Geobios最新文献

The number of late Neogene Spanish micromammal-containing continental sections with a correlation to the Geomagnetic Time Scale is steadily growing. Nonetheless, well-calibrated sections with dense micromammal records are still rare, biostratigraphic correlations between basins are not straightforward, and ages of uncalibrated sites are poorly constrained. Here, we aim at improving the chronology of Iberian micromammal sections and sites for the interval 8.5–2 Ma by: (i) analyzing qualitative and quantitative similarities between rodent assemblages and turnover in the different basins, (ii) formulating a system of fifteen Iberian assemblage biozones, and (iii) constraining the ages of zone boundaries, assuming isochroneity across basins. Age uncertainty ranges for most known Iberian micromammal sites are obtained by combining regional biozone boundary ages with local magnetostratigraphic records, sedimentation rates and/or evolutionary rates. In addition, our results include new, integrated stratigraphic records from the Jumilla-La Celia and Teruel Basins, which are used to constrain the thus far poorly dated interval covering the latest Tortonian and earliest Messinian (8–7 Ma).

In this paper, we describe anatomical structures of 11 fossil wood samples collected from two localities (Brown Sands and Flat Sands) of the Usno Formation, in the Lower Omo valley, Ethiopia. On the basis of former stratigraphy and new investigation, notably Ar/Ar dating of intercalated tuffs and palaeomagnetic studies, the samples are dated between 3.33 and 3.21 Ma. The identified wood samples have been collected within two distinct stratigraphic layers deposited during this time range. The oldest one from Brown Sands includes Albizia sp., Entada sp. and a possible Combretaceae or Leguminosae. The youngest assemblage from White Sands includes many representatives of Combretaceae including Combretum molle and Terminalia sp. associated with Erythrina sp. These assemblages strongly differ from other Miocene and Pliocene wood assemblages known from Ethiopia. Palaeoenvironmental interpretation of the identified tree taxa support affinities with the extant mid-elevation Albizia forest replaced by Combretum/Terminalia woodland in about one hundred thousand years. In the Lower Omo valley, the more humid character of the Pliocene vegetation strongly contrast with the arid Acacia/Commiphora steppe widely spread over the region today. Such past vegetation attests to much wetter and favourable climatic conditions under seasonal climate. However significant changes in the floristic composition of tree cover occurring within a timespan of hundred thousand years, plays in favour of climatic and palaeo-environmental instabilities at a time when Australopithecus afarensis existed in the Turkana basin and flourished elsewhere in Ethiopia.

Pleuromeia Corda is an iconic lycopod genus in the Early Triassic floras of the world. Pleuromeia fossils are very significant in stratigraphy and palaeoenvironmental interpretation and have been regarded as an important Lower Triassic index fossil. Although some recent studies show that the genus occurred in the lower part of the Middle Triassic, no definite Pleuromeia has been reported from the late Middle Triassic and the younger strata so far. In this paper, some reproductive organ fossils of Pleuromeia from the upper Middle Triassic Tongchuan Formation in Shaanxi Province (belonging to the Ordos Basin), North China, are described for the first time, belonging to the new species Pleuromeia obovata Deng nov. sp. Highly accurate dating results of tuff layers indicate that the age of the new species is between 241.06 ± 0.12 Ma and 241.558 ± 0.093 Ma, equivalent to the early Ladinian. This is the youngest species of genus Pleuromeia so far. Spatiotemporal distribution of Pleuromeia indicates that the genus first appeared in the Induan (Early Triassic) in North China, occurred widespread and flourished in both Laurasia and Gondwana during the Olenekian (late Early Triassic), declined from the Anisian (early Middle Triassic), survived in the Ladinian in North China, and may have gone extinct as early as the end of the Middle Triassic. North China may well have included the place of origination and the last habitats of this genus.

Conodonts are very abundant, present a wide occurrence worldwide and high evolutionary rates during the Paleozoic and the Triassic, providing the recognition of more than 240 biozones over the 300 million years of their geological history. Neognathodus comprises species useful as biostratigraphic markers for the early-to-middle Pennsylvanian succession. In this paper, we analyze the record of this genus within the Amazonas Basin, northern Brazil, based on 18 wells and several outcropping sections, including limestone exploratory mines, related to the marine deposits of the Tapajós Group (Monte Alegre, Itaituba and Nova Olinda formations). Taxa have been revised, updated and some have been reclassified according to current international taxonomy. All records of this genus were morphologically analyzed using stereomicroscope and Scanning Electronic Microscope images, allowing the recognition of six species: N. symmetricus, N. bassleri, N. medadultimus, N. atokaensis, N. bothrops, and N. roundyi. The occurrences of these species as well their areal distribution in the basin were detailed, resulting in several modeling stratigraphic maps. Four biozones are proposed herein, in ascending stratigraphic order: (i) N. symmetricus-N. bassleri interval Zone, (ii) N. bassleri-N. symmetricus interval Zone, (iii) N. atokaensis taxon range Zone, and (iv) N. atokaensis-N. bassleri interval Zone. A middle Bashkirian to middle Moscovian age is assigned to the studied marine deposits of the Tapajós Group. Neognathodus is related worldwide to neritic, warm and oxygenated water environments both in high energy proximal contexts and in lower energy more distal environments, slightly deeper waters and periodically affected by storms.

Eurypterids constituted an important component of Paleozoic marine ecosystems, but their fossil record has been mainly reported from North America and Europe, and the evolution of this group in other regions such as East Asia remains poorly understood. A new eurypterid, Malongia mirabilis nov. gen., nov. sp., is described from the Lower Devonian (Lochkovian) Xiaxishancun Formation of Qujing, Yunnan, southwestern China. The holotype shows a ventral prosoma with appendages II–VI and part of the opisthosoma. The characters indicating a dolichopterid affinity of the new taxon include: metastoma anterior cordate and basally truncated; appendage III bearing multiple enlarged spines; appendage V nonspiniferous; long appendage VI with expanded distal podomere and narrow triangular VI-7a; subrhomboidal coxa of appendage VI with a rounded principal tooth. Malongia nov. gen. is the fourth genus described within the Dolichopteridae Kjellesvig-Waering and Størmer, 1952, other members of which are Dolichopterus Hall, 1859, Clarkeipterus Kjellesvig-Waering, 1966, and Ruedemannipterus Kjellesvig-Waering, 1966; it represents the only record of this family in South China.

The Late Miocene hominid-bearing locality in Haritalyangar, India, has yielded remains of fossil lizards and snakes. The material consists of the following taxa: Varanus and an indeterminate anguimorph, Python, a colubrid and a natricid. These squamates are documented from this region for the first time. A co-existence of Varanus and Python, two iconic squamates, is demonstrated. The overall fauna, which is dominated by both large and small semi-aquatic and terrestrial taxa, indicates seasonally wet sub-humid to semi-arid climate in the area during the Late Miocene, ∼9.1 Ma. Moreover, the mean annual temperature must have been high in the region at that time (not less than 15–18.6 °C, similar to the mean annual temperature in this area today), indicated by the occurrence of important thermophilic elements such as Varanus and Python.

Small mammal remains have been discovered in three new outcrops from the Afoud locality. This site is significant from a paleontological point of view because it has yielded fauna of European affinities (Castillomys, Occitanomys, Stephanomys, Eliomys, and Prolagus). The presence of two different species of Arvicanthis from the Afoud locality represents the oldest record in North Africa. The association of small mammals from the AF12-2 deposits provides an approximate view of the local environment and climate at the time of the formation of this locality. This faunal assemblage indicates a warm, temperate, semi-arid climate and an open vegetation cover of wooded savannah. Fossil assemblages documented in this paper expand our knowledge on the Late Miocene–Early Pliocene small mammal communities of the Aït Kandoula Basin. This study provides useful data for understanding the paleobiogeography of the Mediterranean region and faunal exchanges between North Africa and the Iberian Peninsula that took place before the Messinian Salinity Crisis.

This study deals with the issues around the synonymization of the large extinct giraffid genera Libytherium and Sivatherium. We performed a morphological and biometrical analysis of the cranial remains of these giraffid genera and resolved this question by formulating criteria to distinguish Libytherium from Sivatherium, and to justify their systematic position within the Giraffidae. The present study also reports a new species of the genus Libytherium, Libytherium proton nov. sp. from the Chinji Formation (late Middle Miocene) and the Dhok Pathan Formation (Late Miocene) of the Siwalik Group of the Indian subcontinent. This extends the biogeographic and biostratigraphic range of Libytherium because this taxon had never been reported from the Siwaliks, Asia and the Miocene before this study. This study also initiates a detailed reassessment of the African and Siwalik material currently attributed to genus Sivatherium (and some other genera) and their proper allocation within the Giraffidae.

A diverse but fragmentary assemblage of fossil cetaceans is reported from the Oligocene-Miocene Belgrade Formation of North Carolina. This assemblage preserves many odontocetes including four xenorophids (Albertocetus, Echovenator sp., cf. Cotylocara, and Xenorophus sp.), a possible waipatiid (cf. Waipatiidae), a giant agorophiid-grade dolphin (Ankylorhiza), a shark-toothed dolphin (cf. Squalodon), longirostrine “swordfish” dolphins (Eurhinodelphinidae), a longirostrine eoplatanistid dolphin (cf. Eoplatanista), a longirostrine squalodelphinid dolphin, a possible early delphinidan (Kentriodontidae), as well as an eomysticetid baleen whale (Eomysticetus sp.) and sirenian fragments. Most of these taxa are characteristic of or unique to Oligocene deposits (Xenorophidae, cf. Waipatiidae, Ankylorhiza, Eomysticetus) whereas others are more typical of early or middle Miocene deposits (cf. Eoplatanista, Eurhinodelphinidae, cf. Squalodon, Squalodelphinidae, Kentriodontidae). The Belgrade Formation at Belgrade Quarry is dated to 25.95–21.12 Ma, approximating the Oligocene-Miocene transition. The transitional composition of the Belgrade cetacean assemblage suggests gradual changes between Oligocene to Miocene cetacean faunas, to be verified by the discovery of more complete remains from the poorly sampled earliest Miocene (Aquitanian).

This article presents a description of new antler remains from five fossiliferous sites (Sardhok, Panjan Sher Shahana, Puran, Jari Kas, and Potha) of the Upper Siwaliks in Pakistan. The systematic study of the antler material revealed the presence of six cervid forms: Metacervocerus punjabiensis, Rucervus sp., Panolia sp., Hyelaphus sp., Praesinomegaceros bakri, and a poorly represented large cervid that shows a certain affinity with “Eucladoceros sp.” from the Early Pleistocene of Kuruksai (Tajikistan). The remains of Panolia represent the earliest known paleontological record of this cervid lineage. Unlike Metacervocerus and Rucervus that have had phylogenetically closely related counterparts in east and north of the Alpine-Himalayan mountain belt, the evolution of Panolia took place in the Indian subcontinent. The entry of Panolia lineage into the Indian subcontinent marks its phylogenetic split from the main Cervus/Rusa evolutionary branch. The earliest dispersal events of cervids into the Indian subcontinent was preceded by the late Miocene evolutionary radiation and ecological diversification of the subfamily Cervinae in Southeastern Asia. Praesinomegaceros and Metacervocerus most probably entered the Indian subcontinent via Central Asia. Possibly, this is also the case of “Eucladoceros sp.” from Kuruksai (Tajikistan). The dispersal ways of Panolia and Rucervus remain unclear. The dispersals of small-sized cervids (Muntiacus and Hyelaphus) into the Indian subcontinent was triggered by the establishment of the 100-ky glaciation cycle during the Middle Pleistocene: the sea level dropped during glacial peaks and opened to them the dispersal route from Sundaland in the South.