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Dec 24, 2019 The text of this page is licensed under the creative commons attribution noncommercial license version 30. Polyphemus from patten 1894 with his original labels note that our current understanding of the xiphosuran nervous system is different from pattens view in several aspects such as the primary olfactory organ or close parallels of the xiphosuran with the vertebrate brain. Science, 5th Unit 2 (part 1 - Vertebrates Animals created on @flowvella Science, 5th Unit 2 (part 1 - Vertebrates Animals - Screen 6 on FlowVella - Presentation Software for Mac iPad and iPhone FlowVella. Other arthropods are considered generalists, because they apparently tolerate a wide range of plant chemicals and feed on many different plant species. The association between monarchs and their milkweed (Asciepias) host plants is one of the most thoroughly investigated system of arthropod. Arthropods possess a hard, nonliving, exoskeleton that not only provides protection. Approximately two-thirds of all flowering plants are pollinated by insects, and soil and leaf-mold arthropods, which include insects, mites, myriapods, and some crustaceans (pill bugs), play an important role in the formation of humus from decomposed leaf litter and wood.

The Carboniferous Period of the Paleozoic Era began 354 million years ago. It lasted for about 64 million years, until 290 million years ago. The name “Carboniferous” came from the large amounts of carbon-bearing coal that was formed during the period.

In the United States, the Carboniferous is divided into two epochs. The Mississipian Epoch is the older third and the Pennsylvanian Epoch is the more recent two-thirds. A chart or timeline of the Carboniferous and its divisions would look like this:

Shifting Continents Create Mountains As Pangea Is Born
The large land masses of Euramerica and Gondwana continued to move toward one another and collide during the Carboniferous Period. Collisions meant some of the land uplifted into mountains.

These mountains had no plants covering them. During rainy seasons huge amounts of surface rock was washed into flood plains and deltas. Eurameica and Gondwana were working to form the large supercontinent Pangea that would be important during the next period of the Paleozoic Era.

Invertebrates Contribute To The Formation of Limestone
In the early part of the Carboniferous Period, the Mississippian Epoch, much of North America was covered by warm, shallow seas. The many animals living in these waters contributed their shells to the formation of limestone. There were so many crinoids living in these waters that they make up a big part of the limestone formation.

The Lophophorata
There were many bryozoans living in the shallow seas of the Carboniferous Period. Bryozoans are filter feeding animals that form colonies or attach to rock surfaces. Brachiopods covered the sea floor. These bi-valves look like clams, but are actually related to the bryozoans. Both are members of the phyla Lophophorata.

The Trilobites
The trilobite was less and less common during the early Carboniferous or Mississippian and was headed for extinction.

The Fish of The Carboniferous

The placoderms, or armored fish, that had ruled the Devonian seas, became extinct with the end of the Devonian period. They were replaced with fish that looked more like our modern fish. Many species of fish and sharks developed during the late Carboniferous.

The Pennsylvanian Epoch
In the middle and late Carboniferous Period, the land was rising up out of the waters. Some of this was because of the land masses moving toward each other and pushing the land upward, but it was also because of the thickening of the Earth’s crust. Two ice sheets over the South Pole also took a large amount of water out of the oceans and the water cycle.

More of the land was exposed to the air at this time. Both plants and animals had to adapt to the changing habitat. Short periods of drought brought on by the glaciers caused mass extinctions of the invertebrates that lived in the shallow seas. The shallow seas became swamps between the ocean and the dry land.
Plants Put The Carbon In Carboniferous
New plants developed in the warm, humid climate and swampy conditions of this period. Large trees covered with bark and huge ferns grew in the middle Carboniferous swamps. The plants gave off so much oxygen that the air had much more oxygen in it. This allowed plants and animals to reach sizes that are not known in today’s atmosphere. When the huge trees and ferns died, they fell into waters that did not have bacteria to help them decompose. These plants formed peat beds. Eventually, with the weight of layers and layers, these peat beds turned to coal. See samples of Coal Shale Fern Fossils from the Pennsylvanian Epoch for sale.

Amphibians And Reptiles of The Carboniferous Period

Land animals became more and more diverse as the land areas grew. Tetrapods were four-legged vertebrates that began to move onto the land in the late Devonian period. During the Carboniferous, more and more species of tetrapods evolved.

Some were early amphibians that began their lives in the water and later moved onto land. Some were early reptiles that developed leathery skin as they moved to the parts of land that were very dry. These early reptiles also developed leathery coverings for their eggs so the insides didn’t dry out while the baby inside developed.

Giant Insects
Insects also grew well in the humid and high-oxygen conditions. One of the largest was the Meganeura. This large ancestor of the dragonfly had a wingspan of 60 to 75 cm. Another large arthropod lived on the floor of the Carboniferous forests. The Arthropleura was a giant millipede that could grow to more than one and a half meters long. They sometimes had as many as 30 pairs of legs!

The End of The Carboniferous Period

The end of the Carboniferous period is marked by global climate changes due to the glaciers that covered the South Pole. The mass extinctions that mark the end of other geologic periods were not present, yet many species did go extinct during this time. The marine environments were most affected by these climate changes, so the extinctions were mostly invertebrates that spent their lives in the seas. Horn corals, trilobites and some forms of crinoids were on the road to extinction that would come in the next period,

Below is a video of what it may have been like in the Carboniferous Period. It is taken from the BBC's Walking with Monsters, First Life, and Prehistoric Park. It is about 3 minutes long.

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The largest phylum of creatures on Earth without a doubt is Arthropoda, both in terms of number of species and in total number of individuals. There are nearly 1 million species of Arthropods, with over 90% of them being insects. Of the remaining less than 10%, or about 85,000 species, there are only three major marine groups. The most well known is that of the mostly marine sub-phylum Crustacea (>30,000 species), the entirely marine class Pycnogonida, also called the 'sea spiders' (500 species) and the entirely marine class Merostomata, commonly called the horseshoe crabs (5 species).

All Arthropods share certain characteristics making them unique from other phyla. Most obvious is the external skeleton (technically, not really a shell). Not only does this exoskeleton protect the animal like a suit of armor, but it actually does serve as the animal's skeleton. The muscles of an Arthropod are connected to the inside of the exoskeleton, because the animal lacks an internal skeleton of any type.

The exoskeleton is made of a tough substance called chitin (KIE-tin). The animal secretes this hard material from cells in the underlying epidermis. Because the exoskeleton cannot grow, the animal must periodically shed its armor in order to grow. This process is called molting. The animal must first grow a soft exoskeleton underneath the principal exoskeleton. Then, the animal grows enough within the principal exoskeleton to crack it. The animal then crawls out of its old exoskeleton and allows the new soft one to grow and harden. New exoskeletons are usually too large for the animal at the time of the molt, and the animal must grow into the new exoskeleton. This allows reasonable time between molts. Immediately after an Arthropod has molted, it is quite vulnerable because it is essentially defenseless. During this period, the animal will hide and wait for its armor to harden. Lobsters caught during this period of time are sometimes called 'soft-shelled' because they feel noticeably soft.

The name Arthropod means 'jointed-foot.' In order for the Arthropod to move in such a rigid body, it has numerous joints in its exoskeleton. Like door hinges, they allow bending in only one direction, but are surprisingly well developed. A lobster is quite flexible when necessary, and can manage to rotate its claws sufficiently to pinch its captor.

Arthropods have what is called an open circulatory system. This means that unlike many other kinds of animals, they have no arteries, veins or capillaries to carry blood. Instead, blood is pumped through sinuses (open spaces) within the animal to reach the tissues.

Arthropods also have compound eyes. Most people know of the insect's compound eyes, and the other Arthropods' eyes are no different. Each eye is composed of many smaller light-sensitive organs, called ommatidia. Together, these ommatidia form a single working eye. The compound eye is not specialized so much for detailed sight as for the detection of motion.

The Sub-Phylum Crustacea

The crustaceans are probably best known as a source of food. Lobster, crabs and shrimp are all Crustaceans. Barnacles, amphipods, isopods, and copepods are also Crustaceans.

Crustaceans have five pairs of appendages. Usually the front pair, called Chelipeds, have claws on them, while the remaining four pairs are walking legs. In many species, the second and even the third pairs of legs have smaller pincers on them as well.

While some of the primitive Crustaceans have a single body piece, called a trunk, the more advanced forms (like lobster, crabs and shrimp) have the body divided into two regions: a cephalothorax (or thorax) and an abdomen. The cephalothorax (meaning 'head-body') is so called because it contains the 'head' as well as the main body organs. The abdomen (which many people erroneously call the tail), on the other hand, is mostly muscular. The abdomen is usually made up of 6 segments, each containing a pair of 'swimmerets' (small legs). In the male, the most forward pair of swimmerets are longer than the others, designed for inserting sperm into the female.

The last segment of the abdomen ends in a flattened section called the telson. The tailfan is composed of the telson and two flat appendages, called uropods, on each side.

Most Crustaceans are similar in appearance, with the most obvious exception of barnacles. The body form of the barnacle is Crustacean, but it isn't very obvious unless examined at the larval stage. There are about 900 different species of barnacles known. Barnacles contain special glands which produce a type of 'cement' which they use to glue themselves to rocks, ships, whales, docks and just about any other hard surface.

As barnacles grow, they create their own little 'houses,' called carina, which look like tiny volcanoes. These are made of calcium carbonate which the barnacles make by combining carbon dioxide with calcium extracted from the water. When a barnacle is young, it is a planktonic larva with no protective carina and may become a meal for a larger animal. It must find a suitable place to settle and grow before it can start to produce a carina. Barnacles get their food by waving an arrangement of limbs called 'cirri' in the water to catch drifting plankton. The cirri are present on even the larval barnacles--they are the legs. When the barnacle settles down to its adult form, it attaches itself to the substrate by the head and waves its legs to collect plankton.

The Class Merostomata

There are only five species contained within the Class Merostomata, and among those, only one is found in American waters. Commonly called the Horseshoe Crab (Limulus polyphemus), it is only found on the east coast of the United States, from the Gulf of Maine to the Gulf of Mexico. It is very common on Cape Cod. The animal is a tannish-brown color, but may accumulate algae growth, to look green in spots.

11.10: Arthropods - Biology LibreTexts

This creature (which, technically, is not really a crab at all, and is more closely related to the spiders and scorpions) has no relatives in the North Atlantic which look similar, and is therefore impossible to confuse with other Arthropods. Circa 1870, the horseshoe crab was given the name 'horse-foot crab,' which is a better description of its shape than 'horseshoe.' However, somehow the name became corrupted between then and now. It has a rounded ('horse-foot shaped') carapace, with a triangular abdomen and a long, slender tail called a telson. On Sir Walter Raleigh's expedition to the New World in 1584, naturalists Thomas Heriot and John White noted that the indians used the horseshoe crab's tail (connected to a reed or stick) as a spear tip to spear fish.

The mouth is on the underside of the animal and is surrounded by five pairs of walking legs. Each leg is heavily armed with spines on the inside edge of the largest segment. These spines are called gnathobases and are used to grind up food (usually worms, clams and other small invertebrates) before it is eaten.

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