Metoposaurus algarvensis – Triassic Predator the Size of a Door

Portugal may have earned a deserved reputation for being the Jurassic dinosaur fossil capital of Europe, but more ancient sediments provide equally fascinating insights into life on our planet just as the Dinosauria were beginning to diversify and dominate terrestrial ecosystems.  Step forward (or more appropriately waddle forward), Metoposaurus algarvensis a new species added to the Metoposaurus genus described from a bone bed found in the Algarve region of southern Portugal.

A team of international scientists which include Dr Steve Brusatte (University of Edinburgh) and J. Sébastien Steyer (Centre de Recherches en Paléobiodiversité et Paléoenvironnements, Paris), Dr Richard Butler (Birmingham University) and Professor Octávio Mateus (Museu da Lourinhã, Portugal) have been studying the fossilised remains of several individuals that apparently died together when their lake dried up.

A Pair of Super-sized Amphibians Await Their Fate as the Lake Dries Up

Two-metre-long amphibious predator.

Picture credit: Joana Bruno

Metoposaurid Fossils

Metoposaurid fossils are known from Europe, Africa, North America and India, although this is the first time fossils relating to this genus have been discovered in the Iberian peninsula.  Some of the fossil specimens indicate that these amphibians reached lengths in excess of two metres and the shape of the skull along with other anatomical differences between the Portuguese fossils and other material known from Poland and Germany has permitted a new species to be erected.

The bonebed that contains the remains of numerous individuals, ten skulls have been excavated so far, was discovered more than thirty years ago, but not properly mapped and explored until 2009 when the dig site was relocated.  Although, these predators superficially resemble a modern salamander, scientists debate whether the Order Temnospondyli which the metoposaurids are part of, are actually closely related to extant amphibians.

The Scientists at Work Excavating the Bone Bed

Scientists carefully extract blocks containing fossil material.

Picture credit: Steve Brusatte/Richard Butler/ Octávio Mateus/J. Sébastien Steyer

Metoposaurus algarvensis

Although the mouth was large and lined with many sharp teeth, the thick-set body was supported by relatively weak limbs.  It is very likely that M. algarvensis spent a great deal of time in water, the fossils of these large amphibians are associated with strata laid down in lake or river environments (lacustrine and fluvial environments).

These animals were probably ambush predators catching fish with rapid movements of their large mouths from side to side.  They may also have ambushed unsuspecting small creatures, even some small early dinosaurs as these animals came down to the waters edge to drink.  They would have been very capable swimmers but the small legs would have made movement on land rather clumsy and awkward.

Three European species of Metoposaurus have now been described (M. diagnosticus from Germany,  M. krasiejowensis from Poland and M. algarvensis from Portugal).  Some of the German fossil specimens indicate amphibians approaching 3 metres in length, however, the majority of the temnospondyls became extinct by the end of the Triassic.  The Portuguese bone bed evidence further supports the theory that these large animals were confined to very wet habitats with lots of freshwater and therefore the sort of areas that these creatures could live in was much more restricted when compared to the rapidly evolving reptiles such as the crocodiles and the Dinosauria.

The Temnospondyls

As an Order, the temnospondyls probably evolved sometime in the Early Carboniferous and their fossils represent some of the most widely distributed terrestrial fossils recorded in Permian/Triassic strata.  Their global range seems to have been limited to low latitudes during the Middle to Late Triassic, a distribution similar to but not identical to the phytosaurs (crocodile-like reptiles that most probably become extinct at the end of the Triassic).

Phytosaurs are archosauriforms and provide plenty of evidence that the long-snouted, fish grabbing, swimming predator form has evolved in lots of different types of animal over the course of the history of our planet.  Their more primitive ankle configuration (when compared to extant crocodiles), did not prevent the phytosaurs from evolving into a myriad of different forms.

One Survivor into the Cretaceous

However, apart from some controversial fossils, which most scientists claim are Late Triassic and not Early Jurassic the phytosaurs along with most of the temnospondyls were extinct by around 200 million years ago.  However, viewers of the seminal television series “Walking with Dinosaurs” will remember that in programme five “Spirits of the Silent Forest”, which focused on life in the southern polar regions around 106 million years ago, a Koolasuchus makes an appearance.    Two fossil jaws found in Victoria, Australia suggest that at least one type of temnospondyl survived into the Cretaceous.

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Carnufex carolinensis – Three Metre Long Crocodylomorph Challenged Early Theropod Dinosaurs

Palaeontologists from North Carolina State University and the North Carolina Museum of Natural Sciences have published a paper in the open access journal “Scientific Reports” about their research into one of the most fearsome predators that roamed the Americas during the early stages of the Late Triassic some 231 million years ago.  The reptile, identified as an ancestral crocodile has been named Carnufex carolinensis and it probably occupied an apex predator position in the lush, humid, tropical ecosystem as represented by the strata of the Pekin Formation found in North Carolina.

An Illustration of the Fearsome Crocodylomorph C. carolinensis

Fearsome predator of the Triassic.

Picture credit: Jorge Gonzales

 The fossilised remains were found in Chatham County. They include a fifty-centimetre-long partial skull, which when digitally mapped and reconstructed in three dimensions provided the scientists with a very accurate picture of the skull of this carnivore.  It may have walked on four legs for some of the time, but it would also have been able to rear up onto its powerful hind legs, perhaps to help it run down prey.  C. carolinensis was very probably a facultative biped.

Commenting on the significance of the study, Assistant Research Professor at North Caroline State University, Lindsay Zanno said:

“Fossils from this time period are extremely important to scientists because they record the earliest appearance of crocodylomorphs and theropod dinosaurs, two groups that first evolved in the Triassic Period, yet managed to survive to the present day in the form of crocodiles and birds.  The discovery of Carnufex, one of the world’s earliest and largest crocodylomorphs, adds new information to the push and pull of terrestrial top predators across Pangea.”

Rapid Evolution

After the end Permian extinction that wiped out a lot of terrestrial animals there seems to have been a period of rapid evolution as new animal types evolved to exploit the vacant positions in ecosystems.  The fossil record from the Early and Middle Triassic indicates that land-living predator diversity attained new levels with a seeming overabundance of carnivorous animals due to the evolution of entirely new types of predator.  One of the most significant clades to evolve was the Crocodylomorpha that still survive today.  The crocodiles represent one of only two archosaurian lineages that are extant.

The second lineage are the Aves (birds).  In contrast to their modern-day descendants, the earliest crocodylomorphs were generally small, cursorial animals occupying a subsidiary role to other types of predator.  However, C. carolinensis represents a large-bodied taxon with a slender skull, lined with sharp teeth.  It was clearly a formidable hunter and these fossils from Chatham County represent the remains of one of the oldest and earliest diverging crocodylomorphs described so far.

Roaming Pangea at the time were large terrestrial predators which formed the rauisuchians group, amongst the rauisuchids there was a sub-group of poposauroids which were also mainly predatory.  In the southern part of the super-continent, these types of ancient crocodile-like creatures competed with the rapidly evolving theropod dinosaurs.  The fossils of Carnufex also suggest that in the northern part of Pangea, large-bodied crocodylomorphs, not dinosaurs were making up a large portion of the apex terrestrial predators.

Lindsay Zanno went onto add:

“These animals hunted alongside the earliest theropod dinosaurs, creating a predator pile-up.  We knew that there were too many top performers on the proverbial stage in the Late Triassic.  Yet, until we deciphered the story behind Carnufex, it wasn’t clear that early crocodile ancestors were among those vying for top predator roles prior to the reign of the dinosaurs in North America.”

Although the skull material was fragmentary, the scientists were able to build up a picture of the features of Carnufex using comparisons with better known crocodylomorphs from the fossil record.  Sophisticated computer modelling helped the scientists to piece together the skull of this ancient crocodile.

A 231-Million-Year-Old Jigsaw Puzzle

Piecing together the skull from the fragmentary bones.

Picture credit: North Caroline State University

The picture above shows the various bones associated with the fossil specimen (blue), these have been superimposed on a model of a skull (white parts relate to fossil material, grey pieces are based on related animals from the fossil record).

As the Triassic period came to an end there was another set of extinctions, although nowhere near as dramatic as the End Permian extinction.  Many of these large, apex predators did not survive into the Jurassic, only the small-bodied crocodylomorphs and the Theropoda survived.

Lindsay Zanno stated:

“Theropods were ready understudies for vacant top predator niches when large-bodied crocs and their relatives bowed out.  Predatory dinosaurs went on to fill these roles exclusively for the next 135 million years or so.”

However, for the ancestors of today’s crocodiles, gharials, caimans and alligators there were plenty of other ecological niches for them to exploit.  As the theropods began to get bigger and bigger, these early crocodiles continued to flourish but this time they occupied secondary predatory roles.

Graduate student Susan Drymala of North Carolina State University and a co-author of the study put it rather nicely when she explained:

“The ancestors of modern crocs initially took on a role similar to foxes and jackals, with small, sleek bodies and long limbs.  If you want to picture these animals, just think of a modern fox, but with alligator skin instead of fur.”

Perhaps the most famous member of the Order Rauisuchia is Postosuchus, fossils of this six-metre-long giant have been found in North Carolina.  However, it appeared around ten million years after Carnufex carolinensis roamed the Earth.  The last of the large-bodied rauisuchians became extinct at the end of the Triassic.

A Famous Early Crocodile – Postosuchus

Scale drawing of Postosuchus.

Picture credit: Everything Dinosaur

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