Spinosaurus Introduction - Origins and Types of Spinosaurids
The Spinosaurids probably first appeared in the middle Jurassic and reach their peak in the mid-late Cretaceous.
They may have stemmed from the Tetanurae clade of dinosaurs (Sereno el at 1998), which is a diverse group of
carnivorous theropods that appear in the early the Jurassic.
The fossil record of Spinosaurids is very fragmentary. As a result, many "genera" and "species" have been assigned
based on fragments. However, as more samples are found, many of these turn out to be synonymous with other species
of spinosaurids. After sifting through the literature, there appear to be at least 6 agreed upon types (genera)
of Spinosaurids, and probably many more as research is conducted and new fossils are found.
Remarkably, they appear to have a wide diversity and a global distribution. In the middle Jurassic,
the continents of South America, Africa, Antarctica, India, and Australia were still connected. Europe was
an island chain off of North Africa. So, Spinosaurids could have easily migrated to each of these continents.
As a result, Spinosaurids appear to have a nearly global distribution.
They are found in South America, Europe, and North Africa. Fragmentary remains have also been found in Australia
and Asia. In Australia a single cervical vertebra has been found in that may be from some type of Spinosaurus (Barrett et al, 2011).
Throughout Asia there have been reports of fragmentary Spinosaurid fossils. For example, in Thailand a partial skeleton
found in the Khok Kruat formation looks similar to a type of Spinosaurid (Buffetaut et al, 2005).
The Two Spinosaurid Clades: Baryonchinae and Spinosaurinae
All Spinosaurids are characterized by their elongated, crocodile like skull, peg-like teeth,
and a robust forelimb and sickle shaped thumb claw. They were all well adapted for grasping and eating fish.
However, Spinosaurids can be broken into two clades, Baryonchinae, and Spinosaurinae (Sereno 1998).
This clade contains the closely related Suchomimus and Baryonyx genus, as well as the more basal Ichthyovenator genus.
These Spinosaurids have an increased number of teeth that are finely
serrated. The dorsal vertebrae are deeply keeled (Sereno 1998) - This means
they had a small hump or sail on their lower backs.
This clade contains Irritator, Spinosaurus, and Oxalaia.
These Spinosaurids have straight, unserrated teeth which are spaced further apart.
They Spinosaurids also have a small nasal cavity that is located further back in the skull
(making it easier to breathe when partly submerged). At least one genus in this clade has remarkably
tall spinal processes on it's upper back.
Suchomimus tenerensis (Crocodile mimic) - North Africa
Suchomimus tenerensis is an Early Cretaceous dinosaur. It was found in 1997 in the Elrhaz Formation of Niger, Africa.
This Spinosaurid has a very long and extremely narrow skull (Sereno 1998). Its jaws are similar in shape to
a gavial fish-eating crocodile, which is known for its extremely narrow jaws. Like all Spinosaurids,
Suchomimus also has a large thumb claw. The teeth are recurved and are finely serrated (Sereno 1998).
Suchomimus skull - Notice the very thin snout.
Image by: AStrangerintheAlps Copyright: C.C. BY 3
Baryonyx walkeri ("Heavy Claw") - Europe
First discovered in 1983, Baryonyx walker is very similar to Suchomimus,
as it has a similar skull, has numerous teeth with fine serrations, and has a large thumb claw.
It is one of the earlier Spinosaurids found. It comes from Early Cretaceous formations in Europe that
date to around 130 million years ago. The 1983 specimen found
in England had scales and bones from fish in its body cavity,
further showing these dinosaurs were fish eaters. Another Spinosaurid,
called Suchosaurus, from Europe is synonymous with Baryonyx.
Suchomimus skull - Notice the very thin snout.
Image by: Unhindered by Talent Copyright: C.C. BY 2.0
Ichthyovenator laosensis ("Fish Hunter") - Laos - Southeast Asia
A partial skeleton (no skull) was discovered in an Early Cretaceous formation called the Gres Superieurs Formation in Laos.
The partial skeleton follows the Spinosaurus design. A unique characteristic of Ichthyovenator is itt has high neural spines on the middle back,
and then again on the upper back, indicating it may have had two sails on its back (Allain et al, 2012).
This is figure 3 from Allain eta l, 2012. It shows the sacral vertebra, showing the second 'sail' on its lower back.
Image from: Allain, et al. 2012 - Supplimentary Material
Irritator challengeri ("Irritated") - South America - Brazil
Irritator is a Mid-Cretaceous Spinosaurid from Brazil. A partial skull was found in the Santana Formation by
illegal fossil poachers. The poachers fabricated the missing parts of the skull. In 1996, paleontologists Martill et al. acquired the skull.
The paleontologists went to great lengths to remove the fabricated portions of the skull and named it "Irritator" after
being extremely irritated at having to remove the modifications.
Since then, part of a spinal column has been found.
Irritator has a very similar skull as Spinosaurus. It has unserrated teeth ideal for grasping fish.
Its nostrils are positioned far back on the skull, allowing it to breathe while almost completely submerged.
Irritator probably looked very similar to Spinosaurus.
A petrosour from the same formation was found to have a spinosaurid tooth embedded in it. Petrosours would have been near the water feeding on
fish. So it appears these creatures were opportunistic and did not solely feed on fish.
This is an Angaturama on display at the National Museum in rio de Janeiro. Angaturama may be synonymous with Irritator.
Notice the petrasour in it's mouth. A fossil pertrasour from the formation was found with an Angaturama (Irritator) tooth embedded in it.
Image by: Celso Abreu Copyright: C.C. BY 2.0
Oxalaia quilombensis - South America - Brazil
Oxalaia, named after an African deity, is a large Spinosaurid from Brazil.
It is only known from a skull and jaw fragment described by Kellner et al in 2011.
Based on the fragments, the skull would have been over 4 feet in length. The fragments
have a different shape than Irritator, but still resemble Spinosaurus.
This is the skill section of Oxalaia.
Image by: Nekarius (Own Work) via wikimedia commons Copyright: C.C. BY 3.0
Spinosaurus aegyptiacus ("Spine Lizard") - North Africa
Spinosaurus aegyptiacus is by far the most well known spinosaurus. It was a main dinosaur in the Jurassic park movies,
and recently made headlines when an associated specimen was found in Morocco. Fossils of the spinal column, teeth, and skull were
first discovered by Markgraf in 1912 and described by Stromer in 1915. Unfortuantely, the specimens were destroyed in WWII. More recently,
in 2014, a partial specimen was described by Ibrahim et al, Ibrahim et al also did an analysis on available Spinosaurus
bones and discovered remarkable water adaptations of the dinosaur. Click on this link for more Information on
This is a mount of Spinosaurus aegyptiacus in its new aquatic posture. This dinosaur probably could not stand on two legs and spent most of its time in the water.
This mount is at the National Geographic Museum in Washington, D.C.
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|References and Works Cited:|
Allain, R.; Xaisanavong, T.; Richir, P.; Khentavong, B. (2012).
"The first definitive Asian spinosaurid (Dinosauria: Theropoda) from the early cretaceous of Laos".Naturwissenschaften 99 (5): 369-377. 99 (5)
Barrett, P.M., Benson, R.B.J, Rich, T.H., and Vickers-Rich, P. (2011).
"First spinosaurid dinosaur from Australia and the cosmopolitanism of Cretaceous dinosaur faunas."
Biology Letters online preprint: doi:10.1098/rsbl.2011.0466
Buffetaut, E. and M. Ouaja. 2002. "A new specimen of Spinosaurus (Dinosauria, Theropoda) from the Lower Cretaceous of Tunisia
, with remarks on the evolutionary history of the Spinosauridae." Bulletin de la Societe Geologique de France 173/5:415-421.
Ibrahim, N., Sereno, P. C., Dal Sasso, C., Maganuco, S., Fabbri, M., Martill, D. M., Zouhri, S., Myhrvold, N., Iurino, D. A. (2014).
"Semiaquatic adaptations in a giant predatory dinosaur". Science. PDF file
Kellner, A.; Azevedo, S.; Machado, A.; De Carvalho, L.; Henriques, D. (2011). "A new dinosaur (Theropoda, Spinosauridae)
from the Cretaceous (Cenomanian) Alcantara Formation, Cajual Island, Brazil" Anais da Academia Brasileira de Ciencias, 83 (1), 99-108
Martill, D. M., Cruickshank, A. R. I., Frey, E., Small, P. G., Clarke, M. (1996).
"A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil". Journal of the Geological Society 153: 5.
Paul C. Sereno, Allison L. Beck, Didier B. Dutheil,
Boubacar Gado, Hans C. E. Larsson, Gabrielle H. Lyon,
Jonathan D. Marcot, Oliver W. M. Rauhut, Rudyard W. Sadleir,
Christian A. Sidor, David D. Varricchio, Gregory P. Wilson,
Jeffrey A. Wilson (1998) "A Long-Snouted Predatory Dinosaur from Africa and the Evolution of Spinosaurids" Science 282, 1298;
Taquet, P., and Russell, D.A. (1998). "New data on spinosaurid dinosaurs from the Early Cretaceous of the Sahara".
Comptes Rendus de l'Academie des Sciences - Series IIA - Earth & Planetary Sciences 327 (5): 347-353.