Extinct Eocene Research Articles

New records of the subgenus Atomaria (Anchicera) Thomson, 1863 from European amber with description of the new species

ABSTRACT One new extinct species of the genus Atomaria Stephens, 1829 is described and illustrated: A. (Anchicera) telnovi sp. nov. from Rovno amber. It is the sixth species of the subgenus Anchicera in Eocene amber; two-thirds of all species and two-thirds of all reported Eocene amber silken fungus beetle specimens belong to this subgenus. The reasons for the relative abundance of Anchicera in the Eocene fossil resins are discussed. A key to extinct Eocene species of Atomaria is provided.

Two new fossil species of the genus Atomaria Stephens (Coleoptera: Cryptophagidae) from Eocene European amber with a key to species described from fossil resins

Two new extinct species of the genus Atomaria Stephens, 1829 are described and illustrated: A. (Anchicera) alekseevi sp. nov. from Baltic amber and A. (Anchicera) perkovskyi sp. nov. from Rovno amber. A key to extinct Eocene species of Atomaria is provided.

CT-scans of capsules from the Clarno Formation (Oregon, USA) reveal an extinct Eocene theaceous taxon

The economically important but relatively small family Theaceae can be traced back to the Late Cretaceous and is found today in the Western Hemisphere and Asia. Theaceous fruits are generally loculicidal capsules and have been found as fossils throughout the Northern Hemisphere. Using reflected light and μCT-scanning, we recognize Anubiscarpon andersonae MA Smith et Manchester gen. et sp. nov. from the middle Eocene Clarno Formation of north central Oregon, based on five-valved, loculicidal capsules with a central columella, persistent perianth and pedicel, preserved as impressions in lacustrine shale. Its most distinctive feature is its apically clefted valves which are not seen in any other species of the family. Anubiscarpon augments our understanding of former morphological diversity in the Theaceae

The Mastigitae genus †Baltostigus in Upper Eocene Rovno amber(Coleoptera: Staphylinidae: Scydmaeninae).

Three species of the extinct Eocene genus Baltostigus (Mastigitae: Baltostigini) were known in Baltic amber from Poland, Lithuania and Russia. In Rovno amber, although it was relatively well-studied, only one Mastigitae genus and species was recorded, belonging to Leptochromini. We report the occurrence of Baltostigus in the area of the present day Ukraine during the Eocene, on the basis of three inclusions in Rovno amber. One specimen belongs to a newly described species, Baltostigus substriatus sp. n.; two specimens are putatively identified as Baltostigus cf. horribilis, and may represent females of this species. However, further study based on more specimens is necessary to clarify the identity of these specimens.

Western Davis Strait, a volcanic transform margin with petroliferous features

Abstract We present a compilation of the western Davis Strait region offshore southeastern Baffin Island, Nunavut, Canada with new subsurface geological structural details and observations regarding past hydrocarbon occurrences from scientific and commercial exploration. This consists of seismic mapping with archival data correlated with a filtered marine Bouguer anomaly gravity compilation and magnetic data sets covering northern Saglek Basin, the western part of the Lady Franklin Basin and the Ungava Fault Zone from south of Baffin Bay. A regional seismic horizon for mapping basin architecture comes from the top of the Paleogene volcanic syn-magmatic zone, where pervasive volcanic flows and intrusions are intermingled with the sedimentary section. The seismic depth map to the top of the regional volcanic seismic horizon shows pre-rift sedimentary basins having maximum depths of approximately 4–5 km flanking the shallower Ungava Fault Zone. Correlation of Bouguer anomaly gravity and magnetic data interpretations with the seismic mapping, indicate that over some areas true crystalline basement is deeper than can be determined by reflection seismic, as the base of the syn-magmatic section is not resolvable for seismic mapping. Extensive Paleogene mafic intrusives and extrusive basalts dominate the architecture of this volcanic rifted margin as seen by the dominant high amplitude magnetic anomalies associated with many deeper structures. The over 250 km long Davis Strait Fault is recognised as the key structural element of the Ungava Fault Zone (UFZ) and valley complex. The adjoining Davis Strait High maps on seismic as a continuous structure running the length of Davis Strait plunging southwards to a Bouguer gravity high feature that terminates the western end of the extinct Eocene spreading zone south of Davis Strait. This horn shaped structural feature establishes the presence of an accommodation zone with multiple faults and localised thrust faulting as required to fit the complex mechanics for strike-slip motion that occurs along the south end of this transform fault system. The revised marine Bouguer anomaly gravity data set also defines two new, near shore grabens east of Cumberland Sound, the southern Tariut Basin and the northern Imaqpik Basin, each extending over 100 km in length with sediment thicknesses of at least 4 km. These pre-rift basins most likely originate from the Paleozoic based on seafloor dredge and nearby shallow drill cores from previous studies. The hydrocarbon charge of a previously unexplained petroliferous shallow marine drill core that is adjacent the eastern edge of the Tariut Basin is attributed to Paleozoic source rocks that have undergone enhanced thermal maturation from sill intrusion associated with rifting. The Imaqpik Basin shows strong evidence of a hydrocarbon system from the proximity of clustered interpreted sea surface oil slicks, mapped from satellite radar images, and a local zone of anomalously high dissolved methane measured within the water column that originates from the seafloor immediately east of Cape Dyer at the northern limit of that basin. The overlying Cape Dyer flood basalt field extends from limited onshore exposures into the offshore and maps with magnetic data over an area of approximately 13,000 km2. This extrusive feature and it's implicit underlying intrusive components are likely the unconventional heat source for the anomalous enhanced thermal maturation of Paleozoic to Paleogene source rocks in these pre-rift basins that host this previously unrecognised petroleum system.

Taimyraphes gen. nov., the first glandulariine ant-like stone beetle from Santonian Taimyr amber (Coleoptera: Staphylinidae: Scydmaeninae)

The Glandulariini includes 78 genera comprising over 70% of the extant nominal species of Scydmaeninae. Extant members of this tribe are ubiquitous in forests of all continents. Because of small size of most species (often below 2 mm), taxonomic problems accumulated over the past 200 years, and scarcity of fossils with exposed ventral structures that are crucial for generic diagnoses, Glandulariini are rarely subjects of palaeontological studies. Consequently, only five Cretaceous genera have been described, mostly those that can be diagnosed by conspicuous, often bizarre autapomorphies. We report a finding of the first Santonian member of Glandulariini, Taimyraphes microscopicus gen. et sp. nov., based on a specimen in Taimyr amber from Yantardakh. This is also the smallest described Cretaceous glandulariine beetle, with the body length merely ∼0.8 mm. The fossil preservation state allows for examination of mesoventral structures, rarely exposed in such small specimens. We conclude that Taimyraphes does not show any novel character states; it is defined, as many extant Glandulariini, by a unique combination of synapomorphies that, separately or in different sets, can be found in its extant relatives. The Santonian Taimyraphes of Taimyr shares a similar body form with the extinct Eocene Rovnoscydmus of Ukraine, and with the extant Neotropical Amimoscydmus and Heteroscydmus, Nearctic Delius and Neladius, cosmopolitan Microscydmus, or Western Palaearctic Leptocharis. As most Cretaceous Glandulariini are known from Cenomanian, and only one from Turonian, the first Santonian fossil is important to fill gaps in our knowledge of the evolution of Scydmaeninae, a group of beetles that apparently diversified into the extant tribes in or before Early Cretaceous.

Oldest Finch-Beaked Birds Reveal Parallel Ecological Radiations in the Earliest Evolution of Passerines

Beak shape plays a key role in avian radiations and is one of the most intensely studied aspects of avian evolution and ecology [1-4]. Perhaps no other group is more closely associated with the study of beak shape than Passeriformes (passerines or perching birds), the most species-rich ordinal clade of modern birds. However, despite their extraordinary present-day diversity, our understanding of early passerine evolution has been hindered by their sparse fossil record [5, 6]. Here, we describe two new species of early Eocene stem passerines from the Green River Formation of the United States and the Messel Formation of Germany. These species are the oldest fossil birds to exhibit a finch-like beak and provide the earliest evidence for a diet focused on small, hard seeds in crown birds. Given that granivory is a key adaptation that allows passerines to exploit open temperate environments, it is notable that both species occurred in subtropical environments [7, 8]. Phylogenetic analyses place both species within the Psittacopedidae, an extinct Eocene clade of zygodactyl stem passeriforms that also includes the slender-beaked nectarivorous Pumiliornis, the short-beaked Psittacopes, and the thrush-beaked Morsoravis. Our results reveal that stem passerines attained a diversity of beak shapes paralleling manyof the morphotypes present in extant passerine finches, thrushes, and sunbirds, more than 35 million years before these morphotypes arose in the crown group. Extinction of these ecologically diverse fossil taxa may be linked to more sophisticated nest construction in anisodactyl crown passerines versus cavity-nesting in Eocene zygodactyl stem passerines [9].

New long-horned caddisflies in Eocene Baltic amber (Insecta, Trichoptera)

We describe two new extinct caddisflies, Electroadicella kuenowi sp. nov. and Triaenodes simoni sp. nov., embedded in Baltic amber. Both species belong to the tribe Triaenodini and enlarge the family Leptoceridae to a remarkable number of 18 extinct Eocene species from Baltic amber. The extinct Electroadicella and the extant Triaenodes are possibly closely related, by a distinct synapomorphy, a recurved process from the basal plate of the inferior appendages of the ninth abdominal segment in the male genitalia.

Structural variability of the Tonga-Kermadec forearc characterized using robustly constrained geophysical data

Subducting bathymetric anomalies enhance erosion of the overriding forearc crust. The deformation associated with this process is superimposed on pre-existing variable crustal and sedimentary structures developed as a subduction system evolves. Recent attempts to determine the effect and timescale of Louisville Ridge seamount subduction on the Tonga-Kermadec forearc have been limited by simplistic models of inherited overriding crustal structure that neglect along-strike variability. Synthesis of new robustly tested seismic velocity and density models with existing datasets from the region, highlight along-strike variations in the structure of the Tonga-Kermadec subducting and overriding plates. As the subducting plate undergoes bend-faulting and hydration throughout the trench-outer rise region, observed oceanic upper- and mid-crustal velocities are reduced by ∼1.0 km s−1 and upper mantle velocities by ∼0.5 km s−1. In the vicinity of the Louisville Ridge Seamount Chain (LRSC), the trench shallows by 4 km and normal fault throw is reduced by > 1 km, suggesting that the subduction of seamounts reduces plate deformation. We find that the extinct Eocene frontal arc, defined by a high velocity (7.0–7.4 km s−1) and density (3.2 g cm−3) lower-crustal anomaly, increases in thickness by ∼6 km, from 12 to > 18 km, over 300 km laterally along the Tonga-Kermadec forearc. Coincident variations in bathymetry and free-air gravity anomaly indicate a regional trend of northward-increasing crustal thickness that predates LRSC subduction, and highlight the present-day extent of the Eocene arc between 32° S and ∼18° S. Within this framework of existing forearc crustal structure, the subduction of seamounts of the LRSC promotes erosion of the overriding crust, forming steep, gravitationally unstable, lower-trench slopes. Trench-slope stability is most likely re-established by the collapse of the mid-trench slope and the trenchward side of the extinct Eocene arc, which, within the framework of forearc characterisation, implies seamount subduction commenced at ∼22° S.

The extinct Baltic amber genus Propelma Trjapitzin, a valid genus of Neanastatinae (Hymenoptera,Eupelmidae).

The extinct Eocene Baltic amber genus Propelma Trjapitzin 1963 is removed from synonymy under Eupelmus Dalman 1820 (Hymenoptera, Eupelmidae, Eupelminae) and treated as a valid genus within Neanastatinae Kalina 1984 based on examination of the holotype female of Propelma rohdendorfi Trjapitzin. Propelma rohdendorfi is redescribed, illustrated by photomacrographs, and compared to other described extant and extinct genera of Neanastatinae. Taxonomic, morphological and geological diversity of Neanastatinae relative to Eupelminae and Calosotinae is also discussed relative to potential age of the subfamily.

An extinct Eocene taxon of the daisy family (Asteraceae): evolutionary, ecological and biogeographical implications

An extinct Eocene taxon of the daisy family (Asteraceae): evolutionary, ecological and biogeographical implications

An extinct Eocene taxon of the daisy family (Asteraceae): evolutionary, ecological and biogeographical implications

Morphological, molecular and biogeographical information bearing on early evolution of the sunflower alliance of families suggests that the clade containing the extant daisy family (Asteraceae) differentiated in South America during the Eocene, although palaeontological studies on this continent failed to reveal conclusive support for this hypothesis. Here we describe in detail Raiguenrayun cura gen. & sp. nov., an exceptionally well preserved capitulescence of Asteraceae recovered from Eocene deposits of northwestern Patagonia, Argentina. The fossil was collected from the 47·5 million-year-old Huitrera Formation at the Estancia Don Hipólito locality, Río Negro Province, Argentina. The arrangement of the capitula in a cymose capitulescence, the many-flowered capitula with multiseriate-imbricate involucral bracts and the pappus-like structures indicate a close morphological relationship with Asteraceae. Raiguenrayun cura and the associated pollen Mutisiapollis telleriae do not match exactly any living member of the family, and clearly represent extinct taxa. They share a mosaic of morphological features today recognized in taxa phylogenetically close to the root of Asteraceae, such as Stifftieae, Wunderlichioideae and Gochnatieae (Mutisioideae sensu lato) and Dicomeae and Oldenburgieae (Carduoideae), today endemic to or mainly distributed in South America and Africa, respectively. This is the first fossil genus of Asteraceae based on an outstandingly preserved capitulescence that might represent the ancestor of Mutisioideae-Carduoideae. It might have evolved in southern South America some time during the early Palaeogene and subsequently entered Africa, before the biogeographical isolation of these continents became much more pronounced. The new fossil represents the first reliable point for calibration, favouring an earlier date to the split between Barnadesioideae and the rest of Asteraceae than previously thought, which can be traced back at least 47·5 million years. This is the oldest well dated member of Asteraceae and perhaps the earliest indirect evidence for bird pollination in the family.

Algorithmic approaches to aid species' delimitation in multidimensional morphospace

BackgroundThe species is a fundamental unit of biological pattern and process, but its delimitation has proven a ready source of argument and disagreement. Here, we discuss four key steps that utilize statistical thresholds to describe the morphological variability within a sample and hence assess whether there is evidence for one or multiple species. Once the initial set of biologically relevant traits on comparable individuals has been identified, there is no need for the investigator to hypothesise how specimens might be divided among groups, nor the traits on which groups might be separated.ResultsPrincipal components are obtained using robust covariance estimates and retained only if they exceed threshold amounts of explanatory power, before model-based clustering is performed on the dimension-reduced space. We apply these steps in an attempt to resolve ongoing debates among taxonomists working on the extinct Eocene planktonic foraminifera Turborotalia, providing statistical evidence for two species shortly before the lineage's extinction near the Eocene/Oligocene boundary.ConclusionBy estimating variance robustly (samples containing incipient species are unlikely to be scaled optimally by means and standard deviations) and identifying thresholds relevant to a particular system rather than universal standards, the steps of the framework aim to optimize the chances of delineation without imposing pre-conceived patterns onto estimates of species limits.

A phylogeny of the fossil and extant zeiform‐like fishes, Upper Cretaceous to Recent, with comments on the putative zeomorph clade (Acanthomorpha)

Tyler, J. C. & Santini, F. (2005). A phylogeny of the fossil and extant zeiform‐like fishes, Upper Cretaceous to Recent, with comments on the putative zeomorph clade (Acanthomorpha). —Zoological Scripta,**, ***–***.A phylogenetic hypothesis based on 107 morphological characters is proposed for a data set of 43 taxa. Thirty‐three are extant and belong to the orders Zeiformes (20 taxa), Caproiformes (2), Tetraodontiformes (2), Beryciformes (3), Stephanoberyciformes (3) and Perciformes (3). Ten are fossil taxa previously assigned to the Zeiformes (3), Caproiformes (1), Tetraodontiformes (2), Perciformes (1), and to two extinct Eocene families, the Sorbinipercidae (2) and the Zorzinichthyidae (1). This analysis indicates the existence of a previously undocumented clade formed by the families Sorbinipercidae + Zorzinichthyidae that may be related to the tetraodontiforms. It also shows that two uppermost Palaeocene species,Archaeozeus skamolensisandProtozeus kuehnei, sequentially represent the two most basal lineages of zeiforms, whereas the most ancient known zeiform, the Upper CretaceousCretazeus rinaldii, belongs within the clade of extant species in a polytomy with many other zeiform lineages. A reduced data set of 25 mostly zeiform taxa, after the removal of most outgroups, shows at least weak support forCretazeusbeing nested deeply within the extant zeiforms; such a placement would indicate that at least six lineages of zeiforms were present during the Upper Cretaceous, and survived the Cretaceous/Tertiary (K/T) extinction to radiate in Cenozoic seas.