Proganochelys

**__The Proganochelys__** Back to Modern Animal >>  The // Proganochelys quenstedti // is the second oldest turtle species discovered to date. The Triassic turtle (refer Figure 1) is dated to approximately 210 million years ago. Fossils of the omnivorous species were found in Thailand and Germany. In stance and basic shape it appears as modern turtles and tortoises do today, yet it sports many differences.

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 * General Information **
 * Scientific Classification **
 * ** Level ** ||||  ** Classification **  ||
 * Kingdom ||||  Animalia  ||
 * Phylum ||||  Chordata  ||
 * Class ||||  Sauropsida  ||
 * Order ||||  Testudines  ||
 * Family ||||  Proganochelidae
 * Genus ||||  Proganochelys  ||
 * Species |||| P. Quenstedti ||

** Global Location ** The Proganochelys existed during the Triassic period, and lived in the giant continent Laurasia. Fossils of the Proganochelys have been located in Germany and Thailand (refer Figure 2). Presumably, this was where the animal resided, and possibly anywhere in between.
 * Habitat **

**Habitat Description** During the Triassic Period, Laurasia was primarily dry and warm and especially arid inland. However, during the Triassic Period the earth began to experience more seasonal changes, which directly affected the land, such as monsoon weather cycles.

**Specific Habitat of the** ** Proganochelys ** The Proganochelys shared its environment with a variety of dinosaurs. It is suggested that the Proganochelys lived near small bodies of water such as ponds but was mainly earthbound. Evidence that suggests that the Triassic turtle spent most of its time on land is the fact that it carries behind it a heavy spiked tail tipped with a club.

** Adaptations **

**Structural Adaptation – Spikes On Neck** Considering the Proganochelys has the inability to retract into its shell, its neck is left out in the open and vulnerable to predators. But // Proganochelys quenstedti // has found a way to counter this. The Triassic turtle houses spikes on its neck and head (refer Figure 3), protecting itself from any dinosaur or mammal predators. The neck is an extremely exposed part of most animals, especially the slow moving Proganochelys, and is generally where predators can strike a deadly blow. The Proganochelys needs strong defences on its neck to ensure survival. Those born without them, or not as fully developed would have been easier prey and, through the process of natural selection, would have died out. The environmental pressure for this adaptation would have been the turtle’s relocation from water to land, and placing it in danger from a new group of land predators.

**Structural Adaptation – Tail Structure** Another defence mechanism of the Proganochelys is its tail. The tail is longer than modern day turtles and tortoises, is lined with spikes and has a club at the end (refer Figure 3). The purpose of this defence system and weaponry would be to defend against any predators and then have the ability to fight them off. Also possibly to immobilize or kill any prey.

Again, the environmental pressure to develop this tail structure would be the range of predators it is susceptible to on land – particularly carnivorous dinosaurs. The tail development ensured a higher rate of survival for those who had it by reducing the risk of being seriously injured, fighting of would-be predators, and immobilizing prey to kill and eat it.

** Structural Adaptation – Shell ** Currently, the oldest turtle known is the // Odontochelys semitestaceai //, which existed about 220 million years ago//.// This animal lived in the ocean and had only a shell on its underside. This part of the shell is known as the plastron. The Proganochelys has a shell on both top (called the carapace) and bottom (plastron). This suggests that within the space of about 10 million years, the Proganochelys developed a solid full-body shell (refer Figure 3).

The purpose of the shell is, again, defense. This vast array of defenses suggests the Proganochelys had quite a problem with predators – either an extensive range of them or only a few, main, serious predators. But the solid defense provided by the shell would deter predators from biting at its body as this may damage the attacker’s teeth. The shell, acting as a defense and a deterrent would increase the chance and rate of survival of the Proganochelys. This adaptation also supports the theory that the Proganochelys spent most of its time on land, as the heavy tail would be inadequate for swimming. ** Structural Adaptation – Mouth (Beak and teeth) ** The Proganochelys has a slightly different mouth to that of modern day turtles and tortoises. The ancestral Odontochelys had fleshy mouths with teeth, and modern day turtles have a particular type of beak. The Proganochelys was half way between. Its beak was beginning to develop, and it only had teeth on the top of its mouth – the palate (refer Figure 3). This adaptation suggests that the Triassic turtle went from carnivorous, or possibly omnivorous (but primarily meat-eating), to herbivorous, or possibly still omnivorous but primarily eating plants. The beak helps in grasping and slicing up vegetation while the teeth help grind up meat. In a new environment (land), the ability to eat both vegetation and meat gives the turtle the flexibility required to further adapt and survive in an unfamiliar and different environment than its ancestors lived in.

** Behavioural Adaptation – Emerging from ocean to live on land ** Around 250 million years ago, the earth’s environment began to drastically change, especially in the oceans. A mass extinction occurred during this time, wiping out incredible amounts of animals, particularly marine life. Researchers are yet to accurately discover what caused the mass extinction, but most signs point to mechanism in the ocean such as volcanic activity, changes in sea level, shifts in ocean circulation, and the sudden release of methane hydrate.

These global changes may have forced the Odontochelys onto land, which then became the Proganochelys. It may have moved for food, as its prey may have begun to die off during this mass extinction, or to escape the fate that other species had met at the hands of Mother Nature. Either way, moving onto land greatly benefited the Proganochelys as it quickly adapted to a new environment of resources such as food and fresh water, and survived the mass extinctions of marine and terrestrial life.

** Selection Pressure ** Currently, little is know about the existence of the Proganochelys. This prehistoric turtle lived over 200 million years ago, and currently scientists have almost no idea when it died out completely. Two possible reasons for the extinction of the // Proganochelys quenstedti //were that it was wiped out during a minor extinction during the Jurassic Period (approximately190 millions years ago) that killed many species that lived close to water, or shallowed-water creatures due to massive methane deposits being released from the earth. And then there is the possibility that it survived long enough to see the end of the dinosaurs, in which it too was wiped out in that mass extinction.

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 * **Bibliography**
 * All About Reptiles. //Oldest Fossil Land Turtle//. Retrieved June 26th, 2011, from http://www.all-about-reptiles.com/land-turtle.html
 * Enchanted Learning. //Dinosaur and Paleontology Dictionary//. Retrieved June 27th, 2011, from http://www.enchantedlearning.com/subjects/dinosaurs/glossary/indexp4.shtml
 * Wikipedia. //Proganochelys.// Retrieved June 26th, 2011, from http://en.wikipedia.org/wiki/Proganochelys