Group in Depth: Basal Theropoda

Source: http://t-pekc.deviantart.com/art/Tawa-hallae-546069775

Group: Theropoda

Classification: Cellular Life, Archaea, Proteoarchaeota, Eukaryota, Unikota, Opisthokonta, Holozoa, Filozoa, Metazoa, Eumetazoa, Planulozoa, Bilatera, Nephrozoa, Deuterostomia, Chordata, Craniata, Vertebrata, Gnathostomata, Eugnathostomata, Teleostomi, Euteleostomi, Sarcopterygii, Rhipidistia, Tetrapodomorpha, Eotetrapodiforms, Elpistostegalia, Stegocephalia, Tetrapoda, Reptiliomorpha, Anthracosauria, Batrachosauria, Cotylosauria, Amniota, Sauropsida, Eureptilia, Romeriida, Diapsida, Neodiapsida, Sauria, Archosauromorpha, Archelosauria, Archosauriformes, Crurotarsi, Archosauria, Avemetatarsalia, Ornithodira, Dinosauromorpha, Dinosauriformes, Dinosauria, Saurischia, Eusaurischia 

Definition: All dinosaurs more closely related to Megalosaurus than to Apatosaurus 

Organisms Within: Daemonosaurus, Eodromaeus, Tawa, Herrrasauridae (not examined here), Neotheropoda (not examined here), & miscellaneous nomen dubium & not formally described genera (not examined here) 

Time Range: Shown below; numbers on the left are in millions of years. It is clear that Theropods and Sauropodomorphs diverged from one another early in Saurischian evolution, and basal Theropods lasted longer in the Triassic than basal Saurischians did, though they probably went extinct (with more derived theropod lineages surviving) at the end of the Triassic.  

Characteristics: Small carnivorous Saurischians, one of the two major lineages of Eusaurischia, the other being Sauropodmorphs. Theropoda comprises a wide range of dinosaurs from Coelophysis to Tyrannosaurus to Velociraptor to the modern house sparrow and all modern birds. The early ones, however, were all small gracile bipedal carnivores, with long necks and tails. 

Source: https://en.wikipedia.org/wiki/Eodromaeus_murphi

They were probably covered with protofeathers based on phylogenetic bracketing; and though they look similar to the basal Saurischians of last week, they were distinct in being a part of only the Theropoda line, and having diverged from the Sauropodomorphs. Tawa, however, may be a Coelophysoid, an even more derived Theropod group. 

Source: http://www.smithsonianmag.com/science-nature/daemonosaurus-shakes-up-the-early-history-of-dinosaurs-175320534/?no-ist

Fossil Locations: It appears that Theropods originated where dinosaurs did, in Argentina, which makes sense given their apparent early divergence from other Saurischians. They then migrated up through to North America. 

(Colored = country has fossil sites; line points to the approximate fossil location). 

Biogeography: At the time of the Triassic, all the land masses were combined into one supercontinent, the famous Pangaea. Though the major locations of the continents remained fairly unchanged over the time period these three organisms lived, each individual age is given its own map below. All maps taken from Dr. Christopher Scotese. 

It appears that basal Theropods migrated up to the modern American Southwest, though later Theropod distribution covers all continents. 

Read more about Eodromaeus here

Read more about Tawa here

Read more about Daemonosaurus 

Read more about Herrerasauridae here 

Read more about Neotheropoda here






Shoutout goes to @girlyscience-things

Miscellaneous Theropods not examined here that do not have further placement (links added as I do posts on them): 








Dilophosaurus, Giganotosaurus, Daemonosaurus & Herrerasaurus - An other experiment using photographic landscape backgrounds, possibly similar to the habitats these dinosaurs lived in. (These photographic backgrounds have been sourced from Google)