Blistery Bumps On Buttock

Saturnalinos and devil horns

Saturnalinos and devil horns

Pandora Bracelet Manhattan

The roots of the giant

The roots of the giant

Jeep Libertychanging Shocks

Dawn of the Dinosaurs


As we all know from childhood, dinosaurs are some reptiles that evolved from an older animal and it's an older animal, but today I want to go deeper into the origin of the dinosaurs. To do this, we must go back to the Permian period, about 270 million years.

Yes, still missing 40 million years to see the first dinosaur, but these days you can see the roots from which flourished terrible lizards. A mid-Permian is precisely when the lineage of reptiles diápsidos begins to separate into two branches, lepidosaurs and archosaurs. Archosaurs are the first to differentiate, and although at first the group was comprised only small thecodont (polyphyletic group whose use is declining) The group later became one of the most successful in history.

The archosaurs were distinguished from their predecessors thanks to some evolutionary novelty (features of each clade that place it in a phylogenetic tree). The main one is the way to a half upright position, that in the first thecodont could switch to classical view of lizard with legs extended. The price of this alternative form of travel was given at the ankles of thecodont, where he had joint replacement, foot bones based on a more consistent and less "flexible" to hold more weight when the animal was upright.

In the skull, besides the two fenestrae diápsidos characteristics, opened a anteorbital fenestra (in front of the eye) and a mandibular fenestra, whose purpose would be to lighten the skull and provide space for insertion of muscles. In fact, the use of fenestrae in the dinosaurs came to be exaggerated in some cases, more hollow bone surface. Finally, curved jaws and serrated teeth developed, typical of a carnivorous diet to replace the insectivorous diet diápsidos Carboniferous reptiles. All this, plus the increase allowable size by upright posture, made these archosaurs in worthy predators.

All these features would be fully developed with thecodont closer to the dinosaurs, as is the case Euparkeria, small thecodont South Africa. What could really happen in the Middle and Late Permian would be an evolutionary divergence between thecodont, which while some developed previously said traits, others took an amphibious lifestyle similar to crocodiles, and took evolutionary paths that lead them Crocodilomorpha form the group. These were the proterosúquidos thecodont , whose main representative is Proterosuchus (image below).

After seeing all this, we will focus on the environment Euparkeria and his contemporaries. In the Upper Triassic numeros0s were already extinct groups of all kinds, including gorgonopsids or pelycosaurs, which abounded in the Permian, so that new faunas are filling the ecological vacuum. Cynodonts , dicynodonts and rincosaurios are some of the animals that live with thecodont. The rincosaurios were some primitive herbivorous archosaurs, although they were widespread during the Triassic, was the only period in which they lived. These small herbivores a pig, were probably common prey of the first dinosaurs.

At this time the thecodont reached a dominant position on earth, and soon some of them evolve enough to be considered dinosaurs. The Lagosuchus was a small reptile (probably closer to the dinosaurs), Argentina, shaped like a lizard, which ended up adopting a bipedal upright position.

definitely at the beginning of the Late Triassic, dinosaurs appeared around the world, including Argentina, USA, Germany, Madagascar or Brazil, between 230-215 million years ago. Specifically are Eoraptor, Staurikosaurus Herrerasaurus and fossils that have more seniority, so that we can say that the group originated in America, with South Africa at high speed (Triassic Atlantic did not yet exist), North America and Europe today is . Features

ankle and hip dinosaurs were the main evolutionary novelties. Having adopted a fully upright position, the ankle had to endure more weight than their ancestors semi-upright, so that the joint configuration changed again. Old system was replaced by the ankle MA (Mesotarsiano Advanced) which the talus is much greater than the calcaneus (both bones of the ankle) and form the single joint between the tibia and foot, making a simple hinge system and giving up the high mobility of the ankle which provided the previous system.

hip occurred in a series of changes caused by an enlarged and upright. First, the three innominate (ilium, ischium and pubis) were opened in three different directions to leave a gap between them called the acetabulum, which served as the anchor to insert the femoral head in an upright position. The expansion of the ilium and the presence of three or more vertebrae in the region Sacred also modified the hip, but a group of dinosaurs went further. This is the ornithischians, who unlike saurischians "moved" the pubis backward until it aligned with the ischium. This sudden change had already begun in the early Jurassic to the early ornithischians (as Lesothosaurus ), and there are two explanations that can justify it.

The best known is the hypothesis of increased bowel herbivorous dinosaurs (note that this is the diet of all ornithischians), which eventually make room for the pubis take back everything possible and so save space. Sauropods, although also were herbivores, resigned to modify the hip and was confined to enlarge your body, housing a huge gut.

Another hypothesis, proposed by Dr. Alan Charig (1927-1997), is equally valid. This is based on the approach of the pubis and ischium in the hip of all dinosaurs and adopted the upright position, the femur and pubic became very close. Reptiles move their feet forward to the muscle 1 (does anyone know his name?) The diagram below, and back to muscle-femoralis Caudio (ranging from femur to the base of the tail). As shown in the illustration, the muscle 1 is no space left to maneuver when approaching both the femur and pubis, which ornithischians solution turned to move the pubis backward and anchoring this muscle in the front of the ilium, or a pubic apophysis who developed some ornithischians.

Sauropods would not give solution to this problem, and were limited to move slowly, and theropods up the body and pubic thanks to its standing position with the muscle 1 earned enough space.

And then, when the aforementioned features dinosaurs were diversifying more and more taking increasingly bizarre features and distinctive, so much so that while some flew, others developed armor or surpassed the 30 and even 40 tons of weight.

Bibliography: G. Spencer

Lucas (2007): Dinosaurs "textbook" . Barcelona, \u200b\u200bEdiciones Omega.

David Norman (2003): Illustrated Atlas of the Dinosaurs . Madrid, Ediciones Susaeta.