Table of Contents
What are articulate brachiopods?
Rhynchonelliform (articulate) brachiopods Rhynchonelliform brachiopods have shells made calcium carbonate and interlocking pegs (teeth) and sockets that form a hinge between the valves. The teeth are in one valve (the pedicle or ventral valve) and the sockets are in the other (the brachial or dorsal valve).
What are the two major groups of brachiopods?
Historically brachiopods have been divided into two classes: Articulata and Inarticulata. This is in reference to how the two shells are joined.
What would be the best classification of brachiopods in terms of body symmetry?
Brachiopods have a plane of symmetry that cuts across the two valves. This you can think of if someone to cut your body in half down the middle, each side would have an eye, arm, and leg that matches the other side.
What is unique about brachiopods?
Unique to brachiopods is the fleshy, stalk-like pedicle, which some groups use to attach to hard substrates. Although rarely preserved itself, brachiopod shells will often have a pedicle opening preserved along the hinge-line called the pedicle foramen.
What is the genus of a brachiopod?
The brachiopod genus Lingula has the distinction of being the oldest, relatively unchanged animal known. Modern brachiopods generally live in areas of cold water, either near the poles or in deep parts of the ocean.
Which group of brachiopods is still living today?
Order Rhynchonellida (Ordovician to Recent) They were also the first brachiopod group to be completely astrophic. Rhynchonellids are one of the three brachiopod orders that are still alive today!
How do you identify a brachiopod?
Other shell features are useful for identifying brachiopods. A sulcus (a groove-like depression) is present on many brachiopod shells, and a fold (a raised ridge) can be found on the opposite valve. Costae are elevated ribs on the shell. Growth lines are concentric rings representing successive periods of growth.
What species is brachiopod?
Brachiopods are marine animals that, upon first glance, look like clams. They are actually quite different from clams in their anatomy, and they are not closely related to the molluscs. They are lophophorates, and so are related to the Bryozoa and Phoronida.
What are brachiopods made of?
Each valve consists of three layers, an outer periostracum made of organic compounds and two biomineralized layers. Articulate brachiopods have an outermost periostracum made of proteins, a “primary layer” of calcite (a form of calcium carbonate) under that, and innermost a mixture of proteins and calcite.
How many species of brachiopods are there?
There are some 30,000 fossil brachiopod species known, but only around 385 are alive today. They are found in very cold water, in polar regions or in the deep sea, and are rarely seen.
Where did the brachiopod come from?
Their fossils are common in the Pennsylvanian and Permian limestones of eastern Kansas. Brachiopods have an extensive fossil record, first appearing in rocks dating back to the early part of the Cambrian Period, about 541 million years ago.
What is the classification of brachiopods?
With very few living representatives, brachiopod classification has primarily come from a paleontological perspective, with substantial consideration given to the morphology of the shell. Traditionally, brachiopods have been separated into two major groups: the Inarticulates (brachiopods with phosphatic shells) and Articulates (everything else).
What is the difference between articulate and inarticulate brachiopods?
The articulate brachiopods have toothed hinges and simple opening and closing muscles. The other group called the inarticulate or ‘lingulates’ do not join at the hinge, but instead have a complex network of muscles to open and close the valves
What is an articulate brachiopod valve?
Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major groups are recognized, articulate and inarticulate. The word “articulate” is used to describe the tooth-and-groove features of the valve-hinge which is present in the articulate group, and absent from the inarticulate group.
Where does the brachiopod body occupy only one third of its volume?
The brachiopod body occupies only about one-third of the internal space inside the shell, nearest the hinge. The rest of the space is lined with the mantle lobes, extensions that enclose a water-filled space in which sits the lophophore.