Fossil Material Research Articles

Fossil insect-feeding traces indicate unrecognized evolutionary history and biodiversity on Australia's iconic Eucalyptus.

Fossilized plant-insect herbivore associations provide fundamental information about the assembly of terrestrial communities through geologic time. However, fossil evidence of associations originating in deep time and persisting to the modern day is scarce. We studied the insect herbivore damage found on 284 Eucalyptus frenguelliana leaves from the early Eocene Laguna del Hunco rainforest locality in Argentinean Patagonia and compared damage patterns with those observed on extant, rainforest-associated Eucalyptus species from Australasia (> 10 000 herbarium sheets reviewed). In the fossil material, we identified 28 insect herbivory damage types, including 12 types of external feeding, one of piercing-and-sucking, five of galls, and 10 of mines. All 28 damage types were observed in the herbarium specimens. The finding of all the fossil damage types on extant Eucalyptus specimens suggests long-standing associations between multiple insect herbivore lineages and their host genus spanning 52 million years across the Southern Hemisphere. This long-term persistence, probably enabled through niche conservatism in wet eucalypt forests, demonstrates the imprint of fossil history on the composition of extant insect herbivore assemblages. Although the identities of most insect culprits remain unknown, we provide a list of Eucalyptus species and specific population locations to facilitate their discovery, highlighting the relevance of fossils in discovering extant biodiversity.

The most detailed anatomical reconstruction of a Mesozoic coelacanth.

Although the split of coelacanths from other sarcopterygians is ancient, around 420 million years ago, the taxic diversity and the morphological disparity of the clade have remained relatively low, with a few exceptions. This supposedly slow evolutionary pace has earned the extant coelacanth Latimeria the nickname "living fossil". This status generated much interest in both extinct and extant coelacanths leading to the production of numerous anatomical studies. However, detailed descriptions of extinct taxa are made difficult due to the quality of the fossil material which generally prevents fine comparisons with the extant Latimeria. Here we describe a new genus and species of coelacanth, Graulia branchiodonta gen. et sp. nov. from the Middle Triassic of Eastern France, based on microtomographical imaging using synchrotron radiation. Through exquisite 3D preservation of the specimens, we reconstructed the skeletal anatomy of this new species at an unprecedented level of detail for an extinct coelacanth, and barely achieved for the extant Latimeria. In particular, we identified a well-developed trilobed ossified lung whose function is still uncertain. The skeletal anatomy of G. branchiodonta displays the general Bauplan of Mesozoic coelacanths and a phylogenetic analysis resolved it as a basal Mawsoniidae, shedding light on the early diversification of one of the two major lineages of Mesozoic coelacanths. However, despite its exquisite preservation, G. branchiodonta carries a weak phylogenetic signal, highlighting that the sudden radiation of coelacanths in the Early and Middle Triassic makes it currently difficult to detect synapomorphies and resolve phylogenetic interrelationships among coelacanths in the aftermath of the great Permo-Triassic biodiversity crisis.

New material of the small raoellid artiodactyl Metkatius kashmiriensis Kumar and Sahni, 1985 (Mammalia) from the middle Eocene of the Kalakot area, Rajouri District, Jammu and Kashmir, India

New material of the small raoellid artiodactyl Metkatius kashmiriensis is reported from the middle Eocene of the Upper Subathu Formation in the Kalakot area, Jammu and Kashmir, northwest Himalaya, India. The fossil material consists of numerous mandibular and maxillary fragments and isolated teeth, mainly belonging to juvenile specimens. It documents the poorly known dental morphology of M. kashmiriensis and provides an overview of its intraspecific variation, allowing to redefine its diagnosis. M. kashmiriensis is characterized by a particularly small size compared with other raoellid species, and by bunodont molars with moderately marked transverse lophs. The M/1-2 are much longer than wide and display characters similar to those of Rajouria gunnelli, such as the presence of a small paraconid and a mesial mesiostylid. The P/4 bears distally a small hypoconid, which appears to be unique in Raoellidae. The description of the new material also allows to document the poorly known morphology of the deciduous teeth of raoellids. The DP2/ is reported for the first time, and the DP/4 of M. kashmiriensis shows a morphology different from that of Indohyus, with the absence of mesial basin anterior to the paraconid and the primoconid. Contrary to what has recently been proposed, these results confirm that M. kashmiriensis is a valid species and not a synonym of Indohyus indirae, and highlight the great morphological diversity present within the Raoellidae during the middle Eocene in the Indian subcontinent.

Natural fiber reinforced cementitious composites; materials, compatibility issues and future perspectives

ABSTRACT Research on the sustainable production of building materials has been increasing from time to time. The construction industry is one of the sectors that leads to the depletion of significant amounts of nonrenewable resources, such as minerals. The ecosystem is deteriorated, and carbon dioxide (CO2) emissions are enormous in the environment due to the use of fossil fuel-based materials. The purpose of this paper is to review the use of plant fibers (hereafter NF) for reinforcement in cementitious concrete. Concrete, plant fibers, their chemical nature, and characteristics are highlighted in an overview. The most important issues in NF-concrete compatibility were discussed, which could provide research opportunities. Modification of NFs and the cement matrix are examined as methods for improving compatibility and degradation. Moreover, the properties and longevity of cementitious materials that are reinforced with natural fibers are also examined. Finally, the review emphasizes the significant research gaps and future research prospects identified in the reviewed papers.

Calophyllum L.: An important tropical element in the monsoon-influenced ancient Siwalik Forest of eastern Himalaya

Calophyllum vegetative (leaves and woods) fossil remains have been widely reported from the Cenozoic sedimentary strata across the Northern and Southern Hemispheres. However, until now, no reproductive megafossil remains have been discovered. Here, we report and describe Calophyllum fossil fruits from the Siwalik (middle Miocene–Pliocene) sediments of Darjeeling foothills, eastern Himalaya for the first time. In addition, we also provide fossil materials of isolated leaves in appreciable numbers recovered from the same stratigraphic level. Our Siwalik fossils and extant members of Calophyllum are closely related morphologically by stalked, ball-shaped (spherical to ovoid) drupe with a thin, dark brown, smooth surfaced outer layer and a hard endocarp; and symmetrical, oblong-elliptic shaped entire margined lamina with numerous close parallel secondary veins, and obscure tertiary veins. Based upon morphology and epidermal anatomy, the fossil fruits are recognized as a new fossil-species Calophyllum ramthiene sp. nov. The present Calophyllum leaf and fruit fossils, along with previous reports suggest that Calophyllum was an important forest element throughout the eastern Himalaya during the period of Siwalik sedimentation (Mio-Pleistocene time). We briefly discuss the fossil history of Calophyllum and palaeobiogeography in India and palaeoclimatic implications regarding the distribution and habitat of fossil and modern members of Calophyllum.

A Review of Natural Fibres and Biopolymer Composites: Progress, Limitations, and Enhancement Strategies.

The interest in natural fibres and biopolymers for developing bio-composites has greatly increased in recent years, motivated by the need to reduce the environmental impact of traditional synthetic, fossil fuel-derived materials. However, several limitations associated with the use of natural fibres and polymers should be addressed if they are to be seriously considered mainstream fibre reinforcements. These include poor compatibility of natural fibres with polymer matrices, variability, high moisture absorption, and flammability. Various surface treatments have been studied to tackle these drawbacks, such as alkalisation, silane treatment, acetylation, plasma treatment, and polydopamine coating. This review paper considers the classification, properties, and limitations of natural fibres and biopolymers in the context of bio-composite materials. An overview of recent advancements and enhancement strategies to overcome such limitations will also be discussed, with a focus on mechanical performance, moisture absorption behaviour, and flammability of composites. The limitations of natural fibres, biopolymers, and their bio-composites should be carefully addressed to enable the widespread use of bio-composites in various applications, including electronics, automotive, and construction.

Thermal-induced crystallographic transformation in shells of Mytilus galloprovincialis Lamarck, 1819

Biominerals in hard parts are widely used as paleoenvironmental archives, employing proxies such as elemental and isotopic composition, microstructure, and crystallography. However, the effective selection and application of these proxies in fossil materials depends on their preservational potential. Here we evaluated the preservational potential of these proxies through controlled experiments on bivalves, one of the commonly used fossils in paleoenvironmental reconstructions. We utilized cultured Mytilus galloprovincialis specimens at five controlled temperatures to investigate the impact of elevated temperatures on various proxies extracted from both aragonitic and calcitic components of the same shell, including isotopic composition, microstructure and crystallography. Elevated temperatures first induced changes in the oxygen isotope composition (in both aragonite and calcite), followed by modification in aragonitic parts, such as changes in the aragonite phase, textures, nacre microstructure, and grain size of aragonite crystals. Despite aragonite's susceptibility to temperature, the microstructure and texture of calcite remained largely unaltered, demonstrating significantly higher resilience. Our findings emphasize the preservational potential of different shell proxies under heat exposure, ranging from oxygen isotopes to microstructure and texture. A ranking of preservation potential provides a practical guide for selecting well-preserved specimens, as textures and microstructures are not always reliable indicators. In distinguishing aragonite from calcite in fossils, our study pioneers a new avenue by proposing the analysis of high-angle boundary (HAB) content, including twin boundaries, as a reference for altered aragonite.

Reply to Head's comment on “The Volyn biota (Ukraine) – indications of 1.5 Gyr old eukaryotes in 3D preservation, a spotlight on the `boring billion' ” by Franz et al. (2023)

Abstract. Head et al. (2024) emphasize the importance of the Volyn biota for evolution, especially in the so-called “boring billion”, in a detailed outline about the biological and geological context. However, they question the idea that the Volyn biota represent Precambrian fossils and instead argue that they contain young contaminants of “museum dust”. In addition, they question their biotic origin. We present here a detailed discussion of their points of concern based on presented data, including some additional information. Their points of concern were as follows: One object, shown by Franz et al. (2023a), is similar to a pollen grain, and another object is similar to trichomes; we show indications of fossilization and summarize our arguments against “museum dust”. They question the fossil character of the biota and argue for a biomineralization; we show that the biomineralization in trichomes is distinct from the mineralization of the biota. They missed information about the internal structure; we repeat the presented information about the internal structure in more detail, which is also indicative of fossil material and inconsistent with trichomes. They argue that we did not compare the biota with recent fungi via infrared spectroscopy; since the biota experienced temperatures near 300 °C, we think that a comparison with thermally degraded chitosan is more appropriate. They question the use of strongly negative δ13C as an argument for biotic origin, but we show that, in combination with positive δ15N values and the geological situation, a biotic origin is more likely than abiotic synthesis. In addition, Popov (2023) questioned the age of the Volyn biota, which we postulated as between approximately 1.5 and 1.7 Ga. He argues that the fossils could be Phanerozoic. We will also outline our arguments for the minimum age of 1.5 Ga.

The postcranial skeleton of Amphimoschus Bourgeois, 1873 (Cetartiodactyla, Ruminantia, Pecora) sheds light on its phylogeny and the evolution of the clade Cervoidea

Here we present the first description of the postcranial skeleton of Amphimoschus, an enigmatic hornless ruminant known from the late Early to the late Middle Miocene of Eurasia (c. 17.5–13.8 Ma). This new fossil material that includes several elements of the appendicular skeleton comes from the French sites of Pontlevoy (MN5), Aérotrain (MN4), and Artenay (MN4). The postcranial skeleton of Amphimoschus is relevant to determine its phylogenetic affinities within the Pecora and to better understand the evolution of cervoids, the pecoran ruminants more closely related to deer. Our total-evidence tip-dating phylogenetic analysis recovers three well-supported main lineages of crown pecorans (Giraffomorpha, Bovidomorpha and Cervidomorpha) and places Amphimoschus as a basal member of a monophyletic Cervoidea. Thus, we reject the recent assignment of Amphimoschus to the Bovoidea, and confirm the presence of hornless forms at the base of the cervoid clade. We define the Cervoidea as the least inclusive clade of crown pecorans including Amphimoschus and the Cervidae. We also define the Cervidomorpha as the least inclusive clade of crown pecorans containing Namibiomeryx and the Cervidae. Cervidomorphs were relatively successful in the Miocene, spreading through Africa, Eurasia and North America during the Early–Middle Miocene. Amphimoschus xishuiensis Y.-K. Li et al., 2021 is recovered here as the closest sister group to the Bovidae and hence cannot be considered to belong to the genus Amphimoschus. We erect for it the new genus Dimidiomeryx. Our topology adds complexity to the recently revamped hypothesis based on molecular data regarding the single origin of the cranial appendages in pecoran ruminants. Amphimoschus probably had a sitatunga-like lifestyle, sporting sprawling-out fingers with very long third phalanges, long limbs and a general configuration of the appendicular skeleton that probably allowed it to live in swampy/semiaquatic environments.

Accelerating segmentation of fossil CT scans through Deep Learning

Recent developments in Deep Learning have opened the possibility for automated segmentation of large and highly detailed CT scan datasets of fossil material. However, previous methodologies have required large amounts of training data to reliably extract complex skeletal structures. Here we present a method for automated Deep Learning segmentation to obtain high-fidelity 3D models of fossils digitally extracted from the surrounding rock, training the model with less than 1%-2% of the total CT dataset. This workflow has the capacity to revolutionise the use of Deep Learning to significantly reduce the processing time of such data and boost the availability of segmented CT-scanned fossil material for future research outputs. Our final Unet segmentation model achieved a validation Dice similarity of 0.96.

Oxygen isotope studies of the largest West Siberian mammoth sites and implications for last glacial maximum climate reconstruction

This study examines the isotopic potential of mammoth remains from three paleontological sites in the southeast of the West Siberian Plain (SEWS): Shestakovo, Krasnoyarskaya Kurya, and Volchia Griva. We analysed oxygen isotopes from 29 mammoth enamel and tusk samples and horse and deer enamel samples. We verified sample preservation using ATR-FTIR and obtained δ18Op, δ18Oc, and reconstructed δ18Ow values for 28-22 ka cal BP. Preservation assessments revealed variable preservation conditions. Our findings indicate an increase of 1.4‰ in reconstructed δ18Ow values from glacial levels at 28-23 ka to late-glacial conditions at ca. 17–15.5 ka, likely reflecting climatic warming at the end of the Pleistocene. The extensive fossil material at these sites offers significant potential for further Last Glacial Maximum studies.

Revisions, new taxa, and venation transformations of the sawfly family Blasticotomidae sensu lato (Hymenoptera: Tenthredinoidea) highlight the evolution of the basal Hymenoptera

Abstract Wing venation pattern is particularly important in the taxonomy and classification of insects, especially for fossil material. There are recognized transformation series that apparently often represent a mainstream in the evolutionary trend of the wing venation of Hymenoptera. One notable instance is the gradual reduction of the subcosta veins from multiple branches to their total absence. Herein, we place four new genera and six new species in the family Blasticotomidae (=Xyelotomidae) of Hymenoptera. They are Xyelocerus abruptus sp. nov., Liberitoma tenella gen et sp. nov., Liberitoma compta sp. nov., Liberitoma incompleta sp. nov., Aduantoma insolita gen. et sp. nov., and Apertoma gen. nov. from the Middle Jurassic of China, and Enspeletoma oligocaenica gen. et sp. nov. from the Upper Oligocene of Germany. The newly discovered species of Liberitoma from China possessed a supernumerary hind branch of vein Sc in its forewing, which has apparently never been recorded before in other hymenopterans, and the unique venation pattern of Aduantoma suggests the possibility of two additional steps of vein Sc transformation before its complete loss. Based on the new findings, Blasticotomidae are proposed to be divided into four subfamilies: Blasticotominae Thomson 1871, Dahurotominae subfam. nov., Pseudoxyelocerinae subfam. nov., and Undatominae subfam. nov.

Physical and numerical simulation of heat and mass transfer in the furnace of a thermogravimetric analyzer

A numerical study of the processes of heat and mass transfer in the furnace of a thermogravimetric analyzer was carried out, aimed at improving the accuracy of determining the kinetic characteristics of samples during their thermal transformations in different media. Validation of the model and prognostic estimates were carried out in relation to specially conducted thermogravimetric studies of the conversion of fossil and renewable carbon-containing raw materials in successive processes of decarbonization (combustion) and carbonation (mineralization of ash residue). The application of the study results allows to calculate the actual concentrations of the reagent over the sample uncontrolled by the device during pulsed switching of media and the actual temperatures of the sample during its thermochemical transformations.

Sphagnum moss and peat comparative study: Metal release, binding properties and antioxidant activity.

Peat is the main constituent of cultivation substrates and a precious non-renewable fossil material. Peatlands provide important ecosystem services and allow the absorption and storage of carbon. Protecting peatlands helps tackle climate change and contributes to biodiversity conservation. Due to its importance, it is necessary to implement strategies to reduce the use of peat, such as replacing it with biomass-based alternative growing media constituents, such as Sphagnum moss. In this study, we compared the metal release and binding properties at two different pH, antioxidant activity, and total phenolic content of peat and Sphagnum moss from the Tierra del Fuego (TdF) region of southern Patagonia. Levels of the elements were determined by inductively coupled plasma mass spectrometry (ICP-MS), while the types and amounts of functional groups were characterized and compared using Fourier transform infrared (FTIR) spectroscopy. The total phenol level and antioxidant capacity were assessed using the Folin-Ciocalteu method and 2,2-diphenyl-1-picrylhydrazyl test. There are generally higher concentrations of leachable elements in peat than in Sphagnum moss at pH = 2, except Cs, Rb, Ti, and Zr. In contrast, at pH = 5, levels of all leached elements are highest in Sphagnum moss. Sphagnum moss shows a higher metal adsorption capacity than peat, except for Be, Mn, Tl, and Zn. Finally, the results showed that both matrices contained similar total phenolic contents: 0.018 ± 0.011 mg gallic acid equivalent (GAE) per gram dry sample for peat and 0.020 ± 0.007 mg GAE g-1 for Sphagnum moss. Instead, Sphagnum moss extracts showed a significantly higher antioxidant activity [0.026 ± 0.028 mmol Trolox equivalents (TE) g-1] than that estimated in peat (0.009 ± 0.005 mmol TE g-1). Humic acids, carboxylic acids, and phenolic and lignin groups were identified as the functional groups that mainly determined the antioxidant activity of the Sphagnum moss compared to peat. The present study resulted in an advancement of knowledge of these materials for more thoughtful future use and possible replacements.

Using the methyl cellulose poultice method to remove plaster and burlap - A case study on Triceratops bone

The dinosaur collection at the Natural History Museum, London (NHM) includes a Triceratops skull (NHMUK PV R 3886), purchased from Charles Sternberg in 1909. While most of the skull is on public display in the Dinosaurs gallery, two large sections of the frill (the squamosal bones) had been replicated for the display and the originals left in storage. With much of the fossil bone obscured by plaster of Paris, the original frill sections were deemed of limited use to science in their current form. A work request was received to strip away as much artificial material as possible to determine the extent of the original fossil material. An air scribe fitted with a chisel stylus proved initially effective, but soon revealed an additional obstacle – layers of hessian underneath. The methyl cellulose poultice method was used to swell the hessian, aiding softening of the plaster, and allowing layers to be torn off in strips. The fine layer of plaster remaining on the bone was removed, where possible, with a Split-V ultrasonic tool. This sequence of treatments can be utilised at minimal risk to specimens in similar situations when a hessian and plaster jacket has been applied but a separator layer has been omitted.

Unraveling sauropod diversity in the Portezuelo Formation of Patagonia through a comprehensive analysis of new and existing material

The Portezuelo Formation preserves an outstanding record of the upper Turonian – lower Coniacian. Despite the discovery of a significant quantity of sauropod fossil material from the formation, only two species have been formally described to date: Malarguesaurus florenciae and Futalognkosaurus dukei. Here we present new sauropod material mostly composed of non-articulated caudal vertebrae (MCF-PVPH 916 and 917) that belong to two titanosauriforms on the basis of the following features: anterior caudal vertebrae with procoelous-opisthoplatyan articulations, transverse processes that reach the posterior articular face of the centrum and neural spines with a transverse width of around 50% of their anteroposterior length; anterior and middle caudal vertebrae with the neural arch restricted to the anterior half of the centrum; middle caudal centra with circular cross-section. Phylogenetic analysis recovers the new material in close relation to Malarguesaurus within a monophyletic clade at the base of Somphospondyli. This clade shares large pedicel height with a vertical anterior border on the middle caudal vertebrae, a vertical orientation of the neural spines on the distalmost middle caudal vertebrae and proximalmost posterior caudal vertebrae, and subequal relative lengths of the proximal ulnar condylar processes. The specimens presented here are distinct not only from Futalognkosaurus, but also from other indeterminate titanosaurian remains from the same formation. However, there are no significant differences between the specimen MCF-PVPH 917 and Malarguesaurus, but there are differences between the posterior caudal vertebrae of MCF-PVPH 916 and Malarguesaurus, so they could be considered different species. Whilst we err on the side of caution in not naming new taxa here, the two specimens significantly expand what we know about sauropods in the Turonian–Coniacian ecosystems of Patagonia, which will continue to do so as more material is discovered.

Compound osteoderms preserved in amber reveal the oldest known skink

Scincidae is one of the most species-rich and cosmopolitan clades of squamate reptiles. Abundant disarticulated fossil material has also been attributed to this group, however, no complete pre-Cenozoic crown-scincid specimens have been found. A specimen in Burmite (99 MYA) is the first fossil that can be unambiguously referred to this clade. Our analyses place it as nested within extant skinks, supported by the presence of compound osteoderms formed by articulated small ostedermites. The specimen has a combination of dorsal and ventral compound osteoderms and overlapping cycloid scales that is limited to skinks. We propose that this type of osteoderm evolved as a response to an increased overlap of scales, and to reduced stiffness of the dermal armour. Compound osteoderms could be a key innovation that facilitated diversification in this megadiverse family.

O rozwoju naturalnie niezrównoważonym i równoważonym sztucznie

The author presents the hypothesis that in the absence of human interference, i.e. in natural conditions, development takes place spontaneously and is basically unsustainable, and it becomes sustainable only due to anthropogenic factors, i.e. artificially. Sustainable development takes place primarily in the sociosphere. People began to balance development only when they realized that rapid economic development was reaching a critical moment because of the rapid exhaustion of fossil and non-fossil raw material resources and unlimited overconsumption. This was initially ignored. It took several decades before it was taken seriously. Then the idea of controlled, or sustainable, development appeared. Since then, actions have been taken to reduce various categories of imbalances in an increasing number of areas of activity. Since then, the idea of sustainable development has become fashionable, important and lucrative, although utopian, because sustainable development is seen as a panacea for crises, inequalities and social contradictions. The publications of Donella Meadows (Limits to growth. A Report for the Club of Rome's Project on the Predicament of Mankind), of Ernst U. v. Weizäcker (Wir sind dran. Was wir ändern müssen, wenn wir bleiben wollen), and of Gaya Herrington, (Five Insights for Avoiding Global Collapse) contributed significantly to the implementation of this idea. They indicate that appropriate actions taken by 2040 will determine the future fate of humanity. To prove the validity of his hypothesis, the author used some publications on 17 general goals and 169 tasks.

New data and redescription of Kellnerius jamacaruensis Santana et al., 2013, a Palaemonidae shrimp from the Araripe Basin in northeastern Brazil

The preservation of shrimp in the fossil record is difficult due to their rapid decomposition. In this study, we provide new taxonomic insights into Kellnerius jamacaruensis from the Lower Cretaceous Romualdo Formation in the Araripe Basin, northeastern Brazil. A comprehensive taxonomic review, including a more meticulous preparation of the holotype and additional fossil material, enabled the disclosure of previously unknown anatomical features, reaffirming its classification within the family Palaemonidae.

A quantitative test of the "Ecomorphotype Hypothesis" for fossil true seals (Family Phocidae).

The fossil record of true seals (Family Phocidae) is mostly made up of isolated bones, some of which are type specimens. Previous studies have sought to increase referral of non-overlapping and unrelated fossils to these taxa using the 'Ecomorphotype Hypothesis', which stipulates that certain differences in morphology between taxa represent adaptations to differing ecology. On this basis, bulk fossil material could be lumped to a specific ecomorphotype, and then referred to species in that ecomorphotype, even if they are different bones. This qualitative and subjective method has been used often to expand the taxonomy of fossil phocids, but has never been quantitatively tested. We test the proposed ecomorphotypes using morphometric analysis of fossil and extant northern true seal limb bones, specifically principal components analysis and discriminant function analysis. A large amount of morphological overlap between ecomorphotypes, and poor discrimination between them, suggests that the 'Ecomorphotype Hypothesis' is not a valid approach. Further, the analysis failed to assign fossils to ecomorphotypes designated in previous studies, with some fossils from the same taxa being designated as different ecomorphotypes. The failure of this approach suggests that all fossils referred using this method should be considered to have unknown taxonomic status. In light of this, and previous findings that phocid limb bones have limited utility as type specimens, we revise the status of named fossil phocid species. We conclude that the majority of named fossil phocid taxa should be considered nomina dubia.