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[dinosaur] Isisfordia molnari, new Cretaceous eusuchian from Australia + flightless birds + ridged teeth (free pdfs)

Ben Creisler

Non-dino papers with free pdfs:

Isisfordia molnari sp. nov.

Lachlan J. Hart, Phil R. Bell, Elizabeth T. Smith & Steven W. Salisbury (2019)
Isisfordia molnari sp. nov., a new basal eusuchian from the mid-Cretaceous of Lightning Ridge, Australia.
PeerJ 7:e7166
doi: https://doi.org/10.7717/peerj.7166

Free pdf:

The Australian Mesozoic crocodyliform record is sparse in comparison to other Gondwanan localities. A single formally-named taxon is known from this interval; Isisfordia duncani (Winton Formation, AlbianâTuronian, Queensland). We present a previously undescribed crocodyliform braincase from the Griman Creek Formation (Cenomanian), New South Wales, which we assign to Isisfordia molnari sp. nov. Assignment to the genus is based on the possession of a newly-defined autapomorphy of Isisfordia: a broadly exposed prootic within the supratemporal foramen. A second autapomorphy of I. duncani (maximum diameter of the caudal aperture of the cranioquadrate siphonium approximately one-third the mediolateral width of the foramen magnum, with the lateral wall of the caudal aperture formed exclusively by the quadrate) may also be present in I. molnari; however, definitive recognition of this feature is marred by incomplete preservation. The new taxon is differentiated from I. duncani based on the absence of a median ridge on the parietal, and the lack of characteristic ridges on the parietal that form the medial margin of the supratemporal foramina. Reanalysis of a second specimen (the former holotype of the nomen dubium,âCrocodylus (Bottosaurus) selaslophensisâ) allows for its referral to the genus Isisfordia. Crucial to this reappraisal is the reinterpretation of the specimen as a partial maxilla, not the dentary as previously thought. This maxillary fragment possesses specific characteristics shared only with I. duncani; namely an alveolar groove. However, several key features differentiate the maxillary fragment from I. duncani, specifically the presence of continuous alveolar septa, the thickening of the medial alveolar rim, and the alveolar and crown base morphology. These findings constitute the first evidence of Isisfordia outside of the type locality and indicate its widespread occurrence on the freshwater floodplains along the eastern margin of the epeiric Eromanga Sea during the AlbianâCenomanian.

Free pdf:

Shengkai Pan, Yi Lin, Qiong Liu, Jinzhi Duan, Zhenzhen Lin, Yusong Wang, Xueli Wang, Sin Man Lam, Zhen Zou, Guanghou Shui, Yu Zhang, Zhengwang Zhang & Xiangjiang Zhan (2019)
Convergent genomic signatures of flight loss in birds suggest a switch of main fuel.
Nature Communication 10, Article number: 2756 (2019)
doi: https://doi.org/10.1038/s41467-019-10682-3 O

Free pdf:

Flight loss in birds is as characteristic of the class Aves as flight itself. Although morphological and physiological differences are recognized in flight-degenerate bird species, their contributions to recurrent flight degeneration events across modern birds and underlying genetic mechanisms remain unclear. Here, in an analysis of 295 million nucleotides from 48 bird genomes, we identify two convergent sites causing amino acid changes in ATGLSer321Gly and ACOT7Ala197Val in flight-degenerate birds, which to our knowledge have not previously been implicated in loss of flight. Functional assays suggest that Ser321Gly reduces lipid hydrolytic ability of ATGL, and Ala197Val enhances acyl-CoA hydrolytic activity of ACOT7. Modeling simulations suggest a switch of main energy sources from lipids to carbohydrates in flight-degenerate birds. Our results thus suggest that physiological convergence plays an important role in flight degeneration, and anatomical convergence often invoked may not.


This paper was posted on the DML in preprint form in April but now is officially published with a free pdf:

Free pdf:

Matthew R. McCurry, ÂAlistair R. Evans. Erich M. G. Fitzgerald. Colin R. McHenry, ÂJoseph Bevitt Â& Nicholas D. Pyenson (2019)
The repeated evolution of dental apicobasal ridges in aquatic-feeding mammals and reptiles.
Biological Journal of the Linnean Society 127(2): 245â259
doi: https://doi.org/10.1093/biolinnean/blz025

Since the Permian, Earthâs aquatic ecosystems have been ecologically dominated by numerous lineages of predatory amniotes. Many of these groups evolved elevated ridges of enamel that run down the apicalâbasal axis of their teeth, referred to here as apicobasal ridges. This trait is commonly used as a taxonomic tool to identify fossil species and higher groupings, but the function of the ridges and their associated ecological significance are poorly understood. Here, we aim to clarify the phylogenetic distribution of apicobasal ridges among amniotes and to examine how the morphology of apicobasal ridges varies across species. We show that these ridges have evolved independently numerous times and are almost exclusively found in aquatic-feeding species. Ridge morphology varies, including tall, pronounced ridges, low, undulating ridges and interweaving ridges. Their internal structure also varies from tooth crowns with locally thickened enamel to undulating enamelâdentine interface. We assess the relative merits of different hypothetical functions of the ridges and propose that although apicobasal ridges might provide some strengthening of the tooth, their morphology and pattern of evolution do not indicate that this is their primary function. Instead, we suggest that apicobasal ridges serve to increase the efficiency of puncture, grip and/or removal.

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