The long‐term history of dispersal among lizards in the early Eocene: new evidence from a microvertebrate assemblage in the Bighorn Basin of Wyoming,USA

Abstract: Early Eocene mammal faunas of North America were transformed by intercontinental dispersal at the Paleocene–Eocene boundary, but lizard faunas from the earliest Eocene of the same area were dominated by immigrants from within the continent. A new lizard assemblage from the middle early Eocene of Wyoming sheds light on the longer‐term history of dispersal in relation to climate change. The assemblage consists of three iguanid species (including two new species possibly closely related to living Anolis), Scincoideus, ‘Palaeoxantusia’, four anguids, two species of an undescribed new anguimorph clade, Provaranosaurus and a varanoid (cf. Saniwa). Most North American glyptosaurin glyptosaurines are now referred to Glyptosaurus, and Glyptosaurus hillsi is given a new diagnosis. Scincoideus is otherwise known only from the mid‐Paleocene of Belgium, and the specimens described here are the first to document intercontinental dispersal to North America among lizards in the early Eocene. Like in mammals, some immigrant lizard lineages first appearing in the Bighorn Basin in the earliest Eocene persisted in the area long after the Paleocene–Eocene thermal maximum, but other immigrants appear to have been restricted to the Paleocene–Eocene thermal maximum.     

The deciduous dentition and dental replacement in the Eocene bat Palaeochiropteryx tupaiodon from Messel: The primitive condition and beginning of specialization of milk teeth among Chiroptera

The deciduous dentition and tooth replacement pattern of Palaeochiropteryx tupaiodon from the early Middle Eocene of Messel, near Frankfurt, Germany, are described. Ontogenetic states include fetuses to subadults. The posterior portion of the deciduous dentition (dP3-4) still shows the primitive eutherian condition of molarization, while the anterior part (dI-dC) was already engaged in the evolution of the highly derived condition found in living bats for clinging to the mother's fur. A styliform and sharp anterior dentition is considered a prerequisite in earliest chiropteran evolution. The greatly modified milk teeth of all living bats developed in different clades by parallel evolution under high selective pressure. The tiny and, at initial stages, poorly calcified teeth are substantiated by a newly developed microradiographic technique which is described in detail.     

Deciduous Dentitions of Eocene Cebochoerid Artiodactyls and Cetartiodactyl Relationships

Deciduous lower premolars (milk teeth) of the Eocene artiodactyl family Cebochoeridae possess accessory denticles and are remarkably similar to both deciduous and adult teeth of the cetacean family Basilosauridae, suggesting that morphological characters of juvenile dentitions are important to understanding the phylogenetic origin of whales and morphological transitions in the cetartiodactyl lineage. Incorporation of these new characters into a larger phylogenetic analysis of morphological characters of artiodactyls, mesonychids, and basal and recent whales supports a monophyletic Cetartiodactyla, but does not directly support a whale–hippo relationship. However, the presence of accessory denticles on some artiodactyl dentitions weakens the morphological support for a monophyletic Artiodactyla, suggesting either that whales and cebochoerids may be more closely related than had been thought, or that cebochoerids share a developmental pathway with cetaceans.     

New carnivoraforms from the early Eocene of Europe and their bearing on the evolution of the Carnivoraformes

Two new mammalian carnivoraform species, Uintacyon hookeri sp. nov. and Quercygale smithi sp. nov., are described from the early Eocene of Europe. U. hookeri sp. nov. is recorded in Mutigny (MP8 + 9, PE IV), Avenay (MP8 + 9, PE V), Brasles, Condé‐en‐Brie (MP8 + 9) and Cuis (MP 10), while Q. smithi sp. nov. comes from Mutigny and Mancy (MP10). Because the two species are not recorded in earliest Eocene localities such as Dormaal and Le Quesnoy (MP7, PE I), it is proposed that they dispersed after the main phase of the Mammal Dispersal Event. U. hookeri sp. nov. supports the existence of terrestrial connections with North America, while Q. smithi sp. nov. implies possible faunal exchange with Asia. This evidence for the evolution of the Carnivoraformes supports: (1) a rapid decrease in their diversity after the Mammal Dispersal Event; and (2) the existence of a mammal turnover event in Europe during the early Eocene. The discovery of a new species of Quercygale, which is generally considered as the closest carnivoraform to the crown‐group Carnivora, shows that the genus had already lost the M₃ by the early Eocene and supports an important, but very poorly known, radiation of the carnivoraforms at least during the earliest early Eocene.     

Deciduous dentition eruption sequence of the laboratory-reared chimpanzee (Pan troglodytes)

Eruption sequence and age ranges for the maxillary and mandibular deciduous dentition were generated from serial dental study models from 28 laboratory-reared chimpanzees (Pan troglodytes). These data can serve as additional normative, baseline information for the evaluation of fetal insults on neonatal growth and development in the laboratory-reared chimpanzee.     

Deciduous dentition and eruption pattern in late Miocene Pachyrukhinae (Hegetotheriidae,Notoungulata) from La Pampa Province,Argentina

The study of juvenile remains of Paedotherium Burmeister from Cerro Azul Formation (La Pampa Province, Argentina; late Miocene) is presented. Upper and lower deciduous dentition (or permanent molars supposed to be associated with non-preserved deciduous teeth) are recognised. Several ontogenetic stages are distinguished among juveniles, according to the degree of wear and the replaced deciduous teeth. Besides, some morphological and metrical differences are observed along the crown height. Deciduous cheek teeth are high-crowned and placed covering the apex of the corresponding permanent tooth. The height of the crown and the degree of wear allow establishing the pattern of dental replacement of deciduous and permanent premolars in a posterior–anterior direction (DP/dp4–2 and P/p4–2), as well as the eruption of M/m3 before DP/dp4 is replaced. Some of the studied remains are recognised as young individuals of Tremacyllus Ameghino, but with complete permanent dentition, which leads to propose a different timing in the dental replacement with respect to Paedotherium; they also allow the establishment of an opposite premolar eruption pattern, from P/p2 to P/p4. This knowledge of the deciduous dentition of Paedotherium suggests the need of revising the morphological and metrical characters previously used for defining species within this taxon.     

Eocene Bird and Mammal Tracks from the Karaj Formation,Tarom Mountains,Northwestern Iran

A long continuous trackway of a shorebird (cf. Charadriipeda) and a suite of possible Pantodonta (?Corophydon) or Dinocerata tracks are reported from the Eocene Karaj Formation. Fossil footprints are still rare in Iran, described only from two Jurassic and three Tertiary sites. Thus the current record, the third in the Teritary, adds to a sparse record and increases the diversity of known track types.     

Taxonomic status of purported primate frontal bones from the Eocene Pondaung Formation of Myanmar

Two isolated cranial fragments from the late middle Eocene Pondaung Formation of central Myanmar have previously been interpreted as frontal bones of the amphipithecid primate Amphipithecus mogaungensis. Aside from a few maxillary fragments, these specimens provide the only potential source of information currently available regarding the cranial anatomy of Amphipithecidae. Were this taxonomic attribution correct, these specimens would indicate that amphipithecids retained numerous primitive skull features, including the absence of a postorbital septum, the retention of a voluminous olfactory chamber, and strong separation between the forebrain and the orbital fossa. However, several anatomical details observable on these specimens are incompatible with their attribution to any primate and strongly suggest that they cannot be ascribed to Mammalia. Particularly problematic in this regard are the extreme thickness of the dermal bone, the odd structure of the alleged "frontal trigon," and the mediolateral orientation and uniquely robust construction of the descending process of the frontal bone (which partially segregates the orbital and temporal fossae). Because these isolated elements can no longer be attributed to Amphipithecus, the anatomical, phylogenetic, and behavioral inferences regarding amphipithecid paleobiology that have been drawn from these specimens can no longer be sustained.     

Detection of the ADP-ribosyltransferase toxin gene (cdtA) and its activity in Clostridium difficile isolates from Equidae

Clostridium difficile is an antibiotic-associated emerging pathogen of humans and animals. Thus far three toxins of C. difficile have been described: an enterotoxin (ToxA), a cytotoxin (ToxB) and an ADP-ribosyltransferase (CDT). In the present work we describe the first isolation of CDT producing C. difficile from Equidae with gastro-intestinal disease. Out of 17 C. difficile strains isolated from Equidae, 11 were positive for the genes tcdA and tcdB encoding ToxA and ToxB. In addition four of these 11 isolates were positive for the cdtA gene encoding the catalytic subunit of the ADP-ribosyltransferase CDT. Interestingly none of the isolates derived from canines (41 isolates) and felines (4 isolates) harboured the cdtA gene. In C. difficile field isolates which contained the cdtA gene, ADP-ribosyltransferase activity could also be detected in culture supernatants indicating expression and secretion of CDT. All strains were associated with intestinal disorders, but no association was found for the occurrence of toxins with a specific clinical diagnosis.     

Molecular and microstructural inventory of an isolated fossil bird feather from the Eocene Fur Formation of Denmark

An isolated, yet virtually intact contour feather (FUM‐1980) from the lower Eocene Fur Formation of Denmark was analysed using multiple imaging and molecular techniques, including field emission gun scanning electron microscopy (FEG‐SEM), X‐ray absorption spectroscopy and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Additionally, synchrotron radiation X‐ray tomographic microscopy (SRXTM) was employed in order to produce a digital reconstruction of the fossil. Under FEG‐SEM, the proximal, plumulaceous part of the feather revealed masses of ovoid microstructures, about 1.7 μm long and 0.5 μm wide. Microbodies in the distal, pennaceous portion were substantially smaller (averaging 0.9 × 0.2 μm), highly elongate, and more densely packed. Generally, the microbodies in both the plumulaceous and pennaceous segments were aligned along the barbs and located within shallow depressions on the exposed surfaces. Biomarkers consistent with animal eumelanins were co‐localized with the microstructures, to suggest that they represent remnant eumelanosomes (i.e. eumelanin‐housing cellular organelles). Additionally, ToF‐SIMS analysis revealed the presence of sulfur‐containing organics – potentially indicative of pheomelanins – associated with eumelanin‐like compounds. However, since there was no correlation between melanosome morphology and sulfur content, we conclude these molecular structures derive from diagenetically incorporated sulfur rather than pheomelanin. Melanosomes corresponding roughly in both size and morphology with those in the proximal part of FUM‐1980 are known from contour feathers of extant parrots (Psittaciformes), an avian clade that has previously been reported from the Fur Formation.     

Fossil ectomycorrhizae from the Middle Eocene

Fossil ectomycorrhizae were found recently among permineralized plant remains in the middle Eocene Princeton chert of British Columbia. The ectomycorrhizae are associated with roots of Pinus and have a Hartig net that extends to the endodermis, a pseudoparenchymatous mantle, and contiguous extramatrical hyphae that are simple-septate. The mycorrhizal rootlets lack root hairs and dichotomize repeatedly to form large, coralloid clusters. Reproductive structures are absent. Based on the morphological characteristics, and the identity of the host, the closely related basidiomycete genera Rhizopogon and Suillus are suggested as comparable extant mycorrhizal fungi. These exquisitely preserved specimens represent the first unequivocal occurrence of fossil ectomycorrhizae and demonstrate that such associations were well-established at least 50 million years ago.     

Fossil water‐penny beetles (Coleoptera: Psephenidae: Eubrianacinae) from the Eocene of Europe,with remarks on their phylogenetic position and biogeography

Abstract: A species of water‐penny beetles is recorded from larval instars from the Middle Eocene Messel pit fossil site in Germany. This species clearly belongs to the psephenid subfamily Eubrianacinae, but its precise systematic affinities remain unclear. It is the second fossil species of this taxon recorded from Europe. The holotype of the first fossil species, Eubrianax vandeli Bertrand and Laurentiaux, 1963, is lost. The high number of fossil specimens from Messel allowed discussion of stratigraphic and spatial occurrence of the eubrianacine species in the Messel pit, but its larval ontogeny could not be unravelled. Because of the high number of fossils and their wide occurrence, it is inferred that the species from Messel gen. sp. 1 was an autochthonous faunal element of the Eocene Lake Messel, which might indicate that some parts of the former Lake Messel had a shore area with stones. The analysis of the phylogenetic position of both Eocene eubrianacine species showed that their phylogenetic placement cannot be resolved because preservational influences limit the evaluation of characters. The historical biogeography of Psephenidae and Eubrianacinae is analysed and discussed. The fossil record shows that psephenid beetles have fossil members occurring outside their current distribution range, so interpretations of their biogeography based only on extant members can be misleading.     

Taxonomic significance of asymmetrical helmet and lance bristles in the genus Mallomonas (Synurophyceae) and their discovery in Eocene lake sediments

Complex bristle types formed by species in the genus Mallomonas include those with helmet or lance-shaped apices. The ornamentation on each side of the helmet has been thought to be equivalent or symmetrical, whereas on a lance-shaped bristle an expanded portion folds over one side of the shaft to form an asymmetrical structure. We describe, for the first time, helmet bristles with a distinctly asymmetrical design, also formed by the folding of a siliceous membrane over one side of the helmet. We postulate that the asymmetrical helmet represents a structure that combines the formation of a symmetrical helmet and a lance-shaped design on the same bristle. Further, we report structurally similar asymmetrical helmet bristles, lance-shaped bristles and scales that are unambiguously assigned to Mallomonas asmundiae in Middle Eocene sediments from a maar lake in northern Canada, supporting the hypothesis that scale and bristle morphology in the Synurophyceae has undergone extensive prolonged evolutionary stasis. Given differences in scale morphology and the presence of asymmetrical helmet bristles, we transfer the North American endemic Mallomonas acaroides var. muskokana to the rank of species. Further, we formally describe Mallomonas dispar and M. lancea, fossil species with asymmetrical helmet bristles and lance-shaped bristles, respectively. The taxonomic and biogeographic significance of asymmetrical and lance-bearing bristles is discussed.     

A new genus and species of an early Eocene primate from North Africa

A new Adapiform Primate from the locality of Chambi (Tunisia) is described and assigned toDjebelemur martinezi gen.nov., sp. nov. Holotype CBI 33, fragment of left mandible with P/3-M/3. Other material includes a lower and two upper isolated molars and one probable lower canine. This new material is assigned to the Adapidae.     

New Eocene dinoflagellate cysts from the southern edge of the Junggar Basin,Xinjiang, China

The Anjihaihe Formation in the southern edge of the Junggar Basin was previously considered a series of freshwater lacustrine depositions. However, abundant marine dinoflagellate cysts were recently recovered from the middle to upper part of the middle member of the formation. Two new genera, six new species and one new subspecies among the abundant dinoflagellate cysts are described and illustrated, i.e. Circulodinium? laeve sp. nov., Kaiwaradinium abbreviatum sp. nov., Spiniferites adnatus subsp. latispinus subsp. nov., Oligosphaeropsis accreta gen. et. sp. nov., Oligosphaeropsis complex gen. et. sp. nov., Oligosphaeropsis megaprocessa gen. et. sp. nov. and Tianshandinium biconicum gen. et. sp. nov. They are rare to common constituents of the dinoflagellate assemblage in the Anjihaihe Formation and may prove useful for regional biostratigraphic correlation and palaeoenvironment re-establishment.     

Studies in Neotropical paleobotany. XIV. A palynoflora from the Middle Eocene Saramaguacan Formation of Cuba

An assemblage of 46 fossil pollen and spore types is described from a core drilled through the middle Eocene Saramaguacán Formation, Camagüey Province, eastern Cuba. Many of the specimens represent unidentified or extinct taxa but several can be identified to family (Palmae, Bombacaceae, Gramineae, Moraceae, Myrtaceae) and some to genus (Pteris, Crudia, Lymingtonia?). The paleoclimate was warm-temperate to subtropical which is consistent with other floras in the region of comparable age and with the global paleotemperature curve. Older plate tectonic models show a variety of locations for proto-Cuba during Late Cretaceous and later times, including along the norther coast of South America. More recent models depict western and central Cuba as two separate parts until the Eocene, and eastern Cuba (joined to northern Hispaniola) docking to central Cuba also in the Eocene. All fragments are part of the North American Plate and none were directly connected with northern South America in late Mesozoic or Cenozoic time. The Saramaguacán flora supports this model because the assemblage is distinctly North American in affinities, with only one type (Retimonocolpites type 1) found elsewhere only in South America.     

Lunulichnus Tuberosus Ichnogen. and Ichnosp. Nov. from the Early Eocene Wasatch Formation,Fossil Butte National Monument,Wyoming: An Arthropod-Constructed Trace Fossil Associated with Alluvial Firmgrounds

A new trace fossil, Lunulichnus tuberosus, is described from fluvial deposits of the Wasatch Formation (early Eocene) at Fossil Butte National Monument, southwestern Wyoming, USA. L. tuberosus are straight, vertical to obliquely oriented, unlined cylindrical burrows with pronounced crescent-shaped wall sculptings. In situ examples of these trace fossils are most commonly preserved as sand-filled casts emanating from the erosional bases of fluvial channel sandstone bodies into underlying floodplain mudstone/siltstone beds. L. tuberosus is interpreted as the dwelling trace of a stream-dwelling decapod crustacean. Excellent preservation of fine detail, particularly their diagnostic crescent-shaped wall sculptings, support the hypothesis that L. tuberosus were excavated in firm substrata subjacent to fluvial erosional surfaces. As such, they are interpreted as constituents of alluvial Glossifungites trace fossil assemblages.     

Fossil penguin (Aves: Sphenisciformes) cranial material from the Eocene of Seymour Island (Antarctica)

Our knowledge of the cranial morphology of early penguins remains poor, particularly for Paleogene taxa. This paper describes a partial penguin skull and additional isolated cranial elements from the Eocene La Meseta Formation of Seymour Island, Antarctica. These specimens cannot be assigned to named taxa at present, but there is a strong possibility they belong to La Meseta penguins known only from postcranial elements. The skull shares extensive dorsal development of the temporal fossae with extant and fossil Spheniscus and the fossil penguins Paraptenodytes and Marplesornis, indicating the adductor complex was powerful in early penguins. Partial mandibles belonging to a much larger penguin are similar to Paraptenodytes and differ from all living penguins in the lack of a hooked medial process of the articular and the presence of a foramen anterior to the mandibular cotyles. Given the rarity of penguin cranial remains, these specimens provide important new insight into early penguin evolution.