strategy, this species evolved a series of specialized morphological and functional body features to increase its exceptional predatory performance during high-speed hunting. Using high-resolution X-ray computed micro-tomography (μCT), we provide the first analyses of the size and shape of the vestibular system of the inner ear in cats, an organ essential for maintaining body balance and adapting head posture and gaze direction during movement in most vertebrates. We demonstrate that the vestibular system of modern cheetahs is extremely different in shape and proportions relative to other cats analysed (12 modern and two fossil felid species), including a closely-related fossil cheetah species. These distinctive attributes (i.e., one of the greatest volumes of the vestibular system, dorsal extension of the anterior and posterior semicircular canals) correlate with a greater afferent sensitivity of the inner ear to head motions, facilitating postural and visual stability during high-speed prey pursuit and capture. These features are not present in the fossil cheetah A. pardinensis, that went extinct about 126,000 years ago, demonstrating that the unique and highly specialized inner ear of the sole living species of cheetah likely evolved extremely recently, possibly later than the middle Pleistocene.

high-speed hunting
cheetah
vestibular system
proportion
stability


A modular hierarchy-based theory of the chemical origins of life based on molecular complementarity.

Abstract: Albert Szent-Gyorgyi once defined discovery as seeing what everyone else sees and thinking what no one else thinks. I often find that phenomena that are obvious to other people are not obvious to me. Molecular complementarity is one of these phenomena: while rare among any random set of compounds, it is ubiquitous in living systems. Because every molecule in a living system binds more or less specifically to several others, we now speak of "interactomes". What explains the ubiquity of molecular complementarity in living systems? What might such an explanation reveal about the chemical origins of life and the principles that have governed its evolution? Beyond this, what might complementarity tell us about the optimization of integrated systems in general? My research combines theoretical and experimental approaches to molecular complementarity relating to evolution from prebiotic chemical systems to superorganismal interactions. Experimentally, I have characterized complementarity involving specific binding between small molecules and explored how these small-molecule modules have been incorporated into macromolecular systems such as receptors and transporters. Several general principles have emerged from this research. Molecules that bind to each other almost always alter each other's physiological effects; and conversely, molecules that have antagonistic or synergistic physiological effects almost always bind to each other. This principle suggests a chemical link between biological structure and function. Secondly, modern biological systems contain an embedded molecular paleontology based on complementarity that can reveal their chemical origins. This molecular paleontology is often manifested through modules involving small, molecularly complementary subunits that are built into modern macromolecular structures such as receptors and transporters. A third principle is that complementary modules are conserved and repurposed at every stage of evolution. Molecular complementarity plays critical roles in the evolution of chemical systems and resolves a significant number of outstanding problems in the emergence of complex systems. All physical and mathematical models of organization within complex systems rely upon nonrandom linkage between components. Molecular complementarity provides a naturally occurring nonrandom linker. More importantly, the formation of hierarchically organized stable modules vastly improves the probability of achieving self-organization, and molecular complementarity provides a mechanism by which hierarchically organized stable modules can form. Finally, modularity based on molecular complementarity produces a means for storing and replicating information. Linear replicating molecules such as DNA or RNA are not required to transmit information from one generation of compounds to the next: compositional replication is as ubiquitous in living systems as genetic replication and is equally important to its functions. Chemical systems composed of complementary modules mediate this compositional replication and gave rise to linear replication schemes. In sum, I propose that molecular complementarity is ubiquitous in living systems because it provides the physicochemical basis for modular, hierarchical ordering and replication necessary for the evolution of the chemical systems upon which life is based. I conjecture that complementarity more generally is an essential agent that mediates evolution at every level of organization.

chemical origin
molecular complementarity
molecular paleontology


Abstract: Easily-accessible digital palaeontological databases-a new perspective for the storage of palaeontological information Techniques that allow to render diverse types of palaeontological data as publicly available internet resources are described. In order to develop an easily accessible digital palaeontological database, three steps should be followed: (1) digitization of the studied specimens, (2) acquisition of morphometric data, and (3) contribution of the data to open and searchable geoinformatic (palaeontological) databases. Digital data should be submitted to internet databases that allow a user to fetch various types of information from dispersed sources (semantic web services).

digital palaeontological databases-a
digitization
new perspective
storage


Correlation of boron isotopic composition with ultrastructure in the deep‐sea coral Lophelia pertusa: Implications for biomineralization and paleo‐pH

Abstract: Using the CRPG‐CNRS Cameca 1270 ion microprobe facility, we have measured boron isotopic compositions (11B/10B) in different ultrastructural components of the deep‐sea aragonitic scleractinian coral Lophelia pertusa. We observe a systematic difference in B isotopic composition between the Early Mineralization Zone (EMZ) and adjacent fibrous skeleton. In EMZ the measured δ11B values are consistently low. Fibrous aragonite is characterized by systematically higher δ11B values but also displays B isotopic heterogeneity associated with specific growth bands in the calyx wall. The magnitude of the observed B isotopic variations cannot be explained by changes in environmental conditions and is likely caused by biological processes involved in the biomineralization of new skeleton, i.e., “vital” effects. The observed B isotopic variations are opposite to the predictions of geochemical models for vital effects. These models are based on the idea that stable isotopic fractionations (including C and O) in coral skeleton are driven by changes in pH of the fluid from which the skeleton is presumed to precipitate. Our data indicate that pH variations are not responsible for the observed stable isotopic fractionations. Geochemical models therefore do not provide an adequate framework within which to understand coral skeletal formation. Without a better understanding of these processes the use of B isotopic composition to reconstruct paleo‐pH variations in the oceans must be considered problematic, at least as far as Lophelia pertusa is concerned.

boron
isotopic composition
biomineralization


A New Caenagnathid (Dinosauria: Oviraptorosauria) from the Horseshoe Canyon Formation of Alberta, Canada, and a Reevaluation of the Relationships of Caenagnathidae

Abstract: ABSTRACT Our understanding of caenagnathids has benefited from recent discoveries, including nearly complete skeletons from the Hell Creek Formation of Montana. However, their phylogenetic relationships remain unclear. A new specimen from the Horseshoe Canyon Formation of Alberta has implications for the phylogeny and paleobiology of these creatures. The partial skeleton is articulated and includes a mandible, a full cervical and dorsal series of vertebrae, a right pectoral girdle and arm, a sternum, gastralia, a partial ilium, and a partial hind limb. The mandible is edentulous and the articular ridge is intermediate in form between Caenagnathus collinsi and Chirostenotes pergracilis. The neck is long and composed of at least 11 well-pneumatized cervical vertebrae with fused cervical ribs. The dorsal ribs have finger-like uncinate processes dissimilar in shape to those of other oviraptorosaurs. The pectoral girdle is large and typically maniraptoran, except that the glenoid of the scapulocoracoid faces laterally instead of posteroventrally. The arm is well muscled and can be interpreted to have been a pennibrachium, as indicated by ulnar papillae on the ulna. The manus is characterized by a short first metacarpal but an elongate phalanx I-1 and oviraptorid-like phalangeal proportions in the second digit. These and other features indicate that the specimen represents a new taxon, Apatoraptor pennatus, gen. et sp. nov. Phylogenetic analysis resolves the complicated relationships of Caenagnathidae and allows the evolution of display features to be traced throughout Oviraptorosauria.


Decay of vertebrate characters in hagfish and lamprey (Cyclostomata) and the implications for the vertebrate fossil record

Abstract: The timing and sequence of events underlying the origin and early evolution of vertebrates remains poorly understood. The palaeontological evidence should shed light on these issues, but difficulties in interpretation of the non-biomineralized fossil record make this problematic. Here we present an experimental analysis of decay of vertebrate characters based on the extant jawless vertebrates (Lampetra and Myxine). This provides a framework for the interpretation of the anatomy of soft-bodied fossil vertebrates and putative cyclostomes, and a context for reading the fossil record of non-biomineralized vertebrate characters. Decay results in transformation and non-random loss of characters. In both lamprey and hagfish, different types of cartilage decay at different rates, resulting in taphonomic bias towards loss of ‘soft’ cartilages containing vertebrate-specific Col2α1 extracellular matrix proteins; phylogenetically informative soft-tissue characters decay before more plesiomorphic characters. As such, synapomorphic decay bias, previously recognized in early chordates, is more pervasive, and needs to be taken into account when interpreting the anatomy of any non-biomineralized fossil vertebrate, such as Haikouichthys, Mayomyzon and Hardistiella.


Weakening and strengthening of the Indian monsoon during Heinrich events and Dansgaard-Oeschger oscillations

Abstract: The Dansgaard-Oeschger oscillations and Heinrich events described in North Atlantic sediments and Greenland ice are expressed in the climate of the tropics, for example, as documented in Arabian Sea sediments. Given the strength of this teleconnection, we seek to reconstruct its range of environmental impacts. We present geochemical and sedimentological data from core SO130-289KL from the Indus submarine slope spanning the last similar to 80 kyr. Elemental and grain size analyses consistently indicate that interstadials are characterized by an increased contribution of fluvial suspension from the Indus River. In contrast, stadials are characterized by an increased contribution of aeolian dust from the Arabian Peninsula. Decadal-scale shifts at climate transitions, such as onsets of interstadials, were coeval with changes in productivity-related proxies. Heinrich events stand out as especially dry and dusty events, indicating a dramatically weakened Indian summer monsoon, potentially increased winter monsoon circulation, and increased aridity on the Arabian Peninsula. This finding is consistent with other paleoclimate evidence for continental aridity in the northern tropics during these events. Our results strengthen the evidence that circum-North Atlantic temperature variations translate to hydrological shifts in the tropics, with major impacts on regional environmental conditions such as rainfall, river discharge, aeolian dust transport, and ocean margin anoxia. Key Points Intensity of Indian monsoon is traced with geochemical and grain size analyses of sediments Fluvial versus aeolian sediment input to Arabian Sea mimics DO oscillations During Heinrich events the Indian monsoon weakened distinctly

monsoon
heinrich event
dansgaard-oeschger oscillation


The seasonal water temperature cycle in the Arctic Dicksonfjord (Svalbard) during the Holocene Climate Optimum derived from subfossil Arctica islandica shells

Abstract: Future climate change will have significant effects on ecosystems worldwide and on polar regions in particular. Hence, palaeo-environmental studies focussing on the last warmer-than-today phase (i.e. the early Holocene) in higher latitudes are of particular importance to understand climate development and its potential impact in polar systems. Molluscan bivalve shells constitute suitable bio-archives for high-resolution palaeo-environmental reconstructions. Here, we present a first reconstruction of early Holocene seasonal water temperature cycle in an Arctic fjord based on stable oxygen isotope (δ18Oshell) profiles in shells of Arctica islandica (Bivalvia) from raised beach deposits in Dicksonfjorden, Svalbard, dated at 9954–9782 cal. yr BP. Reconstructed maximum and minimum bottom water temperatures for the assumed shell growth period between April and August of 15.2°C and 2.8°C imply a seasonality of about 12.4°C for the early Holocene. In comparison to modern temperatures, this indicates that average temperature declined by 6°C and seasonality narrowed by 50%. This first palaeo-environmental description of a fjord setting during the Holocene Climate Optimum at Spitsbergen exceeds most previous global estimates (+1–3°C) but confirms studies indicating an amplified effect (+4–6°C) at high northern latitudes.

seasonality
water temperature cycle
holocene climate optimum


Cranial osteology of the Middle Jurassic (Callovian) Martillichthys renwickae (Neopterygii, Pachycormiformes) with comments on the evolution and ecology of edentulous pachycormiforms

Abstract: Our understanding of the ecology and phylogenetic relationships of Pachycormiformes, a group of Mesozoic stem teleosts including the iconic Leedsichthys, has often been hindered by a lack of comprehensive morphological information. Micro‐CT scanning of an articulated, although flattened, cranium of the edentulous Martillichthys renwickae from the Middle Jurassic (Callovian) Oxford Clay of the UK reveals previously unknown internal details of the most complete suspension‐feeding pachycormiform skull known, including the palate, braincase and branchial skeleton. The latter preserves gill rakers with elongate, pointed projections similar to those of Asthenocormus, in contrast to the finer fimbriations associated with Leedsichthys. We also reinterpret some previously described features, including dermal bone patterns of the snout, skull roof and lower jaw, and the morphology of the ventral hyoid arch. These new anatomical data reinforce the phylogenetic placement of Martillichthys as part of the Jurassic clade of edentulous pachycormiforms. The elongate skull geometry of these Jurassic taxa is strikingly similar to that of Ohmdenia, the sister taxon to edentulous pachycormiforms, but contrasts sharply with the morphology of the Late Cretaceous edentulous pachycormiform Bonnerichthys, raising questions over the phylogenetic relationships among these taxa. Most significantly, Martillichthys shows specialized characters with a restricted phylogenetic distribution among suspension‐feeding pachycormiforms, including the distinctive gill rakers and a greatly extended occipital stalk. Our analysis of Martillichthys supports past interpretations of a close relationship with Asthenocormus, and provides a model for interpreting the less complete remains of other members of this enigmatic group of fishes.

martillichthys renwickae
pachycormiformes
edentulous pachycormiform


A new Permian temnospondyl with Russian affinities from South America, the new family Konzhukoviidae, and the phylogenetic status of Archegosauroidea

Abstract: A new Permian temnospondyl from South America is described and considered to represent a new species – Konzhukovia sangabrielensis sp. nov. – of the genus Konzhukovia previously recorded exclusively from Russia. It consists of the anterior half and partial right side of the skull roof and palate. A comprehensive phylogenetic analysis was performed with several archegosauroids and other well-supported groups of temnospondyls in order to access the affinities of the new Brazilian species and test the monophyly of Archegosauroidea. Archegosauroidea was not recovered as a monophyletic group, comprising successive paraphyletic taxa. The only monophyletic group of ‘archegosauroids’ is the ‘Tryphosuchinae’ (in a sister-group relationship with Stereospondyli), composed of Tryphosuchus paucidens, Konzhukovia vetusta, K. tarda and K. sangabrielensis. As the diagnosis of T. paucidens is unclear and based on incomplete material, nested among three species of Konzhukovia, we consider this taxon to be a nomen dubium and purge it from the strict consensus tree. An alternative solution would be to erect a new taxonomic combination for T. paucidens. In order to solve these taxonomic problems, it is necessary to discover more complete material with a clear set of diagnostic characters, to either revalidate this taxon or provide a new combination for it. The phylogenetic results support the erection of a new family – Konzhukoviidae – to replace ‘Tryphosuchinae’ and accommodate Konzhukovia vetusta, K. tarda and K. sangabrielensis, the new Brazilian species basal to the Russian forms. An early diverging konzhukoviid in Gondwana leads to interesting insights regarding the evolution of the new family, stereospondyl origins, their early diversification and their palaeobiogeographical patterns of distribution. http://zoobank.org/urn:lsid:zoobank.org:pub:4772DC7E-C427-4F5F-89FD-9E68E3B0BFD5

new permian temnospondyl
south america
archegosauroidea


The last 18 kyr fluctuations in Norwegian sea surface conditions and implications for the magnitude of climatic change: Evidence from the North Sea

Abstract: A combined record of three cores spanning the last 18 kyr from the northern North Sea is investigated for content of benthic and planktonic foraminifera and stable oxygen isotopes. The paleoenvironmental development through this time period shows an early deglaciation (18–14.4 ka) and the Younger Dryas (12.7–11.5 ka) characterized by arctic/polar conditions and increased ice rafting in the Norwegian Channel. During the Bolling-Allerod period, warm sea surface temperature (9°C) conditions similar to present conditions are inferred, while bottom waters stayed cold (0–1°C) with normal salinity. The Bolling-Allerod period is interrupted twice at 13.9–13.6 ka (Older Dryas) and at 13.0–12.8 ka (Inter-Allerod Cooling Period) by reductions in sea surface temperatures and increased sea ice cover. The beginning of the Holocene period is marked by increases in surface and bottom water temperature. Superimposed on the broad climatic changes through the Holocene, a series of short-lived oscillations in the ocean circulation are recorded. The amplitude of these Holocene events appears larger in the early Holocene (prior to 8 ka) than compared with the remaining part of the Holocene. This amplification can possibly be attributed to a general increased freshwater budget in the North Atlantic at this time during the final stages of the deglaciation of the Laurentide and Scandinavian ice sheets.

climatic change
north sea
early holocene


Abstract:
Filipiak, P. & Zaton, M. 2010: Plant and animal cuticle remains from the Lower Devonian of southern Poland and their palaeoenvironmental significance. Lethaia, Vol. 44, pp. 397–409.

Assemblages of plant and arthropod remains are reported from the Lower Devonian clastic deposits of the Upper Silesian and Malopolska blocks in southern Poland. Most of the plant and animal remains are palynologically dated as Pragian–Emsian/Eifelian. The plant material comprises higher plant cuticles with stomata classified as Drephanophycus and Sawdonia, and more enigmatic remains (nematophytes) classified as Nematothallus, Cosmochlaina and tubular banded tubes. They are associated with abundant and diverse miospores. Animal remains consist of eurypterid respiratory organs, the morphology of which may presumably point to their advance physiological properties, and cuticular remains of eurypterid and probably scorpion origin, as well as some remains of unknown affinity. The presence of such mixed assemblages in the Lower Devonian of Poland indicate marginal-marine and/or alluvial environments spreading in the southern margin of the Old Red Continent. The dominance of land-derived plant remains and simultaneous scarcity of marine acritarchs indicate that the environment was very weakly influenced by marine conditions. If nematophytes were really related to extant liverworts, as suggested by some workers, they, together with the other associated spore-producing plants, may strongly indicate moist environmental conditions, which may have offered suitable habitats for temporary eurypterid migrations onto land. □Cuticles, eurypterids, Lower Devonian, nematophytes, Poland, spores.

animal cuticle
southern poland
palaeoenvironmental significance


Intraspecific variation in cephalopod conchs changes during ontogeny: perspectives from three-dimensional morphometry of Nautilus pompilius

Abstract:
Abstract.
 Intraspecific variation of organisms is of great importance to correctly carry out taxonomic work, which is a prerequisite for key disciplines in paleontology such as community paleoecology, biostratigraphy, and biogeography. However, intraspecific variation is rarely studied in ectocochleate cephalopods (ammonoids and nautiloids), for which an excessive number of taxa was established during the past centuries. Because intraspecific variation of fossilized organisms suffers from various biases (time averaging and taphonomy), an extant example is needed for actualistic comparison. We applied 3D morphometry to 93 specimens of Nautilus pompilius from three different geographic populations. This data set was used to examine the intraspecific variation throughout ontogeny in detail. Although there are slight differences between the populations as well as some measurement biases, a common pattern of intraspecific variation appears to be present. High variation in morphometric variables appears early in ontogeny and then decreases gradually in the following ontogenetic stages. Subsequently, the variation shows an increase again before maturity until a sharp increase or decrease occurs toward the end of ontogeny. Comparison with intraspecific variation of ammonoids and belemnites illustrated that some groups have ontogenetic patterns of intraspecific variation that are similar to that of N. pompilius. This implies that the abovementioned ontogenetic pattern of intraspecific variation might be common in some major cephalopod clades.

morphometry
pompilius
intraspecific variation


Dental and tarsal morphology of the European Paleocene/Eocene "condylarth" mammal Microhyus

Abstract: New dental and postcranial remains of the alleged louisinine hyopsodontid "condylarth" Microhyus from the European Paleocene/Eocene transition are described, and prompt a reevaluation of the genus. New specimens belonging to Microhyus musculus from Dormaal (MP7, Belgium) provide the first evidence of the lower dentition of the type species. We describe M. musculus? from Pourcy (MP7, France) and cf. Microhyus sp. from Berru (MP6a, France). A rich original assemblage of M. reisi from Silveirinha (MP7, Portugal) allows a detailed description of the morphological dental variation within that species. Well-preserved astragali and calcanei from Silveirinha can be confidently attributed to Microhyus reisi. Functional analysis of these elements suggests that Microhyus was a terrestrial mammal capable of rapid running or jumping. The pedal morphology of Microhyus is very similar to that of Paschatherium. These louisinines share some derived characters with the hyopsodontids Apheliscus and Haplomylus (e.g., the occurrence of a cotylar fossa on the astragalus) but they differ from Hyopsodus. Therefore, in view of the pedal morphology alone, the hyopsodontids may be polyphyletic. Given the dental similarities between Microhyus and the early representatives of the order Macroscelidea, we compared the tarsal morphology of louisinines with that of modern macroscelidids (Paleogene tarsal remains are currently unknown for this group). Macroscelidids and louisinines present some similarities in their astragalar morphology; however, the macroscelidid astragalus appears to be too specialized to be compared with that of Microhyus and Paschatherium.

tarsal morphology
european paleocene
condylarth


Development and trunk segmentation of early instars of a ptychopariid trilobite from Cambrian Stage 5 of China

Abstract: Many three-dimensionally preserved exoskeletons found from the middle Cambrian (Stage 5) Gaotai Formation in Guizhou, southern China, have been assigned to the ptychopariid trilobite Gunnia sp. They represent mainly a series of early instars, exhibiting some delicate structures and morphological variation associated with their trunk segmentation and early development. Morphometric and statistical analyses indicate that the transverse joint appears to occur with the full growth of the third axial ring of the protopygidium, which increases in size much more rapidly than its corresponding protocephalon with growth. The ‘one by one' sequential release of thoracic segments from a transitory pygidium does not progress exactly in accordance with the development of the pygidial axis, whose axial rings increase at a relatively faster rate, and an ‘immature ring' always appears initially at the rear end of the axis. These new data set up a testable model for revealing trilobite segmentation and provide fresh insights into the development, evolution and taphonomic surroundings associated with the Cambrian trilobites.

trunk segmentation
early instar
trilobite


How to date a crocodile: estimation of neosuchian clade ages and a comparison of four time‐scaling methods

Abstract: Clade ages within the crocodylomorph clade Neosuchia have long been debated. Molecular and morphological studies have yielded remarkably divergent results. Despite recent advances, there has been no comprehensive relative comparison of the major time calibration methods available to estimate clade ages based on morphological data. We used four methods (cal3, extended Hedman, smoothed ghost lineage analysis (sGLA) and the fossilized birth–death model (FBD)) to date clade ages derived from a published crocodylomorph supertree and a new neosuchian phylogeny. All time‐scaling methods applied here agree on the origination of Neosuchia during the Late Triassic or Early Jurassic, and the presence of the major extant eusuchian groups (Crocodyloidea, Gavialoidea, Alligatoroidea and Caimaininae) by the end of the Late Cretaceous. The number of distinct lineages present before the K/Pg boundary is less certain, with support for two competing scenarios in which Crocodylinae, Tomistominae and Diplocynodontinae either: (1) diverged from other eusuchian lineages before the K/Pg boundary; or (2) evolved during a ‘burst’ of diversification after the K/Pg event. Cal3 and FBD proved to be the most suitable methods for time‐scaling phylogenetic trees dominated by fossil taxa. Extended Hedman estimates are substantially older than the others, with larger standard deviations and a strong sensitivity to taxon sampling and topological changes; sGLA has similar problems. We conclude that a detailed understanding of phylogenetic relationships, tree reconstruction methods, and good taxonomic coverage (in particular the inclusion of the oldest taxon in each clade) is essential when evaluating the results of such dating analyses.


Terminal Cretaceous Extinctions in the Hell Creek Area, Montana: Compatible with Catastrophic Extinction

Abstract: Inaccurate stratigraphic correlations in the Hell Creek area, Montana, have led to the assumption that transitional vertebrate faunas (Bug Creek Anthills) exist in the latest Cretaceous, refuting a catastrophic turnover at the Cretaceous-Tertiary boundary. Establishment of the transitional faunas in Paleocene channels that cut down through the Cretaceous-Tertiary boundary renders the terrestrial faunal record compatible with the marine record and with catastrophic extinction.

hell creek area
montana
catastrophic extinction


Late Silurian reef development in the Baltic Sea

Abstract: Abstract In the Baltic Sea, reef structures are common in the Ordovician and Silurian sedimentary bedrock. Palaeozoic reef development culminated in the Silurian when several successive reef barriers developed. The present investigation has revealed new reef structures in the upper Silurian sedimentary bedrock. Two new biostromes, E1 and E2, have been found in the Ludlovian Eke Beds, east of Gotland. The biostromes trend in a more or less east-west direction and can be traced across the northern part of the Baltic Sea. In the Pridolian, two reef-like barriers, named B5 and B6, occur at the boundary to the Devonian. The lower barrier, B5, is found to the south of the younger B6 barrier. This indicates that a transgression occurred between the formation of the two barriers. A tentative reconstruction of the Pridolian bay suggests that the coast shifted from a more east-west direction in the Ludlovian to a more north-easterly to south-westerly direction in the Pridolian. Bioherms are commonly associated with the Eke biostromes and the upper Pridolian reef-like barriers. The bioherms occur on the seaward side of the larger reef structures, on the biohermal slope. Patch-reefs also occur on the biohermal slope but they are more common on the landward (lagoonal) side of the barriers.


Blade and bladelet production at Hohle Fels Cave, AH IV in the Swabian Jura and its importance for characterizing the technological variability of the Aurignacian in Central Europe

Abstract: Hohle Fels Cave in the Ach Valley of Southwestern Germany exhibits an Aurignacian sequence of 1 m thickness within geological horizons (GH) 6–8. The deposition of the layers took place during mild and cold phases between at least 42 ka (GI 10) and 36 ka calBP (GI 7). We present below a technological study of blade and bladelet production from AH IV (GH 7) at Hohle Fels. Our analyses show that blade manufacture is relatively constant, while bladelet production displays a high degree of variability in order to obtain different blanks. Knappers used a variety of burins as cores to produce fine bladelets. The results reveal a new variant of the Aurignacian in the Swabian Jura primarily characterized by the production of bladelets and microliths from burin-cores. The artefacts from the Swabian Aurignacian are technologically and functionally more diverse than earlier studies of the Geißenklösterle and Vogelherd sequences have suggested. The technological analyses presented here challenge the claim that the typo-chronological system from Southwestern Europe can be applied to the Central European Aurignacian. Instead, we emphasize the impact of technological and functional variables within the Aurignacian of the Swabian Jura.

bladelet production
swabian jura
aurignacian


Spatial sampling heterogeneity limits the detectability of deep time latitudinal biodiversity gradients

Abstract: The latitudinal biodiversity gradient (LBG), in which species richness decreases from tropical to polar regions, is a pervasive pattern of the modern biosphere. Although the distribution of fossil occurrences suggests this pattern has varied through deep time, the recognition of palaeobiogeographic patterns is hampered by geological and anthropogenic biases. In particular, spatial sampling heterogeneity has the capacity to impact upon the reconstruction of deep time LBGs. Here we use a simulation framework to test the detectability of three different types of LBG (flat, unimodal and bimodal) over the last 300 Myr. We show that heterogeneity in spatial sampling significantly impacts upon the detectability of genuine LBGs, with known biodiversity patterns regularly obscured after applying the spatial sampling window of fossil collections. Sampling-standardization aids the reconstruction of relative biodiversity gradients, but cannot account for artefactual absences introduced by geological and anthropogenic biases. Therefore, we argue that some previous studies might have failed to recover the ‘true’ LBG type owing to incomplete and heterogeneous sampling, particularly between 200 and 20 Ma. Furthermore, these issues also have the potential to bias global estimates of past biodiversity, as well as inhibit the recognition of extinction and radiation events.

sampling
heterogeneity
deep time
latitudinal biodiversity gradient


Climate Sensitivity on Geological Timescales Controlled by Nonlinear Feedbacks and Ocean Circulation

Abstract: Climate sensitivity is a key metric used to assess the magnitude of global warming given increased CO2 concentrations. The geological past can provide insights into climate sensitivity; however, on timescales of millions of years, factors other than CO2 can drive climate, including paleogeographic forcing and solar luminosity. Here, through an ensemble of climate model simulations covering the period 150–35 million years ago, we show that climate sensitivity to CO2 doubling varies between ∼3.5 and 5.5 °C through this time. These variations can be explained as a nonlinear response to solar luminosity, evolving surface albedo due to changes in ocean area, and changes in ocean circulation. The work shows that the modern climate sensitivity is relatively low in the context of the geological record, as a result of relatively weak feedbacks due to a relatively low CO2 baseline, and the presence of ice and relatively small ocean area in the modern continental configuration.

ocean circulation
ensemble
climate sensitivity


The earliest segmental sternum in a Permian synapsid and its implications for the evolution of mammalian locomotion and ventilation

Abstract: The sternum is a stabilizing element in the axial skeleton of most tetrapods, closely linked with the function of the pectoral girdle of the appendicular skeleton. Modern mammals have a distinctive sternum characterized by multiple ossified segments, the origins of which are poorly understood. Although the evolution of the pectoral girdle has been extensively studied in early members of the mammalian total group (Synapsida), only limited data exist for the sternum. Ancestrally, synapsids exhibit a single sternal element and previously the earliest report of a segmental sternum in non-mammalian synapsids was in the Middle Triassic cynodont Diademodon tetragonus. Here, we describe the well-preserved sternum of a gorgonopsian, a group of sabre-toothed synapsids from the Permian. It represents an ossified, multipartite element resembling the mammalian condition. This discovery pulls back the origin of the distinctive “mammalian” sternum to the base of Theriodontia, significantly extending the temporal range of this morphology. Through a review of sternal morphology across Synapsida, we reconstruct the evolutionary history of this structure. Furthermore, we explore its role in the evolution of mammalian posture, gait, and ventilation through progressive regionalization of the postcranium as well as the posteriorization of musculature associated with mammalian breathing.


Ancient DNA and multimethod dating confirm the late arrival of anatomically modern humans in southern China

Abstract: Significance Genetic studies show the founders of all living non-African populations expanded from Africa ca. 65 to 45 ka. This “late dispersal” model has been challenged by the discovery of isolated AMHs at caves in southern China suggested as early as ca. 120 ka. We assessed the age of early AMH fossils from five caves in this region using ancient DNA analysis and a multimethod geological dating strategy. We found they were much younger than previously suggested, with some remains dating to the Holocene owing to the complex depositional history at these subtropical caves. Current evidence shows AMHs settled southern China within the timeframe set by molecular data of less than ca. 50 to 45 ka and no earlier. The expansion of anatomically modern humans (AMHs) from Africa around 65,000 to 45,000 y ago (ca. 65 to 45 ka) led to the establishment of present-day non-African populations. Some paleoanthropologists have argued that fossil discoveries from Huanglong, Zhiren, Luna, and Fuyan caves in southern China indicate one or more prior dispersals, perhaps as early as ca. 120 ka. We investigated the age of the human remains from three of these localities and two additional early AMH sites (Yangjiapo and Sanyou caves, Hubei) by combining ancient DNA (aDNA) analysis with a multimethod geological dating strategy. Although U–Th dating of capping flowstones suggested they lie within the range ca. 168 to 70 ka, analyses of aDNA and direct AMS 14C dating on human teeth from Fuyan and Yangjiapo caves showed they derive from the Holocene. OSL dating of sediments and AMS 14C analysis of mammal teeth and charcoal also demonstrated major discrepancies from the flowstone ages; the difference between them being an order of magnitude or more at most of these localities. Our work highlights the surprisingly complex depositional history recorded at these subtropical caves which involved one or more episodes of erosion and redeposition or intrusion as recently as the late Holocene. In light of our findings, the first appearance datum for AMHs in southern China should probably lie within the timeframe set by molecular data of ca. 50 to 45 ka.

modern human
southern china
cave
ancient dna


HOW DO GEOLOGICAL SAMPLING BIASES AFFECT STUDIES OF MORPHOLOGICAL EVOLUTION IN DEEP TIME? A CASE STUDY OF PTEROSAUR (REPTILIA: ARCHOSAURIA) DISPARITY

Abstract: A fundamental contribution of paleobiology to macroevolutionary theory has been the illumination of deep time patterns of diversification. However, recent work has suggested that taxonomic diversity counts taken from the fossil record may be strongly biased by uneven spatiotemporal sampling. Although morphological diversity (disparity) is also frequently used to examine evolutionary radiations, no empirical work has yet addressed how disparity might be affected by uneven fossil record sampling. Here, we use pterosaurs (Mesozoic flying reptiles) as an exemplar group to address this problem. We calculate multiple disparity metrics based upon a comprehensive anatomical dataset including a novel phylogenetic correction for missing data, statistically compare these metrics to four geological sampling proxies, and use multiple regression modeling to assess the importance of uneven sampling and exceptional fossil deposits (Lagerstätten). We find that range‐based disparity metrics are strongly affected by uneven fossil record sampling, and should therefore be interpreted cautiously. The robustness of variance‐based metrics to sample size and geological sampling suggests that they can be more confidently interpreted as reflecting true biological signals. In addition, our results highlight the problem of high levels of missing data for disparity analyses, indicating a pressing need for more theoretical and empirical work.

sampling
pterosaur
disparity metric
phylogenetic correction


The pectoral girdle and forelimb of the basal theropod Herrerasaurus ischigualastensis

Abstract: ABSTRACT New specimens of Herrerasaurus ischigualastensis shed light on the structure and function of the pectoral girdle and forelimb in early theropod dinosaurs. As in tetanurian theropods, the scapulocoracoid has a broadly expanded acromion and strap-shaped scapular blade. The forelimb is less than one-half the length of the hind-limb and is specialized for prey capture and manipulation. The short proximal segments of the forelimb provide mechanical advantage and are marked by prominent tuberosities. The well-ossified carpus is divided into two functional units, one composed of the radiale and ulnare and the other composed of a centrale and distal carpals, and is designed functionally for dorsoventral extension and flexion of the manus against the forearm. The manus is longer than the humerus, radius, or ulna and is specialized for grasping and raking, as shown by the marked metacarpal extensor depressions, long penultimate phalanges, and trenchant unguals in digits I–III. Upon flexion or extension, th...

pectoral girdle
forelimb
herrerasaurus ischigualastensis