Cameron S.L.,Queensland University of Technology |
Lo N.,University of Sydney |
Bourguignon T.,Hokkaido University |
Svenson G.J.,University Circle |
Evans T.A.,National University of Singapore
Molecular Phylogenetics and Evolution | Year: 2012
Despite their ecological significance as decomposers and their evolutionary significance as the most speciose eusocial insect group outside the Hymenoptera, termite (Blattodea: Termitoidae or Isoptera) evolutionary relationships have yet to be well resolved. Previous morphological and molecular analyses strongly conflict at the family level and are marked by poor support for backbone nodes. A mitochondrial (mt) genome phylogeny of termites was produced to test relationships between the recognised termite families, improve nodal support and test the phylogenetic utility of rare genomic changes found in the termite mt genome. Complete mt genomes were sequenced for 7 of the 9 extant termite families with additional representatives of each of the two most speciose families Rhinotermitidae (3 of 7 subfamilies) and Termitidae (3 of 8 subfamilies). The mt genome of the well supported sister-group of termites, the subsocial cockroach Cryptocercus, was also sequenced. A highly supported tree of termite relationships was produced by all analytical methods and data treatment approaches, however the relationship of the termites + Cryptocercus clade to other cockroach lineages was highly affected by the strong nucleotide compositional bias found in termites relative to other dictyopterans. The phylogeny supports previously proposed suprafamilial termite lineages, the Euisoptera and Neoisoptera, a later derived Kalotermitidae as sister group of the Neoisoptera and a monophyletic clade of dampwood (Stolotermitidae, Archotermopsidae) and harvester termites (Hodotermitidae). In contrast to previous termite phylogenetic studies, nodal supports were very high for family-level relationships within termites. Two rare genomic changes in the mt genome control region were found to be molecular synapomorphies for major clades. An elongated stem-loop structure defined the clade Polyphagidae + (Cryptocercus+. termites), and a further series of compensatory base changes in this stem-loop is synapomorphic for the Neoisoptera. The complicated repeat structures first identified in Reticulitermes, composed of short (A-type) and long (B-type repeats) defines the clade Heterotermitinae + Termitidae, while the secondary loss of A-type repeats is synapomorphic for the non-macrotermitine Termitidae. © 2012 Elsevier Inc.
Pocknall D.T.,Hess Corporation |
Jarzen D.M.,University Circle
Palynology | Year: 2012
Grimsdalea magnaclavata was first described by Germeraad, Hopping and Muller from Miocene and Pliocene deposits of northern South America, specifically Colombia and Venezuela. The specific epithet, magnaclavata', was selected by the authors to draw attention to the distinctive clavate processes of the pollen. A revised taxonomic description is supported by illustrations of fossil specimens from outcrop and well sections that show the range in morphology not previously recorded in the original description; the key difference is the wide variation in process morphology from clavae to clavae with interspersed echinae. Based on the new observations of the pollen morphology we conclude that the records from Cretaceous and Paleogene sediments in North and West Africa are invalid. G. magnaclavata is clearly restricted to northern South America from the Miocene to Pleistocene. The parent plant of G. magnaclavata probably grew in upper coastal plain or around swamps, commonly associated with shrubs and herbaceous savannah plants. The botanical affinity of G. magnaclavata has always been in question. Based on a review of pollen from several palm genera presently extant in northern South America we consider that the nearest living relatives, if indeed G. magnaclavata is an ancient palm, are the genera Mauritia and Mauritiella. The basis for this conclusion is the distinctive foot layer morphology of the processes in the fossil and the modern examples. © 2012 Copyright Taylor and Francis Group, LLC.
Mallon J.C.,University of Calgary |
Holmes R.,University of Alberta |
Eberth D.A.,Royal Tyrrell Museum of Palaeontology |
Ryan M.J.,University Circle |
Anderson J.S.,University of Calgary
Journal of Vertebrate Paleontology | Year: 2011
Anchiceratops is a chasmosaurine ceratopsid from the Upper Cretaceous Horseshoe Canyon Formation (HCF) of Alberta. It is distinguished primarily by its unique parietosquamosal frill ornamentation and possibly by the presence of a ventrally flexed olfactory bulb of the brain. Although Anchiceratops is known from at least ten partial skulls, only two of these have been formally described. These skulls are not stratigraphically segregated, but they differ markedly in their proportions (e.g., supraorbital horncore and frill dimensions), causing previous authors to account for this disparity with reference to either interspecific or sexual differences. Both of these hypotheses assume that variation in Anchiceratops is dimorphic; however, this assumption has never been tested with reference to all available material. The present study describes all material from the HCF that can be positively attributed to Anchiceratops, and tests the assumption of dimorphism by subjecting this material to a series of morphometric analyses. We find no compelling evidence for dimorphism in Anchiceratops, although sample size is still too small for convincing statistical support. We conclude that there is a single, variable species of Anchiceratops, A. ornatus. Average sedimentation rates for the HCF suggest that A. ornatus is a particularly long-lived species compared with other ceratopsids (1.5-2.0 Ma), and the paleoecological implications of this are discussed. A cladistic analysis that includes the new data presented here indicates that Anchiceratops is more closely related to Chasmosaurus than to Triceratops, in contrast with previous studies. © 2011 by the Society of Vertebrate Paleontology.
Mallon J.C.,Canadian Museum of Nature |
Ryan M.J.,University Circle |
Campbell J.A.,University of Calgary
Zoological Journal of the Linnean Society | Year: 2015
Disentangling ontogenetic from interspecific variation is key to understanding biodiversity in the fossil record, yet information on growth in the ceratopsid subfamily Chasmosaurinae is sparse. Here, we describe the partial skull of a juvenile chasmosaurine, attributed to Arrhinoceratops brachyops, within the context of more mature specimens of this species, to better understand the ontogenetic transformations therein. We show that as A. brachyops matured, the postorbital horncores became longer and shifted from a posterior to an anterior inclination, the delta-shaped frill epiossifications became lower and fused to the underlying frill, and the face became more elongate. In these respects, A. brachyops closely resembled Triceratops, suggesting that these ontogenetic changes may have been common to all long-horned chasmosaurines. However, an event-paired cladistic analysis of Chasmosaurinae using a standardized matrix of 24 developmental characters reveals that the relative timing of ontogenetic events in Arrhinoceratops was more like that of Chasmosaurus, particularly in the relatively late reduction in scalloping around the frill margins. Thus, the ontogenetic similarities between Arrhinoceratops and Triceratops appear to be plesiomorphic, partly related to the retention of the elongate postorbital horncores, which are primitive for Ceratopsidae. This study elucidates the otherwise contentious evolutionary relationships of Arrhinoceratops, and highlights the importance of ontogenetic data for resolving phylogenies when morphological data from adults alone are inadequate. © 2015 The Linnean Society of London.
Evans D.C.,Royal Ontario Museum |
Evans D.C.,University of Toronto |
Schott R.K.,University of Toronto |
Larson D.W.,University of Toronto |
And 3 more authors.
Nature Communications | Year: 2013
Taphonomic biases dictate how organisms are represented in the fossil record, but their effect on studies of vertebrate diversity dynamics is poorly studied. In contrast to the high diversity and abundance of small-bodied animals in extant ecosystems, small-bodied dinosaurs are less common than their large-bodied counterparts, but it is unclear whether this reflects unique properties of dinosaurian ecosystems or relates to taphonomic biases. A new, fully domed pachycephalosaurid dinosaur, Acrotholus audeti, from the Santonian of Alberta predates incompletely domed taxa, and provides important new information on pachycephalosaur evolution and the completeness of the ornithischian fossil record. Here we provide the first empirical evidence that the diversity of small-bodied ornithischian dinosaurs is strongly underestimated based on ghost lineages and the high proportion of robust and diagnostic frontoparietal domes compared with other pachycephalosaur fossils. This suggests preservational biases have a confounding role in attempts to decipher vertebrate palaeoecology and diversity dynamics through the Mesozoic. © 2013 Macmillan Publishers Limited. All rights reserved.