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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
Hey everyone, recently came across this partial vertebra from the Kimmeridge Clay online, apparently collected south of Oxford. It measures 9.5cm x 8.5cm. The seller tentatively identified it as a Stegosaurid based on the internal pattern visible on the polished side, and subsequently assigned it to Dacentrurus, since it's the only Stegosaurid fitting the time and location. I tried to find more information on these supposed patterns indicative of Stegosaurs without much success, so I'd like to ask: › Is the vertebra actually identifiable on a family level? › If so, what are the defining characteristics and where could I read up about them? Thanks for your help!
The family tree was announced back in February but the paper was just published. https://www.theguardian.com/science/2017/apr/19/how-we-revealed-a-new-family-tree-for-dinosaurs?CMP=share_btn_tw Abstract: For 130 years, dinosaurs have been divided into two distinct clades—Ornithischia and Saurischia. Here we present a hypothesis for the phylogenetic relationships of the major dinosaurian groups that challenges the current consensus concerning early dinosaur evolution and highlights problematic aspects of current cladistic definitions. Our study has found a sister-group relationship between Ornithischia and Theropoda (united in the new clade Ornithoscelida), with Sauropodomorpha and Herrerasauridae (as the redefined Saurischia) forming its monophyletic outgroup. This new tree topology requires redefinition and rediagnosis of Dinosauria and the subsidiary dinosaurian clades. In addition, it forces re-evaluations of early dinosaur cladogenesis and character evolution, suggests that hypercarnivory was acquired independently in herrerasaurids and theropods, and offers an explanation for many of the anatomical features previously regarded as notable convergences between theropods and early ornithischians Paper it's paywalls publication http://www.nature.com/nature/journal/v543/n7646/abs/nature21700.html
Here is another peice of my work, this profile is on the Stegosaurus and once again I would like to see what you all think but keep in mind I kind of wrote this in a biased way, as in I used the theories I think are true without mentioning other ones so Forgive me for that. But hey, At least it's pretty simplified. Stegosaurus is one of the Most well known of all dinosaurs along with the T.rex and the Velociraptor. Despite this very, very, very, few people know what it actually looked and behaved like. For example the Stegosaurus has Sexual Dimorphism which means a difference in the males and female's. Females have sharp pointed Plates along its back while the males back plates would be rounded kind of like a squashed circle. Stegosaurus is part of the Stegosauri family that arrived on the scene in the early Jurassic and died out at the end of the Jurassic Period. Stegosaurus grew to be 30 feet long and 9 feet tall which 3 foot long plates and 3 foot long thagomizers which were the spikes at the end of the tail, that it used for self defense. Stegosaurus has extremely small heads even for a Stegosaurs, They fed on Fern cycads and Conifers which were the dominant plant species in the Jurassic period in North America. Another thing, Stegosaurus is native to North America in places such as Wyoming and South Dakota along with animals like Brachiosaurus and the Brontosaurus Stegosaurus also have a thick armor on its neck represented by thick rock like scales. While the bone plates and thagomizers in the skeleton are large, they were much larger in life as they were covered in keratin and thick sponge bone like material. It's notable to mention that Stegosaurus tail spikes called thagomizers are at the tip of the tail and unlike many archosaur tails which get thicker and stiffer near the end instead are very flexible like the tail of a monkey in order to swing around their thagomizers with great accuracy against predators, killing a Allosaur in one blow or at least wounding it badly. Fossil Records of Allosaurus show puncture woulds in areas like the leg or against the pubic bone which is part of Pelvis. These were caused by the Stegosaurus which was defending itself or a baby, Now while they have these large spikes to protect themselves they also have these large kite shaped sponge plates which were not protection but was used for Courtship for females and to confuse predators, This means it would flush blood into its plates and they would turn to bright red along with other colors, the body would likely be green or brown while the plates would have bright colors much like a Baboons Colorful face. Stegosaurus was discovered by the Famous Charles Marsh in 1877 and Stegosaurus had this very wide gap of space in between its hips and Marsh thought in this space it had a Secondary brain. Now he thought this because this elephant size animal had the brain the size of a dogs brain. He thought this was not enough and he had to had a secondary brain to help it function. Not true it did not have a second brain and no dinosaur or reptile ever had a second brain.