Scientists reconstruct skull of huge ancient crocodile-like predator

Crassigyrinus scoticus was a massive aquatic predator that hunted swamps during the Carboniferous period. 
Mrigakshi Dixit
The process of fossilization has caused specimens of Crassigyrinus to become compressed.
The process of fossilization has caused specimens of Crassigyrinus to become compressed.

The Trustees of the Natural History Museum, London  

The ancient world was a strange place to be, with a plethora of strange creatures ruling the planet from sky to sea. 

Scientists have now digitally recreated the skull of a strange, crocodile-like creature that lived around 300 million years ago.

Crassigyrinus scoticus was a massive aquatic predator that hunted swamps during the Carboniferous period. 

The reconstruction of the skull

Crassigyrinus thrived on coal swamps millions of years ago in parts of Scotland and North America, where it has been discovered preserved. Because the fossils were discovered preserved in fine-grained rock, the specimens were broken and deformed.

Experts have been studying this species for a long time, but it wasn't until recently that they were able to put together the broken fossil pieces to digitally reconstruct its skull. 

This reconstruction is scientifically significant because most known fossils of this Carboniferous carnivore have been recovered in crushed form, making it difficult to understand the traits of this species. 

The UCL team, led by Dr. Laura Porro, used CT scanning and 3D visualization techniques for this digital reconstruction. Furthermore, the team scanned four Crassigyrinus specimens, including three from the Natural History Museum. The team was able to reconstruct the tetrapod's skull by studying the skull bones of other fossils.

Crassigyrinus was a tetrapod, a four-limbed animal that is thought to be the first animal to transition from water to land.

Understanding other traits

The final reconstruction revealed a shallow skull, implying that the creature had short limbs and a flat body. It would have been two to three meters long, which was quite large for the time. 

It showed that the creature had a skull shaped like a modern crocodile and large teeth with powerful jaws to catch prey. The creature had large eyes and would have had excellent sensory abilities. 

Surprisingly, they also discovered a strange gap near the snout. “A lot of early tetrapods have midline gaps at the front of their snout, but the gap in Crassigyrinus is much larger and features smoothly sculpted edges. The nostrils were elsewhere, so there has been a lot of speculation about what this opening might have been,” explained Laura in an official statement.

The authors speculate that the mysterious gap could indicate that the creature had additional senses. One theory suggests they had a rostral organ at this gap, which is commonly found in some fish and aids in the detection of electric fields. Another theory is that Cassigyrinus had a Jacobson's organ, similar to the one found in snakes, to sniff out chemicals.

However, due to the lack of fossils, the researchers are unsure. 

“Unfortunately, we can't be sure what was in this gap because there's nothing preserved there, and nothing alive today is closely related enough to Crassigyrinus to definitely know. What is clear is that these animals had very well-developed senses, so it stands to reason that it might have had another sensory organ at the front of its snout,” said Laura. 

The findings have been reported in the Journal of Vertebrate Palaeontology.

Study abstract:

The early tetrapod Crassigyrinus scoticus was a large aquatic predator known from the lower- to mid-Carboniferous (upper Tournasian to upper Visean/lower Serpukovian, approximately 350–330 Ma) of Scotland and Canada. Crassigyrinus is enigmatic in terms of its phylogenetic position due to its unusual morphology, which features a mixture of primitive and derived characters. Previous reconstructions, based on five incomplete and deformed specimens, have suggested a dorsoventrally tall skull with a short and broad snout, large orbits and external nares, and an extended postorbital region. In this study, we scanned four specimens using computed tomography and segmented imaging data to separate bone from matrix and individual bones from each other. Based on these data, we present a revised description of the upper and lower jaws, including sutural morphology and abundant new anatomical information. Damage was repaired and the skull retrodeformed to create a hypothetical three-dimensional reconstruction of the skull of Crassigyrinus that is dorsoventrally flatter than earlier reconstructions, yet still morphologically unique amongst early tetrapods. Overall skull shape, the size and distribution of the teeth, sutural morphology, and the specialized anatomy of the jaw joint and mandibular symphysis all suggest that Crassigyrinus was a powerful aquatic predator capable of hunting and subduing large prey.

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