A new review paper on Spinosaurs

[Dyscrasia]

A review paper on these enigmatic beasts by David Hone and Thomas Holtz has been recently published.

http://onlinelibrary.wiley.com/doi/10.1111/1755-6724.13328/full

A Century of Spinosaurs - A Review and Revision of the Spinosauridae with Comments on Their Ecology
Acta Geologica Sinica
June 2017


You can read the full paper here:
http://www.davehone.co.uk/wp-content/uploads/2014/01/Hone-Holtz-2017-Spinosaurs.pdf

[Halichoeres]

Thanks for posting!

[ZoPteryx]

Very interesting read!    There's still much to investigate on spinosaurs it seems.

[Sim]

Yes, the paper contained a lot of interesting information.  Something I found especially interesting was the following from the paper:

The idea that spinosaurs were fully adapted to an aquatic lifestyle to an extent similar to crocodilians, hippopotamus, otters, etc. is limited.  Evidence suggests spinosaurs were able to better exploit food sources in the water compared to other theropods, and were able to better exploit food sources on land compared to crocodiles.  One of the reasons the paper gives in support for this is that isotopic analysis shows:

- Some spinosaur teeth retain a signature close to that of semi-aquatic crocodilians and chelonians, suggesting extended periods in water.

- Some teeth referred to Spinosaurus give results that are like other terrestrial theropods and less like semi-aquatic animals.

I was very surprised by the latter, as it contrasts with the idea that Spinosaurus was confined to bodies of water.  After reading the paper, I get the impression Spinosaurus was well-adapted to acquire food in the water, but it was also capable to walk around well enough on land even with relatively short legs.

The paper also says: As with other theropods, there is no reason to a priori assume the forelimb of a spinosaur could pronate and the animals could walk on their palms.  Assessment of the recent suggestion by Ibrahim et al. that Spinosaurus may have been adept quadrupedally is obstructed by the lack of known forelimb material for Spinosaurus.

[Newt]

Keep in mind also that teeth "referred to Spinosaurus" may not in fact be Spinosaurus, if all North African spinosaurids are not actually the same species. The review suggests S. moroccanus and Sigilmassaurus may be distinct from S. aegyptiacus. Which teeth go with which taxon is hard to say with current data. It's very possible that both more-aquatic and less-aquatic spinosaurids occurred in this region. Or that there were ecological differences among regional populations within a species - who knows?

It's certainly an interesting and informative review...but it could have used some better proofreading. Journalese is hard enough to read without typos and other errors.

[stargatedalek]

It's also worth taking into account Ibrahim et al. have said they're waiting on publishing more information about why they think Spinosaurus was a floating surface based hunter which would explain the teeth.

[Sim]

It's also worth taking into account Ibrahim et al. have said they're waiting on publishing more information about why they think Spinosaurus was a floating surface based hunter which would explain the teeth.

How would Spinosaurus being a floating surface based hunter explain the teeth giving results like terrestrial theropods?  There's also this from the Spinosaurus Wikipedia page which explains that some Spinosaurus teeth gave results closer to turtles and crocodilians than other theropods, leading the authors of the analysis to suggest Spinosaurus switched between terrestrial and aquatic habitats:

A 2010 isotope analysis by Romain Amiot and colleagues found that oxygen isotope ratios of spinosaurid teeth, including teeth of Spinosaurus, indicate semiaquatic lifestyles.[45] Isotope ratios from tooth enamel and from other parts of Spinosaurus (found in Morocco and Tunisia) and of other predators from the same area such as Carcharodontosaurus were compared with isotopic compositions from contemporaneous theropods, turtles, and crocodilians.[45] The study found that Spinosaurus teeth from five of six sampled localities had oxygen isotope ratios closer to those of turtles and crocodilians when compared with other theropod teeth from the same localities.[45] The authors postulated that Spinosaurus switched between terrestrial and aquatic habitats to compete for food with large crocodilians and other large theropods respectively.[45]

Keep in mind also that teeth "referred to Spinosaurus" may not in fact be Spinosaurus, if all North African spinosaurids are not actually the same species. The review suggests S. moroccanus and Sigilmassaurus may be distinct from S. aegyptiacus. Which teeth go with which taxon is hard to say with current data. It's very possible that both more-aquatic and less-aquatic spinosaurids occurred in this region. Or that there were ecological differences among regional populations within a species - who knows?

Ibrahim et al.'s 2014 paper suggested the remains all belonged to Spinosaurus aegyptiacus.  I know of three Spinosaurus-related papers that have been published since then, Evers et al. (2015), Hendrickx et al. (2016), and this new 2017 paper by David Hone and Thomas Holtz.  All three of these find support for two Cenomanian North African spinosaurids, Spinosaurus aegyptiacus and Sigilmassasaurus brevicollis, which I agree with.  Interestingly, it appears there are actually two small-legged specimens, the one described by Ibrahim et al. in 2014, and Stromer's "Spinosaurus B" from 1934.  From what I've seen, it seems there is growing agreement these two specimens appear to represent two different species, with the one described in 2014 being Spinosaurus aegyptiacus, and "Spinosaurus B" being Sigilmassasaurus.  "Spinosaurus maroccanus" is thought to be the same animal as Sigilmassasaurus brevicollis.

So if there was both a more-aquatic and less-aquatic spinosaurid species in the area, both appear to have been small-legged...  This is illustrated in this set of Spinosaurus and Sigilmassasaurus skeletals: http://getawaytrike.deviantart.com/art/Cenomanian-North-African-spinosaurs-599210201

In the skeletals linked to above, I was struck by the size difference between the smaller Spinosaurus specimens and the larger one.  I also noticed the neural spines appear to be proportionally thinner in the smallest Spinosaurus specimen when compared to the specimen a little larger than it.  This all makes me wonder if and how proportions could've changed as Spinosaurus grew.  It seems the more work is done relating to these animals, the more it becomes apparent how mysterious they are.

It's certainly an interesting and informative review...but it could have used some better proofreading. Journalese is hard enough to read without typos and other errors.

I agree!

[Libraraptor]

An interesting read!