Glossary SIG - SZE
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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.
Siltstone
A fine-grained sedimentary rock produced from the consolidation of clay
materials. It has the texture and composition of shale but lacks fine
lamination.
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.
Silurian
The Silurian is a period of geological time between 438 and 408 million
years ago in the Palaeozoic era. It is split into two epochs, the Early
Silurian (438-428 MYA) and the Late Silurian (428-408 MYA).
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. and 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.
SKELETON
A skeleton is the supporting structure of an animal's body. Dinosaur skeltons
were made of bones and cartilage.
SKULL
The skull is the bony structure of the head that encloses the brain and
supports the jaws.
SKULL CREST
Some dinosaurs had skull crests, bony protrusions on their skull. Some
dinosaurs with skull crests include: Parasaurolophus (pictured above),
Dilophosaurus, Corythosaurus, Lambeosaurus, Saurolophus, and many more.
Skull crests may have been used for display or for making sounds.
SMILODON
(pronounced SMILE-oh-don) Smilodon (meaning: "knife tooth"),
the largest saber-toothed cat (or saber-toothed tiger), was a fierce predator
about 4-5 feet (1.2-1.5 m) long. Its one foot (30 cm) long skull had 2
huge canine teeth (they were serrated and oval in cross-section) in powerful
jaws that opened to an angle of about 120°. It also had very strong jaw
and neck muscles that let smilodon stab prey with its deadly teeth. It
had a short, bobbed tail. It may have eaten thick-skinned prey like mastodons
(hairy, extinct elephants) and bison. Thousands of fossils have been found
in late Pleistocene tar pits and rocks from both North America (S. californicus
in California) and South America (S. neogaeus in Argentina). Classification:
family Nimravidae (early cats). Smilodon was named by Plieninger in 1846.
SONORASAURUS
(pronounced son-OR-ah-SAWR-us) Sonorasaurus (meaning: "Sonora lizard")
was a large, plant-eating dinosaur, a brachiosaurid sauropod from the
middle Cretaceous Period, roughly 99-112 million years ago. This giant
was about 45-55 feet (14-17 m) long. This dinosaur had a giraffe-like
stance, a long-neck, a long-tail, a bulky body, and a small head. It was
about 1/3 the size of Brachiosaurus. An incomplete fossil was found in
1995 by geology student Richard Thompson in southern Arizona, USA (in
the Sonora Desert, hence its name). An Acrocanthosaurus tooth was also
found at the site, indicating that it may have eaten Sonorasaurus. The
type species is S. thompsoni. Sonorasaurus was named by Ratkevich in 1998.
Solnhofen Limestone
A fine-grained limestone of Late Jurassic age named after the quarry at
Solnhofen in Bavaria, southern Germany from where it is obtained. The
rock is famous for the excellent preservation of its fossils which often
show traces of soft tissue. The few, very rare fossils of the early bird
Archaeopteryx have all been obtained from the quarries of Solnhofen.
SORDES
(pronounced SOR-dees) Sordes (meaning: "demon") was a pterosaur
with a 1.5 feet (0.5 m) wide wingspan with a thick, hairy coat on the
body (but not on the tail or wings), a long, pointed tail, and no head
crest. From Kazakhstan, Asia, during the late Jurassic Period. It was
not a dinosaur, but a type of extinct, flying reptile. It was named by
Sharov in 1971.
Southern Hemisphere
The half of the globe between the South Pole and the Equator.
SPECIATION
Speciation is the process in which a single species differentiates into
two distinct species. One method by which this occurs is geographic isolation,
in which two subpopulations of a single species are separated and no longer
interbreed. Since the pressures of natural selection differ for the two
groups, the two populations become more and more different from one other.
Species
A group of organisms of common ancestry that are able to reproduce only
among themselves.
SPEED
Paleontologists can deduce approximate dinosaur speeds by using fossilized
trackway and the dinosaur's skeletal structure. In 1976, the British zoologist
R. McNeill Alexander used elephants, birds, people, and many other living
animals to formulate an equation relating an animal's speed, leg length,
and its stride length. Solving for speed, the equation is: Speed (m/sec)=0.25*(stride
length)1.67*(leg length)-1.17*(gravitational constant)0.5
The gravitational constant is 9.8 m/sec2. Leg length is estimated using
Alexander's equations relating hip height to the length of the part of
the foot that hits the ground. This is necessary because it is very difficult
to determine which dinosaur made a set of tracks. (ref: Alexander, R.M.,
1976, Estimates of speeds of dinosaurs, Nature 261: 129-130).
Sphecid Wasp
This antisocial insect lives alone and uses its sting to paralyse its
prey. It digs a nest for its young and brings back food to feed its larvae.
SPHENODOCOELUS
Sphenocoelus was a large, thick-skinned, small-brained, rhinoceros-like
mammal. It was an early brontothere.
Sphenodontian
One of four surviving orders of reptiles although it includes only one
living representative, the tuatara, or Sphenodon, of New Zealand. They
are characterised by possessing two openings in the cheek region of the
skull and an overhanging beak. They arose about the same time as the dinosaurs
and became diverse, but have dwindled to a single form today.
SPHENOPSIDS
Sphenopsids (horsetails) are primitive, spore-bearing plant with rhizomes.
These fast-growing, resilient plants were common during the Mesozoic Era.
The side branches are arranged in rings along the hollow stem. Horsetails
date from the Devonian period 408-360 million years ago, but are still
around today and are invasive weeds. Huge horsetails went extinct in the
Permian mass extinction; smaller ones lived during the Mesozoic Era.
SPINOSAURID
(pronounced SPINE-oh-SAWR-ids) Spinosaurids were a large, theropod from
the Cretaceous Period. These meat-eating dinosaurs had three-fingered
hands and vertebral spines. Other Spinosaurids include Angaturama, Baryonyx,
Irritator, Suchomimus, Siamosaurus and Spinosaurus.
SPINOSAURUS
(pronounced SPINE-oh-SAWR-us) Spinosaurus was a large, sail-backed, spinosaur,
a theropod from the late Cretaceous Period, 97.5 million-95 million years
ago. This meat-eating, bipedal dinosaur was named by Stromer in 1915.
The type species is S. aegypticus.
STAURIKOSAURUS
(pronounced STORE-ee-koh-SAWR-us) Staurikosaurus was a primitive, bipedal
(walked on two legs), meat-eating dinosaur. It was a fast runner that
had long legs (with five-toed feet), a long tail, and a long body. It
had very short arms, a medium-length neck, was about 7 feet (2 m) long,
and weighed roughy 50-100 pounds (20-40 kg). This very early theropod
lived during the late Triassic Period, roughly 231 million to 225 million
years ago. Fossils were found in Brazil and Argentina. Staurikosaurus
was named by Edwin Colbert in 1970. The type species is S. pricei.
STEGOCERAS
(pronounced STEG-oh-CEER-us) Stegoceras (meaning: "roofed horn")
was a bipedal, herbivore, dome-headed, plant-eating dinosaur from the
late Cretaceous Period, about 76-65 million years ago. This pachycephalosuar
was about 7 ft (2 m) long and lived in what is now Alberta, Canada. The
type species is P. validum. Stegoceras was named by paleontologist L.
Lambe in 1902.
STEGOSAURIA
(pronounced STEG-oh-SAWR-ee-ah) Stegosauria was a group (family) of quadrupedal,
plant-eating, ornithischian dinosaurs with two rows of armored plates
along their backs and tail spikes. The stegosaurids lived from the Mid-Jurassic
to the early Cretaceous. Dacentrus, Kentrosaurus,Stegosaurus, and Wuerhosaurus
were stegosaurs.
Stegosaurus
This huge, four-legged herbivore lived in the Late Jurassic period. It
is thought to have inhabited the plains and grazed in large herds alongside
other herbivores like Diplodocus. It had a row of massive bony plates
down its back, and a dangerous tail with four spikes to fend off attack
from predators. It grew up to approximately 12 metres long and seven metres
tall. It could weigh up to seven tonnes.
STEM REPTILE
Stem reptiles (aka Captorhinids or Cotylosaurs) are primitive anapsids
that led to the reptiles (including dinosaurs and turtles), birds, and
mammals. They evolved from amphibians 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. Eggs were laid on the ground, freeing
them from the water. They had four sprawling legs and a tail; they ranged
in size from about a foot long up to 7-8 ft long. Some were predators,
some were herbivores. Class Sauropsida, subclass Anapsida, Infraclass
Captorhinida.
STENONYCHOSAURUS
(pronounced ste-NON-ik-oh-SAWR-us) Stenonychosaurus (meaning: "narrow
claw lizard") is an invalid name for Troödon, a smart, human-sized,
meat-eating theropod dinosaur from the late Cretaceous Period. Stenonychosaurus
was named by C. M. Sternberg in 1932; the type species is S. inequalis
= Troodon formosus.
STENOPTERYGIUS
Stenopterygius was an Ichthyosaur, a dolphin-like reptile about 10 feet
(3 m) long and dolphin-like with large eyes. It was from the early-middle
Jurassic Period in what is now England and Germany. It was not a dinosaur,
but another type of extinct reptile.
STERNBERG, CHARLES H.
A fossil hunter who found many dinosaurs for E.D. Cope, mostly in Alberta,
Canada from 1912-1917. He worked with his sons Charles M., George, and
Levi.
STERNBERG, CHARLES M.
Charles M. Sternberg (son of Charles H. Sternberg), who collected fossils
for E. D. Cope, working mostly in Alberta, Canada from 1912-1917) was
a US fossil hunter who named the following dinosaurs: Brachylophosaurus
(1953), Edmontonia (1928), Macrophalangia (1932), Montanoceratops (1951),
the Pachycephalosaurid family (1945), Pachyrhinosaurus (1950), Parksosaurus
(1937), and Stenonychosaurus (1932).
STERNBERG, GEORGE
George Sternberg (son of Charles H. Sternberg), found a "mummified"
duck-billed dinosaur in Wyoming, USA in 1908.
STERNUM
The sternum is the breastbone. In birds, the keeled sternum anchors some
flight muscles.
Steropodon
A small spiny mammal, from the late Cretaceous period in Australia.
STOKESOSAURUS
(pronounced STOHK-soh-SAWR-us) Stokesosaurus (meaning: "Stokes' lizard")
was a meat-eating dinosaur found in Utah, USA. It was about 13.5 feet
(4 m) long. Stokesosaurus clevelandi, only known from a very incomplete
fossil, dates from the late Jurassic Period, about 156 million to 145
million years ago, although some of its skeletal adaptations resemble
those of dinosaurs from the late Cretaceous Period. Its classification
is unsure; if it was a tyrannosaurid, it was by far the earliest one.
Stokesosaurus was named by Madsen in 1974.
STETHACANTHUS
Stethacanthus (also spelled Stethacanthes) is a genus of strange-looking
extinct sharks from the Carboniferous and Permian periods. They had brush-like
denticles on the head, a large protrusion on the back, fin spines, an
anal fin, and were about 3 feet (1 m) long.
STRATIGRAPHY
Stratigraphy is a method of dating fossils by observing how deeply a fossil
is buried. Sedimentary rock layers (strata) are formed episodically as
Earth is deposited horizontally over time. Newer layers are formed on
top of older layers, pressurizing them into rocks. Paleontologists can
estimate the amount of time that has passed since the stratum containing
the fossil was formed. Generally, deeper rocks and fossils are older than
those found above them.
STRATOCLADISTICS
Stratocladistics is a method of classifying organisms based upon both
cladistics (considering common ancestors with shared anatomical characteristics)
together with stratiography (information from the fossil record which
lets you know which animals lived earlier or later than others; older
fossils are deeper than more recent fossils). In stratocladistics, cladograms
are generated in which ancestors preceed their descendants. (see Science,
11th June, Vol 284, 1999)
STRENUSAURUS
(pronounced STREN-u-SAWR-us) Strenusaurus (meaning: "vigorous lizard")
was an early, plant-eating dinosaur that is now called Riojasaurus. Fossils
were found in Argentina, South America. Struthiosaurus was named in 1870
by paleontologist Bonaparte in 1969. The type species is S. procerus .
STROMER von REICHENBACH, ERNST
Ernst Stromer von Reichenbach (1870-1952) was a paleontologist/geologist
from Munich Germany. He found Egyptian dinosaurs between 1911 and 1914,
in the Bahariya Oasis 180 miles southwest of Cairo. He found and named:
Aegyptosaurus (1932), Bahariasaurus (1934), Carcharodontosaurus (1931),
and Spinosaurus (1915). He also named the family of Spinosaurids (1915).
The original specimens of these 94-million-year-old dinosaurs were destroyed
in the Bayerische Staatssammlung museum when the allies bombed Munich
in 1944 (towards the end of WWII).
STRONG SEASONALITY
Strong seasonality is when there is a big difference in temperature between
the seasons (for example, a hot summer and a cold winter). Compare to
low seasonality, in which the difference in temperatures between the seasons
is small (with mild winters and summers).
STRUTHIOMIMUS
(pronounced STROOTH ee-oh-MEEM-us) Struthiomimus (meaning: "ostrich
mimic") was an ostrich-like carnivorous dinosaur from the late Cretaceous
Period (76 million-70 million years ago). It was about 12 feet (3.7 m)
long and about 6 feet (1.8 m) tall. It had a long neck, small head with
a toothless, horny beak, walked on two strong legs, had long arms, three-fingered
hands with curved claws, three-toed feet, large eyes, large brains, and
a long tail for balancing. It must have been a very fast runner, like
an ostrich. It probably laid eggs and ran in herds. Fossils have been
found in North America (Alberta, Canada and New Jersey, USA). It was first
discovered in 1914 and named by paleontologist Henry F. Osborn in 1916.
STRUTHIOSAURUS
(pronounced STROO-thee-oh-SAWR-us) Struthiosaurus (meaning: "ostrich
lizard") was a small, armored, quadrupedal, plant-eating dinosaur.
Struthiosaurus was about 7 feet (2 m) long) and lived during the very
late Cretaceous Period, about 83 million-65 million years ago. Struthiosaurus
is the smallest-known nodosaurid ankylosaur. This armored ornithischian
had no tail club. Very incomplete fossils have been found in Austria (S.
austriacus) and Romania (S. transilvanicus), where is was isolated on
small islands during the Cretaceous. It may have been the last of the
European nodosauurids. Struthiosaurus was named in 1870 by paleontologist
Bunzel. The type species is S. austriacus.
STYGIMOLOCH
(pronounced STIJ-eh-MOLL-uk) Stygimoloch (meaning: "demon from the
river Styx") was a bipedal, plant-eating dinosaur with very strange,
demonic-looking, spikes and bumps on its skull. The many horns ranged
up to 4 inches (100 mm) long. Stygimoloch was about 7-10 feet (2-3 m)
long and weighed roughly 170 pounds (78 kg). This pachycphalosaurid dinosaur
lived during the very late Cretaceous Period, about 68 million-65 million
years ago. Only parts of Stygimoloch's skull have been found - in Montana
and Wyoming, USA. Stygimoloch belongs to to the family Pachycephalosauridae,
ornithischian dinosaurs that had thick, domed, spiked skulls. Pachycephalosaurs
probably engaged in head-butting as both a defense and as intra-species
rivalry. Stygimoloch was named in 1983 by British paleontologist Peter
M. Galton and German paleontologist Hans-Dieter Sues.
STYGIVENATOR
(pronounced STIJ-eh-veh-NEH-tor) Stygivenator (meaning: "River in
Hell Hunter") was a bipedal, meat-eating dinosaur (a tyrannosaurid
theropod). It may be the same as Aublysodon; it was known as the "Jordan
theropod." Stygivenator was roughly 1.5 feet (4.5 m) long) and lived
during the late Cretaceous Period, about 68 million-65 million years ago.
A partial skull was found in the Hell Creek Formation, Montana, USA. The
type species is S. molnari. Stygivenator was named in 1995 by paleontologist
Olshevsky.
STYRACOSAURUS
(pronounced sty-RACK-oh-SAWR-us) Styracosaurus (meaning: "spike lizard")
was a plant-eating ceratopsian dinosaur that had a horned frill and a
huge nose horn. It was about 18 feet (5 1/4 m) long and weighed about
2-3 tons. It lived during the late Cretaceous Period, roughly 77 million
to 73 million years ago. Fossils have been found in Montana, USA and Alberta,
Canada. Styracosaurus was named by Lambe in 1913. The type species is
S. albertensis.
SUCHOMIMUS
(pronounced SOOK-oh-MIME-us) Suchomimus (meaning: "crocodile mimic")
was a fish-eating spinosaurid theropod dinosaur found in Niger, Africa
in 1997 in the Sahara desert by paleontologist P. Sereno. It was about
36 feet (11 m) long, had powerful hindlegs, small arms, sharp, pointed
teeth, and a crocodile-like pointed jaw. It lived about 100 million years
ago, during the Cretaceous Period.
SUE
Sue is the nickname of a huge, almost complete Tyrannosaurus rex fossil
that was found by Susan (Sue) Hendrickson near Faith, South Dakota, USA,
in August 1990. After much controversy about its ownership (and other
legal matters), Sue (the Tyrannosaurus rex) was auctioned at Sotheby's
in 1997 for 7.6 million dollars to the Field Museum in Chicago, Illinois,
USA, where Sue is now on view.
SUES, HANS-DIETER
Hans-Dieter Sues is a paleontologist at the University of Toronto and
Senior Curator, Department of Palaeobiology, at the Royal Ontario Museum.
Sues studies late Paleozoic and Mesozoic non-mammalian vertebrates. He
named the dinosaurs: Majungatholus (with P. Taquet, 1979), Ornatotholus
(with P. Galton,1983), Saurornitholestes (1978), Stygimoloch (with P.
Galton, 1983), and Zephyrosaurus (1980).
SUESS, EDUARD
Eduard Suess was an Austrian geologist who first realized that there had
once been a land bridge between South America, Africa, India, Australia,
and Antarctica. He named this large land mass Gondwanaland (named after
a district in India where the fossil plant Glossopteris was found). This
was the southern supercontinent formed after Pangaea broke up during the
Jurassic Period. He based his deductions upon the fossil fern Glossopteris,
which is found throughout India, South America, southern Africa, Australia,
and Antarctica.
SUNDANCE SEA
The Sundance Sea was a wide, warm, shallow sea that existed during the
middle to late Jurassic Period, covering much of what is now Montana,
the Dakotas, Wyoming, Utah, Colorado, and Nebraska (USA). This very salty
inland sea formed as the supercontinent of Pangaea was breaking up, and
the Tethys Sea spilled over onto the land. The mid-Jurassic period was
a time when the climate was mild and warm and there was no polar ice,
making sea levels relatively high worldwide.
SUPERCONTINENT
A supercontinent is a large continent that is formed by two or more continents.
Pangaea was a supercontinent consisting of all of Earth's land masses.
It existed during the Permian period through the Jurassic Period. It began
breaking up during the Jurassic, forming the continents Gondwanaland and
Laurasia.
SUPERSAURUS
(pronounced SOUP-er-SAWR-us) Supersaurus is one of the longest dinosaur
yet found, about 140 feet long. This sauropod was a Jurassic long-necked,
long-tailed plant-eater with a small head.
SUUWASSEA
Suuwassea emilieae (Suuwassea is a combination of Crow Indian words meaning
"ancient thunder" and emilieae honors the late Philadelphia
socialite Emilie deHellebrath who funded the expedition) was a small diplodocid
sauropod dinosaur from the Jurassic period, about 150 million years ago.
This plant-eater was about 14-15 m long. It had an extra hole in its skull,
a long neck, a small head, a whip-like tail, and (four) legs like those
of an elephant. Suuwassea was found in 1998 by William Donawick in the
Morrison Formation (specifically in southern Montana near the Wyoming
border). Suuwassea emilieae was named by Jerry Harris and Peter Dodson
in 2004.
Swamp Cypress
It is a type of cypress, a group of ancient plants that survive to this
day.
SYMBIOSIS
Symbiosis is a situation in which two dissimilar organisms live together.
There are many types of symbiosis, including mutualism (in which both
organisms benefit), commensalism (in which one organism benefits and the
other is not affected), or parasitism (in which one organism benefits
at the other organism's expense). Symbiosis used to be defined as a situation
in which two dissimilar organisms live together to the benefit of both
- this is now called mutualism. The word symbiosis means "living
together"" in Greek.
SYMPATRIC SPECIATION
Sympatric speciation is the the formation of a new species within a geographical
area - it is probably caused by strong selection pressures. Compare with
parapatric speciation and allopatry.
SYMPATRY
Sympatry means occupying the same geographical location. Compare with
parapatry and allopatry.
SYMPHYROPHUS
(pronounced sim-FEHR-oh-fus) Symphyrophus (meaning: fused roof) is a doubtful
genus of dinosaur; it is probably Camptosaurus, a plant-eater from the
late Jurassic Period (about 156 million to 145 million years ago) that
looked a lot like Iguanodon. It was a heavy ornithischian dinosaur that
was about 16-23 feet (5-7 m) long. It had a long snout, hundreds of teeth
and a horny beak, and longer legs than arms. It could walk on two or four
legs.
SYMPLESIOMORPHY
Symplesiomorphy (meaning: "shared old form") is the persistence
of ancestral (primitive) traits in different clades.
SYNAPOMORPHY
Synapomorphy (meaning: "shared form") is a derived (new) character
shared by groups. A synapomorphy can be used to infer common ancestry.
SYNAPSID
(pronounced sin-AP-sid) Synapsids are a group of animals distinguished
by having a skull with an extra low opening behind the eyes; this opening
gave these animals stronger jaw muscles and jaws (the jaw muscles were
anchored to the skull opening). Synapsids include the mammals, and extinct
animals such as Dimetrodon. The pelycosaurs were early synapsids; later
synapsids were the therapsids, cynodonts and dicynodonts (from the late
Permian period), leading to the mammals. With time, the synapsid gait
became more upright and tail length decreased. The oldest-known synapsid
is Archarothyris, a pelycosaur 300 million years old.
SYNGONOSAURUS
Syngonosaurus is an invalid name for the dinosaur Anoplosaurus, an iguanodontid
from the early Cretaceous Period, about 98 million years ago. This small
plant-eater had thumb spikes and lived in what is now England.
SYNOPLOTHERIUM
Synoplotherium was a superficially wolf-like mammal that lived during
the Eocene epoch, roughly 50 million years ago. This wolf-sized animal
may have hunted in packs, attacking animals like Hyracotherium (a small
horse), Helaletes (a tapir), and perhaps young or ailing Uintatherium.
This late mesonychid had many sharp canine teeth, huge round-cusped molars,
strong jaws, and a large skull; it was a carnivore that could rip flesh
and crush bones. It had a long tail and long legs. The toes had small
, claw-like hooves (and not claws). Classification: Class Mammalia (mammals),
Superorder Ungulata (ungulates, hoofed mammals), Order Acreodi, Family
Mesonychidae (mammals that may have led to the whales), Genus Synoplotherium.
SYNSACRUM
(pronounced sin-SAK-rum) The synsacrum is the fused part of a bird's vertebral
column (backbone) between the thoracic vertebrae and the caudal vertebrae
(the pelvic region near the base of the tail). The synsacrum is composed
of fused vertebrae, including some thoracic, lumbar, sacral, and caudal
vertebrae. The number of vertebrae in the synsacrum varies from species
to species. The ilium is attached to the synsacrum.
SYNTARSUS
(pronounced sin-TAR-sus) Syntarsus (meaning: "fused or flat ankle")
was a very early saurischian dinosaur from the early Jurassic Period (208
million-194 million years ago). It was a small, bipedal primitive dinosaur,
about 10 feet (3 m) long weighing about 60-70 pounds. It was a carnivore.
It had four-fingered hands and four-toed feet with fused ankle bones (like
those of early ornithopods although it was a saurischian dinosaur). It
was a crested theropod related to Coelophysis. Fossils have found in Africa
and USA. Syntarsus was named in 1969 by M. A. Raath.
SYRMOSAURUS
Syrmosaurus is an invalid name for the dinosaur Pinacosaurus.
SZECHUANOSAURUS
(pronounced SECH-ou-WAN-nuh-SAWR-us) Szechuanosaurus (meaning: "Szechuan
province lizard") was a meat-eating dinosaur from the late Jurassic
Period, about 156-145 million years ago. This Allosaurid theropod was
about 20 feet (6 m) long, had short arms with clawed, three-fingered hands,
long, powerful legs, a short neck, and a big head with pointed, curved
teeth. It ma have weighed 220-330 pounds (100-150 kg). Fossils were found
in Sichuan Province, China. Szechuanosaurus was named by paleontologist
Young in 1942. The type species is S. campi. Szechuanosaurus is a doubtful
genus; very little is known about it.