Early Middle Miocene Research Articles

Evolutionary history of Chinese karst loaches (Nemacheilidae, Karstsinnectes): new insights from mitochondrial-based genomes and description of a new species from Guangxi, China

The genus Karstsinnectes of blind fishes known as karst loaches from China was established in 2023 during a revision of the genus Oreonectes (Nemacheilidae). Six species are recorded in this study and some taxonomic progress has been made; however, the lack of genetic data for some species (e.g., K. anophthalmus) may have weakened our current understanding of Karstsinnectes. This study reassessed the phylogeny and evolutionary history of Karstsinnectes by integrating a combination of previously published and newly sequenced mitochondrial genomic data. A phylogenetic tree was developed that was able to divide Karstsinnectes into two clades corresponding to drainages and clarify the phylogenetic position of K. anophthalmus. Divergence times show that Karstsinnectes originated at the Oligocene/Miocene boundary (~22.37 Mya), with the most recent common ancestor occurring in the early Miocene (~18.87 Mya) and interspecific divergence occurring in the late Miocene. Ancestral area reconstruction suggests that the most recent common ancestor of Karstsinnectes most likely inhabited the Hongshui River basin and dispersed into the Zuojiang-Yujiang, Beipanjiang, and Youjiang river basins during the early Miocene (~18.87 Mya), middle Miocene (~12.78 Mya), and late Miocene (~6.71 Mya), respectively. The dispersal under the influence of orogenesis and a monsoon climate drove the speciation and diverse distribution of Karstsinnectes. Such findings are important for conservation considering that Karstsinnectes strictly inhabits deep caves. Additionally, the taxonomic status of the distributed Karstsinnectes population in Leiping Town, Daxin County, Guangxi, China was revised by combining genetic and morphological differences to describe this population as a new species, Karstsinnectes daxinensis Luo, Zhou & Zhou, sp. nov. The definition of the phylogenetic position of K. anophthalmus emphasizes the importance of using type locality material for the identification of cryptic species.

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.

Tuff deposits as preservational context for a Miocene continental mammal assemblage from Patagonia, Argentina

The CO tuff is one of the volumetrically largest volcaniclastic events so far recorded in the Early-Middle Miocene Santa Cruz Formation (Patagonian Argentina). It represents aeolian processes, related with westerlies, that reworked and transported enormous quantities of volcanic ash from the Andes into the continental interior that accumulated in fluvial floodplain deposits. This volcanic event generated a major environmental change at ∼17 Ma (Burdigalian) and hostile living conditions for the biota of the area, at least during the time of deposition. We performed here a comprehensive study including taxonomic, sedimentological, and taphonomic aspects of the mammal assemblage recovered from this tuff deposit. The assemblage is constituted by representatives of Microbiotheria, Paucituberculata, Folivora, Cingulata, Rodentia, Notoungulata, and Litopterna, reflecting a wide mammalian diversity. The formation of the assemblage can be linked to a normal attritional model, in which the death of the individuals and subsequent deposition and burial of their remains would have occurred gradually over time, simultaneously with the accumulation of volcanic ash, at the place of death or very close to it. The time between the death and burial would have been relatively short, in accordance with the rapid and continuous influx of volcanic ash to the depositional environment. This multidisciplinary study allows us to interpret and reconstruct the possible taphonomic pathways of the mammal assemblage and to provide novel information on this particular preservation context linked to volcanically-influenced fluvial environments.

A New Late Early to Early Middle Miocene Fossil Baleen Whale Aff. Isanacetus laticephalus Specimen from Hokkaido, Japan

A New Late Early to Early Middle Miocene Fossil Baleen Whale Aff. Isanacetus laticephalus Specimen from Hokkaido, Japan

Petrogenetic evolution of the Jalapa del Marqués pluton: Miocene arc magmatism in southern Mexico and its tectonic implications

Arc-related plutonic rocks in southern Mexico occur along the Pacific coast in the Sierra Madre del Sur (SMS) igneous province. These rocks record the migration of the Caribbean–North America–Farallon/Cocos junction towards the east between the Late Cretaceous and Miocene. However, little is known about the petrogenesis of igneous rocks that were emplaced during the latest expressions of magmatism in the SMS (i.e., early–middle Miocene). Based on fieldwork, petrography, whole-rock and mineral geochemistry, thermobarometric calculations, and zircon UPb dating, we document the petrogenetic evolution of the Jalapa del Marqués pluton and adjoining intrusions, which are the youngest so far dated in the SMS and are located ∼150 km inland from the present-day trench. This subduction-related magmatic complex consists of granites, granodiorites, diorites, dacite porphyries, and intermediate-to-felsic dikes, whose geochemical features suggest early evolutionary processes driven by fractionation of amphibole ± clinopyroxene (moderate–high pressures) or plagioclase (low pressures). Pulses of evolved magmas were episodically injected into upper-crustal reservoirs (7–14 km) over ∼9 Myr, starting at 22.14 ± 0.65 Ma (2σ)—earlier than previously thought (∼15.7 Ma)—and producing subsequent pulses at 19.45 ± 0.36 Ma, from 16.36 ± 0.37 to 15.8 ± 0.34 Ma, and from 13.9 ± 0.5 to 13.3 ± 0.2 Ma. These ages correlate with the onset and early stages of volcanic centers in the Trans-Mexican Volcanic Belt (TMVB), some of which were located up to 500 km landward from the present-day trench. The large difference in the distance-to-trench between coeval magmatism in the Jalapa del Marqués pluton and the TMVB, indicates a variation in the subduction angle between two segments of the Farallon/Cocos Plate that were likely separated by a slab-tear. The eastward migration of this slab-tear (along with the triple junction) terminated the magmatic activity in the SMS by switching the locus of magmatism to the TMVB. This probably occurred shortly after the studied magmatic complex was assembled.

The Early–Middle Miocene climate as reflected by a mid‐latitude lacustrine record in the Ebro Basin, north‐east Iberia

The Early–Middle Miocene climate as reflected by a mid‐latitude lacustrine record in the Ebro Basin, north‐east Iberia

Stable isotope evidence for resource partitioning in extinct marine carnivores

Living pinnipeds play essential roles in marine ecosystems and display divergent lineage-specific foraging and habitat preferences. The origin of these ecological strategies remains unclear. We analyzed original (n = 22) and published (n = 93) stable carbon (δ13C) and oxygen (δ18O) isotope compositions of tooth enamel from fossil pinnipeds and coeval marine and terrestrial mammals from the late Early Miocene to early Middle Miocene Temblor Formation, the early Middle Miocene Round Mountain Silt Formation at Sharktooth Hill Bonebed, the Middle Miocene of lower levels of the Monterey Formation, and the late Middle Miocene Santa Margarita Formation from the eastern North Pacific Ocean; and original (n = 43) δ13C and δ18O values from the Early Pliocene Yorktown Formation in the western North Atlantic. As expected for aquatic mammals, pinnipeds and control marine mammals had low δ18O variability relative to coeval terrestrial mammals, indicating minimal diagenetic alteration. Among late Early Miocene and Middle Miocene pinnipeds, Allodesmus had lower δ13C values than coeval taxa indicating offshore foraging, in agreement with predictions based on skeletal morphology. However, Allodesmus from the late Middle Miocene Santa Margarita Formation had overlapping δ13C values with co-occurring cetaceans and pinnipeds suggesting preferential nearshore habitat. The stem otariid Pithanotaria had higher enamel δ13C values than co-occurring pinnipeds, indicating nearshore foraging. The stem odobenid Neotherium had intermediate δ13C values supporting foraging between nearshore and offshore predators. Conversely, the stem odobenid cf. Imagotaria had lower enamel δ18O but comparable δ13C values to coexisting pinnipeds, suggesting the exploitation of estuarine resources. At least two ecologically distinct pinniped groups also occurred in the Yorktown Formation. In this unit, the odobenid Ontocetus and some monachinae phocids were predominantly nearshore foragers, with higher enamel δ13C and δ18O values than simultaneously occurring marine mammals. The second group was exclusively composed of phocids, which had comparatively low δ13C and δ18O values, compatible with northward foraging movements along the western North Atlantic coast. The paleoecological profiles of fossils bear strong similarities to the life modes of extant pinniped communities, implying that extant foraging modes appeared early in pinniped evolution and that resource partitioning contributed to their community structure over time.

A new extinct member of the resin producer group of the Mexican amber: Hymenaeaphyllum mirandae n. gen. n. sp. (Detarioideae-Leguminosae)

One of the most important amber deposits with bioinclusion outcrops in Chiapas, southern Mexico, dated ca. 23–15 Ma (early–middle Miocene). Angiosperms (flowering plants) are the most frequently recorded group, with ca. 16 families based principally on fossil flowers and occasional leaves, including members of Leguminosae. This study reports new bifoliolate-compound leaves preserved in Mexican amber, represented by a pair of leaflets marginally attached to a short petiole. Each leaflet is ovate to oblong with an entire margin and has an acuminate apex with a pinnate primary vein. Their characteristics are comparable with bifoliate compound leaves of extant members of Cercidoideae, Caesalpinioideae, and Detarioideae subfamilies. Their asymmetrical base, brochidodromous secondary veins, and abundant translucid glands allow establishment of a new extinct resin-producing member of the Hymenaea clade (Detarieae, Detarioideae), Hymenaeaphyllum mirandae n. gen. n. sp. Hymenaea clade includes Guibourtia, Hymenaea, and Peltogyne, all with similar foliar architecture and other plant characteristics, including reproductive structures. The connection of Hymenaeaphyllum mirandae with extinct members of resin-producing plants recognized previously is uncertain. The discovery of Hymenaeaphyllum mirandae in the Mexican amber suggests that the Boreotropical Flora extended to low latitudes of North America during the Miocene.

First record of Chelonian coprolites from the Early-Middle Miocene Kutch Basin, western India, and their palaeodietary and palaeobiological implications

In this paper, we provide the first data on large (cm-sized) coprolites (represented by three morphotypes) comprising a rare occurrence of eight specimens from a total of three vertebrate-bearing horizons identified within the Early Miocene (Aquitanian) Khari Nadi Formation and Middle Miocene (Burdigalian-Langhian) Chassra Formation, Kutch Basin, western India. The geochemical data confirm the phosphatic character of the investigated ichnofossils. The dominance of partly digested bone matter and presence of plant remains in all the three coprolite morphotypes reflects the omnivorous diet of the producers, which were most likely chelonians. The occurrence of an inclusion (in a coprolite specimen recorded in this study) showcasing an ultrastructure similar to mammalian dental enamel is a rarity in Neogene coprolite records. Additional biotic inclusions observed in the investigated coprolites include ostracods (assigned to genera Paractinocythereis, Hermanites, and Propontocypris); large planispiral benthic foraminifera including the genus Quinqueloculina; uniserial and biserial benthic foraminifera belonging to genus Textularia; marine calcareous algae genus Actinoporella; chrysophytes (resting spores or cysts of planktonic algae); sponge spicules (represented by the morphotypes Acanthoxea and Strongyle); freshwater diatom genus Aulacoseira; unidentified fungal remains; and phytoliths. Taken together, the biotic and abiotic (e.g., pyrite) inclusions, geochemical data and associated microbiota suggest that these ichnofossils were deposited in a dominantly coastal marine (intertidal) setting linked to a lacustrine/palustrine environment.

Osteology of Crocodylus palaeindicus from the late Miocene–Pleistocene of South Asia and the phylogenetic relationships of crocodyloids

Fossil crocodylian remains have been documented from India and other parts of South Asia since the mid-nineteenth century, but specimens attributed to several extinct and extant species of Crocodylus have largely been neglected in modern taxonomic treatments. Here, we present a detailed anatomical description of the extinct species Crocodylus palaeindicus, which we restrict to the late Miocene to early middle Pleistocene of India. Using an autapomorphy-based approach to species-level identification, we regard Crocodylus sivalensis as a junior synonym of C. palaeindicus and provide taxonomic re-identifications of all specimens previously referred to these two species. We present a new diagnosis for C. palaeindicus that facilitates its distinction from the extant mugger crocodile, C. palustris, which does not unequivocally appear in the fossil record prior to the Pleistocene. The lack of clear spatiotemporal overlap, coupled with the otherwise lengthy ghost lineage implied by their sister-taxon relationship in our phylogenetic analyses, provides tentative support that the extant species either is the descendant of C. palaeindicus or originated via budding cladogenesis. An expanded phylogenetic analysis recovers the late Miocene African C. checchiai and Pliocene South American C. falconensis as species within the Neotropical Crocodylus clade, supporting an African origin for this radiation. We also recover Kinyang, from the early–middle Miocene of Kenya, as a crocodyline, rather than an osteolaemine as originally described, and it is potentially the stratigraphically earliest known member of the Crocodylus lineage. Other notable results from our phylogenetic analyses suggest that crocodyloids might not have been present in North America prior to the late Neogene arrival of Crocodylus, with Albertosuchus knudsenii, Prodiplocynodon langi and ‘Crocodylus’ affinis all recovered outside of Crocodyloidea. Furthermore, we demonstrate that an alligatoroid placement for the recently erected latest Cretaceous–Palaeogene East Asian clade Orientalosuchina is highly labile, with relationships at the ‘base’ of Crocodylia unstable.

The Manantiales Basin, Southern Central Andes (∼32°S), Preserves a Record of Late Eocene–Miocene Episodic Growth of an East‐Vergent Orogenic Wedge

AbstractThe Manantiales basin contains >4 km of nonmarine sedimentary strata that accumulated at 31.75–32.5°S during construction of the High Andes. We report field and analytical data from the underexplored northern portion of this basin. The basin contains upper Eocene–middle Miocene strata that accumulated in back‐bulge or distal foredeep through inner‐wedge‐top depozones of the Andean foreland basin as it migrated through this region. A revised accumulation history for the basin‐filling Río de los Patos and Chinches Formations supports a regional pattern of flexure in front of an east‐vergent orogenic wedge. The former formation consists of eolian and localized fluviolacustrine deposits which accumulated between ca. 38 Ma and ≤34 Ma during thrust belt development in Chile. A subsequent ≤12 Myr hiatus may reflect passage of the flexural forebulge or cessation of subsidence during orogenic quiescence. The overlying Chinches Formation records a transition from the foredeep to wedge‐top depozones. Foredeep deposits of east‐flowing, meandering streams were incised prior to ca. 18 Ma, after which deposits of axial rivers, playas, and perennial lakes ponded in a depression behind orogenic topography to the east. After ca. 15 Ma, alluvial‐fan deposits were syndepositionally deformed adjacent to growing thrust‐belt structures along the western basin margin. Although the basin record supports a westward step in the locus of deformation during Early–Middle Miocene time, it conflicts with models involving west‐vergence of the orogenic wedge. Rather, this pattern can be explained as out‐of‐sequence deformation alternating with wedge forward propagation, consistent with Coulomb wedge models incorporating syntectonic sedimentation.

Types and Evolution of the Miocene Reefs Based on Seismic Data in the Beikang Basin, South China Sea

During the Miocene, several reefs formed in the Beikang Basin, South China Sea, which may be potential targets for hydrocarbon exploration. This is due to the environment that developed as a result of the collision, splitting, and splicing of the Nansha Block, which was influenced by the Neogene expansion of the area. However, studies on the types, distribution, controlling factors, and evolution stages of these reefs are scarce. In this study, we used high-resolution seismic data and extensive well-drilling records to gain insights into the evolution of reefs in this particular area. Six distinct types of reefs, namely, the point reef, the platform-edge reef, the block reef, the bedded reef, the pinnacle reef, and the atoll reef, were identified based on our data. These reefs underwent four stages of development. During the initial stage, a few small-sized point reefs emerged in the basin and experienced significant growth during the early Middle Miocene. In the flourishing stage, the reefs predominantly thrived around the Central Uplift and Eastern Uplift areas. In the recession stage, the reefs began to deteriorate during the late Middle Miocene period as a result of the rapid increase in relative sea level caused by tectonic subsidence. In the submerged stage, since the Late Miocene, as the relative sea level continued to rise steadily over time, many reefs that had previously flourished surrounding the Central Uplift and Eastern Uplift areas became submerged underwater, with only a handful of atoll reefs surviving near islands located on the Eastern Uplift. This study indicated the presence of a significant number of well-preserved reefs in the Beikang Basin that have experienced minimal subsequent diagenesis and therefore exhibit high potential as reservoirs for oil and gas exploration.

Structural architecture and maturity of Val d’Agri faults, Italy: Inferences from natural and induced seismicity

The Val d’Agri Basin is a Quaternary sedimentary basin topping multiple tectonic units of the southern Apennines fold-and-thrust belt and a giant oilfield within deeper Apulian Platform carbonates. This basin is bounded by the seismically active East Agri (EAFS) and Monti della Maddalena (MMFS) extensional fault systems. The reservoir rocks are sealed and separated from shallower thrust sheets by a clay-rich and overpressured mélange. The role of this mélange during fault evolution at shallow crustal levels is widely debated and perhaps underestimated. Here, through multi-scale structural analyses and U–Pb dating of syn-tectonic calcite mineralizations, we gain new insights into the Val d’Agri fault system architecture, their structural maturity, and their relations with both natural and induced seismicity. Consistent with present-day NE-SW crustal stretching, the macro-scale structural architecture of both EAFS and MMFS is controlled by NW-SE and NE-SW fault sets, which displaced and in part re-sheared inherited pre- and syn-orogenic structures. The lack of evident clustering of meso-scale faults and the radial pattern of related slickenlines suggest that polygonal-like faulting occurred, particularly along the EAFS, due to lateral spreading of the Irpinia mélange in the subsurface. Structural data show that the MMFS is characterized by a higher structural maturity (slip longevity), with calcite U–Pb ages indicating the onset of long-lasting extensional tectonics in Early-Middle Miocene time. The original results are discussed in terms of seismotectonic setting of the study area, emphasizing the role played by both the thickness and spatial distribution of plastic mélange in modulating fluid pressure and seismic faulting.

Variable behaviour of Abu Jir fault zone, western Iraq

This study sheds light on the dynamic nature of the Abu Jir fault zone, uncovering intriguing contrasts along its path. It was conducted to know the variation through the zone, western Iraq, that starts at Razzazah Lake’s west and continues to Anah city. It is divided into two parts, southern and northern, utilized seismic sections for the southern part whereas fieldwork for the northern part. Seismic sections indicate that the southern part of the fault zone is negative flower structure which develops depressions, while field studies reveal that the northern part is positive behaviour forms some structures such as ridges, relay ramps and controlled the distribution of valleys within its zone. The Abu Jir fault zone not continuous fault but consists of many segments that subject to differential forces of strike-slip movements during Early-middle Miocene. The variation of behaviours is attributed to the difference of the direction between the northern and southern parts of the fault with sense of movement.

Controls on organic matter enrichment of the early-middle Miocene lacustrine oil shale, central Tibet (SW China): New insights from clay minerals and geochemistry

The Lunpola oil shale is the largest lacustrine oil shale deposit in Tibet (SW China), which deposited in a Cenozoic lacustrine rift basin and contains abundant organic matter (OM), whereas the crucial factors that controlled the OM enrichment remain elusive. Here, we present new datasets of total organic carbon (TOC) contents, clay minerals and whole-rock geochemistry of the early-middle Miocene Middle Dingqinghu Formation oil shale from the Lunpola basin, central Tibet, in order to elucidate the paleoclimate, paleo-environment condition and the controlling factors on the OM enrichment of the lacustrine oil shale.Oil shales from the Lunpola East section have high TOC contents (avg. 9.60%), while the contiguous mudstones contain low TOC contents (avg. 0.44%). During the oil shale deposition, high smectite and kaolinite contents, low illite contents and low Sr/Cu ratios suggest strong chemical weathering and hence warm and humid climate, which may probably have close relationship with the mid-Miocene climatic optimum (MMCO). However, during the mudstone deposition, the relatively high illite and low smectite contents and higher Sr/Cu ratios suggest weak chemical weathering, indicating relatively arid climatic condition. The paleo-environment indexes (Corg/P, MoEF and UEF) and MoEF-UEF covariation reflect an anoxic bottom water condition during the oil shale deposition, while the mudstone formed in oxic-dysoxic water environment. The weak and moderate positive relationship between bio-productivity proxies (P/Ti and Cu/Ti ratios) and TOC contents reveal that the bio-productivity condition is not the crucial factor for the OM enrichment. Moreover, the water column environment was brackish and stratified during the oil shale deposition, and the sedimentation rate was moderate, which were also conducive to the OM preservation. The positive correlations between the TOC and the paleoclimate and paleoenvironment proxies demonstrate that warm and humid climate during the MMCO and anoxic water conditions play predominant roles in OM enrichment of the Lunpola lacustrine oil shale. Besides, modest sedimentation rate can prevent the dilution of OM, which can also promote the OM enrichment. This study can not only deepen the understanding of OM enrichment mechanism in lacustrine rift basin but also provide important information for predicting the distribution of the oil shale in the Lunpola Basin.

Structural and Stratigraphic Study of Hazara-Kashmir Syntaxis with the Aid of Geographic Information System and Field Data Approach

Abstract This research area is located along the Hazara-Kashmir Syntaxis in the sub-Himalaya. The Hazara-Kashmir Syntaxis runs through numerous areas within Mirpur district. One of the key characteristics of the Hazara-Kashmir Syntaxis is its antiformality. The project area is bounded to the east by the Riasi fault and to the west by the Jhelum fault, while to the south it is bounded by Salt Range Thrust. Research is being conducted in the areas of Narmah, Sahan, Pirgali, Kas Guma, Mohra Jangu, and Kalri. Fold-and-thrust belts are present in the sub-Himalayan region ofPakistan. Essentially, there are two major folds: the Sahan syncline and the Gaiyan anticline. The Sahan syncline is characterized by an open fold and a southwest orientation. In contrast, open-to-close folds in Gaiyan anticlines are oriented to the southwest. The area is characterized by five major faults: the Narmah fault, the Dhok Poran fault, the Dubal fault, the Pirgali fault, and the Jabi fault. Folds and faults in the project area are the product of NE-SW or NW-SE compaction of the Himalaya. In the research project area sedimentary rocks of Early Miocene- Recent age are located. The rocks which are exposed in the study area includes: the Early-Middle Miocene Kamlial Formation, Middle-Late Miocene Chinji Formation, Late-Miocene Nagri Formation, Late-Miocene Dhok Pathan Formation, Pliocene Soan Formation, and Quaternary Alluvium deposits. Sedimentary structures in the area consist primarily of crossed bedding and rip-ups. These structures define the facing of stratigraphic units.

Phylogenetic relationships and biogeography in Hedysarum (Hedysareae, Fabaceae) with a focus on Central Asian taxa

AbstractCentral Asia, especially the Tian‐Shan and Pamir‐Alay, is a biodiversity hotspot for Hedysarum (Fabaceae) with a high number of endemic species. However, to date, studies of the genus Hedysarum based on molecular data have included only a few species distributed in this region. To fill this gap, we analysed 110 Hedysarum species, 36 of which were from the Tian‐Shan and Pamir‐Alay Mountains of Central Asia. We performed phylogenetic analyses, divergence time estimates, and biogeographic analyses using both the internal transcribed spacers of nuclear ribosomal DNA (nrDNA ITS) and three plastid DNA (cpDNA) sequences (trnL‐trnF, matK, psbA‐trnH). Our phylogenetic analysis grouped the species of Hedysarum into three sections: H. sect. Hedysarum, sect. Multicaulia, and sect. Stracheya, which are largely consistent with previous phylogenetic classifications. Accordingly, most of the Central Asian species we studied (28 spp.) were placed in H. subsect. Crinifera within H. sect. Multicaulia. Our divergence time and biogeographic analyses indicate that Hedysarum likely originated in West Asia and/or East Asia during the Early Miocene or Middle Miocene and subsequently dispersed to adjacent areas of Eurasia, as well as North America via the Bering Land Bridge. The likely area of origin for H. sect. Multicaulia is West Asia, while East Asia appears to be the center of origin for H. sect. Hedysarum and sect. Stracheya. In addition, we suggest that the rapid radiation of the species of H. subsect. Crinifera occurred in the Tian‐Shan and Pamir‐Alay Mountains, as well as the Turkish‐Iranian Plateau, and that geological and climatic changes were the main causes of speciation in Hedysarum.

The Architectonicidae and Mathildidae (Gastropoda, Heterobranchia) of the Miocene Paratethys Seavictims of the Miocene Climatic Transition.

The Architectonicidae of the Miocene of the Central Paratethys Sea comprise 18 species placed in eight genera. The coeval Mathildidae are documented by nine species, placed into three genera. We present descriptions of these species and illustrate type material wherever possible. Several species suggest relationships with Late Miocene to Holocene species of the Mediterranean Sea, although none of the species is known from modern faunas. Both families attained their maximum diversity during the early Middle Miocene (Langhian), and both families experienced a dramatic loss in species richness at the Langhian/Serravallian boundary. This Architectonicidae/Mathildidae turnover evidently coincided with the Miocene Climatic Transition, suggesting climate as the driving force. As members of both families feed on coelenterates, we assume that the climatic cooling of that phase caused a retreat of cnidarians, which is reflected in a decline in their predators. Ammotectonica nov. gen., Simplexollata nov. gen. and Pseudotuba nov. gen. are introduced as new genera. Ammotectonica gregorovae nov. sp., Simplexollata anticollata nov. sp., Nipteraxis deformatus nov. sp., Solatisonax? transversa nov. sp., Heliacus globosus nov. sp., Solatisonax tavianii nov. sp., and Pseudotorinia grasemanni nov. sp. are described as new species. Solarium (Torinia) criticum Boettger, 1907 and Discohelix quinquangularis Boettger, 1902 are treated as subjective junior synonyms of Heliacus berthae (Boettger, 1902) and Spirolaxis cornicula (Boettger, 1902).

Small Ducks (Aves: Anatidae) from the Early–Middle Miocene of Eurasia. 3. A Revision of <i>Mionetta natator</i> (Milne-Edwards, 1867)

The results of a taxonomic and morphological revision of Mionetta natator (Milne-Edwards, 1867) from the lower Miocene of Western and Central Europe are presented. It is shown that the collections of small ducks from Saint-Gérand-le-Puy localities (France) indeed contain a small species of the genus Mionetta, which is here described as Mionetta defossa sp. nov. At the same time, Mionetta natator represents a separate taxon and is here assigned to the genus Caerulonettion gen. nov., showing morphological similarities with modern Malacorhynchus and fossil Mioquerquedula spp. The first finds of small ducks from the lower Miocene of Kazakhstan are also described (Aral Svita, the Agyspe and Altynshokysu localities; Akzhar Svita, the Blue Sands locality), tentatively attributed to Mionetta defossa and Mionetta sp. The diversity and relationships of small ducks of the early–middle Miocene of Eurasia are discussed.

Miocene Stromboid Gastropods (Superfamily Stromboidea Rafinesque, 1815) from the Dwarka Basin, Western India and their Paleobiogeographic Implications

Abstract Stromboid gastropods (Superfamily Stromboidea) are one of the most diverse groups of gastropods present in the Neogene marine successions of western India. In the present endeavor, we report eight stromboid species, of which four are described as new, from the early-middle Miocene marine successions of the Dwarka Basin, western India. The species are Conomurex indica n. sp., Persististrombus deperditus, Persististrombus sp., Dilatilabrum mahalonobisi n. sp., Tibia indica, Terebellum obtusum, Hemithersitea kanerus n. sp. and Hemithersitea nadharus n. sp. Paleobiogeographic distribution of most of the stromboid genera reported here reveals a unidirectional migration from the Tethys Region towards the Indo-Pacific Region during the Paleogene and Neogene. Conomurex originated in the western India and further radiated to the eastern Indian-Western Pacific localities with the onset of the Neogene. Persististrombus and Tibia show widespread distribution in the Mediterranean and gradually radiated towards the eastern Africa-western India localities during the Paleogene. However, from the middle Miocene onwards, these two genera further migrated towards the eastern Indian-Western Pacific localities and became more diverse. The remaining two genera, i.e., Dilatilabrum and Hemithersitea originated in the Mediterranean and later migrated to take refuge in western India during the late Paleogene, and ultimately succumbed to extinction during the middle Miocene.