Related Experiment Video
Updated: Jul 6, 2026
06:36
A Novel Tenorrhaphy Suture Technique with Tissue Engineered Collagen Graft to Repair Large Tendon Defects
Published on: December 10, 2021
Evolution of Complexity in Paleozoic Ammonoid Sutures
1Department of Geology, Bryn Mawr College, Bryn Mawr, PA 19010, USA. Cincinnati Museum Center, Geier Collections and Research Center, Cincinnati, OH 45202, USA. Paleontological Research Institute, Russian Academy of Sciences, Profsoyuznaya 123, 117647 Moscow, Russia.
Science (New York, N.Y.)
|October 26, 1999
Summary
Paleozoic ammonoids exhibited a significant increase in septal suture complexity over 140 million years. Despite mass extinctions, a long-term evolutionary trend favored greater complexity in these marine invertebrates.
Area of Science:
- Paleontology
- Evolutionary Biology
- Marine Biology
Background:
- Ammonoids, an extinct group of marine cephalopods, are important index fossils for the Paleozoic and Mesozoic eras.
- Their complex shell structures, particularly septal sutures, provide a record of evolutionary change.
- Understanding trends in ammonoid evolution can offer insights into broader evolutionary patterns.
Purpose of the Study:
- To quantify the long-term trend in septal suture complexity in Paleozoic ammonoids.
- To investigate the role of ancestry and extinction events in shaping evolutionary complexity.
- To determine if there is an inherent bias towards increased complexity in ammonoid evolution.
Main Methods:
- Analysis of septal suture complexity in 588 genera of Paleozoic ammonoids spanning 140 million years.
- Comparison of complexity between 475 ancestor/descendant pairs.
- Examination of complexity trends within 12 specific subclades (373 genera).
Main Results:
- A 1600% increase in mean septal suture complexity was observed over 140 million years.
- Descendants were over twice as likely to be more complex than their ancestors.
- Twelve subclades showed an average increase of 34% in complexity.
Conclusions:
- The data suggest a long-term bias or driven system favoring increased complexity in ammonoid evolution.
- Mass extinctions acted counter to this trend, often eliminating more complex forms and resetting evolutionary trajectories.
- Evolutionary trends can be influenced by both intrinsic biases and extrinsic factors like extinction events.
More Related Videos
Related Concept Videos
01:26Joints
Joints, also called articulations or articular surfaces, are points at which ligaments or other tissues connect adjacent bones. Joints permit movement and stability, and can be classified based on their structure or function.
Structural joint classifications are based on the material that makes up the joint as well as whether or not the joint contains a space between the bones. Joints are structurally classified as fibrous, cartilaginous, or synovial.
Fibrous Joints Are Immovable
The bones of a...
Structural joint classifications are based on the material that makes up the joint as well as whether or not the joint contains a space between the bones. Joints are structurally classified as fibrous, cartilaginous, or synovial.
Fibrous Joints Are Immovable
The bones of a...
02:06Conditions on Early Earth
Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.
01:22Sutures of the Skull
The human skull is composed of several bones that come together to protect the brain and support the structures of the face. The junctions where these bones meet are called sutures.
Sutures are immobile joints between adjacent bones of the skull. The narrow gap between the bones is filled with dense, fibrous connective tissue that unites the bones. The long sutures located between the skull bones are not straight but instead follow irregular, tightly twisting paths. These twisting lines tightly...
Sutures are immobile joints between adjacent bones of the skull. The narrow gap between the bones is filled with dense, fibrous connective tissue that unites the bones. The long sutures located between the skull bones are not straight but instead follow irregular, tightly twisting paths. These twisting lines tightly...
01:03Structural Joints: Fibrous Joints
Fibrous joints are a type of joint where the bones are connected by fibrous connective tissue. These joints provide stability and minimal to no movement between the articulating bones. There are three types of fibrous joints.
Suture
All the bones of the skull, except for the mandible, are joined to each other by a fibrous joint called a suture. The fibrous connective tissue found at a suture strongly unites the adjacent skull bones and thus helps to protect the brain and form the face. In...
Suture
All the bones of the skull, except for the mandible, are joined to each other by a fibrous joint called a suture. The fibrous connective tissue found at a suture strongly unites the adjacent skull bones and thus helps to protect the brain and form the face. In...
01:17Structural Joints: Cartilaginous Joints
As the name indicates, at a cartilaginous joint, the adjacent bones are united by cartilage, a tough but flexible type of connective tissue. Unlike synovial joints, these types of joints lack a joint cavity and involve bones joined together by either hyaline cartilage or fibrocartilage.
There are two types of cartilaginous joints:
Synchondrosis
A synchondrosis ("joined by cartilage") is a cartilaginous joint where bones are connected by hyaline cartilage. Synchondrosis may be temporary or...
There are two types of cartilaginous joints:
Synchondrosis
A synchondrosis ("joined by cartilage") is a cartilaginous joint where bones are connected by hyaline cartilage. Synchondrosis may be temporary or...
01:20Structural Classification of Joints
Joints, also known as articulations, are classified based on their structural characteristics, i.e., based on whether the articulating surfaces of the adjacent bones are directly connected by fibrous connective tissue or cartilage, or whether the articulating surfaces contact each other within a fluid-filled joint cavity. These differences serve to divide the joints of the body into three structural classifications.
A fibrous joint is where the adjacent bones are united by fibrous connective...
A fibrous joint is where the adjacent bones are united by fibrous connective...