Sigilmassasaurus
Encyclopedia
Sigilmassasaurus is a genus
of tetanuran
theropod dinosaur
from the middle of the Cretaceous Period of northern Africa
. Not much is known about this dinosaur, but it was almost definitely a biped
al carnivore
like most other theropods.
Fossil
s of this dinosaur were found in the Tafilalt
Oasis
region of Morocco
, near the site of the ancient city of Sijilmassa, for which it was named. Canadian
paleontologist Dale Russell
named Sigilmassasaurus in 1996, from the ancient city and the Greek
word sauros ("lizard"). A single species
was named, S. brevicollis, which is derived from the Latin
brevis ("short") and collum ("neck"), because the neck vertebrae are very short from front to back. Russell also described another specimen as a possible second species of Sigilmassasaurus, although he chose not to name it due to its incomplete nature.
Sigilmassasaurus comes from sediments in southern Morocco, which are called by various names, including the Grés rouges infracénomaniens, Continental Red Beds, and lower Kem Kem Beds. These rocks date back to the Cenomanian
, the earliest faunal stage
within the Late Cretaceous
Period, or about 100 to 94 million years ago (Sereno et al., 1996).
, or original specimen, of S. brevicollis is a single neck
vertebra, although Russell referred about fifteen other vertebra found in the same formation to the species. Other material was found in Egypt
, and is known as "Spinosaurus B" (Stromer, 1934). Russell considered this Egyptian specimen to belong to Sigilmassasaurus or a closely related animal, and created the family Sigilmassasauridae for these animals (Russell, 1996). The neck vertebrae of these dinosaurs are wider from side to side than they are long from front to back. The exact position of Sigilmassasaurus within the theropod family tree is unknown, but it belongs somewhere inside the theropod subgroup known as Tetanurae
.
Some scientists do not believe that Sigilmassasaurus is a valid genus. In 1996, Paul Sereno
and colleagues described a Carcharodontosaurus
skull
(SGM-Din-1) from Morocco, as well as a neck vertebra (SGM-Din-3) which resembled that of "Spinosaurus
B," which they therefore synonymized with Carcharodontosaurus (Sereno et al., 1996). A later study went further, calling Sigilmassasaurus itself a junior synonym of Carcharodontosaurus (Sereno et al., 1998).
More recently, however, it was revealed that SGM-Din-3, which was used to synonymize Carcharodontosaurus and "Spinosaurus B" was not actually associated with SGM-Din-1, the Carcharodontosaurus skull described in 1996, and shows clear differences with the holotype of Carcharodontosaurus. Other features of "Spinosaurus B" also clearly differ from Carcharodontosaurus, lending support to the notion that it (and therefore Sigilmassasaurus) is a separate taxon (Novas et al., 2005).
) are known from the Cenomanian of northern Africa, raising questions about how such animals would have coexisted. Species of Spinosaurus
, the largest known theropod, has been found in both Morocco and Egypt, as has the huge Carcharodontosaurus. Two smaller theropods, Deltadromeus
and Bahariasaurus
, have also been found in Morocco and Egypt, respectively, and may be closely related or possibly the same genus. Sigilmassasaurus, from Morocco, and "Spinosaurus B", from Egypt, represent a fourth type of large predator
. This situation resembles that in the Late Jurassic
Morrison Formation
of North America
, which boasts up to five theropod genera over one tonne in weight, as well as several smaller genera (Henderson, 1998; Holtz et al., 2004). Differences in head shape and body size among the large North African theropods may have been enough to allow niche
partitioning as seen among the many different predator species found today in the Africa
n savanna
(Farlow & Pianka, 2002).
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of tetanuran
Tetanurae
Tetanurae, or "stiff tails", is a clade that includes most theropod dinosaurs, as well as birds. Tetanurans first appear during the early or middle Jurassic Period.-Definition:...
theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the middle of the Cretaceous Period of northern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. Not much is known about this dinosaur, but it was almost definitely a biped
Biped
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
al carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
like most other theropods.
Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s of this dinosaur were found in the Tafilalt
Tafilalt
Tafilalt or Tafilet is a region and the most important oasis of the Moroccan Sahara; it is also considered one of the largest oases in the world, the oasis is entirely located along the Ziz River. The oasis is ten days' journey south of Fez, across the Atlas Mountains...
Oasis
Oasis
In geography, an oasis or cienega is an isolated area of vegetation in a desert, typically surrounding a spring or similar water source...
region of Morocco
Morocco
Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
, near the site of the ancient city of Sijilmassa, for which it was named. Canadian
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
paleontologist Dale Russell
Dale Russell
Dale A. Russell is a Canadian geologist/palaeontologist, currently Research Professor at The Department of Marine Earth and Atmospheric Sciences of North Carolina State University...
named Sigilmassasaurus in 1996, from the ancient city and the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word sauros ("lizard"). A single species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
was named, S. brevicollis, which is derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
brevis ("short") and collum ("neck"), because the neck vertebrae are very short from front to back. Russell also described another specimen as a possible second species of Sigilmassasaurus, although he chose not to name it due to its incomplete nature.
Sigilmassasaurus comes from sediments in southern Morocco, which are called by various names, including the Grés rouges infracénomaniens, Continental Red Beds, and lower Kem Kem Beds. These rocks date back to the Cenomanian
Cenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
, the earliest faunal stage
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
within the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
Period, or about 100 to 94 million years ago (Sereno et al., 1996).
Disputed validity
The holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
, or original specimen, of S. brevicollis is a single neck
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...
vertebra, although Russell referred about fifteen other vertebra found in the same formation to the species. Other material was found in Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, and is known as "Spinosaurus B" (Stromer, 1934). Russell considered this Egyptian specimen to belong to Sigilmassasaurus or a closely related animal, and created the family Sigilmassasauridae for these animals (Russell, 1996). The neck vertebrae of these dinosaurs are wider from side to side than they are long from front to back. The exact position of Sigilmassasaurus within the theropod family tree is unknown, but it belongs somewhere inside the theropod subgroup known as Tetanurae
Tetanurae
Tetanurae, or "stiff tails", is a clade that includes most theropod dinosaurs, as well as birds. Tetanurans first appear during the early or middle Jurassic Period.-Definition:...
.
Some scientists do not believe that Sigilmassasaurus is a valid genus. In 1996, Paul Sereno
Paul Sereno
Paul Callistus Sereno is an American paleontologist from the University of Chicago who discovered several new dinosaur species on several continents. He has conducted excavations at sites as varied as Inner Mongolia, Argentina, Morocco, and Niger...
and colleagues described a Carcharodontosaurus
Carcharodontosaurus
Carcharodontosaurus was a gigantic carnivorous carcharodontosaurid dinosaur that lived around 100 to 93 million years ago, during the late Albian to early Cenomanian stages of the mid-Cretaceous Period...
skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
(SGM-Din-1) from Morocco, as well as a neck vertebra (SGM-Din-3) which resembled that of "Spinosaurus
Spinosaurus
Spinosaurus is a genus of theropod dinosaur which lived in what is now North Africa, from the lower Albian to lower Cenomanian stages of the Cretaceous period, about 112 to 97 million years ago. This genus was first known from Egyptian remains discovered in 1912 and described by German...
B," which they therefore synonymized with Carcharodontosaurus (Sereno et al., 1996). A later study went further, calling Sigilmassasaurus itself a junior synonym of Carcharodontosaurus (Sereno et al., 1998).
More recently, however, it was revealed that SGM-Din-3, which was used to synonymize Carcharodontosaurus and "Spinosaurus B" was not actually associated with SGM-Din-1, the Carcharodontosaurus skull described in 1996, and shows clear differences with the holotype of Carcharodontosaurus. Other features of "Spinosaurus B" also clearly differ from Carcharodontosaurus, lending support to the notion that it (and therefore Sigilmassasaurus) is a separate taxon (Novas et al., 2005).
Paleobiology
Several large theropods (more than one tonneTonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
) are known from the Cenomanian of northern Africa, raising questions about how such animals would have coexisted. Species of Spinosaurus
Spinosaurus
Spinosaurus is a genus of theropod dinosaur which lived in what is now North Africa, from the lower Albian to lower Cenomanian stages of the Cretaceous period, about 112 to 97 million years ago. This genus was first known from Egyptian remains discovered in 1912 and described by German...
, the largest known theropod, has been found in both Morocco and Egypt, as has the huge Carcharodontosaurus. Two smaller theropods, Deltadromeus
Deltadromeus
Deltadromeus is a genus of large basal ceratosaurian theropod dinosaur from Northern Africa. It had long, unusually slender hind limbs for its size, suggesting that it was a swift runner. The skull is not known. Two fossil specimens of a single species Deltadromeus (meaning "delta runner") is a...
and Bahariasaurus
Bahariasaurus
Bahariasaurus is a genus of large theropod dinosaur found in the Bahariya Formation in El-Waha el-Bahariya or Bahariya oasis in Egypt and Kem Kem Beds of North Africa, which date to the late Cretaceous Period, , about 95 million years ago...
, have also been found in Morocco and Egypt, respectively, and may be closely related or possibly the same genus. Sigilmassasaurus, from Morocco, and "Spinosaurus B", from Egypt, represent a fourth type of large predator
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
. This situation resembles that in the Late Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, which boasts up to five theropod genera over one tonne in weight, as well as several smaller genera (Henderson, 1998; Holtz et al., 2004). Differences in head shape and body size among the large North African theropods may have been enough to allow niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
partitioning as seen among the many different predator species found today in the Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
n savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
(Farlow & Pianka, 2002).