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Types of Spinosaurus

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Spinosaurus Introduction - Origins and Types of Spinosaurids

Introduction:

The Spinosaurids 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.

Distribution:

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, it appears Spinosaurids migrated to each of these continents and had 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, such as a partial skeleton found in the Khok Kruat formation of Thailand (Buffetaut et al, 2005).

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The Two Spinosaurid Clades: Baryonchinae and Spinosaurinae

All Spinosaurids are characterized by their elongated, crocodile like skull, peg-like teeth, and a robust forelimb with a sickle shaped thumb claw. They were well adapted for grasping and eating fish. Spinosaurids can be broken into two clades, Baryonchinae, and Spinosaurinae (Sereno 1998).

Baryonchinae clade

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 finely serrated teeth. The dorsal vertebrae are deeply keeled (Sereno 1998) - This means they had a small hump or sail on their lower backs.

Spinosaurinae clade

This clade contains Irritator, Spinosaurus, and Oxalaia. These Spinosaurids have straight, unserrated teeth which are spaced farther apart. They Spinosaurids also have a small nasal cavity that is located farther back in the skull (making it easier to breathe when partly submerged). The Spinosaurus genus also has a remarkably tall spinal processes on it's upper back (a sail).

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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. Like all Spinosaurids, Suchomimus also has a large thumb claw. The teeth are recurved and finely serrated (Sereno 1998).

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Baryonyx walkeri ("Heavy Claw") - Europe

First discovered in 1983, Baryonyx walker is very similar to Suchomimus, as it has a similar skull, 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.

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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 it 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).

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Irritator challengeri ("Irritated Challenge") - South America - Brazil

The name Irritator Challenge comes from the fact the mostly complete skull that was used to name the specimen had been partially faked by a commercial dealer. It was an irritating challenge for David Martill and the other paleontologists to remove car body filler and fake parts of the skull in order to study it!

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. 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 pterosaur from the same formation was found to have a spinosaurid tooth embedded in it. pterosaur would have been in or near the water feeding on fish.

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Oxalaia quilombensis ("Oxalaia of the quilombo settlements") - South America - Brazil

Oxalaia is named after an African deity that was introduced to Brazil during the time of slavery. It 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.

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Spinosaurus aegyptiacus ("Spine Lizard of Egypt") - 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 a partial specimen and also a juvenile tail was described by Ibrahim et al. (2014 and 2020) Ibrahim also did an analysis on available Spinosaurus bones and discovered remarkable water adaptations of the dinosaur.
Click on this link for your guide to Spinosaurus: Spinosaurus aegyptiacus Facts.

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References / Works Cited