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A new paper is out online that you'll find shocking: Müller RT, Garcia MS. 2020. A paraphyletic ‘Silesauridae’ as an alternative hypothesis for the initial radiation of ornithischian dinosaurs. Biol. Lett.16:20200417. http://dx.doi.org/10.1098/rsbl.2020.0417 I remember that several Late Triassic animals erected upon teeth (Crosbysaurus, Galtonia, Krzyzanowskisaurus, Lucianosaurus, Pekinosaurus, Protecovasaurus, Revueltosaurus, and Tecovasaurus) were once classified within Ornithischia because the type teeth of those taxa are similar to those of ornithischians (some early sauropodomorphs have leaf-shaped teeth, too), but Revueltosaurus was later reclassified as an extinct relative of alligators and crocodiles based on complete material, and Galtonia and Pekinosaurus were also recognized as suchians closely related to Revueltosaurus, meaning that other putative Triassic ornithischian taxa from the American Southwest were placed in Archosauriformes incertae sedis by Parker et al. (2005) and Irmis et al. (2007) due to the presence of triangular leaf-shaped teeth being convergent among ornithischian dinosaurs and some non-dinosaurian clades. The hyper-sparse record of Triassic Ornithischia left people scratching their heads to explain the paucity of Triassic ornithischian fossils, with some speculating that ornithischians did not diversify until the Early Jurassic; the fact that Pisanosaurus combines some craniodental traits of Ornithischia more advanced than those of Lesothosaurus and the postcranial traits of basal dinosauriforms complicated matters further, because this mosaic of morphological features threatened the status of Pisanosaurus as the oldest ornithischian. Agnolin and Rozadilla (2018) tidied up matters by concluding that Pisanosaurus is a silesaurid that evolves craniodental features convergent with those of advanced ornithischians. The new paper by Muller and Garcia (2020) has a pretty novel hypothesis to explain the virtually non-existence of Ornithischia in Triassic deposits. It shockingly recovers Silesauridae as paraphyletic with respect to traditional Ornithischia (containing Genasauria and Eocursor), suggesting that the earliest relatives of Ornithischia evolved a purely faunivorous diet, given that Asilisaurus from Tanzania has sub-triangular crowns and a constricted root and dentaries with a beak-like anterior tip. For instance, Lewisuchus is recovered a more primitive than Soumyasaurus and Asilisaurus. Since Pisanosaurus has a mosaic of ornithischian-like features and postcranial traits usually seen in non-dinosaurian dinosauromorphs, it may be surmised that the earliest dinosaurs had some postcranial features similar to those of lagerpetids and Lagosuchus. Of interesting note is the fact that Technosaurus (named for Texas Tech University where the holotype is stored) was once considered a 'fabrosaurid' ornitischian before it was classified as a silesaurid, so the placement of all silesaurs as closely related to Ornithischia and recovery of Pisanosaurus as sister to Ornithischia means that the peculiar morphology of Pisanosaurus renders silesaurs more closely related to ornithischians. Randall B. Irmis, William G. Parker, Sterling J. Nesbitt & Jun Liu (2007) Early ornithischian dinosaurs: the Triassic record. Historical Biology, 19:1, 3-22, DOI: 10.1080/08912960600719988 Parker, W. G., Irmis, R. B., Nesbitt, S. J., Martz, J. W., & Browne, L. S. (2005). The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. Proceedings. Biological sciences, 272(1566): 963–969. https://doi.org/10.1098/rspb.2004.3047

Well the Tuscon fossil show is just a few days away and I'm already getting calls from sellers wanting to get together this weekend. Hopefully the show will be full of cool displays and will pass on a few of those images next week. But here we are week 3 in the new year so lets begin with this weeks show. An almost complete hatchling specimen of the basal sauropodomorph Mussaurus patagonicus from the MacnVp colletion in Argentina. This specimen is from the Early Jurassic of the Argentinian Patagonia Courtesy, Bernardino Rivadavia Natural Sciences Argentine Museum Skull is in top right. A couple of photos of the T rex Scotty Now this is a T rex tooth, one of the best I've seen and gotta like its size Femur Another T rex specimen this one Burke's Museum... they say " can you believe that the humerus (upper arm bone) of a T. rex is nearly the same size as yours? " Pretty rare specimen, not a lot around From the NHM Dino lab The weird Triassic herbivore Pisanosaurus in the PVL collections. Based on a single partial skeleton discovered in the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina Also from the NHM Dinolab : Coloradisaurus is a genus of massospondylid sauropodomorph dinosaur. It lived during the Late Triassic period in what is now La Rioja Province, Argentina. It is known from the holotype PVL 5904, nearly complete skull. The recently-named Cryodrakon boreas was one of the largest-ever flying animals, with an estimated 10-meter wingspan. This tibia contains a tooth left behind by a scavenging dromaeosaur. Courtesy Royal Tyrrell Museum. Now thats a cool specimen... These beautiful feet belong to a nearly complete specimen of Saurornitholestes, from Alberta. Courtesy Mark Powers