Echinognathus
Encyclopedia
Echinognathus is a genus of prehistoric eurypterid
in the Family Megalograptidae
. Echinognathus is known from the Ordovician
.
s with ovate to triangular scales. The prosoma (head) was subquadrate, with a tonguelike anterior process bearing marginal spines, and compound eyes on the top front of the head. The chelicerae (claws in front of the mouth) were small and short. The first and third pairs of walking legs were short, with diverging or closely spaced spines. The second pair of walking legs was enormously developed, with long paired spines. The fourth pair of walking legs was nearly spineless. The preabdomen
, the front portion of the body, was narrow with axial furrows, while the postabdomen was moderately narrow with broad, flat and curved appendages on the last body segment. The telson
was short and lanceolate.
Echinognathus is distinguishable from other members of the family by the third walking legs, which are characterized by long, closely set spines.
Eurypterid
Eurypterids are an extinct group of arthropods related to arachnids which include the largest known arthropods that ever lived. They are members of the extinct order Eurypterida ; which is the most diverse Paleozoic chelicerate order in terms of species...
in the Family Megalograptidae
Megalograptidae
Megalograptidae is a family of extinct eurypterids.-Description:Megalograptids were characterized by large exoskeletons with ovate to triangular scales. The prosoma was subquadrate, with a tonguelike anterior process bearing marginal spines, and compound eyes on the top front of the head. The...
. Echinognathus is known from the Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
.
Description
Megalograptids were characterized by large exoskeletonExoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
s with ovate to triangular scales. The prosoma (head) was subquadrate, with a tonguelike anterior process bearing marginal spines, and compound eyes on the top front of the head. The chelicerae (claws in front of the mouth) were small and short. The first and third pairs of walking legs were short, with diverging or closely spaced spines. The second pair of walking legs was enormously developed, with long paired spines. The fourth pair of walking legs was nearly spineless. The preabdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
, the front portion of the body, was narrow with axial furrows, while the postabdomen was moderately narrow with broad, flat and curved appendages on the last body segment. The telson
Telson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...
was short and lanceolate.
Echinognathus is distinguishable from other members of the family by the third walking legs, which are characterized by long, closely set spines.