Fossil Record Research Articles

Re-investigation of the Mesozoic cycad genus Chilinia: fossil record, diversity, spatio-temporal distribution, and palaeoclimate implications

Chilinia is an extinct genus of cycads, established by Li and Ye in 1964 based on leaf fossils from the Lower Cretaceous in Jilin Province, China. Morphologically, the genus Chilinia closely resembles Ctenis, another cycad foliage genus, in having pinnately divided leaves with laterally inserted pinnae on the rachis and reticulate venation but differs mainly from the latter in having toothed or irregularly lobed rather than entire-margined pinnae. Fossil records show that up to now, nine species of Chilinia have been reported worldwide, representing an index fossil plant in the Jurassic to Early Cretaceous. In this study, we present a comprehensive overview of all reported Chilinia fossils from a systematic palaeobotanical perspective. Fossil records indicate that Chilinia mainly occurred in the middle–high latitudes of the northern and southern hemispheres in Pangea from the Middle Jurassic to mid-Cretaceous. Combined evidence from the morphology of Chilinia and its floral patterns suggests that the genus probably lived in humid warm-temperate palaeoclimatic conditions with brief seasonal variations.

Of sea, rivers and symbiosis: Diversity, systematics, biogeography and evolution of the deeply diverging florideophycean order Hildenbrandiales (Rhodophyta)

The Hildenbrandiales, a typically saxicolous red algal order, is an early diverging florideophycean group with global significance in marine and freshwater ecosystems across diverse temperature zones. To comprehensively elucidate the diversity, phylogeny, biogeography, and evolution of this order, we conducted a thorough re-examination employing molecular data derived from nearly 700 specimens. Employing a species delimitation method, we identified Evolutionary Species Units (ESUs) within the Hildenbrandiales aiming to enhance our understanding of species diversity and generate the first time-calibrated tree and ancestral area reconstruction for this order. Mitochondrial cox1 and chloroplast rbcL markers were used to infer species boundaries, and subsequent phylogenetic reconstructions involved concatenated sequences of cox1, rbcL, and 18S rDNA. Time calibration of the resulting phylogenetic tree used a fossil record from a Triassic purportedly freshwater Hildenbrandia species and three secondary time points from the literature. Our species delimitation analysis revealed an astounding 97 distinct ESUs, quintupling the known diversity within this order. Our time-calibration analysis placed the origin of Hildenbrandiales (crown age) in the Ediacaran period, with freshwater species emerging as a monophyletic group during the later Permian to early Triassic. Phylogenetic reconstructions identified seven major clades, experiencing early diversification during the Silurian to Carboniferous period. Two major evolutionary events—colonization of freshwater habitats and obligate systemic symbiosis with a marine fungus—marked this order, leading to significant morphological alterations without a commensurate increase in species diversification. Despite the remarkable newly discovered diversity, the extant taxon diversity appears relatively constrained when viewed against an evolutionary timeline spanning over 800 million years. This limitation may stem from restricted geographic sampling or the prevalence of asexual reproduction. However, species richness estimation and rarefaction analyses suggest a substantially larger diversity yet to be uncovered—potentially four times greater. These findings drastically reshape our understanding of the deeply diverging florideophycean order Hildenbrandiales species diversity, and contribute valuable insights into this order evolutionary history and ecological adaptations. Supported by phylogenetic, ecological and morphological evidence, we established the genus Riverina gen. nov. to accommodate freshwater species of Hildenbrandiales, which form a monophyletic clade in our analyses. This marks the first step toward refining the taxonomy of the Hildenbrandiales order, a task demanding thorough revisions, notably the creation of several genera to address the polyphyletic status of Hildenbrandia. However, the limited diagnostic features pose a challenge, necessitating a fresh approach to defining genera. A potential solution lies in embracing a molecular systematic perspective, which can offer precise delineations of taxonomic boundaries.

Elateriform beetle larvae preserved in about 100-million-year-old Kachin amber

AbstractBeetle larvae show high diversity in forms and ecological roles. Beetle larvae are often roughly categorised into certain larval types, for example: campodeiform, onisciform, scarabeiform, or elateriform. Larvae of the latter type are virtually absent from the fossil record. Here, we report three amber pieces from Cretaceous Kachin amber, Myanmar (about 100 million years old) that together include nine elateriform beetle larvae. One of the amber pieces has a single specimen included. The specimen is interpreted as a larva of Elateridae, the group of click beetles, possibly of the ingroup Elaterinae; yet accessible details are limited. Eight specimens within the other two amber pieces show certain similarities with larvae of Elateridae, but show significant differences in the trunk end, which bears two lobes armed with hooks in these fossils. This very specific structure is well known in modern larvae of Ptilodactylidae (toed-winged beetles). Therefore, the fossils are interpreted as larvae of Ptilodactylidae. Both types of here reported elateriform larvae represent the first fossil record of larvae of their respective groups. It is well known that larval morphology does not evolve in concert with adult morphology, and a modern-type morphology of the one may precede that of the other. Hence, the new fossils are important indicators of the appearance of the modern larval morphologies of their respective lineages. We also briefly discuss the fossil record of larvae of Elateriformia (of which Elateridae and Ptilodactylidae are ingroups) in general.

An inclusion of Melastomataceae leaf from the Miocene amber of Simojovel de Allende, Chiapas, México

Melastomataceae Jussis a family well represented in tropical biomes and is characterized by a distinctive venation pattern in its leaves. The worldwide fossil record consists mainly of leaves that date back to the Palaeocene. However, this family is poorly represented in the fossil record in Mexico. Here, we show a new finding of a Melastomataceae leaf preserved as inclusion in amber outcrops in Chiapas that preserves evidence of the complex Miocene ecosystem through well-preserved fossil organisms. The morphological characteristics described were based on shape and venation patterns and compared with extant or fossil organisms with similar patterns, allowing us to assign individuals to one of the species hypotheses or name them as a new species. The fossil leaf has ovate to elliptical lamina, nanophyll size, long petiole, and basal acrodromous venation, with one pair of secondaries emerging from the petiole and merging at the leaf apex and opposite percurrent epimedial tertiary veins. This combination of characteristics are typical of Miconia Ruiz & Pavón and have not been observed together in any leaf recordings for this family, proposing a new fossil species. This discovery confirms the presence of Melastomataceae in Southern Mexico during the Miocene, which was once part of the tropical rainforest of the Simojovel Formation of Chiapas, Mexico.

Come rain or come shine, the species richness will decline in the Moroccan mountains

Plant species richness in mountainous regions generally follows a unimodal distribution with lower values at both low and high altitudes in relation to precipitation. In the Atlas mountains, Morocco, plant species richness is currently highest at 800-1200m elevation, but the extent and altitudinal limits of this species-rich belt have shifted in the past with climate change.Here, we trace the evolution of pollen taxonomic richness (PTR) as a proxy for plant species richness, with the aim of understanding the relationship with climatic changes over the past 19,000 years, and make some assumptions about future changes in species richness. Past PTR was inferred through an analogy with an extensive modern pollen dataset, and past climatic variables were reconstructed from a fossil record collected in the Middle Atlas, Morocco.We found that the current PTR distribution in Morocco is more closely associated with precipitation than with temperature. During the last glacial period, both PTR and annual precipitation were low, and the analogs were located at lower altitudes than the altitude of the fossil record. During the early Holocene, the PTR increased by approximately 15%, and the modern analogs were found approximately 600 to 800 meters higher than the analogs of the last glacial period. After 6,000 years BP, we observe a steady decline in annual precipitation of approximately 30%, resulting in a species richness loss of approximately 18% and a retreat of the upper boundary of the species-rich belt.Climate projections suggest that annual precipitation in Northwest Africa will decrease by 20-30% over the next 50 years, an annual amount comparable to that of the last glacial period, but under much warmer conditions and in a significantly shorter time. Such a decline in precipitation could result in an unprecedented loss of plant species richness of approximately 15% in just a few decades and put 35% of the protected areas at risk. The forested mountains above 1600 meters could then resemble the treeless and less diverse steppes found at higher altitudes above today's tree line.

High-resolution UAV maps of the Gobi Desert provide new insights into the Upper Cretaceous of Mongolia

The Gobi Desert of southern Mongolia is home to an incredibly rich record of dinosaurs and other vertebrate fossils from the latest Cretaceous Period. Together, more than a dozen sites in several basins have produced one of the richest palaeofaunas known from this interval anywhere in the world. Most of this diversity has been recovered from the fluvial deposits of the Nemegt Formation. Despite historic and ongoing research in southern Mongolia, accurate maps and geological data for the main fossil sites are still lacking, limiting our ability to investigate how local palaeoecological dynamics influenced Nemegt taxa, their geographic distribution, and their evolutionary patterns. One of these sites, Guriliin Tsav, has produced more than a hundred significant fossil specimens to date, but still remains one of the lesser known Nemegt localities. In part this is because many expeditions have instead focused on the nearby Bügiin Tsav, one of the largest and richest localities for the Nemegt Formation. To address this gap, a project was initiated in 2018 to produce a high-resolution topographic map of Guriliin Tsav using Unmanned Aerial Vehicles (UAV), and consequently, to plot the geographic and stratigraphic distributions of palaeontological resources on this map. In so doing, we also collected stratigraphic and taphonomic data from the area, allowing for the first detailed palaeoecological interpretation of Guriliin Tsav and a comparison with other localities of southern Mongolia. Here we present the results of this project, and also discuss new topographic and stratigraphic data from Bügiin Tsav. This sheds new light into the temporal and geographic distribution of vertebrate taxa in the latest Cretaceous of Mongolia.

New records of early Paleocene (earliest Torrejonian) plesiadapiforms from northeastern Montana, USA, provide a window into the diversification of stem primates

Plesiadapiforms (putative stem primates) appear in the fossil record shortly after the Cretaceous/Paleogene boundary and subsequently radiated throughout the Paleocene into a taxonomically and ecomorphologically diverse group. The oldest known plesiadapiforms come from early Puercan (the oldest North American Land Mammal ‘age’ [NALMA] of the Cenozoic) deposits in northeastern Montana, and all records of Puercan plesiadapiforms are taxonomically restricted to members of the Purgatoriidae and the enigmatic genus Pandemonium. Plesiadapiform diversity substantially increased in the following Torrejonian NALMA, but the sparse record of faunas between the Puercan and the well-known middle and late Torrejonian has hampered our understanding of this important interval in early primate evolution. Here we report new plesiadapiform dental fossils from early Torrejonian (To1) deposits from the Tullock Member of the Fort Union Formation in northeastern Montana that record several poorly known taxa including members of the Purgatoriidae, Paromomyidae and Pandemonium, and that document the largest and most diverse assemblage of To1 plesiadapiforms known. We describe a new species of the purgatoriid Ursolestes (Ursolestes blissorum, sp. nov.) that represents the largest plesiadapiform known from the early Paleocene and, among other taxa, provides additional evidence that the temporal range of purgatoriids extended into the Torrejonian. Large sample sizes of the oldest known paromomyid, Paromomys farrandi, allowed us to document intraspecific variability and one undescribed tooth locus. Our observations illuminate changes in dental morphology of some taxa that occurred in To1 and may inform the acquisition of certain diagnostic plesiadapiform dental characters. We evaluate plesiadapiform species richness, mean body mass and body-mass disparity through the Paleocene and reveal unrecognized levels of richness in To1 and a general trend of stable body mass and body-mass disparity. Our findings contribute to documented patterns of plesiadapiform provincialism in the early Paleocene and shed light on the early stages of their Torrejonian radiation.

Earliest megafossils of scandent calamoid palms from the Deccan Intertrappean Beds of Central India and their paleobiogeographic implications

Two well-preserved petrified palm stems from the latest Maastrichtian (Late Cretaceous) to earliest Danian (Early Paleocene) sediments of the Deccan Intertrappean Beds of Madhya Pradesh, Central India are described. Their significant anatomical characteristics include a Calamus-type general stem pattern, the presence of well-preserved fibrovascular bundles (fvbs) with two wide metaxylem vessel elements (230 μm–250 μm) and one phloem strand, uniform density of fvbs, lack of continuity between protoxylem and metaxylem vessel elements, and an absence of centrifugal differentiation of sclerenchymatous fibrous parts. These features reveal a close resemblance to those of extant genera of scandent Calamoideae. The permineralized stems are described as a new species namely, Palmoxylon calamoides Kumar, Roy et Khan sp. nov. The fossils represent the oldest reliable fossil records of this family, supporting their Gondwanan origin, their importance in tracing their migration pathways from India to Europe and other continents after the docking of the Indian subcontinent with Eurasia during the Paleocene, and an “Out-of-India” dispersal hypothesis. Today the subfamily Calamoideae is disjunctly occurred in Africa, Asia, Australia, Europe, and South America, but the poor deep-time fossil record of this subfamily with a small number of Cenozoic fossils makes hypotheses concerning its origin and dispersal difficult to evaluate. The present study has significant implications for the origin and migration of this subfamily and the paleoclimate.

The "elongate chelicera problem": A virtual approach in an extinct pterygotid sea scorpion from a 3D kinematic point of view.

Chelicerae, distinctive feeding appendages in chelicerates, such as spiders, scorpions, or horseshoe crabs, can be classified based on their orientation relative to the body axis simplified as either orthognathous (parallel) or labidognathous (inclined), exhibiting considerable diversity across various taxa. Among extinct chelicerates, sea scorpions belonging to the Pterygotidae represent the only chelicerates possessing markedly elongated chelicerae relative to body length. Despite various hypotheses regarding the potential ecological functions and feeding movements of these structures, no comprehensive 3D kinematic investigation has been conducted yet to test these ideas. In this study, we generated a comprehensive 3D model of the pterygotid Acutiramus, making the elongated right chelicera movable by equipping it with virtual joint axes for conducting Range of Motion analyses. Due to the absence in the fossil record of a clear indication of the chelicerae orientation and their potential lateral or ventral movements (vertical or horizontal insertion of joint axis 1), we explored the Range of Motion analyses under four distinct kinematic settings with two orientation modes (euthygnathous, klinogathous) analogous to the terminology of the terrestrial relatives. The most plausible kinematic setting involved euthygnathous chelicerae being folded ventrally over a horizontal joint axis. This configuration positioned the chelicera closest to the oral opening. Concerning the maximum excursion angle, our analysis revealed that the chela could open up to 70°, while it could be retracted against the basal element to a maximum of 145°. The maximum excursion in the proximal joint varied between 55° and 120° based on the insertion and orientation. Our findings underscore the utility of applying 3D kinematics to fossilized arthropods for addressing inquiries on functional ecology such as prey capture and handling, enabling insights into their possible behavioral patterns. Pterygotidae likely captured and processed their prey using the chelicerae, subsequently transporting it to the oral opening with the assistance of other prosomal appendages.

Inferring the evolution of reproductive isolation in a lineage of fossil threespine stickleback, Gasterosteus doryssus.

Darwin attributed the absence of species transitions in the fossil record to his hypothesis that speciation occurs within isolated habitat patches too geographically restricted to be captured by fossil sequences. Mayr's peripatric speciation model added that such speciation would be rapid, further explaining missing evidence of diversification. Indeed, Eldredge and Gould's original punctuated equilibrium model combined Darwin's conjecture, Mayr's model and 124 years of unsuccessfully sampling the fossil record for transitions. Observing such divergence, however, could illustrate the tempo and mode of evolution during early speciation. Here, we investigate peripatric divergence in a Miocene stickleback fish, Gasterosteus doryssus. This lineage appeared and, over approximately 8000 generations, evolved significant reduction of 12 of 16 traits related to armour, swimming and diet, relative to its ancestral population. This was greater morphological divergence than we observed between reproductively isolated, benthic-limnetic ecotypes of extant Gasterosteus aculeatus. Therefore, we infer that reproductive isolation was evolving. However, local extinction of G. doryssus lineages shows how young, isolated, speciating populations often disappear, supporting Darwin's explanation for missing evidence and revealing a mechanism behind morphological stasis. Extinction may also account for limited sustained divergence within the stickleback species complex and help reconcile speciation rate variation observed across time scales.

Fossil-informed biogeographic analysis suggests Eurasian regionalization in crown Squamata during the early Jurassic.

Squamata (lizards, snakes, and amphisbaenians) is a Triassic lineage with an extensive and complex biogeographic history, yet no large-scale study has reconstructed the ancestral range of early squamate lineages. The fossil record indicates a broadly Pangaean distribution by the end- Cretaceous, though many lineages (e.g., Paramacellodidae, Mosasauria, Polyglyphanodontia) subsequently went extinct. Thus, the origin and occupancy of extant radiations is unclear and may have been localized within Pangaea to specific plates, with potential regionalization to distinct Laurasian and Gondwanan landmasses during the Mesozoic in some groups. We used recent tectonic models to code extant and fossil squamate distributions occurring on nine discrete plates for 9,755 species, with Jurassic and Cretaceous fossil constraints from three extinct lineages. We modeled ancestral ranges for crown Squamata from an extant-only molecular phylogeny using a suite of biogeographic models accommodating different evolutionary processes and fossil-based node constraints from known Jurassic and Cretaceous localities. We hypothesized that the best-fit models would not support a full Pangaean distribution (i.e., including all areas) for the origin of crown Squamata, but would instead show regionalization to specific areas within the fragmenting supercontinent, likely in the Northern Hemisphere where most early squamate fossils have been found. Incorporating fossil data reconstructs a localized origin within Pangaea, with early regionalization of extant lineages to Eurasia and Laurasia, while Gondwanan regionalization did not occur until the middle Cretaceous for Alethinophidia, Scolecophidia, and some crown Gekkotan lineages. While the Mesozoic history of extant squamate biogeography can be summarized as a Eurasian origin with dispersal out of Laurasia into Gondwana, their Cenozoic history is complex with multiple events (including secondary and tertiary recolonizations) in several directions. As noted by previous authors, squamates have likely utilized over-land range expansion, land-bridge colonization, and trans-oceanic dispersal. Tropical Gondwana and Eurasia hold more ancient lineages than the Holarctic (Rhineuridae being a major exception), and some asymmetries in colonization (e.g., to North America from Eurasia during the Cenozoic through Beringia) deserve additional study. Future studies that incorporate fossil branches, rather than as node constraints, into the reconstruction can be used to explore this history further.

First record of an Eomysticetidae from the El Cien Formation (late Oligocene), “Ten Minute” locality, Baja California Sur, Mexico

Eomysticetidae (Chaeomysticeti clade) is an archaic family of baleen whales that originated and diversified during the Oligocene epoch. The fossil record of this family is represented by at least 11 formally described species, including records in Baja California Sur (Mexico), Kaiserswerth (Germany), Kitakyushu (Japan), South Carolina (United States), and South Island (New Zealand). Baja California Sur (BCS) possesses important marine deposits from the upper Oligocene, which document a rich diversity of fossil mysticetes, including members of the family Eomysticetidae. In this work, we report a whale specimen collected in the upper Oligocene San Juan Member, El Cien Formation, from the so-called “Ten Minute locality”, San Hilario, about 100 km NW of La Paz, Baja California Sur. The studied specimen consists of an incomplete skull, in which most of the rostrum and part of the occipital shield are missing but preserving one tympanic bulla in situ. This specimen is identified as belonging to the family Eomysticetidae based on both an elongated skull and nasals and transversely narrow and long intertemporal region with a wide exposure of parietals and frontals. The lack of more diagnostic regions precludes its identification at generic/specific levels. The specimen represents the first description of an eomysticetid for the San Hilario area, increasing our knowledge of the evolution of this group of mysticetes and its record in the Pacific basin from the late Oligocene of BCS.

The Middle Triassic palaeontomofauna of Monte San Giorgio with the description of Merithone laetitiae (†Permithonidae) gen. et sp. nov.

AbstractThe Triassic is considered a crucial period for the establishment of the modern insect fauna and fossil records from this period are fundamental for understanding the real impact that the end Permian Mass Extinction events had on these animals. Here, we review the insect fossils from one of the main deposits of this period in the world, Monte San Giorgio, which is considered one of the nine main insect Fossillagerstätten. In this Lagerstätte, located on the border between Switzerland and Italy, a total of 273 fossil insects have been collected in five localities. The fossils found in Val Mara site D, one of the two richest insect fossils sites of Monte San Giorgio, present peculiar features, such as extraordinary sizes and phosphatisation of internal tissues revealing fine internal details. In contrast, the Val Mara site VM 12 fossil record (248 specimens) is dominated by small to medium size insects, usually almost intact, preserving details such as setae on wings and compound eyes. Besides these exceptional features, these fossil insects are of extreme evolutionary importance, since they represent the first or the last occurrence for their lineage. In this regard, their use to calibrate nodes in a phylogenomic dating analysis led to backdating the origin of many insect lineages, including Diptera and Heteroptera. Up to now, a total of five species from Monte San Giorgio have been formally described, belonging to the orders Archaeognatha (†Monura and Machilidae), Ephemeroptera, Hemiptera (Tingidae) and Coleoptera (Adephaga). A further species, Merithone laetitiae (†Permithonidae) gen. et sp. nov., whose fossil is included among the recent findings in Val Mara site VM 12, is described in the present work.

A Saharan fossil and the dawn of Neotropical armoured catfishes in Gondwana

Siluriformes are considered as primarily freshwater and have frequently been a model for the study of historical biogeography. Among catfishes, the most diverse clade is the Loricarioidei, a Neotropical group for which the fossil record extends back to the Palaeocene of Argentina. Here we describe a fossil from the early Late Cretaceous of Morocco, exhibiting typical morphological traits of the Loricariidae. A phylogenetic analysis integrating morphological characters with a multigene database for the main loricarioid lineages and outgroups highly supports inclusion of the fossil within the Loricariidae. A time-calibrated analysis corroborates the origin of loricarioids at about 112 MYA. The presence of this loricariid in Africa provides evidence that loricarioids have diversified before the separation of Africa and South America. The Moroccan loricariid shows an ancient evolutionary history that, in Africa, ended in the Late Cretaceous but persisted in South America, later surviving the K/Pg extinction.

The oldest evidence of symbiosis between mites and fungi with description of a new genus and species of Trochometridiidae (Acari: Heterostigmata) from Cretaceous amber</p >

The female of a new fossil genus and species, Rhombometridium pankowskiorum gen. and sp. nov. (Acari: Trochometridiidae), is described from Cretaceous Kachin amber. The new genus is characterized by the presence of well-developed sporothecae anteriad legs III, each sporotheca containing several ovoid fungal spores. This is the oldest (ca. 100 Mya), evidence of symbiosis between mites and fungi and the first fossil record of the mite family Trochometridiidae. The new genus shares synapomorphies with the family Trochometridiidae (presence of sporothecae between bases of legs III and IV) and Caraboacaridae (rhombic body shape, absence of setae v2, absence of palpal solenidion, palps fused with distinctly widened gnathosomal capsule), and potentially represents a transitional form or a missing link between these two closely related families. We also compare the sporothecae of R. pankowskiorum with those of other heterostigmatic mites.

Taxonomical use of scale ornamentation: Challenges by intraspecific and intra-individual variations in four adult specimens of Polypterus bichir.

Many actinopterygian fish groups, including fossil and extant polypteriforms and lepisosteiforms, fossil halecomorphs, and some basal teleosts, have stout bony scales covered by layers of ganoin-an enamel layer ornamented with minute tubercles. Ganoid scales preserve well as disarticulated remains and notably constitute most of the fossil record for polypteriform in both South America and Africa. Based on two variables (tubercle size and distance between tubercles), some authors reported that the ganoin tubercle ornamentation in these scales is constant within a species and differs between species and allows distinguishing species or at least groups of species. However, despite its promising potential for assessing polypteriform paleodiversity, this tool has remained unused, probably because the variables are not well defined, and intraspecific variation does not seem to have been considered. To address this gap, we aimed to test the intraspecific and intra-individual variation in the ornamentation of ganoid scales in the type species Polypterus bichir. We propose three different parameters to describe the tubercle ornamentation: the distance between contiguous tubercles centers, their density, and their relative spatial organization. With these parameters, we investigate the variation in ganoin ornamentation among four specimens and across different regions of the body. Our results show that the distribution of the tubercles is highly variable within a same species, regardless of the body region, and sometimes even between different sectors of a same scale. Moreover, the variation observed in P. bichir overlaps with the distribution described in the literature for several extant and fossil species. Thus far, the ornamentation of ganoid scales is not a reliable diagnostical feature for polypterids.

Megafauna Fossils in Iran's Quaternary Period: An Overview

The Quaternary is marked by numerous climatic fluctuations, including glacial and interglacial periods. Interglacial periods were characterized by warmer and wetter conditions, and are associated with a unique group of large vertebrate animals, or mammals. Fossil remains of these large mammalian vertebrates, such as elephants, rhinoceroses, horses, deer, and boars, are commonly found in Quaternary sediments. One reason for the abundance of Quaternary vertebrate fossils compared to those from other geological epochs is the relatively young age of Quaternary deposits. Additionally, the size of these creatures' skeletal remains and their higher preservation potential in high-energy environments contribute to their prevalence in the fossil record. In recent years, the study of Quaternary paleontology in Iran has gained significant momentum, with numerous research projects focusing on the animal remains of ancient caves throughout the country. This review aims to summarize and introduce the most significant discoveries in this vital field by examining the regions with substantial Quaternary mammalian vertebrates in Iran. Notable areas include Lorestan, Moghan Plain, Ravansar inKermanshah, Natanz, Isfahan, Qaleh Joq, Torbat Heydarieh, Zaviya Saveh, Shahreza, Isfahan, Qazvin, and Haft Tepeh of Khuzestan. The primary fossils of these regions' large animals, such as elephants, geckos, and horses, have been discussed.

Charting the Course of Pinniped Evolution: insights from molecular phylogeny and fossil record integration.

Pinnipeds (seals, sea lions, walruses, and their fossil relatives) are one of the most successful mammalian clades to live in the oceans. Despite a well-resolved molecular phylogeny and a global fossil record, a complete understanding of their macroevolutionary dynamics remains hampered by a lack of formal analyses that combine these two rich sources of information. We used a meta-analytic approach to infer the most densely sampled pinniped phylogeny to-date (36 recent and 93 fossil taxa) and used phylogenetic paleobiological methods to study their diversification dynamics and biogeographic history. Pinnipeds mostly diversified at constant rates. Walruses however experienced rapid turnover in which extinction rates ultimately exceeded speciation rates from 12-6 Ma, possibly due to changing sea-levels and/or competition with otariids (eared seals). Historical biogeographic analyses including fossil data allowed us to confidently identify the North Pacific and the North Atlantic (plus or minus Paratethys) as the ancestral ranges of Otarioidea (eared seals + walrus) and crown phocids (earless seals), respectively. Yet, despite the novel addition of stem pan-pinniped taxa, the region of origin for Pan-Pinnipedia remained ambiguous. These results suggest further avenues of study in pinnipeds and provide a framework for investigating other groups with substantial extinct and extant diversity.

Exploring the preservation of a parasitic trace in decapod crustaceans using finite elements analysis.

The fossil record of parasitism is poorly understood, due largely to the scarcity of strong fossil evidence of parasites. Understanding the preservation potential for fossil parasitic evidence is critical to contextualizing the fossil record of parasitism. Here, we present the first use of X-ray computed tomography (CT) scanning and finite elements analysis (FEA) to analyze the impact of a parasite-induced fossil trace on host preservation. Four fossil and three modern decapod crustacean specimens with branchial swellings attributed to an epicaridean isopod parasite were CT scanned and examined with FEA to assess differences in the magnitude and distribution of stress between normal and swollen branchial chambers. The results of the FEA show highly localized stress peaks in reaction to point forces, with higher peak stress on the swollen branchial chamber for nearly all specimens and different forces applied, suggesting a possible shape-related decrease in the preservation potential of these parasitic swellings. Broader application of these methods as well as advances in the application of 3D data analysis in paleontology are critical to understanding the fossil record of parasitism and other poorly represented fossil groups.

First fossil pod of Mezoneuron (Caesalpinioideae, Fabaceae) in Asia

The genus Mezoneuron Desf. (Caesalpinioideae, Fabaceae) comprises 23 extant species distributed throughout the Old World tropics and subtropics, yet its fossil record is scarce with finds restricted to Europe and North America. Here, we report a new Mezoneuron pod fossil from the lower Miocene Sanhaogou Formation of Jinggu Basin in Southwest China, representing the first fossil occurrence of this genus in Asia and the only one within its current distribution range. The fossil presents a vascularized wing along the placental suture and with poorly developed, irregular reticulate venation, which are typical pod characters in Mezoneuron. With detailed morphological observation and comparison, it is assigned as a new species, namely M. zhekunii Y.S. Zhao, L.B. Jia et T. Su sp. nov. Together with the historic and modern distribution of Mezoneuron and its relatives, we propose that Mezoneuron originated in the Northern Hemisphere no later than the middle Eocene. Mezoneuron attained relatively low latitudes in Asia no later than the early Miocene, with our fossil representing the lowest latitudinal record. The oblique and fine wrinkles of pod probably suggest a papery texture and low weight observed in mature pods of some extant Mezoneuron species, which favors wind dispersal.