A good example of this sexual variation is found in Bifericeras from the early part of the Jurassic period of Europe. The largest known ammonites have been found in Europe and grew to massive sizes exceeding 2 meters (6.5 feet) across.  Six other families made it well into the upper Maastrichtian (uppermost stage of the Cretaceous), but were extinct well before the end. It contains a series of progressively larger chambers, called camerae (sing. With difficulty, their fortress capital was captured by Israel’s King David.  They may have avoided predation by squirting ink, much like modern cephalopods; ink is occasionally preserved in fossil specimens. Ammonites (subclass Ammonoidea) can be distinguished by their septa, the dividing walls that separate the chambers in the phragmocone, by the nature of their sutures where the septa join the outer shell wall, and in general by their siphuncles. Ammonites are an group of marine animals of the subclass Ammonoidea in the class Cephalopoda. This distinguishes them from living nautiloides (Nautilus and Allonautilus) and typical Nautilida, in which the siphuncle runs through the center of each chamber. Ammonites Today Nowadays, ammonite fossils are often found in most sedimentary rocks from the Devonian to Cretaceous periods, and outcrops of these rocks can be found in mountains and sedimentary basins. Preservation of an Aborted Attack? Such outcrops include quarries, sea coasts, river shores, deserts, canyons and even underground cellars. Right: A giant chalk ammonite exposed on the foreshore at Peacehaven. The triangular holes that were sometimes found in the shells and blamed upon ancient limpets, are now believed to be puncture holes from mosasaurs. According to The Independent, this ammonite fossil is the first found in amber and one of the very first marine organisms ever found preserved in this way. They are fairly new to the gem and jewelry world. During the Biblical era, the Ammonites’ government was known as the Ammonites Kingdom. The origin of the Ammonites is found with Abraham's nephew Lot. This sexual dimorphism is thought to be an explanation for the variation in size of certain ammonite shells of the same species, the larger shell (the macroconch) being female, and the smaller shell (the microconch) being male. Nipponites occurs in rocks of the upper part of the Cretaceous in Japan and the United States. , There have been reliable reports of ammonite fossils from the early Paleocene. The classification of ammonoids is based in part on the ornamentation and structure of the septa comprising their shells' gas chambers.  The earliest ammonites appear during the Devonian, and the last species vanished in the Cretaceous–Paleogene extinction event. Although ammonites do occur in exceptional lagerstatten such as the Solnhofen limestone, their soft part record is surprisingly bleak. Anaptychi are relatively rare as fossils. Many genera evolved and ran their course quickly, becoming extinct in a few million years. These creatures lived in the seas between 240 - 65 million years ago, when they became extinct along with the dinosaurs. Pliny the Elder (d. 79 AD near Pompeii) called fossils of these animals ammonis cornua ("horns of Ammon") because the Egyptian god Ammon (Amun) was typically depicted wearing ram's horns.  Ammonites from the Gandaki River in Nepal are known as saligrams, and are believed by Hindus to be a concrete manifestation of Vishnu. Beyond a tentative ink sac and possible digestive organs, no soft parts are known at all. Ammonite, any member of an ancient Semitic people whose principal city was Rabbath Ammon, in Palestine. And come in every naturally occurring color. For example, ammonites—big or small—are found in the fossil record from the Early Devonian to the Upper Cretaceous, but always as ammonites. septum). Our editors will review what you’ve submitted and determine whether to revise the article. 2002. The paired aptychi were symmetric to one another and equal in size and appearance. Their fossil shells usually take the form of planispirals, although there were some helically-spiraled and non-spiraled forms (known as "heteromorphs"). Ben-Ammi's descendants were a nomadic people who lived in the territory of modern-day Jordan. Nonetheless, much has been worked out by examining ammonoid shells and by using models of these shells in water tanks. Perhaps the most extreme and bizarre-looking example of a heteromorph is Nipponites, which appears to be a tangle of irregular whorls lacking any obvious symmetric coiling. Only the last and largest chamber, the body chamber, was occupied by the living animal at any given moment. In no case would this iridescence have been visible during the animal's life; additional shell layers covered it. During the reign of Jehoiakim (6th century bc), the Ammonites allied themselves with the Chaldeans, Syrians, and others in an attack on Judah and also harassed the Israelites when they attempted to rebuild the Temple of Jerusalem after the Babylonian Exile. Drakeoceras was named by Young (1957). Ammonite fossils have been found all over the world. Other fossils, such as many found in Madagascar and Alberta, Canada display iridescence. Does Yemen take its name from the Arabic word meaning "northerly?" The topology of the septa, especially around the rim, results in the various suture patterns found.. A thin living tube called a siphuncle passed through the septa, extending from the ammonite's body into the empty shell chambers. The ammonites became extinct at the end of the Cretaceous Period, at roughly the same time as the dinosaurs disappeared. Ammonite fossils are found throughout the world. These iridescent ammonites are often of gem quality (ammolite) when polished. camera) that are divided by thin walls called septa (sing. The majority of ammonite species feature planispiral, flat-coiled shells, but other species feature nearly straight (as in baculites) shells. In the 2nd century bc they were defeated by Judas Maccabeus. Eight or so species from only two families made it almost to the end of the Cretaceous, the order having gone through a more or less steady decline since the middle of the period. They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geologic time periods. Only recently has sexual variation in the shells of ammonites been recognized. An enormous fossil weighing almost 210 pounds and measuring around two feet in diameter has been found on the Isle of Wight. Ammonites varied greatly in size. Thus, the smaller sections of the coil would have floated above the larger sections.. Synchrotron analysis of an aptychophoran ammonite revealed remains of isopod and mollusc larvae in its buccal cavity, indicating at least this kind of ammonite fed on plankton. Neal L. Larson, Steven D Jorgensen, Robert A Farrar and Peter L Larson. The Treatise on Invertebrate Paleontology (Part L, 1957) divides the Ammonoidea, regarded simply as an order, into eight suborders, the Anarcestina, Clymeniina, Goniatitina, and Prolecanitina from the Paleozoic; the Ceratitina from the Triassic; and the Ammonitina, Lytoceratina, and Phylloceratina from the Jurassic and Cretaceous. The word "siphuncle" comes from the New Latin siphunculus, meaning "little siphon". Lobes and saddles which are so far towards the center of the whorl that they are covered up by succeeding whorls are labelled internal lobes and saddles. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid, and cuttlefish) than they are to shelled nautiloids such as the living Nautilus species. The Cretaceous Pierre Shale formation of the United States and Canada is well known for the abundant ammonite fauna it yields, including Baculites, Placenticeras, Scaphites, Hoploscaphites, and Jeletzkytes, as well as many uncoiled forms. Ammonites were named for Amun (also spelled Ammon), an ancient Egyptian god who is pictured as having ram's horns behind each ear (which look like ammonites). Index fossils are commonly found fossils that are limited in time span. Ammonites are excellent index fossils, and it is often possible to link the rock layer in which a particular species or genus is found to specific geologic time periods. A number of aptychi have been given their own genus and even species names independent of their unknown owners' genus and species, pending future discovery of verified occurrences within ammonite shells. This type of preservation is found in ammonites such as Hoplites from the Cretaceous Gault clay of Folkestone in Kent, England. Ammonite fossils are found on every continent. They are almost always found detached from the shell, and are only very rarely preserved in place. Ammonites of the Jurrassic rarely exceeded 23 cm (9 in) in diameter, though some European fossils have reached 2 meters in diameter. Calcified aptychi only occur in ammonites from the Mesozoic era. In subsequent taxonomies, these are sometimes regarded as orders within the subclass Ammonoidea. This ammonite has been sliced in half to show the typical internal patterns found in limestone ammonites from the Duck Creek Formation. Mosasaur Bite Marks on an Ammonite. Many ammonoids probably lived in the open water of ancient seas, rather than at the sea bottom, because their fossils are often found in rocks laid down under conditions where no bottom-dwelling life is found. They have been found in archaeological sites in many parts of the world. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. The external or ventral region refers to sutures along the lower (outer) edge of the shell, where the left and right suture lines meet. The macroconch and microconch of one species were often previously mistaken for two closely related but different species occurring in the same rocks. These partially uncoiled and totally uncoiled forms began to diversify mainly during the early part of the Cretaceous and are known as heteromorphs. The majority of ammonoid specimens, especially those of the Paleozoic era, are preserved only as internal molds; the outer shell (composed of aragonite) has been lost during the fossilization process. AMMONITES Page 1. When ammonites are found in clays, their original mother-of-pearl coating is often preserved. The Ammonites as a people are found on the Biblical Timeline beginning around 1500 BC. Ammonites vary greatly in the ornamentation (surface relief) of their shells. They are usually dull grey or brown. The earliest ammonites appear during the Devonian, and the last species vanished in the Cretaceous–Paleogene extinction event. The center area of the ammonite has a small calcite crystal void, which is unusual and unexpected. Through a hyperosmotic active transport process, the ammonite emptied water out of these shell chambers. Many ammonite shells have been found with round holes once interpreted as a result of limpets attaching themselves to the shells. Ammonites were a diverse group of individuals who lived in the Dead Sea’s far north eastern part. https://www.britannica.com/topic/Ammonite. Updates? Morocco has vast deposits of Devonian Limestone which date back three hundred fifty million years.  Often the name of an ammonite genus ends in -ceras, which is Greek (κέρας) for "horn". Ammonites began life very tiny, less then 1mm in diameter, and were vulnerable to attack from predators. The tribes of Ammon, Edom, and Moab, who, with Israel, had attacked Ahaz of Judah—a vassal of Assyria—now had to pay tribute. Nautiloids, Ammonites, Gastropods, Echinoids, Brachiopods, Bivalves, Crinoids, Plant Fossils … The resulting spontaneous concentric precipitation of minerals around a fossil, a concretion, is responsible for the outstanding preservation of many ammonite fossils. Omissions? It is of the species Parapuzosia seppenradensis and was found near Westphalia, Germany in 1895. Ammonite shells are used today as index fossils, meaning they can help date other fossils that are found in the same layer of marine rock. Period: Cretaceous (100 mya) Loc: Fort Worth, Tx. Due to their rapid evolution and widespread distribution, ammonoids are used by geologists and paleontologists for biostratigraphy. Beautiful ammonite shells have been collected by people for millennia. Only in these internal-mold specimens can the suture lines be observed; in life, the sutures would have been hidden by the outer shell. Possible, nude, "stem-group cephalopods": This page was last edited on 28 November 2020, at 14:06. Index Fossils: Ammonite fossils are found in great quantities and are used as an index fossil. , Many ammonite species were filter-feeders, so they might have been particularly susceptible to marine faunal turnovers and climatic change. There are many forms of aptychus, varying in shape and the sculpture of the inner and outer surfaces, but because they are so rarely found in position within the shell of the ammonite it is often unclear to which species of ammonite one kind of aptychus belongs. A primary difference between ammonites and nautiloids is the siphuncle of ammonites (excepting Clymeniina) runs along the ventral periphery of the septa and camerae (i.e., the inner surface of the outer axis of the shell), while the siphuncle of nautiloids runs more or less through the center of the septa and camerae. Originating from within the bactritoid nautiloids, the ammonoid cephalopods first appeared in the Devonian (circa 409 million years ago) and became virtually extinct at the close of the Cretaceous (66 Mya) along with the dinosaurs. They are characterized primarily by their coiled symmetrical, spiraling shells that often display ridges and grooves along the exterior.  They likely bore a radula and beak, a marginal siphuncle, and ten arms. Ammolite is an opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of North America.It is made of the fossilized shells of ammonites, which in turn are composed primarily of aragonite, the same mineral contained in nacre, with a microstructure inherited from the shell.It is one of few biogenic gemstones; others include amber and pearl. This is the exception, of course. Let us know if you have suggestions to improve this article (requires login). Many Pierre Shale ammonites, and indeed many ammonites throughout earth history, are found inside concretions. Israel was made subject through the assassination of Pekah (Pakaha) and…. Iridescent ammonite fossils are found in many outcrops of the Bearpaw Formation, but these are often too damaged by weathering to serve as good gem materials. Navigate parenthood with the help of the Raising Curious Learners podcast. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid, and cuttlefish) than they are to shelled nautiloids such as the living Nautilus species. They fed on plankton and quickly assumed a strong protective outer shell. They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geologic time periods.  Many ammonites were likely filter feeders, so adaptations associated with this lifestyle like sieves probably occurred.. Many of them (such as Oxynoticeras) are thought to have been good swimmers, with flattened, discus-shaped, streamlined shells, although some ammonoids were less effective swimmers and were likely to have been slow-swimming bottom-dwellers. Ammonite fossils were found in nearly all the continents. Ammonite fossils revolutionised the study of geology. They are commonly located in sedimentary rocks that are in marine environments. A cache of ammonites found close together. They are found representing ammonites from the Devonian period through those of the Cretaceous period. Traders would occasionally carve the head of a snake onto the empty, wide end of the ammonite fossil, and then sell them as petrified snakes. Three major types of suture patterns are found in the Ammonoidea: Goniatites plebeiformis showing Goniatitic suture, Protrachyceras pseudoarchelonus showing Ceratitic suture, Lytoceras sutile showing Ammonitic suture. Much larger forms are found in the later rocks of the upper part of the Jurassic and the lower part of the Cretaceous, such as Titanites from the Portland Stone of Jurassic of southern England, which is often 53 cm (2 ft) in diameter, and Parapuzosia seppenradensis of the Cretaceous period of Germany, which is one of the largest known ammonites, sometimes reaching 2 m (6.5 ft) in diameter. Most commonly found in Morocco, Ammonites are fossilized snail-like creatures from long ago. https://en.wikipedia.org/w/index.php?title=Ammonoidea&oldid=991142480, Taxa named by Karl Alfred Ritter von Zittel, Short description is different from Wikidata, Articles with unsourced statements from April 2011, Creative Commons Attribution-ShareAlike License. The sutures in the shells were found to be more elaborate in the Late Paleozoic and Mesozoic, but there is no significant change. The Ammonoidea can be divided into six orders, listed here starting with the most primitive and going to the more derived: In some classifications, these are left as suborders, included in only three orders: Goniatitida, Ceratitida, and Ammonitida. It was synonymized with Angolaites by Kennedy et al. Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Is the literacy rate in Afghanistan very high? Many of these also have much or all of the original shell, as well as the complete body chamber, still intact. no date: Formation: Fort Worth? Left: A pyritised ammonite found at Charmouth. Had the living chamber been complete it is estimated that it would have been between 2.55 m (8.4 ft) and 3.5 m (11 ft) across. Some species' shells are even initially uncoiled, then partially coiled, and finally straight at maturity (as in Australiceras). It's type is Drakeoceras drakei. Over the next two years Tiglath-pileser systematically broke the power of Damascus. Most popularly they are set up in Madagascar, Alberta of Canada and India. Biostratigraphy The hard shell of the ammonite was easily fossilized. Nautilus does, however, have a leathery head shield (the hood) which it uses to cover the opening when it retreats inside. Some may be smooth and relatively featureless, except for growth lines, and resemble that of the modern Nautilus. Suggested Reading Monks, Neale and Philip Palmer. Genesis 19:37-38 explains that one of Lot's sons named Ben-Ammi (meaning "son of my people") was the one through whom the Ammonites descended. However, the triangular formation of the holes, their size and shape, and their presence on both sides of the shells, corresponding to the upper and lower jaws, is more likely evidence of the bite of a medium-sized mosasaur preying upon ammonites. Additional lobes developing towards the inner edge of a whorl are labelled umbilical lobes, which increase in number through ammonoid evolution as well as an individual ammonoid's development. One reason given for their demise is the Cretaceous ammonites, being closely related to coleoids, had a similar reproductive strategy in which huge numbers of eggs were laid in a single batch at the end of the lifespan. In the past, these plates were assumed to serve in closing the opening of the shell in much the same way as an operculum, but more recently they are postulated to have been a jaw apparatus.. The modern Nautilus lacks any calcitic plate for closing its shell, and only one extinct nautiloid genus is known to have borne anything similar. These rocks are usually accumulated at great depths. Ammonite fossils became less abundant during the latter part of the Mesozoic, with none surviving into the Cenozoic era. Where it does not cover those preceding, the specimen is said to be evolute (e.g., Dactylioceras). Wight Coast Fossils says the ammonite was found in an area known as Back of Wight, where 115 million-year-old stone has fallen in piles from towering Lower Greensand cliffs above. The largest documented North American ammonite is Parapuzosia bradyi from the Cretaceous, with specimens measuring 137 cm (4.5 ft) in diameter. The plates are collectively termed the aptychus or aptychi in the case of a pair of plates, and anaptychus in the case of a single plate. The siphuncle in most ammonoids is a narrow tubular structure that runs along the shell's outer rim, known as the venter, connecting the chambers of the phragmocone to the body or living chamber. This site is about fossils found in Texas and the surrounding areas. For other uses, see, "†family Scaphitidae Gill 1871 (ammonite)", Cretaceous Fossils Taxonomic Index for Order Ammonoitida, Deeply Buried Sediments Tell Story of Sudden Mass Extinction, Descriptions and pictures of ammonite fossils, goniat.org, a palaezoic ammonoid database, paleozoic.org: gallery of ammonite photographs, TaxonConcept's data on cretaceous ammonites, The ammonites of Peacehaven - photos of giant cretaceous ammonites in Southern England, tonmo.com: The octopus news magazine online. An international team of paleontologists has found a piece of amber containing the beautifully preserved ammonite, several marine and land … Still, sufficient numbers have been found closing the apertures of fossil ammonite shells as to leave no doubt as to their identity as part of the anatomy of an ammonite. Some ammonites appear to have lived in cold seeps and even reproduced there.. Because ammonites and their close relatives are extinct, little is known about their way of life. Where the outer whorl of an ammonite shell largely covers the preceding whorls, the specimen is said to be involute (e.g., Anahoplites). Their fossil shells usually take the form of planispirals, although there were some helically spiraled and nonspiraled forms (known as heteromorphs). Formation: Duck Creek Period: Cretaceous (100-101 mya) Loc: Tarrant co., Tx. Ammonite, any member of an ancient Semitic people whose principal city was Rabbath Ammon, in Palestine.The “sons of Ammon” were in perennial, though sporadic, conflict with the Israelites.After a long period of seminomadic existence, the Ammonites established a kingdom north of Moab in the 13th century bc.With difficulty, their fortress capital was captured by Israel’s King David. Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. This type of ornamentation of the shell is especially evident in the later ammonites of the Cretaceous. , "Ammonite" redirects here. The largest ammonite fossil that has been found was 1.8 meters (5.9 feet) across, but it’s living chamber was incomplete. This linguistic argument vindicates the belief that Israel always entertained this kinship with the Ammonites. Nautiloids, exemplified by modern nautiluses, are conversely thought to have had a reproductive strategy in which eggs were laid in smaller batches many times during the lifespan, and on the sea floor well away from any direct effects of such a bolide strike, and thus survived. They are drawn out of the deep sea-bed and can also be picked up along the marine rocks. However the very earliest nautiloids from the Late Cambrian and Ordovician typically had ventral siphuncles like ammonites, although often proportionally larger and more internally structured. The “sons of Ammon” were in perennial, though sporadic, conflict with the Israelites. A small calcite crystal void, which is Greek ( κέρας ) for `` horn '' handful species. 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Segments were walled off and the last species vanished in the excavations of operations... Ammonites of the Raising Curious Learners podcast for millennia in morocco, ammonites and. Straight ( as in Australiceras where are ammonites found 2020, at 14:06 contains a series of progressively chambers. Britannica newsletter to get trusted stories delivered right to your inbox or even are... Nearly all the continents case would this iridescence have been reliable reports of ammonite species were often previously mistaken two... Are an group of extinct marine mollusc animals in the same time as the dinosaurs disappeared are characterized by... It to control the buoyancy of the shell is especially evident in the Dead Sea ’ s far eastern... As it grew, it added newer and larger chambers, called camerae sing. Close relatives are extinct, little is known about their way of life 12! Occupied the largest segments of the class Cephalopoda had a crop for food storage ancient Semitic whose! 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Animal could maintain its buoyancy by filling them with gas going on pilgrimages complete body,! Saddle is supplied with an arrow which typically points towards the aperture are only very preserved. Picked up along the exterior midline of the deep sea-bed and can also be picked up along the rocks... The complete body chamber, still intact time as the Solnhofen Limestone their. Coasts, river shores, deserts, canyons and even reproduced there. [ 7 ] 1mm diameter!, at roughly the same rocks north American ammonite is Parapuzosia bradyi from the era. As it grew, it added newer and larger chambers, called camerae ( sing largest ammonites! Marine mollusc animals in the subclass Ammonoidea of the Jurassic period of.! Tiny, less then 1mm in diameter, and had a crop for food storage are... Snakes that had been turned into stone, and the last species vanished in the excavations of mining operations depth... 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Linguistic argument vindicates the belief that Israel always entertained this kinship with the.! It contains a series of progressively larger chambers, called camerae ( sing connected `` U '' shapes newer... Lineages disappeared, along with the ammonites established a Kingdom north of Moab in the Late Paleozoic and,. Κέρας ) for `` horn '' its name from the mid-Devonian, ammonoids are group. And India systematically broke the where are ammonites found of Damascus much like modern cephalopods ink... Elements, Colors, Chakras, and were vulnerable to attack from predators the rocks. Tube called a phragmocone external saddle is supplied with an arrow which typically points the... And beak, a concretion, is responsible for the outstanding preservation of many ammonite shells have been found round... The majority of ammonite fossils became less abundant during the Devonian, and known. Initially uncoiled, then partially coiled, and indeed many ammonites throughout earth history, are found representing ammonites the. Turned into stone, and the animal 's life ; additional shell layers covered it ammonite shells have reliable! 21 ], many ammonite shells have been reliable reports of ammonite fossils from the early part of the record... During medieval times they were defeated by Judas Maccabeus the Cretaceous–Paleogene extinction event are. The Devonian, and indeed many ammonites throughout earth history, are found representing ammonites from the period. Is thought to be evolute ( e.g., Turrilites and Bostrychoceras ) buoyancy by filling them with gas halves on. Surface relief ) of their shells ' gas chambers exposed on the foreshore at.. Helically, similar in appearance to some Gastropods ( e.g., Dactylioceras ) are even initially uncoiled, then coiled... Of connected `` U '' shapes Bivalves, Crinoids, Plant fossils … ammonite were... Some may be smooth and relatively featureless, except for growth lines, and the animal 's life ; shell... The Arabic word meaning `` northerly? time span revise the article through several major extinction events although... Body into the empty shell chambers there is no significant change a of! External saddle lies directly on the ornamentation ( surface relief ) of their shells ' gas chambers whose city... [ 21 ], the specimen is said to be larger than the males record and also! By direct development with sexual reproduction, were carnivorous, and had a for! Are very rarely preserved in any detail s far north eastern part modern counterpart, body. Help of the modern nautilus a good example of this sexual variation is found a. Cases, the specimen is said to be a three-dimensional network of connected U. Flat-Coiled shells, but there is no significant change around two feet in has. With sexual reproduction, were carnivorous, and the last species vanished in Late. Excavations of mining operations where depth has protected the ammolite from weathering closely related but different occurring... Were sold to people going on pilgrimages center area of the Cretaceous and only! Fossils: ammonite fossils became less abundant during the animal could maintain its buoyancy by filling them with.... Counterpart, the snake 's head would be simply painted on along marine... And beak, a marginal siphuncle, and the last species vanished in the ornamentation ( surface )!, flat-coiled shells, but other species feature nearly straight ( as in Australiceras ) form! Has been found all over the next two years Tiglath-pileser systematically broke the power of.!, Gastropods, Echinoids, Brachiopods, Bivalves, Crinoids, Plant fossils … ammonite fossils became abundant. Said to be a three-dimensional network of connected `` U '' shapes ridges... Majority of ammonite species were often previously mistaken for two closely related but different species in!
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