1,721,005 research outputs found
The first fossil leaf insect: 47 million years of specialized cryptic morphology and behavior
No full textStick and leaf insects (insect order Phasmatodea) are represented primarily by twig-imitating slender forms. Only a small percentage (approximate to 1%) of extant phasmids belong to the leaf insects (Phylliinae), which exhibit an extreme form of morphological and behavioral leaf mimicry. Fossils of phasmid insects are extremely rare worldwide. Here we report the first fossil leaf insect, Eophyllium messelensis gen. et sp. nov., from 47-million-year-old deposits at Messel in Germany. The new specimen, a male, is exquisitely preserved and displays the same foliaceous appearance as extant male leaf insects. Clearly, an advanced form of extant angiosperm leaf mimicry had already evolved early in the Eocene. We infer that this trait was combined with a special behavior, catalepsy or "adaptive stillness," enabling Eophyllium to deceive visually oriented predators. Potential predators reported from the Eocene are birds, early primates, and bats. The combination of primitive and derived characters revealed by Eophyllium allows the determination of its exact phylogenetic position and illuminates the evolution of leaf mimicry for this insect group. It provides direct evidence that Phylliinae originated at least 47 Mya. Eophyllium enlarges the known geographical range of Phylliinae, currently restricted to southeast Asia, which is apparently a relict distribution. This fossil leaf insect bears considerable resemblance to extant individuals in size and cryptic morphology, indicating minimal change in 47 million years. This absence of evolutionary change is an outstanding example of morphological and, probably, behavioral stasis
Paleobiology and taphonomy of fishes from the Late Cretaceous marine ecosystems of northeastern Mexico
No full textThe platy limestone deposit of Vallecillo in the northeastern Mexican state of Nuevo León is well known for its exceptionally well preserved faunal assemblage of vertebrate in addition to invertebrate fossils of Late Cretaceous (Latest Cenomanian-middle Turonian) age. Large marine reptiles are associated with cartilaginous as well as sarcopterygian and actinopterygian fishes that populated an open marine environment, at least 300 km away from the nearest coast. The most common fishes in the Vallecillo platy limestone member are the halecomorph needle fish Rhynchodercetis yovanovitchi, the teleost Tselfatia formosa, the pycnodont Nursallia gutturosum and the pachyrhizodont fish Goulmimichthys roberti.
Goulmimichthys roberti is a fusiform taxon that resembles modern tunas or mackerels. The fish reached a maximum length of 650 mm and is interpreted as a sustainable high-speed swimmer that formed schools in the pelagic. 177 individuals from Vallecillo were reviewed including 11 specimens from deposits near Múzquiz in Coahuila, about 400 km to the north of Vallecillo. These latter deposits reflect significantly more shallow and more near-shore environments extending the stratigraphical and environmental range of the taxon previously known from the Cenomanian to Santonian. Goulmimichthys roberti may thus have migrated between shallow environments and the pelagic. Taphonomic analyses point to articulated and complete specimens in both deposits, Vallecillo and Múzquiz, excluding a phase of carcass transportation. Different embedding positions suggest that the sea bottom of the northern (Múzquiz) deposits must have been more soften. Specimens from Vallecillo are majorly preserved with open mouth and spread-out fins which is interpreted as a result of respiratory stress associated with anoxic sea bottom conditions. The oxygen-deficient bottom also excluded scavengers and favored preservation. Specimens from Múzquiz were rapidly phosphatized preserving additional details, and corpses were covered in a soft mud sediment that prevented the carcass to turnover into a lateral position as seen in Vallecillo.
During the revision of G. roberti, the first Cretaceous isopod was revealed on a specimen from Vallecillo. The isopod is directly attached to the skull of the fish host and slightly twisted exposing the right body side. The isopod is nearly complete with most of the appendages allowing for an assignation to a new species of Cymothoidae named Mothocya vallecillae. A parasitic lifestyle is based on hook-like distal articles on all appendages (dactyli) as well as the position on the host, close to the gills. Modern Mothocya populate the branchial cavity of the host and feed on tissue, blood and mucus. A scavenging mode of life appears unlikely for M. vallecillae due to the anoxic bottom conditions reported from Vallecillo and the preservation of host and parasite which exclude the interference of scavengers. Mothocya vallecillae is of special interest because of the direct association to G. roberti which belongs to an pelagic ecosystem. Parasitic isopods directly attached to the fish host are presently only reported from Solnhofen in Germany.
The teleost Tselfatia formosa is a frequent member of the Vallecillo fish assemblage. The fish resembles modern fan fishes and is characterized by extraordinary long dorsal and anal fins, pseudo fulcra on the main rays of the unpaired fins, and small pectorals above the ventral column. A review of 149 specimens revealed two different body shape types which are interpreted as sexual shape dimorphism excluding ontogenetic variation. Deeply keeled specimens are interpreted as females that are twice as long as high compared to torpedo-shaped males which are three times longer than wide. The teleost is frequently articulated and complete and the unpaired fins are retracted behind modified scales which allow for comparison to extant fan fishes (e.g. Pteraclis and Pterycombus). A membrane between the fin rays is concluded due to fin preservation and arrangement. Taphonomic analyses suggest that Tselfatia formosa inhabited deeper water environments similar to recent fan fishes
Occlusion and Function of Triconodont Dentitions
Get PDFOver the last decades, many studies have focused on the tribosphenic molar and its functional aspects because it is considered to be a key innovation in mammalian evolution. Early triconodont dentitions have been examined to a lesser degree, despite being the plesiomorphic mammalian tooth morphology and, therefore, closely linked to the evolution of precise occlusion and food processing, which contributed to the evolution of endothermy. The majority of these studies were limited to descriptions and two-dimensional modeling. In this thesis, micro-computed tomography (µ-Ct) and 3D models were used to test existing occlusal models and to analyze the dental function of the different triconodont molar morphologies. The triconodont molar is characterized by three linearly aligned main cusps a/A, b/B, and c/C. It is the characteristic molar pattern for the non-mammalian Mammaliaformes Morganucodonta and the early-diverging crown-group Mammalia Eutriconodonta, which were subjects of this study.
The early-diverging mammaliaforms Morganucodon watsoni, Megazostrodon rudnerae, and Erythrotherium parringtoni had a primarily orthal occlusal path. Differences in the occlusion of the main cusps of Morganucodon compared to the embrasure occlusion of Megazostrodon and Erythrotherium were confirmed with the Occlusal Fingerprint Analyser (OFA). The occlusion of Morganucodon further showed variation in trajectory and cusp placement. The dentitions of Morganucodonta were well adapted to piercing and shear-cutting. ‘Shearing flanks’, which were the focus of previous studies, seemed to be rather a result of attrition, than functional areas in themselves.
Positioning of the upper molars within the maxilla of Morganucodon suggests a predetermined tooth placement to allow space for the lower dentition. These results are in contrast to previous hypotheses that stated that Morganucodon relied on extensive wear in order to form a precise occlusion.
While the molars of Morganucodonta emphasize the piercing capability with large, isolated cusps, the molars of Triconodontidae have a homogenous cusp-valley system that formed a continuous fore-aft crest that linked the entire molar series in a zig-zag pattern. It thus combines traits linked to both carnivorous diets (e.g. fore-aft cutting edges) and insectivorous diets (transverse crests and lobes). The molar series of triconodontids was highly uniform and adapted to a precise fit; lower molar cusps were self-sharpening within the valleys between upper molar cusps. While the high degree of precision ensured good cutting capabilities, its uniformity likely put the dentition under greater evolutionary constraints than other molar types with more heterogeneous cusp morphologies. This explains the stereotyped nature of the triconodontid molar, which underwent little change during the 60–85 Ma range of the family. Contrary to previous studies, embrasure occlusion was confirmed for Triconodontidae based on the OFA analysis. Embrasure occlusion can be therefore considered the universal occlusal mode for all taxa with triconodont molars with the exception of few Morganucodonta. Additionally, sequential tooth replacement was confirmed for Triconodontidae, which is in accordance with their phylogenetic position as early-diverging crown Mammalia. A unique pattern, on the other hand, is the development of m4 within the lingual side of the coronoid process, well above the tooth row of Triconodon. It was subsequently accommodated in the active tooth row via unusually prolonged and localized growth of the posterior part of the mandible (and, by implication, the base of the skull rostrum), with the m4 remaining in position and not erupting upward. This pattern is also seen among some later triconodontids and appears to be unique to the family. Over the course of this study, a new species of Triconodontidae Triconodon averianovi was described based on the partially reduced m4, its small p4, and gracile canine.
Gobiconodontidae, a clade of early crown-group Mammalia, are unique among Mesozoic mammals due to their large size, the replacement of their molariforms, and carnivorous diet. A type of embrasure occlusion was present that caused extensive wear and resulted in deep grooves between the upper molars. The occlusion is centered around mesiodistally oriented crests. They form in the course of increased wear that results in the loss of the smaller b/B and c/C cusps and extend from the tip of the large a/A cusps to the base of the molariforms. These crests provide the main cutting capability during the single-phased power stroke. Gobiconodontidae and Triconodontidae both share mesiodistally oriented crests, a faunivorous diet, as well as lingually inclined upper molars. However, the occlusion of Gobiconodontidae differs from the precise uniform system of Triconodontidae. Its primary focus is on the formation of long crests at the costs of tooth material. Given the large size of Gobiconodontidae, it seems likely that bite force was emphasized over precision. This interpretation is in agreement with the previous hypothesis that the replacement of the molariforms might have been necessary to compensate for the loss of tooth material.
The molars of all taxa, with a preserved maxilla, observed in this study were lingually inclined within the tooth row. This is interpreted as a mechanism to reduce the amount of roll required to keep the teeth in contact during occlusion
Soft tissue preservation in amber : a comparative study on the taphonomy and limits of fossilisation of resin embedded arthropods
Get PDFThis doctoral thesis deals with the limits of morphological and biomolecular preservation of fossils in amber and provides new information on their taphonomy. A particular focus lies on arthropod inclusions from Cambay and Zhangpu amber deposits, which both are chemically distinct from previously studied amber occurrences.
For the first time, subcellular structures could be evidenced in fossils from Eocene Cambay amber from India with electron microscopic methods. An examination of arthropods from Miocene Zhangpu amber from China shows that the frequency and extent of internal tissue preservation is not randomly distributed, but impacted by a combination of organismal characteristics and original resin chemistry. Muscle tissue, tracheal remains, and nervous tissue are the most commonly preserved, whereas abdominal tissue is infrequently detectable. This pattern is explained by an infiltration of volatile resin compounds along the tracheal system of entrapped arthropods.
Chemical analyses revealed that amber fossils can be exposed to mineral precipitations of calcite and quartz, which shows that the geological environment can have a strong influence on the potential of tissue or biomolecular preservation. This is further confirmed by a lizard bone from Dominican amber in which the original bioapatite was transformed into fluorapatite. Raman spectra of the same specimen showed an intense degradation of collagen into amorphous carbon compounds, indicating a lack of intact biomolecules.
In contrast to this, original single amino acids are extracted from Cambay and Zhangpu amber fossils which still enable conclusions about their phylogeny. Previous studies and the results of this thesis suggest that amino acids represent the limit of peptide preservation in amber. With respect to DNA preservation in amber, it is shown that intact DNA can be retrieved from extant resin-embedded arthropods. This provides an initial basis for step-by-step approaches towards the DNA preservation limit in amber. Numerous details regarding fossilisation in amber have not yet been investigated and hold great potential for future studies.Diese Doktorarbeit befasst sich mit den Grenzen der morphologischen und biomolekularen Erhaltung von Fossilien in Bernstein und liefert neue Informationen zu ihrer Taphonomie. Ein besonderer Schwerpunkt liegt auf Arthropodeneinschlüssen aus den Bernsteinvorkommen von Cambay und Zhangpu, welche sich chemisch von zuvor untersuchten Bernsteinablagerungen unterscheiden. Dabei konnten zum ersten Mal anhand elektronenmikroskopischer Methoden subzelluläre Strukturen in Fossilien aus dem eozänen Cambay-Bernstein aus Indien nachgewiesen werden. Eine Untersuchung von Arthropoden aus dem miozänen Zhangpu-Bernstein aus China zeigt, dass die Häufigkeit und das Ausmaß der Erhaltung der inneren Gewebe nicht zufällig verteilt sind, sondern in erster Linie durch eine Kombination von organismischen Eigenschaften und ursprünglicher Harzchemie beeinflusst werden. Muskelgewebe, Tracheenreste und Nervengewebe sind am häufigsten erhalten, wohingegen abdominales Gewebe seltener nachweisbar ist. Dieses Muster wird durch das Eindringen flüchtiger Harzverbindungen entlang des Tracheensystems eingeschlossener Arthropoden erklärt.
Chemische Analysen ergaben, dass Bernsteinfossilien mineralischen Ausfällungen von Calcit und Quarz ausgesetzt sein können, was zeigt, dass die geologische Umgebung einen starken Einfluss auf das Potenzial der Erhaltung von Gewebe oder Biomolekülen haben kann. Dies wird weiter durch einen Eidechsenknochen aus Dominikanischem Bernstein bestätigt, in dem der ursprüngliche Bioapatit in Fluorapatit umgewandelt ist. Raman-Spektren derselben Probe zeigten einen intensiven Abbau von Kollagen zu amorphen Kohlenstoffverbindungen, was auf die Abwesenheit intakter Biomoleküle hinweist.
Im Gegensatz dazu können ursprüngliche einzelne Aminosäuren von Fossilien aus Cambay und Zhangpu Bernstein extrahiert werden, die immer noch Rückschlüsse auf deren Phylogenie ermöglichen. Frühere Studien und die Ergebnisse dieser Arbeit legen nahe, dass Aminosäuren die Grenze der Konservierung von Peptiden in Bernstein darstellen.
In Bezug auf DNA-Konservierung in Bernstein wird gezeigt, dass intakte DNA zumindest aus heutigen, in Harz eingebetteten Arthropoden gewonnen werden kann. Dies bietet eine erste Grundlage um schrittweise die Konservierungsgrenze von DNA in Bernstein zu ermitteln. Zahlreiche Details im Hinblick auf die Fossilisation in Bernstein sind noch nicht untersucht worden und beinhalten ein großes Potenzial für zukünftige Studien
Diversity of feeding and pollination strategies of Mesozoic beetles
Get PDFBeetles (Order: Coleoptera) as the most diverse and successful animals on the earth, comprise about 400,000 species, constituting almost 40% of described insects and a quarter of all animal species. They are distributed in almost every terrestrial natural habitat today, with various feeding preferences. Approximately 90% of the species in Coleoptera emerged in the Mesozoic, especially during the Jurassic-Cretaceous period. At the same time, vegetation type on the earth was shifting significantly — angiosperms (flowering plants) rapidly replacing the dominating gymnosperms, an event which Charles Darwin called the “Abominable Mystery”. The dramatic environmental and nutritional change could have impacted the interaction between beetles and related plant groups. The evolution of beetles may have also influenced the angiosperm radiation, e.g. through zoophilous pollination.
The studies in this thesis demonstrate the remarkable feeding strategies and ecological diversity of Mesozoic beetles. Fourteen species of seven families from Karabastau Formation, Daohugou Biota, Burmese amber and Baltic amber are described, ranging from Early Jurassic to Eocene. The co-evolution between beetles and vegetation environments is discussed. Based on the continuous fossil records of the family Mordellidae, the early evolution trend of a typical beetle-flower ecology is outlined. Hypothetically, insect pollination contributes largely to the diversity of flowering plants, and is essential to the Cretaceous radiation of angiosperms. Angimordella burmitina Bao, 2019 and the associated tricolpate pollens provides direct evidence of insect pollination of Cretaceous eudicots ~99 million years ago, extending the record of insect mediated angiosperm pollination at least 50 million years earlier. The great angiosperm radiation in mid-Cretaceous acted as a driving force for the replacement of earth surface vegetation. By this time, nutrition groups as gymnosperms, fern, are also changed relatively, which also imply the associated beetle taxa. Praezolodinus pilosus and Cretoptomaphagus microsoma provide rare records of bottom forest ecosystem: an association of fern habited beetle and scavenger. Wood-borer and fungivorous beetles are abundant in Burmese amber, similar to the extant beetle species. With more and more flora and fauna inclusions discovered from Burmese amber, it is possible to draw a big picture of the Burmese forest back in. We can generally understand the forest vertical eco-components and the inner relationships of the ecosystem. The Waipoua forest could be the extant reference ecosystem. However, it should be pointed out that it is easy to underestimate the complexity of the ecosystem, when performing a comparative study of paleoecology in the future
Analysis of functional morphology in carnassial dentitions (Carnivora, Dasyuromorphia, Hyaenodonta)
Get PDFFunctional and structural changes in the evolution of carnassial teeth in the Carnivora, Dasyuromorphia and Hyaenodonta are analyzed by a combination of Occlusal Fingerprint Analysis, Dental Topographic Analysis (quantification of crown curvature by Dirichlet Normal Energy) and 3D geometric morphometrics. Carnassialization can be described as an increasing simplification of tooth structure and function. The documented tooth wear and virtual simulation of the power stroke indicate a functional shift from weakly to higher carnassialized teeth, where the cutting function is emphasized and the crushing function is reduced. In some taxa, a trenchant talonid with a hypoflexid groove evolves, performing a similar shearing and guiding function as the hypoflexid in pretribosphenic teeth, such as in dryolestids. This observation is consistent with the hypothesis that carnassialization is a simplification and structural reverse of the tooth crown to an ancestral pretribosphenic condition. The Dental Topographic Analysis of lower carnassials shows low crown curvature values in higher carnassialized teeth. The decrease of crown curvature with increasing carnassialization can be explained with the reduction of cusps and crests, which results in a simplified crown relief. The geometric morphometric analysis of lower carnassials indicates a convergent simplification of the crown relief connected to carnassial blade enlargement and talonid reduction. Along the lower tooth row of dasyuromorphs (m2 - m4) and hyaenodonts (m1 - m3) the most distal carnassial is the most carnassialized (principal carnassial), and in most taxa with overall higher carnassialized teeth, carnassialization successively increases from the mesial to the distal tooth position. Additionally, a shape difference connected to the phylogeny, showing a mesio-distal elongation of the carnassial unique to carnivorans with weakly carnassialized teeth, is indicated. The mesio-distal tooth elongation, present only in caniforms and unspecialized feliforms (viverrids and herpestids), enables the presence of a functional crushing talonid basin and a longitudinally oriented carnassial blade, performing an efficient carnassial cutting. As indicated by an ancestral state reconstruction, this condition may be plesiomorphic for the Carnivora and may have provided them with an advantage in terms adaptive versatility, as it did not evolve in dasyuromorphs or hyaenodonts
Fossil record and new aspects of evolutionary history of Calcium biomineralization and plant waxes in fossil leaves
Get PDFCalcium oxalate (CaOx) is one of the most common bio-minerals in extant plants. It plays a major role in a better understanding of plant taphonomy, environmental effects and evolution of calcium minerals in fossil plants. Although CaOx is common in extant leaves of many plant groups, the fossil record of CaOx in fossil leaves is almost completely unknown, due to the imperfect preservation of CaOx bio-minerals and the disintegration of CaOx crystals during fossilization. Recognition of the remains of CaOx in fossil leaves can be challenging. The record of casts of CaOx in fossil leaves from basal plants, gymnosperms and angiosperms has been established to reconstruct the evolutionary history of CaOx from the Devonian to the Neogene.
The present thesis aims to introduce the different distribution patterns of CaOx traces (individual crystals and druses) in fossil leaves and to compare the substituted or residual chemical components in their casts in fossil leaves from basal to higher plant groups. In order to achieve this goal, both fossil and modern (for extant groups) leaves of seed ferns, pteridophytes (ferns), gymnosperms (cycadales, ginkgophytales, conifera) and angiosperms have been examined. Fossil samples were borrowed from different sites and ages from natural history museums in Germany. Extant samples were collected in the Botanical Garden, University of Bonn. Light microscopy (LM) and Scanning Electron Microscopy (SEM) were utilized to clarify the distribution of CaOx casts in both fossil and fresh leaves.
The results show that CaOx is almost non-existent in modern ferns. In seed ferns, the casts of former CaOx crystal druses were observed under a carbon layer in a regular distribution pattern with a size of approximately 20 µm. CaOx in cycads and ginkgophytes appeared as aggregated forms or druses in the phloem. Druses in ginkgophyte measured up to 100 µm. Conifera show a different trend: crystals occur as individuals and more or less small size (10-12 µm) under the cuticle. In angiosperms CaOx appears commonly and in diverse forms.
In conclusion, the presence of the CaOx as an important chemical factor in plants is reported from primitive seed ferns to the modern gymnosperms and angiosperms. The distributional pattern of CaOx in each major group of plants is different and can be affected by environmental factors and physiological aspects in plants
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