New aspects of the paleobiogeography of early alligatoroids - a new alligator from the Upper Cretaceous of Hungary.
According to the generally accepted explanation
, alligatoroids first appeared in North America during the Late Cretaceous and soon after migrated to Europe from the direction of the Atlantic Ocean. It is supported by the occurrence of two phylogenetically basal species, Leidyosuchus canadensis
and Deinosuchus rugosus
in the Campanian and Maastrichtian sediments of North America.
In Europe at least two Late Cretaceous alligatoroid taxa have been described: Acynodon and Musturzabalsuchus , discovered in the area of the former Mediterranean. Recently the Hungarian dinosaur bearing locality in the Bakony Mountains has yielded several isolated alligatoroid mandible remains. Some of the autapomorphic characters of the group are present on these remains (laterally shifted foramen aërum on the articular) and comparison with other Late Cretaceous taxa suggests that the Hungarian alligatoroid is probably a new taxon. The biogeographical importance of the discovery is given by the age of the material which is Santonian, so far the oldest alligatoroid remains ever reported. Some of the characters on the dentary (such as the separated 3rd and 4th alveoli) indicate that the Hungarian alligatoroid is more closely related to the derived, blunt-snouted alligatorids like Brachychampsa, Stangerochampsa and Acynodon than to the basal Alligatoroidea group (including Leidyosuchus and Musturzabalsuchus) . These results question the North American origin of Alligatoroidea as by this new discovery the oldest member of the group is presently known from Europe, nevertheless this taxon morphologically seems to be a derived form.
JEAN-CLAUDE RAGE1 & ZBIGNIEW SZYNDLAR2
1Département Histoire de la Terre, Muséum national d’Histoire naturelle, Paris, France (firstname.lastname@example.org); 2Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Krakow, Poland (SZYNDLAR@isez.pan.krakow.pl)
The strange Eocene snake Cadurceryx.
Snakes are elongate and very flexible animals. However, in erycine Boidae (‘sand boas’), the posterior part of the tail is not flexible. The vertebrae of this portion of the vertebral column of erycines are markedly shortened and they bear additional apophyses that form extra intervertebral articulations, in fact non-flexible joints. A snake from the Eocene, Cadurceryx filholi
, has posterior caudal vertebrae similar to those of extant Erycinae; but in this snake, additional apophyses are present also on more anterior vertebrae: they are present in the whole caudal region and on vertebrae from the trunk. In the original description of Cadurceryx
, it was presumed that, aside from the caudal region, only the posteriormost trunk vertebrae were provided with additional apophyses. But, new material has shown that the vertebral column of Cadurceryx
was entirely composed of vertebrae with additional apophyses
, except perhaps the anteriormost vertebrae (‘cervical’ region).
A living snake, the African Mehelya (Colubridae), has rather similar trunk vertebrae. It displays usual habits and movements of snakes, but its additional apophyses do not form additional intervertebral articulations. On the contrary, in Cadurceryx , the apophyses are comparatively longer and provided extra intervertebral articulations in at least a part of the trunk region. Therefore, the movements of Cadurceryx were likely limited to a degree that cannot be estimated. Cadurceryx was first assigned to the erycine Boidae, but its trunk vertebrae cast doubt on this referral. No skull bone may be confidently attributed to this snake and its affinities remain enigmatic.
Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, United Kingdom. (email@example.com )
Understanding the biomechanics of bird skulls using Finite Element Analysis.
How well do our Finite Element model results reflect reality? We will never be able to definitively answer this question in extinct animals, but we can phylogenetically and functionally bracket extinct animal FE-models with data from living animals detailing (a) how well FE-models replicate experimentally recorded in-vivo/vitro bone strain; and (b) which parameters matter the most for accuracy. FE-model validation against bone strain data is currently underway for macaques and crocodiles. To close the phylogenetic bracket around dinosaurs and pterosaurs, extant birds are an obvious candidate for FE-validation.
Here I present the first FE-model of a bird skull and its biomechanical behaviour during pecking and biting. Ostriches are chosen as a model system as they are large and retain a paleognathous palate and open cranial sutures in-keeping with their theropod ancestors. Loadings are applied to the beak based on (i) preliminary pecking forces recorded in-vivo, and (ii) biting forces calculated from musculoskeletal architecture. Results show that the behaviour of the skull is fundamentally different during pecking versus biting. The jugal bar is excessively stressed, particularly during biting, but is alleviated by introducing soft tissues and passive kinetic movement at sutures and joints. Results are useful on two counts in that they (1) suggest that a deviation from biting towards pecking behaviour in early avian evolution can be detected from characters of bony morphology, and (2) provide an idea where to attach strain gauges in the next step of the research – in-vitro strain measurement and comparison to FE-model derived strain.
Dipartimento di Biologia Strutturale e Funzionale, Università degli Studi dell’Insubria, via Dunant 3, I-21100 Varese, Italy (firstname.lastname@example.org )
Skin preservation in the reptiles from the Late Triassic Calcare di Zorzino Formation.
The Norian Calcare di Zorzino (Zorzino Limestone) yield an interesting vertebrate fauna, comprising mainly fishes
, but also reptiles were well represented. Although it was deposited amid a carbonate platform, terrestrial reptiles are more abundant and diverse than aquatic ones, with archosauriforms, protorosaurs, drepanosaurids and sphenodontids, in addition to pterosaurs. Several lines of evidence suggest that these reptiles lived on small islands that surrounded the basins in which the Calcare di Zorzino was deposited. Preservation is usually good and most specimens are fairly complete and articulated. In most cases however, no traces of soft parts are preserved, but there are some remarkable exceptions. In fact, skin patches are present on the holotypes of Drepanosaurus unguicaudatus
, of Vallesaurus cenensis
, and of Langobardisaurus pandolfii, as well as on one specimen of Megalancosaurus preonensis
. Preliminary investigation shows that the skin is not preserved as impression but scales are actually fossilized; that all specimens with fossilized skin belong to terrestrial taxa and the preserved portion in most cases corresponds to the tail or pelvic region (but soft tissues are present also in the shoulder region of Drepanosaurus
); and, finally, that specimens with fossilized skin were found only in the more marly and thinly laminated beds, while the skin is not preserved in those specimens found in thicker and more calcareous beds.
Karen K. Roberts
School of BEES, University of New South Wales, Sydney, Australia (email@example.com)
Fitting the maxilla to the mandible.
The detailed morphology of the lower teeth of ringtail possums (Marsupialia: Pseudocheiridae), particularly m1, is highly significant in determining species. Several new fossil pseudocheirid species have been recognised on the basis of lower teeth from the Oligo-Miocene deposits of Riversleigh, Australia. However, there is an equally large number of upper dental specimens, including two skulls, that are more difficult to identify to species, let alone positively match with an occluding group of lower teeth. Upper teeth are known for some previously identified fossil pseudocheirids, but pairings have been aided by low species diversity in their localities and distinct size correlations - little has been discussed of their diagnostic features. Species-level resolution of the upper teeth holds potentially valuable information regarding phylogeny and the palaeobiology of pseudocheirids.
A morphometric prediction method has been developed to help identify the upper teeth for fossil species. Using paired measurements of upper and lower molars of extant pseudocheirid species, regression analyses were performed and prediction equations calculated. As expected, a high correlation was found between matched occluding molars, and %SEE and %PE were also calculated to test prediction reliability. Initial application of the prediction equations to lower teeth of fossil species has satisfactorily narrowed the possible selection of almost 300 matching upper dental specimens, but only functions as a first step. Ultimately, matching of occluding teeth, and species identification of upper teeth must be based on morphology and more specific morphometric analyses.
Bristol University Department of Earth Sciences, Wills Memorial Building, BS8 1RJ
Natural History Museum, Department of Palaeontology, London SW7 5BD, UK (firstname.lastname@example.org)
Osteostracan evolution through space and time: a phylogenetic approach.
The Osteostraci (Cephalaspids) have a wide range both spatially and temporally. They share a last common ancestor with the jawed vertebrates which represents one of the most crucial stages of vertebrate evolution – the transition from jawless to jawed vertebrates. Osteostracan phylogeny therefore impacts not only upon our understanding of the acquisition of many key vertebrate characters but also ideas of palaeobiogeographic evolution across Laurussia and Siberia.
An in-depth phylogeny for the group is lacking and little consensus has been reached so far. Previous studies have been limited by out-dated methodology, taxonomic scope, or accuracy of findings. Here, novel observations are used to construct a computer generated phylogeny including recent new finds. The phylogeny impacts upon palaeobiogeography, osteostracan evolution and development of paired appendages.
The ancestral osteostracan state has broad implications for not only the group but also general early vertebrate evolution and gnathostome origins. The new phylogeny lends support to the long disputed claim that the tremataspids are derived rather than ancestral and thus supports the placement of Osteostraci as sister to the jawed vertebrates. However, the phylogeny indicates that the evolution and development of pectoral fins is more complicated than previously envisaged, with losses and potential reversions occuring within the group.
Osteostraci taxa generally demonstrate strong endemism and as such have a strong palaeogeographical signal. This new phylogeny enables cladistic palaeobiogeographic reconstruction of dispersal and vicariance events occuring across the arctic. The Osteostraci are found to have originated and diversified in South Norway and Britain.
Tamaki Sato & Xiao-chun Wu
(National Science Museum, 3-23-1 Hyakunincho, Shinjuku-ku, Tokyo, Japan; (email@example.com); Canadian Museum of Nature, Po Box 3443 STN”D”, Ottawa, ON K1P 6P4, Canada; (firstname.lastname@example.org)
Review of plesiosaurians (Reptilia, Sauropterygia) from the Upper Cretaceous non-marine sediments in Alberta, Canada.
Plesiosaurian remains from non-marine sediments are not very common, but such occurrences have been reported from several different horizons in various countries. In Canada, two Upper Cretaceous non-marine
units, the Dinosaur Park Formation and Horseshoe Canyon Formation in Alberta, have yielded plesiosaurian fossils. A previous study of the plesiosaurian fauna of the Dinosaur Park Formation (Campanian) confirmed their non-marine occurrences, and the dominance of elasmosaurids relative to polycotylids was demonstrated. The taxonomic status of the specimens from the non-marine Horseshoe Canyon Formation (Campanian-Maastrichtian, Upper Cretaceous), Alberta, Canada was recently reassessed. The holotype of Leurospondylus ultimus and a previously undescribed partial skeleton from Red Deer River Valley represent indeterminate elasmosaurids, whereas the “plesiosaurian” vertebra from Edmonton is actually an ornithopod caudal. The two plesiosaurian specimens came from different horizons for which different environments are inferred. The larger individual may be closely related to Elasmosaurus . These studies support the hypothesized decline of polycotylid plesiosaurs in the North American during the Late Campanian. Well-preserved plesiosaurian specimens from non-marine sediments are usually of juveniles and small adults, and it is suggested that small adults and juveniles existed in both marine and non-marine environments whereas large adults were limited to the former.
GINA SEMPREBON1 & FLORENT RIVALS 2
1Bay Path College, Department of Biology, 588 Longmeadow Street, Longmeadow, MA 01106, USA (email@example.com); 2University of Hamburg, Biozentrum Grindel and Zoological Museum, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany (firstname.lastname@example.org)
Dental wear and dietary evolution of North American Miocene to Pleistocene ungulates.
Stereoscopic microwear and mesowear analyses have proven very useful as independent tools for paleodietary reconstruction to test paleodietary inferences drawn from the study of craniodental morphology in extinct species. These techniques lend themselves particularly well to dietary studies involving large samples and spanning vast tracks of evolutionary time. Here, we compare dental microwear (i.e., immediate wear) and mesowear (i.e., cumulative wear) results for both Tertiary and Quaternary representatives of the families Antilocapridae, Camelidae, Dromomerycidae, Equidae, and Oreodontidae. Results offer insights into the origin of hypsodonty in certain lineages and also show that the classic story in paleontology regarding the timing of changes in mammalian communities in North America due to the spread of savanna grasslands replacing more closed habitats is greatly oversimplified. For example, peak shifts toward more abrasive diets apparently occurred in the earliest Miocene in Equids but not until the late Miocene in Antilocaprids and Dromomerycids. Results also indicate that the widely ascribed ideas of brachyodonty being indicative of browsing, mesodonty being indicative of mixed feeding, and hypsodonty being indicative of grazing are in need of serious revision and more applicable to extant versus extinct ungulates.
STEVEN C. SWEETMAN
School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth, PO1 3QL, UK. (email@example.com)
Wealden (Early Cretaceous) mammals from southern Britain, including a new spalacotheriid from the Barremian Wessex Formation of the Isle of Wight and its bearing on spalacotheriid evolution.
The first undisputed record of mammals from Wealden Group (Early Cretaceous) strata of Britain dates from 1911. Subsequently, no Wealden mammal fossils were found until a sustained search was commenced in 1960. This resulted in the recovery of a number of new specimens from the Valanginian of mainland Britain. During the 1970s, in a further attempt to isolate Wealden mammal remains, a number of workers also undertook bulk screening of Barremian strata exposed on the Isle of Wight. Only two multituberculate teeth were found and work to recover mammal fossils from the Wealden of the Isle of Wight ceased. Despite this unpromising start, recent comprehensive bulk screening of Isle of Wight Wessex Formation strata has resulted in the recovery of a diverse microvertebrate fauna including at least six mammals. Among these are a new spalacolestine spalacotheriid representing the first European record of the Spalacolestinae. Hitherto, five species (one unnamed) of spalacotheriid mammal were known from the Lower Cretaceous of Britain. All are referred to the genus Spalacotherium
but it is now evident that these referrals should be treated with caution. Furthermore, the new Wessex Formation spalacotheriid and recently described spalacotheriids from the ?Barremian of Japan
, and the Barremian and Aptian of China exhibit combinations of characters that suggest that these tiny mammals were more diverse and that their evolution was more complex than previously recognized. The discovery of a spalacolestine in the Barremian Wessex Formation supports the concept of faunal interchange between Europe, Asia and North America during the Early Cretaceous and possible derivation of North American spalacotheriids from a European or Eurasian ancestor.
Haiyan Tong1,2, Eugene Gaffney2 and Ren Hirayama3
1. 16 cour du Liégat, 75013 Paris, France (firstname.lastname@example.org); 2. American Museum of Natural History, Central Park west at 79th st, New York, NY 10024, USA (email@example.com); 3. School of International Liberal Studies, Waseda University, Nishiwaseda 1-7-14, Shinjuku-ku, Tokyo 169-0051, Japan (firstname.lastname@example.org)
The diversity of the turtle assemblage from the Ouled Abdoun Basin, Morocco.
The largest phosphate basin of Morocco, the Ouled Abdoun Basin, has yielded a very rich vertebrate fauna, ranging in age from the latest Cretaceous (Maastrichtian) to the Early Eocene (Ypresian). Turtle remains are abundant there; they include both articulated skeletons and isolated elements. This turtle assemblage shows considerable diversity. More than a dozen taxa, mostly based on skulls, have been collected, belonging to both cryptodires and pleurodires. The cryptodiran turtles are represented by cheloniid sea turtles (Osteopygis emarginatus
from the Danian beds, Tasbacka ouledabdounensis
from the Thanetian beds), and a dermochelyid from the Maastrichtian beds. The pleurodires consist of several taxa of bothremydids, including Phosphatochelys tedfordi
from the Ypresian beds. All turtles hitherto recorded from this near-shore marine phosphate sequence are marine forms. The remarkable diversity in skull morphology, especially among bothremydids, varying from a very long
, narrow snout to a wide, telescoped short face, and from a narrow triturating surface to a very large secondary palate with deep pits, reveals sensory modifications and adaptations in feeding mechanisms.
KENNY J. TRAVOUILLON1,2 & MICHAEL BEDWARD3
1School of Biological, Earth and Environmental Sciences, University of New South Wales, New South Wales 2052, Australia. ( email@example.com)u.
2UMR CNRS 5125 Paleoenvironments et Paleobiosphere”, Université Claude Bernard-Lyon 1, Bat. Geode, Domaine scientifique de la Doua, F-69622 Villeurbanne Cedex, France. (Kenny.Travouillon@pepsmail.univ-lyon1.f)r.
3NSW National Parks and Wildlife Service, Population Analysis and Modeling Unit, Biodiversity Conservation Science Section, Department of Environment and Conservation (NSW)PO Box 1967, Hurstville NSW 2220, Australia. (Michael.Bedward@environment.nsw.gov.au).
Finding the Minimum Sample Richness (MSR) for multivariate analyses: implications for palaeoecology.
Many techniques have been developed to estimate species richness and beta diversity. Those techniques, dependent on sampling, require abundance or presence/absence data. Palaeontological data is by nature incomplete (Hammer & Harper 2006), and presence/absence data is often the only type of data that can be used to provide an estimate of ancient biodiversity. We propose a new technique (using multivariate analyses) to assess whether palaeontological presence/absence data are statistically representative of original life assemblages. Artificially generated species lists are used to make parent and subset lists which are then compared using a cluster analysis to find the minimum sample richness (MSR) with a 95% confidence of correctly clustering the parent and subset lists. Several commonly used similarity indexes (Dice, Jaccard, Simpson and Raup-Crick) were investigated. Of these, the Raup-Crick index required the lowest MSR, i.e. it performed best at correctly clustering subset lists with their respective parents at low sample species richness. MSR can be found by our graphs for presence/absence data provided absolute species richness and the beta diversity can be estimated.
Hammer, O. and Harper, D., 2006. Paleontological Data Analysis. Blackwell Publishing: UK.
DAVID M. UNWIN
Museum für Naturkunde, Humboldt Universität zu Berlin, Germany/ Department for Museum Studies, Leicester University, LE17LG, UK (firstname.lastname@example.org)
The origin of pterodactyloid pterosaurs.
If pterodactyloids had never existed pterosaur evolutionary history would have been a truly modest affair that faded out in the Early Cretaceous. As it is, following their debut in the Late Jurassic, pterodactyloids became remarkably diverse, achieved giant size, and seem to have been the dominant group of flying vertebrates throughout the Cretaceous. To understand this evolutionary success story we need to gain insights into the origin of pterodactyloids, and to do this we must first establish how pterodactyloids are related to more basal forms ('rhamphorhynchoids'). Traditional schemes are vague and reveal nothing of consequence regarding this relationship. Phylogenetic analyses, by contrast, largely concur in grouping pterodactyloids with Rhamphorhynchus
(or Rhamphorhynchidae), with all other 'rhamphorhynchoids' lying basal to this clade. The problem with this arrangement is that it requires several character state reversals (rhamphorhynchids and more basal clades such as campylognathoidids share various apomorphies not found in pterodactyloids) and reveals very little regarding the origins of typical features of pterodactyloids. An alternative arrangement, supported here, unites pterodactyloids with anurognathids, an unusual group of 'frog-headed' insectivorous pterosaurs that lie at or near the base of the pterosaur tree. If correct
, this hypothesis means that classic pterodactyloid apomorphies (e.g. loss of cervical ribs and short tail) occurred early in pterosaur evolution and are not restricted to pterodactyloids. Moreover, the lineage leading to anurognathids + pterodactyloids must have appeared before the Jurassic and most or (if anurognathids are the most basal clade) possibly all long-tailed pterosaurs belong within a distinct clade.
Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK (email@example.com).
The Palaeobiogeography of the Morrison and Tendaguru Dinosaur Faunas.
The Late Jurassic faunas of the Morrison Formation (USA) and Tendaguru (Tanzania) apparently share several dinosaurian genera (e.g. Elaphrosaurus
). This faunal similarity has been interpreted as evidence for a terrestrial connection between North America and Africa during the Late Jurassic, which allowed regular dispersal/ migration between the two areas. Faunal dissimilarities have been explained as either sampling error or palaeoecological differences. These interpretations can be challenged on a number of grounds. First, although palaeogeographic reconstructions are not unanimous, the majority depict marine barriers between North America and Africa from ca. the Oxfordian onwards. Second, taxonomic revision has undermined the evidence for generic-level similarities between the two faunas (e.g. “Barosaurus
from Tendaguru has recently been re-interpreted as Tornieria africana
, and there are doubts about the congeneric status of the Morrison and Tendaguru Brachiosaurus
species). Finally, cladistic biogeography sheds light on the biotic relationships between North America and Africa. Area cladograms for the Late Jurassic have placed North America and Africa as sister areas
, but this is compatible with either a land connection (allowing dispersal) or separation (promoting vicariance). Furthermore, analysis using an updated data-set supports a closer relationship between Europe and North America compared to Africa in the Late Jurassic. Thus, there is little biogeographic or palaeogeographic evidence for faunal exchange between North America and Africa in the Late Jurassic. Instead, a more plausible explanation for the observed distribution patterns requires the formation of a widespread biota during the Middle Jurassic, followed by separation and vicariance in the Late Jurassic.
Department of Geology, Royal Holloway, University of London & Department of Palaeontology, The Natural History Museum, London, UK (firstname.lastname@example.org)
Mechanisms of accumulation of mammalian remains in the Late Eocene, Isle of Wight (UK).
A quantitative and qualitative study has been undertaken of surface modifications on enamel, dentine and bone of micromammals from a single bed in the Osborne Member, Headon Hill Formation. The theridomyids, glirids, marsupials and nyctitheres were living in close association with a small floodplain pond in which the fossiliferous sediments accumulated. The primates
, bats and apatothere were living further away from this pond, probably in forested patches on the floodplain. The pantolestid shows evidence of longer distance waterborne transport. The majority of theridomyids, many marsupials, fewer glirids and even fewer nyctitheres were locally predated/scavenged. The amphicyonid Cynodictis
is identified as the predator/scavenger of the theridomyids and marsupials, based on bite marks and fragmentation patterns, whereas the possibility of the same predator/scavenger for the glirids and the nyctitheres is not excluded. Lesser predation/scavenging of the nyctitheres and glirids may be due to their scansorial locomotion. The primates were eaten by an animal that caused little fragmentation or corrosion of their skeletal elements: probably a carnivorous bird. The bats, apatothere and pantolestid also show indications of predation/scavenging, but the identity of the predator/scavenger is not clear. A crocodile or other reptile predator is excluded as all cause complete demineralization of their prey. Large creodonts are possible predators/scavengers for some mammals, especially the larger pantolestid, but there is no evidence of this interaction. This detailed taphonomic analysis of individual species in a single bed has resulted in a comprehensive understanding of the accumulation of the micromammalian assemblage.
UMR 5143 du CNRS, Département Histoire de la Terre, Muséum National d’Histoire Naturelle, 8 rue Buffon, 75005 Paris (