Deviation Actions
Description
Welcome to northwest Argentina about 231 million years ago. This about the middle of the Triassic period. Much of the world has recovered from the Great Dying that marked the end of the Permian and the start of the Triassic. Argentina is still part of the one great continent called Pangaea, but this great landmass is showing signs now of breaking apart with what will become North America, Europe, Eurasia and Asia in the earliest beginnings of forming the northern continent of Laurasia while the lower continent formed of South America, Africa, India, Australia and Antarctica will become known as Gondwanna.
Herrerasaurus is one of the earliest dinosaurs of all. There are a couple others that may be older, but all these early ones border on the definition of what makes a dinosaur. Certain characteristics fall just outside, but generally most aspects of the bone structure fall into general categories of dinosaur. These variations have made it difficult to put Herrerasaurus into a particular family. As of now, most agree it is a carnivore and early, if not the first, theropod dinosaur. Theropods would evolve many forms of meat eating dinosaurs, birds and a small group that would give up meat and return to eating plants.
Herrerasaurus was about 20 feet long from nose to tail tip and 5 ½ feet tall at the hip. Herrerasaurus had a flexible joint in the lower jaw that could slide back and forth to deliver a grasping bite. This cranial specialization is unusual among dinosaurs but has evolved independently in some lizards. The jaws were equipped with large serrated teeth for biting and eating flesh, and the neck was slender and flexible.
The forelimbs of Herrerasaurus were less than half the length of its hind limbs. The upper arm and forearm were rather short, while the hand was elongated. The first two fingers and the thumb ended in curved, sharp claws for grasping prey. The fourth and fifth digits were small stubs without claws.
Herrerasaurus was fully bipedal. It had strong hind limbs with short thighs and rather long feet, indicating that it was likely a swift runner. The foot had five toes, but only the middle three (digits 2, 3, and 4) bore weight. The outer toes (1 and 5) were small; the first toe had a small claw. The tail, partially stiffened by overlapping vertebral projections, balanced the body and was also an adaptation for speed.
Herrerasaurus still lived among giant rausuchians like Saurosuchus and the large reptile/mammals the dicynodonts like Kannemeyeria. Other early Sauropodomorphs lived in this formation as well, but they were small and two legged, bearing little resemblance to the Titanosaur to come some 100 million years later. Panphagia, seen here, were small bipedal animals that bore teeth indicating they were probably omnivores. It is likely they were transitioning from a meat eating diet to an herbivorous diet. By this time, the age of dinosaurs had truly begun.
