Birds and Dinosaurs
Birds and Dinosaurs
By any reasonable definition, T. rex is more closely related to sparrows than to Stegosaurus . [Diagram showing that Stegosaurus came earlier than T. rex , along with it showing that T. rex came closer in time to sparrows. Evaluation criteria "separation by time", "phylogenetic distance" and "physical similarity" are highlighted in red.] Birds aren't descended from dinosaurs, they are dinosaurs. Which means that the fastest animal alive today is a small carnivorous dinosaur, Falco peregrinus . [A picture of two birds is shown.] It preys mainly on other dinosaurs, which it strikes and kills in midair with its claws. [In red:] This is a good world.

Birds are commonly considered to be a separate class of tetrapods . However, this classification is false according to phylogenetic taxonomy . Taking into account that birds developed around 150 million years ago out of small theropod dinosaurs, birds along with crocodiles are indeed the remaining representatives of the archosaur clade . This premise appeared also in comic 867: Herpetology .
This relation between birds and dinosaurs is depicted in the comic in a cladogram which shows that Tyrannosaurus rex is more closely related to the common sparrow than to Stegosaurus . Not only do the former share a phylogenetic branch, but T. rex also lived around 80 million years after Stegosaurus . The concurrence of both species in popular culture is a widespread error. T. rex is also much more alike to modern birds than to other dinosaurs in terms of anatomy. This relationship was pointed out on the Science journal the week of the comic.
The comic draws the conclusion that if birds must in fact be considered modern dinosaurs, the hunting practice of birds of prey (specifically, the Peregrine Falcon ) is consequently a dinosaur fight. For an inveterate dinosaur aficionado like Randall , this fact must make the modern world much more attractive.
The line "This is a good world." could also possibly refer to a famous scene from the pilot episode of the television series Firefly featuring two plastic dinosaurs in a somewhat philosophic dialogue. Randall is known to be a fan of the series .
The title text is a sidesweep to the webcomic Dinosaur Comics drawn by Ryan North , who stands 6'6.5" (199 cm) tall. At that page the title text of the comic strip from the same day refers to Randall and xkcd .
The conclusion of this comic is referenced in the title text of the last image in the Plastic Dinosaurs What if?
By any reasonable definition, T. rex is more closely related to sparrows than to Stegosaurus . [Diagram showing that Stegosaurus came earlier than T. rex , along with it showing that T. rex came closer in time to sparrows. Evaluation criteria "separation by time", "phylogenetic distance" and "physical similarity" are highlighted in red.] Birds aren't descended from dinosaurs, they are dinosaurs. Which means that the fastest animal alive today is a small carnivorous dinosaur, Falco peregrinus . [A picture of two birds is shown.] It preys mainly on other dinosaurs, which it strikes and kills in midair with its claws. [In red:] This is a good world.
