About Asaphus
| Scientific Name (Genus) | Asaphus |
| Meaning of Name |
Obscure one Derived from Greek 'asaphes' (obscure). Due to the shallow and obscure grooves of the carapace, which integrate the whole smoothly. |
| Classification | Trilobita - Asaphida - Asaphidae |
| Period | Early to Middle Ordovician |
| Sub-classification / Species Name |
Asaphus expansus (Type species) acuminatus broeggeri cornutus kowalewskii lepidurus punctatus raniceps *And many other species are known. |
| Year of Paper Publication | 1822 |
| Genus Name Publication |
Des corps organisés fossiles nommés trilobites. In Desmarest, Anselme-Gaëtan. Histoire naturelle des crustacés fossiles. Paris. by Brongiart, Alexandre, 1822. |
Features and Defense System of Asaphus
From Russia
My Collection
The genus Asaphus is a trilobite that flourished in the cold shallow seas of the paleocontinent Baltica (present-day Northern Europe to northwestern Russia) from the Early to Middle Ordovician period (about 485.5 million to 457.5 million years ago).
The most prominent feature of Asaphus is its smooth carapace (shell) called "effacement." The grooves on the cephalon (head) and pygidium (tail) are almost absent, forming an overall dome-like curved surface. This streamlined form and the step-like fine lines on the surface of the shell allowed it to burrow smoothly into the mud and calcareous sand of the seabed.
It also possessed a defense system to protect itself from predators such as large orthoconic cephalopods (relatives of the nautilus). It could take a "spherical defensive posture (enrollment)" by bending its thorax consisting of eight segments and perfectly joining its head and tail. Furthermore, on the ventral (belly) side of the shell, there were special projections and pores called the "Panderian organ." This acted as a stopper, firmly locking the rolled shell so it wouldn't shift or come off.
Periscope: The Competition of Evolution
In the genus Asaphus, we can observe evolution that changed the length of the stalk with eyes (eyestalk) depending on the era and the depth of the environment they lived in.
Asaphus lepidurus
From Russia
My Collection
Asaphus lepidurus is an old species that lived in the early Ordovician period (about 480 million years ago) among the genus Asaphus.
It had a nearly circular proportion with a body length and width of about 4.5 cm, and had standard eyes without specialized eyestalks. It is considered to be close to the common ancestor of many Asaphus species that later flourished in the Baltic region.
Type Species: Asaphus expansus
From Sweden
Collection of the National Museum of Nature and Science
The eyestalks of the type species of the genus Asaphus, Asaphus expansus (A. expansus), were not yet that long, and it had relatively standard compound eyes. Another feature of Asaphus expansus is the presence of a single tubercle on the back of the head.
The Pinnacle of Evolution: Asaphus kowalewskii
From Russia
My Collection
As time progressed, to hide deeper in the sand and mud, species appeared that stuck only their eyes upwards like a submarine's periscope. Standing at the pinnacle of this evolution is Asaphus kowalewskii (A. kowalewskii), which has extremely long eyestalks reaching up to 5 cm.
In the seabed of the same era, species with medium-length eyes and species with "visors" over their eyes to block sunlight coexisted. It is thought that they lived peacefully without competing for prey or living space by changing the "depth" they burrowed into.
Could they pull their long eyes into their bodies like a snail? The answer is "No." Because the eyes of trilobites, like the surrounding shell, were made of hard calcite, they could not be expanded or contracted by muscles at all. When attacked by predators and rolled up like a ball, they had the weakness (biomechanical trade-off) of leaving only their two long, slender eyes sticking out defenselessly.
Latest Research: The Debate Over the "Eyes" of Asaphus
The eyes of Asaphus were a type of compound eye called "holochroal eyes." Under a single cornea on the surface, very long, cylindrical lenses made of calcite were densely packed, forming a structure that efficiently gathered light.
In recent years, an intense debate has been taking place among paleontologists regarding the internal structure of the eyes of Asaphus. When a research team examined fossils using X-rays, they announced that "under the lenses, there remains a structure called 'crystalline cones' found in insects and crustaceans." If this is true, it would be a discovery showing that trilobites are close relatives of insects.
However, another research team argued against this. They claimed that "because the central part of the Asaphus lens is weak, it dissolved from the center during the fossilization process, and it is merely an illusion that happens to look conical." The debate continues today to unravel the mysteries of trilobite evolution.
It is the study of the processes (decay, weathering, dissolution, etc.) from when an organism dies until it is discovered as a fossil. Because the appearance of a fossil is not always exactly as it was when it was alive, this is a very important perspective in paleontology.
First Paper Description of Asaphus
Source: Des corps organisés fossiles nommés trilobites.
by Brongiart, Alexandre
In Desmarest, Anselme-Gaëtan. Histoire naturelle des crustacés fossiles. Paris: L.-T. Cellot.
Asaphus was first scientifically described in 1822 by Alexandre Brongniart in the paper "Des corps organisés fossiles nommés trilobites."
Alexandre Brongniart was a French chemist, mineralogist, and zoologist. He learned the chemistry of mineral and ceramic manufacturing at the Sèvres porcelain factory, and expanded his research to include geology and trilobites around Paris. He is also the founder of the National Ceramics Museum.
Asaphus Stamp and Fossil Gallery
