In the last issue we talked about the splendor of the heavy cavalry nautilus in the Ordovician (miss the little buddy click here!). ), allowing cephalopods to have their first golden age. However, just as the armored cavalry was eventually eliminated because of their clumsiness and cost, the "iron floating" nautilus was also in decline in the face of the mass extinction in the late Ordovician and the vertebrates with jaws evolved in the Silurian period. However, the cephalopods did not concede defeat, and they continued to improve themselves, like the Mongol cavalry, the final form of the cavalry in history, casting the last glory of the armored warrior before the advent of the age of firearms.
In the name of chrysanthemum, ammonites, born in the Devonian period, the paradise of fish, will launch a decisive challenge to the newborn overlord vertebrates for more than 300 million years, when the ocean world must be "full of golden armor".
Warrior, A is on top
Ammonite was born in the Devonian period. The nova cephalopods improved the armor of the Nautilus ancestors, which was no longer dominated by straight pagodas, but instead curled and coiled, which guaranteed maximum flexibility during swimming. At the same time, the next door began to curl and deform, which gave ammonite an unusually complex and beautiful suture, and the complexity of the late suture line even needed to be seen clearly with the help of a magnifying glass (Figure 1). The sutures of ammonite are also divided into goniatitic, ceratitic and ammonitic (Fig. 2) according to their shape, which is a major fossil feature that classifies ammonite and distinguishes it from other cephalopods.
Fig. 1 Beautiful ammonite sutures
(Source: Tianmu Dixue, Shan Huachun)
Fig. 2 Ammonite suture changes
(Source: Hui Shifen Museum, University of Hong Kong)
This complex and anomalous next-door structure makes ammonite armor more resistant to pressure, in addition to being able to withstand greater water pressure in addition to being able to resist threats from predators. At the same time, the complex folds of the next door make the soft body of the ammonite and the hard part of the next door more tightly combined, thereby improving its own stability. These targeted changes have led to increased ammonite flexibility and compressive resistance. Like the Mongol cavalry in history, the flexibility of the cavalry was maximized, pressing the iron can knights of the same era of Europe to the ground and constantly rubbing, and also beating the JinGuo, who once had the iron floating slaughter, completely powerless.
Ammonite restoration (Source: NobuTamura)
In addition to the change in shape, ammonite also further thickens the surface of its shell, and some thicken and thicken the growth pattern to form a growth rib, which looks like a blooming chrysanthemum (Figure 3), hence the name ammonite. Others have thorns and tumors on their shells (Figure 4) that look more powerful and strange. There is even the beautiful pancai armor (Fig. 5), which is recognized as a gemstone by the International Jewelry Federation because of the structural color of aragonite on the surface of the shell.
Fig. 3 Ammonites like chrysanthemums
(Source: Tianmu Dixue, Shan Huachun )
Fig. 4 Barbed ammonites nolani
(Source: Wiki-media: author Teresa Martin)
Fig. 5 Ammonite of honor guards in ammonite
(Source: Taken by the author)
The change of ammonite shell is a bit like the leather armor process in Chinese history, brushing a thick layer of paint on the leather armor made of it, which not only enhances the defensive ability, but also anti-corrosion and beauty, so the scenes of the ancient great legions fighting are mostly black and red seas of people. (Although the raw lacquer is initially milky white, it will darken into a maroon shell color after oxidation, and it is basically not obvious to add other pigments, so red and black are the mainstream colors of lacquerware and leather armor, Figure 6). And if we return to the oceans of the Mesozoic Era, we may see the most ornate parade of colored honors of the Ammonite Army shining in glittering and glowing in the sea.
Figure 6 Above: Leather armor excavated from the tomb of Marquis Yi of Zeng (Source: see watermark)
Below: Colorful Terracotta Warriors and Horses of Qin Shi Huang (Source: Qin Shi Huang Emperor Mausoleum Museum official website)
Get up wherever you fall
After the vertebrates had their jaws, they began to suppress the heavy armor of mollusks and arthropods. Under pressure, many taxa could only turn to a second battlefield, such as the arthropods that once dominated the Cambrian Period, successfully followed the plants to land, and even dominated the sky first. The good brothers of cephalopods , gastropods ( most recently related to cephalopods in molluscs ) also landed and formed their own army. Although the vertebrates were later chased and killed, and killed in the land and air realms, that was another story.
However, this escapist spirit of lying down wherever you fall does not seem to affect our cephalopods at all, and they are bent on fighting the vertebrates to the end in the ocean, and this deep-rooted thinking of naval warfare has created the indomitable demonic spirit of cephalopods.
Ammonite with new armor began to gradually replace its old ancestors, the Nautilus, to join the marine war, more flexible hands and changeable armor so that ammonite is no longer a heavy cavalry iron knot waiting to die, but a light cavalry that comes and goes like the wind and has a certain degree of defensive power, just like the Mongol cavalry Great Leap Forward Conquest War, and soon ammonites began to occupy a large area of marine space, experiencing the first golden period in the Late Paleozoic (Devonian to Permian). They are numerous and evolve very quickly, so they are often compared to strata.
The rise of ammonites soon attracted the attention of vertebrates, some of which specialized their jaw weapons and appeared as a super "can opener" (Figure 7), but this did not make ammonite retreat, but became more and more courageous. Until the end of the Permian, the greatest extinction of the all-geological epoch arrived, the loss of marine species reached more than 95%, and the biological world was ruthlessly cleansed by Mother Earth, and ammonite was no exception. The first golden age of ammonites ended, and with the downturn of ammonites, those specialized can openers also went to extinction.
Figure 7 Above: The can opener spiny shark that once went to the ocean
(Source: prehistoric-wildlife.com)
Bottom: The spiny tooth shark pulls the ammonite flesh out through the opening and closing of its teeth
(图源:Ramsay et al., 2014)
Heroes in the chaotic world, many straw bags in the prosperous world
You think that's the end of the story? No, ammonite lets us know what is called "a hundred-footed worm, dead but not stiff". At the beginning of the Triassic period after the Great Purge, when nature had not yet fully recovered, ammonites began to appear in the strata of the Early Triassic, and together with bivalves became one of the earliest revived marine organisms.
In the immediate Mesozoic Era, although everyone was familiar with the vertebrate thing. Dinosaurs and pterosaurs can't do it on land and in the sky, and monsters are rampant in the ocean. Ichthyosaurs, plesiosaurs, and dragons tumble into the sea. However, ammonites continued to flourish in the oceans since the beginning of the recovery, and the entire Mesozoic Era was not at all inferior in the face of the huge vertebrates.
Ammonite, dressed in beautiful armor, truly achieved "golden armor all over the city", and its prosperity also gave the Mesozoic Era the nickname of "Ammonite Age" in addition to the "Age of Dinosaurs" (Figure 8). However, the comfortable prosperity made the ammonite a little floating, and some non-mainstream ammonites began to fly themselves in appearance, growing arbitrarily, and even forming a xiang shape (there is an inner flavor, Figure 9).
Figure 8 Ammonite Sea (Source: cluelessconscience.com copyright: Robbie Sidhu)
Figure 9 Ammonite Heteromorph ammonite, preserved at the Museum of Natural Sciences in Houston
(Source: Wikipedia-Daderot)
Everything is still so familiar, and the triumphant ammonite has encountered the great purge of nature. This time, it was not so lucky, completely sinking into the dark seabed. The Ammonite Dynasty and the Dinosaur Dynasty were buried mercilessly by the irresistible forces of nature.
However, in the barren ocean after being tormented by meteorite impacts and volcanic eruptions, the bright eyes of the last proud cockroach of the Cephalopod Empire are looking at the revived world, the age of armorless is coming, see the dragon unloading armor, we will see you next!
bibliography:
[1] Jason B. Ramsay, Cheryl D. Wilga, Leif Tapanila, et al., 2014. Eating with a Saw for a Jaw: Functional Morphology of the Jaws and Tooth-Whorl in Helicoprion davisii. JOURNAL OF MORPHOLOGY 00, 1–18.
[2] Shu-zhong Shen, Samuel A. Bowring, The end-Permian mass extinction: a still unexplained catastrophe, National Science Review, Volume 1, Issue 4, December 2014, Pages 492-495, https://doi.org/10.1093/nsr/nwu047
Xu Hankui. Biological Evolution from the Rise and Fall of Cephalopods, 2015. Biological Evolution. (4):33-40.
Source of the article: Science Compound
Author: Wang Guanqun Pan Haochen Fang Xiang Liu Yun Tan Chao
Author Affilications:Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences