Ben Creisler
New papers:
Ricardo N.Melchor, David L.Rivarola, Aldo MartÃn Umazano, Magdalena NalÃn Moyano & FÃtima R. Mendoza Belmontes (2019)
Elusive Cretaceous Gondwanan theropods: the footprint evidence from central Argentina.
Cretaceous Research (advance online publication)
Highlights
Description and interpretation of Albian theropod footprints from central Argentina.
The footprints occur in sheetflood deposits fringing a freshwater lake.
Amended diagnosis of Grallatoridae based on mesaxony and footprint elongation.
The new ichnotaxon Picunichnus quijadaensis (Grallatoridae) is proposed.
Osteometric comparisons suggest that the trackmaker is not yet recorded as fossil.
Abstract
New findings of well-preserved theropod dinosaur footprints from the Albian Lagarcito Formation (Sierras de Las Quijadas National Park, San Luis, Argentina) are described and its paleoenvironmental and stratigraphic context is discussed. The local succession of the formation is represented by three shallowing-upward cycles that were deposited in a lacustrine setting. The theropod footprints occur in sheet flood facies fringing the lake and probably were mostly oriented parallel to the shoreline. The footprints are assigned to Picunichnus quijadaensis Melchor nov. isp. which is distinguished from similar ichnotaxa by the degree of mesaxony, footprint elongation, digit proportions and occasional presence of a hallux impression. Based on the comparison of type material of theropod ichnotaxa, it is suggested that Picunichnus belongs to the ichnofamily Grallatoridae Lull, 1904, which is amended to include Grallator, Anchisauripus, and Prototrisauropus. This revision also suggests the potential recognition of additional ichnofamilies for theropod dinosaur footprints. Preservation of digital pads in P. quijadaensis also permits an osteological comparison with theropods from Gondwana. This comparison is based on the length of pedal bones inferred from P. quijadaensis and similar information on selected Jurassic-Cretaceous theropods. In addition, relative size, age and geographic provenance are also contrasted. There is no known Gondwanan theropod dinosaur with preserved pedal bones that match all these features. The best candidates are the smaller basal coelurosaur Aniksosaurus darwini from the Cenomanian of Patagonia and the similar-sized abelisaurid Majungasaurus crenatissimus from the Maastrichtian of Madagascar. This finding is relevant because the footprints come from a geographic area lacking skeletal or other footprint records of Cretaceous theropods and because the producer is apparently not recorded by skeletal remains in Gondwana continents.
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Multifissoolithus chianensis new oogenus & oospecies
ZHANG Shu-Kang, XIE Jun-Fang, JIN Xing-Sheng, DU Tian-Ming & HUANG Mei-Yan (2019)
New type of dinosaur eggs from Yiwu, Zhejiang Province, China and a revision of Dongyangoolithus nanmaensis.Â
Vertebrata PalAsiatica (advance online publication)
DOI: 10.19615/j.cnki.1000-3118.190107
A new type of dinosaur egg, which is remarkable for the roughly paralleled, wavy and branched clefts on the outer surface, was recovered from Yiwu, Zhejiang Province, China. The extraordinary ornamentation indicates that the eggs do not belong to any known oofamilies. Interestingly, they share the following eggshell micro-features with Dongyangoolithus nanmaensis, which was previously assigned to the Dendroolithidae: branched clefts on the outer surface of the eggshell and eggshell unit assemblages separated by large cavities. Due to these similarities and the nearness of their localities and similar horizons, the new type of dinosaur eggs from Yiwu and D. nanmaensis likely represents a new oofamily, Dongyangoolithidae. Based on the differences in shape between the eggshell unit assemblages and clefts of the new type of dinosaur eggs and D. nanmaensis, we erect a new oogenus and a new oospecies, Multifissoolithus chianensis. The new oofamily reported here shows a close relationship with Spheroolithus in Spheroolithidae and an intermediate pattern of gas exchange systems.Â
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