Vertebrate microremains from the Early Cretaceous of southern Tunisia

Microremains of various sharks, actinopterygians and crocodiles have been recovered from two sites in the Douiret Formation and three sites in the Aïn el Guettar Formation in southern Tunisia. The presence of an actinistian is also suggested based on histological study of hemisegments of lepidotrichia. Convergence in dental enameloid microstructure between neoselachian sharks and actinopterygians sharing a tearing dentition is also documented. The vertebrate assemblage of the Douiret Formation suggests a pre-Aptian age for this formation and the presence of Bernissartia in the Aïn el Guettar Formation confirms faunal exchange between Africa and Europa during the Early Cretaceous.     

Paleoenvironmental reconstruction of an Albian plant community from the Ariño bonebed layer (Iberian Chain,NE Spain)

The AR-1 layer, corresponding to the Escucha Formation (Lower Cretaceous) in the Santa Maria Mine of Ariño, has supplied rich and well-preserved macrofloral and palynological assemblages showing interesting data about both taphonomic and environmental conditions. This single layer is located in the Oliete Sub-Basin from the Maestrazgo Basin in northeastern Spain, and it represents one of the most outstanding single layer fossil sites in the world. This site shows abundant and diverse fauna containing exquisitely preserved vertebrate and invertebrate fossils (dinosaur bones, turtles, crocodiles, fishes, molluscs and ostracods) and also plant remains of Albian age. The assemblage is especially significant for dinosaur phylogenetic analysis. The sedimentary environment corresponds to a freshwater swamp plain with sporadic marine inputs within a deltaic–estuarine system under subtropical–tropical climate.     

A new crocodylomorph tooth assemblage from the Tataouine Basin and comments on the stratigraphic context of the Douiret Formation

A new crocodylomorph tooth assemblage from the Lower Member of the Douiret Formation (uppermost Jurassic–lowermost Cretaceous) in southeastern Tunisia is described. These teeth have been grouped into five morphotypes based on their diagnostic morphological features. The sample includes teeth, which have not been reported until now, such as non-Machimosaurini teleosauroid teeth, and labiolingually compressed tooth crowns with cutting edges devoid of serrations. Certain minor morphometric differences have been interpreted as ontogenetic or being possibly related to the position of the teeth in the jaws. Three trophic entities have subsequently been defined on the basis of the morphological characteristics of the teeth, and a possible niche partitioning between at least three crocodylomorph taxa is highlighted for the first time in the Tataouine Basin. On the other hand, the stratigraphic context of the Douiret Formation is thoroughly discussed in order to show how stratigraphic uncertainties could significantly impact previous attempts at reconstructing the macroevolutionary history of Crocodylomorpha. The latter should be treated with caution when the stratigraphic context of the fossil bearing formation remains a subject of debate.     

Depositional environments and facies development of the Cenomanian–Turonian Galala and Maghra el Hadida formations of the Southern Galala Plateau (Upper Cretaceous,Eastern Desert,Egypt)

The Cenomanian–Turonian (Upper Cretaceous) Galala and Maghra el Hadida formations of the Southern Galala Plateau in Wadi Araba (northern Eastern Desert, Egypt) represent marine depositional systems developing in response to the early Late Cretaceous transgression at the southern margin of the Neotethyan Ocean in tropical paleolatitudes. A facies analysis (litho-, bio- and microfacies) of these successions shows the presence of 22 facies types (FTs, six are related to the Galala Formation, while the Maghra el Hadida Formation is represented by 16 FTs). The Galala Formation was deposited in a fully marine lagoonal environment developing in response to a latest Middle to early Late Cenomanian transgression. The rich suspension- and deposit-feeding macrobenthos of the Galala Formation indicate meso- to eutrophic (i.e., green water) conditions. The facies types of the uppermost Cenomanian–Turonian Maghra el Hadida Formation suggest deposition on a homoclinal carbonate ramp with sub-environments ranging from deep-subtidal basin to intertidal back-ramp. Major and rapid shifts in depositional environments, related to (relative) sea-level changes, occurred in the mid-Late Cenomanian, the Early–Middle Turonian boundary interval, the middle part of the Middle Turonian and the Middle–Late Turonian boundary interval.     

High Diversity in Cretaceous Ichthyosaurs from Europe Prior to Their Extinction

Background

Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group declining since the Jurassic. Recently, however, an unexpected diversity has been described in Upper Jurassic–Lower Cretaceous deposits, but is widely spread across time and space, giving small clues on the adaptive potential and ecosystem control of the last ichthyosaurs. The famous but little studied English Gault Formation and ‘greensands’ deposits (the Upper Greensand Formation and the Cambridge Greensand Member of the Lower Chalk Formation) offer an unprecedented opportunity to investigate this topic, containing thousands of ichthyosaur remains spanning the Early–Late Cretaceous boundary.

Methodology/Principal Findings

To assess the diversity of the ichthyosaur assemblage from these sedimentary bodies, we recognized morphotypes within each type of bones. We grouped these morphotypes together, when possible, by using articulated specimens from the same formations and from new localities in the Vocontian Basin (France); a revised taxonomic scheme is proposed. We recognize the following taxa in the ‘greensands’: the platypterygiines ‘Platypterygius’ sp. and Sisteronia seeleyi gen. et sp. nov., indeterminate ophthalmosaurines and the rare incertae sedis Cetarthrosaurus walkeri. The taxonomic diversity of late Albian ichthyosaurs now matches that of older, well-known intervals such as the Toarcian or the Tithonian. Contrasting tooth shapes and wear patterns suggest that these ichthyosaurs colonized three distinct feeding guilds, despite the presence of numerous plesiosaur taxa.

Conclusion/Significance

Western Europe was a diversity hot-spot for ichthyosaurs a few million years prior to their final extinction. By contrast, the low diversity in Australia and U.S.A. suggests strong geographical disparities in the diversity pattern of Albian–early Cenomanian ichthyosaurs. This provides a whole new context to investigate the extinction of these successful marine reptiles, at the end of the Cenomanian.     

甘肃平凉安国镇白垩系六盘山群的孢粉植物群

对甘肃—宁夏交界处六盘山群一个露头剖面进行了孢粉分析,从和尚铺组、李洼峡组、马东山组和乃家河组中获得了孢粉化石。这些材料表明,六盘山群的孢粉植物群中白垩纪分子丰度高、分异度大,时代可能为晚Aptian—早、中Albian。孢粉反映当时的气候条件中性偏干,其中和尚铺组和乃家河组比李洼峡组和马东山组要更干一些。根据孢粉资料,六盘山群的和尚铺组至乃家河组的沉积可与盆地主体的志丹群的上部即泾川组对比,三桥组则可能相当于罗汉洞组。陕甘宁盆地西部边缘区缺少相当于志丹群宜君组至环河华池组的早白垩世早期的沉积。     

Dinosaur footprints from the Phra Wihan Formation (Early Cretaceous of Thailand)

The ichnological assemblage of the Phra Wihan Formation (early Early Cretaceous of northeastern Thailand) includes the first sauropod tracks ever found in Thailand. It is reminiscent of the fauna of the underlying Jurassic Phu Kradung Formation with theropods, small ornithischians of uncertain affinities (possibly Hypsilophodon-like ornithopods) and sauropods. It suggests that, in southeastern Asia, an important faunal change occurred in the Early Cretaceous among continental vertebrates, whereas little happened at the Jurassic–Cretaceous boundary.     

Early Cretaceous stratigraphy and SHRIMP U‐Pb age constrain the Valanginian–Hauterivian boundary in southern Tibet

Wan, X., Scott, R., Chen, W., Gao, L. & Zhang, Y. 2011: Early Cretaceous stratigraphy and SHRIMP U‐Pb age constrain the Valanginian–Hauterivian boundary in southern Tibet. Lethaia, Vol. 44, pp. 231–244. The Late Jurassic to the Early Cretaceous marine strata are extensively distributed in southern Tibet. In Gyangze, the strata are divided into the Weimei and Jiabula formations. In Nagarze, they are divided into the Weimei and Sangxiu formations. Previous work has reported diverse ammonite species of Haplophylloceras and Himalayites in the Weimei Formation, and a few species of Spiticeras in the lower Jiabula and Sangxiu formations. The present study has found the bivalve Inoceramus and nannofossil assemblages in the lower Jiabula and Sangxiu formations. The nannofossil assemblage of Nannoconus steimannii steinmannii, N. steinmannii minor and Watznaueria barnesae indicates Berriasian age, and the Calcicalathina oblongata–Speetonia colligata assemblage is Valanginian in age. Numerical ages for the Jiabula and Jiabula‐goukou sections in Gyangze have been interpolated by comparing the fossil ranges with ages calibrated in other sections. The correlation experiment plots fossil ranges in the two sections to the CRET1 Database. The estimated rate of sediment accumulation of the lower Sangxiu Formation is 22.6 m/myr. The Jurassic–Cretaceous (J/K) boundary is at the bottom of the Jiabula Formation in Gyangze, and the base of the Sangxiu Formation in Nagarze. The boundary is marked by the appearance of the ammonite Spiticeras and the nannofossil assemblage of Nannoconus st. steinmannii–N. st. minor–Watznaueria barnesae. The radiometric age in Tibet is the first to be integrated with upper Valanginian fossils. The volcanic rocks of the upper Sangxiu Formation are dated at 136 ± 3.0 Ma deduced from zircon SHRIMP age of rhyolite. By consideration of the rate of sediment accumulation of the underlying sedimentary deposits, the J/K boundary in the Gyangze–Nagarze area is approximately 145 Ma as suggested by the newly issued International Stratigraphic Chart, and the Valanginian/Hauterivian boundary lies between 134 Ma and 136 Ma. □ Biostratigraphy, graphic plot, Jurassic/Cretaceous boundary, nannofossil, SHRIMP U‐Pb age, Southern Tibet, Valanginian/Hauterivian boundary.     

粤西怀集盆地白垩系马屋组的介形类化石

依据闸岗剖面地表及钻井样品的分析鉴定,粤西怀集盆地白垩纪闸岗群马屋组产介形类化石10属17种,本文描述其中9属14种,包括1新种。介形类组合以Eucypris最繁盛,次为Ziziphocypris和Darwinula,称Eucypris hubeiensis-Ziziphocypris simakovi-Darwinula leguminella组合。马屋组与湖北贾店组的介形类组合面貌非常相似,可以进行对比,层位大体相当,其时代应属早白垩世最晚期(Albian)-晚白垩世早期(Cenomanian)。     

辽西早白垩世义县组Ruffordia和Nageiopsis的发现及其地层意义

报道辽西义县组两种颇具地层意义的植物化石。Ruffordia goeppertii(Dunker)Seward和Nageiopsis exgr.samioides(Fontaine)berry,根据植物化石认为义县组的时代应属于早白垩世。     

Low ecological disparity in Early Cretaceous birds

Ecological divergence is thought to be coupled with evolutionary radiations, yet the strength of this coupling is unclear. When birds diversified ecologically has received much less attention than their hotly debated crown divergence time. Here, we quantify how accurately skeletal morphology can predict ecology in living and extinct birds, and show that the earliest known assemblage of birds (= pygostylians) from the Jehol Biota (≈ 125 Ma) was substantially impoverished ecologically. The Jehol avifauna has few representatives of highly preservable ecomorphs (e.g. aquatic forms) and a notable lack of ecomorphological overlap with the pterosaur assemblage (e.g. no large or aerially foraging pygostylians). Comparisons of the Jehol functional diversity with modern and subfossil avian assemblages show that taphonomic bias alone cannot explain the ecomorphological impoverishment. However, evolutionary simulations suggest that the constrained ecological diversity of the Early Cretaceous pygostylians is consistent with what is expected from a relatively young radiation. Regardless of the proximate biological explanation, the anomalously low functional diversity of the Jehol birds is evidence both for ecological vacancies in Cretaceous ecosystems, which were subsequently filled by the radiation of crown Aves, and for discordance between taxonomic richness and ecological diversity in the best-known Mesozoic ecosystem.     

藏南江孜地区古近纪甲查拉组孢粉组合及古环境分析

甲查拉组位于藏南特提斯喜马拉雅北带的江孜盆地,是江孜地区的最高海相地层,被视为新特提斯洋关闭时代的主要证据。通过对甲查拉组剖面的孢粉分析,自下而上划分为3个孢粉组合带:1 Ulmipollenites minor+Ulmoideipites-Myricipites组合带;2 Quercoidites-Caryapollenites组合带;3 Abiespollenites-Betulaceoipollenites+Betulaepollenites组合带。甲查拉组孢粉植物群揭示出其沉积自晚古新世开始,其沉积结束可能延续到早渐新世。推测晚古新世—早始新世为温暖湿润的暖温带或亚热带气候,始新世中晚期为温暖、潮湿的亚热带气候,早渐新世为温和湿润的暖温带气候。     

内蒙古海拉尔盆地白垩纪生物地层研究进展

兴安岭群龙江组产Ephemeropsistrisetalis等热河生物群分子,九峰山组产富含Cicatricosisporites,Pilosisporites,Concavissimisporites的孢粉组合,兴安岭群龙江组、甘河组火山岩同位素年龄为105-141Ma,证实兴安岭群的时代为早白垩世早期;扎赉诺尔群中以Cypridea,Limnocypridea,Ilyocyprimorpha和Hailaeria等属为代表的介形类动物群,以Nyktericysta,Vesperopsis等属为代表的NV浮游植物群,以富含Lygopodiaceae科各属孢子,尤其是Cicatricosisporites高含量的孢粉组合,代表了中国北方早白垩世特有的动、植物群面貌,而其中Asteropollis,Tricolpites和Polyporites等被子植物花粉化石的发现,这一事实似乎暗示了扎赉诺尔群的时代为早白垩世中、晚期;青元岗组产以Talicypridea,Altanicypris,Chinocypridea和Harbinia为代表的介形类动物群,具有显著的地域性特点,可与松辽盆地四方台组对比,其时代为晚白垩世Maastrichtian期。     

New mammal remains from the Late Cretaceous Bostobe Formation (Northeast Aral Sea Region,Kazakhstan)

Four recently collected mammal specimens from the Upper Cretaceous (Santonian–?Campanian) Bostobe Formation in the northeastern Aral Sea Region, Kazakhstan are attributed to Asioryctitheria indet. (an edentulous dentary fragment) and the zhelestid Parazhelestes sp. cf. P. mynbulakensis (a maxillary fragment with a double-rooted canine, an M1, and a dentary fragment including m3). These new records double the known mammal fauna from this formation, which previously included the zhelestid Zhalmouzia bazhanovi and Zhelestidae indet. The taxonomic and ecological structure of the mammal assemblage from the Bostobe Formation can, on present evidence, be considered close to the other eutherian dominated Late Cretaceous mammal assemblages of Central Asia. This region is important in particular in the search for Late Cretaceous ancestors of crown-group eutherian mammal clades (Placentalia).     

The context of Stw 573, an early hominid skull and skeleton from Sterkfontein Member 2: taphonomy and paleoenvironment

The reconstructed taphonomic and paleoenvironmental contexts of a ca. 4 million-year-old partial hominid skeleton (Stw 573) from Sterkfontein Member 2 are described through presentation of the results of our analyses of the mammalian faunal assemblage associated stratigraphically with the hominid. The assemblage is dominated by cercopithecoids (Parapapio and Papio) and felids (Panthera pardus, P. leo, Felis caracal, and Felidae indet.), based on number of identified specimens, minimum number of elements and, minimum number of individuals. In addition, the assemblage is characterized by a number of partial skeletons and/or antimeric sets of bones across all taxonomic groups. There is scant indication of carnivore chewing in the assemblage. These observations, in addition to other taphonomic data, suggest that the remains of many animals recovered in Member 2 are from individuals that entered the cave on their own-whether accidentally by falling through avens connecting the cave to the ground surface above or by intentional entry-and were then unable to escape, rather than primarily through systematic collection by a biotic, bone-accumulating agent. The taphonomic conclusion that animals with climbing proclivities (i.e., primates and carnivores) are preferentially preserved over other taxa, ultimately because of those proclivities, urges caution in assessing the fidelity of the assemblage for reconstruction of the Member 2 paleoenvironment. With that caveat, we infer that the Member 2 paleoenvironment was typified by rolling, rock-littered and brush- and scrub-covered hills, indicated by the abundant F. caracal and cercopithecoid fossils recovered and the identified presence of the extinct Caprinae Makapania broomi. In addition, the valley bottom may have retained standing water year-round, perhaps supporting some tree cover--a setting suitable for the well-represented ambush predator P. pardus and suggested by the presence of Alcelaphini. Finally, the reconstructed taphonomic and paleoenvironmental settings of Sterkfontein Member 2 are compared to penecontemporaneous sites in South and East Africa.     

Taphonomic analysis of the Middle Stone Age faunal assemblage from Pinnacle Point Cave 13B, Western Cape, South Africa

A detailed taphonomic analysis is provided for the mammalian and tortoise faunal assemblages from Pinnacle Point Cave 13B (PP13B). It is the first of several reports on the fauna from this site, and must necessarily precede analyses focused on higher level interpretations of Middle Stone Age (MSA) butchery, transport, and hunting behavior. The taphonomic work shows that the faunal assemblage is well preserved and there are discernable differences in the taphonomic pathways to which the fauna was subjected at PP13B between the Middle and Late Pleistocene, between the front and back of the cave, and between body size classes. The largest mammals (size classes 2-5, body weight >24?kg) were mainly accumulated by MSA hominins. Size class 1 ungulates also exhibit a degree of hominin modification consistent with some hominin accumulation of fresh carcasses, but this is more variable through time and includes an observable degree of independent carnivore contribution. Basic taxonomic comparisons reveal a low representation of small mammals, tortoises, and marine mammals at PP13B relative to larger (>4.5?kg) terrestrial mammals. This is a different pattern from other MSA sites along the southwestern coast of South Africa, where small mammals and tortoises are abundant. A microscopic study of the bone surfaces confirms that MSA hominins exploited these small faunal components opportunistically, while focusing most heavily on large terrestrial ungulates. All faunal components show evidence of carnivore scavenging of hominin food debris and a high degree of density mediated destruction. Raptors are at no point implicated as major accumulators of any fauna. The study demonstrates that the full spectrum of MSA faunal exploitation can only be understood when the large mammal, small mammal, and tortoise components of fossil assemblages have all been subjected to comprehensive taphonomic analyses.     

Cretaceous small scavengers: feeding traces in tetrapod bones from Patagonia, Argentina

Ecological relationships among fossil vertebrate groups are interpreted based on evidence of modification features and paleopathologies on fossil bones. Here we describe an ichnological assemblage composed of trace fossils on reptile bones, mainly sphenodontids, crocodyliforms and maniraptoran theropods. They all come from La Buitrera, an early Late Cretaceous locality in the Candeleros Formation of northwestern Patagonia, Argentina. This locality is significant because of the abundance of small to medium-sized vertebrates. The abundant ichnological record includes traces on bones, most of them attributable to tetrapods. These latter traces include tooth marks that provde evidence of feeding activities made during the sub-aerial exposure of tetrapod carcasses. Other traces are attributable to arthropods or roots. The totality of evidence provides an uncommon insight into paleoecological aspects of a Late Cretaceous southern ecosystem.     

The living and the dead: How do taphonomic processes modify relative abundance and skeletal completeness of freshwater fish?

This study is designed to determine the extent to which taphonomic processes alter the taxonomic composition of fish remains in lacustrine sediments. We wish to explore information loss in a bone assemblage relative to the original, living community. We examined fish bone assemblages from lacustrine sediments along the southern shore of Lake Kinneret (Sea of Galilee) and compared them to modern living communities. For this purpose we randomly selected 24 squares, each 0.5 m² in size, and excavated them to a depth of 30–50 cm. Three lithofacies were recovered, spanning the past 1500 years (unccorected for reservoir age). The fish remains include 5037 bones and 758 scales, of which 1566 bones were identified to taxonomic group. The list of identified species was compared with the list of indigenous species known to live in Lake Kinneret in general and in a similar sandy habitat in particular. The proportion of skeletal elements found was compared with the proportion known in a complete fish. Our study indicates that differences exist between the three lithofacies in species diversity and composition, skeletal element richness, completeness, and relative abundance. In addition, the bones exhibit a clumped distribution pattern, regardless of depositional depth. From a taphonomic and paleoecological perspective, our findings demonstrate that fish remains retrieved from lacustrine sediments do not represent the composition and diversity of species as in the recent fish community.     

Taphonomic analysis of the early Pleistocene (2.4 Ma) faunal assemblage from A.L. 894 (Hadar, Ethiopia)

The A.L. 894 site (Hadar, Ethiopia) is, together with OGS 7 (Gona, Ethiopia), one of the oldest archaeological sites documenting a spatial association of stone tools and bones retrieved from an in situ excavation. In contrast with OGS 7, the better preservation of the bone assemblage at A.L. 894 allows the identification of taphonomic processes of bone breakage, thanks to abundant green bone fractures. The presence of tooth marks and the lack of hominin-produced bone modifications together argue against hominins as the responsible agents for bone accumulation and modification. This taphonomic study of A.L. 894 shows lack of evidence for functional associations between stone tools and bones, a pattern documented in several other early Pleistocene sites. Such a pattern underscores the complex phenomena involved in site formation processes, especially in the earliest archaeological assemblages     

Upper Ordovician microphytoplankton of the Bill's Creek Shale and Stonington Formation,Upper Peninsula of Michigan,U.S.A.: Biostratigraphy and paleogeographic significance

An abundant, diverse, and well-preserved organic-walled microphytoplankton assemblage is described from the Upper Ordovician Bill's Creek Shale and the lower Stonington Formation (Bay de Noc Member) in the Upper Peninsula of Michigan, U.S.A. Based on graptolite and conodont evidence, the Bill's Creek Shale and Stonington Formation are Richmondian (=Ashgill) in age. The assemblage is dominated by acritarchs, which comprise 29 species (including the enigmatic palynomorph Gloeocapsomorpha prisca) assigned to 20 genera. The prasinophyte phycomata are represented by undifferentiated species of Leiosphaeridia and Tasmanites. In addition, chitinozoans are abundant, and scolecodonts and graptolite fragments are common. Paleontologic-palynologic and sedimentologic evidence indicates that the Bill's Creek Shale was deposited in a low-energy, shallow, nearshore marine environment. The overlying Bay de Noc Member of the Stonington Formation also accumulated in a low-energy, normal marine environment, but in a more offshore, somewhat deeper water setting. Both formations experienced minor transgressive and regressive episodes as indicated by fluctuations in the composition of the palynoflora. The combined Bill's Creek/Stonington acritarch assemblage closely resembles those described from the Richmondian-aged Maquoketa Shale (Missouri and Kansas), Sylvan Shale (Oklahoma), and Vauréal Formation (Anticosti Island, Québec, Canada). The overall composition of the acritarch assemblage from these four formations reflects a distinctive, recognizably Laurentian character. Nonetheless, many of the Bill's Creek/Stonington acritarchs have been reported from Upper Ordovician localities elsewhere, providing additional evidence for Late Ordovician cosmopolitanism of the marine microphytoplankton community. Additionally, the restricted stratigraphic range of many of the taxa further enhances their biostratigraphic application, both regionally and globally, and reaffirms the Richmondian (=Ashgill) age of the Bill's Creek Shale and Stonington Formation.