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[dinosaur] Cedar Mountain Formation microvertebrates + avian microchromosomes + mosasaur coprolites (free pdfs)

Ben Creisler

Recent non-dino papers with free pdfs:

Haviv M. Avrahami, Terry A. Gates, Andrew B. Heckert, Peter J. Makovicky & Lindsay E. Zanno (2018)
A new microvertebrate assemblage from the Mussentuchit Member, Cedar Mountain Formation: insights into the paleobiodiversity and paleobiogeography of early Late Cretaceous ecosystems in western North America.Â
PeerJ 6:e5883

The vertebrate fauna of the Late Cretaceous Mussentuchit Member of the Cedar Mountain Formation has been studied for nearly three decades, yet the fossil-rich unit continues to produce new information about life in western North America approximately 97 million years ago. Here we report on the composition of the Cliffs of Insanity (COI) microvertebrate locality, a newly sampled site containing perhaps one of the densest concentrations of microvertebrate fossils yet discovered in the Mussentuchit Member. The COI locality preserves osteichthyan, lissamphibian, testudinatan, mesoeucrocodylian, dinosaurian, metatherian, and trace fossil remains and is among the most taxonomically rich microvertebrate localities in the Mussentuchit Member. To better refine taxonomic identifications of isolated theropod dinosaur teeth, we used quantitative analyses of taxonomically comprehensive databases of theropod tooth measurements, adding new data on theropod tooth morphodiversity in this poorly understood interval. We further provide the first descriptions of tyrannosauroid premaxillary teeth and document the earliest North American record of adocid remains, extending the appearance of this ancestrally Asian clade by 5 million years in western North America and supporting studies of pre-Cenomaninan Laurasian faunal exchange across Beringia. The overabundance of mesoeucrocodylian remains at the COI locality produces a comparatively low measure of relative biodiversity when compared to other microvertebrate sites in the Mussentuchit Member using both raw and subsampling methods. Much more microvertebrate research is necessary to understand the roles of changing ecology and taphonomy that may be linked to transgression of the Western Interior Seaway or microhabitat variation.


Rebecca E. OâConnor, Lucas Kiazim, Ben Skinner, Gothami Fonseka, Sunitha Joseph, Rebecca Jennings, Denis M. Larkin & Darren K. Griffin (2018)
Patterns of microchromosome organization remain highly conserved throughout avian evolution.
Chromosoma (advance online publication)
Free pdf:

The structure and organization of a species genome at a karyotypic level, and in interphase nuclei, have broad functional significance. Although regular sized chromosomes are studied extensively in this regard, microchromosomes, which are present in many terrestrial vertebrates, remain poorly explored. Birds have more cytologically indistinguishable microchromosomes (~â30 pairs) than other vertebrates; however, the degree to which genome organization patterns at a karyotypic and interphase level differ between species is unknown. In species where microchromosomes have fused to other chromosomes, they retain genomic features such as gene density and GC content; however, the extent to which they retain a central nuclear position has not been investigated. In studying 22 avian species from 10 orders, we established that, other than in species where microchromosomal fusion is obvious (Falconiformes and Psittaciformes), there was no evidence of microchromosomal rearrangement, suggesting an evolutionarily stable avian genome (karyotypic) organization. Moreover, in species where microchromosomal fusion has occurred, they retain a central nuclear location, suggesting that the nuclear position of microchromosomes is a function of their genomic features rather than their physical size.


Adrian P. Hunt and Spencer G. Lucas (2018)
Mosasaur coprolites from the Bearpaw Formation (Upper Cretaceous) of Saskatchewan, Canada
in Lucas, S.G. and Sullivan, R.M., eds., 2018. Fossil Record 6. New Mexico Museum of Natural History and Science 79: 271-275

Coprolites of marine reptiles were first described in the early nineteenth century. During the 1980s, coprolites were found in the Bearpaw Formation (Upper Cretaceous; upper Campanian) in southern Saskatchewan. Beechybromus wellschi igen. et isp. nov. is a coprolite that is elongate and sub-cylindrical with rounded cross section and is composed of up to 12 discoidal segments; the posterior termination is rounded, and the anterior consists of a triangular apex. It most probably pertains to a mosasaur. A partial specimen from Kansas may pertain to this ichnogenus. Segmented coprolites are typical of mosasaurs


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