Dinosaur Evolution: A Journey from Tetrapod to Bird

Xenotaris

Okay before I get in to direct Dinosaur evolution I must first weave the tale of how these guys came along, okay lets start with the Fish that crawled out of the water otherwise it would be a drag explaining the evolution of fish.

Okay along time ago back around the Devonian time, a group of Lobe-fin fishes gradually evolved lungs and slowly crawled out of the water on to land to possibly escape from hungry predators.

These fish became the first Tetrapods or Amphibians, millions of years later and millions of generations later prototreptile amniotes then evolve from Reptiliomorph amphibians during the Carboniferous peroid, officially around the Pennsylvanian Epoch but it is possible they could of appear in the Mississippian epoch.

Animotes later diverged in to two clades: Synapsids (Mammal-like Reptiles and later Mammals) and Sauropsida (Classic Reptiles).

Now since we are going in to later dinosaur evolution we can mark out the Synapsids from the discussion since that would be a topic for a later time.

Sauropsida is then divided into Parareptilia (at the side of reptiles) and Eureptilia (True Reptiles)

Eureptilia later gives rise to several lizard-like early reptiles and then the clade Romeriida evolves which will give rise to Diapsid reptiles (Modern Reptiles and their extinct relatives)

Diapsid Reptiles would evolve in to several primitive forms before two notable clades would eventually win out so to speak. Lepidosauromorphs (Snakes, lizards, Tuatara, and their extinct relatives like mosasurus) and Archosauromorphs (Ruing Reptiles). Pantestudines in my opinion belongs with Archosauromorph due to DNA and Fossil record backing. This ends the Permian peroid.

Archosauromorphs, now where getting closer. After several basal clades we finally get Archosauriformes. Most Archosauriformes roughly resembled crocodiles if more lightly armored to barely armored but lets flash forward to the clade of Archosauria; seeing as the other Archosauriformes are no long relevant to this topic. Which happens mostly in the Early Triassic.

Archosauria can be divided in to two super clades: Avemetatarsalia/Ornithodira and Pseudosuchia (Crocodilans and their extinct relatives like the Rauisuchians)

Avemetatarsalia also known as Ornithodira or Pan-Aves is the clade that holds the Pterosauromorphs and the Dinosauromorphs.

Dinosauromorphs clade contains all Dinosaur clades including modern birds and their extinct relatives. Dinosauromorphs that were closer related to true Dinosaurs were Dinosauriformes while Non-dinosaurian dinosaurmorphs belong to Lagerpetids.

Dinosauriformes housed several dinosaur-like forerunners but the most developed group besides the dinosaurs themselves were the Silesaurids. These creatures appeared roughly in the Middle Triassic.

And now we finally arrived to the clade Dinosauria which itself is broken up in to two major clades: Ornithischia (Bird-hip Dinosaurs) and Saurischia (Lizard-hip Dinosaurs) both arrived in the Late Triassic.

Ornithischia can be splitted up in to three primary clades: Ornithopods (basically beaked bipeds and duckbills), Thyreophora (Plated and armored dinosaurs with attack tails), and Marginocephalia (Head Armored Dinosaurs)

Saurischia is simply divided in to two clades: Sauropodomorphs (Long Necked herbivores) and Theropods (Bipedal Carnivores, later some beaked long necked bipedal herbivores, and birds)

The earliest members of Saurischia were fairly theropod-like but we do know the earliest members of each clade. Eoraptor long suspected to be a primitive theropod or even a basal Saurischia is now thought to be a primitive sauropodomorph along with the similar Guaibasaurids while Eodromaeus snags the spot of the Eoraptors previous position as an early theropod along side the slightly more advanced Herrerasaurids.

Darth Shiro

I will contact Lord Tyrant and maybe Raptor-401.

Xenotaris

sweet!

Darth Shiro

finished

Xenotaris

As much as I love Jurassic-Cretaceous dinosaurs, I find earlier Triassic Dinosaurs more fascinating because of their more basal routes and I'm fascinated with early dinosaur evolution. I know its easier to love Utahraptor, Tyrannosaurus, Velociraptor, Triceratops, Apatosaurus, Parasaurolophus, Ankylosaurus, Stegosaurus, Brachiosaurus, or even Spinosaurus but Triassic dinosaurs were like the great grand parents of the more famous dinosaur clades.

Darth Shiro

Yeah! My favorite Triassic dinosaur is Gojirasaurus quayi! For the Jurassic i must say Allosaurus and finally for the Cretaceous period Spinosaurus who's also my favorite dinosaur. I also like Styracosaurus and Brachiosaurs.

Xenotaris

Ah Gojirasaurus, a rather large Coelophysoid. Hey its not too distant from my favorite dinosaur, Dilophosaurus.

Darth Shiro

Yup! I love Gojirasaurus because as a Coelophysoid it is HUGE!! Like Godzilla as you see in my profile pic.

Xenotaris

Hey it might of had competition with another large coelophysoid Liliensternus. although my Dilophosaurus is bigger but Dilophosaurus is an Early Jurassic Theropod with the body of a Late Triassic Theropod. Dilophosaurus a while back was considered to be a Coelophysoid before being placed in its own clade Dilophosauridae.

Darth Shiro

Yeah.

I Meme Everything

Gojirasaurus is my favourite Triassic dinosaur

Darth Shiro

cool.

Darth Shiro

No updates Xeno?

Xenotaris

Sorry, I will update soon. I'm trying to think which Dinosaur linage/clade to do next.

Darth Shiro

Ok

Xenotaris

Any Suggestions?

Darth Shiro

Maybe the Pterosaurs?

Xenotaris

Well that's outside of Dinosauria Evolution but they are both Avemetatarsalia

Darth Shiro

Mmmhhm

Xenotaris

Hey I know I will discuss Spinosaurid evolution

Xenotaris

Spinosaurids: My opinion on them is this, as an animal and part of dinosaur evolution I do find them fascinating since they seem to of been gradually evolving in to aquatic animals and had not the early late cretaceous waters been Anoxic (de-oxygeniated) during the Cenomanian-Turonian boundary event, we possibly would of seen fully aquatic dinosaurs. However as far as popular portrayal of the Spinosaurus goes, I despise the Jurassic Park III and Planet Dinosaur's depictions of the Spinosaurus.

Just to clarify: I have nothing against the real animal that is Spinosaurus aegyptiacus, Now on to Spinosauridae evolution.

Okay well Spinosaurids belong to the superfamily Megalosauroidea which were a group of stiffed tailed Theropods or tetanuran that reached to medium to large porportions before the Avetheropods (Bird-aligned tetanurans) such as Allosaurus, Tyrannosaurus, and the Haast's Eagle. But before we get in to the them ( i would like to get in to a more detailed with T. rex evolution later, I feel that my explanation was too brief), lets refocus on the Spinosaurids.

Most basal spinosaurids weren't that impressive, such as Ostafrikasaurus, It had a slight elongated snout and a slightly high spines but it closely resembled its megalosaurian cousins. however it is believed to be closer to the baryonyx-line of the Spinosaurids and then there is Siamosaurus who is another basal spinosaur but it had a longer snout than its cousin Ostafrikasaurus and its teeth resembled that of Spinosaurus. Sinopliosaurus, a Chinese basal Spinosaurus that was originally thought to be a pliosaurus that is only known for its collection of teeth which resembles Thailand's Siamosaurus, which quite possibly could be a synonyms. There is another possible basal spinosaurid that has yet to be named that's remains were found in Australia.

Okay now were don with the basal members time to move on to their more advanced relatives the subfamilies Baryonychinae and Spinosaurinae. Starting with the Baryonychinae:

Ichthyovenator, a basal baryonchina spinosaurid that's remains were discovered in Laos.

Baryonyx, one of the two most famous members of its subfamily. Discovered in England this Spinosaurid, it may have hunted near lakes or river deltas.

Suchomimus, the second of the two most famous member of its subfamily. Discovered in Niger Africa, this spinosaurid is larger than baryonyx and had a short pronounced spinal ridge.

Cristatusaurus, a baryonchinae spinosaurid that maybe be a Suchomimus or its own genus.

Suchosaurus, it maybe a Baryonyx.

Xenotaris

Okay now for the Spinosaurinae:

Irritator, despite being a close relative to Spinosaurus, it lacks the signature spine of its cousin and it was a lot smaller. Its remains were discovered in Brazil.

Sigilmassasaurus (formerly Spinosaurus maroccanus) it unlike its larger cousin, Sigilmassasaurus lived primarily on land. Its remains were discovered in Morocco, Africa.

Spinosaurus, discovered in Egpyt, Africa. One of the most bizarre theropods, with its crocodilian head combined with its rather large sail-like protrusion of its spine and now as of 2014, a quadruped. It quite possibly lived a semi-aquatic lifestyle along side crocodilians who they may of competed for fish, on the land the Spinosaurus was rivaled by the allosauroid Carchardontosaurus. 

Oxalaia, little can be said of this spinosaurid as its fossils have yet to be completed and it was discovered in Brazil.

Darth Shiro

I love Spinosauridae! The Baryonichinae evolution is very interesting. Also i agree with you as much as i love Jurassic Park 3 and Planet Dinosaur, their description of our Spinosaurus is wrong. If you see the photos of Stromer (i spelled his name right?) the fossils were OVERSIZED!! I have the National Geographic journal of the 2014 Spinosaurus with me and Ibrahim's decription is quite good and respects the laws of physics as for the size and posture. Also if we should have more animals than dinosaurs! Like the marine reptiles and the flying reptiles. Thanks Xeno for posting the Spinosaurid evolution :D!

Xenotaris

Your welcome, I'm sure I could expand the Topic soon.

Darth Shiro

Also this post is expanding my knowledge on Dinosaurs as i can only recognise them and state their traits.

Xenotaris

I think I will discuss Dilophosaurus evolution next.

Darth Shiro

ok......*is sad and depressed*.......

Xenotaris

alright I will also talk about Pterosauromorph evolution as well

Xenotaris

I'm going to make a separate post for Pterosaurs and Marine Reptiles

Darth Shiro

cool!

I Meme Everything

Nice!  I love the Spinosaurids.

Spinosaurus, the internet's most overrated dinosaur