Late Miocene marine ostracods from Santa Maria island,Azores (NE Atlantic): Systematics,palaeoecology and palaeobiogeography

The nine oceanic islands that comprise the Azores archipelago are located in the middle of the northern Atlantic Ocean. In this isolated archipelago, there is a rich fossil record in one of the islands, Santa Maria. In this island, samples were collected in the Upper Miocene composite section of Malbusca outcrop, located in the southern shore of the island, and the fossil marine Ostracoda were studied. This work represents the first report of fossil ostracods from the Azores archipelago. Thirteen species were found, representing seven families and 12 genera (Xestoleberis, Loxoconcha, Callistocythere, Leptocythere, Dameriacella, Aurila, Heliocythere, Pachycaudites, Neonesidea, Cyamocytheridea, ?Quadracythere and Paracypris). Among the identified species, one new species, Leptocythere azorica n. sp., is described. Loxoconcha (two species) was the most diversified genus. The collected species are mainly ornamented and typical of warm waters and epi-neritic habitats (～ 10–50 m of depth).     

Lamniform Shark Teeth from the Late Cretaceous of Southernmost South America (Santa Cruz Province,Argentina)

Here we report multiple lamniform shark teeth recovered from fluvial sediments in the (Campanian-Maastrichtian) Cerro Fortaleza Formation, Santa Cruz Province, Argentina. This small tooth assemblage is compared to various lamniform sharks possessing similar dental morphologies, including Archaeolamna, Cretalamna, Dwardius, Dallasiella, and Cretodus. Although the teeth share numerous morphological features with the genus Archaeolamna, including a developed neck that maintains a relatively consistent width along the base of the crown, the small sample size and incomplete nature of these specimens precludes definitive taxonomic assignment. Regardless, the discovery of selachian teeth unique from those previously described for the region broadens the known diversity of Late Cretaceous South American sharks. Additionally, the discovery of the teeth in fluvial sandstone may indicate a euryhaline paleobiology in the lamniform taxon or taxa represented by this tooth assemblage.     

Neogene stratigraphy,foraminifera, diatoms,and depositional history of Maria Madre Island,Mexico: Evidence of early Neogene marine conditions in the southern Gulf of California

Foraminifera and diatoms have been analyzed from an upper Miocene through Pleistocene(?) sequence of marine sediments exposed on Maria Madre Island, largest of the Trés Marias Islands off the Pacific coast of Mexico. The Neogene stratigraphic sequence exposed on Maria Madre Island includes a mid-Miocene(?) non-marine and/or shallow marine sandstone unconformably overlain by a lower upper Miocene to uppermost Miocene upper to middle bathyal laminated and massive diatomite, mudstone, and siltstone unit. This unit is unconformably overlain by lower Pliocene middle to lower bathyal sandstones and siltstones which, in turn, are unconformably overlain by upper Pliocene through Pleistocene(?) upper bathyal to upper middle bathyal foraminiferal limestones and siltstones. These beds are unconformably capped by Pleistocene terrace deposits. Basement rocks on the island include Cretaceous granite and granodiorite, and Tertiary(?) andesites and rhyolites. The upper Miocene diatomaceous unit contains a low diversity foraminiferal fauna dominated by species of Bolivina indicating low oxygen conditions in the proto-Gulf Maria Madre basin. The diatomaceous unit grades into a mudstone that contains a latest Miocene upper to middle bathyal biofacies characterized by Baggina californica and Uvigerina hootsi along with displaced neritic taxa. An angular unconformity separates the upper Miocene middle bathyal sediments from overlying lower Pliocene siltstones and mudstones that contain a middle to lower bathyal biofacies and abundant planktonic species including Neogloboquadrina acostaensis and Pulleniatina primalis indicating an early Pliocene age. Significantly, this Pliocene unit contains common occurrences of benthic species restricted to Miocene sediments in California including Bulimina uvigerinaformis. Pliocene to Pleistocene(?) foraminiferal limestones and siltstones characterize submarine bank accumulations formed during uplift of the Trés Marias Island area, and include abundant planktonic foraminifera such as Pulleniatina obliquiloculata and Neogloboquadrina duterteri. Common benthic foraminifera in this unit are indicative of upper bathyal water depths. The Neogene depositional history recorded on Maria Madre Island involves an early late Miocene subsidence event marking formation of the Trés Marias Basin with relatively undiluted diatomaceous sediment deposited in a low oxygen setting. Subsidence and deepening of the basin continued into the early Pliocene along with rapid deposition of terrigenous clastics. Uplift of the basinal sequence began in late Pliocene time accompanied by deposition of upper Pliocene-Pleistocene foraminiferal limestones on a rising submarine bank. Continued episodic uplift of the Neogene deposits brought the island above sea level by late Pleistocene time.     

The fossil turtles of Greece: An overview of taxonomy and distribution

Turtle remains are common in the Miocene-Holocene deposits of Greece, and are a key focus of the growing research interest in Neogene herpetofaunas from the Aegean region. Some of the most important finds include one of Europe's stratigraphically youngest pleurodiran taxa, Nostimochelone lampra, from the Early Miocene of Macedonia, together with arguably the richest record of fossil tortoises from the Eastern Mediterranean. This incorporates the presently oldest definitive representatives of the quintessential genus Testudo sensu stricto from the Late Miocene of Attica and Macedonia, and numerous specimens of the colossal (carapace ∼2 m-length) testudinid Cheirogaster from Late Miocene-Late Pliocene sediments in southern and northern Greece, as well as on the eastern Aegean islands of Samos and Lesvos. Tantalising, but as yet unconfirmed Miocene accounts of the geoemydid Mauremys in Macedonia, and indeterminate emydid-like remains from Euboea, also provide potentially significant range extensions. Although hampered by a historically sparse documentation, the fossil turtles of Greece are a significant resource that record both assemblage changes and the origin of modern lineages.     

New chondrichthyan fauna from the Palaeogene deposits of Barmer district,Rajasthan, western India: Age,palaeoenvironment and intercontinental affinities

Field investigations of the Palaeogene sections exposed in Barmer district, Rajasthan (India) led to the discovery of a new fossiliferous horizon in the Padma Rao Open Cast Bentonitic Clay Quarry. The bentonitic clay sequence of this quarry is considered as representing the upper part of the shale, carbonaceous shale, lignite and bentonitic clay succession of the Akli Formation exposed in the Giral Lignite Mine, 2.5 km to its north. Screen-washing of the sediments from a fossiliferous level within the bentonitic clay of the new site has yielded nine taxa of sharks and batoids: Squatiscyllium nigeriensis White, 1934, Ginglymostoma sokotoense White, 1934, Ginglymostomatidae gen. et sp. indet., Brachycarcharias sp., Abdounia recticona Winkler, 1873, Premontreia (Oxyscyllium) peypouqueti Noubhani et Cappetta, 1997, Eotorpedo hilgendorfi Jaekel, 1904, Coupatezia sp. cf. C. danica, and Myliobatidae gen. et sp. indet. The fauna recovered is mainly represented by nearshore shallow marine forms. This fauna is quite different from that of Palaeocene Fatehgarh Formation, the Lower Eocene Kapurdi Formation (Barmer Basin), the Khuiala Formation (Jaisalmer Basin) and the Cambay Shale (Cambay Basin), and favours a late Palaeocene (Thanetian) age for the upper part of the Akli Formation. A nearshore shallow marine palaeoenvironment is favored for the investigated stratigraphic horizon on the basis of the selachian fauna. Majority of the fossil shark species described from the Padma Rao quarry section are known from a number of sites in Africa, western Europe, Asia and southeastern USA, suggesting that free faunal interchanges were possible between the western Tethys and Indo-Madagascan faunal provinces during the late Palaeocene.     

Giant-toothed white sharks and cetacean trophic interaction from the Pliocene Caribbean Paraguaná Formation

The role of the extinct giant-toothed white sharkCarcharodon megalodon (Agassiz) in the Caribbean Neogene is discussed based on new evidence of predation on cetaceans from the Lower Pliocene Paraguaná Formation in Venezuela. Large sharks have occupied the highest trophic level in the marine environment. However, based on the recovery of a giant white shark tooth piercing a cetacean lumbar vertebra, the predator-prey relationship is discussed under the hypothesis of initial shark attack, subsequent floating transport of the cetacean carcass, and scavenging prior to deposition on the bottom. The scarce Caribbean fossil records of both giant-toothed sharks and cetaceans suggest that these species were transients during the Pliocene on the Venezuelan coast.      

ORIGINAL ARTICLE: Mass extinctions in the Azores during the last glaciation: fact or myth?

Aim The influence of the last glaciation on the shallow‐water marine malacofauna of the Azores Islands is reviewed. We test, for this fauna, the ‘Pleistocene temperature theory’ of J.C. Briggs, which hypothesizes that a (supposed) lack of endemics in the older (Azorean endemic) fauna resulted from extinctions caused by a severe drop in sea surface temperatures during the Pleistocene. Location Santa Maria Island, Azores, Portugal. Methods We compare the fossil mollusc fauna of Prainha, Praia do Calhau and Lagoinhas Pleistocene outcrops with the recent mollusc fauna of the Azores Islands. We dated the fossil fauna, using shells of Patella aspera Röding, 1798, by standard U/Th methodology at the GEOTOP laboratory (Université du Québec à Montreal, Canada). Results Dating of the shells of P. aspera indicates that the deposition of the lower unit of the Prainha outcrop corresponded to Marine Oxygen Isotope Substage 5e (MISS 5e). Not a single endemic Azorean species of mollusc that is present in the Pleistocene fossil record has since become extinct, and we found no signs of ‘mass extinctions’ in the littoral marine molluscs of the Azores. The only species that were extirpated from these islands were thermophilic molluscs and littoral bivalves living in fine sand. Main conclusions Our results do not support Briggs’‘Pleistocene temperature theory’. Nor did we find evidence supporting the hypothesis that most of the marine organisms now present in the Azores recolonized the islands after the last glacial maximum.     

Population genetics and conservation of the Azorean tree Picconia azorica

Picconia azorica (Tutin) Knobl. (Oleaceae) is an endangered species, endemic to the Azores. Samples from 31 populations in 8 islands were genotyped using 8 newly developed nuclear microsatellite markers. From the amplified loci, 81% were polymorphic across all populations and the species showed a relatively high total genetic diversity (H_T = 0.7). Several populations were close to Hardy–Weinberg equilibrium while others presented positive F_IS values (0.02–0.2). The largest proportion of genetic variation (98%) occurred within populations and the level of differentiation between populations, was generally low, although 27% of the population pairwise comparisons showed relatively high differentiation values (0.25 ≤ R_ST ≤ 0.65). Relatively high levels of gene flow were also found among most populations. Using the Bayesian clustering method implemented in STRUCTURE we found a particular genetic pattern in Corvo samples, and also similarities between Santa Maria, São Miguel and Flores populations. Considerable levels of genetic admixture within P. azorica populations might have resulted from: (i) fruit dispersal by native birds; and/or (ii) human mediated dispersal between islands. Our results revealed the existence of some genetically depauperate populations needing specific conservation measures, and indicate that arbitrary translocation of individuals between islands should be avoided.     

When Did Carcharocles megalodon Become Extinct? A New Analysis of the Fossil Record

Carcharocles megalodon (“Megalodon”) is the largest shark that ever lived. Based on its distribution, dental morphology, and associated fauna, it has been suggested that this species was a cosmopolitan apex predator that fed on marine mammals from the middle Miocene to the Pliocene (15.9–2.6 Ma). Prevailing theory suggests that the extinction of apex predators affects ecosystem dynamics. Accordingly, knowing the time of extinction of C. megalodon is a fundamental step towards understanding the effects of such an event in ancient communities. However, the time of extinction of this important species has never been quantitatively assessed. Here, we synthesize the most recent records of C. megalodon from the literature and scientific collections and infer the date of its extinction by making a novel use of the Optimal Linear Estimation (OLE) model. Our results suggest that C. megalodon went extinct around 2.6 Ma. Furthermore, when contrasting our results with known ecological and macroevolutionary trends in marine mammals, it became evident that the modern composition and function of modern gigantic filter-feeding whales was established after the extinction of C. megalodon. Consequently, the study of the time of extinction of C. megalodon provides the basis to improve our understanding of the responses of marine species to the removal of apex predators, presenting a deep-time perspective for the conservation of modern ecosystems.     

First porcupine fossils (Mammalia,Rodentia) from the late Miocene of NW Iran,with notes on late Miocene–Pliocene dispersal of porcupines

This paper describes the first fossil porcupine remains from Iran. Four upper cheek teeth and two fragmentary lower incisors present sufficient characters for identification as Hystrix aryanensis, a species previously known from the late Miocene locality of Molayan (Afghanistan) estimated at ca. 7–8 Ma. The dental features of porcupines are discussed to show their systematic value and highlight evolutionary trends in late Miocene and Pliocene porcupines. This study also discusses the dispersal history of fossil porcupines in relation to paleobiogeographic provinces and environmental changes during late Miocene to late Pliocene time.     

Additional fish recordsfrom the Judith River Formation (Campanian) of Montana

The recent recovery of additional fish remains from several fossil sites in Blaine County. Montana, allows us to add a new species of selachian and the occurrence of two genera of Chimaeriformes to the total vertebrate faunal assemblage of the Judith River Formation (Campanian).The new selachian genus is: Chiloscyllium missouriensis, a representative of the family: Orectolobidae.In association with the new orectolobid, there are representatives of the Chimaeroids: Ischyodus bifurcatusCase, and Elasmodus cf. greenoughiAgassiz.These new additions increase the total vertebratefaunnal assemblage of the Judith River Formation to twenty species.     

Labyrinth morphology and the evolution of low-frequency phonoreception in elasmobranchs

Labyrinth morphology in extant elasmobranchs (neoselachians: sharks, skates and rays) and several extinct chondrichthyans ranging in age from Pliocene to Devonian is investigated using high-resolution computed tomography (CT scanning) and digital reconstitution techniques. The elasmobranch labyrinth is highly specialized toward low-frequency semi-directional sound detection (LFSDP), optimally around 100 Hz. Several features associated with LFSDP in neoselachians also occur in Mesozoic hybodonts (e.g., Egertonodus, Tribodus) and in some incertae sedis extinct sharks (Acronemus, Tristychius), but are absent in osteichthyans, extant and fossil holocephalans, and certain Paleozoic chondrichthyans (ctenacanths, symmoriiforms, Pucapampella). Thus, LFSDP is regarded as an evolutionary novelty of elasmobranchs that arose some time after their divergence from chimaeroids. The suite of characters associated with LFSDP was probably acquired progressively, some characters being more widely distributed among fossil chondrichthyans than others. LFSDP evolved only within chondrichthyans whose otico-occipital fissure became secondarily closed during ontogeny.     

New observations on the Late Miocene–Early Pliocene Lutrinae (Mustelidae: Carnivora,Mammalia) from the Middle Awash,Afar Rift,Ethiopia

New observations on the Late Miocene and Earliest Pliocene mustelids from the Middle Awash of Ethiopia are presented. The Middle Awash study area samples the last six million years of African vertebrate evolutionary history. Its Latest Miocene (Asa Koma Member of the Adu-Asa Formation, 5.54–5.77 Ma) and Earliest Pliocene (Kuseralee and Gawto Members of the Sagantole Formation, 5.2 and 4.85 Ma, respectively) deposits sample a number of large and small carnivore taxa among which mustelids are numerically abundant. Among the known Late Miocene and Early Pliocene mustelid genera, the Middle Awash Late Miocene documents the earliest Mellivora in eastern Africa and its likely first appearance in Africa, a new species of Plesiogulo, and a species of Vishnuonyx. The latter possibly represents the last appearance of this genus in Africa. Torolutra ougandensis is known from both the Late Miocene and Early Pliocene deposits of the Middle Awash. The genus Sivaonyx is represented by at least two species: S. ekecaman and S. aff. S. soriae. Most of the lutrine genera documented in the Middle Awash Late Miocene/Early Pliocene are also documented in contemporaneous sites of eastern Africa. The new observations presented here show that mustelids were more diverse in the Middle Awash Late Miocene and Early Pliocene than previously documented.     

The colonization history of Juniperus brevifolia (Cupressaceae) in the Azores Islands

Background

A central aim of island biogeography is to understand the colonization history of insular species using current distributions, fossil records and genetic diversity. Here, we analyze five plastid DNA regions of the endangered Juniperus brevifolia, which is endemic to the Azores archipelago.

Methodology/Principal Findings

The phylogeny of the section Juniperus and the phylogeographic analyses of J. brevifolia based on the coalescence theory of allele (plastid) diversity suggest that: (1) a single introduction event likely occurred from Europe; (2) genetic diversification and inter-island dispersal postdated the emergence of the oldest island (Santa Maria, 8.12 Ma); (3) the genetic differentiation found in populations on the islands with higher age and smaller distance to the continent is significantly higher than that on the younger, more remote ones; (4) the high number of haplotypes observed (16), and the widespread distribution of the most frequent and ancestral ones across the archipelago, are indicating early diversification, demographic expansion, and recurrent dispersal. In contrast, restriction of six of the seven derived haplotypes to single islands is construed as reflecting significant isolation time prior to colonization.

Conclusions/Significance

Our phylogeographic reconstruction points to the sequence of island emergence as the key factor to explain the distribution of plastid DNA variation. The reproductive traits of this juniper species (anemophily, ornithochory, multi-seeded cones), together with its broad ecological range, appear to be largely responsible for recurrent inter-island colonization of ancestral haplotypes. In contrast, certain delay in colonization of new haplotypes may reflect intraspecific habitat competition on islands where this juniper was already present.     

Exploring the Formation of a Disjunctive Pattern between Eastern Asia and North America Based on Fossil Evidence from Thuja (Cupressaceae)

Thuja, a genus of Cupressaceae comprising five extant species, presently occurs in both East Asia (3 species) and North America (2 species) and has a long fossil record from Paleocene to Pleistocene in the Northern Hemisphere. Two distinct hypotheses have been proposed to account for the origin and present distribution of this genus. Here we recognize and describe T. sutchuenensis Franch., a new fossil Thuja from the late Pliocene sediments of Zhangcun, Shanxi, North China, based on detailed comparisons with all living species and other fossil ones, integrate the global fossil records of this genus plotted in a set of paleomaps from different time intervals, which show that Thuja probably first appeared at high latitudes of North America in or before the Paleocene. This genus reached Greenland in the Paleocene, then arrived in eastern Asia in the Miocene via the land connection between East Asia and western North America. In the late Pliocene, it migrated into the interior of China. With the Quaternary cooling and drying, Thuja gradually retreated southwards to form today’s disjunctive distribution between East Asia and North America.     

Leaf beds in the Early Miocene lacustrine deposits of the Geumgwangdong Formation,Korea: Occurrence,plant–insect interaction records,taphonomy and palaeoenvironmental implications

Occurrence, preservation and evidence of plant–insect interactions in the leaf deposits of the early Miocene Geumgwangdong Formation are described, and the taphonomy and palaeoenvironmental implications are interpreted. The Geumgwangdong leaf beds are tuffaceous lacustrine deposits consisting mainly of thin-bedded sediments, including shale. Deposition was dominated through the vertical aggradation of fine-grained sediments by suspension sedimentation, rather than by the fluvial deposition of coarse-grained sediments. The majority of the fossil leaves were preserved by compression rather than merely preserved as impressions. The Geumgwangdong leaf deposits can be characterised as a wind-transported, dysaerobic, deep-water, lake taphofacies with some influence of water-transport. The fossil flora of the Geumgwandong Formation consists of 64 taxa belonging to 27 families and 43 genera. The dominant taxa were Metasequoia, Fagus, Betula, Quercus, Acer, Zelkova, and Leguminosae, which is comparable to the Early Miocene cool–temperate Aniai-type Flora of north-east Japan. The similarity between the lake settings of the Geumgwangdong Formation and the Aniai Coal-bearing Formation might have been a factor in the development of similar plant–fossil assemblages. Although traces of insect damage in the fossil leaves of the Geumgwangdong Formation were commonly observed, more than 90% of the damaged leaves showed a low level of diversity and degree of insect damage (< 10%), which is indicative of a cool–temperate palaeoclimatic condition. Despite latitudinal differences and geographic separation, the development of similar floras in the Geumgwangdong Formation of south-east Korea and the Aniai Coal-bearing Formation of north-east Japan during the early Miocene could have been influenced by the incipient NW–SE sea-floor spreading that resulted in the opening of the East Sea (Sea of Japan), which might have enabled floral migration between the two regions. This study provides useful data for understanding not only the taphonomy and palaeoenviroments of the leaf deposits, but also the spatial development of the flora resulting from palaeogeographic changes driven by tectonic movement during the early Miocene in Far East Asia.     

First fossil record of Vipera Laurenti 1768 “Oriental vipers complex” (Serpentes: Viperidae) from the Early Pliocene of the western Mediterranean islands

The first fossil record of Vipera “Oriental vipers complex” (Serpentes: Viperidae) in the western Mediterranean islands is presented. Two large-sized vertebrae were found in an Early Pliocene karstic deposit located on the eastern coast of Mallorca, close to Caló den Rafelino (Manacor). The centrum length of the trunk vertebra (12.7 mm) represents the largest-sized known specimen of the European vipers belonging to the “Oriental vipers complex” and it suggests a body length close or greater than 200 cm. The arrival of this snake to Mallorca probably took place during the Messinian Salinity Crisis of the Mediterranean Sea (Late Miocene, 5.6-5.32 My ago) and it should be considered as one of the largest predators in Mallorca during the Early Pliocene. Although patterns of body size change in island snakes are unclear, some considerations about the large size of the Caló den Rafelino viper and co-evolution with endothermic preys are proposed.     

Use of nursery areas by the extinct megatooth shark Otodus megalodon (Chondrichthyes: Lamniformes)

Nursery areas are fundamental for the success of many marine species, particularly for large, slow-growing taxa with low fecundity and high age of maturity. Here, we examine the population size-class structure of the extinct gigantic shark Otodus megalodon in a newly described middle Miocene locality from Northeastern Spain, as well as in eight previously known formations (Temblor, Calvert, Pisco, Gatún, Chucunaque, Bahía Inglesa, Yorktown and Bone Valley). In all cases, body lengths of all individuals were inferred from dental parameters and the size-class structure was estimated from kernel probability density functions and Gaussian mixture models. Our analyses support the presence of five potential nurseries ranging from the Langhian (middle Miocene) to the Zanclean (Pliocene), with higher densities of individuals with estimated body lengths within the typical range of neonates and young juveniles. These results reveal, for the first time, that nursery areas were commonly used by O. megalodon over large temporal and spatial scales, reducing early mortality and playing a key role in maintaining viable adult populations. Ultimately, the presumed reliance of O. megalodon on the presence of suitable nursery grounds might have also been determinant in the demise of this iconic top predatory shark.