Re: Ichthyovenator, new spinosaurid from Early Cretaceous of Laos

[Mickey Mortimer <mickey_mortimer111@msn.com>]

This paper has some troubling aspects, though the neural spines are surprising 
and it's great to get a description of complete spinosaurid pubes and ischia.

First, Ichthyovenator is NOT the first definitive Asian spinosaurid.  We have 
Hone et al.'s (2010) baryonychine tooth from the Majiacun Formation of China, 
many teeth of Siamosaurus suteethorni from Thailand, teeth and a partial 
skeleton of Siamosaurus sp. from later sediments in Thailand (Buffetaut et al., 
2004), teeth of "Sinopliosaurus" fusuiensis from China, a Siamosaurus-like 
tooth from Japan (Hasegawa et al., 2003), and a spinosaurine tooth from the 
Mangchuan Formation China (Lu et al., 2009).  Even if you discount teeth, the 
partial skeleton was announced eight years ago.

Second, Chilantaisaurus was found to be a spinosaurid in their analysis, but it 
didn't include any of Benson et al.'s (2010) neovenatorid characters, so they 
didn't even test that hypothesis.  As for the Morrison manual ungual being 
spinosaurid, it's a Torvosaurus paratype.  Now it's true we don't know it 
belonged to Torvosaurus since it was found isolated, but surely it's more 
likely that Torvosaurus had a similar ungual to its relatives than spinosaurids 
being overlooked in the Morrison.

 Mickey Mortimer

> ----------------------------------------
> > Date: Sun, 22 Apr 2012 15:24:14 -0700
> > From: bcreisler@gmail.com
> > To: dinosaur@usc.edu
> > Subject: Ichthyovenator, new spinosaurid from Early Cretaceous of Laos
> >
> > From: Ben Creisler
> > bcreisler@gmail.com
> >
> > A new online paper:
> >
> > Ronan Allain, Tiengkham Xaisanavong, Philippe Richir and Bounsou
> > Khentavong (2012)
> > The first definitive Asian spinosaurid (Dinosauria: Theropoda) from
> > the Early Cretaceous of Laos.
> > Naturwissenschaften (advance online publication)
> > 2012, DOI: 10.1007/s00114-012-0911-7
> > http://www.springerlink.com/content/r5x213648388tt23/
> >
> >
> > Spinosaurids are among the largest and most specialized carnivorous
> > dinosaurs. The morphology of their crocodile-like skull, stomach
> > contents, and oxygen isotopic composition of the bones suggest they
> > had a predominantly piscivorous diet. Even if close relationships
> > between spinosaurids and Middle Jurassic megalosaurs seem well
> > established, very little is known about the transition from a
> > generalized large basal tetanuran to the specialized morphology of
> > spinosaurids. Spinosaurid remains were previously known from the Early
> > to Late Cretaceous of North Africa, Europe, and South America. Here,
> > we report the discovery of a new spinosaurid theropod from the late
> > Early Cretaceous Savannakhet Basin in Laos, which is distinguished by
> > an autapomorphic sinusoidal dorsosacral sail. This new taxon,
> > Ichthyovenator laosensis gen. et sp. nov., includes well-preserved and
> > partially articulated postcranial remains. Although possible
> > spinosaurid teeth have been reported from various Early Cretaceous
> > localities in Asia, the new taxon I. laosensis is the first definite
> > record of Spinosauridae from Asia. Cladistic analysis identifies
> > Ichthyovenator as a member of the sub-clade Baryonychinae and suggests
> > a widespread distribution of this clade at the end of the Early
> > Cretaceous. Chilantaisaurus tashouikensis from the Cretaceous of Inner
> > Mongolia, and an ungual phalanx from the Upper Jurassic of Colorado
> > are also referred to spinosaurids, extending both the stratigraphical
> > and geographical range of this clade.
>