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Millions of Years Ago (MYA)

Late Jurassic through the Cretaceous Heyday of Dinosaurs

170 to 65 Million Years Ago





A group of nasty predators, thriving in the late Cretaceous.  "Raptor" is a pop culture term, referring to dinosaurs, most notably the Velociraptor, Deinonychus, Utahraptor and other theropods such as Oviraptor.  Dromaeosauridae is the more acceptable (but less colorful) name for these bird-like structured theropod dinosaurs. They were small to medium-sized, possibly feathered carnivores.

The informal term "raptor" (after Velociraptor), popularized by the film Jurassic Park will probably remain in popular usage. Technically, the name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'.

"Theropods" refer to all two legged dinosaurs, with the word literally meaning "beast feet."  Raptors varied in size from that of a chicken, to somewhat larger than a human.  Based on size, weaponry including "slashing" claws, sharp serrated teeth and hollow bones (like the modern bird), we can hypothesize that they might have been warm blooded.  We can be reasonably certain that they were relatively swift, extremely dangerous and possibly hunted in packs.

Saurornitholestes/Dromaeosaur Raptor Claw with all Foot Bones

Hell Creek Formation, Northern MT

Raptor Teeth Newborn Babies (Group View)

Raptor Teeth Newborn Babies (Enlarged View)

Hell Creek, Montana

Raptor Dromaeosaur Radius Arm Bone

Hell Creek Formation, North East Montana

Oviraptor or Dromaeosaur Tibia

Channel Deposit Garfield County, Hell Creek MT

Raptor (probably Dromaeosaur) Femur Segment

Hell Creek, SD

Raptor Rib in Matrix

Lance Creek, Wyoming

Raptor Teeth

Hell Creek Channel Deposit, SE Montana

Raptor Small Crystallized Limb end

Hell Creek, Montana

Theropod Claws Unidentified Species

Channel Deposit, Eastern MT






Very rare, with partial fossil remains found only in the Two Medicine Formation North of Dupyer, Montana dating around 75 million years ago.  Probably the rarest example of the Ceratopsians.  In the same family of dinosaurs as Triceratops, it was smaller at 15 feet/1.5 tons and "odder" in appearance, particularly placement and shape of horns.  Like most herbivores, it probably displayed herd behavior.  Besides bone shape, it is also recognizable by the grey/black tint of bones due to the somewhat unique mineralization of Dupyer Montana area.

Einiosaurus Ulna & Radius (Juvenile)

Einiosaurus Ribs (Adult)

Einiosaurus Ribs (Juvenile)

Einiosaurus Sacrum Vertebra, Upper Jaw Piece

Einiosaurus Sacrum Vertebra (Baby)

Einiosaurus Sacrum Vertebra (Juvenile)

Einiosaurus Humerus

Einiosaurus Teeth

Einiosaurus Frill

Einiosaurus Jugal (Cheek Bone)

Einiosaurus Tail Vertebra & Process

Einiosaurus Vertebra Process

Einiosaurus Foot Bone

All from Two Medicine Formation

North of Dupuyer, Montana.

Never found anywhere else.






A herbivore that could hold its own against the feared T-Rex and one of the two most popular dinosaurs of all time.  Triceratops thrived between 68-65 million years ago.  The function of their frills and three distinctive facial horns has long inspired debate. Although traditionally viewed as defensive weapons against predators, a new theory hypothesizes that these features were primarily used in courtship and dominance displays, much like antlers. 

Most likely, they were used for both, although horn shape and positioning would indicate formidable weaponry potential.  Triceratops was about 30 feet long and weighed at least 6 tons.  It's head, including the frill shield was up to ten feet in length.  Undoubtedly, it would have put up an excellent fight against any of the larger predators, including Tyrannosaurus Rex. 

Somewhat resembling the modern Rhinoceros, the reptile/mammal similarity is an excellent example of what Paleontologists call "Convergent Evolution."  i.e.. If faced with similar environmental challenges, similar characteristics can develop over millions of years in the fight for species survival.  According to the existing fossil record, Triceratops was last of the giant dinosaurs to disappear in the great extinction.


Triceratops Rib & Vert Process on reverse of Matrix

Lance Creek, WY

Triceratops Nose Horn and Horn Bridge

Lance Creek, WY

Triceratops Nose Horn Very Large

Hell Creek Montana

Triceratops Brow Horn Tip

Lance Creek, WY

Triceratops Caudial (Tail Vertebra)

Channel Deposit (sub-surface) Garfield Cty, MT

Triceratops Leg Bone Segment

Hell Creek.  Harding County SD

Triceratops Hoof (Ungual)

Lance Creek, WY

Triceratops Occipital (Rear) Skull Brain Case

Hell Creek.  West Central SD

Triceratops Rib Head in Matrix

West Central, SD

Ceratopsian Frill

Lance Creek, WY

Triceratops Beak and Snout

Lance Creek, WY

Triceratops Scapula Shoulder Blade Distal (lower) End

Hell Creek, West Central SD

Triceratops Frill & Skull

Lance Creek, WY

Triceratops Frill in Matrix

Lance Creek, WY

Triceratops Jaw Sections 01

Hell Creek, N.W. SD

Triceratops Jaw Sections 02

Hell Creek, N.W. SD

Triceratops Teeth

Harding County, SD





Largest and most well known of the North American carnivores, it was probably both a predator and scavenger, although Paleontologists devoted to T-Rex lore will argue.  The skull alone could be as much as five feet in length, with a total length of about 40 feet.  Weight is approximated at six tons.  As an aside, Paleontologists can judge carnivore vs. herbivore bone derivation with about 90% accuracy. The internal structure of carnivore bones are usually "honeycombed" or granular in look, possibly caused by their diet.

Tyrannosaurus Rex Cervical (Neck) Vertebra

Hell Creek, N.W. SD

Tyrannosaurus Rex Centrum Vertebra Processes

Hell Creek, N.W. SD

Tyrannosaurus Rex Leg Bone Probably Femur

Hell Creek North of Baker Montana

Tyrannosaurus Rex Leg and Toe Bone

Hell Creek North of Baker, MT

Carnivorous Theropod Bone

Lance Creek, WY

Tyrannosaurus Rex Tooth Juvenile

Lance Creek Formation near Newcastle, WY

Tyrannosaurus Rex  Teeth

Buffalo SD & North of Baker Montana

Tyrannosaurus Rex (or Nano) Premaxillary Tooth

Hell Creek Formation, MT

Tooth From Juvenile

Hell Creek Formation, MT






This genus was first known from Egyptian remains discovered in 1910. The original remains were destroyed in World War II, but additional skull material has come to light in recent years in North Africa.  Somewhat larger than Tyrannosaurus Rex, it's non-serrated teeth lead experts to believe that it might have lived on a diet of large fish. The large back "sail" has been hypothesized to have been used for either intimidation or courting, but we really don't know.


Spinosaurus Teeth

Baharija Formation, Kem Kem Morocco




Middle Cretaceous


Not a "heavyweight" like the North American T-Rex or North African Carcharodontasaurus, Deltadromeus or "Delta Runner" was long in size but relatively light and limber for running down prey.  In size, Deltadromeus approached 30 feet in length and weighed approximately 3 tons.

It has only been found in North Africa where it's long, slender "runners" legs must have made it much feared. Skeleton artifacts have been found with remains of Spinosaurus (above) and Carcharodontasaurus (below).

Deltadromeus Agilis Tooth Very Large

Deltadromeus Agilis Tooth-01

Deltadromeus Agilis Tooth-02

Red Sandstone beds, Tegana Formation Kem Kem Morocco








A carnivore, with enormous jaws and long, serrated teeth up to eight inches long.   Very similar to T-Rex and a bit larger, it is found in North Africa.  During the Cretaceous period, North West Africa possessed a lush, swampy environment, rather than the stark, dry, desert of today.  As with Spinosaurus (above), the original discovered remains were destroyed in World War II, but new finds were made in 1996.

Carcharodontasaurus Teeth

(Two at Right) Tegana Formation,

Taouz, Morocco

(Left Bahariji Formation,

Kem Kem Morocco






A large herbivore nicknamed the "Duck Bill Dinosaur," it could walk on two or four extremities.  The most well known sub-species is Edmontosaurus.  Most common, varied, and well-adapted of the ornithopod (bird-hipped) dinosaurs.  This unique group of dinosaurs grew in sizes to over 40 feet and probably weighed over 5 tons! In-depth studies of a variety of duckbill remains indicate that they walked predominantly on all fours but had the ability to stand on their hind legs.

Edmontosaurus Skin & Shoulder Blade same animal

Edmontosaurus Vertebra with Spinal Cord Cast

Edmontosdaurus Fibula

Hell Creek Formation, MT

Edmontosaurus Metatarsal (Foot Bone)

Hell Creek Formation, NW South Dakota

Hadrosaur Ulna Juvenile (lower arm bone)

Hell Creek Formation, NW South Dakota

Edmontosauaurus Humerus Distal End

Hell Creek Formation, MT

Edmontosaurus Femur End

Lance Creek, WY

Hadrosaur Chevron & Rib Parts in Matrix

Lance Creek, WY

Hadrosaur Tail Vertebra

Channel Deposit, Hell Creek MT

Hadrosaur Egg 01

Hadrosaur Egg 02 (Natural Preparation)

Kaugo Formation, Xixia basin, Hunan China

Edmontosaurus Rib Head & End Tip

Skull Stripe, Vertebra, Foot Bones

All from Hell Creek Formation, N. Baker Montana



"Egg Mountain" Two Medicine Formation MT USA





There has been much speculation as to whether Dinosaurs were maternal.  The speculation is that some were and some were not.  We don't really know, but can glean a logical deduction from the fossil record.

Some Dinosaur finds involve what seems to be the remains of large communities.  Equally telling is the discovery of group nesting areas. 

Most have been uncovered in Central Asia and the Patagonia region of Argentina.  But this changed in 1978 at what came to be called "Egg Mountain" in the Two Medicine Formation of Montana, U.S.A.  There was a discovery of some fourteen dinosaur nests, convincing many Paleontologists that at least some species of dinosaurs lived in large colonies to care for their young.

This raised speculation that dinosaurs, most particularly the "bird-like" species were maternally driven, although some Duck Bill varieties seemed to also.

It was further hypothesized that since most all egg discoveries were crushed, this might indicate that the young didn't simply walk away unattended.

Adding to this, the Egg Mountain U.S.A. find revealed "layering" of egg shells, reinforcing the possibility of nesting areas.  We don't know any of this for certain, but it's interesting speculation.






Dinosaur Eggs found in the United States

Two Medicine Formation, Egg Mountain Montana

Oviraptor Egg Segment

Nanxiong Formation, Guangdong Provice China

Hadrosaur Egg 01

Hadrosaur Egg 02 (Natural Preparation)

Kaugo Formation, Xixia basin, Hunan China

Titanosaur Egg

Rio Colorado Formation

North West Patagonia, Argentina

Saltasaurus Very large egg shell section from matrix

Patagonia, Argentina

Saltasaurus large egg shell section from matrix

Patagonia, Argentina








Named after the western Alberta State of Canada where it is most frequently found.  A predator somewhat predating T-Rex, they are both in the family of Tyrannosauridae.  Albertosaurus had a similar body appearance as T-Rex, but was smaller at somewhat under 30 feet in length and approximately 2 tons.  As with T-Rex, the forelimbs were extremely small and ended in two claws.  It's hind legs had 3 primary toes.  Finding a large amount of remains together leads some to believe it might have displayed pack behavior.


Albertosaurus Teeth

Foremost Beds, S.E. Alberta Canada




Richardoestesia is a medium sized theropod dinosaur from the late Cretaceous Period of North America.  Little is known of this creature.  Physiology is reconstructed from a single pair of lower jaw bones and a large number of isolated teeth. The jaws are slender and rather long but the teeth are small and finely serrated. It has been suggested that Richardoestesia was a fish eater, but most likely, it was a hunter of opportunity. Because so little is known of the animal, its relationships are unclear. However, the jaws resemble Archaeopteryx, Troodontidae and some Dromaeosauridae, in having a strong groove on the lateral surface.  It is estimated to have weighed approximately 220 pounds.


Richardoestesia Teeth

Hell Creek, Powder River County MT






Late Cretaceous

A small dinosaur originally found in Mongolia, its name means "Egg Seizer."  Originally discovered lying on a group of eggs, it was hypothesized this dinosaur was an egg thief.  This theory has been subsequently disproven to some extent although eggs of other species might have been a portion of its diet.   Birdlike in physiology, it is probably not an early avian.  On the other hand, it is felt to have been a meat eater. 

A member of the suborder Theropoda, Oviraptor grew to a length of up to 2.7 m (9 ft). It walked upright, balancing itself with its heavy tail, and had long, powerful forelimbs.  This dinosaur had a short head and a strong, curved, toothless beak. Bony prongs inside its mouth appear similar to the throat tooth of egg-eating snakes but we can only speculate.  Oviraptor probably lived near lakes where it may have fed on freshwater mussels, crushing the shells with its powerful beak. This dinosaur had a hornlike crest on its nose.


Oviraptor Claw

Hell Creek Formation, Montana

Oviraptor Egg Segment

Nanxiong Formation, Guangdong Provice China

Oviraptor & Other Eggs found in the United States

Two Medicine Formation, Egg Mountain Montana







(Pteranodon sternbergi)



(Anhanguera sp)



Pteranodon sternbergi

Pterosaur or "winged lizard" were flying reptiles, not dinosaurs.  According to the fossil record, they existed from the late Triassic to the end of the Cretaceous or 220-65 million years ago.  They are the earliest vertebrates known to have evolved powered flight.  Some feel their aerodynamic characteristics would preclude flight in our existing atmosphere.  They speculate that the heavily oxygenated atmosphere of their own environment, gave them sufficient airworthy attributes to accomplish this.  In any event, they probably soared like an Albatross.

Pterosaur wings were formed by a membrane of skin, muscle and other tissue, stretching from the ankles to a fourth finger, somewhat similar to a bat.  Some had teeth and some didn't.  Some had ornate skull crests and some did not.  It is speculated that some might have had the rudiments of feathers.

Wingspread averaged from 15 to 35 feet, although you cannot necessarily equate this large size to weight.  They tended to be fragile relative to land reptiles, with thin, hollow bones much like modern soaring birds of flight.  Graceful in the air, on ground they were clumsy and fell relatively easy victim to predators unless taking to the air in time.

In North America, the most prevalent Pterosaur fossils are of Pteranodon or "winged toothless."   According to the fossil record, this blade-like crested Pterosaur was wide spread during the late Cretaceous and had a wingspan of almost 25 feet.  Fossils of Pteranodon sternbergi are most widespread, having been found in Kansas, Nebraska, Wyoming and other states that made up part of the Western Interior Seaway, separating the eastern and western land masses.  It is speculated that Pteranodons who couldn't successfully navigate the long flights for nesting or fishing expeditions, perished in what was once an inland sea.

Pterosaur Pteranodon Sternbergi Wing Bone

Niobrara Chalk, Smoky Hill River West, Kansas

Pterosaur (Anhanguera sp) Front Tooth

Red Sandstone beds, Tegana Formation Kem Kem Morocco

Pterosaur Tooth

Sandstone Deposit, Qued Zem, Morocco







Troodon is a genus of relatively small, bird-like dinosaur from the Late Cretaceous, 75-65 mya. Discovered in 1855, it was among the first dinosaurs found in North America. Its name  is Greek for "wounding tooth", referring to the dinosaur's teeth, which bore prominent serrations.  At the very least, it was omnivorous.  Troodon was a small dinosaur, around 6.5 feet in length, 3 feet tall, and weighed about 130 pounds. It had very long, slender limbs, suggesting that the animal was able to move quickly. It had large, retractable sickle-shaped claws on its second toes, which were raised off the ground when running.

Troodon Tooth

Dinosaur Park Formation

S.E. Alberta Canada

Troodon Vertebra (Juvenile)

Hell Creek, MT





Late Jurassic (155-145 MYA)

A herbivore of the late Jurasic, early Cretaceous.  The name means "bent lizard," because, when standing on all fours, its body must have been arched.  Smaller than the Hydrosaur that appear later, they have many physical similarities.  It is estimated to have been about 20 feet long and weighed around 1,000 pounds.


Camptosaurus Leg Bones

Morrison Formation, Big Horn Basin WY



Thescelosaurus meaning marvelous Lizard in Greek, was a genus of small ornithopod dinosaur that appeared at the very end of the Late Cretaceous period in North America.
Skeletons and skulls, indicate it grew to between 8 to 13 feet in length. It had sturdy hind limbs with four hoof like claws and small wide hands with five fingers. It's head was elongated with a pointed snout. This genus of dinosaur is regarded as a specialized herbivore, but might have been an omnivore.
The genus attracted media attention in 2000, when a specimen unearthed in 1993 in South Dakota was interpreted as including a fossilized heart, although there is much debate as to whether or not it really was a heart.

Thescelosaurus Various Teeth

Hell Creek, Montana

Thescelosaurus Premaxilla +7 Maxilla back. Same animal

Powder River County, MT

Thescelosaurus Jaw Section

Hell Creek Formation near Jordan MT

Thescelosaurus Jaw Section with Roots and Toe Bone

Found together in Hell Creek, MT

Thescelosaurus Juvenile Ungual (Foot Claw)

Hell Creek Formation, Eastern MT






Although a complete skeleton has not been discovered, Ankylosaurus is often considered the archetypal armored dinosaur.  The largest was Euoplocedphalus.  This herbivore's defense was an armored body and massive bony tail club.  From head to tail, they averaged some 20 feet in length, with an estimated weight of somewhat over 2 tons.  Certainly, predators of the Cretaceous would think twice about attacking this formidable creature.

Although a reptile, it shares interesting superficial physical qualities with the giant Ice Age mammalian Glyptodonts and Armadillos of the Pleistocene, some 65 million years later.  This "convergent evolution" may be due to similar environmental conditions and defense needs, or just coincidence. 

Ankylosaurus Extending Armor Spike

Hell Creek, MT

Ankylosaurus Teeth & Armor Plate Segment

1 Pre-Molar - Lance Creek Wyoming

2 Molars - Judith River Form. N. Lewistown MT

Scute Section - Harding County, SD

Ankylosaurus Armor Plate (Scute) Complete

Judith River Formation, Alberta Canada

Ankylosaurus Armor Plate (Scute) Large

Hell Creek, Montana

Ankylosaurus Armor Plate (Scute) Juvenile

Hell Creek, Montana







One of the "armored" dinosaurs of the late Jurassic, it is known for the bony plates creating an "armored" ridge, accompanied by a set of tail spikes.

While only a few examples of Stegosaurus exist, much has been speculated.  Some claim that the plates running the spinal ridge were for defense.  Others have hypothesized that they were thermal plates, used to dissipate heat.  We'll never really know, although the tail spikes were most likely used for defense.

Fossils have been found in Western North America, particularly in the Morrison formation that spans several states.  The brain cavity of this herbivore was quite small for an animal that was up to 30 feet in length.  Weight is estimated to have been somewhat over 2 tons.

Stegosaurus Femur - Tibia Joint

San Rafael Swell, South Eastern Utah





Very little information exists, other than the many similar teeth found in several areas of the United states and Asia in late Cretaceous period strata. It may be that this is not a distinct species at all and the teeth come from a juvenile tyrannosaurid. Recently, a partial skull was found in Montana that some feel may partially unravel the Aublysodon mystery.  The teeth are similar and as an interesting point, the skull shows a long, low snout with a species specific uncommon step in the lower jaw.  Length is estimated to be about fifteen feet.  But the story is rather incomplete although teeth have been found in several states.  Where are the fossil bones?  Your guess is as good as anyone else's.


Aublysodon Tooth

Hell Creek, Montana

Aublysodon Teeth

Hell Creek, Powder River County MT



Pachycephalosaurus means "thick headed lizard." It lived during the Late Cretaceous Period  of what is now North America. Remains have been excavated in Montana, South Dakota, and Wyoming. It was a herbivorous or omnivorous creature which is only known from a single mostly complete skeleton, almost complete skulls, a few extremely thick skull roofs and assorted, incomplete fossil remains. 

It is estimated to have been 16 feet in length and to have weighed some fifteen hundred pounds.  Large bone segments are rare.  Some Paleontologists have hypothesized that Pachycephalosaurus is the same species as the similar and equally rare Stygimoloch spinifer. Nobody really knows for sure. 

Pachycephalosaurus Snout with Spikes

Lance Creek Wyoming

Pachycephalosaurus Femur Leg Bone, Left Side

Lance Creek Wyoming

Pachycephalosaurus Skull Knob & Spike

Lance Creek, Wyoming

Pachycephalosaurus Teeth

Butte County, South Dakota

Pachycephalosaurus Toe Bone (Unprepped)

Hell Creek Formation near Jordan Montana






Plesiosaurs means "near lizard."  It was a carnivorous, aquatic, non-dinosaur reptile.  Many have been found in England, some of them virtually complete, and new discoveries are made frequently.  Some grew to sixty feet in length.  Paleontologists have joked about this strange reptile, calling it a large snake, strung through the shell of a giant turtle.  Naturally, this deadly predator was neither.


Plesiosaur Femur Bone with Vertebra

Portland Dorset UK

Plesiosaur Humerus Bone

Kimmeridge Clay, Portland Seabed Dorset,  UK

Plesiosaur Vertebra with Process & Pectoral Bone

North Yorkshire Coast, UK

Plesiosaur Tooth

Khouribgha, Morocco




Some paleontologists consider this vicious, reptilian marine predator to be a relative of sea-snakes, but nobody really knows.  Mosasaurs breathed air and were powerful swimmers, well-adapted to living in the warm, shallow seas, prevalent during the Late Cretaceous Period. Mosasaurs were so well adapted to this environment that they gave birth to live young, rather than return to the shore to lay eggs, as sea turtles do.  Some were more than thirty five-feet long.


Mosasaur Vertebras+Squalicorax shark tooth Matrix

Niobrara Formation, Western Kansas

Mosasaur Vertebra Complete & Unprepped

Southern South Dakota

Mosasaur Ulna

Sulfur River Ozan Formation, NE Texas

Mosasaur Rear of Jaw

Ozan Formation, Taylor Shale Group TX

Mosasaur Tooth with Root in Matrix

Atlas Mountains, Morocco

Mosasaur  Teeth (4) Exceptionally large

1 Atlas Mountains, Morocco

3 Oued Zem Morrocco

Mosasaur Snout Tip of Juvenile with Tooth Roots

Ozan Formation, Sulphur River NE TX

Mosasaur Vertebra

Ozan Formation, Taylor Shale Deposits N.E. TX

Mosasaur Tail Vertebra

Pierre Shale Deposits, W. Kansas

Mosasaur Ribs in Shale

Alberta, Canada









These were the giants of the dinosaurs although as with virtually all the others, we know little about their lifestyle.  What we do know, we glean from the fossil record containing some relatively complete specimens and far more incomplete examples.

We can be reasonably certain that they were herbivores, given their peg-like teeth used to strip vegetation from trees.  They were obviously too slow and ponderous to be predators.  On the other hand and with the exception of the young or old, it is probable that predators of the day kept a wide berth.

As with non predators of today, they probably congregated in herds.  In that way, these relatively slow giants could protect their young.

Were they good parents?  We don't really know, although poor parenting would have resulted in their being less successful. 

It was formerly felt that dinosaurs in general laid their eggs and walked away, but extrapolation from modern reptile lifestyle makes this highly unlikely.

Alligators and other crocodilians tend to be good parents, watching over their young until they are reasonably capable of surviving on their own.  There is no reason to believe that this didn't exist among the dinosaurs and particularly among the Sauropods.

Size of Sauropods varied from very large to extreme.  Most were between 80-100 feet in length with an estimated weight of 90-100 tons.  Their fossils can be found widely throughout much of the world.


Diplodocus Rib Mineralized

Morrison Formation (Late Jurassic) South East Utah

Sauropod Scapula (Shoulder Blade) Distal End possibly from Juvenile Diplodocus

Morrison Formation (Jurassic), Montana

Sauropod Fibula (?) Segment with Quartz Crystals

Morrison Formation (Late Jurassic) South East Utah





Rebbachisaurus is a genus of sauropod dinosaurs, up to sixty-eight feet long.  It lived in the Early Cretaceous period, about 99 million years ago. This massive four-legged plant-eating animal had a small head, a long, graceful neck and a whip-like tail. Rebbachisaurus is distinguished from other sauropods by its unusually tall, ridged back.  It has the typical "chisel" tip teeth of large herbivores, for stripping leaves off branches.

Rebbachisaurus Tooth

Kem-Kem Morocco

OMITHOPSIS humerocristatus



(Late Jurassic through Cretaceous)


Popularly and somewhat incorrectly called "The Jurassic Coast," this area is rather rich in four legged giant Sauropods.  Sauropoda or the Sauropods are notable for the enormous sizes attained by some species.  The group includes many of the largest animals to have ever lived on land. Well-known genera include Apatosaurus (formerly known as Brontosaurus), Brachiosaurus and Diplodocus. One of the rarest is Omithopsis humerocristatus, nicknamed "The Portland Dinosaur," of which barely more than vertebra have been found.  Based on analysis, it is fair to assume that it was rather like Diplodocus or Brachiosaurus, possibly smaller at 50 feet in length.  Like the other large Sauropods, it was vegetarian, but sufficiently large for adults to keep Theropod predators at bay.

Omithopsis humerocristatus Tail Vertebra

Kimmeridge Clay Deposits,

Portland Harbor, UK








(Mid-Late Cretaceous)


A diverse group of herbivore sauropod dinosaurs, which included Saltasaurus and Isisaurus. It includes some of the heaviest creatures ever to walk the earth, some of which might have weighed up to 100 tons. Others were significantly smaller.  Because of their immense size, they were named after the mythological Titans.  Titanosaurs had small heads and a crest formed by nasal bones.  Legs were somewhat short for their size, with broad sided bodies.  They were widespread in Southern Continents.  The Rio Colorado Formation (now called a Sub Group) in North West Argentina has proven rich in Cretaceous dinosaur fossils between 83-75 million years old.

Saltasaurus was not one of the larger Titanosaurid Sauropods, weighing in at approximately 10 tons and up to 40 feet in length.  On the other hand, it was heavily protected with bony armor plate, similar to the Ankylosaurus. 


Titanosaur Egg

Rio Colorado Formation

North West Patagonia, Argentina

Saltasaurus Very large egg shell section from matrix

Patagonia, Argentina

Saltasaurus large egg shell section from matrix

Patagonia, Argentina








Crocodiles are among the most successful of reptiles, surviving several mass extinctions.  This is probably due to their living in an aquatic environment, more immune to the climatic change and pollution that doomed the land reptiles.

 Phobosuchus riograndensis was the hugest discovered to date, living about 70 million years ago in the late Cretaceous. It was about 50 feet long, with a head extending some 6 feet in length.
Fossilized remains of Phobosuchus have been found in Texas which was under water during the Cretaceous. Crocodiles are saltwater reptiles, venturing into coastal marshes, lakes, and rivers.


Other Cretaceous crocodiles were also large.

One was Crocodilus cf. spenceri, now renamed to Kentisuchus.  Discovered in the Tegana Formation of the Kem Kem phosphate mine region, K’Sar-es-Souk Province, Khouribga, Morocco.  They weighed 5-10 tons and attained a length of 25-40 feet with a four to five foot skull. Land vertebrates including young or small dinosaurs may have been additional victims.  Primarily found in the late Cretaceous (75-65 MYA), examples have been found in the early Eocene (54-45 MYA)

Many early Crocodiles can be recognized by the large bulbous front snout and relatively narrow jaw. 

The last remaining descendant of these Cretaceous Crocodilia is the endangered to near extinct Indian Gharial.


Crocodilus cf. spenceri  a.k.a. Kentisuchus Skull

Tegana Formation of the Kem Kem phosphate mine region, K’Sar-es-Souk Province, Khouribga, Morocco



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