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[dinosaur] Mexico: hadrosaur dental microwear + metriorhynchid jaw remains (free pdfs)



Ben Creisler
bcreisler@gmail.com

Papers from the recent issue of PaleontologÃa Mexicana:

Free pdf:

HÃctor E. Rivera-Sylva, Christina I. BarrÃn-OrtÃzb, Rafael l Vivas GonzÃlez, Rosalba Lizbeth Nava RodrÃguez, Josà RubÃn GuzmÃn-GutiÃrreza, Fernando Cabral Valdez & Claudio de LeÃn DÃvila (2019)
Preliminary assessment of hadrosaur dental microwear from the Cerro del Pueblo Formation (Upper Cretaceous: Campanian) of Coahuila, northeastern Mexico.
PaleontologÃa Mexicana 8(1): 17--28
http://www.ojs-igl.unam.mx/index.php/Paleontologia/article/view/606


Here we report new hadrosaur remains recovered from the Cerro del Pueblo Formation (Upper Cretaceous: Campanian) at La Parrita locality, northeastern Mexico. Although the material is fragmentary, the identification of dental microwear in three out of the four teeth collected is notable. This sample allows for a preliminary assessment of hadrosaur dental microwear from this geographic region and time frame. The variables studied were the orientation and average count of scratches, average count of pits, and average microwear feature width in an area of 400 X 400 Îm at 35X magnification. The results show a predominance of dorsodistally-ventromesially inclined scratches in all three teeth indicating that the mandible primarily moved in an orthopalinal direction during the power stroke. The pattern of scratch orientation we recorded is comparable to that reported for different hadrosaur species from Alberta, Canada, and Wyoming, U.S.A.; suggesting similar jaw mechanics in the hadrosaurs from Coahuila. In contrast, there are significant differences in the average number of pits and microwear feature width between the Alberta and the Coahuila hadrosaurs samples, with the latter presenting more pits and finer microwear features. Given the similar jaw mechanics between the Alberta and Coahuila hadrosaurs, suggested by our analysis, the difference in average number of pits and microwear feature width is probably due to differences in diet and/or the type and amount of grit ingested during feeding. The greater number of pits in the hadrosaurs from Coahuila might indicate that these individuals ingested a greater proportion of hard food items than the Alberta hadrosaurs.




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Free pdf:

Jair Israel Barrientos-Lara & JesÃs Alvarado-Ortega (2019)
Restos mandibulares de un cocodrilo marino (Thalattosuchia, Metriorhynchidae) del Llano YosobÃ, en Tlaxiaco, Oaxaca, MÃxico.
[Mandibular remains of a marine crocodile (Thalattosuchia, Metriorhynchidae) from Llano YosobÃ, ei Tlaxiaco, Oaxaca, MÃxico]
PaleontologÃa Mexicana 8(1): 65-73
http://www.ojs-igl.unam.mx/index.php/Paleontologia/article/view/610


The Metriorhynchidae (Crocodylomorpha) gathers highly specialized marine crocodiles, permanent habitants of the open sea, and very efficient predators in the tropical seas of the Jurassic. These have a large fossil record in Europe and South America while in North America the metriorhynchid remains are very scarce and are limited to a couple of species found in north and central Mexico. Other specimens of this group of uncertain affinity have been found in Cuba. This work includes the description of a new metriorhynchid specimen from the Sabinal Formation (Kimmeridgian), which is identified as a Metriorhynchinae indeterminate for its dental characters. This specimen adds to the diversity and high richness of specimens offered by of the Upper Jurassic locality known as Llano Yosobà in southern Mexico.

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