Trigonotarbida Thomisus Onustus>>

The trigonotarbida, also known as palaeotarbus jerami were alive around c. 419 to 290 million years ago. They used to be found around the areas of North America, Argentina and also in Europe (same with the locations of the thomisus spider). In this report I will be discussing about why this particular species had become extinct, while talking about it's habitat, 4 structural adaptations and 1 behavioral adaptation.
Level
Classification
Kingdom
Animalia
Phylum
Arthropoda
Subphylum
Chelicerata
Class
Arachnida
Order
Trigonotarbida

Habitat of Trigonotarbida:
The trigonotarbida are found in countries such as Europe and North America, from what research has shown for previous climates in both Europe and North America are both linked to the changes that are made by the Atlantic Ocean. They would have a fairly steady climate throughout the whole year because they are fairly near the equator of earth, this would effect them directly because their hunting style is mainly to hunt on ground and to wait for their prey to come along, which is very similar to the Thomisus Onustus flower spider. Their specific hunting style may also be the reason of which lead them to be extinct. For most animals they would have some sort of way to be able to protect themselves from predators, and the reason for why Trigonotarbida spiders couldn't do so it would most likely be because they nearly have no sort of protection to help them escape the run from predators.
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Distribution of Trigonotarbida spiders in areas of blue and green (Figure 1)
As shown in (figure 1), you are able to see that North America and Europe are very close to each other, and at about 400 million years ago these two countries were once one big landmass. With the extreme climates that these species of spiders have to live in, they would also have to cope with the uneven land such as mountains and rockslides that were present at about 400 million years ago. Coping with the land would be an advantage for the spiders because they mostly live on land, with the extreme land masses they would be able to hide under the surfaces. The environment that they lived in was very green, and but it was also covered in a very dull coloured area (some parts), which would possibly lead to the dull colour of the spider itself, so as to camouflage itself better.
The trigonotarbida aren't as easily found when compared with modern day spiders, the reason for this is because there is a large amount of rocks that these spiders hide under. Therefore, they can only be spotted when the rocks and the environment around them were moved, this was a good advantage for the trionotarbida spiders because then would be able to hide under somewhere when they are being attacked.
The environment itself 400 million years ago was filled with forests and lakes that were closely packed together, which allowed the spider to travel from one plant to another, or to be able to attach it's spider webs on different plants. Hence the location that the trigonotarbida once lived in was very tropical and filled with green environments, and also having the rocks and mountains that are able to protect them for other animals that may be hunting them.
trigonotarbida.png
The trigonotarbida spider (Figure 2)


Adaptations:

Structural adaptation #1:
The body of this particular spider, has a hard and thick texture very similar to armor, which protects the spider while being attacked. Having such a body texture allows the trigonotarbida spider much more freely without being afraid about being eaten by other animals. The main advantage to this adaptation for this animal is that the environment that it's living in is very extreme, animal and flora wise. Animals that were main predators for the trigonotarbida spiders are frogs, it is also very important for them to be able to protect the abdomen with such texture because that is also where all the main organs are located at. It is very protective against flora because not all flora are safe to be around with, some may be poisonous which could've harmed the spider in various ways.

Structural adaptation #2:
The legs on this particular spider are very similar to to the salamanders, because they both are able to grow back body parts. Even though the length of the legs on the trigonotarbida aren't the same (as seen in figure 2), the good thing about this body part for them is that they can grow back even if they lose it. Without similar length legs, the spider might of have troubles with walking and traveling but whilst this is a bad thing, they wouldn't mind losing on of the uneven legs because they would always regenerate. This is an advantage towards the spider itself because only the outer shell of the body has a very protective armor, but on the other hand the legs are merely protectable. Most animals wouldn't be able to fully eat the spider because of the size of the spider (approximately as large as a hand), but on the other hand the other animals are able to move faster than the trigonotarbida spider which causes the fact that they lose their legs really often.

Structural adaptation #3:
Trigonotarbida eyes were located on the top of the head, which was in a very bad position considering the fact they mostly move forward and not up. Similar to most spiders, the trigonotarbida also had eight eyes, even though it may sound that having eight eyes their eyesight would be in a very good quality but because of the environment that the spiders were living in and also because of the locations of the eyes it caused the fact that trigonotarbida spiders had poor eyesight. Even though they have fairly poor eyesight, but because of the shape of the eyes they are able to see from above the top and across on a even surface. This meant that they couldn't be look down and forward and the same time, which would most likely mean that they are unable to notice possible meals that may pass them, which is similar with the thomisus onustus spiders side vision. Though this would be a disadvantage towards the trigonotarbida itself, it could also be an advantage because of the high levels of trees that cover the land during the time, it would be better for it to be able to see and notice what is on the top and attacking them.

Physiological adaptation #1:
It is known that spider's fangs are poisonous to it's preys and some are to human beings, for the trigonotarbida, they are poisonous only towards animals. These fangs are located on the very front of the head, which are shaped like fairly short legs, they are able to insert it into the prey because of the sharpness of the fangs and inject the poison into the animal. The poison then paralyzes the victim which then allows the spider to eat the victim slowly in it's own pace. The main advantage of this particular adaptation during it's time period was that it was able to poison animals or insects that were fairly larger than them, which made it easier for them to hunt for a meal.

Physiological adaptation #2:
The main uses of a spiders silk it to build a web to catch animals, and after catching the animal they are able to wrap the victim with the silk to completely kill it and drink all it's protein inside of that animal. The main advantage for the trigonotarbida to be able to spin webs is that they can link from tree to tree or plant to plant and be able to catch preys very easily, such as flies. This would be easily done because of the environment itself it covered with forests which is closely packed where a bird can jump from tree to tree and not needing to fly. On a large scale this kind of environment could be suitable for all sorts of animals, but particularly for animals such as a trigonotarbida which uses web spinning and pouncing on the prey as their hunting style.

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Close up on the spiders eyes and fangs (figure 3)


References:
Information and photos:

- How Spiders See the World - Australian Museum." Australian Museum - Nature, Culture, Discover - Australian Museum. Web. 21 June 2011. <http://australianmuseum.net.au/How-spiders-see-the-world>.

- "The Paleobiology Database." The Paleobiology Database. Web. 15 June 2011. <http://www.paleodb.org/cgi-bin/bridge.pl?a=basicTaxonInfo>.

- "Pleophrynus - Trigonotarbida - Arachnida." Arachnid Origins and Evolution. Web. 17 June 2011. <http://drjasondunlop.tripod.com/pj4.html>.