Ichthyovenator

Ichthyovenator was a meat-eating theropod dinosaur. It was from the Early Cretaceous, about 113 to 125 million years ago. Its fossils were found in Laos in 2010.^[1] Ichthyovenator was a spinosaurid, they were crocodile-like dinosaurs that ate fish.^[2]

Ichthyovenator Temporal range: Early Cretaceous, Aptian PreꞒ Ꞓ O S D C P T J K Pg N
Casts of the type vertebrae in side view
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Family:	†Spinosauridae
Subfamily:	†Spinosaurinae
Genus:	†Ichthyovenator Allain et al., 2012
Type species
†Ichthyovenator laosensis Allain et al., 2012

It is one of three spinosaurids found in Asia, the other two are Siamosaurus, and "Sinopliosaurus" fusuiensis.^[1][3][4]

Discovery and naming

Some of the known bones of Ichthyovenator, the holotype specimen is in white and undescribed fossils are in red

The first parts of the skeleton were found in 2010. They include: One rib, part of the animal's backbones (or vertebra), and most hip bones. They did not find the skull.

The only known species is Ichthyovenator laosensis. It was named and described by Ronan Allain and his colleagues in 2012. It was found in the Grès supérieurs Formation.

The name Ichthyovenator comes from the Greek word for "fish" and the Latin word for "hunter", The name refers to the fact that it ate fish. The species name is laosensis, because it lived in what is now Laos.^[1]

While Ichthyovenator was being described, paleontologists were still digging up more of its bones.^[1]

Ronan Allain was one of Ichthyovenator's original describers. In 2014, he mentioned that more of Icthyovenator's skeleton was dug up in 2012. He wrote this in the Journal of Vertebrate Paleontology. These new bones include: several teeth, a hip bone, most neck bones, and a few back and tail bones. The description of the new bones has not been officially published.^[5]

In 2015, some of Ichthyovenator's bones were compared to the ones of Sigilmassasaurus. Sigilmassasaurus is another spinosaurid.^[6]

Description

Size of Ichthyovenator (in turquoise, first from right) and other spinosaurids compared to a human

Paleontologists estimate Ichthyovenator was about 8.5 metres (28 feet) long. That's about as big as Baryonyx, one of its close relatives.

It had a half-meter sail or hump on its back, similar to Suchomimus, or Spinosaurus.^[7] Ichthyovenator's sail was unusual because it was split in two at the hips. Scientists don't know why it was like that.^[1]

Classification

Speculative life restoration of Ichthyovenator laosensis, the head and limbs are based on relatives

Ichthyovenator was first classified as a spinosaurid, inside the subfamily baryonychinae. This is the same subfamily that includes Baryonyx and Suchomimus.^[1]

In 2014 it was found that Ichthyovenator was part of the subfamily spinosaurinae instead. This was because of specific features on its teeth, and because its backbones look much like the ones of Sigilmassasaurus.^[5][8]

Some sources say Ichthyovenator might not have been a spinosaurid. They say it may have been a sail-backed carcharodontosaurid, and that it was related to Concavenator. But this hypothesis has not been published in an academic place.^[9]

The diagram below is called a cladogram. It shows how Ichthyovenator is related to other dinosaurs in its family tree. This cladogram is by Allain et al. (2012):^[1]

Spinosauroidea	Megalosauria Torvosaurus Eustreptospondylus Dubreuillosaurus Afrovenator Spinosauridae Irritator Spinosaurus Ichthyovenator Suchomimus Baryonyx