Fossil Hunting in Florida Why are there so many Fossils in Florida?




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Fossil Hunting in Florida



















   




Why are there so many Fossils in Florida?

There are many fossils, not just in Florida, but throughout the low country of the Southeastern U.S.  To understand why, you need to know a little ancient history.

With each Ice Age, the Earth cooled and polar ice formed.  These rising ice continents pulled water from the oceans and lowered sea levels.  This exposed new dry land around the world, including most of the state of Florida.  What had once been a warm, shallow sea, home to abundant aquatic life, gradually became a swampy home for reptiles.  As the land continued to emerge from the water, it was inhabited by prehistoric mammals, escaping the cold of the north.  It is believed that many Ice Ages have come and gone, leaving behind a vast and varied treasure of fossils.



Many ask, "Do you find dinosaur fossils?"  Actually, dinosaurs lived prior to the Ice Ages, when Florida was still under water.  So if dinosaur fossils are found, they would likely be aquatic dinosaurs.  Unfortunately, the vastly changing landscape of Florida, the warm water and high temperatures make finding 100 million year old dinosaur fossils unlikely.

The fossils we find are conservatively estimated to be between 2 and 20 million years old.  While they include many species that still exist today, they also include extinct species, such as giant sharks, giant land tortoise, mammoth and mastodon, saber-tooth cat, giant ground sloth, North American rhinoceros, camel and many others.  No one really KNOWS how old these fossils are.  In a laboratory you can fossilize something in a matter of hours.  Natural conditions could take hundreds, thousand or perhaps millions of years.  Also complicating age identification is the fact that river-found fossils have been washed from "who knows what level" and mixed with other fossils.

If you are old enough to have lived when these extinct animals were alive, feel free to step forward and speak authoritatively.  If not, you'll have to wade through the often-contradictory scientific information and decide for yourself.  Also, your religious beliefs about the origin of the world may impact your opinion.

Where can I find Fossils?

There are fossils approximately 5-15 feet below the surface almost anywhere you walk in our part of Florida.  The reason is explained in the answer to the first question (above).  The trick is simply to find places where that 5-15 foot depth is exposed.  One place to find fossils is where someone is mining, or digging a trench or canal, or working on a construction project.  You will likely find fossils in the piled-up debris (the "spoil") that was removed from the excavation.  Another place to find fossils is at the beach (especially west central Florida).  They are washed onto the beach by the surf, from fossil deposits that are off-shore (and approximately 5-15 feet below the surface).  The place I prefer to hunt fossils is in the rivers of southwest Florida.  As they course through the landscape, rivers cut out the banks.  After a period of flooding, you'll see just how powerful the river is, moving LARGE amounts of sand and debris.  Every year the river changes, sometimes dramatically, always washing new fossils into the river bed.  Below are the pros and cons of each location.




   
Construction or Mining "spoil" piles


Pro - Fossils that are found may be in very good condition.

Con - Because of strict insurance policies, access to the site will likely be restricted by the company doing the work.

Pro - If you CAN obtain permission to fossil hunt there, you will likely have little competition.

Con - Without a water source, sifting through the debris is more difficult.

Pro - The fossils you find may have desirable light colors, including whites, tans and even green.

   
Beach Combing


Pro - Access is relatively easy, but that means...

Con - You have a lot of competition from other beach combers, especially the experienced ones, who know to look after storms.

Pro - If you like sea shells, they can be found at the same time.

Con - Because the fossils are washed back and forth in the surf, they are often broken and worn.

Pro - If you're a social person, you'll enjoy meeting people and answering questions about what you're looking for.

   
River Digging


Pro - Plenty of moving water provides an easy way to separate the fossils from the sand (using special equipment).

Con - When the water level is too high, access to the best fossil hunting spots is limited (unless you can dive).

Pro - You can find concentrated fossil deposits, due to the action of the river and the work of Phosphate miners who dredged the rivers a century ago.  They separated the sand from debris, then sorting out the Phosphate.  The remaining debris, which included fossils, was discarded back into the river.  Pockets of this debris can be found.

Con - Though animals are seldom a problem, the rivers are home to alligators and poisonous snakes.  Be smart - be safe.

Pro - You'll have the chance to see many species of plants, birds and perhaps even reptiles and mammals.

Will I see an alligator while I Fossil Hunt?

   




Alligators are not like crocodiles (native to Africa, Asia, South America and Australia).  Crocodiles apparently consider humans their prey and many attacks are reported each year.  Fortunately, crocodiles are no longer native to Florida and are rarely seen.  Alligators (which we have a lot of) generally DO NOT prey on humans.  They will generally only attack if they feel threatened.  Keep your distance.  Given the chance, they will generally move away, in an attempt to avoid you.

The most dangerous type of alligator in Florida is one that has been fed by humans.  This will cause the alligator to lose its natural fear of humans.  Any such alligator is promptly dealt with by authorities.  Such an animal will approach humans, expecting a hand-out.  If no hand-out is offered, a hand will do just fine.

Like I said, in the wild, alligators would rather avoid humans than attack them.  Even so, it's not a good idea to bring small children or pets near the water, which are closer to the size of typical alligator prey.  Not long ago, a woman was bitten on the leg, while trying to defend a pet that she was walking near the water.  The gator was after the pet, not her.

If you fossil hunt as part of a group of people, you'll probably never see a gator.  They'll slip under the water and make a fast pace away from you.  They're an impressive sight, if you get the chance.  In fact, do yourself a favor and take time while you're in Florida to rent a canoe and drift down a river.  You'll not only see gators, but turtles, many species of birds (perhaps a bald eagle) and maybe even some mammals like river otters, deer, wild boar, and more.  Plus, the trees and plants can be breath-taking, especially when they're flowering or bearing fruit.

If you saw an alligator and crocodile next to each other, you could relatively easily tell them apart.  First, the crocodile may be larger, and that may also be why they consider humans prey.  Also, the crocodile may have a lighter color - alligators tend to be dark gray/green.  The tell-tale feature though, is their teeth.  An alligator has an "over-bite."  It's lower teeth fit into the roof of its mouth and are not visible when the jaw is closed.  Only top teeth visible (mouth closed) = alligator.  Top and bottom teeth visible (mouth closed) = crocodile.  If it's coming toward you with an open mouth, then it doesn't really matter what it is, does it?

When is the best time of year to Fossil Hunt?

   




At the beach, fossils can be found anytime, especially after storms.  In the rivers, the best (and least disturbed) fossils are deep.  That means, the best time to hunt fossils at rivers is during the dry season (winter and spring), because the water is lowest.  The summer may be the best time to travel, because the kids are out of school, but it's not the best time to fossil hunt in rivers.  To improve your chances of a successful fossil hunt, you should plan to be here sometime between Christmas and Memorial Day.  In January and February, you may find the water to be a bit cool.  If you wait until April or May, the water will be warmer, but you may also encounter early-arriving wet weather.
   








Rain / Storms

Water Level

Water Temp






Winter  -     

Ending

Falling

Cool





Spring  -     

Unlikely

Lowest

Warm



Summer  -     

Beginning

Rising

Warm



Fall  -     

Likely

Highest

Warm






   
The information above is just a guideline.  Actually, there could be a heavy rain (or a rainy period) anytime during the year, which could bring up the river's water level.  The best plan would be to arrive in mid-Spring and cross your fingers.  If you can only travel in the summer, plan to be here as early as possible.








   




You can check the Peace River water level ("gage height") at the USGS web site (as recorded at Arcadia, Florida).  After the page loads, scroll down to find a graph displaying the recorded water level over the course of the past month. 






NOTE - The blue areas shown above are averages.  The actual water level will vary, perhaps much higher or much lower.  Generally though, you can expect the water level to be close to that listed above.

What equipment will I need to Fossil Hunt?




Along the beach, you just look down, where the surf is washing things onto the beach.  You may benefit from using what is called a Florida "snow shovel."  It is a specially shaped metal wire basket on the end of a pole.  How it is used will be obvious once you see it.



Fossil hunting in rivers, you can occasionally find nice fossils along the rivers edge, exposed as the water level goes down.  Much of Florida's river banks though have dense plant/tree growth right up to the edge of the water.  To consistently find fossils, you'll need to get into the river and get your feet wet, because fossils tend to be washed to the center of the river.  Much of the riverbed, during the dry season, lies just 1-3 feet below the water's surface.  The basic premise is to separate the fossils from everything else.

First, you use the water and specially designed equipment to wash out the sand, dirt and very small debris.  Then you use your trained eye to spot the fossils among the river rocks.  Most people use a simple "screen box."  Thousands of hours of experience have contributed to a floating, two-tier design that we manufacture, sell and rent.  Our unique design allows you to spot fossils more easily and allows you to work 2-3 times as fast as a typical "screen box" (thus go through 2-3 times as much material).  You can bring your own shovel though.  It should be strong, long-handled and have a pointed blade (like Florida Jones is using in the animation above-left).

Also, fossils can be found by snorkeling or diving, using a technique called "fanning."  Come visit and we'll show you how.  It's not for the faint-hearted though, if you have a phobia about gators.

There are other important things to bring that you might not think of.  Be sure to bring a wide-brimmed hat (like Florida Jones has).  Cords for tying it under your chin might be useful also, when the occasional air-boat comes by.  Also bring sunscreen, unless you want to go home with a tourist tan (sunburn).  The best shoes to wear are neoprene diving boots, which can be found at any dive shop for about the price of a pair of tennis shoes.  Old tennis shoes will work, but the dive boots have high, tight ankles, which will be more comfortable and keep the sand out better.  Inexpensive aqua-socks, found at discount department stores, provide less protection and support, and are often torn-up by the end of a day of fossil hunting.  Wear clothes that you don't mind getting wet and dirty.  And if you are fossil hunting in the winter, you might want a dry towel for when you get out of the water.  If you arrive in January or February you may want to use a thin wet-suit ("skin"), though it may restrict movement more than you want.

You'll dehydrate quicker than you might think, so bring water (caffeine worsens dehydration).  Take breaks often and bring snacks.  Fossil hunting is actually hard work, but it's so fun you may not notice until you're exhausted.  Taking breaks is especially difficult, because fossil hunting is like gambling.  That next pull of the slot machine handle (or that next shovel-full of debris) may be the one that pays off - that big Megladon shark tooth or canine tooth from a saber-tooth cat.  I recommend having firm plans about when you'll leave the river and sticking to it.  It's easy to say, "Just one more scoop."  Late in the day though, is when the weather often turns bad (lightning is nothing to toy with) and evening is when the alligators are more active.  You don't want to meet up with one that is especially hungry or happens to be near-sighted.  Be smart - be safe.

Can I keep ANYTHING I find?

The river belongs to the State of Florida (to the legal residents of Florida).  Scientifically important finds may be more important to all of us than it is to just you.  The State of Florida, through legislation, says that sea shells and shark teeth are common enough that they do not need to be regulated.  Other types of fossils though, such as Mammoth, Mastodon and other unique vertebrates may be important enough for the state to take possession of them.  Amateur fossil hunters are only loosely regulated, so those of us who do it professionally try to educate those just getting started.  Here is some information that you should know.

To fossil hunt on privately owned land, you MUST have the permission of the land owner.  The river bank is likely private land, so fossil hunting there may be illegal, without permission.  Anyone can fossil hunt on state owned land (such as river beds), but some areas may be off-limits, including State Parks or any site containing a high concentration of human artifacts.  If you are only an occasional fossil hunter, you probably do not need a permit to fossil hunt on State land.  If you fossil hunt regularly though, you probably DO. 

Use this link and look under the heading "Who Must Obtain A Permit?" http://www.flmnh.ufl.edu/natsci/vertpaleo/vppermit.htm

We have a permit, which covers our fossil hunting activity.  Most of the people we work with do not require a permit.  Obtaining a permit is easy and inexpensive.  Use the above link for more information.  Whether you have a permit or not, please follow the guidelines of reporting any significant finds.

When I started fossil hunting, I felt very possessive of the things that I found.  It eventually became apparent though, that (1) the land belongs to all of us, not me and (2) the find might be important enough to be of value to us as a society.  Please be respectful of this consideration, but don't let it stop you from fossil hunting.  Some of the most important finds have been made by amateur fossil hunters.

Use common sense.

        Do not do major excavations in the river banks (the bank is likely private land).


        Do not destroy vegetation or disturb wild-life, especially alligators.
        Avoid deep water and fast currents (be safe).


Shark Fossils found in Florida
Text and illustrations are provide by Shark Teeth R Us at www.sharkteethrus.com.
   




Reef-Dwelling (or Requiem) - (upper jaw) -  The crown is fully serrated and can be either straight or angled.  As with most sharks, the teeth positioned closer to the back of the jaw tend to be shorter and more angled.  Common Requiem species include the Black Tip, Bull, Dusky, Reef, Sand Bar, Silky, Spinner and more.  (average size = 3/4 inch) - (scientific name Carcharhinus sp.)



Reef-Dwelling (or Requiem) - (lower jaw) -  Many Requiem species have lower teeth that look similar to their upper teeth (illustrated above).  The Bull and others will have lower teeth that look like this one (illustrated left).  The crown is either finely serrated (Bull) or not at all and can be angled.  (average size = 3/4 inch) - (scientific name Carcharhinus sp.)



Lemon -  The crown is not serrated.  There is a wavy cutting surface along the root, where the crown and root meet.  As with most sharks, the teeth positioned closer to the back of the jaw tend to be shorter and more angled.  (average size = 3/4 inch) - (Lemon scientific name Negaprion brevirostis)



Tiger -  The crown is serrated, including dramatic serrations near the root (on the inside angle of the crown).  Teeth near the back of the jaw can be much shorter.  (average size = 1 inch) - (scientific name Galeocerdo cuvier)  An extinct Tiger species has a more dagger-like crown and less dramatic serrations.  (average size = 3/4 inch) - (scientific name Galeocerdo contortus)



Sand Tiger -  The long, slender crown is not serrated.  There is a single cusp on each side of the crown, which is often damaged.  Note the U-shaped root, which is also prone to damage.  (average size = 1 inch) - (scientific name Odontaspis taurus)  A similar looking tooth has a less "U" shaped root and is slightly wider where the root and crown meet.  It is an extinct Sand shark species.  (average size = 1 inch) - (scientific name Odontaspis cuspidata)



Snaggletooth (or Snaggle-Toothed) -  The crown has dramatic serrations.  Upper teeth are fully serrated and can be either wide or narrow.  Lower teeth are generally narrower and are not fully serrated.  They become less serrated as they approach the front of the jaw (remaining serrations near the root).  Both upper and lower teeth have a “median boss“ protruding forward in the center of the root, on the display side.  (average size = 1 1/4 inch) - (scientific name Hemipristis serra)



Extinct Mako? -  This tooth looks very much like the Great White, but the crown is not serrated.  The crown can be angled, but not dramatically.  (average size = 1 1/2 inches) - (scientific name Isurus hastalis)  This was once assumed to be an extinct Mako species (and is often called Mako or extinct Mako), but is more likely an ancestor of the Great White.  Modern Mako teeth are much narrower.



Megalodon (or Meg) -  The crown is serrated and can be slightly angled.  There is a “chevron” or "bourlette" below the root, on the display side of the tooth (the area above the dashed line), which is a different surface texture from either the root or the enamel crown.  (average size = 2 1/2 inches)  (largest ever found - over 7 inches) - (scientific name Carcharocles megalodon or Carcharodon megalodon.



Great White (or White Pointer) (or White Death) -  This tooth looks a lot like an Isurus hastalis tooth, but has heavy serrations.  It is rarely found in Florida.  (average size = 1 1/4 inches) - (scientific name Carcharodon carcharias)

The fossil shark teeth identified on this page are listed in the approximate order of their rarity (as found in Florida rivers).  The top listings are the most common and the lower listings are more rare.  This may help you decide what type of tooth you have found.  Chances are, if you are debating between two possible identifications, it's the one listed higher in the above chart.




 


 










  • WHERE SHARKS TEETH HAVE BEEN UNCOVERED?

  • North America

    • Florida, North and South Carolina

  • South and Central America

    • Peru, Chile, Venezuela, Costa Rica

  • Africa - Morocco

  • Europe – Belgium







A "Quick & Dirty" Guide to

Fossil Shark Teeth

Sandtiger Shark Carcharias spp.

  • long, slender, smooth-edged blade

  • small, secondary cusplet on either side of main blade

  • strongly bilobed root

  • large lingual protruberance (bulge) and nutrient groove at center of root

Many 'species' have been named, but the fossil teeth are difficult to distinguish from one another as well as similar genera, such as Odontaspis and Striatolamna.

Paleocarcharodon orientalis

  • broadly triangular, thin, coarsely serrated blade

  • large, complex secondary cusplets

  • no prominent lingual protuberance at center of root

  • tapered basal groove between blade and root

  • strongly bilobed root with U-shaped notch at center

Considered by some to be the earliest member of the genus Carcharodon, P. orientalis seems to be a short-lived evolutionary dead-end in no direct way related to the modern White Shark.

Parotodus benedeni

  • stout, robust, smooth-edged blade

  • no secondary cusplets

  • prominent lingual protuberance at center of root

  • strongly bilobed root

A poorly known species of uncertain affinities; this specimen is from Nova Scotia, Canada

Otodus obliquus

  • triangular robust, smooth-edged blade

  • stout secondary cusplets on either side of main blade

  • strongly bilobed root

  • large lingual protruberance and nurtrient groove at center of root

A direct ancestor of Megalodon (Carcharocles megalodon); most commercially sold specimens come from Morocco

Carcharocles auriculatus

  • triangular, thick, finely serrated blade

  • prominent secondary cusplets

  • broad chevron (enameloid-free scar) between blade and root

  • root strongly bilobed

Resembles a serrated Otodus obliquus and was, until recently, sometimes classified as Otodus subserratus.

Carcharocles chubutensis

  • broadly triangular, thick, finely serrated blade

  • small to subtle secondary cusplets

  • broad chevron (enameloid-free scar) between blade and root

  • root strongly bilobed

Like other Carcharocles, C. chubutensis is probably best regarded as a chronomorph rather than a biologically discrete species.  The numerous subtle variations between C. auriculatus and C. megalodon represent a continuum of evolution within a single world-wide species.

Carcharocles megalodon

  • very broadly triangular, thick, finely serrated blade

  • no secondary cusplets

  • broad chevron (enameloid-free scar) between blade and root

  • root strongly bilobed

Most commercial specimens come from the Cooper River in North Carolina and are greyish-black (eg: the specimen on the right); large specimens are becoming scarce



 Cosmopolitodus planus

  • broadly triangular, flattened, unserrated blade

  • no secondary cusplets

  • narrow basal scar between root and blade

  • no lingual protruberence on root

  • cusp of main blade strongly curved at tip

  • blade overhangs the root markedly



 Cosmopolitodus hastalis

  • broadly triangular, flattened, unserrated blade

  • no secondary cusplets

  • narrow basal scar between root and blade

  • no lingual protruberence on root

  • cusp of main blade NOT strongly curved at tip

  • blade does NOT overhang the root markedly

A direct ancestor of the modern White Shark (Carcharodon carcharias)

White Shark Carcharodon carcharias

  • broadly triangular, flattened, coarsely serrated blades

  • serrae are irregular in size and spacing, a feature which helps distinguish teeth of this species from triangular and serrated toothed whaler sharks, such as the Oceanic Whitetip (Carcharhinus longimanus)

  • narrow scar separating blade from root

  • strongly bilobed root, especially in anterior lower teeth

 Squalicorax pristodontus

  • broad, flattened, serrated blade

  • blade strongly convex on leading edge

  • blade distinctly angled on trailing edge

  • root extremely flattened, almost lacy

  • root with shallow U-shaped notch at center

Teeth of this species are functionally similar to those of the Tiger Shark (Galeocerdo cuvier)

Hemipristis serra

  • falcate, flattened, strongly serrated blade

  • no serrae on very tip of blade

  • base of blade often ridged longitudinally (lengthwise)

  • squared-off root

  • thick lingual protruberance at center of root flanking nutritive groove

Represented today by the Snaggletooth Shark (Hemipristis elongatus)

Tiger Sharks Galeocerdo contortus

  • deeply-notched, flattened blade with strong serrations at shoulders (near the base) of blade, especially on inner margin

  • main cusp angular rather than smoothly curved (as in G. cuvier)

  • blade height up to twice root breadth

Closely related to the modern Tiger Shark (Galeocerdo cuvier)



Tiger Sharks Galeocerdo cuvier

  • deeply-notched, flattened blade with strong serrations at shoulders of blade, especially on inner margin

  • main cusp smoothly curved (unlike G. contortus)

  • blade height about equal to root breadth

One of the most beautifully-shaped of shark teeth, remarkably similar to those from modern specimens



Dusky Shark Carcharhinus obscurus

  • oblique, flattened blade with broad serrated shoulders tapering to narrow apex

  • serrations decreasing in size toward tip of blade

  • squared-off root

The teeth of various fossil species of whaler (grey) sharks can be very difficult to distinguish; it is probably best to regard all identifications as highly provisional.

Bull Shark Carcharhinus leucas

  • broad, flattened, serrated blade tapering to narrow apex

  • serrations decreasing in size toward tip of blade

  • squared-off root

The teeth of various fossil species of whaler (grey) sharks can be very difficult to distinguish; it is probably best to regard all identifications as highly provisional.




Oceanic Whitetip Shark Carcharhinus longimanus

  • broadly triangular, flattened, serrated blade, superficially similar to that of a White Shark (Carcharodon carcharias)

  • serrations decreasing in size toward tip of blade

  • squared-off root

The teeth of various fossil species of whaler (grey) sharks of the genus Carcharhinus can be very difficult to distinguish; it is probably best to regard all identifications as highly provisional.

Lemon Shark Negaprion brevirostris

  • narrow, flattened, unserrated blade

  • blade erect to slightly oblique

  • base of blade with broad 'shoulders'

  • squared-off root

Fossil teeth of this species are remarkably similar to the teeth from modern specimens

JAWS, Then and Now

Even in their earliest days, sharks showed some remarkable variations on their basic structural theme. Ancient sharks differed from their modern descendants in several important respects:



The snout of a Devonian shark was typically short and rounded, and the jaws were longish and located at the front of the head. In modern sharks, the snout is typically longish and pointed, the jaws shorter and located underneath the head. Long jaws are structurally weaker than short ones and less able to produce a powerful bite, so early sharks may have plucked prey from the bottom or 'on the fin' with forceps-like delicacy.

Early sharks' upper jaws were fixed to the braincase at both the front and the back (the so-called 'amphistylic' form of jaw suspension), unlike most modern sharks in which the upper jaw is fixed to the braincase at the back only ('hyostylic' jaw suspension). As a result, ancient sharks may have been less able to protrude their jaws than modern sharks, reducing their ability to suck prey into their mouths and restricting the size of their food.

The braincase and olfactory capsules (which house the scent organs) of ancient sharks were relatively small, suggesting that they had a lesser brain and less well-developed sense of smell than their modern descendants. Smaller brain size may also indicate that their other senses were less acute, predatory behavior less flexible, and social dynamics lgess sophisticated than in most modern sharks (especially the whalers and hammerheads).

The teeth of the earliest sharks were smooth-edged and multi-cusped, with a large central blade flanked by two or more smaller cusplets on either side (a tooth type termed cladodont, meaning 'branch-toothed'). Although some of the more conservative modern sharks (such as the six- and seven-gills, nurse sharks and smoothhounds) have multi-cusped teeth, the most recent forms (such as whalers, hammerheads, and the white shark) typically have single-cusped teeth often with serrations. Cladodont teeth are best suited to grasping prey that can be swallowed whole; whereas the sharp-edged or serrated single-cusped teeth of modern sharks opens new dietary options, enabling them to gouge pieces from food items too large to be swallowed whole.

The pectoral fins of ancient sharks were triangular and rigid with broad bases. In contrast, most modern sharks have falcate, highly flexible pectoral fins with narrow bases. Therefore, the fins of ancient sharks were probably somewhat less maneuverable than those of modern sharks, making them less agile.

The backbone of ancient sharks was composed of many, relatively simple vertebrae which were uncalcified and did not constrict the spinal column. The backbone of most modern sharks contains fewer, complexly sculpted vertebrae which have calcified bands and constrict the spinal column at regular intervals. (Exceptions include the squaloid dogfishes and the six- and seven-gilled sharks, most of which inhabit very deep waters. It is not clear whether this is due to retention of primitive characteristics or a secondary adaptation to their nutrient-poor deep-sea environment.) The poorly calcified backbone of ancient sharks may have been less able to withstand the forces generated by the flank muscles, making them less powerful swimmers than most of their modern descendants.

Yet in many respects, ancient sharks were very similar to modern sharks. Like the sharks of today, ancient sharks had a cartilaginous skeleton, replaceable teeth, tooth-like scales called 'dermal denticles', multiple gill slits, two sets of paired fins (pectoral and pelvic), claspers (the paired, cartilage-supported copulatory organs of male sharks, developed along the inner margin of the pelvic fins), a backbone that extended into the upper lobe of the tail, and a strongly heterocercal tail fin (more properly called a caudal fin), in which the upper lobe is considerably longer than the lower.

 

Thus, sharks are like automobiles: new models come and go, but certain basic features remain much like those in the prototype.





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