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Showing results for tags 'middle cretaceous'.
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Silver Iridescent Ammonite Fossils Mahajanga Province, Madagascar TIME PERIOD: Middle Cretaceous (110 million years ago) Data: Ammonoids are an extinct group of marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs are more closely related to living coleoids (i.e., octopuses, squid, and cuttlefish) than they are to shelled nautiloids such as the living Nautilus species. The earliest ammonites appear during the Devonian, and the last species died out during the Cretaceous–Paleogene extinction event. Ammonites are excellent index fossils, and it is often possible to link the rock layer in which a particular species or genus is found to specific geologic time periods. Their fossil shells usually take the form of planispirals, although there were some helically spiraled and nonspiraled forms (known as heteromorphs). The name "ammonite", from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble tightly coiled rams' horns. Pliny the Elder (d. 79 AD near Pompeii) called fossils of these animals ammonis cornua ("horns of Ammon") because the Egyptian god Ammon (Amun) was typically depicted wearing ram's horns. Often the name of an ammonite genus ends in -ceras, which is Greek for "horn". Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Order: Ammonitida
You should read these papers. They are very interesting: Carvalho, I.; Novas, F.E.; Agnolín, F.L.; Isasi, M.P.; Freitas, F.I.; Andrade, J.A.. (2015). "A new genus and species of enantiornithine bird from the Early Cretaceous of Brazil". Brazilian Journal of Geology 45 (2): 161–171. DOI:10.1590/23174889201500020001. Carvalho, I.; Novas, F.E.; Agnolín, F.L.; Isasi, M.P.; Freitas, F.I.; Andrade, J.A.. (2015). "A Mesozoic bird from Gondwana preserving feathers". Nature Communications 6. DOI:10.1038/ncomms8141. The discovery of Cratoavis in Brazil is remarkable because nearly all Early to Middle Cretaceous birds have been found in Laurasia (Nanantius is the only other pre-Santonian bird found in Gondwana). It'd be interesting to see if there might be any Early and Middle Cretaceous birds from North Africa and the rest of South America because we now know that the multitude of Early Cretaceous bird fossils in China was due to a Mesozoic version of Pompeii.
An interesting article about a new sauropod from Tanzania: http://phys.org/news/2014-09-species-titanosaurian-dinosaur-tanzania.html The discovery of a titanosaur from the Middle Cretaceous deposits in Tanzania is significant in many respects. First, it represents the third diagnostic titanosaur from Cretaceous sediments in sub-Saharan Africa. Second, it bolsters the hypothesis by Paul Sereno and colleagues that the breakup of Gondwana was a rather gradual one, so a number of titanosaurs known from South America may also have inhabited sub-Saharan Africa at a time when South America was slowly breaking away from Africa (the basal somphospondylian Angolatitan is of late Turonian age and also from sub-Saharan Africa, so it's not unreasonable to imagine titanosaurs populating South America and Africa in the Cenomanian and Turonian). Third, Rukwatitan is the first middle Cretaceous dinosaur from the Africa's Great Rift Valley. The non-titanosaur somphospondyl Wintonotitan and the lithostrotian Diamantinasaurus from Australia are of about the same age as Rukwatitan, so it's not implausible that some titanosaurs made it to Australia by immigrating to Africa, and then indirectly to Australia via Antarctica. With Rukwatitan, we are just beginning to appreciate the diversity of middle Cretaceous Gondwanan titanosaurs outside South America.
DD1991 posted a topic in EuropeA forthcoming paper on the largest specimen of Dakosaurus from the UK (Young et al. in press) mentions a number of Dakosaurus specimens found in the Woburn Sands Formation, which leads me to suspect that a number of loose Lower Greensand sediments in SE england may have specimens reworked from Late Jurassic sediments. Are there any other Cretaceous sediments in England that have yielded fossils reworked from Jurassic sediments? Young MT, Steel L, Rigby MP, Howlett EA, Humphrey S. (In press). Largest known specimen of the genus Dakosaurus (Metriorhynchidae: Geosaurini) from the Kimmeridge Clay Formation (Late Jurassic) of England, and an overview of Dakosaurus specimens discovered from this formation (including reworked specimens from the Woburn Sands Formation). Historical Biology.