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Dinosaur Facts: Baryonyx

Anatomy

Baryonyx was an unusual theropod with huge 1-foot (30.5-cm) long claws on its hands, and long, narrow, crocodile-like jaws with 96 small, serrated teeth (this is 1.5 times the number of teeth that most other theropods had). It had a small crest on its snout. Baryonyx had a long, straight neck (unlike other theropods, who had s-shaped necks) and a long tail. Its low-slung body was supported by 2 large rear legs and 2 slightly smaller arms. It was a carnivorous dinosaur from the early Cretaceous period, about 125 million years ago. This predator was about 32 feet (9.5 m) long, weighing perhaps over 2 tons.

When Baryonyx lived
Baryonyx lived during the early Cretaceous period, about 125 million years ago, in what is now England.

Behavior

Baryonyx

Intelligence
Baryonyx was a theropod, whose intelligence (as measured by the relative brain to body weight, or EQ) was high among the dinosaurs.

Diet and teeth
Baryonyx was a carnivore, a meat eater with huge claws and many small, sharp teeth in powerful, crocodile-like jaws. It had 64 teeth in the lower jaw but only 32 teeth in the upper jaw (the upper teeth were larger than the lower teeth).

Baryonyx was a large predator that ate fish. A fossilized Baryonyx was found with a fossilized meal in its stomach; this stomach contained fish scales, fish bones, and some partially digested bones of a young Iguanodon. So far, Baryonyx is the only known dinosaur that ate fish. It may have waded in rivers and shallow seas to catch fish (just as some modern-day bears do).

Locomotion
Baryonyx may have walked on two or four muscular legs. Although the front legs shorter than the rear legs, they were not that much shorter.
Discovery of fossils
Baryonyx was found in 1983 in a clay pit in Surrey, England, by the British amateur fossil hunter William Walker. It was the first carnivorous (meat-eating) dinosaur found in England. About 70% of this dinosaur’s skeleton was found. Baryonyx was found 30 miles south of London, England, in 1983. It was named in 1987 by British paleontologists Angela C. Milner and Alan J. Charig.

Classification
Baryonyx was an early Cretaceous Saurischian (”lizard-hipped”) dinosaur. It was a very unusual theropod. It was a tetanuran belonging to the superfamily Spinosauroidea (related to Spinosaurus) and a Spinosauridae. The type species is B. walkeri.

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Dinosaur Facts: “Bird mimic” Avimimus

Anatomy

Avimimus was about 3 feet (1 m) long and weighed about 33 pounds (15 kg). Avimimus had a long, toothless beak, a very short tail, and very long legs. This dinosaur has tiny ridges running along its arms; some paleontologists think that they may have anchored feathers.

When Avimimus lived
Avimimus lived during the late Cretaceous period, about 85 million-75 million years ago.

Intelligence
Avimimus was an advanced theropod, whose intelligence (as measured by its relative brain to body weight, or EQ) was high among the dinosaurs.

Diet
Avimimus may have been an omnivore, eating small animals, insects, eggs, and some plant material.

Locomotion
Avimimus walked on two long, slender legs. It was a fast, agile dinosaur, probably running about as quickly as an ostrich , which can run up to 43 mph (70 kph).

Discovery of fossils
Four partial skeletons of Avimimus were found in Mongolia. It was found and named by Russian paleontologist Sergei Mikhailovich Kurzanov in 1981.

Classification
Avimimus belonged to the:

Kingdom Animalia (animals)
Phylum Chordata (having a hollow nerve chord ending in a brain)
Class Archosauria (diapsids with socket-set teeth, etc.)
Order Saurischia - lizard-hipped dinosaurs
Suborder Theropoda - bipedal carnivores
Infraorder Coelurosauria - lightly-built fast-running predators with hollow bones and large brains
Superfamily Maniraptoriformes - advanced coelurosaurs with a fused wrist bone
Family Avimimidae
Genus Avimimus
Species portentosus (the type species, Kurzanov)

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Dinosaur Facts: Archelon

Archelon

Anatomy
Archelon was huge marine turtle (a chelonian) that was the size of a car. It lived during the time of the dinosaurs, but it was not a dinosaur. This carnivore was about 10-13 feet (3-4 m) long. Archelon had a wide, flattened shell, paddle-like legs, a long, narrow head, weak jaws, and a short, pointed tail. Archelon, like other anapsids, had a solidly-roofed skull with no opening (except for eyes, and nostrils).

Archelon’s shell was not like that of modern-day turtles; it did not have the numerous shell bones of modern-day tortoises. Archelon’s back probably had a leathery covering or horny plates over a bony framework on its back.

Diet
Archelon was a carnivore (meat-eater). It had very weak jaws and a toothless beak; it may have eaten jellyfish.

Locomotion
Archelon swam using its paddle-like flippers.

When Archelon lived
Archelon lived during the late Cretaceous period.

Discovery of fossils
Archelon lived in the seas in what is now North America; fossils have been found in Kansas and South Dakota, USA.

Classification
Archelon belonged to the Class Reptilia (reptiles), Order Chelonia (turtles, tortoises and terrapins), Suborder Cryptodira, Family Protostegidae (sea turtles from the late Cretaceous period with flippers and minimal shells), Genus Archelon.

Ancestry
The earliest turtles belonged to the family Proganochelyidae, primitive tortoises that lived during the Triassic period, evolving about 215 million years ago.

Archelon, other turtles (chelonians), and reptiles may have descended from captorhinids, primitive anapsids that lived during the Early Carboniferous period, about 340 million years ago and went extinct at the end of the Triassic period, about 250 million years ago. Captorhinids They had four sprawling legs and a long tail and evolved from amphibians.

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Dinosaur Facts: Ammonite

Ammonites

(pronounced AM-uh-nites) Ammonites were early mollusks.  These marine animals had no vertebrae and were protected by a hard shell (usually coiled) made from calcium.  Fast-moving predators, they ate other animals in the sea.  They were cephalopods.

Anatomy

These animals were protected by a shell (usually spiral-coiled) that contained many air filled chambers, called phragmocones; the animal lived only in the outer chamber.  The opening of the shell is called the aperture.  The walls of each chamber are called septa; these walls were penetrated by a ventral tubelike structure called a siphuncle that probably regulated the air pressure, allowing the ammonite to float.

Size

Ammonites ranged in size from under an inch to about 9 feet (3 m) in diameter.

When Ammonites Lived: Ammonites appeared during the Devonian and went extinct during the K-T extinction, 65 million years ago.  The closest living relative of the ammonite is the chambered nautilus.

Why Are They Called Ammonites?: Ammonites were named for Amun (also spelled Ammon), an ancient Egyptian god who is pictured as having  ram’s horns behind each ear (which look like ammonites).

Fossils

Ammonite fossils are found in great quantities and are used as an index fossil.  Index fossils are commonly found fossils that are limited in time span.  They help in dating other fossils.

Ammonites were common during the Mesozoic Era, but are not found after the Cretaceous period (when they went extinct).  This knowledge (and knowledge of when particular species of ammonites lived) helps date rarer fossils of unknown age.  For example, if a new fossil is found in the same rock layer as an ammonite that is known to have lived only during the Cretaceous period, the new fossil can likely be dated to that same period.

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