scholarly journals A new elasmosaurid plesiosaurian from the Early Cretaceous of Russia marks an early attempt at neck elongation

2020 ◽  
Author(s):  
Valentin Fischer ◽  
Nikolay G Zverkov ◽  
Maxim S Arkhangelsky ◽  
Ilya M Stenshin ◽  
Ivan V Blagovetshensky ◽  
...  
Keyword(s):  
Lower Cretaceous ◽  
Fossil Record ◽  
Phylogenetic Signal ◽  
Differential Growth ◽  
Early Attempt ◽  
Marine Reptiles ◽  
Upper Hauterivian ◽  
Wide Range ◽  
Body Shapes ◽  
Multiple Episodes

Abstract Plesiosaurian marine reptiles evolved a wide range of body shapes during the Jurassic and Cretaceous, including long-necked forms. Many Late Cretaceous members of the clade Elasmosauridae epitomized this part of the plesiosaurian morphological spectrum by evolving extremely long necks through somitogenesis (resulting in an increase in the number of cervical centra) and differential growth (resulting in the elongation of cervical centra). However, the early evolution of elasmosaurids remains poorly understood because of a generally poor Lower Cretaceous fossil record. We describe a new elasmosaurid, Jucha squalea gen. et sp. nov., from the upper Hauterivian (Lower Cretaceous) of Ulyanovsk (European Russia), in addition to other elasmosaurid remains from the same area. Jucha squalea is one of the oldest and basalmost elasmosaurids known and lacks a series of features that otherwise characterize the group, such as the heart-shaped intercoracoid fenestra and the median pectoral bar. However, Jucha squalea marks an early attempt at cervical elongation through differential growth. The data we gathered on the shape of cervical centra among elasmosaurids suggest multiple episodes of elongation and shortening. However, the precise patterns are obscured by an unstable phylogenetic signal.

scholarly journals Hydromechanics of low-Reynolds-number flow. Part 2. Singularity method for Stokes flows

1975 ◽  
Vol 67 (4) ◽  
pp. 787-815 ◽  
Author(s):  
Allen T. Chwang ◽  
T. Yao-Tsu Wu
Keyword(s):  
Exact Solutions ◽  
Stokes Flow ◽  
Fundamental Solutions ◽  
The Body ◽  
Circular Cylinders ◽  
Geometrical Parameters ◽  
Flow Problems ◽  
Singularity Method ◽  
Wide Range ◽  
Body Shapes

The present study further explores the fundamental singular solutions for Stokes flow that can be useful for constructing solutions over a wide range of free-stream profiles and body shapes. The primary singularity is the Stokeslet, which is associated with a singular point force embedded in a Stokes flow. From its derivatives other fundamental singularities can be obtained, including rotlets, stresslets, potential doublets and higher-order poles derived from them. For treating interior Stokes-flow problems new fundamental solutions are introduced; they include the Stokeson and its derivatives, called the roton and stresson.These fundamental singularities are employed here to construct exact solutions to a number of exterior and interior Stokes-flow problems for several specific body shapes translating and rotating in a viscous fluid which may itself be providing a primary flow. The different primary flows considered here include the uniform stream, shear flows, parabolic profiles and extensional flows (hyper-bolic profiles), while the body shapes cover prolate spheroids, spheres and circular cylinders. The salient features of these exact solutions (all obtained in closed form) regarding the types of singularities required for the construction of a solution in each specific case, their distribution densities and the range of validity of the solution, which may depend on the characteristic Reynolds numbers and governing geometrical parameters, are discussed.

scholarly journals Two new long-rostrum cranefly species from the Cretaceous Iberian amber (Diptera, Limoniidae, Helius)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Iwona Kania-Kłosok ◽  
Wiesław Krzemiński ◽  
Antonio Arillo
Keyword(s):  
Environmental Conditions ◽  
Lower Cretaceous ◽  
Fossil Record ◽  
First Record ◽  
Northern Spain ◽  
Fossil Species ◽  
Body Morphology ◽  
Cretaceous Period ◽  
Basque Cantabrian Basin

AbstractFirst record of the genus Helius—long-rostrum cranefly from Maestrazgo Basin (eastern Spain, Iberian Penisula) is documented. Two new fossil species of the genus Helius are described from Cretaceous Spanish amber and compared with other species of the genus known from fossil record with particular references to these known from Cretaceous period. Helius turolensis sp. nov. is described from San Just amber (Lower Cretaceous, upper Albian) Maestrazgo Basin, eastern Spain, and Helius hispanicus sp. nov. is described from Álava amber (Lower Cretaceous, upper Albian), Basque-Cantabrian Basin, northern Spain. The specific body morphology of representatives of the genus Helius preserved in Spanish amber was discussed in relation to the environmental conditions of the Maestrazgo Basin and Basque-Cantabrian Basin in Cretaceous.

scholarly journals Convergent evolution of ramified antennae in insect lineages from the Early Cretaceous of Northeastern China

2016 ◽  
Vol 283 (1839) ◽  
pp. 20161448 ◽  
Author(s):  
Taiping Gao ◽  
Chungkun Shih ◽  
Conrad C. Labandeira ◽  
Jorge A. Santiago-Blay ◽  
Yunzhi Yao ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Motion Detection ◽  
Lower Cretaceous ◽  
Fossil Record ◽  
Convergent Evolution ◽  
Chemical Cues ◽  
Northeastern China ◽  
Environmental Cues ◽  
Key Innovation ◽  
Temperature Levels

Antennae are important, insect sensory organs that are used principally for communication with other insects and the detection of environmental cues. Some insects independently evolved ramified (branched) antennae, which house several types of sensilla for motion detection, sensing olfactory and chemical cues, and determining humidity and temperature levels. Though ramified antennae are common in living insects, occasionally they are present in the Mesozoic fossil record. Here, we present the first caddisflies with ramified antennae, the earliest known fossil sawfly, and a scorpionfly also with ramified antennae from the mid-Lower Cretaceous Yixian Formation of Northeastern China, dated at 125 million years ago (Ma). These three insect taxa with ramified antennae consist of three unrelated lineages and provide evidence for broad structural convergence that historically has been best demonstrated by features such as convergent mouthparts. In addition, ramified antennae in these Mid-Mesozoic lineages likely do not constitute a key innovation, as they are not associated with significantly increased diversification compared with closely related lineages lacking this trait, and nor are they ecologically isolated from numerous, co-occurring insect species with unmodified antennae.

A fossil record of land plant origins from charophyte algae

Science ◽  
2021 ◽  
Vol 373 (6556) ◽  
pp. 792-796 ◽  
Author(s):  
Paul K. Strother ◽  
Clinton Foster
Keyword(s):  
Fossil Record ◽  
Evolutionary History ◽  
Phylogenetic Signal ◽  
Land Plant ◽  
Fossil Plants ◽  
Fossil Plant ◽  
Molecular Phylogenetic ◽  
History Of ◽  
Time Gap ◽  
Evolutionary Continuity

Molecular time trees indicating that embryophytes originated around 500 million years ago (Ma) during the Cambrian are at odds with the record of fossil plants, which first appear in the mid-Silurian almost 80 million years later. This time gap has been attributed to a missing fossil plant record, but that attribution belies the case for fossil spores. Here, we describe a Tremadocian (Early Ordovician, about 480 Ma) assemblage with elements of both Cambrian and younger embryophyte spores that provides a new level of evolutionary continuity between embryophytes and their algal ancestors. This finding suggests that the molecular phylogenetic signal retains a latent evolutionary history of the acquisition of the embryophytic developmental genome, a history that perhaps began during Ediacaran-Cambrian time but was not completed until the mid-Silurian (about 430 Ma).

scholarly journals Comparative Cladistics: Fossils, Morphological Data Partitions and Lost Branches in the Fossil Tree of Life

2017 ◽  
Author(s):  
Ross Mounce
Keyword(s):  
Large Scale ◽  
Phylogenetic Signal ◽  
Scientific Progress ◽  
Molecular Data ◽  
Morphological Data ◽  
Data Sets ◽  
Phylogenetic Groups ◽  
Use Of Data ◽  
Wide Range ◽  
Cladistic Analyses

In this thesis I attempt to gather together a wide range of cladistic analyses of fossil and extant taxa representing a diverse array of phylogenetic groups. I use this data to quantitatively compare the effect of fossil taxa relative to extant taxa in terms of support for relationships, number of most parsimonious trees (MPTs) and leaf stability. In line with previous studies I find that the effects of fossil taxa are seldom different to extant taxa – although I highlight some interesting exceptions. I also use this data to compare the phylogenetic signal within vertebrate morphological data sets, by choosing to compare cranial data to postcranial data. Comparisons between molecular data and morphological data have been previously well explored, as have signals between different molecular loci. But comparative signal within morphological data sets is much less commonly characterized and certainly not across a wide array of clades. With this analysis I show that there are many studies in which the evidence provided by cranial data appears to be be significantly incongruent with the postcranial data – more than one would expect to see just by the effect of chance and noise alone. I devise and implement a modification to a rarely used measure of homoplasy that will hopefully encourage its wider usage. Previously it had some undesirable bias associated with the distribution of missing data in a dataset, but my modification controls for this. I also take an in-depth and extensive review of the ILD test, noting it is often misused or reported poorly, even in recent studies. Finally, in attempting to collect data and metadata on a large scale, I uncovered inefficiencies in the research publication system that obstruct re-use of data and scientific progress. I highlight the importance of replication and reproducibility – even simple reanalysis of high profile papers can turn up some very different results. Data is highly valuable and thus it must be retained and made available for further re-use to maximize the overall return on research investment.

The tale of the headless turtle

Zootaxa ◽  
2016 ◽  
Vol 4200 (2) ◽  
pp. 327 ◽  
Author(s):  
PEDRO S. R. ROMANO
Keyword(s):  
New Species ◽  
Phenotypic Plasticity ◽  
Lower Cretaceous ◽  
Fossil Record ◽  
Diagnostic Features ◽  
Fossil Species ◽  
The Past ◽  
Early Paleocene ◽  
Phylogenetic Hypotheses ◽  
A New Species

Pelomedusoides is the most diverse clade of side-necked turtles and there is an extensive fossil record (de Broin, 1988; Lapparent de Broin, 2000; Gaffney et al., 2006, 2011) that dates back at least to the Barremian (Lower Cretaceous) (Romano et al., 2014). Its large fossil record evidences a greater diversity in the past, particularly at the end of the Mesozoic, and exhibits a good sampling of species that are represented by skull material (Gaffney et al., 2006, 2011). As a consequence, the most complete and recent phylogenetic hypotheses for this clade (e.g. Romano et al., 2014; Cadena, 2015) are based on matrices comprising a great amount of cranial characters derived largely from Gaffney et al. (2006, 2011). In addition, it is well established that shell characters show a lot of phenotypic plasticity, even in the fossil species (Romano, 2008; Gaffney et al., 2006, 2011). In most cases it consequently is not justified to rely on “diagnostic features” of poorly informative shell-only material for describing a new species. Because of that, most authors remark new morphotypes in the literature when such aberrant specimens are recovered, but do not make any nomenclatural act by proposing a new yet poorly supported species (e.g. Romano et al., 2013; Ferreira & Langer, 2013; Menegazzo et al., 2015). Unfortunately, such a supposedly new bothremydid turtle (Pleurodira: Bothremydidae) from the Early Paleocene of Brazil was recently described based on poorly diagnostic remains (Carvalho et al., 2016; hereafter CGB, for the authors initials) and a correction of this unfounded nomenclatural act is required. In addition I present some comments on shell only material from Brazil in order to guide splitter-taxonomists to stop describing poorly preserved fossil specimens as new species. 

AN OVERVIEW OF HYMENOPTERAN COCOONS AS A TOOL TO INTERPRET ICHNOSPECIES OF FICTOVICHNUS (PALLICHNIDAE) AND OTHER FOSSIL COCOONS OF WASPS

Palaios ◽  
2019 ◽  
Vol 34 (11) ◽  
pp. 562-574
Author(s):  
LAURA C. SARZETTI ◽  
JORGE F. GENISE ◽  
PABLO DINGHI ◽  
M. ALEJANDRA MOLINA
Keyword(s):  
Phylogenetic Signal ◽  
Character State ◽  
Complex Structures ◽  
Single Family ◽  
Accurate Identification ◽  
Texture Surface ◽  
Equatorial Diameter ◽  
Wide Range ◽  
Preservation Potential ◽  
Surface Morphologies

ABSTRACT Hymenopteran cocoons are complex structures constructed from silk by larvae and exhibit a wide range of morphologies, compositions, and textures. The recognition of the most relevant characters of modern cocoons is important for the accurate identification of trace fossils attributed to wasps, which are included in the ichnogenus Fictovichnus. Characters assessed in this study are length, equatorial diameter, diameters near the extremes, shape, color, texture, surface morphology, and occurrence (isolated or clustered). We mapped these characters onto a hymenopteran phylogeny, revealing that the distribution of most of them has no evident phylogenetic signal. In many cases, there is more than one character state in a single family, whereas others appear distributed among several groups. Ellipsoidal and ovoid cocoons, showing membranous texture are the most basal and common characters. Bilobated, subconical and fusiform shapes, clustering, nipple and pores seem to be autapomorphies for certain groups. Crabronidae, Pompilidae, Scolioidea and Thynnoidea construct hard coriaceous cocoons, which may show distinctive surface morphologies and would have the highest preservation potential in paleosols. Data presented herein show that both Fictovichnus sciuttoi and Fictovichnus aragon were correctly attributed to Crabronidae or Pompilidae, although Scolioidea and Thynnoidea cannot be ruled out because of the shape and coriaceous texture of their cocoons. According to the low phylogenetic signal of Hymenoptera cocoons found herein, it would be impossible to refine the affinities of these ichnospecies to particular taxa. The simple morphology of Fictovichnus gobiensis precludes a definitive attribution, either to wasps or to coleopterans, even after the new data presented herein.

The Triassic U–Pb age for the aquatic long-necked protorosaur of Guizhou, China

2014 ◽  
Vol 151 (4) ◽  
pp. 749-754 ◽  
Author(s):  
YANBIN WANG ◽  
DETING YANG ◽  
JUAN HAN ◽  
LITING WANG ◽  
JIANXIN YAO ◽  
...  
Keyword(s):  
Middle Triassic ◽  
Rapid Evolution ◽  
Guizhou Province ◽  
Ion Microprobe ◽  
Isotopic Age ◽  
Zircon Age ◽  
Marine Reptiles ◽  
Wide Range ◽  
History Of ◽  
Permian Mass Extinction

AbstractThe ancient marine limestone beds of the upper part of the Guanling Formation, Panxian County, Guizhou Province, SW China, yielded a wide range of high-diversity well-preserved marine reptiles such as the fully aquatic protorosaur with an extremely long neckDinocephalosaurus orientalis, the oldest mixosaurid ichthyosaurs and lariosaurs. However, there is no precise isotopic age to study the intriguing origin, evolution and emigration history of the important fauna. We report a sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon age for a volcanic tuff bed within the upper part of the Guanling Formation. The result indicates that the age of the fossil horizon is 244.0±1.3 Ma, 14 Ma earlier than the previously estimated age based on conodont evidence. We consider that the marine reptiles had a relatively rapid evolution during Middle Triassic time, some 8 Ma after the end-Permian mass extinction.

First plesiosaur remains from the lower Cretaceous of the Neuquén Basin, Argentina

2003 ◽  
Vol 77 (4) ◽  
pp. 784-789 ◽  
Author(s):  
Dario G. Lazo ◽  
Marcela Cichowolski
Keyword(s):  
Lower Cretaceous ◽  
Sister Group ◽  
Monophyletic Group ◽  
Phylogenetic Position ◽  
Crown Group ◽  
Marine Reptiles ◽  
Stem Group ◽  
Neuquen Basin ◽  
Neuquén Basin

Plesiosaurs constitute a monophyletic group whose stratigraphical range is uppermost Triassic to uppermost Cretaceous (Brown, 1981). They were large predatory marine reptiles, highly adapted for submarine locomotion, with powerful paddle-like limbs and heavily reinforced limb girdles (Saint-Seine, 1955; Romer, 1966; Carroll, 1988; Benton, 1990). The Plesiosauria clade belongs to the Sauropterygia, which has recently been hypothesized as the sister-group of the Ichthyosauria. Together with that clade they form the Euryapsida (Caldwell, 1997). The Sauropterygia can be subdivided into relatively plesiomorphic stem-group taxa from the Triassic (Placodonts, Nothosauroids, and Pistosauroids), and the obligatorily marine crown-group Plesiosauria (Rieppel, 1999). Plesiosaurs are traditionally divided into two superfamilies: Plesiosauroidea, with usually small heads and long necks; and Pliosauroidea, with larger heads and shorter necks (Welles, 1943; Persson, 1963; Brown, 1981). Plesiosauroidea contains three families: Plesiosauridae, Cryptoclididae, and Elasmosauridae (Brown, 1981; Brown and Cruickshank, 1994). The validity of the Polycotylidae Cope, 1869, has long been questioned and its phylogenetic position among Plesiosauria debated, as many consider it to be related to the Pliosauridae or to be a sister-group of the Elasmosauridae (Sato and Storrs, 2000; O'Keefe, 2001).

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