Fossils/Vertebrates

Main article: Fossils

Subphylum Vertebrata

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Physical Description	Have a backbone and cranium.
Fossil Range	Evolved during the Cambrian Explosion.
Taxonomy	Kingdom: Animalia Phylum: Chordata
Adaptations Over Time	Slowly became bigger and more terrestrial. They evolved bigger jaws and stronger bones.

Superclass Agnatha (Jawless Fish) (Ostracoderms)

This fossil will only be tested at the State and National levels.

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Common Names	Jawless fish, including lampreys and hagfish.
Physical Description	They lack paired appendages and jaws. They have skin but no dermal or epidermal scales. Instead of stomachs, they simply have one long gut. Cold-blooded (ectothermic). Two-chambered heart. They have seven or more paired gill pouches. Possess a notochord (a cartilage-like rod that is a characteristic feature of all chordates in at least one stage of life) during their larval and adult stages. They possess a photoreceptive parietal eye for regulating circadian rhythm and body heat. The skeleton is made of cartilage.
Fossil Range	Cambrian Explosion to present-day.
Taxonomy	Agnatha is split up into Cyclostomata (extant and comprising lampreys and hagfish, ~120 species), Conodonta (extinct), and Ostracoderms (extinct). Sister taxon to Gnathostomata (jawed vertebrates). rRNA and mtDNA data suggest that Cyclostomata is monophyletic.
Mode of Life or Habitat	Cold marine waters from 10 meters deep at high latitudes to 1300 meters at low altitudes. Lampreys feed on other fish and mammals. Hagfish are scavengers. No known parental care, fertilization is most likely external.
Distribution	Worldwide, except for tropics and polar regions.
Etymology	Ancient Greek for "without jaws."
External Links	https://en.wikipedia.org/wiki/Notochord. https://en.wikipedia.org/wiki/Agnatha. https://en.wikipedia.org/wiki/Parietal_eye.

Class Placodermi (Armored Jawed Fish)

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Common Names	Placoderms
Physical Description	Most were small fish reaching lengths of 15 cm; however, a few species reached lengths of 4 to 10 meters. They all have jaws, an internal skeleton, head and trunk armor, paired fins, and projecting spines to the sides of the trunk shield. A neck joint allowed them to lift the anterior portion of their head shield. The head and thorax are covered by armored, bony plates. The rest of the body is either covered in small plates or has no plates. The bony plates have three layers, a basal layer made of compact bone, a middle layer made of spongy bone, and a superficial layer.
Fossil Range	Early Silurian (in China) to the Late Devonian (“Age of Fish”). They became extinct at the end-Devonian Hangenberg event.
Taxonomy	Infraphylum: Gnathostomata. Thought to be paraphyletic, consisting of sister groups to modern jawed vertebrates. However, they could be monophyletic. First studied by Louis Agassiz, 1833-1843.
Mode of Life or Habitat	Placoderms lived in both marine and freshwater environments. They were predators and some may have been filter feeders.
Adaptations Over Time	One of the first fish that developed jaws. They evolved jaws from their gill arches. Instead of teeth, they had bony plates. First fish to develop paired pelvic fins, which would later develop into hindlimbs. First fish to develop true teeth. Some genera in this class exhibit the oldest known examples of live birth.
Distribution	Worldwide distribution by the Devonian.
Etymology	Comes from the Greek for plate-skinned or tablet-skinned.
External Links	https://en.wikipedia.org/wiki/Bothriolepis. https://en.wikipedia.org/wiki/Placodermi. https://onlinelibrary.wiley.com/doi/full/10.1111/pala.12093.

Genus Bothriolepis

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Physical Description	Around 30 cm long, but the largest species (B. rex) could be 170 cm long. Lifted their bodies with pectoral fins. Bothriolepis also could have used its fins to throw sediment over itself. Had heavily armored heads attached to the thoracic shield and two holes on their heads (one on the upper side for the eyes and nose and one on the lower side for the mouth), along with preorbital recesses (separate bones below the eyes and noses). The thoracic shield covered almost half of their body. In addition to its gills, they had pouches that connected to the oesophagus, which may have been rudimentary lungs that may have allowed them to live for short periods out of the water. The two halves of the jaw are separate, and adults can use them independently of one another. The tail (caudal fin) was long and is rarely preserved due to its soft nature.
Fossil Range	(Middle and) Late Devonian, ~387-360 mya.
Taxonomy	Order: Antiarchi Family: Bothriolepididae
Mode of Life or Habitat	Benthic detritus feeders. Found in both shore marine and freshwater. Likely to have spent most of its life in freshwater but probably entered saltwater at times.
Distribution	Widespread and abundant. Worldwide, in every paleo-continent.
Etymology	Means pitted scale or trench scale in Greek.
Additional Information	Bothriolepis is a diverse genus.
External Links	https://en.wikipedia.org/wiki/Bothriolepis.

Genus Dunkleosteus

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Physical Description	Some of the largest placoderms. Largest species could grow up to 8.79 m long. Could open and close jaws very quickly, with a bite force of 6000 N. Could weigh up to 4 tons. Instead of teeth, they had 2 pairs of sharp plates which formed a beak. Juveniles likely also had large bite forces.
Fossil Range	Late Devonian, 382-352 mya. It became extinct in the Hangenberg event.
Taxonomy	Order: Arthrodira Family: Dunkleosteidae
Mode of Life or Habitat	Hypercarnivorous apex predators. Diet could have included armored prey such as ammonites and other placoderms. Sometimes cannibalized. May have been pelagic. They were slow swimmers so they ambushed their prey to hunt. Lived in shallow waters as juveniles, then moved to deeper waters. Speed of jaw opening and closing is consistent with suction feeding, where prey is sucked into the predator’s mouth.
Adaptations Over Time	May have been among the first vertebrates to internalize egg fertilization.
Distribution	Many fossils have been found in North America, Belgium, Morocco, and Poland.
Etymology	Named in 1956 after David Dunkle, a paleontologist at the Cleveland Museum of Natural History. ὀστέον, "osteon" is Greek for bone.
Additional Information	Only about 5% of specimens have more than a quarter of the skeleton preserved. Specimens often found with boluses (balled up mix of food and saliva) of fish bones, may have regurgitated bones instead of digesting them.
External Links	https://en.wikipedia.org/wiki/Dunkleosteus.

Class Chondrichthyes (Cartilaginous Fish)

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Common Names	Cartilaginous fish.
Physical Description	Have skeletons made of cartilage with tough skins covered in sharp tooth-like scales (dermal denticles or placoid scales) which are all oriented in one direction. Electric rays are the exception: they have flabby bodies. Chondrichthyans have paired fins and paired nostrils. Their hearts have two chambers in series. The notochord is replaced by vertebrae. They lack bone marrow: red blood cells are created in the spleen and epigonal organ. Some sharks and rays have Leydig’s organs which also produce red blood cells. They have five to seven pairs of gills. Sharks, skates, and rays have special electrosensory organs known as ampullae of Lorenzini. Some species have two dorsal (back) fins while some have one dorsal fin. The pectoral (side) fins are used for steering. The pelvic fin is found on the stomach and stabilizes the body. The clasper is an organ in males found near the pelvic fin used for mating. The tail is called the caudal fin and gives propulsion. It is heterocercal, meaning the upper lobe is bigger than the lower lobe and contains part of the vertebral column. The anal fin, if present, is also used for stabilization.
Fossil Range	Late Silurian to recent.
Taxonomy	Infraphylum: Gnathostomata. Split into two subclasses: Elasmobranchii (sharks, rays, skates, and sawfish) and Holocephali (chimaeras/ghost sharks).
Mode of Life or Habitat	Can be pelagic (in which case they must keep swimming to get water through their gills) or demersal (in which case they can pump water in through the spiracles behind their eyes and out through their gills). Due to their lack of a swim bladder, pelagic species must continuously swim to avoid sinking (buoyancy is given by large amounts of liver oil). Most are marine. Only 5% are restricted to freshwater (e.g. the freshwater stingray). Half of the species live down to depths of 200 m (on the continental slope) while 35% live in depths of 200-2000 m. Beyond that, high salinity and low oxygen levels pose as barriers. Only 5% swim through the open ocean (e.g. the great white shark). Some give birth to eggs surrounded by egg cases/capsules while others give live birth. Predators.
Adaptations Over Time	Among the first vertebrates to evolve jaws and bony teeth. Evolved from spiny sharks (Acanthodii). Very diverse group.
Distribution	Waters worldwide.
Etymology	From Greek "cartilage fish," χονδρ chondr "cartilage" + ἰχθύς ichthys "fish."
External Links	https://en.wikipedia.org/wiki/Chondrichthyes. https://www.ucl.ac.uk/museums-static/obl4he/vertebratediversity/chondrichthyes.html. https://nhpbs.org/wild/chondrichthyes.asp. http://www.comfsm.fm/~brianl/chondrichthyes.html.

Superorder Selachimorpha (Sharks)

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Common Names	Sharks
Physical Description	Usually streamlined body. The jaws are not attached to the cranium. They shed and replace their teeth and scales. The teeth are made of calcium phosphate, an apatite. The pectoral fin is not fused to the head. Can range from 17 cm (the pygmy shark) to 12 m (the whale shark).
Fossil Range	Late Silurian to modern-day, 425- mya.
Taxonomy	Subclass: Elasmobranchii
Mode of Life or Habitat	Common to depths of 2000 m. Usually do not dwell in freshwater, although some do (bull shark and river shark can be found in freshwater and seawater). Well-known species are apex predators. Poikilotherms, "cold-blooded." Most live 20 to 30 years. Sharks practice internal fertilization.
Adaptations Over Time	Sharks have a hydrodynamic shape in order to swim with less resistance, with tapered ends at the head and tail. Most sharks are dark with pale bellies, with camouflages them from above and below.
Distribution	Waters worldwide.
Etymology	The origin of the word "shark" is uncertain.
Additional Information	Some have biofluorescence. Some species can detect as little as 1 ppm of blood in seawater.
External Links	https://en.wikipedia.org/wiki/Shark.

Genus Otodus

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Common Names	A type of mackerel shark (all sharks in Lamniformes are mackerel sharks).
Physical Description	The teeth could get to 10.4 cm tall, and the vertebral centrum could get over 12.7 cm wide. Thus, the maximum length of the shark is estimated to be between 9.1 and 12.2 meters long. The teeth have a triangular crown and smooth cutting edges with visible cusps on the roots.
Fossil Range	Paleocene to Pleistocene (66-0.34 mya).
Taxonomy	Order: Lamniformes Family: Otodontidae.
Mode of Life or Habitat	Top predator. Likely preyed on large bony fish, aquatic mammals, and other sharks.
Adaptations Over Time	Transitional teeth show Otodus evolving into Carcharocles. These teeth have lightly serrated cusplets and serrated cutting edges and are found all over the world (Maryland, Belgium, and Kazakhstan), implying that the evolution occurred worldwide. The ancestor of Carcharocles is thought to be O. aksuaticus.
Distribution	Worldwide.
Etymology	Ancient Greek ὠτ (ōt, "ear") and ὀδούς (odoús, "tooth"), combining to make "ear-shaped tooth."
Additional Information	Fossilized parts are teeth and vertebrae.
External Links	http://fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=34621. https://en.wikipedia.org/wiki/Otodus.

Genus Carcharocles

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Physical Description	Carcharocles is estimated to be 13 meters long - they are one of the world's largest predators. They have about 24 teeth in their upper jaw and 20 in their lower jaw.
Fossil Range	Early Eocene to Pliocene
Mode of Life or Habitat	They could be found in shallow coastal waters, swampy coastal lagoons, offshore deep water environments, etc. They are a transient species - they often move around.
Distribution	Found in North and South America, Africa, Europe, Japan, Australia and New Zealand.
Additional Information	In Greek, Carcharocles means "Famed for Jaggedness."

Species C. megalodon

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Physical Description	C. Megalodon was up to 18 m (59 ft) in length. Its skeleton was heavily calcified. They had about 276 teeth in 5 rows.
Fossil Range	Cenzoic era - Middle Miocene to end of Pliocene. Became extinct due to oceanic cooling, sea level drops, decline in food supply, and new competition.
Mode of Life or Habitat	Adults were not abundant in shallow water environments, and mostly lurked offshore. They gave birth to their young in shallow water environments. They preyed upon whales, porpoises, sea turtles, etc.
Additional Information	Megalodon means "big tooth" in Greek.

Superorder Batoidea (Rays)

This fossil will only be tested at the State and National levels.

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Common Names	Skates and Rays
Physical Description	They have flattened bodies with wing-like pectoral fins and whip-like tails. Their eyes are on top of their bodies with their gills under. They have heavy, rounded teeth for crushing the shells of prey.
Fossil Range	Early triassic
Taxonomy	Contains more than 500 species, and 13 families.

Class Actinopterygii (ray-finned)

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Physical Description	They possess lepidotrichia or “fin rays.” Size ranges from 0.3in to 36 feet!
Fossil Range	Late Silurian - recent
Mode of Life or Habitat	They feed on algae, diatoms, insects, and smaller fish. Freshwater and marine environment.
Adaptations Over Time	They were the first ever bony fish! The swim bladder evolved into a more efficient organ in the teleost making them neutrally buoyant.
Distribution	Remains have been found in Russia, Sweden, and Estonia
Additional Information	Actinopterygians are the dominant class of vertebrates, comprising nearly 99% of the over 30,000 species of fish. They account for half of living vertebrates

Genus Knightia

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Physical Description	Knightia has heavy scales and small, conical teeth. They were typically 3-5 inches long - the longest was Knightia eocaena which grew up to 10 inches long.
Fossil Range	Early Eocene.
Mode of Life or Habitat	Freshwater lakes and rivers. Ate small marine organisms like plankton, diatoms, algae, etc. They travelled in large schools. Were an abundant food source for larger predators.
Distribution	North America and Asia
Additional Information	Knightia is the state fossil of Wyoming - they are abundant in the Green River formation. They are the most commonly excavated fish in the world!

Genus Xiphactinus

This fossil will only be tested at the State and National levels.

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Common Names	"Bulldog fish"
Physical Description	The tail is forked, and attached to a narrow base. At 25-30 feet long, it was the largest bony fish of the Cretaceous. The jaw is very mobile, and therefore able to take in large prey.
Fossil Range	Cretaceous. They became extinct due to the Cretaceous-Paleogene extinction.
Mode of Life or Habitat	Shallow and deep marine. They ate fish, seabirds, and maybe pterosaurs.
Additional Information	Their name comes from the Latin & Greek for “sword ray.” State fossil of Kansas.

Class Sarcopterygii (lobe-finned)

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Physical Description	Their fins differ from those of all other fish - each is on a fleshy, lobelike stalk extending from the body.
Fossil Range	Late Silurian to recent.
Mode of Life or Habitat	They live in a combination of aquatic and terrestrial environments, hibernating while on land. They are ovoviviparous, and they have lungs and gills.

Genus Eusthenopteron

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Common Names	Fish with Legs.
Physical Description	They were 5-6 feet long, and covered in scaly skin.
Fossil Range	Late Devonian
Mode of Life or Habitat	They lived in shallow waterways, and preyed on smaller fish.
Adaptations Over Time	They have a close relationship to tetrapods.
Additional Information	The name means “strongly developed fins” (Greek).

Genus Latimeria (Coelacanth)

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Physical Description	They are 200cm long and weigh 80 kg.
Fossil Range	Middle Pleistocene to recent.
Mode of Life or Habitat	They are found in deep reefs and volcanic slopes - both freshwater and marine environments.
Additional Information	The name is from the Greek words "koilos" meaning “hollow” and "akantha" meaning “spine.” They live very long - possibly up to 80-100 years! They are one of the most endangered genus of animals in the world.

Genus Tiktaalik

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Physical Description	3 to 9 feet long. The eyes were on the top of the skull, rather than the sides. The shoulders were not connected to the skull, so it had a functional neck.
Fossil Range	Late Devonian
Mode of Life or Habitat	They ate smaller fish and bug-like creatures. It is unlikely that they could live entirely on land.
Adaptations Over Time	They were an extremely important transitional form between fish and tetrapods.
Additional Information	There is only one species: Tiktaalik rosae. "Tiktaalik" means "large freshwater fish" (Inuktitut language)

Class Amphibia (Amphibians)

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Physical Description	Changes in anatomy allowed the upper body to be propped up for breathing, the head to turn, and created a rigid structure strong enough to support walking. Their eyes are larger than their predecessors because eyesight is more important on land than in water. They can weigh up to 500 pounds.
Fossil Range	Devonian to recent.
Mode of Life or Habitat	Marine and terrestrial. Carnivorous.
Adaptations Over Time	They may have moved to land because of seasonal droughts and escape from drying pools, or maybe because they were carnivores and the land had a lot of arthropods which they could eat.
Additional Information	"Amphibia" means “double life” and refers to a life cycle that includes an aquatic existence and a terrestrial existence.

Genus Acanthostega

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Physical Description	1 meter long. They had 8 fingers on each hand linked by webbing - no wrists.
Fossil Range	Late Devonian
Mode of Life or Habitat	Shallow, weed-choked swamps.
Adaptations Over Time	In general, they were pretty poorly adapted for going on land (for example, joints weren't very mobile, shoulder and forearm were very fish-like, ribs were too short to support chest out of water).
Additional Information	The name means "spiny roof."

Genus Eryops

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Physical Description	Usually 1.5 - 2 meters long, but could grow up to 3 meters long, making them some of the largest land animals of their time. Average mass was 90 kg. They had an unusually large skull and mouth, with many teeth. The shoulder girdle is disconnected from the skull for improved terrestrial locomotion.
Fossil Range	Mainly Permian - appeared in the Pennslvanian epoch.
Mode of Life or Habitat	Predator - large fish and aquatic tetrapods. Habitat was lowland habitats in and around ponds, streams, and rivers - juveniles probably lived in swamps which gave them protection from predators, while adults spent most of their time on land.
Distribution	Southwestern United States.
Additional Information	Name means "drawn-out face."

Genus Diplocaulus

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Physical Description	Up to 1 meter in length. They had a distinct boomerang-shaped head. Skulls are up to 16 inches wide across the horn tips. Their mouth gape was very small because the lower jaw hinge was posterior to the eye sockets.
Fossil Range	Late Permian.
Mode of Life or Habitat	Rivers, lakes, swamps. They ate insects and fish.
Adaptations Over Time	Their head shape could have been defensive because predators would have a hard time trying to swallow such a large head.
Distribution	North America and North Africa.
Additional Information	Name means "double caul."

Class Reptilia (Reptiles)

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Physical Description	They range from 17 mm to 6 m in length. They have a 3-chambered heart with 2 atria, 1 ventricle, and 2 aortas. They use lungs to breathe. Their skin is rather thin so it is often covered in scales.
Fossil Range	Pennsylvanian to recent. They were dominant during the late Paleozoic and Mesozoic.
Mode of Life or Habitat	They are oviparous, and they shed their skin continuously throughout their lifetimes. Most are insectivorous or carnivorous

Order Crocodilia (crocodiles)

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Order Testudines (turtles)

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Order Icthyosauria (Ichthyosaurs)

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Physical Description	Usually around 2-4 meters in length. They could swim at speeds up to 25 mph. They have the largest known eyes of any reptile.
Fossil Range	Early Triassic to Late Cretaceous. They were the most abundant in the late Triassic and early Jurassic.
Mode of Life or Habitat	Carnivorous, viviparous. Sight was their main sense, and their hearing may have been poor.
Distribution	All Mesozoic oceans - Europe and Asia.
Additional Information	Their name means "fish lizard."

Order Squamata

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Family Mosasauridae (Mosasaurs)

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Physical Description	They were anywhere from 2.5 to 17 meters long. Their jaws were double-hinged and flexible, so they would often gulp down their prey whole. They had an expanded chest region, suggesting that they had 2 lungs.
Fossil Range	Late Cretaceous
Mode of Life or Habitat	Warm, shallow seas. They were dominant marine predators. They were viviparous.
Distribution	Worldwide.
Additional Information	They are probably related to snakes due to similarities in their jaws and skulls.

Order Plesiosauria (Plesiosaurs & Pliosaurs)

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Physical Description	They were anywhere from 3 to 20 meters long. They had a broad, flat body and a short tail. Their necks had up to 70 vertebrae. Plesiosaurs had long necks, small heads, and were slow, while pliosaurs had shorter necks, large heads, and were apex predators. They had a euryapsid skull.
Fossil Range	Late Triassic - Late Cretaceous. Became extinct in the Cretaceous-Paleogene extinction event.
Mode of Life or Habitat	Oceanic environment. Plesiosaurs ate fish and cephalopods. Pliosaurs ate fish, cephalopods, sharks, ichthyosaurs, and even plesiosaurs.
Adaptations Over Time	They have two main morphs - plesiosaurs and pliosaurs.
Distribution	Worldwide
Additional Information	Their name comes from the Greek "plesios" meaning "near to" and "sauros" meaning "lizard."

Order Pterosauria (Pterosaurs)

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Clade Dinosauria (Dinosaurs)

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Order Saurischia (lizard-hipped)

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Suborder Theropoda

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Genus Allosaurus

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Genus Coelophysis

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Genus Dilophosaurus

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Genus Spinosaurus

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Genus Tyrannosaurus

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Genus Velociraptor

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Suborder Sauropodamorpha

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Genus Brachiosaurus

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Genus Diplodocus

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Genus Patagotitan

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Genus Plateosaurus

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Order Ornithischia (bird-hipped)

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Infraorder Anklyosauria

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Genus Ankylosaurus

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Infraorder Ceratopsia

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Genus Triceratops

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Genus Protoceratops

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Infraorder Ornithopoda

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Genus Iguanodon

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Genus Parasaurolophus

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Genus Maiasaura

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Infraorder Pachycephalosauria

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Genus Dracorex

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Infraorder Stegosauria

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Genus Stegosaurus

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Class Aves (Birds)

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Genus Archaeopteryx

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Physical Description	A feathered dinosaur that could be the size of a bluejay to a chicken. Looked similar to a theropod other than the fact that it had feathers.
Fossil Range	Late Jurassic
Distribution	Europe

Genus Titanis (Terror Bird)

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Physical Description	Large flightless carnivore bird. It could reach heights of about 2.5 meters and usually weighed around 150kg. It can most easily be recognized by its large skull and hooked beak.
Fossil Range	Pliocene-Early Pleistocene
Distribution	North America

Genus Icthyornis

This fossil will only be tested at the State and National levels.

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Clade Synapsida

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Mammal-like Reptiles

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Genus Dimetrodon (pelycosaurs)

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Physical Description	They grew up to 3.5 meters long. They have 2 types of teeth - shearing teeth and canine teeth. They have a sail supported by spines sprouting from the vertebrates.
Fossil Range	Permian to Cisuralian.
Mode of Life or Habitat	They were an apex predator.
Adaptations Over Time	Their sail had many uses, such as thermoregulation, sexual display, looking larger to predators, and stabilization of the spine.
Distribution	Mainly Southwestern US, but also Europe.
Additional Information	"Dimetrodon" means "2 measures teeth."

Genus Lystrosaurus (therapsids)

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Physical Description	About 3 feet long. They don't have any teeth besides the tusk-like upper canines. They had huge forearms - thought to be a powerful burrower.
Fossil Range	Late Permian to Early Triassic.
Mode of Life or Habitat	Desert-like landscape. They were herbivores, and ate plants and roots.
Adaptations Over Time	They survived the Permian-Triassic extinction event.
Distribution	Mainly Africa.
Additional Information	"Lystrosaurus" means "shovel lizard." For a while, 95% of all land vertebrates were Lystrosaurus. They are good index fossils.

Class Mammalia (Mammals)

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Genus Basilosaurus (prehistoric whale)

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Genus Equus (modern horse)

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Genus Australopithecus (hominin)

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Genus Homo (hominin)

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Species H. neanderthalensis

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Species H. erectus

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Species H. sapiens

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Genus Mammut (Mastodon)

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Physical Description	Usually around 2.3 meters tall at the shoulders. Could weigh up to 4.5 tons. They had low-crowned or “bunodont” cheek teeth covered in thick enamel. They had 2 or 3 teeth in each half of the jaw.
Fossil Range	Late Miocene-Late Pleistocene
Mode of Life or Habitat	They lived in forests. Their social groups consisted of females and young, while the males abandoned the mixed herds once reaching sexual maturity and lived either alone or in male bond groupings. They mainly ate trees and shrubs.
Distribution	North and Central America, less common in Africa and Eurasia
Additional Information	Their name means "nipple tooth."

Genus Mammuthus (Mammoth)

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Physical Description	About as large as a modern Asian elephant - 2.5 - 3 meters tall at the shoulder. The teeth consisted of a series of plates surrounding a dentine core. They were held together in a matrix of dental cement.
Fossil Range	Early Pliocene-Early Holocene
Mode of Life or Habitat	They ate grasses, fruits, shrubs, etc. Baby mammoths ate the dung of the adults.
Distribution	North America, Eurasia.
Additional Information	The name means “earth” from the Tartar word "mamma."

Species M. primigenius (Wooly Mammoth)

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Physical Description	About the same size as modern African elephants - shoulder height 2.6 - 3.4 meters. They had 4 functional molars at a time. The tusks in males were usually around 2.5 meters long and weighed 45 kg, while in females they were only about 1.5 meters and weighed around 9 kg. They had an outer layer of long hair which was up to 90 cm long. They also had a denser, shorter inner layer of hair.
Fossil Range	Middle Pleistocene to Early Holocene. They became extinct due to climate change or hunting.
Mode of Life or Habitat	Grasses, herbaceous plants, flowering plants, shrubs, etc. Adults needed to eat 6 tons of food daily! They lived in matriarchal family groups.
Adaptations Over Time	They were well adapted to the cold environment of the last ice age - thick layer of fat, fur, small ears (to minimize frostbite), etc.
Distribution	Northern Eurasia and North America.
Additional Information	Their name means "first elephant" in Latin. State fossil of Alaska, Nebraska, and Vermont

Genus Megacerops (Brontothere)

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Physical Description	Up to 5 meters tall. They had an odd number of toes. The dorsal vertebrae above the shoulders had long spines to support the huge neck muscles needed to carry the heavy skull. They had a pair of blunt horns on their snout.
Fossil Range	Late Eocene
Mode of Life or Habitat	The shape of its teeth suggests that it preferred food such as soft stems and leaves, rather than tough vegetation. Adults may have used their horns to defend themselves and their calves from predators.
Distribution	North America
Additional Information	Name means "large-horned face." Closely related to Mesohippus.

Genus Mesohippus (three-toed horse)

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Physical Description	They were about 60 cm tall, 4 feet long, and weighed about 75 pounds. They had three toes.
Fossil Range	Middle Eocene to Early Oligocen
Mode of Life or Habitat	They were herbivores, although their teeth were unsuited to grazing (this trait was adopted in later, more advanced horses)
Adaptations Over Time	Longer legs and longer/larger face than earlier equids. They were faster than earlier horses. They were the first of the three-toed horses.
Distribution	North America
Additional Information	In Greek, "meso" means "middle" and "hippos" means "horse."

Genus Smilodon (saber-toothed cat)

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Physical Description	They weighed up to 400 kg. Their teeth were about 7 inches long and their upper canines were more than 10 inches long. Teeth were fragile, and they had a weaker bite than other big cats. They had a hyoid bone to help them roar. They had shorter but more massive limbs than other felines.
Fossil Range	Pleistocene
Mode of Life or Habitat	They were carnivores - ate bison, elk, deer, etc. They may have lived in social groups. Canines may have been an attraction during mating.
Distribution	North and South America
Additional Information	In Greek, "smile" means "chisel" and "odous" means "tooth." There are hundreds of Smilodon fossils in the La Brea Tar Pits.