Gasosaurus

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Saurischia

Family: Avetheropoda

Genus:Gasosaurus

Species:Gasosaurus constructus

Introduction

Gasosaurus is a mid-sized theropod that roamed the central Asian continent during the Middle Jurassic period (174–163 million years ago). Very little is known about this dinosaur. To date, only the one original specimen of Gasosaurus constructus has been located in the Lower Shaximiao Formation of Sichuan, China. This incomplete fossil record has limited the information that scientists can determine about this species.

Classification

Scientists use two primary methods to organize organisms into different groups. Linnaean taxonomy, also called “systematics,” groups organisms in a hierarchical fashion according to overall physical similarity, while an alternate system called “cladistics” attempts to create groups that better reflect the evolutionary relationships between species. The more shared evolutionary novelties they have, the more likely it is that they also shared a common ancestor, placing them in the same clade.

Traditionally, dinosaur classification groups dinosaur species in one of two orders, Ornithischia (or bird-hipped dinosaurs) or Saurischia (or lizard-hipped dinosaurs). Surprisingly, it is from the lizard-hipped dinosaurs, and not the bird-hipped dinosaurs, that modern day birds evolved. This is a very good example of convergent evolution, whereby the backward pointing pubis seen in ornithischian dinosaurs and birds actually evolved separately.

Gasosaurus is considered a saurischian and further placed in the suborder Theropoda. The bipedal, mostly carnivorous theropods are considered to be the most diverse and oldest dinosaur group to have ever existed. Theropod species first appeared during the Late Triassic period about 230 million years ago and survived until the end of the age of dinosaurs at the end of the Late Cretaceous period about 66 million years ago. Cladistic analysis generally places Gasosaurus in the largest and most advanced theropod clade, Tetanurae, which first appeared in the fossil record during the Early Jurassic period (201–164 million years ago). All Tetanurae species are characterized by their “stiff tails” and are considered more closely related to birds than to ceratosaurus (“horned lizards”).

Further classification of Gasosaurus is highly uncertain, in part because very few specimens have been retrieved and in part because its features suggest a very basal position within Tetanurae. It is sometimes placed within the Avetheropoda clade, which includes the “bird-like” dinosaurs (Allosauridae, Coelurosauria, and Carnosauria). Some researchers believe that Gasosaurus is a basal coelurosaur (one of the oldest ever described) while others believe it to be a carnosaur or perhaps a common ancestor between the two. It has also been speculated that Gasosaurus and Kaijiangosaurus are actually the same species. Until more remains are found, classification of this species remains unsettled.

Anatomy

Despite the fact that very few remains have been recovered, including no skull, Gasosaurus anatomy is considered to follow the characteristics of all bipedal theropods. As such, it is thought to have possessed a large head and an impressive jaw, as well as long, serrated teeth, a deep chest, and a long, tapering tail.

Like all lizard-hipped bipedal theropods, Gasosaurus possessed a backwards-facing pubis and extremely long and powerful rear legs, which ended with three or four clawed toes on each foot. Despite having such muscular hind limbs, as with most theropods, the forearms of Gasosaurus were greatly reduced, with limited usefulness and function, and ended with only two or three claws on each hand.

Intelligence

Scientists have used encephalization quotient (EQ), based on brain and body size, to estimate animal intelligence. Although a skull is yet to be recovered, based on related species, Gasosaurus was likely at the higher end of dinosaur intelligence with an EQ score falling between 1.0–1.9. In general, carnivorous dinosaurs are thought to have possessed higher intelligences than their herbivorous cousins. This is believed to be related to the carnivores' need for greater cognitive capability and behavioral flexibility to successfully hunt.

Reproduction and Population

Theropod species are among the oldest and most diverse of dinosaur groups. They were widely distributed and have been found on almost all continents, although Gasosaurus appears to have a distribution limited to central China. Despite such success, incomplete fossil records make it very difficult to estimate past population numbers of prehistoric animals.

While no nesting sites have been uncovered, it is believed that Gasosaurus was oviparous, like most dinosaurs. Females would have laid several eggs at a time, although egg-laying methods appeared to differ from species to species, such as using nests, underground burial, and perhaps even brooding. While post-hatching parental care behavior is considered possible, even probable, for some dinosaur species, evidence remains uncertain in the case of Gasosaurus.

Diet

Like most theropods, Gasosaurus was a carnivorous species that would have preyed on the small- and mid-sized herbivore dinosaurs that existed in what is now central China, including the stegosaur Huayangosaurus and the ornithopod Xiaosaurus. Although no skull of Gasosaurus has yet been recovered, it is considered likely that this species used its sharp serrated teeth to “grip-and-rip” prey, known as the “puncture-pull” feeding hypothesis.

There is still much debate regarding the feeding behavior of many carnivorous theropods, such as Gasosaurus. Although the question remains as to whether this species was an active hunting predator or an opportunistic carrion scavenger, most paleontologists believe that it was probably both when required.

Behavior

Fossil records are often incomplete, particularly so for Gasosaurus, which was named from only one partial skeleton, from which is it almost impossible to elucidate social behavior. Given the paucity of fossils recovered, very little is understood regarding the behavior of Gasosaurus. Currently, no nest sites or group burials have been located, which makes it difficult to determine whether this species exhibited social interaction, lived in groups or was solitary, or whether parents provided pre- or post-hatching care of offspring. Such difficulties often lead to scientific hypotheses based on the behavior of extant animals that share a similar ecological niche to extinct species.

It is considered likely, however, that Gasosaurus would have exhibited similar behavior to other closely related theropods, including possible pack hunting.

Habitat and Other Life Forms

With a lack of polar ice caps, the Jurassic period (201–146 million years ago) experienced much higher sea levels and a warmer climate than seen today. The warm wet climate of the Middle Jurassic created an abundance of lush landscapes covered with ancient gymnosperms such as ferns, cycads, and mosses, and large tree species such as Ginkgoes and conifers. During the Middle Jurassic, the supercontinent Pangaea had already commenced its separation into the continents of Laurasia and Gondwana. This process, known as continental drift, resulted in an increase in flooded areas and distribution of the temperate and tropical forests favored by prey species of Gasosaurus in what is now central China.

Gasosaurus roamed the Asian landscape during the Middle Jurassic period. It lived alongside sauropod species, such as Protognathosaurus, Shunosaurus, Datousaurus, and Omeisaurus; basal stegosaurs, such as Huayangosaurus; and the ornithopod Xiaosaurus, all of whose remains have been found in the Shaximiao Formation in Sichuan. It is likely that the mid-sized Gasosaurus preyed upon many of these herbivores.

Research

In 1985, a postcranial (the bones beneath the skull) dinosaur skeleton was discovered by a Chinese gas mining company in the Lower Shaximiao Formation of Sichuan. The remains were examined and described by Dong Zhiming, a paleontologist from the Beijing's Institute of Vertebrate Paleontology and Paleoanthropology, and were named Gasosaurus constructus after the construction site it was found in.

Although excavation continues, no other remains of this species have been formally described. Further research on Gasosaurus has largely focused on classification, using known similarities and differences to other theropods to attempt to trace evolutionary relationships. In 2014 an internet hoax emerged about a supposed Gasosaurus egg hatching in a German museum; this was clearly false, as no such eggs had been discovered, and no fossilized egg could ever hatch.

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