ZoomDinosaurs.com Dinosaur and Paleontology Dictionary

SIAMOSAURUS (pronounced si-AM-oh-SAWR-us) Siamosaurus (meaning "Siamese lizard") was a large, sail-backed, early spinosaurid theropod from the early Cretaceous period. This meat-eating biped was named by paleontologists Buffetaut and Ingavat in 1986 and found in Thailand. The type species is S. suteethorni.

SIAMOTYRANNUS (pronounced sie-AM-oh-ti-RAN-us) Siamotyrannus (meaning "Siamese tyrant") was a tyrannosaurid theropod from the early Cretaceous period. Fossils were found in northeast Thailand. This meat-eating biped was named by paleontologists Buffetaut, Suteethorn, and Tong in 1996.

SICKLE-LIKE CLAW Some theropod dinosaurs, including the dromaeosaurids (eg., Velociraptor, Utahraptor, and Deinonychus) and Megaraptor were armed with a sickle-like claw on each hind foot, making them deadly predators. These sharp claws, varying in length from a few inches to over 14 inches (35 m), could eviscerate prey easily. When alive, this claw would have been sheathed in a horny, keratinous material much like our fingernails, making the claw even bigger, longer and sharper.

SIGNOR-LIPPS EFFECT The Signor-Lipps Effect explains how a fossil record that appears to be a gradual extinction can actually represent a sudden extinction. If many organisms go extinct at the same time, the fossil record wouldn't necessarily represent the rarer species and the more common equally. The rarer species might disappear from the fossil record long before the time of extinction, simply due to chance.

SILUOSAURUS (pronounced suh-LOO-oh-SAWR-us) Siluosaurus (meaning "Silk Road lizard") was a hypsilophodontid ornithopod from the early Cretaceous period. Siluosaurus is known from only two teeth that were found along the ancient Silk Road in China. This plant-eater was named by paleontologist Dong in 1996. THe type species is S. zhangqiani.

SILURUAN PERIOD (pronounced si-LURE-ee-en) The Silurian Period lasted from 438 million to 408 million years ago. The first jawed fishes and uniramians (like insects, centipedes and millipedes) appeared during the Silurian (over 400 million years ago). The first vascular plants (plants with water-conducting tissue as compared with non-vascular plants like mosses) appeared on land (Cooksonia is the first known vascular plant). During this time, there were high seas worldwide until the end of the Silurian. Brachiopods, crinoids, corals, and eurypterids (sea scorpions) lived in the seas. The Silurian was named for the Silures, an ancient Celtic tribe that lived in southeastern Wales in ancient times.

SILVISAURUS (pronounced SILL-vah-SAWR-us) Silvisaurus (meaning "forest lizard") was a primitive, armored dinosaur with no tail clubs. It was about 13 feet (4 m) long and had a long neck (relative to its relatives, the ankylosaurs). It had balloon-like sinuses (cavities within its head) that may have amplified sounds, letting Silvisaurus make loud, reverberating noises. This quadrupedal plant-eater dates from the early Cretaceous period, about 116 million to 113 million years ago. This nodosaurid ankylosaur was named by paleontologist Eaton in 1960 from a partial skeleton found in Kansas, USA.

SINORNITHOIDES Sinornithoides (meaning "Chinese bird form") was a troodontid dinosaur found in Inner Mongolia, Asia. Sinornithosaurus lived during the middle Cretaceous period, roughly 110 to 100 million years ago. The type species is S. youngi. Sinornithosaurus was named by D. A. Russell and Dong Zhiming in 1994.

SINORNITHOSAURUS Sinornithosaurus millenii (meaning "Chinese bird lizard of the millennium") was a dromaeosaurid dinosaur recently found in northeast China. This fossil had traces of downy fibers on its skin. Sinornithosaurus lived during the middle Jurassic period, roughly 124 million years ago. Sinornithosaurus was named by Wu, et. al, in 1999.

SINOSAUROPTERYX (pronounced SINE-oh-sawr-OP-ter-iks) Sinosauropteryx (meaning "Chinese lizard with feathers") was a feathered theropod dinosaur from the late Jurassic period. It was about 3.3 feet (1 m) long. Fossils (including 2 complete adult skeletons, one juvenile skeleton, and tissue impressions) have been found in China. It was named by Ji Q. & Ji S. in 1996.

SINRAPTOR (pronounced SINE-rap-tor) Sinraptor (meaning "Chinese plunderer") was a large theropod dinosaur from the late Jurassic period, roughly 155-144 million years ago. This carnosaur was about 23 feet (7 m) long. A meat-eater, it walked on two powerful legs, had short arms, a long snout, and sharp teeth. Fossils (including a nearly complete skeleton) were found near Jiangjunmiao, in N.W. China. Sinraptor was named by Phillip Currie and Zhao, 1994. The type species is S. dongi.

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