Cretaceous Freshwater Research Articles

Geochemical study of vertebrate fossils from the Upper Cretaceous (Santonian) Csehbánya Formation (Hungary): Evidence for a freshwater habitat of mosasaurs and pycnodont fish

The diverse vertebrate remains from the Upper Cretaceous freshwater settings at Iharkút, Hungary, contain two fossil groups, Pycnodontiformes fish and Mosasauridae that are almost exclusively known from marine palaeo-environments. Hence, their appearance in alluvial sediments is very unusual. Trace element and isotope compositions of the remains have been analyzed to investigate the taphonomy and the ecological differences among the different fossil groups present at Iharkút. All examined fossils have undergone post-depositional diagenetic alteration, which resulted in high concentrations of REE, U, and Fe, together with almost complete homogenization of δ 18O CO3 values. Similar REE patterns in different fossils suggest a common origin for all remains, hence the discovered species most likely lived in the same local ecosystem. Despite partial diagenetic overprinting, the δ 18O PO4 values of the fossils indicate sufficient taxon-specific isotopic diversity to permit some broad conclusions on the palaeo-environment of the fossils. In particular, it is apparent that the isotopic composition of the Pycnodontiformes fish and Mosasauridae remains is most compatible with a freshwater palaeo-habitat and incompatible with a marine palaeo-environment. In addition, the Sr concentration and isotope data indicate that the Pycnodontiformes and Mosasauridae likely lived predominantly in a freshwater environment and were not simply occasional visitors to the Iharkút river ecosystem. Regarding other fossil groups, high δ 18O PO4 values of Alligatoroidea and Iharkutosuchus teeth suggest that these small crocodile species might have inhabited swamps and ponds where the water was relatively rich in 18O due to evaporation.

The first sinamiid fish (Holostei: Halecomorpha) from Southeast Asia (Early Cretaceous of Thailand)

ABSTRACT †Siamamia naga, gen. et sp. nov, is described on the basis of three partly articulated skulls and a collection of isolated ossifications from a continental Early Cretaceous Formation of northeastern Thailand. The new taxon is a †sinamiid halecomorph as demonstrated by the median parietal and other cranial characters. †Sinamiidae is hitherto known by two genera occurring in Early Cretaceous freshwater deposits in China. Although a complete revision of all species within the family is necessary, the Thai material shows characters justifying a new genus. It is the first †sinamiid found outside eastern Asia (South and North Chinese blocks, plus small Central Asian terranes), thus validating the close paleogeographical affinities between mainland Asia and SE Asia in the Early Cretaceous. A preliminary phylogenetic assessment of the new taxon with the data matrix of Grande and Bemis (1998) with the addition of data for †Siamamia and †Tomognathus provides a strict consensus tree similar to the phylogenetic hypothesis of Halecomorphi proposed by these authors, except the basal-most amiids which show a lower resolution in our hypothesis. The †Sinamiidae appear as a monophyletic clade, but the four taxa included in the analysis form a polytomy.

<i>Eodinia poulseni</i> sp. nov., a dinoflagellate cyst from Middle Jurassic of Central Poland

Abstract. A new species of dinoflagellate, Eodinia poulseni, is described from the Middle Jurassic of Central Poland. Light and scaning electron microscopy shows that this species has a complex cyst wall consisting of autophragm and ectophragm. Eodinia poulseni sp. nov. has similarities to some common Middle Jurassic species, especially when separate hypocysts are observed. Important differences between Eodinia pachytheca, Mosaicodinium mosaicum, Wanaea acollaris, W. cornucavata and Hurlandsia rugarum are discussed. Some phylogenetic and environmental relationships to the Early Cretaceous freshwater species Hurlandsia rugarum are suggested. H. rugarum shows similarity in archaeopyle, overall shape and tabulation formula but is acavate and also distinct from E. poulseni in time.

On Early Cretaceous (earliest Aptian) freshwater Charophyta and Ostracoda from Northern Somalia

On Early Cretaceous (earliest Aptian) freshwater Charophyta and Ostracoda from Northern Somalia

Habitat of the Early Cretaceous non-marine bivalve Nippononaia yanjiensis in northeast China

The Lower Cretaceous Sunjiawan Formation of northeast China consists of non-marine deposits containing abundant Nippononaia yanjiensis Gu. These sedimentary rocks comprise fluvial channel and overbank (levee, crevasse splay, pond and floodplain) accumulations. There are two modes of occurrence of N. yanjiensis. Type 1 is characterized by inferred life positions within the pond deposits, and Type 2 represents poorly preserved fragments and disarticulated valves within the channel deposits. N. yanjiensis was a freshwater mollusc that lived in ponds within abandoned channels in overbank environments. The genus Nippononaia is widely distributed in the Northern Hemisphere, and is a useful indicator of Lower Cretaceous freshwater environments.

A new species of †Notogoneus (Teleostei: Gonorynchidae) from the Upper Cretaceous Two Medicine Formation of Montana, and the poor Cretaceous record of freshwater fishes from North America

ABSTRACT †Notogoneus montanensis, sp. nov. (Teleostei: Ostariophysi: Gonorynchidae) is described from Late Cretaceous freshwater deposits of the Two Medicine Formation of Montana. The species is represented by one articulated skeleton and a partial trunk region of a second individual. Articulated freshwater fish fossils are almost unknown in Early Cretaceous through Middle Paleocene age deposits of North America. Localities such as the Two Medicine fish locality are extremely important to a better understanding of the biodiversity of early North American freshwater teleosts. †Notogoneus montanensis, sp. nov. is the earliest known occurrence of the genus †Notogoneus, and it is the earliest known freshwater gonorynchiform from North America. The distribution of †Notogoneus and other gonorynchid species is briefly reviewed. Additional fragmentary fish fossils found associated with †N. montanensis, sp. nov. include a number of teleost scales, which appear to belong to at least two different taxa other than †Notogoneus.

First isotopic and multidisciplinary evidence for nonmarine coelacanths and pycnodontiform fishes: palaeoenvironmental implications

The Recent coelacanth Latimeria chalumnae, one of the best known `living fossils', dwells in deep marine water. Fossil coelacanths have been globally related to marine environments, specially after the Triassic, an association that has led to a general belief that they have always been marine. Previous reports of fossil coelacanths in continental deposits have been largely neglected. Prior to this report, uncontested Cretaceous freshwater coelacanths were unknown. In turn, the pycnodontiform fishes have always been considered exclusively marine, apart from a few controversial exceptions. Here we present the first multidisciplinary evidence for nonmarine coelacanths and pycnodonts. Our conclusions are based upon palaeogeographic, sedimentologic, taphonomic, and palaeoecologic criteria, strongly supported by strontium ( 87Sr– 86Sr) and stable carbon and oxygen isotopic studies. The coelacanth, provisionally attributed to the genus ` Holophagus', and the pycnodontiforms Eomesodon sp. and Macromesodon aff. bernissartensis were unearthed at the Early Cretaceous locality of Las Hoyas (Cuenca, Spain), where they grew in and inhabited a freshwater environment without marine influence. Fossil coelacanths and pycnodonts cannot, therefore, be used as unambiguous indicators of a marine environment. Caution is needed when using a single or a few taxa as palaeoenvironmental indicators, especially fish; in this sense, communities are much more reliable. Arguments based on actualism or taxonomic uniformitarianism, morphologic convergence and functional morphology are truly significant only within the framework of a sound multidisciplinary approach to the study of the palaeoenvironment.

A Comprehensive Phylogenetic Study of Amiid Fishes (Amiidae) Based on Comparative Skeletal Anatomy. an Empirical Search for Interconnected Patterns of Natural History

ABSTRACT The comparative osteology, phylogenetic relationships, and historical biogeography of all known taxa of fossil and living amiid fishes (Halecomorphi: Amiidae) are investigated in detail. Previously, the detailed osteology of nearly all fossil amiids was unknown. We present the first well-supported comprehensive phylogeny for fossil and living amiid fishes. We synthesize clearly documented phylogenetic data on amiids and other halecomorph fishes with other historical phenomena such as ontogeny, historical biogeography, stratigraphic paleontology, and paleoecology (both “stationary” and “historical”). We also use our study of halecomorph fishes as a platform to explore several fundamental methodological and theoretical concepts important to phylogenetic/evolutionary investigations. These concepts pertain mainly to (1) the use of comparative empirical data to interpret various historical patterns and (2) the practice of integrating fossil and living species together in original (i.e., non-literature...

The evolution and distribution of normapolles pollen during the cenophytic

Long-term palaeopalynological studies of the Upper Cretaceous freshwater and marine sediments of the Bohemian Massif and of other European areas have yielded the following results. The first recorded Normapolles pollen are of middle Cenomanian Age and are associated with the first triporate forms; thus, the Normapolles did not necessarily arise from the triporates. Changes in both the vegetation and pollen morphology that occurred at this time were in response to changing palaeoecological, palaeogeographical and palaeoclimatological conditions. The discovery of Normapolles on the Indian subcontinent changes the hitherto maintained views on the phytogeographic distribution of the Normapolles, and suggests that their geographic occurrences might be significant with respect to plate tectonic reconstructions. In Europe there are differences between the Upper Cretaceous palynospectra of the Mediterranean and boreal areas, with the Upper Cretaceous sediments of the South Bohemian basins representing a transitional flora. The progressive evolution of the Normapolles group has provided a basis for the biostratigraphic subdivision of the Upper Cretaceous. Without the Normapolles we would have no idea of the explosive evolution of flowering plants during this period.

GEOCHEMISTRY AND SIGNIFICANCE OF COASTAL BITUMEN FROM SOUTHERN AND NORTHERN AUSTRALIA

Detailed geochemical analysis of eleven Australian coastal bitumens - eight from ocean beaches in South Australia and western Victoria, and three from stranding sites on Bathurst Island and Cobourg Peninsula in the Northern Territory - shows that they are inspissated waxy crudes of low API gravity and low sulphur content.Only one bitumen appears not to be a natural crude, its composition is that of a weathered fuel oil. The rest may be divided into two types, as follows:Bitumens from Ocean Beach, Geltwood Beach and Sleaford Bay in South Australia are paraffinic to naphthenic in composition. Those from the Northern Territory, Victoria and Cape Northumberland, SA, together with a second sample from Geltwood Beach, are highly paraffinic to paraffinic. Both types of bitumen strand at Geltwood Beach where each contains appreciably more nickel (85-105 ppm) than bitumens of either type found elsewhere (3-30 ppm).The effects of exposure are more evident in some bitumens than in others. Weathering has involved evaporative loss of volatile components, bacterial degradation of n-alkanes up to C25, and an increase in asphaltenes at the expense of saturated hydrocarbons.A high proportion of long-chain (C23+) n-alkanes in the stranded crudes indicates that they are products of the diagenesis of mostly continental vegetation. However, their low pristane/phytane ratios (The geochemistry of the bitumens supports the belief that they represent natural submarine seepages. The amount of weathering sustained by the bitumens in each suite correlates with their exposure time. Their degree of alteration, in conjunction with a knowledge of local surface currents, can be used to establish their provenance. Cretaceous freshwater and paralic sediments are present at depth offshore in both the western Otway Basin and the Money Shoal Basin. These sediments constitute the most likely ultimate source for the immature oils that gave rise to the coastal bitumens now found scattered along the southern and northern coastlines of Australia.