Kem Kem Group spinosaurines

Credit: Cisiopurple on DeviantArt.

The Kem Kem Group spinosaurine(s) is an unnamed genus of spinosaurid dinosaur that lived in Morocco during the Early Cretaceous.

## Description

Spines from an indeterminate Spinosauridae have been recovered from the Kem Kem beds. They are not yet described and do not match any spines discovered near them. This morphotype may comprise multiple taxa.

## Paleobiology

Remains of a Kem Kem spinosaurine dorsal vertebrae have been found with strange holes and markings bore into them. These are theorized to have been insect burrows in the centrum, made by insects long after death.

### Locomotion

    The exact habitat of the Kem Kem spinosaur remains unclear. Several researchers that have studied members of Spinosauridae, however the results often contradict one another. Kem Kem Group spinosaur is suspected to be semi-aquatic, spending most of its life in the water. The environment of Kem Kem Group spinosaur has been supported by the studies that claimed the genus' habitats were rivers with highly specialized features that has been redesigned in 2014 . With the recent discovery finding an highly elongated and flat tail, that might have helped animal swim actively against currents . The studies of the tail vertebrae and chevrons of Kem Kem Group spinosaur go against Henderson's initial theory that Kem Kem Group spinosaur mainly inhabited riverbanks and in shallow water, but was too buoyant to submerge into deep water. Studies of its tail, a specimen recovered and analyzed by paleontologists Ibrahim, Pierce, Lauder, and Sereno in 2018 propose that Kem Kem Group spinosaur had a tail that was well adapted to propelling the animal through water. However, there are a number of counter thesis against the tail's depiction as a propeller in the water as well . The elongated neural spines, which run to the end of the tail on both dorsal and ventral sides, indicate that Kem Kem Group spinosaur was able to move in a similar manner to modern crocodilians, swinging its tail from side-to-side. Through further experimentation by Lauder and Pierce (using a plastic model in water), the tail of Kem Kem Group spinosaur was found to have eight times as much forward thrust as the tails of other theropods like *Coelophysis* and *Allosaurus*. Kem Kem Group spinosaur was two times as efficient at achieving forward thrust than others like it. This discovery indicates that Kem Kem Group spinosaur may have led a lifestyle comparable to modern alligators and crocodiles, and that this animal might have capable of remaining in water for long periods of time while hunting fish and small animals.

On the other hand, that there are also several research about this animal, refutes the semi aquatic claims, for example: A 2018 study, led by paleobiologist Donald Henderson, the research studying the buoyancy in lungs of crocodilians and comparing it to the lung placement in Kem Kem Group spinosaur fossils. It was discovered that Kem Kem Group spinosaur could not sink or dive below the water surface. It was able to keep its entire head above the water surface while floating, much like other theropods. The study also found that Kem Kem Group spinosaur had to paddle its hind legs to prevent itself from tipping over onto its side, something that living semi-aquatic animals do not need to do. The studies conducted on Kem Kem Group spinosaur suggests that it probably did not hunt completely submerged in water as previously theorized, but would have spent majority of its life on land or around water . This research also correlates with an earlier research done by Romain Amiot and colleagues in 2010, they look to the oxygen isotope ratios of spinosaurid fossils, by comparing Isotope ratios from teeth of *Baryonyx*, *Irritator*, *Siamosaurus* and Kem Kem Group spinosaur were compared with isotopic compositions from theropods, turtles, and crocodilians. The study found that spinosaurid isotope ratios were closer to those of aquatic reptiles. However, the *Siamosaurus* specimens tended to have the largest difference from the results of the other species discovered. Kem Kem Group spinosaur had the least difference, strongly suggesting that the different species of Spinosaurids have had different preferences for their environments. Some specimens show similar isotope ratios to other theropods . The debate whether that the Kem Kem Group spinosaur was entirely aquatic, terrestrial or amphibious, switched between both habitats, will continue to be a matter of debate. However, research published by Thomas R. Holtz Jr. and Dave Hone in 2021 suggests paleontologists have little evidence for a fully aquatic Kem Kem Group spinosaur model. Based on the nares and orbits not so dorsally positioned, spread toes ideal for wading, a long neck and increased ventriflexion capacity suited to vertical lunging and slender neural spines lacking rugose musculature anchor points, they conclude Kem Kem Group spinosaur was likely a waterside generalist. They include the fact that the tail may not have been suited for propulsion and it may have been unstable in the water. Holtz and Hone cite drag, instability and low swimming efficiency as reasons for Kem Kem Group spinosaur acting like a massive generalist pelican, shoebill, giant petrels or skua rather than a proto-whale, or semi-aquatic to aquatic species of crocodilian . However, some paleontologists doubt that Kem Kem Group spinosaur was exclusively wading predator, with Luis Rey stating that the dinosaur was likely more like a "seal-walrus-penguin" than anything previously published . Meanwhile, other paleontologists like Donald M. Handerson, Michael Milbourne, David Hone, Scott Hartman and John Hutchinson conclude that the degree of highest aquatic attributions directly associated to Kem Kem Group spinosaur is not validated and consistent.

    Fabbri et al. (2022) used bone thickness in a wealth of theropods to determine that Kem Kem Group spinosaur had bones about as thick as modern penguins. In penguins, this specific structure is used to optimize buoyancy while diving. They entered it and other spinosaurs into a comprehensive dataset including crocodilians, ceteaceans, mosasaurs, sauropterygians (including ichthyosaurs), pinnipeds, placodontians, birds and pterosaurs but excluding *Oxalaia* and *Sigilmassasaurus* based on presumed synonymy. They found that it and possibly *Baryonyx* fall firmly into diver morphology and bear evidence of subaqueous feeding, where the latter was likely ancestral to Spinosauridae and likely secondarily lost in *Suchomimus*. The study was received well by others, although some paleontologists like, Donald M. Handerson remains skeptical about its conclusion. There is significant criticism to the original paper. Dave Hone notes that the information is not new, and that biomechanics studies examining hydrodynamics show that they were not ideal. Hone also published again, concluding that the biological assumptions given is not consistent and can be interpreted differently, They suggest earlier publications lack specimen diversity and have sampling errors, with an earlier publication also being inconsistent with their database . However, the other tram responded again and so did Hone. The debate continued in the same year with Sereno et al. arguing that it was too buoyant to dive, a slow swimmer and generally unsuitable. They also reduced the animal to 14 meters long, 2.6 tall and 7390 kilograms heavy. Additionally the research included the fossil remains that identified and confirmed to be Kem Kem Group spinosaur has been extracted from inland parts of Africa; away from any significant bodies of water; like deltas, seas or oceans. Aiding Hone's, Holtz's and Handerson's argument, a study by Myhrvold and Sereno et al. suggests that Nizar et al. cannot determine lifestyle for an entire clade through bone compactness and pDFA.

### Ontogeny

It has been proposed that juveniles exploited a semiaquatic niche, but recent publications might make this unlikely, since it was likely a generalist wader than a derivered semiaquatic piscivore. Ecological separation between adults and juveniles was likely due to size difference. Cenomanian deltas are noted to have been age-inclusive, with no geographical or environmental separation . Theoretically the situation of juvenile spinosaurines could be somewhat similar to crocodilians and monitor lizards, staying away from aggressive adults in potential nurseries, until they reached appropriate size[*citation needed*].

## Paleoecology

Prehistoric Northern Africa bore many large predators such as crocodylomorphs and theropods, often described as "the most dangerous place on Earth".

## Notable Specimens

* MSNM V4047: a very large specimen that has been recovered from the Kem Kem fossil beds, formerly, it was estimated to be 15-16 meters long, but as of 2022, it has been downsized 13.5 - 14.45 meters long. The specimen is currently held in the Milano Natural History Museum .
* NHMUK R 16421: another, potentially larger, specimen.
* NHMUK 16665: A juvenile rostrum.
* FSAC-KK-11888: a partial sub-adult skeleton.

## Gallery

**Credit: Dan Folkes.****Credit: Mark Witton.****Credit: Maija Karala on Twitter.****Credit: R.J. Palmer.**Possible top jaw recovered by Ibrahim showing alveolar arrangement, but currently resides in private hands.**Credit: SpinoInWonderland.****Credit: Scott Hartman.****Credit: Scott Hartman.****Credit: Scott Hartman.**A dorsal vertebrae centrum, with theorized insect-bored holes.NHMUK R 16421.
## References

1. ↑ https://twitter.com/TheBioBob/status/1331957228228792321
2. ↑ https://twitter.com/TheBioBob/status/1325512952246657026
3. ↑ https://www.nationalgeographic.com/science/phenomena/2014/09/11/the-new-spinosaurus/
4. ↑ https://api.nationalgeographic.com/distribution/public/amp/science/2020/04/first-spinosaurus-tail-found-confirms-dinosaur-was-swimming
5. ↑ https://api.nationalgeographic.com/distribution/public/amp/science/2020/04/spinosaurus-graphic-reconstructing-gigantic-aquatic-predator
6. ↑ https://www.nytimes.com/2020/04/29/science/spinosaurus-dinosaur-tail-swimming.html
7. ↑ https://twitter.com/markwitton/status/1255814025931296769?lang=en
8. ↑ https://twitter.com/markwitton/status/1255830578487873541?lang=en
9. ↑ https://www.instagram.com/p/B\_qP6A9qO7e/
10. ↑ https://blogs.scientificamerican.com/laelaps/spinosaurus-was-a-terrible-swimmer/
11. ↑ https://royaltyrrellmuseum.wpcomstaging.com/2018/08/16/new-research-refutes-claims-that-spinosaurus-was-semi-aquatic/
12. ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6098948/
13. ↑ https://pubs.geoscienceworld.org/gsa/geology/article-abstract/38/2/139/130188/Oxygen-isotope-evidence-for-semi-aquatic-habits?redirectedFrom=fulltext
14. ↑ https://www.oieau.org/eaudoc/eaudoc/page/Oxygen-isotope-evidence-semi-aquatic-habits-among-spinosaurid-theropods-0
15. ↑ https://www.researchgate.net/publication/222090629\_Oxygen\_isotope\_evidence\_for\_semi-aquatic\_habits\_among\_spinosaurid\_theropods
16. ↑ https://palaeo-electronica.org/content/2021/3219-the-ecology-of-spinosaurus
17. ↑ https://archosaurmusings.wordpress.com/2021/01/26/the-evidence-for-spinosaurus-being-a-specialist-aquatic-predator-and-good-swimmer-is-weak/amp/?\_\_twitter\_impression=true
18. ↑ https://www.nationalgeographic.com/science/article/did-the-river-monster-spinosaurus-hunt-like-a-stork
19. ↑ https://www.upi.com/Science\_News/2021/01/26/Giant-dinosaur-hunted-from-the-shoreline-like-a-bird-not-an-aquatic-predator/4911611633287/
20. ↑ Luis V. Rey answering a question
21. ↑ https://www.nytimes.com/2020/04/29/science/spinosaurus-dinosaur-tail-swimming.html
22. ↑ https://peerj.com/articles/5409/
23. ↑ https://blogs.scientificamerican.com/laelaps/spinosaurus-was-a-terrible-swimmer/
24. ↑ https://edition.cnn.com/2021/01/26/world/spinosaurus-behavior-study-scli-intl-scn/index.html
25. ↑ https://twitter.com/Dave\_Hone/status/1577155804523732992
26. ↑ https://www.nature.com/articles/s41586-022-04528-0
27. ↑ https://phys.org/news/2022-03-dense-bones-spinosaurus-underwater.html
28. ↑ https://www.sciencenews.org/article/spinosaurus-bones-dinosaur-swim-paleontology
29. ↑ https://twitter.com/TomHoltzPaleo/status/1506671659805290505
30. ↑ https://www.nationalgeographic.com/science/article/spinosaurus-had-penguin-like-bones-a-sign-of-hunting-underwater
31. ↑ https://www.biorxiv.org/content/10.1101/2022.04.13.487781v1
32. ↑ https://mobile.twitter.com/Dave\_Hone/status/1506663165542686728
33. ↑ https://www.youtube.com/watch?v=TkBdxRkXbYM&t=2167s
34. ↑ https://www.biorxiv.org/content/10.1101/2022.04.13.487781v1
35. ↑ https://www.biorxiv.org/content/10.1101/2022.05.05.490811v1
36. ↑ https://twitter.com/Dave\_Hone/status/1523036298541293569
37. ↑ https://twitter.com/Dave\_Hone/status/1577160214825947137
38. ↑ https://twitter.com/Dave\_Hone/status/1577161864567742464
39. ↑ https://www.biorxiv.org/content/10.1101/2022.05.25.493395v1
40. ↑ https://www.biorxiv.org/content/10.1101/2023.05.04.539484v1.full.pdf
41. ↑ https://www.sciencedirect.com/science/article/pii/S0195667118302052
42. ↑ https://medium.com/predict/scientists-reveal-the-most-dangerous-place-in-earths-history-562b88cb6681